Ignore:
Timestamp:
14/06/14 11:20:37 (7 years ago)
Author:
julian.reschke@…
Message:

update to latest version of rfc2629.xslt, regen all HTML

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1 edited

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  • draft-ietf-httpbis/03/p1-messaging.html

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    389398      <link rel="Appendix" title="D Compatibility with Previous Versions" href="#rfc.section.D">
    390399      <link rel="Appendix" title="E Change Log (to be removed by RFC Editor before publication)" href="#rfc.section.E">
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    392401      <link rel="schema.dct" href="http://purl.org/dc/terms/">
    393402      <meta name="dct.creator" content="Fielding, R.">
     
    418427            </tr>
    419428            <tr>
    420                <td class="left">Obsoletes: <a href="http://tools.ietf.org/html/rfc2616">2616</a> (if approved)
     429               <td class="left">Obsoletes: <a href="https://tools.ietf.org/html/rfc2616">2616</a> (if approved)
    421430               </td>
    422431               <td class="right">J. Gettys</td>
     
    489498      </table>
    490499      <p class="title">HTTP/1.1, part 1: URIs, Connections, and Message Parsing<br><span class="filename">draft-ietf-httpbis-p1-messaging-03</span></p>
    491       <h1><a id="rfc.status" href="#rfc.status">Status of this Memo</a></h1>
    492       <p>By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she
    493          is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section
    494          6 of BCP 79.
    495       </p>
    496       <p>Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note
    497          that other groups may also distribute working documents as Internet-Drafts.
    498       </p>
    499       <p>Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other
    500          documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as “work
    501          in progress”.
    502       </p>
    503       <p>The list of current Internet-Drafts can be accessed at <a href="http://www.ietf.org/ietf/1id-abstracts.txt">http://www.ietf.org/ietf/1id-abstracts.txt</a>.
    504       </p>
    505       <p>The list of Internet-Draft Shadow Directories can be accessed at <a href="http://www.ietf.org/shadow.html">http://www.ietf.org/shadow.html</a>.
    506       </p>
    507       <p>This Internet-Draft will expire on December 19, 2008.</p>
    508       <h1 id="rfc.abstract"><a href="#rfc.abstract">Abstract</a></h1>
     500      <div id="rfc.status">
     501         <h1><a href="#rfc.status">Status of this Memo</a></h1>
     502         <p>By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she
     503            is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section
     504            6 of BCP 79.
     505         </p>
     506         <p>Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note
     507            that other groups may also distribute working documents as Internet-Drafts.
     508         </p>
     509         <p>Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other
     510            documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as “work
     511            in progress”.
     512         </p>
     513         <p>The list of current Internet-Drafts can be accessed at <a href="http://www.ietf.org/ietf/1id-abstracts.txt">http://www.ietf.org/ietf/1id-abstracts.txt</a>.
     514         </p>
     515         <p>The list of Internet-Draft Shadow Directories can be accessed at <a href="http://www.ietf.org/shadow.html">http://www.ietf.org/shadow.html</a>.
     516         </p>
     517         <p>This Internet-Draft will expire on December 19, 2008.</p>
     518      </div>
     519      <h1 id="rfc.abstract"><a href="#rfc.abstract">Abstract</a></h1>
    509520      <p>The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypermedia information
    510521         systems. HTTP has been in use by the World Wide Web global information initiative since 1990. This document is Part 1 of the
     
    513524         (URI) schemes, defines the generic message syntax and parsing requirements for HTTP message frames, and describes general
    514525         security concerns for implementations.
    515       </p> 
    516       <h1 id="rfc.note.1"><a href="#rfc.note.1">Editorial Note (To be removed by RFC Editor)</a></h1> 
     526      </p>
     527      <h1 id="rfc.note.1"><a href="#rfc.note.1">Editorial Note (To be removed by RFC Editor)</a></h1>
    517528      <p>Discussion of this draft should take place on the HTTPBIS working group mailing list (ietf-http-wg@w3.org). The current issues
    518529         list is at &lt;<a href="http://www.tools.ietf.org/wg/httpbis/trac/report/11">http://www.tools.ietf.org/wg/httpbis/trac/report/11</a>&gt; and related documents (including fancy diffs) can be found at &lt;<a href="http://www.tools.ietf.org/wg/httpbis/">http://www.tools.ietf.org/wg/httpbis/</a>&gt;.
    519       </p> 
     530      </p>
    520531      <p>The changes in this draft are summarized in <a href="#changes.since.02" title="Since draft-ietf-httpbis-p1-messaging-02">Appendix&nbsp;E.4</a>.
    521       </p> 
     532      </p>
    522533      <hr class="noprint">
    523534      <h1 class="np" id="rfc.toc"><a href="#rfc.toc">Table of Contents</a></h1>
    524535      <ul class="toc">
    525          <li>1.&nbsp;&nbsp;&nbsp;<a href="#introduction">Introduction</a><ul>
    526                <li>1.1&nbsp;&nbsp;&nbsp;<a href="#intro.purpose">Purpose</a></li>
    527                <li>1.2&nbsp;&nbsp;&nbsp;<a href="#intro.requirements">Requirements</a></li>
    528                <li>1.3&nbsp;&nbsp;&nbsp;<a href="#intro.terminology">Terminology</a></li>
    529                <li>1.4&nbsp;&nbsp;&nbsp;<a href="#intro.overall.operation">Overall Operation</a></li>
     536         <li><a href="#rfc.section.1">1.</a>&nbsp;&nbsp;&nbsp;<a href="#introduction">Introduction</a><ul>
     537               <li><a href="#rfc.section.1.1">1.1</a>&nbsp;&nbsp;&nbsp;<a href="#intro.purpose">Purpose</a></li>
     538               <li><a href="#rfc.section.1.2">1.2</a>&nbsp;&nbsp;&nbsp;<a href="#intro.requirements">Requirements</a></li>
     539               <li><a href="#rfc.section.1.3">1.3</a>&nbsp;&nbsp;&nbsp;<a href="#intro.terminology">Terminology</a></li>
     540               <li><a href="#rfc.section.1.4">1.4</a>&nbsp;&nbsp;&nbsp;<a href="#intro.overall.operation">Overall Operation</a></li>
    530541            </ul>
    531542         </li>
    532          <li>2.&nbsp;&nbsp;&nbsp;<a href="#notation">Notational Conventions and Generic Grammar</a><ul>
    533                <li>2.1&nbsp;&nbsp;&nbsp;<a href="#notation.abnf">Augmented BNF</a></li>
    534                <li>2.2&nbsp;&nbsp;&nbsp;<a href="#basic.rules">Basic Rules</a></li>
    535                <li>2.3&nbsp;&nbsp;&nbsp;<a href="#abnf.dependencies">ABNF Rules defined in other Parts of the Specification</a></li>
     543         <li><a href="#rfc.section.2">2.</a>&nbsp;&nbsp;&nbsp;<a href="#notation">Notational Conventions and Generic Grammar</a><ul>
     544               <li><a href="#rfc.section.2.1">2.1</a>&nbsp;&nbsp;&nbsp;<a href="#notation.abnf">Augmented BNF</a></li>
     545               <li><a href="#rfc.section.2.2">2.2</a>&nbsp;&nbsp;&nbsp;<a href="#basic.rules">Basic Rules</a></li>
     546               <li><a href="#rfc.section.2.3">2.3</a>&nbsp;&nbsp;&nbsp;<a href="#abnf.dependencies">ABNF Rules defined in other Parts of the Specification</a></li>
    536547            </ul>
    537548         </li>
    538          <li>3.&nbsp;&nbsp;&nbsp;<a href="#protocol.parameters">Protocol Parameters</a><ul>
    539                <li>3.1&nbsp;&nbsp;&nbsp;<a href="#http.version">HTTP Version</a></li>
    540                <li>3.2&nbsp;&nbsp;&nbsp;<a href="#uri">Uniform Resource Identifiers</a><ul>
    541                      <li>3.2.1&nbsp;&nbsp;&nbsp;<a href="#general.syntax">General Syntax</a></li>
    542                      <li>3.2.2&nbsp;&nbsp;&nbsp;<a href="#http.url">http URL</a></li>
    543                      <li>3.2.3&nbsp;&nbsp;&nbsp;<a href="#uri.comparison">URI Comparison</a></li>
     549         <li><a href="#rfc.section.3">3.</a>&nbsp;&nbsp;&nbsp;<a href="#protocol.parameters">Protocol Parameters</a><ul>
     550               <li><a href="#rfc.section.3.1">3.1</a>&nbsp;&nbsp;&nbsp;<a href="#http.version">HTTP Version</a></li>
     551               <li><a href="#rfc.section.3.2">3.2</a>&nbsp;&nbsp;&nbsp;<a href="#uri">Uniform Resource Identifiers</a><ul>
     552                     <li><a href="#rfc.section.3.2.1">3.2.1</a>&nbsp;&nbsp;&nbsp;<a href="#general.syntax">General Syntax</a></li>
     553                     <li><a href="#rfc.section.3.2.2">3.2.2</a>&nbsp;&nbsp;&nbsp;<a href="#http.url">http URL</a></li>
     554                     <li><a href="#rfc.section.3.2.3">3.2.3</a>&nbsp;&nbsp;&nbsp;<a href="#uri.comparison">URI Comparison</a></li>
    544555                  </ul>
    545556               </li>
    546                <li>3.3&nbsp;&nbsp;&nbsp;<a href="#date.time.formats">Date/Time Formats</a><ul>
    547                      <li>3.3.1&nbsp;&nbsp;&nbsp;<a href="#full.date">Full Date</a></li>
     557               <li><a href="#rfc.section.3.3">3.3</a>&nbsp;&nbsp;&nbsp;<a href="#date.time.formats">Date/Time Formats</a><ul>
     558                     <li><a href="#rfc.section.3.3.1">3.3.1</a>&nbsp;&nbsp;&nbsp;<a href="#full.date">Full Date</a></li>
    548559                  </ul>
    549560               </li>
    550                <li>3.4&nbsp;&nbsp;&nbsp;<a href="#transfer.codings">Transfer Codings</a><ul>
    551                      <li>3.4.1&nbsp;&nbsp;&nbsp;<a href="#chunked.transfer.encoding">Chunked Transfer Coding</a></li>
     561               <li><a href="#rfc.section.3.4">3.4</a>&nbsp;&nbsp;&nbsp;<a href="#transfer.codings">Transfer Codings</a><ul>
     562                     <li><a href="#rfc.section.3.4.1">3.4.1</a>&nbsp;&nbsp;&nbsp;<a href="#chunked.transfer.encoding">Chunked Transfer Coding</a></li>
    552563                  </ul>
    553564               </li>
    554                <li>3.5&nbsp;&nbsp;&nbsp;<a href="#product.tokens">Product Tokens</a></li>
     565               <li><a href="#rfc.section.3.5">3.5</a>&nbsp;&nbsp;&nbsp;<a href="#product.tokens">Product Tokens</a></li>
    555566            </ul>
    556567         </li>
    557          <li>4.&nbsp;&nbsp;&nbsp;<a href="#http.message">HTTP Message</a><ul>
    558                <li>4.1&nbsp;&nbsp;&nbsp;<a href="#message.types">Message Types</a></li>
    559                <li>4.2&nbsp;&nbsp;&nbsp;<a href="#message.headers">Message Headers</a></li>
    560                <li>4.3&nbsp;&nbsp;&nbsp;<a href="#message.body">Message Body</a></li>
    561                <li>4.4&nbsp;&nbsp;&nbsp;<a href="#message.length">Message Length</a></li>
    562                <li>4.5&nbsp;&nbsp;&nbsp;<a href="#general.header.fields">General Header Fields</a></li>
     568         <li><a href="#rfc.section.4">4.</a>&nbsp;&nbsp;&nbsp;<a href="#http.message">HTTP Message</a><ul>
     569               <li><a href="#rfc.section.4.1">4.1</a>&nbsp;&nbsp;&nbsp;<a href="#message.types">Message Types</a></li>
     570               <li><a href="#rfc.section.4.2">4.2</a>&nbsp;&nbsp;&nbsp;<a href="#message.headers">Message Headers</a></li>
     571               <li><a href="#rfc.section.4.3">4.3</a>&nbsp;&nbsp;&nbsp;<a href="#message.body">Message Body</a></li>
     572               <li><a href="#rfc.section.4.4">4.4</a>&nbsp;&nbsp;&nbsp;<a href="#message.length">Message Length</a></li>
     573               <li><a href="#rfc.section.4.5">4.5</a>&nbsp;&nbsp;&nbsp;<a href="#general.header.fields">General Header Fields</a></li>
    563574            </ul>
    564575         </li>
    565          <li>5.&nbsp;&nbsp;&nbsp;<a href="#request">Request</a><ul>
    566                <li>5.1&nbsp;&nbsp;&nbsp;<a href="#request-line">Request-Line</a><ul>
    567                      <li>5.1.1&nbsp;&nbsp;&nbsp;<a href="#method">Method</a></li>
    568                      <li>5.1.2&nbsp;&nbsp;&nbsp;<a href="#request-uri">Request-URI</a></li>
     576         <li><a href="#rfc.section.5">5.</a>&nbsp;&nbsp;&nbsp;<a href="#request">Request</a><ul>
     577               <li><a href="#rfc.section.5.1">5.1</a>&nbsp;&nbsp;&nbsp;<a href="#request-line">Request-Line</a><ul>
     578                     <li><a href="#rfc.section.5.1.1">5.1.1</a>&nbsp;&nbsp;&nbsp;<a href="#method">Method</a></li>
     579                     <li><a href="#rfc.section.5.1.2">5.1.2</a>&nbsp;&nbsp;&nbsp;<a href="#request-uri">Request-URI</a></li>
    569580                  </ul>
    570581               </li>
    571                <li>5.2&nbsp;&nbsp;&nbsp;<a href="#the.resource.identified.by.a.request">The Resource Identified by a Request</a></li>
     582               <li><a href="#rfc.section.5.2">5.2</a>&nbsp;&nbsp;&nbsp;<a href="#the.resource.identified.by.a.request">The Resource Identified by a Request</a></li>
    572583            </ul>
    573584         </li>
    574          <li>6.&nbsp;&nbsp;&nbsp;<a href="#response">Response</a><ul>
    575                <li>6.1&nbsp;&nbsp;&nbsp;<a href="#status-line">Status-Line</a><ul>
    576                      <li>6.1.1&nbsp;&nbsp;&nbsp;<a href="#status.code.and.reason.phrase">Status Code and Reason Phrase</a></li>
     585         <li><a href="#rfc.section.6">6.</a>&nbsp;&nbsp;&nbsp;<a href="#response">Response</a><ul>
     586               <li><a href="#rfc.section.6.1">6.1</a>&nbsp;&nbsp;&nbsp;<a href="#status-line">Status-Line</a><ul>
     587                     <li><a href="#rfc.section.6.1.1">6.1.1</a>&nbsp;&nbsp;&nbsp;<a href="#status.code.and.reason.phrase">Status Code and Reason Phrase</a></li>
    577588                  </ul>
    578589               </li>
    579590            </ul>
    580591         </li>
    581          <li>7.&nbsp;&nbsp;&nbsp;<a href="#connections">Connections</a><ul>
    582                <li>7.1&nbsp;&nbsp;&nbsp;<a href="#persistent.connections">Persistent Connections</a><ul>
    583                      <li>7.1.1&nbsp;&nbsp;&nbsp;<a href="#persistent.purpose">Purpose</a></li>
    584                      <li>7.1.2&nbsp;&nbsp;&nbsp;<a href="#persistent.overall">Overall Operation</a><ul>
    585                            <li>7.1.2.1&nbsp;&nbsp;&nbsp;<a href="#persistent.negotiation">Negotiation</a></li>
    586                            <li>7.1.2.2&nbsp;&nbsp;&nbsp;<a href="#pipelining">Pipelining</a></li>
    587                         </ul>
    588                      </li>
    589                      <li>7.1.3&nbsp;&nbsp;&nbsp;<a href="#persistent.proxy">Proxy Servers</a></li>
    590                      <li>7.1.4&nbsp;&nbsp;&nbsp;<a href="#persistent.practical">Practical Considerations</a></li>
     592         <li><a href="#rfc.section.7">7.</a>&nbsp;&nbsp;&nbsp;<a href="#connections">Connections</a><ul>
     593               <li><a href="#rfc.section.7.1">7.1</a>&nbsp;&nbsp;&nbsp;<a href="#persistent.connections">Persistent Connections</a><ul>
     594                     <li><a href="#rfc.section.7.1.1">7.1.1</a>&nbsp;&nbsp;&nbsp;<a href="#persistent.purpose">Purpose</a></li>
     595                     <li><a href="#rfc.section.7.1.2">7.1.2</a>&nbsp;&nbsp;&nbsp;<a href="#persistent.overall">Overall Operation</a></li>
     596                     <li><a href="#rfc.section.7.1.3">7.1.3</a>&nbsp;&nbsp;&nbsp;<a href="#persistent.proxy">Proxy Servers</a></li>
     597                     <li><a href="#rfc.section.7.1.4">7.1.4</a>&nbsp;&nbsp;&nbsp;<a href="#persistent.practical">Practical Considerations</a></li>
    591598                  </ul>
    592599               </li>
    593                <li>7.2&nbsp;&nbsp;&nbsp;<a href="#message.transmission.requirements">Message Transmission Requirements</a><ul>
    594                      <li>7.2.1&nbsp;&nbsp;&nbsp;<a href="#persistent.flow">Persistent Connections and Flow Control</a></li>
    595                      <li>7.2.2&nbsp;&nbsp;&nbsp;<a href="#persistent.monitor">Monitoring Connections for Error Status Messages</a></li>
    596                      <li>7.2.3&nbsp;&nbsp;&nbsp;<a href="#use.of.the.100.status">Use of the 100 (Continue) Status</a></li>
    597                      <li>7.2.4&nbsp;&nbsp;&nbsp;<a href="#connection.premature">Client Behavior if Server Prematurely Closes Connection</a></li>
     600               <li><a href="#rfc.section.7.2">7.2</a>&nbsp;&nbsp;&nbsp;<a href="#message.transmission.requirements">Message Transmission Requirements</a><ul>
     601                     <li><a href="#rfc.section.7.2.1">7.2.1</a>&nbsp;&nbsp;&nbsp;<a href="#persistent.flow">Persistent Connections and Flow Control</a></li>
     602                     <li><a href="#rfc.section.7.2.2">7.2.2</a>&nbsp;&nbsp;&nbsp;<a href="#persistent.monitor">Monitoring Connections for Error Status Messages</a></li>
     603                     <li><a href="#rfc.section.7.2.3">7.2.3</a>&nbsp;&nbsp;&nbsp;<a href="#use.of.the.100.status">Use of the 100 (Continue) Status</a></li>
     604                     <li><a href="#rfc.section.7.2.4">7.2.4</a>&nbsp;&nbsp;&nbsp;<a href="#connection.premature">Client Behavior if Server Prematurely Closes Connection</a></li>
    598605                  </ul>
    599606               </li>
    600607            </ul>
    601608         </li>
    602          <li>8.&nbsp;&nbsp;&nbsp;<a href="#header.fields">Header Field Definitions</a><ul>
    603                <li>8.1&nbsp;&nbsp;&nbsp;<a href="#header.connection">Connection</a></li>
    604                <li>8.2&nbsp;&nbsp;&nbsp;<a href="#header.content-length">Content-Length</a></li>
    605                <li>8.3&nbsp;&nbsp;&nbsp;<a href="#header.date">Date</a><ul>
    606                      <li>8.3.1&nbsp;&nbsp;&nbsp;<a href="#clockless.origin.server.operation">Clockless Origin Server Operation</a></li>
     609         <li><a href="#rfc.section.8">8.</a>&nbsp;&nbsp;&nbsp;<a href="#header.fields">Header Field Definitions</a><ul>
     610               <li><a href="#rfc.section.8.1">8.1</a>&nbsp;&nbsp;&nbsp;<a href="#header.connection">Connection</a></li>
     611               <li><a href="#rfc.section.8.2">8.2</a>&nbsp;&nbsp;&nbsp;<a href="#header.content-length">Content-Length</a></li>
     612               <li><a href="#rfc.section.8.3">8.3</a>&nbsp;&nbsp;&nbsp;<a href="#header.date">Date</a><ul>
     613                     <li><a href="#rfc.section.8.3.1">8.3.1</a>&nbsp;&nbsp;&nbsp;<a href="#clockless.origin.server.operation">Clockless Origin Server Operation</a></li>
    607614                  </ul>
    608615               </li>
    609                <li>8.4&nbsp;&nbsp;&nbsp;<a href="#header.host">Host</a></li>
    610                <li>8.5&nbsp;&nbsp;&nbsp;<a href="#header.te">TE</a></li>
    611                <li>8.6&nbsp;&nbsp;&nbsp;<a href="#header.trailer">Trailer</a></li>
    612                <li>8.7&nbsp;&nbsp;&nbsp;<a href="#header.transfer-encoding">Transfer-Encoding</a></li>
    613                <li>8.8&nbsp;&nbsp;&nbsp;<a href="#header.upgrade">Upgrade</a></li>
    614                <li>8.9&nbsp;&nbsp;&nbsp;<a href="#header.via">Via</a></li>
     616               <li><a href="#rfc.section.8.4">8.4</a>&nbsp;&nbsp;&nbsp;<a href="#header.host">Host</a></li>
     617               <li><a href="#rfc.section.8.5">8.5</a>&nbsp;&nbsp;&nbsp;<a href="#header.te">TE</a></li>
     618               <li><a href="#rfc.section.8.6">8.6</a>&nbsp;&nbsp;&nbsp;<a href="#header.trailer">Trailer</a></li>
     619               <li><a href="#rfc.section.8.7">8.7</a>&nbsp;&nbsp;&nbsp;<a href="#header.transfer-encoding">Transfer-Encoding</a></li>
     620               <li><a href="#rfc.section.8.8">8.8</a>&nbsp;&nbsp;&nbsp;<a href="#header.upgrade">Upgrade</a></li>
     621               <li><a href="#rfc.section.8.9">8.9</a>&nbsp;&nbsp;&nbsp;<a href="#header.via">Via</a></li>
    615622            </ul>
    616623         </li>
    617          <li>9.&nbsp;&nbsp;&nbsp;<a href="#IANA.considerations">IANA Considerations</a><ul>
    618                <li>9.1&nbsp;&nbsp;&nbsp;<a href="#message.header.registration">Message Header Registration</a></li>
     624         <li><a href="#rfc.section.9">9.</a>&nbsp;&nbsp;&nbsp;<a href="#IANA.considerations">IANA Considerations</a><ul>
     625               <li><a href="#rfc.section.9.1">9.1</a>&nbsp;&nbsp;&nbsp;<a href="#message.header.registration">Message Header Registration</a></li>
    619626            </ul>
    620627         </li>
    621          <li>10.&nbsp;&nbsp;&nbsp;<a href="#security.considerations">Security Considerations</a><ul>
    622                <li>10.1&nbsp;&nbsp;&nbsp;<a href="#personal.information">Personal Information</a></li>
    623                <li>10.2&nbsp;&nbsp;&nbsp;<a href="#abuse.of.server.log.information">Abuse of Server Log Information</a></li>
    624                <li>10.3&nbsp;&nbsp;&nbsp;<a href="#attack.pathname">Attacks Based On File and Path Names</a></li>
    625                <li>10.4&nbsp;&nbsp;&nbsp;<a href="#dns.spoofing">DNS Spoofing</a></li>
    626                <li>10.5&nbsp;&nbsp;&nbsp;<a href="#attack.proxies">Proxies and Caching</a></li>
    627                <li>10.6&nbsp;&nbsp;&nbsp;<a href="#attack.DoS">Denial of Service Attacks on Proxies</a></li>
     628         <li><a href="#rfc.section.10">10.</a>&nbsp;&nbsp;&nbsp;<a href="#security.considerations">Security Considerations</a><ul>
     629               <li><a href="#rfc.section.10.1">10.1</a>&nbsp;&nbsp;&nbsp;<a href="#personal.information">Personal Information</a></li>
     630               <li><a href="#rfc.section.10.2">10.2</a>&nbsp;&nbsp;&nbsp;<a href="#abuse.of.server.log.information">Abuse of Server Log Information</a></li>
     631               <li><a href="#rfc.section.10.3">10.3</a>&nbsp;&nbsp;&nbsp;<a href="#attack.pathname">Attacks Based On File and Path Names</a></li>
     632               <li><a href="#rfc.section.10.4">10.4</a>&nbsp;&nbsp;&nbsp;<a href="#dns.spoofing">DNS Spoofing</a></li>
     633               <li><a href="#rfc.section.10.5">10.5</a>&nbsp;&nbsp;&nbsp;<a href="#attack.proxies">Proxies and Caching</a></li>
     634               <li><a href="#rfc.section.10.6">10.6</a>&nbsp;&nbsp;&nbsp;<a href="#attack.DoS">Denial of Service Attacks on Proxies</a></li>
    628635            </ul>
    629636         </li>
    630          <li>11.&nbsp;&nbsp;&nbsp;<a href="#ack">Acknowledgments</a></li>
    631          <li>12.&nbsp;&nbsp;&nbsp;<a href="#rfc.references">References</a><ul>
    632                <li>12.1&nbsp;&nbsp;&nbsp;<a href="#rfc.references.1">Normative References</a></li>
    633                <li>12.2&nbsp;&nbsp;&nbsp;<a href="#rfc.references.2">Informative References</a></li>
     637         <li><a href="#rfc.section.11">11.</a>&nbsp;&nbsp;&nbsp;<a href="#ack">Acknowledgments</a></li>
     638         <li><a href="#rfc.section.12">12.</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.references">References</a><ul>
     639               <li><a href="#rfc.section.12.1">12.1</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.references.1">Normative References</a></li>
     640               <li><a href="#rfc.section.12.2">12.2</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.references.2">Informative References</a></li>
    634641            </ul>
    635642         </li>
    636          <li><a href="#rfc.authors">Authors' Addresses</a></li>
    637          <li>A.&nbsp;&nbsp;&nbsp;<a href="#internet.media.type.http">Internet Media Types</a><ul>
    638                <li>A.1&nbsp;&nbsp;&nbsp;<a href="#internet.media.type.message.http">Internet Media Type message/http</a></li>
    639                <li>A.2&nbsp;&nbsp;&nbsp;<a href="#internet.media.type.application.http">Internet Media Type application/http</a></li>
     643         <li><a href="#rfc.section.A">A.</a>&nbsp;&nbsp;&nbsp;<a href="#internet.media.type.http">Internet Media Types</a><ul>
     644               <li><a href="#rfc.section.A.1">A.1</a>&nbsp;&nbsp;&nbsp;<a href="#internet.media.type.message.http">Internet Media Type message/http</a></li>
     645               <li><a href="#rfc.section.A.2">A.2</a>&nbsp;&nbsp;&nbsp;<a href="#internet.media.type.application.http">Internet Media Type application/http</a></li>
    640646            </ul>
    641647         </li>
    642          <li>B.&nbsp;&nbsp;&nbsp;<a href="#tolerant.applications">Tolerant Applications</a></li>
    643          <li>C.&nbsp;&nbsp;&nbsp;<a href="#conversion.of.date.formats">Conversion of Date Formats</a></li>
    644          <li>D.&nbsp;&nbsp;&nbsp;<a href="#compatibility">Compatibility with Previous Versions</a><ul>
    645                <li>D.1&nbsp;&nbsp;&nbsp;<a href="#changes.from.1.0">Changes from HTTP/1.0</a><ul>
    646                      <li>D.1.1&nbsp;&nbsp;&nbsp;<a href="#changes.to.simplify.multi-homed.web.servers.and.conserve.ip.addresses">Changes to Simplify Multi-homed Web Servers and Conserve IP Addresses</a></li>
     648         <li><a href="#rfc.section.B">B.</a>&nbsp;&nbsp;&nbsp;<a href="#tolerant.applications">Tolerant Applications</a></li>
     649         <li><a href="#rfc.section.C">C.</a>&nbsp;&nbsp;&nbsp;<a href="#conversion.of.date.formats">Conversion of Date Formats</a></li>
     650         <li><a href="#rfc.section.D">D.</a>&nbsp;&nbsp;&nbsp;<a href="#compatibility">Compatibility with Previous Versions</a><ul>
     651               <li><a href="#rfc.section.D.1">D.1</a>&nbsp;&nbsp;&nbsp;<a href="#changes.from.1.0">Changes from HTTP/1.0</a><ul>
     652                     <li><a href="#rfc.section.D.1.1">D.1.1</a>&nbsp;&nbsp;&nbsp;<a href="#changes.to.simplify.multi-homed.web.servers.and.conserve.ip.addresses">Changes to Simplify Multi-homed Web Servers and Conserve IP Addresses</a></li>
    647653                  </ul>
    648654               </li>
    649                <li>D.2&nbsp;&nbsp;&nbsp;<a href="#compatibility.with.http.1.0.persistent.connections">Compatibility with HTTP/1.0 Persistent Connections</a></li>
    650                <li>D.3&nbsp;&nbsp;&nbsp;<a href="#changes.from.rfc.2068">Changes from RFC 2068</a></li>
    651                <li>D.4&nbsp;&nbsp;&nbsp;<a href="#changes.from.rfc.2616">Changes from RFC 2616</a></li>
     655               <li><a href="#rfc.section.D.2">D.2</a>&nbsp;&nbsp;&nbsp;<a href="#compatibility.with.http.1.0.persistent.connections">Compatibility with HTTP/1.0 Persistent Connections</a></li>
     656               <li><a href="#rfc.section.D.3">D.3</a>&nbsp;&nbsp;&nbsp;<a href="#changes.from.rfc.2068">Changes from RFC 2068</a></li>
     657               <li><a href="#rfc.section.D.4">D.4</a>&nbsp;&nbsp;&nbsp;<a href="#changes.from.rfc.2616">Changes from RFC 2616</a></li>
    652658            </ul>
    653659         </li>
    654          <li>E.&nbsp;&nbsp;&nbsp;<a href="#change.log">Change Log (to be removed by RFC Editor before publication)</a><ul>
    655                <li>E.1&nbsp;&nbsp;&nbsp;<a href="#rfc.section.E.1">Since RFC2616</a></li>
    656                <li>E.2&nbsp;&nbsp;&nbsp;<a href="#rfc.section.E.2">Since draft-ietf-httpbis-p1-messaging-00</a></li>
    657                <li>E.3&nbsp;&nbsp;&nbsp;<a href="#rfc.section.E.3">Since draft-ietf-httpbis-p1-messaging-01</a></li>
    658                <li>E.4&nbsp;&nbsp;&nbsp;<a href="#changes.since.02">Since draft-ietf-httpbis-p1-messaging-02</a></li>
     660         <li><a href="#rfc.section.E">E.</a>&nbsp;&nbsp;&nbsp;<a href="#change.log">Change Log (to be removed by RFC Editor before publication)</a><ul>
     661               <li><a href="#rfc.section.E.1">E.1</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.E.1">Since RFC2616</a></li>
     662               <li><a href="#rfc.section.E.2">E.2</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.E.2">Since draft-ietf-httpbis-p1-messaging-00</a></li>
     663               <li><a href="#rfc.section.E.3">E.3</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.E.3">Since draft-ietf-httpbis-p1-messaging-01</a></li>
     664               <li><a href="#rfc.section.E.4">E.4</a>&nbsp;&nbsp;&nbsp;<a href="#changes.since.02">Since draft-ietf-httpbis-p1-messaging-02</a></li>
    659665            </ul>
    660666         </li>
    661667         <li><a href="#rfc.index">Index</a></li>
     668         <li><a href="#rfc.authors">Authors' Addresses</a></li>
    662669         <li><a href="#rfc.ipr">Intellectual Property and Copyright Statements</a></li>
    663670      </ul>
    664       <h1 id="rfc.section.1" class="np"><a href="#rfc.section.1">1.</a>&nbsp;<a id="introduction" href="#introduction">Introduction</a></h1>
    665       <p id="rfc.section.1.p.1">The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypermedia information
    666          systems. HTTP has been in use by the World-Wide Web global information initiative since 1990. The first version of HTTP, commonly
    667          referred to as HTTP/0.9, was a simple protocol for raw data transfer across the Internet with only a single method and no
    668          metadata. HTTP/1.0, as defined by <a href="#RFC1945" id="rfc.xref.RFC1945.1"><cite title="Hypertext Transfer Protocol -- HTTP/1.0">[RFC1945]</cite></a>, improved the protocol by allowing messages to be in the format of MIME-like messages, containing metadata about the data
    669          transferred and modifiers on the request/response semantics. However, HTTP/1.0 did not sufficiently take into consideration
    670          the effects of hierarchical proxies, caching, the need for persistent connections, or name-based virtual hosts. In addition,
    671          the proliferation of incompletely-implemented applications calling themselves "HTTP/1.0" necessitated a protocol version change
    672          in order for two communicating applications to determine each other's true capabilities.
    673       </p>
    674       <p id="rfc.section.1.p.2">This document is Part 1 of the seven-part specification that defines the protocol referred to as "HTTP/1.1", obsoleting <a href="#RFC2616" id="rfc.xref.RFC2616.1"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>. HTTP/1.1 remains compatible with HTTP/1.0 by including more stringent requirements that enable reliable implementations
    675          and adding only those new features that will either be safely ignored by an HTTP/1.0 recipient or only sent when communicating
    676          with a party advertising compliance with HTTP/1.1. Part 1 defines those aspects of HTTP/1.1 related to overall network operation,
    677          message framing, interaction with transport protocols, and URI schemes.
    678       </p>
    679       <p id="rfc.section.1.p.3">This document is currently disorganized in order to minimize the changes between drafts and enable reviewers to see the smaller
    680          errata changes. The next draft will reorganize the sections to better reflect the content. In particular, the sections will
    681          be organized according to the typical process of deciding when to use HTTP (URI schemes), overall network operation, connection
    682          management, message framing, and generic message parsing. The current mess reflects how widely dispersed these topics and
    683          associated requirements had become in <a href="#RFC2616" id="rfc.xref.RFC2616.2"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>.
    684       </p>
    685       <h2 id="rfc.section.1.1"><a href="#rfc.section.1.1">1.1</a>&nbsp;<a id="intro.purpose" href="#intro.purpose">Purpose</a></h2>
    686       <p id="rfc.section.1.1.p.1">Practical information systems require more functionality than simple retrieval, including search, front-end update, and annotation.
    687          HTTP allows an open-ended set of methods and headers that indicate the purpose of a request <a href="#RFC2324" id="rfc.xref.RFC2324.1"><cite title="Hyper Text Coffee Pot Control Protocol (HTCPCP/1.0)">[RFC2324]</cite></a>. It builds on the discipline of reference provided by the Uniform Resource Identifier (URI) <a href="#RFC1630" id="rfc.xref.RFC1630.1"><cite title="Universal Resource Identifiers in WWW: A Unifying Syntax for the Expression of Names and Addresses of Objects on the Network as used in the World-Wide Web">[RFC1630]</cite></a>, as a location (URL) <a href="#RFC1738" id="rfc.xref.RFC1738.1"><cite title="Uniform Resource Locators (URL)">[RFC1738]</cite></a> or name (URN) <a href="#RFC1737" id="rfc.xref.RFC1737.1"><cite title="Functional Requirements for Uniform Resource Names">[RFC1737]</cite></a>, for indicating the resource to which a method is to be applied. Messages are passed in a format similar to that used by
    688          Internet mail <a href="#RFC2822" id="rfc.xref.RFC2822.1"><cite title="Internet Message Format">[RFC2822]</cite></a> as defined by the Multipurpose Internet Mail Extensions (MIME) <a href="#RFC2045" id="rfc.xref.RFC2045.1"><cite title="Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies">[RFC2045]</cite></a>.
    689       </p>
    690       <p id="rfc.section.1.1.p.2">HTTP is also used as a generic protocol for communication between user agents and proxies/gateways to other Internet systems,
    691          including those supported by the SMTP <a href="#RFC2821" id="rfc.xref.RFC2821.1"><cite title="Simple Mail Transfer Protocol">[RFC2821]</cite></a>, NNTP <a href="#RFC3977" id="rfc.xref.RFC3977.1"><cite title="Network News Transfer Protocol (NNTP)">[RFC3977]</cite></a>, FTP <a href="#RFC959" id="rfc.xref.RFC959.1"><cite title="File Transfer Protocol">[RFC959]</cite></a>, Gopher <a href="#RFC1436" id="rfc.xref.RFC1436.1"><cite title="The Internet Gopher Protocol (a distributed document search and retrieval protocol)">[RFC1436]</cite></a>, and WAIS <a href="#WAIS" id="rfc.xref.WAIS.1"><cite title="WAIS Interface Protocol Prototype Functional Specification (v1.5)">[WAIS]</cite></a> protocols. In this way, HTTP allows basic hypermedia access to resources available from diverse applications.
    692       </p>
    693       <h2 id="rfc.section.1.2"><a href="#rfc.section.1.2">1.2</a>&nbsp;<a id="intro.requirements" href="#intro.requirements">Requirements</a></h2>
    694       <p id="rfc.section.1.2.p.1">The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"
    695          in this document are to be interpreted as described in <a href="#RFC2119" id="rfc.xref.RFC2119.1"><cite title="Key words for use in RFCs to Indicate Requirement Levels">[RFC2119]</cite></a>.
    696       </p>
    697       <p id="rfc.section.1.2.p.2">An implementation is not compliant if it fails to satisfy one or more of the <em class="bcp14">MUST</em> or <em class="bcp14">REQUIRED</em> level requirements for the protocols it implements. An implementation that satisfies all the <em class="bcp14">MUST</em> or <em class="bcp14">REQUIRED</em> level and all the <em class="bcp14">SHOULD</em> level requirements for its protocols is said to be "unconditionally compliant"; one that satisfies all the <em class="bcp14">MUST</em> level requirements but not all the <em class="bcp14">SHOULD</em> level requirements for its protocols is said to be "conditionally compliant."
    698       </p>
    699       <h2 id="rfc.section.1.3"><a href="#rfc.section.1.3">1.3</a>&nbsp;<a id="intro.terminology" href="#intro.terminology">Terminology</a></h2>
    700       <p id="rfc.section.1.3.p.1">This specification uses a number of terms to refer to the roles played by participants in, and objects of, the HTTP communication.</p>
    701       <p id="rfc.section.1.3.p.2"> <span id="rfc.iref.c.1"></span>  <dfn>connection</dfn> 
    702       </p>
    703       <ul class="empty">
    704          <li>A transport layer virtual circuit established between two programs for the purpose of communication.</li>
    705       </ul>
    706       <p id="rfc.section.1.3.p.3"> <span id="rfc.iref.m.1"></span>  <dfn>message</dfn> 
    707       </p>
    708       <ul class="empty">
    709          <li>The basic unit of HTTP communication, consisting of a structured sequence of octets matching the syntax defined in <a href="#http.message" title="HTTP Message">Section&nbsp;4</a> and transmitted via the connection.
    710          </li>
    711       </ul>
    712       <p id="rfc.section.1.3.p.4"> <span id="rfc.iref.r.1"></span>  <dfn>request</dfn> 
    713       </p>
    714       <ul class="empty">
    715          <li>An HTTP request message, as defined in <a href="#request" title="Request">Section&nbsp;5</a>.
    716          </li>
    717       </ul>
    718       <p id="rfc.section.1.3.p.5"> <span id="rfc.iref.r.2"></span>  <dfn>response</dfn> 
    719       </p>
    720       <ul class="empty">
    721          <li>An HTTP response message, as defined in <a href="#response" title="Response">Section&nbsp;6</a>.
    722          </li>
    723       </ul>
    724       <p id="rfc.section.1.3.p.6"> <span id="rfc.iref.r.3"></span>  <dfn>resource</dfn> 
    725       </p>
    726       <ul class="empty">
    727          <li>A network data object or service that can be identified by a URI, as defined in <a href="#uri" title="Uniform Resource Identifiers">Section&nbsp;3.2</a>. Resources may be available in multiple representations (e.g. multiple languages, data formats, size, and resolutions) or
    728             vary in other ways.
    729          </li>
    730       </ul>
    731       <p id="rfc.section.1.3.p.7"> <span id="rfc.iref.e.1"></span>  <dfn>entity</dfn> 
    732       </p>
    733       <ul class="empty">
    734          <li>The information transferred as the payload of a request or response. An entity consists of metainformation in the form of
    735             entity-header fields and content in the form of an entity-body, as described in <a href="p3-payload.html#entity" title="Entity">Section 4</a> of <a href="#Part3" id="rfc.xref.Part3.1"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>.
    736          </li>
    737       </ul>
    738       <p id="rfc.section.1.3.p.8"> <span id="rfc.iref.r.4"></span>  <dfn>representation</dfn> 
    739       </p>
    740       <ul class="empty">
    741          <li>An entity included with a response that is subject to content negotiation, as described in <a href="p3-payload.html#content.negotiation" title="Content Negotiation">Section 5</a> of <a href="#Part3" id="rfc.xref.Part3.2"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>. There may exist multiple representations associated with a particular response status.
    742          </li>
    743       </ul>
    744       <p id="rfc.section.1.3.p.9"> <span id="rfc.iref.c.2"></span>  <dfn>content negotiation</dfn> 
    745       </p>
    746       <ul class="empty">
    747          <li>The mechanism for selecting the appropriate representation when servicing a request, as described in <a href="p3-payload.html#content.negotiation" title="Content Negotiation">Section 5</a> of <a href="#Part3" id="rfc.xref.Part3.3"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>. The representation of entities in any response can be negotiated (including error responses).
    748          </li>
    749       </ul>
    750       <p id="rfc.section.1.3.p.10"> <span id="rfc.iref.v.1"></span>  <dfn>variant</dfn> 
    751       </p>
    752       <ul class="empty">
    753          <li>A resource may have one, or more than one, representation(s) associated with it at any given instant. Each of these representations
    754             is termed a `variant'. Use of the term `variant' does not necessarily imply that the resource is subject to content negotiation.
    755          </li>
    756       </ul>
    757       <p id="rfc.section.1.3.p.11"> <span id="rfc.iref.c.3"></span>  <dfn>client</dfn> 
    758       </p>
    759       <ul class="empty">
    760          <li>A program that establishes connections for the purpose of sending requests.</li>
    761       </ul>
    762       <p id="rfc.section.1.3.p.12"> <span id="rfc.iref.u.1"></span>  <dfn>user agent</dfn> 
    763       </p>
    764       <ul class="empty">
    765          <li>The client which initiates a request. These are often browsers, editors, spiders (web-traversing robots), or other end user
    766             tools.
    767          </li>
    768       </ul>
    769       <p id="rfc.section.1.3.p.13"> <span id="rfc.iref.s.1"></span>  <dfn>server</dfn> 
    770       </p>
    771       <ul class="empty">
    772          <li>An application program that accepts connections in order to service requests by sending back responses. Any given program
    773             may be capable of being both a client and a server; our use of these terms refers only to the role being performed by the
    774             program for a particular connection, rather than to the program's capabilities in general. Likewise, any server may act as
    775             an origin server, proxy, gateway, or tunnel, switching behavior based on the nature of each request.
    776          </li>
    777       </ul>
    778       <p id="rfc.section.1.3.p.14"> <span id="rfc.iref.o.1"></span>  <dfn>origin server</dfn> 
    779       </p>
    780       <ul class="empty">
    781          <li>The server on which a given resource resides or is to be created.</li>
    782       </ul>
    783       <p id="rfc.section.1.3.p.15"> <span id="rfc.iref.p.1"></span>  <dfn>proxy</dfn> 
    784       </p>
    785       <ul class="empty">
    786          <li>An intermediary program which acts as both a server and a client for the purpose of making requests on behalf of other clients.
    787             Requests are serviced internally or by passing them on, with possible translation, to other servers. A proxy <em class="bcp14">MUST</em> implement both the client and server requirements of this specification. A "transparent proxy" is a proxy that does not modify
    788             the request or response beyond what is required for proxy authentication and identification. A "non-transparent proxy" is
    789             a proxy that modifies the request or response in order to provide some added service to the user agent, such as group annotation
    790             services, media type transformation, protocol reduction, or anonymity filtering. Except where either transparent or non-transparent
    791             behavior is explicitly stated, the HTTP proxy requirements apply to both types of proxies.
    792          </li>
    793       </ul>
    794       <p id="rfc.section.1.3.p.16"> <span id="rfc.iref.g.1"></span>  <dfn>gateway</dfn> 
    795       </p>
    796       <ul class="empty">
    797          <li>A server which acts as an intermediary for some other server. Unlike a proxy, a gateway receives requests as if it were the
    798             origin server for the requested resource; the requesting client may not be aware that it is communicating with a gateway.
    799          </li>
    800       </ul>
    801       <p id="rfc.section.1.3.p.17"> <span id="rfc.iref.t.1"></span>  <dfn>tunnel</dfn> 
    802       </p>
    803       <ul class="empty">
    804          <li>An intermediary program which is acting as a blind relay between two connections. Once active, a tunnel is not considered
    805             a party to the HTTP communication, though the tunnel may have been initiated by an HTTP request. The tunnel ceases to exist
    806             when both ends of the relayed connections are closed.
    807          </li>
    808       </ul>
    809       <p id="rfc.section.1.3.p.18"> <span id="rfc.iref.c.4"></span>  <dfn>cache</dfn> 
    810       </p>
    811       <ul class="empty">
    812          <li>A program's local store of response messages and the subsystem that controls its message storage, retrieval, and deletion.
    813             A cache stores cacheable responses in order to reduce the response time and network bandwidth consumption on future, equivalent
    814             requests. Any client or server may include a cache, though a cache cannot be used by a server that is acting as a tunnel.
    815          </li>
    816       </ul>
    817       <p id="rfc.section.1.3.p.19"> <span id="rfc.iref.c.5"></span>  <dfn>cacheable</dfn> 
    818       </p>
    819       <ul class="empty">
    820          <li>A response is cacheable if a cache is allowed to store a copy of the response message for use in answering subsequent requests.
    821             The rules for determining the cacheability of HTTP responses are defined in <a href="p6-cache.html#caching" title="Introduction">Section 1</a> of <a href="#Part6" id="rfc.xref.Part6.1"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>. Even if a resource is cacheable, there may be additional constraints on whether a cache can use the cached copy for a particular
    822             request.
    823          </li>
    824       </ul>
    825       <p id="rfc.section.1.3.p.20"> <span id="rfc.iref.u.2"></span>  <span id="rfc.iref.d.1"></span>  <dfn>upstream</dfn>/<dfn>downstream</dfn> 
    826       </p>
    827       <ul class="empty">
    828          <li>Upstream and downstream describe the flow of a message: all messages flow from upstream to downstream.</li>
    829       </ul>
    830       <p id="rfc.section.1.3.p.21"> <span id="rfc.iref.i.1"></span>  <span id="rfc.iref.o.2"></span>  <dfn>inbound</dfn>/<dfn>outbound</dfn> 
    831       </p>
    832       <ul class="empty">
    833          <li>Inbound and outbound refer to the request and response paths for messages: "inbound" means "traveling toward the origin server",
    834             and "outbound" means "traveling toward the user agent"
    835          </li>
    836       </ul>
    837       <h2 id="rfc.section.1.4"><a href="#rfc.section.1.4">1.4</a>&nbsp;<a id="intro.overall.operation" href="#intro.overall.operation">Overall Operation</a></h2>
    838       <p id="rfc.section.1.4.p.1">HTTP is a request/response protocol. A client sends a request to the server in the form of a request method, URI, and protocol
    839          version, followed by a MIME-like message containing request modifiers, client information, and possible body content over
    840          a connection with a server. The server responds with a status line, including the message's protocol version and a success
    841          or error code, followed by a MIME-like message containing server information, entity metainformation, and possible entity-body
    842          content. The relationship between HTTP and MIME is described in <a href="p3-payload.html#differences.between.http.entities.and.rfc.2045.entities" title="Differences Between HTTP Entities and RFC 2045 Entities">Appendix A</a> of <a href="#Part3" id="rfc.xref.Part3.4"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>.
    843       </p>
    844       <p id="rfc.section.1.4.p.2">Most HTTP communication is initiated by a user agent and consists of a request to be applied to a resource on some origin
    845          server. In the simplest case, this may be accomplished via a single connection (v) between the user agent (UA) and the origin
    846          server (O).
    847       </p>
    848       <div id="rfc.figure.u.1"></div><pre class="drawing">       request chain ------------------------&gt;
     671      <div id="introduction">
     672         <h1 id="rfc.section.1" class="np"><a href="#rfc.section.1">1.</a>&nbsp;<a href="#introduction">Introduction</a></h1>
     673         <p id="rfc.section.1.p.1">The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypermedia information
     674            systems. HTTP has been in use by the World-Wide Web global information initiative since 1990. The first version of HTTP, commonly
     675            referred to as HTTP/0.9, was a simple protocol for raw data transfer across the Internet with only a single method and no
     676            metadata. HTTP/1.0, as defined by <a href="#RFC1945" id="rfc.xref.RFC1945.1"><cite title="Hypertext Transfer Protocol -- HTTP/1.0">[RFC1945]</cite></a>, improved the protocol by allowing messages to be in the format of MIME-like messages, containing metadata about the data
     677            transferred and modifiers on the request/response semantics. However, HTTP/1.0 did not sufficiently take into consideration
     678            the effects of hierarchical proxies, caching, the need for persistent connections, or name-based virtual hosts. In addition,
     679            the proliferation of incompletely-implemented applications calling themselves "HTTP/1.0" necessitated a protocol version change
     680            in order for two communicating applications to determine each other's true capabilities.
     681         </p>
     682         <p id="rfc.section.1.p.2">This document is Part 1 of the seven-part specification that defines the protocol referred to as "HTTP/1.1", obsoleting <a href="#RFC2616" id="rfc.xref.RFC2616.1"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>. HTTP/1.1 remains compatible with HTTP/1.0 by including more stringent requirements that enable reliable implementations
     683            and adding only those new features that will either be safely ignored by an HTTP/1.0 recipient or only sent when communicating
     684            with a party advertising compliance with HTTP/1.1. Part 1 defines those aspects of HTTP/1.1 related to overall network operation,
     685            message framing, interaction with transport protocols, and URI schemes.
     686         </p>
     687         <p id="rfc.section.1.p.3">This document is currently disorganized in order to minimize the changes between drafts and enable reviewers to see the smaller
     688            errata changes. The next draft will reorganize the sections to better reflect the content. In particular, the sections will
     689            be organized according to the typical process of deciding when to use HTTP (URI schemes), overall network operation, connection
     690            management, message framing, and generic message parsing. The current mess reflects how widely dispersed these topics and
     691            associated requirements had become in <a href="#RFC2616" id="rfc.xref.RFC2616.2"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>.
     692         </p>
     693         <div id="intro.purpose">
     694            <h2 id="rfc.section.1.1"><a href="#rfc.section.1.1">1.1</a>&nbsp;<a href="#intro.purpose">Purpose</a></h2>
     695            <p id="rfc.section.1.1.p.1">Practical information systems require more functionality than simple retrieval, including search, front-end update, and annotation.
     696               HTTP allows an open-ended set of methods and headers that indicate the purpose of a request <a href="#RFC2324" id="rfc.xref.RFC2324.1"><cite title="Hyper Text Coffee Pot Control Protocol (HTCPCP/1.0)">[RFC2324]</cite></a>. It builds on the discipline of reference provided by the Uniform Resource Identifier (URI) <a href="#RFC1630" id="rfc.xref.RFC1630.1"><cite title="Universal Resource Identifiers in WWW: A Unifying Syntax for the Expression of Names and Addresses of Objects on the Network as used in the World-Wide Web">[RFC1630]</cite></a>, as a location (URL) <a href="#RFC1738" id="rfc.xref.RFC1738.1"><cite title="Uniform Resource Locators (URL)">[RFC1738]</cite></a> or name (URN) <a href="#RFC1737" id="rfc.xref.RFC1737.1"><cite title="Functional Requirements for Uniform Resource Names">[RFC1737]</cite></a>, for indicating the resource to which a method is to be applied. Messages are passed in a format similar to that used by
     697               Internet mail <a href="#RFC2822" id="rfc.xref.RFC2822.1"><cite title="Internet Message Format">[RFC2822]</cite></a> as defined by the Multipurpose Internet Mail Extensions (MIME) <a href="#RFC2045" id="rfc.xref.RFC2045.1"><cite title="Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies">[RFC2045]</cite></a>.
     698            </p>
     699            <p id="rfc.section.1.1.p.2">HTTP is also used as a generic protocol for communication between user agents and proxies/gateways to other Internet systems,
     700               including those supported by the SMTP <a href="#RFC2821" id="rfc.xref.RFC2821.1"><cite title="Simple Mail Transfer Protocol">[RFC2821]</cite></a>, NNTP <a href="#RFC3977" id="rfc.xref.RFC3977.1"><cite title="Network News Transfer Protocol (NNTP)">[RFC3977]</cite></a>, FTP <a href="#RFC959" id="rfc.xref.RFC959.1"><cite title="File Transfer Protocol">[RFC959]</cite></a>, Gopher <a href="#RFC1436" id="rfc.xref.RFC1436.1"><cite title="The Internet Gopher Protocol (a distributed document search and retrieval protocol)">[RFC1436]</cite></a>, and WAIS <a href="#WAIS" id="rfc.xref.WAIS.1"><cite title="WAIS Interface Protocol Prototype Functional Specification (v1.5)">[WAIS]</cite></a> protocols. In this way, HTTP allows basic hypermedia access to resources available from diverse applications.
     701            </p>
     702         </div>
     703         <div id="intro.requirements">
     704            <h2 id="rfc.section.1.2"><a href="#rfc.section.1.2">1.2</a>&nbsp;<a href="#intro.requirements">Requirements</a></h2>
     705            <p id="rfc.section.1.2.p.1">The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"
     706               in this document are to be interpreted as described in <a href="#RFC2119" id="rfc.xref.RFC2119.1"><cite title="Key words for use in RFCs to Indicate Requirement Levels">[RFC2119]</cite></a>.
     707            </p>
     708            <p id="rfc.section.1.2.p.2">An implementation is not compliant if it fails to satisfy one or more of the <em class="bcp14">MUST</em> or <em class="bcp14">REQUIRED</em> level requirements for the protocols it implements. An implementation that satisfies all the <em class="bcp14">MUST</em> or <em class="bcp14">REQUIRED</em> level and all the <em class="bcp14">SHOULD</em> level requirements for its protocols is said to be "unconditionally compliant"; one that satisfies all the <em class="bcp14">MUST</em> level requirements but not all the <em class="bcp14">SHOULD</em> level requirements for its protocols is said to be "conditionally compliant."
     709            </p>
     710         </div>
     711         <div id="intro.terminology">
     712            <h2 id="rfc.section.1.3"><a href="#rfc.section.1.3">1.3</a>&nbsp;<a href="#intro.terminology">Terminology</a></h2>
     713            <p id="rfc.section.1.3.p.1">This specification uses a number of terms to refer to the roles played by participants in, and objects of, the HTTP communication.</p>
     714            <p id="rfc.section.1.3.p.2"><span id="rfc.iref.c.1"></span> <dfn>connection</dfn>
     715            </p>
     716            <ul class="empty">
     717               <li>A transport layer virtual circuit established between two programs for the purpose of communication.</li>
     718            </ul>
     719            <p id="rfc.section.1.3.p.3"><span id="rfc.iref.m.1"></span> <dfn>message</dfn>
     720            </p>
     721            <ul class="empty">
     722               <li>The basic unit of HTTP communication, consisting of a structured sequence of octets matching the syntax defined in <a href="#http.message" title="HTTP Message">Section&nbsp;4</a> and transmitted via the connection.
     723               </li>
     724            </ul>
     725            <p id="rfc.section.1.3.p.4"><span id="rfc.iref.r.1"></span> <dfn>request</dfn>
     726            </p>
     727            <ul class="empty">
     728               <li>An HTTP request message, as defined in <a href="#request" title="Request">Section&nbsp;5</a>.
     729               </li>
     730            </ul>
     731            <p id="rfc.section.1.3.p.5"><span id="rfc.iref.r.2"></span> <dfn>response</dfn>
     732            </p>
     733            <ul class="empty">
     734               <li>An HTTP response message, as defined in <a href="#response" title="Response">Section&nbsp;6</a>.
     735               </li>
     736            </ul>
     737            <p id="rfc.section.1.3.p.6"><span id="rfc.iref.r.3"></span> <dfn>resource</dfn>
     738            </p>
     739            <ul class="empty">
     740               <li>A network data object or service that can be identified by a URI, as defined in <a href="#uri" title="Uniform Resource Identifiers">Section&nbsp;3.2</a>. Resources may be available in multiple representations (e.g. multiple languages, data formats, size, and resolutions) or
     741                  vary in other ways.
     742               </li>
     743            </ul>
     744            <p id="rfc.section.1.3.p.7"><span id="rfc.iref.e.1"></span> <dfn>entity</dfn>
     745            </p>
     746            <ul class="empty">
     747               <li>The information transferred as the payload of a request or response. An entity consists of metainformation in the form of
     748                  entity-header fields and content in the form of an entity-body, as described in <a href="p3-payload.html#entity" title="Entity">Section 4</a> of <a href="#Part3" id="rfc.xref.Part3.1"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>.
     749               </li>
     750            </ul>
     751            <p id="rfc.section.1.3.p.8"><span id="rfc.iref.r.4"></span> <dfn>representation</dfn>
     752            </p>
     753            <ul class="empty">
     754               <li>An entity included with a response that is subject to content negotiation, as described in <a href="p3-payload.html#content.negotiation" title="Content Negotiation">Section 5</a> of <a href="#Part3" id="rfc.xref.Part3.2"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>. There may exist multiple representations associated with a particular response status.
     755               </li>
     756            </ul>
     757            <p id="rfc.section.1.3.p.9"><span id="rfc.iref.c.2"></span> <dfn>content negotiation</dfn>
     758            </p>
     759            <ul class="empty">
     760               <li>The mechanism for selecting the appropriate representation when servicing a request, as described in <a href="p3-payload.html#content.negotiation" title="Content Negotiation">Section 5</a> of <a href="#Part3" id="rfc.xref.Part3.3"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>. The representation of entities in any response can be negotiated (including error responses).
     761               </li>
     762            </ul>
     763            <p id="rfc.section.1.3.p.10"><span id="rfc.iref.v.1"></span> <dfn>variant</dfn>
     764            </p>
     765            <ul class="empty">
     766               <li>A resource may have one, or more than one, representation(s) associated with it at any given instant. Each of these representations
     767                  is termed a `variant'. Use of the term `variant' does not necessarily imply that the resource is subject to content negotiation.
     768               </li>
     769            </ul>
     770            <p id="rfc.section.1.3.p.11"><span id="rfc.iref.c.3"></span> <dfn>client</dfn>
     771            </p>
     772            <ul class="empty">
     773               <li>A program that establishes connections for the purpose of sending requests.</li>
     774            </ul>
     775            <p id="rfc.section.1.3.p.12"><span id="rfc.iref.u.1"></span> <dfn>user agent</dfn>
     776            </p>
     777            <ul class="empty">
     778               <li>The client which initiates a request. These are often browsers, editors, spiders (web-traversing robots), or other end user
     779                  tools.
     780               </li>
     781            </ul>
     782            <p id="rfc.section.1.3.p.13"><span id="rfc.iref.s.1"></span> <dfn>server</dfn>
     783            </p>
     784            <ul class="empty">
     785               <li>An application program that accepts connections in order to service requests by sending back responses. Any given program
     786                  may be capable of being both a client and a server; our use of these terms refers only to the role being performed by the
     787                  program for a particular connection, rather than to the program's capabilities in general. Likewise, any server may act as
     788                  an origin server, proxy, gateway, or tunnel, switching behavior based on the nature of each request.
     789               </li>
     790            </ul>
     791            <p id="rfc.section.1.3.p.14"><span id="rfc.iref.o.1"></span> <dfn>origin server</dfn>
     792            </p>
     793            <ul class="empty">
     794               <li>The server on which a given resource resides or is to be created.</li>
     795            </ul>
     796            <p id="rfc.section.1.3.p.15"><span id="rfc.iref.p.1"></span> <dfn>proxy</dfn>
     797            </p>
     798            <ul class="empty">
     799               <li>An intermediary program which acts as both a server and a client for the purpose of making requests on behalf of other clients.
     800                  Requests are serviced internally or by passing them on, with possible translation, to other servers. A proxy <em class="bcp14">MUST</em> implement both the client and server requirements of this specification. A "transparent proxy" is a proxy that does not modify
     801                  the request or response beyond what is required for proxy authentication and identification. A "non-transparent proxy" is
     802                  a proxy that modifies the request or response in order to provide some added service to the user agent, such as group annotation
     803                  services, media type transformation, protocol reduction, or anonymity filtering. Except where either transparent or non-transparent
     804                  behavior is explicitly stated, the HTTP proxy requirements apply to both types of proxies.
     805               </li>
     806            </ul>
     807            <p id="rfc.section.1.3.p.16"><span id="rfc.iref.g.1"></span> <dfn>gateway</dfn>
     808            </p>
     809            <ul class="empty">
     810               <li>A server which acts as an intermediary for some other server. Unlike a proxy, a gateway receives requests as if it were the
     811                  origin server for the requested resource; the requesting client may not be aware that it is communicating with a gateway.
     812               </li>
     813            </ul>
     814            <p id="rfc.section.1.3.p.17"><span id="rfc.iref.t.1"></span> <dfn>tunnel</dfn>
     815            </p>
     816            <ul class="empty">
     817               <li>An intermediary program which is acting as a blind relay between two connections. Once active, a tunnel is not considered
     818                  a party to the HTTP communication, though the tunnel may have been initiated by an HTTP request. The tunnel ceases to exist
     819                  when both ends of the relayed connections are closed.
     820               </li>
     821            </ul>
     822            <p id="rfc.section.1.3.p.18"><span id="rfc.iref.c.4"></span> <dfn>cache</dfn>
     823            </p>
     824            <ul class="empty">
     825               <li>A program's local store of response messages and the subsystem that controls its message storage, retrieval, and deletion.
     826                  A cache stores cacheable responses in order to reduce the response time and network bandwidth consumption on future, equivalent
     827                  requests. Any client or server may include a cache, though a cache cannot be used by a server that is acting as a tunnel.
     828               </li>
     829            </ul>
     830            <p id="rfc.section.1.3.p.19"><span id="rfc.iref.c.5"></span> <dfn>cacheable</dfn>
     831            </p>
     832            <ul class="empty">
     833               <li>A response is cacheable if a cache is allowed to store a copy of the response message for use in answering subsequent requests.
     834                  The rules for determining the cacheability of HTTP responses are defined in <a href="p6-cache.html#caching" title="Introduction">Section 1</a> of <a href="#Part6" id="rfc.xref.Part6.1"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>. Even if a resource is cacheable, there may be additional constraints on whether a cache can use the cached copy for a particular
     835                  request.
     836               </li>
     837            </ul>
     838            <p id="rfc.section.1.3.p.20"><span id="rfc.iref.u.2"></span> <span id="rfc.iref.d.1"></span> <dfn>upstream</dfn>/<dfn>downstream</dfn>
     839            </p>
     840            <ul class="empty">
     841               <li>Upstream and downstream describe the flow of a message: all messages flow from upstream to downstream.</li>
     842            </ul>
     843            <p id="rfc.section.1.3.p.21"><span id="rfc.iref.i.1"></span> <span id="rfc.iref.o.2"></span> <dfn>inbound</dfn>/<dfn>outbound</dfn>
     844            </p>
     845            <ul class="empty">
     846               <li>Inbound and outbound refer to the request and response paths for messages: "inbound" means "traveling toward the origin server",
     847                  and "outbound" means "traveling toward the user agent"
     848               </li>
     849            </ul>
     850         </div>
     851         <div id="intro.overall.operation">
     852            <h2 id="rfc.section.1.4"><a href="#rfc.section.1.4">1.4</a>&nbsp;<a href="#intro.overall.operation">Overall Operation</a></h2>
     853            <p id="rfc.section.1.4.p.1">HTTP is a request/response protocol. A client sends a request to the server in the form of a request method, URI, and protocol
     854               version, followed by a MIME-like message containing request modifiers, client information, and possible body content over
     855               a connection with a server. The server responds with a status line, including the message's protocol version and a success
     856               or error code, followed by a MIME-like message containing server information, entity metainformation, and possible entity-body
     857               content. The relationship between HTTP and MIME is described in <a href="p3-payload.html#differences.between.http.entities.and.rfc.2045.entities" title="Differences Between HTTP Entities and RFC 2045 Entities">Appendix A</a> of <a href="#Part3" id="rfc.xref.Part3.4"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>.
     858            </p>
     859            <p id="rfc.section.1.4.p.2">Most HTTP communication is initiated by a user agent and consists of a request to be applied to a resource on some origin
     860               server. In the simplest case, this may be accomplished via a single connection (v) between the user agent (UA) and the origin
     861               server (O).
     862            </p>
     863            <div id="rfc.figure.u.1"></div><pre class="drawing">       request chain ------------------------&gt;
    849864    UA -------------------v------------------- O
    850865       &lt;----------------------- response chain
    851866</pre><p id="rfc.section.1.4.p.4">A more complicated situation occurs when one or more intermediaries are present in the request/response chain. There are three
    852          common forms of intermediary: proxy, gateway, and tunnel. A proxy is a forwarding agent, receiving requests for a URI in its
    853          absolute form, rewriting all or part of the message, and forwarding the reformatted request toward the server identified by
    854          the URI. A gateway is a receiving agent, acting as a layer above some other server(s) and, if necessary, translating the requests
    855          to the underlying server's protocol. A tunnel acts as a relay point between two connections without changing the messages;
    856          tunnels are used when the communication needs to pass through an intermediary (such as a firewall) even when the intermediary
    857          cannot understand the contents of the messages.
    858       </p>
    859       <div id="rfc.figure.u.2"></div><pre class="drawing">       request chain --------------------------------------&gt;
     867               common forms of intermediary: proxy, gateway, and tunnel. A proxy is a forwarding agent, receiving requests for a URI in its
     868               absolute form, rewriting all or part of the message, and forwarding the reformatted request toward the server identified by
     869               the URI. A gateway is a receiving agent, acting as a layer above some other server(s) and, if necessary, translating the requests
     870               to the underlying server's protocol. A tunnel acts as a relay point between two connections without changing the messages;
     871               tunnels are used when the communication needs to pass through an intermediary (such as a firewall) even when the intermediary
     872               cannot understand the contents of the messages.
     873            </p>
     874            <div id="rfc.figure.u.2"></div><pre class="drawing">       request chain --------------------------------------&gt;
    860875    UA -----v----- A -----v----- B -----v----- C -----v----- O
    861876       &lt;------------------------------------- response chain
    862877</pre><p id="rfc.section.1.4.p.6">The figure above shows three intermediaries (A, B, and C) between the user agent and origin server. A request or response
    863          message that travels the whole chain will pass through four separate connections. This distinction is important because some
    864          HTTP communication options may apply only to the connection with the nearest, non-tunnel neighbor, only to the end-points
    865          of the chain, or to all connections along the chain. Although the diagram is linear, each participant may be engaged in multiple,
    866          simultaneous communications. For example, B may be receiving requests from many clients other than A, and/or forwarding requests
    867          to servers other than C, at the same time that it is handling A's request.
    868       </p>
    869       <p id="rfc.section.1.4.p.7">Any party to the communication which is not acting as a tunnel may employ an internal cache for handling requests. The effect
    870          of a cache is that the request/response chain is shortened if one of the participants along the chain has a cached response
    871          applicable to that request. The following illustrates the resulting chain if B has a cached copy of an earlier response from
    872          O (via C) for a request which has not been cached by UA or A.
    873       </p>
    874       <div id="rfc.figure.u.3"></div><pre class="drawing">          request chain ----------&gt;
     878               message that travels the whole chain will pass through four separate connections. This distinction is important because some
     879               HTTP communication options may apply only to the connection with the nearest, non-tunnel neighbor, only to the end-points
     880               of the chain, or to all connections along the chain. Although the diagram is linear, each participant may be engaged in multiple,
     881               simultaneous communications. For example, B may be receiving requests from many clients other than A, and/or forwarding requests
     882               to servers other than C, at the same time that it is handling A's request.
     883            </p>
     884            <p id="rfc.section.1.4.p.7">Any party to the communication which is not acting as a tunnel may employ an internal cache for handling requests. The effect
     885               of a cache is that the request/response chain is shortened if one of the participants along the chain has a cached response
     886               applicable to that request. The following illustrates the resulting chain if B has a cached copy of an earlier response from
     887               O (via C) for a request which has not been cached by UA or A.
     888            </p>
     889            <div id="rfc.figure.u.3"></div><pre class="drawing">          request chain ----------&gt;
    875890       UA -----v----- A -----v----- B - - - - - - C - - - - - - O
    876891          &lt;--------- response chain
    877892</pre><p id="rfc.section.1.4.p.9">Not all responses are usefully cacheable, and some requests may contain modifiers which place special requirements on cache
    878          behavior. HTTP requirements for cache behavior and cacheable responses are defined in <a href="p6-cache.html#caching" title="Introduction">Section 1</a> of <a href="#Part6" id="rfc.xref.Part6.2"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>.
    879       </p>
    880       <p id="rfc.section.1.4.p.10">In fact, there are a wide variety of architectures and configurations of caches and proxies currently being experimented with
    881          or deployed across the World Wide Web. These systems include national hierarchies of proxy caches to save transoceanic bandwidth,
    882          systems that broadcast or multicast cache entries, organizations that distribute subsets of cached data via CD-ROM, and so
    883          on. HTTP systems are used in corporate intranets over high-bandwidth links, and for access via PDAs with low-power radio links
    884          and intermittent connectivity. The goal of HTTP/1.1 is to support the wide diversity of configurations already deployed while
    885          introducing protocol constructs that meet the needs of those who build web applications that require high reliability and,
    886          failing that, at least reliable indications of failure.
    887       </p>
    888       <p id="rfc.section.1.4.p.11">HTTP communication usually takes place over TCP/IP connections. The default port is TCP 80 (&lt;<a href="http://www.iana.org/assignments/port-numbers">http://www.iana.org/assignments/port-numbers</a>&gt;), but other ports can be used. This does not preclude HTTP from being implemented on top of any other protocol on the Internet,
    889          or on other networks. HTTP only presumes a reliable transport; any protocol that provides such guarantees can be used; the
    890          mapping of the HTTP/1.1 request and response structures onto the transport data units of the protocol in question is outside
    891          the scope of this specification.
    892       </p>
    893       <p id="rfc.section.1.4.p.12">In HTTP/1.0, most implementations used a new connection for each request/response exchange. In HTTP/1.1, a connection may
    894          be used for one or more request/response exchanges, although connections may be closed for a variety of reasons (see <a href="#persistent.connections" title="Persistent Connections">Section&nbsp;7.1</a>).
    895       </p>
    896       <h1 id="rfc.section.2"><a href="#rfc.section.2">2.</a>&nbsp;<a id="notation" href="#notation">Notational Conventions and Generic Grammar</a></h1>
    897       <h2 id="rfc.section.2.1"><a href="#rfc.section.2.1">2.1</a>&nbsp;<a id="notation.abnf" href="#notation.abnf">Augmented BNF</a></h2>
    898       <p id="rfc.section.2.1.p.1">All of the mechanisms specified in this document are described in both prose and an augmented Backus-Naur Form (BNF) similar
    899          to that used by <a href="#RFC822ABNF" id="rfc.xref.RFC822ABNF.1"><cite title="Standard for the format of ARPA Internet text messages">[RFC822ABNF]</cite></a>. Implementors will need to be familiar with the notation in order to understand this specification. The augmented BNF includes
    900          the following constructs:
    901       </p>
    902       <p id="rfc.section.2.1.p.2">name = definition </p>
    903       <ul class="empty">
    904          <li>The name of a rule is simply the name itself (without any enclosing "&lt;" and "&gt;") and is separated from its definition by the
    905             equal "=" character. White space is only significant in that indentation of continuation lines is used to indicate a rule
    906             definition that spans more than one line. Certain basic rules are in uppercase, such as SP, LWS, HTAB, CRLF, DIGIT, ALPHA,
    907             etc. Angle brackets are used within definitions whenever their presence will facilitate discerning the use of rule names.
    908          </li>
    909       </ul>
    910       <p id="rfc.section.2.1.p.3">"literal" </p>
    911       <ul class="empty">
    912          <li>Quotation marks surround literal text. Unless stated otherwise, the text is case-insensitive.</li>
    913       </ul>
    914       <p id="rfc.section.2.1.p.4">rule1 | rule2 </p>
    915       <ul class="empty">
    916          <li>Elements separated by a bar ("|") are alternatives, e.g., "yes | no" will accept yes or no.</li>
    917       </ul>
    918       <p id="rfc.section.2.1.p.5">(rule1 rule2) </p>
    919       <ul class="empty">
    920          <li>Elements enclosed in parentheses are treated as a single element. Thus, "(elem (foo | bar) elem)" allows the token sequences
    921             "elem foo elem" and "elem bar elem".
    922          </li>
    923       </ul>
    924       <p id="rfc.section.2.1.p.6">*rule </p>
    925       <ul class="empty">
    926          <li>The character "*" preceding an element indicates repetition. The full form is "&lt;n&gt;*&lt;m&gt;element" indicating at least &lt;n&gt; and
    927             at most &lt;m&gt; occurrences of element. Default values are 0 and infinity so that "*(element)" allows any number, including zero;
    928             "1*element" requires at least one; and "1*2element" allows one or two.
    929          </li>
    930       </ul>
    931       <p id="rfc.section.2.1.p.7">[rule] </p>
    932       <ul class="empty">
    933          <li>Square brackets enclose optional elements; "[foo bar]" is equivalent to "*1(foo bar)".</li>
    934       </ul>
    935       <p id="rfc.section.2.1.p.8">N rule </p>
    936       <ul class="empty">
    937          <li>Specific repetition: "&lt;n&gt;(element)" is equivalent to "&lt;n&gt;*&lt;n&gt;(element)"; that is, exactly &lt;n&gt; occurrences of (element). Thus
    938             2DIGIT is a 2-digit number, and 3ALPHA is a string of three alphabetic characters.
    939          </li>
    940       </ul>
    941       <p id="rfc.section.2.1.p.9">#rule </p>
    942       <ul class="empty">
    943          <li>A construct "#" is defined, similar to "*", for defining lists of elements. The full form is "&lt;n&gt;#&lt;m&gt;element" indicating at
    944             least &lt;n&gt; and at most &lt;m&gt; elements, each separated by one or more commas (",") and <em class="bcp14">OPTIONAL</em> linear white space (LWS). This makes the usual form of lists very easy; a rule such as
    945             <div id="rfc.figure.u.4"></div><pre class="text">   ( *<a href="#rule.LWS" class="smpl">LWS</a> element *( *<a href="#rule.LWS" class="smpl">LWS</a> "," *<a href="#rule.LWS" class="smpl">LWS</a> element ))</pre> </li>
    946          <li>can be shown as
    947             <div id="rfc.figure.u.5"></div><pre class="text">   1#element</pre> </li>
    948          <li>Wherever this construct is used, null elements are allowed, but do not contribute to the count of elements present. That is,
    949             "(element), , (element) " is permitted, but counts as only two elements. Therefore, where at least one element is required,
    950             at least one non-null element <em class="bcp14">MUST</em> be present. Default values are 0 and infinity so that "#element" allows any number, including zero; "1#element" requires at
    951             least one; and "1#2element" allows one or two.
    952          </li>
    953       </ul>
    954       <p id="rfc.section.2.1.p.10">; comment </p>
    955       <ul class="empty">
    956          <li>A semi-colon, set off some distance to the right of rule text, starts a comment that continues to the end of line. This is
    957             a simple way of including useful notes in parallel with the specifications.
    958          </li>
    959       </ul>
    960       <div id="implied.LWS">
    961          <p id="rfc.section.2.1.p.11"> <span id="rfc.iref.i.2"></span> implied *LWS
    962          </p>
    963          <ul class="empty">
    964             <li>The grammar described by this specification is word-based. Except where noted otherwise, linear white space (LWS) can be included
    965                between any two adjacent words (token or quoted-string), and between adjacent words and separators, without changing the interpretation
    966                of a field. At least one delimiter (LWS and/or separators) <em class="bcp14">MUST</em> exist between any two tokens (for the definition of "token" below), since they would otherwise be interpreted as a single
    967                token.
    968             </li>
    969          </ul>
     893               behavior. HTTP requirements for cache behavior and cacheable responses are defined in <a href="p6-cache.html#caching" title="Introduction">Section 1</a> of <a href="#Part6" id="rfc.xref.Part6.2"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>.
     894            </p>
     895            <p id="rfc.section.1.4.p.10">In fact, there are a wide variety of architectures and configurations of caches and proxies currently being experimented with
     896               or deployed across the World Wide Web. These systems include national hierarchies of proxy caches to save transoceanic bandwidth,
     897               systems that broadcast or multicast cache entries, organizations that distribute subsets of cached data via CD-ROM, and so
     898               on. HTTP systems are used in corporate intranets over high-bandwidth links, and for access via PDAs with low-power radio links
     899               and intermittent connectivity. The goal of HTTP/1.1 is to support the wide diversity of configurations already deployed while
     900               introducing protocol constructs that meet the needs of those who build web applications that require high reliability and,
     901               failing that, at least reliable indications of failure.
     902            </p>
     903            <p id="rfc.section.1.4.p.11">HTTP communication usually takes place over TCP/IP connections. The default port is TCP 80 (&lt;<a href="http://www.iana.org/assignments/port-numbers">http://www.iana.org/assignments/port-numbers</a>&gt;), but other ports can be used. This does not preclude HTTP from being implemented on top of any other protocol on the Internet,
     904               or on other networks. HTTP only presumes a reliable transport; any protocol that provides such guarantees can be used; the
     905               mapping of the HTTP/1.1 request and response structures onto the transport data units of the protocol in question is outside
     906               the scope of this specification.
     907            </p>
     908            <p id="rfc.section.1.4.p.12">In HTTP/1.0, most implementations used a new connection for each request/response exchange. In HTTP/1.1, a connection may
     909               be used for one or more request/response exchanges, although connections may be closed for a variety of reasons (see <a href="#persistent.connections" title="Persistent Connections">Section&nbsp;7.1</a>).
     910            </p>
     911         </div>
    970912      </div>
    971       <h2 id="rfc.section.2.2"><a href="#rfc.section.2.2">2.2</a>&nbsp;<a id="basic.rules" href="#basic.rules">Basic Rules</a></h2>
    972       <div id="core.rules">
    973          <p id="rfc.section.2.2.p.1">                    The following rules are used throughout this specification to describe basic parsing constructs. The US-ASCII coded character
    974             set is defined by ANSI X3.4-1986 <a href="#USASCII" id="rfc.xref.USASCII.1"><cite title="Coded Character Set -- 7-bit American Standard Code for Information Interchange">[USASCII]</cite></a>.
    975          </p>
    976       </div>
    977       <div id="rfc.figure.u.6"></div><pre class="inline"><span id="rfc.iref.g.2"></span><span id="rfc.iref.g.3"></span><span id="rfc.iref.g.4"></span><span id="rfc.iref.g.5"></span><span id="rfc.iref.g.6"></span><span id="rfc.iref.g.7"></span><span id="rfc.iref.g.8"></span><span id="rfc.iref.g.9"></span><span id="rfc.iref.g.10"></span><span id="rfc.iref.g.11"></span>  <a href="#core.rules" class="smpl">OCTET</a>          = %x00-FF
     913      <div id="notation">
     914         <h1 id="rfc.section.2"><a href="#rfc.section.2">2.</a>&nbsp;<a href="#notation">Notational Conventions and Generic Grammar</a></h1>
     915         <div id="notation.abnf">
     916            <h2 id="rfc.section.2.1"><a href="#rfc.section.2.1">2.1</a>&nbsp;<a href="#notation.abnf">Augmented BNF</a></h2>
     917            <p id="rfc.section.2.1.p.1">All of the mechanisms specified in this document are described in both prose and an augmented Backus-Naur Form (BNF) similar
     918               to that used by <a href="#RFC822ABNF" id="rfc.xref.RFC822ABNF.1"><cite title="Standard for the format of ARPA Internet text messages">[RFC822ABNF]</cite></a>. Implementors will need to be familiar with the notation in order to understand this specification. The augmented BNF includes
     919               the following constructs:
     920            </p>
     921            <p id="rfc.section.2.1.p.2">name = definition </p>
     922            <ul class="empty">
     923               <li>The name of a rule is simply the name itself (without any enclosing "&lt;" and "&gt;") and is separated from its definition by the
     924                  equal "=" character. White space is only significant in that indentation of continuation lines is used to indicate a rule
     925                  definition that spans more than one line. Certain basic rules are in uppercase, such as SP, LWS, HTAB, CRLF, DIGIT, ALPHA,
     926                  etc. Angle brackets are used within definitions whenever their presence will facilitate discerning the use of rule names.
     927               </li>
     928            </ul>
     929            <p id="rfc.section.2.1.p.3">"literal" </p>
     930            <ul class="empty">
     931               <li>Quotation marks surround literal text. Unless stated otherwise, the text is case-insensitive.</li>
     932            </ul>
     933            <p id="rfc.section.2.1.p.4">rule1 | rule2 </p>
     934            <ul class="empty">
     935               <li>Elements separated by a bar ("|") are alternatives, e.g., "yes | no" will accept yes or no.</li>
     936            </ul>
     937            <p id="rfc.section.2.1.p.5">(rule1 rule2) </p>
     938            <ul class="empty">
     939               <li>Elements enclosed in parentheses are treated as a single element. Thus, "(elem (foo | bar) elem)" allows the token sequences
     940                  "elem foo elem" and "elem bar elem".
     941               </li>
     942            </ul>
     943            <p id="rfc.section.2.1.p.6">*rule </p>
     944            <ul class="empty">
     945               <li>The character "*" preceding an element indicates repetition. The full form is "&lt;n&gt;*&lt;m&gt;element" indicating at least &lt;n&gt; and
     946                  at most &lt;m&gt; occurrences of element. Default values are 0 and infinity so that "*(element)" allows any number, including zero;
     947                  "1*element" requires at least one; and "1*2element" allows one or two.
     948               </li>
     949            </ul>
     950            <p id="rfc.section.2.1.p.7">[rule] </p>
     951            <ul class="empty">
     952               <li>Square brackets enclose optional elements; "[foo bar]" is equivalent to "*1(foo bar)".</li>
     953            </ul>
     954            <p id="rfc.section.2.1.p.8">N rule </p>
     955            <ul class="empty">
     956               <li>Specific repetition: "&lt;n&gt;(element)" is equivalent to "&lt;n&gt;*&lt;n&gt;(element)"; that is, exactly &lt;n&gt; occurrences of (element). Thus
     957                  2DIGIT is a 2-digit number, and 3ALPHA is a string of three alphabetic characters.
     958               </li>
     959            </ul>
     960            <p id="rfc.section.2.1.p.9">#rule </p>
     961            <ul class="empty">
     962               <li>A construct "#" is defined, similar to "*", for defining lists of elements. The full form is "&lt;n&gt;#&lt;m&gt;element" indicating at
     963                  least &lt;n&gt; and at most &lt;m&gt; elements, each separated by one or more commas (",") and <em class="bcp14">OPTIONAL</em> linear white space (LWS). This makes the usual form of lists very easy; a rule such as <span id="rfc.figure.u.4"></span><pre class="text">   ( *<a href="#rule.LWS" class="smpl">LWS</a> element *( *<a href="#rule.LWS" class="smpl">LWS</a> "," *<a href="#rule.LWS" class="smpl">LWS</a> element ))</pre> </li>
     964               <li>can be shown as <span id="rfc.figure.u.5"></span><pre class="text">   1#element</pre> </li>
     965               <li>Wherever this construct is used, null elements are allowed, but do not contribute to the count of elements present. That is,
     966                  "(element), , (element) " is permitted, but counts as only two elements. Therefore, where at least one element is required,
     967                  at least one non-null element <em class="bcp14">MUST</em> be present. Default values are 0 and infinity so that "#element" allows any number, including zero; "1#element" requires at
     968                  least one; and "1#2element" allows one or two.
     969               </li>
     970            </ul>
     971            <p id="rfc.section.2.1.p.10">; comment </p>
     972            <ul class="empty">
     973               <li>A semi-colon, set off some distance to the right of rule text, starts a comment that continues to the end of line. This is
     974                  a simple way of including useful notes in parallel with the specifications.
     975               </li>
     976            </ul>
     977            <div id="implied.LWS">
     978               <p id="rfc.section.2.1.p.11"><span id="rfc.iref.i.2"></span> implied *LWS
     979               </p>
     980               <ul class="empty">
     981                  <li>The grammar described by this specification is word-based. Except where noted otherwise, linear white space (LWS) can be included
     982                     between any two adjacent words (token or quoted-string), and between adjacent words and separators, without changing the interpretation
     983                     of a field. At least one delimiter (LWS and/or separators) <em class="bcp14">MUST</em> exist between any two tokens (for the definition of "token" below), since they would otherwise be interpreted as a single
     984                     token.
     985                  </li>
     986               </ul>
     987            </div>
     988         </div>
     989         <div id="basic.rules">
     990            <h2 id="rfc.section.2.2"><a href="#rfc.section.2.2">2.2</a>&nbsp;<a href="#basic.rules">Basic Rules</a></h2>
     991            <div id="core.rules">
     992               <p id="rfc.section.2.2.p.1">          The following rules are used throughout this specification to describe basic parsing constructs. The US-ASCII coded character
     993                  set is defined by ANSI X3.4-1986 <a href="#USASCII" id="rfc.xref.USASCII.1"><cite title="Coded Character Set -- 7-bit American Standard Code for Information Interchange">[USASCII]</cite></a>.
     994               </p>
     995            </div>
     996            <div id="rfc.figure.u.6"></div><pre class="inline"><span id="rfc.iref.g.2"></span><span id="rfc.iref.g.3"></span><span id="rfc.iref.g.4"></span><span id="rfc.iref.g.5"></span><span id="rfc.iref.g.6"></span><span id="rfc.iref.g.7"></span><span id="rfc.iref.g.8"></span><span id="rfc.iref.g.9"></span><span id="rfc.iref.g.10"></span><span id="rfc.iref.g.11"></span>  <a href="#core.rules" class="smpl">OCTET</a>          = %x00-FF
    978997                   ; any 8-bit sequence of data
    979998  <a href="#core.rules" class="smpl">CHAR</a>           = %x01-7F
     
    9961015                   ; US-ASCII double-quote mark (34)
    9971016</pre><div id="rule.CRLF">
    998          <p id="rfc.section.2.2.p.3"> HTTP/1.1 defines the sequence CR LF as the end-of-line marker for all protocol elements except the entity-body (see <a href="#tolerant.applications" title="Tolerant Applications">Appendix&nbsp;B</a> for tolerant applications). The end-of-line marker within an entity-body is defined by its associated media type, as described
    999             in <a href="p3-payload.html#media.types" title="Media Types">Section 3.3</a> of <a href="#Part3" id="rfc.xref.Part3.5"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>.
    1000          </p>
    1001       </div>
    1002       <div id="rfc.figure.u.7"></div><pre class="inline"><span id="rfc.iref.g.12"></span>  <a href="#rule.CRLF" class="smpl">CRLF</a>           = <a href="#core.rules" class="smpl">CR</a> LF
     1017               <p id="rfc.section.2.2.p.3"> HTTP/1.1 defines the sequence CR LF as the end-of-line marker for all protocol elements except the entity-body (see <a href="#tolerant.applications" title="Tolerant Applications">Appendix&nbsp;B</a> for tolerant applications). The end-of-line marker within an entity-body is defined by its associated media type, as described
     1018                  in <a href="p3-payload.html#media.types" title="Media Types">Section 3.3</a> of <a href="#Part3" id="rfc.xref.Part3.5"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>.
     1019               </p>
     1020            </div>
     1021            <div id="rfc.figure.u.7"></div><pre class="inline"><span id="rfc.iref.g.12"></span>  <a href="#rule.CRLF" class="smpl">CRLF</a>           = <a href="#core.rules" class="smpl">CR</a> LF
    10031022</pre><div id="rule.LWS">
    1004          <p id="rfc.section.2.2.p.5"> HTTP/1.1 header field values can be folded onto multiple lines if the continuation line begins with a space or horizontal
    1005             tab. All linear white space, including folding, has the same semantics as SP. A recipient <em class="bcp14">MAY</em> replace any linear white space with a single SP before interpreting the field value or forwarding the message downstream.
    1006          </p>
    1007       </div>
    1008       <div id="rfc.figure.u.8"></div><pre class="inline"><span id="rfc.iref.g.13"></span>  <a href="#rule.LWS" class="smpl">LWS</a>            = [<a href="#rule.CRLF" class="smpl">CRLF</a>] 1*( <a href="#core.rules" class="smpl">SP</a> | <a href="#core.rules" class="smpl">HTAB</a> )
     1023               <p id="rfc.section.2.2.p.5"> HTTP/1.1 header field values can be folded onto multiple lines if the continuation line begins with a space or horizontal
     1024                  tab. All linear white space, including folding, has the same semantics as SP. A recipient <em class="bcp14">MAY</em> replace any linear white space with a single SP before interpreting the field value or forwarding the message downstream.
     1025               </p>
     1026            </div>
     1027            <div id="rfc.figure.u.8"></div><pre class="inline"><span id="rfc.iref.g.13"></span>  <a href="#rule.LWS" class="smpl">LWS</a>            = [<a href="#rule.CRLF" class="smpl">CRLF</a>] 1*( <a href="#core.rules" class="smpl">SP</a> | <a href="#core.rules" class="smpl">HTAB</a> )
    10091028</pre><div id="rule.TEXT">
    1010          <p id="rfc.section.2.2.p.7"> The TEXT rule is only used for descriptive field contents and values that are not intended to be interpreted by the message
    1011             parser. Words of *TEXT <em class="bcp14">MAY</em> contain characters from character sets other than ISO-8859-1 <a href="#ISO-8859-1" id="rfc.xref.ISO-8859-1.1"><cite title="Information technology -- 8-bit single-byte coded graphic character sets -- Part 1: Latin alphabet No. 1">[ISO-8859-1]</cite></a> only when encoded according to the rules of <a href="#RFC2047" id="rfc.xref.RFC2047.1"><cite title="MIME (Multipurpose Internet Mail Extensions) Part Three: Message Header Extensions for Non-ASCII Text">[RFC2047]</cite></a>.
    1012          </p>
    1013       </div>
    1014       <div id="rfc.figure.u.9"></div><pre class="inline"><span id="rfc.iref.g.14"></span>  <a href="#rule.TEXT" class="smpl">TEXT</a>           = %x20-7E | %x80-FF | <a href="#rule.LWS" class="smpl">LWS</a>
     1029               <p id="rfc.section.2.2.p.7"> The TEXT rule is only used for descriptive field contents and values that are not intended to be interpreted by the message
     1030                  parser. Words of *TEXT <em class="bcp14">MAY</em> contain characters from character sets other than ISO-8859-1 <a href="#ISO-8859-1" id="rfc.xref.ISO-8859-1.1"><cite title="Information technology -- 8-bit single-byte coded graphic character sets -- Part 1: Latin alphabet No. 1">[ISO-8859-1]</cite></a> only when encoded according to the rules of <a href="#RFC2047" id="rfc.xref.RFC2047.1"><cite title="MIME (Multipurpose Internet Mail Extensions) Part Three: Message Header Extensions for Non-ASCII Text">[RFC2047]</cite></a>.
     1031               </p>
     1032            </div>
     1033            <div id="rfc.figure.u.9"></div><pre class="inline"><span id="rfc.iref.g.14"></span>  <a href="#rule.TEXT" class="smpl">TEXT</a>           = %x20-7E | %x80-FF | <a href="#rule.LWS" class="smpl">LWS</a>
    10151034                 ; any <a href="#core.rules" class="smpl">OCTET</a> except <a href="#core.rules" class="smpl">CTL</a>s, but including <a href="#rule.LWS" class="smpl">LWS</a>
    10161035</pre><p id="rfc.section.2.2.p.9">A CRLF is allowed in the definition of TEXT only as part of a header field continuation. It is expected that the folding LWS
    1017          will be replaced with a single SP before interpretation of the TEXT value.
    1018       </p>
    1019       <div id="rule.HEX">
    1020          <p id="rfc.section.2.2.p.10"> Hexadecimal numeric characters are used in several protocol elements.</p>
    1021       </div>
    1022       <div id="rfc.figure.u.10"></div><pre class="inline"><span id="rfc.iref.g.15"></span>  <a href="#rule.HEX" class="smpl">HEX</a>            = "A" | "B" | "C" | "D" | "E" | "F"
     1036               will be replaced with a single SP before interpretation of the TEXT value.
     1037            </p>
     1038            <div id="rule.HEX">
     1039               <p id="rfc.section.2.2.p.10"> Hexadecimal numeric characters are used in several protocol elements.</p>
     1040            </div>
     1041            <div id="rfc.figure.u.10"></div><pre class="inline"><span id="rfc.iref.g.15"></span>  <a href="#rule.HEX" class="smpl">HEX</a>            = "A" | "B" | "C" | "D" | "E" | "F"
    10231042                 | "a" | "b" | "c" | "d" | "e" | "f" | <a href="#core.rules" class="smpl">DIGIT</a>
    10241043</pre><div id="rule.token.separators">
    1025          <p id="rfc.section.2.2.p.12">      Many HTTP/1.1 header field values consist of words separated by LWS or special characters. These special characters <em class="bcp14">MUST</em> be in a quoted string to be used within a parameter value (as defined in <a href="#transfer.codings" title="Transfer Codings">Section&nbsp;3.4</a>).
    1026          </p>
    1027       </div>
    1028       <div id="rfc.figure.u.11"></div><pre class="inline"><span id="rfc.iref.g.16"></span><span id="rfc.iref.g.17"></span><span id="rfc.iref.g.18"></span>  <a href="#rule.token.separators" class="smpl">separators</a>     = "(" | ")" | "&lt;" | "&gt;" | "@"
     1044               <p id="rfc.section.2.2.p.12">   Many HTTP/1.1 header field values consist of words separated by LWS or special characters. These special characters <em class="bcp14">MUST</em> be in a quoted string to be used within a parameter value (as defined in <a href="#transfer.codings" title="Transfer Codings">Section&nbsp;3.4</a>).
     1045               </p>
     1046            </div>
     1047            <div id="rfc.figure.u.11"></div><pre class="inline"><span id="rfc.iref.g.16"></span><span id="rfc.iref.g.17"></span><span id="rfc.iref.g.18"></span>  <a href="#rule.token.separators" class="smpl">separators</a>     = "(" | ")" | "&lt;" | "&gt;" | "@"
    10291048                 | "," | ";" | ":" | "\" | <a href="#core.rules" class="smpl">DQUOTE</a>
    10301049                 | "/" | "[" | "]" | "?" | "="
     
    10381057  <a href="#rule.token.separators" class="smpl">token</a>          = 1*<a href="#rule.token.separators" class="smpl">tchar</a>
    10391058</pre><div id="rule.comment">
    1040          <p id="rfc.section.2.2.p.14">    Comments can be included in some HTTP header fields by surrounding the comment text with parentheses. Comments are only allowed
    1041             in fields containing "comment" as part of their field value definition. In all other fields, parentheses are considered part
    1042             of the field value.
    1043          </p>
    1044       </div>
    1045       <div id="rfc.figure.u.12"></div><pre class="inline"><span id="rfc.iref.g.19"></span><span id="rfc.iref.g.20"></span>  <a href="#rule.comment" class="smpl">comment</a>        = "(" *( <a href="#rule.comment" class="smpl">ctext</a> | <a href="#rule.quoted-pair" class="smpl">quoted-pair</a> | <a href="#rule.comment" class="smpl">comment</a> ) ")"
     1059               <p id="rfc.section.2.2.p.14">  Comments can be included in some HTTP header fields by surrounding the comment text with parentheses. Comments are only allowed
     1060                  in fields containing "comment" as part of their field value definition. In all other fields, parentheses are considered part
     1061                  of the field value.
     1062               </p>
     1063            </div>
     1064            <div id="rfc.figure.u.12"></div><pre class="inline"><span id="rfc.iref.g.19"></span><span id="rfc.iref.g.20"></span>  <a href="#rule.comment" class="smpl">comment</a>        = "(" *( <a href="#rule.comment" class="smpl">ctext</a> | <a href="#rule.quoted-pair" class="smpl">quoted-pair</a> | <a href="#rule.comment" class="smpl">comment</a> ) ")"
    10461065  <a href="#rule.comment" class="smpl">ctext</a>          = &lt;any <a href="#rule.TEXT" class="smpl">TEXT</a> excluding "(" and ")"&gt;
    10471066</pre><div id="rule.quoted-string">
    1048          <p id="rfc.section.2.2.p.16">    A string of text is parsed as a single word if it is quoted using double-quote marks.</p>
    1049       </div>
    1050       <div id="rfc.figure.u.13"></div><pre class="inline"><span id="rfc.iref.g.21"></span><span id="rfc.iref.g.22"></span>  <a href="#rule.quoted-string" class="smpl">quoted-string</a>  = ( <a href="#core.rules" class="smpl">DQUOTE</a> *(<a href="#rule.quoted-string" class="smpl">qdtext</a> | <a href="#rule.quoted-pair" class="smpl">quoted-pair</a> ) <a href="#core.rules" class="smpl">DQUOTE</a> )
     1067               <p id="rfc.section.2.2.p.16">  A string of text is parsed as a single word if it is quoted using double-quote marks.</p>
     1068            </div>
     1069            <div id="rfc.figure.u.13"></div><pre class="inline"><span id="rfc.iref.g.21"></span><span id="rfc.iref.g.22"></span>  <a href="#rule.quoted-string" class="smpl">quoted-string</a>  = ( <a href="#core.rules" class="smpl">DQUOTE</a> *(<a href="#rule.quoted-string" class="smpl">qdtext</a> | <a href="#rule.quoted-pair" class="smpl">quoted-pair</a> ) <a href="#core.rules" class="smpl">DQUOTE</a> )
    10511070  <a href="#rule.quoted-string" class="smpl">qdtext</a>         = &lt;any <a href="#rule.TEXT" class="smpl">TEXT</a> excluding <a href="#core.rules" class="smpl">DQUOTE</a> and "\"&gt;
    10521071</pre><div id="rule.quoted-pair">
    1053          <p id="rfc.section.2.2.p.18">    The backslash character ("\") <em class="bcp14">MAY</em> be used as a single-character quoting mechanism only within quoted-string and comment constructs.
    1054          </p>
    1055       </div>
    1056       <div id="rfc.figure.u.14"></div><pre class="inline"><span id="rfc.iref.g.23"></span><span id="rfc.iref.g.24"></span>  <a href="#rule.quoted-pair" class="smpl">quoted-text</a>    = %x01-09 |
     1072               <p id="rfc.section.2.2.p.18">  The backslash character ("\") <em class="bcp14">MAY</em> be used as a single-character quoting mechanism only within quoted-string and comment constructs.
     1073               </p>
     1074            </div>
     1075            <div id="rfc.figure.u.14"></div><pre class="inline"><span id="rfc.iref.g.23"></span><span id="rfc.iref.g.24"></span>  <a href="#rule.quoted-pair" class="smpl">quoted-text</a>    = %x01-09 |
    10571076                   %x0B-0C |
    10581077                   %x0E-FF ; Characters excluding NUL, <a href="#core.rules" class="smpl">CR</a> and <a href="#core.rules" class="smpl">LF</a>
    10591078  <a href="#rule.quoted-pair" class="smpl">quoted-pair</a>    = "\" <a href="#rule.quoted-pair" class="smpl">quoted-text</a>
    1060 </pre><h2 id="rfc.section.2.3"><a href="#rfc.section.2.3">2.3</a>&nbsp;<a id="abnf.dependencies" href="#abnf.dependencies">ABNF Rules defined in other Parts of the Specification</a></h2>
    1061       <p id="rfc.section.2.3.p.1">The ABNF rules below are defined in other parts:</p>
    1062       <div id="rfc.figure.u.15"></div><pre class="inline">  <a href="#abnf.dependencies" class="smpl">request-header</a>  = &lt;request-header, defined in <a href="#Part2" id="rfc.xref.Part2.1"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>, <a href="p2-semantics.html#request.header.fields" title="Request Header Fields">Section 4</a>&gt;
     1079</pre></div>
     1080         <div id="abnf.dependencies">
     1081            <h2 id="rfc.section.2.3"><a href="#rfc.section.2.3">2.3</a>&nbsp;<a href="#abnf.dependencies">ABNF Rules defined in other Parts of the Specification</a></h2>
     1082            <p id="rfc.section.2.3.p.1">The ABNF rules below are defined in other parts:</p>
     1083            <div id="rfc.figure.u.15"></div><pre class="inline">  <a href="#abnf.dependencies" class="smpl">request-header</a>  = &lt;request-header, defined in <a href="#Part2" id="rfc.xref.Part2.1"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>, <a href="p2-semantics.html#request.header.fields" title="Request Header Fields">Section 4</a>&gt;
    10631084  <a href="#abnf.dependencies" class="smpl">response-header</a> = &lt;response-header, defined in <a href="#Part2" id="rfc.xref.Part2.2"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>, <a href="p2-semantics.html#response.header.fields" title="Response Header Fields">Section 6</a>&gt;
    10641085</pre><div id="rfc.figure.u.16"></div><pre class="inline">  <a href="#abnf.dependencies" class="smpl">accept-params</a>   = &lt;accept-params, defined in <a href="#Part3" id="rfc.xref.Part3.6"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>, <a href="p3-payload.html#header.accept" title="Accept">Section 6.1</a>&gt;
     
    10681089  <a href="#abnf.dependencies" class="smpl">Pragma</a>          = &lt;Pragma, defined in <a href="#Part6" id="rfc.xref.Part6.4"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>, <a href="p6-cache.html#header.pragma" title="Pragma">Section 16.4</a>&gt;
    10691090  <a href="#abnf.dependencies" class="smpl">Warning</a>         = &lt;Warning, defined in <a href="#Part6" id="rfc.xref.Part6.5"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>, <a href="p6-cache.html#header.warning" title="Warning">Section 16.6</a>&gt;
    1070 </pre><h1 id="rfc.section.3"><a href="#rfc.section.3">3.</a>&nbsp;<a id="protocol.parameters" href="#protocol.parameters">Protocol Parameters</a></h1>
    1071       <h2 id="rfc.section.3.1"><a href="#rfc.section.3.1">3.1</a>&nbsp;<a id="http.version" href="#http.version">HTTP Version</a></h2>
    1072       <p id="rfc.section.3.1.p.1">HTTP uses a "&lt;major&gt;.&lt;minor&gt;" numbering scheme to indicate versions of the protocol. The protocol versioning policy is intended
    1073          to allow the sender to indicate the format of a message and its capacity for understanding further HTTP communication, rather
    1074          than the features obtained via that communication. No change is made to the version number for the addition of message components
    1075          which do not affect communication behavior or which only add to extensible field values. The &lt;minor&gt; number is incremented
    1076          when the changes made to the protocol add features which do not change the general message parsing algorithm, but which may
    1077          add to the message semantics and imply additional capabilities of the sender. The &lt;major&gt; number is incremented when the format
    1078          of a message within the protocol is changed. See <a href="#RFC2145" id="rfc.xref.RFC2145.1"><cite title="Use and Interpretation of HTTP Version Numbers">[RFC2145]</cite></a> for a fuller explanation.
    1079       </p>
    1080       <p id="rfc.section.3.1.p.2">The version of an HTTP message is indicated by an HTTP-Version field in the first line of the message. HTTP-Version is case-sensitive.</p>
    1081       <div id="rfc.figure.u.18"></div><pre class="inline"><span id="rfc.iref.g.25"></span><span id="rfc.iref.g.26"></span>  <a href="#http.version" class="smpl">HTTP-Version</a>   = <a href="#http.version" class="smpl">HTTP-Prot-Name</a> "/" 1*<a href="#core.rules" class="smpl">DIGIT</a> "." 1*<a href="#core.rules" class="smpl">DIGIT</a>
     1091</pre></div>
     1092      </div>
     1093      <div id="protocol.parameters">
     1094         <h1 id="rfc.section.3"><a href="#rfc.section.3">3.</a>&nbsp;<a href="#protocol.parameters">Protocol Parameters</a></h1>
     1095         <div id="http.version">
     1096            <h2 id="rfc.section.3.1"><a href="#rfc.section.3.1">3.1</a>&nbsp;<a href="#http.version">HTTP Version</a></h2>
     1097            <p id="rfc.section.3.1.p.1">HTTP uses a "&lt;major&gt;.&lt;minor&gt;" numbering scheme to indicate versions of the protocol. The protocol versioning policy is intended
     1098               to allow the sender to indicate the format of a message and its capacity for understanding further HTTP communication, rather
     1099               than the features obtained via that communication. No change is made to the version number for the addition of message components
     1100               which do not affect communication behavior or which only add to extensible field values. The &lt;minor&gt; number is incremented
     1101               when the changes made to the protocol add features which do not change the general message parsing algorithm, but which may
     1102               add to the message semantics and imply additional capabilities of the sender. The &lt;major&gt; number is incremented when the format
     1103               of a message within the protocol is changed. See <a href="#RFC2145" id="rfc.xref.RFC2145.1"><cite title="Use and Interpretation of HTTP Version Numbers">[RFC2145]</cite></a> for a fuller explanation.
     1104            </p>
     1105            <p id="rfc.section.3.1.p.2">The version of an HTTP message is indicated by an HTTP-Version field in the first line of the message. HTTP-Version is case-sensitive.</p>
     1106            <div id="rfc.figure.u.18"></div><pre class="inline"><span id="rfc.iref.g.25"></span><span id="rfc.iref.g.26"></span>  <a href="#http.version" class="smpl">HTTP-Version</a>   = <a href="#http.version" class="smpl">HTTP-Prot-Name</a> "/" 1*<a href="#core.rules" class="smpl">DIGIT</a> "." 1*<a href="#core.rules" class="smpl">DIGIT</a>
    10821107  <a href="#http.version" class="smpl">HTTP-Prot-Name</a> = %x48.54.54.50 ; "HTTP", case-sensitive
    10831108</pre><p id="rfc.section.3.1.p.4">Note that the major and minor numbers <em class="bcp14">MUST</em> be treated as separate integers and that each <em class="bcp14">MAY</em> be incremented higher than a single digit. Thus, HTTP/2.4 is a lower version than HTTP/2.13, which in turn is lower than HTTP/12.3.
    1084          Leading zeros <em class="bcp14">MUST</em> be ignored by recipients and <em class="bcp14">MUST NOT</em> be sent.
    1085       </p>
    1086       <p id="rfc.section.3.1.p.5">An application that sends a request or response message that includes HTTP-Version of "HTTP/1.1" <em class="bcp14">MUST</em> be at least conditionally compliant with this specification. Applications that are at least conditionally compliant with this
    1087          specification <em class="bcp14">SHOULD</em> use an HTTP-Version of "HTTP/1.1" in their messages, and <em class="bcp14">MUST</em> do so for any message that is not compatible with HTTP/1.0. For more details on when to send specific HTTP-Version values,
    1088          see <a href="#RFC2145" id="rfc.xref.RFC2145.2"><cite title="Use and Interpretation of HTTP Version Numbers">[RFC2145]</cite></a>.
    1089       </p>
    1090       <p id="rfc.section.3.1.p.6">The HTTP version of an application is the highest HTTP version for which the application is at least conditionally compliant.</p>
    1091       <p id="rfc.section.3.1.p.7">Proxy and gateway applications need to be careful when forwarding messages in protocol versions different from that of the
    1092          application. Since the protocol version indicates the protocol capability of the sender, a proxy/gateway <em class="bcp14">MUST NOT</em> send a message with a version indicator which is greater than its actual version. If a higher version request is received,
    1093          the proxy/gateway <em class="bcp14">MUST</em> either downgrade the request version, or respond with an error, or switch to tunnel behavior.
    1094       </p>
    1095       <p id="rfc.section.3.1.p.8">Due to interoperability problems with HTTP/1.0 proxies discovered since the publication of <a href="#RFC2068" id="rfc.xref.RFC2068.1"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2068]</cite></a>, caching proxies <em class="bcp14">MUST</em>, gateways <em class="bcp14">MAY</em>, and tunnels <em class="bcp14">MUST NOT</em> upgrade the request to the highest version they support. The proxy/gateway's response to that request <em class="bcp14">MUST</em> be in the same major version as the request.
    1096       </p>
    1097       <p id="rfc.section.3.1.p.9"> </p>
    1098       <ul class="empty">
    1099          <li> <b>Note:</b> Converting between versions of HTTP may involve modification of header fields required or forbidden by the versions involved.
    1100          </li>
    1101       </ul>
    1102       <h2 id="rfc.section.3.2"><a href="#rfc.section.3.2">3.2</a>&nbsp;<a id="uri" href="#uri">Uniform Resource Identifiers</a></h2>
    1103       <p id="rfc.section.3.2.p.1">URIs have been known by many names: WWW addresses, Universal Document Identifiers, Universal Resource Identifiers <a href="#RFC1630" id="rfc.xref.RFC1630.2"><cite title="Universal Resource Identifiers in WWW: A Unifying Syntax for the Expression of Names and Addresses of Objects on the Network as used in the World-Wide Web">[RFC1630]</cite></a>, and finally the combination of Uniform Resource Locators (URL) <a href="#RFC1738" id="rfc.xref.RFC1738.2"><cite title="Uniform Resource Locators (URL)">[RFC1738]</cite></a> and Names (URN) <a href="#RFC1737" id="rfc.xref.RFC1737.2"><cite title="Functional Requirements for Uniform Resource Names">[RFC1737]</cite></a>. As far as HTTP is concerned, Uniform Resource Identifiers are simply formatted strings which identify--via name, location,
    1104          or any other characteristic--a resource.
    1105       </p>
    1106       <h3 id="rfc.section.3.2.1"><a href="#rfc.section.3.2.1">3.2.1</a>&nbsp;<a id="general.syntax" href="#general.syntax">General Syntax</a></h3>
    1107       <p id="rfc.section.3.2.1.p.1">URIs in HTTP can be represented in absolute form or relative to some known base URI <a href="#RFC1808" id="rfc.xref.RFC1808.1"><cite title="Relative Uniform Resource Locators">[RFC1808]</cite></a>, depending upon the context of their use. The two forms are differentiated by the fact that absolute URIs always begin with
    1108          a scheme name followed by a colon. For definitive information on URL syntax and semantics, see "Uniform Resource Identifiers
    1109          (URI): Generic Syntax and Semantics," <a href="#RFC2396" id="rfc.xref.RFC2396.1"><cite title="Uniform Resource Identifiers (URI): Generic Syntax">[RFC2396]</cite></a> (which replaces <a href="#RFC1738" id="rfc.xref.RFC1738.3"><cite title="Uniform Resource Locators (URL)">[RFC1738]</cite></a> and <a href="#RFC1808" id="rfc.xref.RFC1808.2"><cite title="Relative Uniform Resource Locators">[RFC1808]</cite></a>). This specification adopts the definitions of "URI-reference", "absoluteURI", "fragment", "relativeURI", "port", "host",
    1110          "abs_path", "query", and "authority" from that specification:
    1111       </p>
    1112       <div id="rfc.figure.u.19"></div><pre class="inline"><span id="rfc.iref.g.27"></span><span id="rfc.iref.g.28"></span><span id="rfc.iref.g.29"></span><span id="rfc.iref.g.30"></span><span id="rfc.iref.g.31"></span><span id="rfc.iref.g.32"></span><span id="rfc.iref.g.33"></span>  <a href="#general.syntax" class="smpl">absoluteURI</a>   = &lt;absoluteURI, defined in <a href="#RFC2396" id="rfc.xref.RFC2396.2"><cite title="Uniform Resource Identifiers (URI): Generic Syntax">[RFC2396]</cite></a>, <a href="http://tools.ietf.org/html/rfc2396#section-3">Section 3</a>&gt;
    1113   <a href="#general.syntax" class="smpl">authority</a>     = &lt;authority, defined in <a href="#RFC2396" id="rfc.xref.RFC2396.3"><cite title="Uniform Resource Identifiers (URI): Generic Syntax">[RFC2396]</cite></a>, <a href="http://tools.ietf.org/html/rfc2396#section-3.2">Section 3.2</a>&gt;
    1114   <a href="#general.syntax" class="smpl">fragment</a>      = &lt;fragment, defined in <a href="#RFC2396" id="rfc.xref.RFC2396.4"><cite title="Uniform Resource Identifiers (URI): Generic Syntax">[RFC2396]</cite></a>, <a href="http://tools.ietf.org/html/rfc2396#section-4.1">Section 4.1</a>&gt;
    1115   <a href="#general.syntax" class="smpl">path-absolute</a> = &lt;abs_path, defined in <a href="#RFC2396" id="rfc.xref.RFC2396.5"><cite title="Uniform Resource Identifiers (URI): Generic Syntax">[RFC2396]</cite></a>, <a href="http://tools.ietf.org/html/rfc2396#section-3">Section 3</a>&gt;
    1116   <a href="#general.syntax" class="smpl">port</a>          = &lt;port, defined in <a href="#RFC2396" id="rfc.xref.RFC2396.6"><cite title="Uniform Resource Identifiers (URI): Generic Syntax">[RFC2396]</cite></a>, <a href="http://tools.ietf.org/html/rfc2396#section-3.2.2">Section 3.2.2</a>&gt;
    1117   <a href="#general.syntax" class="smpl">query</a>         = &lt;query, defined in <a href="#RFC2396" id="rfc.xref.RFC2396.7"><cite title="Uniform Resource Identifiers (URI): Generic Syntax">[RFC2396]</cite></a>, <a href="http://tools.ietf.org/html/rfc2396#section-3.4">Section 3.4</a>&gt;
    1118   <a href="#general.syntax" class="smpl">relativeURI</a>   = &lt;relativeURI, defined in <a href="#RFC2396" id="rfc.xref.RFC2396.8"><cite title="Uniform Resource Identifiers (URI): Generic Syntax">[RFC2396]</cite></a>, <a href="http://tools.ietf.org/html/rfc2396#section-5">Section 5</a>&gt;
    1119   <a href="#general.syntax" class="smpl">uri-host</a>      = &lt;host, defined in <a href="#RFC2396" id="rfc.xref.RFC2396.9"><cite title="Uniform Resource Identifiers (URI): Generic Syntax">[RFC2396]</cite></a>, <a href="http://tools.ietf.org/html/rfc2396#section-3.2.2">Section 3.2.2</a>&gt;
     1109               Leading zeros <em class="bcp14">MUST</em> be ignored by recipients and <em class="bcp14">MUST NOT</em> be sent.
     1110            </p>
     1111            <p id="rfc.section.3.1.p.5">An application that sends a request or response message that includes HTTP-Version of "HTTP/1.1" <em class="bcp14">MUST</em> be at least conditionally compliant with this specification. Applications that are at least conditionally compliant with this
     1112               specification <em class="bcp14">SHOULD</em> use an HTTP-Version of "HTTP/1.1" in their messages, and <em class="bcp14">MUST</em> do so for any message that is not compatible with HTTP/1.0. For more details on when to send specific HTTP-Version values,
     1113               see <a href="#RFC2145" id="rfc.xref.RFC2145.2"><cite title="Use and Interpretation of HTTP Version Numbers">[RFC2145]</cite></a>.
     1114            </p>
     1115            <p id="rfc.section.3.1.p.6">The HTTP version of an application is the highest HTTP version for which the application is at least conditionally compliant.</p>
     1116            <p id="rfc.section.3.1.p.7">Proxy and gateway applications need to be careful when forwarding messages in protocol versions different from that of the
     1117               application. Since the protocol version indicates the protocol capability of the sender, a proxy/gateway <em class="bcp14">MUST NOT</em> send a message with a version indicator which is greater than its actual version. If a higher version request is received,
     1118               the proxy/gateway <em class="bcp14">MUST</em> either downgrade the request version, or respond with an error, or switch to tunnel behavior.
     1119            </p>
     1120            <p id="rfc.section.3.1.p.8">Due to interoperability problems with HTTP/1.0 proxies discovered since the publication of <a href="#RFC2068" id="rfc.xref.RFC2068.1"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2068]</cite></a>, caching proxies <em class="bcp14">MUST</em>, gateways <em class="bcp14">MAY</em>, and tunnels <em class="bcp14">MUST NOT</em> upgrade the request to the highest version they support. The proxy/gateway's response to that request <em class="bcp14">MUST</em> be in the same major version as the request.
     1121            </p>
     1122            <p id="rfc.section.3.1.p.9"></p>
     1123            <ul class="empty">
     1124               <li><b>Note:</b> Converting between versions of HTTP may involve modification of header fields required or forbidden by the versions involved.
     1125               </li>
     1126            </ul>
     1127         </div>
     1128         <div id="uri">
     1129            <h2 id="rfc.section.3.2"><a href="#rfc.section.3.2">3.2</a>&nbsp;<a href="#uri">Uniform Resource Identifiers</a></h2>
     1130            <p id="rfc.section.3.2.p.1">URIs have been known by many names: WWW addresses, Universal Document Identifiers, Universal Resource Identifiers <a href="#RFC1630" id="rfc.xref.RFC1630.2"><cite title="Universal Resource Identifiers in WWW: A Unifying Syntax for the Expression of Names and Addresses of Objects on the Network as used in the World-Wide Web">[RFC1630]</cite></a>, and finally the combination of Uniform Resource Locators (URL) <a href="#RFC1738" id="rfc.xref.RFC1738.2"><cite title="Uniform Resource Locators (URL)">[RFC1738]</cite></a> and Names (URN) <a href="#RFC1737" id="rfc.xref.RFC1737.2"><cite title="Functional Requirements for Uniform Resource Names">[RFC1737]</cite></a>. As far as HTTP is concerned, Uniform Resource Identifiers are simply formatted strings which identify--via name, location,
     1131               or any other characteristic--a resource.
     1132            </p>
     1133            <div id="general.syntax">
     1134               <h3 id="rfc.section.3.2.1"><a href="#rfc.section.3.2.1">3.2.1</a>&nbsp;<a href="#general.syntax">General Syntax</a></h3>
     1135               <p id="rfc.section.3.2.1.p.1">URIs in HTTP can be represented in absolute form or relative to some known base URI <a href="#RFC1808" id="rfc.xref.RFC1808.1"><cite title="Relative Uniform Resource Locators">[RFC1808]</cite></a>, depending upon the context of their use. The two forms are differentiated by the fact that absolute URIs always begin with
     1136                  a scheme name followed by a colon. For definitive information on URL syntax and semantics, see "Uniform Resource Identifiers
     1137                  (URI): Generic Syntax and Semantics," <a href="#RFC2396" id="rfc.xref.RFC2396.1"><cite title="Uniform Resource Identifiers (URI): Generic Syntax">[RFC2396]</cite></a> (which replaces <a href="#RFC1738" id="rfc.xref.RFC1738.3"><cite title="Uniform Resource Locators (URL)">[RFC1738]</cite></a> and <a href="#RFC1808" id="rfc.xref.RFC1808.2"><cite title="Relative Uniform Resource Locators">[RFC1808]</cite></a>). This specification adopts the definitions of "URI-reference", "absoluteURI", "fragment", "relativeURI", "port", "host",
     1138                  "abs_path", "query", and "authority" from that specification:
     1139               </p>
     1140               <div id="rfc.figure.u.19"></div><pre class="inline"><span id="rfc.iref.g.27"></span><span id="rfc.iref.g.28"></span><span id="rfc.iref.g.29"></span><span id="rfc.iref.g.30"></span><span id="rfc.iref.g.31"></span><span id="rfc.iref.g.32"></span><span id="rfc.iref.g.33"></span>  <a href="#general.syntax" class="smpl">absoluteURI</a>   = &lt;absoluteURI, defined in <a href="#RFC2396" id="rfc.xref.RFC2396.2"><cite title="Uniform Resource Identifiers (URI): Generic Syntax">[RFC2396]</cite></a>, <a href="https://tools.ietf.org/html/rfc2396#section-3">Section 3</a>&gt;
     1141  <a href="#general.syntax" class="smpl">authority</a>     = &lt;authority, defined in <a href="#RFC2396" id="rfc.xref.RFC2396.3"><cite title="Uniform Resource Identifiers (URI): Generic Syntax">[RFC2396]</cite></a>, <a href="https://tools.ietf.org/html/rfc2396#section-3.2">Section 3.2</a>&gt;
     1142  <a href="#general.syntax" class="smpl">fragment</a>      = &lt;fragment, defined in <a href="#RFC2396" id="rfc.xref.RFC2396.4"><cite title="Uniform Resource Identifiers (URI): Generic Syntax">[RFC2396]</cite></a>, <a href="https://tools.ietf.org/html/rfc2396#section-4.1">Section 4.1</a>&gt;
     1143  <a href="#general.syntax" class="smpl">path-absolute</a> = &lt;abs_path, defined in <a href="#RFC2396" id="rfc.xref.RFC2396.5"><cite title="Uniform Resource Identifiers (URI): Generic Syntax">[RFC2396]</cite></a>, <a href="https://tools.ietf.org/html/rfc2396#section-3">Section 3</a>&gt;
     1144  <a href="#general.syntax" class="smpl">port</a>          = &lt;port, defined in <a href="#RFC2396" id="rfc.xref.RFC2396.6"><cite title="Uniform Resource Identifiers (URI): Generic Syntax">[RFC2396]</cite></a>, <a href="https://tools.ietf.org/html/rfc2396#section-3.2.2">Section 3.2.2</a>&gt;
     1145  <a href="#general.syntax" class="smpl">query</a>         = &lt;query, defined in <a href="#RFC2396" id="rfc.xref.RFC2396.7"><cite title="Uniform Resource Identifiers (URI): Generic Syntax">[RFC2396]</cite></a>, <a href="https://tools.ietf.org/html/rfc2396#section-3.4">Section 3.4</a>&gt;
     1146  <a href="#general.syntax" class="smpl">relativeURI</a>   = &lt;relativeURI, defined in <a href="#RFC2396" id="rfc.xref.RFC2396.8"><cite title="Uniform Resource Identifiers (URI): Generic Syntax">[RFC2396]</cite></a>, <a href="https://tools.ietf.org/html/rfc2396#section-5">Section 5</a>&gt;
     1147  <a href="#general.syntax" class="smpl">uri-host</a>      = &lt;host, defined in <a href="#RFC2396" id="rfc.xref.RFC2396.9"><cite title="Uniform Resource Identifiers (URI): Generic Syntax">[RFC2396]</cite></a>, <a href="https://tools.ietf.org/html/rfc2396#section-3.2.2">Section 3.2.2</a>&gt;
    11201148</pre><p id="rfc.section.3.2.1.p.3">HTTP does not place any a priori limit on the length of a URI. Servers <em class="bcp14">MUST</em> be able to handle the URI of any resource they serve, and <em class="bcp14">SHOULD</em> be able to handle URIs of unbounded length if they provide GET-based forms that could generate such URIs. A server <em class="bcp14">SHOULD</em> return 414 (Request-URI Too Long) status if a URI is longer than the server can handle (see <a href="p2-semantics.html#status.414" title="414 Request-URI Too Long">Section 9.4.15</a> of <a href="#Part2" id="rfc.xref.Part2.3"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>).
    1121       </p>
    1122       <p id="rfc.section.3.2.1.p.4"> </p>
    1123       <ul class="empty">
    1124          <li> <b>Note:</b> Servers ought to be cautious about depending on URI lengths above 255 bytes, because some older client or proxy implementations
    1125             might not properly support these lengths.
    1126          </li>
    1127       </ul>
    1128       <h3 id="rfc.section.3.2.2"><a href="#rfc.section.3.2.2">3.2.2</a>&nbsp;<a id="http.url" href="#http.url">http URL</a></h3>
    1129       <p id="rfc.section.3.2.2.p.1">The "http" scheme is used to locate network resources via the HTTP protocol. This section defines the scheme-specific syntax
    1130          and semantics for http URLs.
    1131       </p>
    1132       <div id="rfc.figure.u.20"></div><pre class="inline"><span id="rfc.iref.g.34"></span>  <a href="#http.url" class="smpl">http-URL</a> = "http:" "//" <a href="#general.syntax" class="smpl">uri-host</a> [ ":" <a href="#general.syntax" class="smpl">port</a> ]
     1149               </p>
     1150               <p id="rfc.section.3.2.1.p.4"></p>
     1151               <ul class="empty">
     1152                  <li><b>Note:</b> Servers ought to be cautious about depending on URI lengths above 255 bytes, because some older client or proxy implementations
     1153                     might not properly support these lengths.
     1154                  </li>
     1155               </ul>
     1156            </div>
     1157            <div id="http.url">
     1158               <h3 id="rfc.section.3.2.2"><a href="#rfc.section.3.2.2">3.2.2</a>&nbsp;<a href="#http.url">http URL</a></h3>
     1159               <p id="rfc.section.3.2.2.p.1">The "http" scheme is used to locate network resources via the HTTP protocol. This section defines the scheme-specific syntax
     1160                  and semantics for http URLs.
     1161               </p>
     1162               <div id="rfc.figure.u.20"></div><pre class="inline"><span id="rfc.iref.g.34"></span>  <a href="#http.url" class="smpl">http-URL</a> = "http:" "//" <a href="#general.syntax" class="smpl">uri-host</a> [ ":" <a href="#general.syntax" class="smpl">port</a> ]
    11331163             [ <a href="#general.syntax" class="smpl">path-absolute</a> [ "?" <a href="#general.syntax" class="smpl">query</a> ]]
    11341164</pre><p id="rfc.section.3.2.2.p.3">If the port is empty or not given, port 80 is assumed. The semantics are that the identified resource is located at the server
    1135          listening for TCP connections on that port of that host, and the Request-URI for the resource is path-absolute (<a href="#request-uri" title="Request-URI">Section&nbsp;5.1.2</a>). The use of IP addresses in URLs <em class="bcp14">SHOULD</em> be avoided whenever possible (see <a href="#RFC1900" id="rfc.xref.RFC1900.1"><cite title="Renumbering Needs Work">[RFC1900]</cite></a>). If the path-absolute is not present in the URL, it <em class="bcp14">MUST</em> be given as "/" when used as a Request-URI for a resource (<a href="#request-uri" title="Request-URI">Section&nbsp;5.1.2</a>). If a proxy receives a host name which is not a fully qualified domain name, it <em class="bcp14">MAY</em> add its domain to the host name it received. If a proxy receives a fully qualified domain name, the proxy <em class="bcp14">MUST NOT</em> change the host name.
    1136       </p>
    1137       <h3 id="rfc.section.3.2.3"><a href="#rfc.section.3.2.3">3.2.3</a>&nbsp;<a id="uri.comparison" href="#uri.comparison">URI Comparison</a></h3>
    1138       <p id="rfc.section.3.2.3.p.1">When comparing two URIs to decide if they match or not, a client <em class="bcp14">SHOULD</em> use a case-sensitive octet-by-octet comparison of the entire URIs, with these exceptions:
    1139       </p>
    1140       <ul>
    1141          <li>A port that is empty or not given is equivalent to the default port for that URI-reference;</li>
    1142          <li>Comparisons of host names <em class="bcp14">MUST</em> be case-insensitive;
    1143          </li>
    1144          <li>Comparisons of scheme names <em class="bcp14">MUST</em> be case-insensitive;
    1145          </li>
    1146          <li>An empty path-absolute is equivalent to an path-absolute of "/".</li>
    1147       </ul>
    1148       <p id="rfc.section.3.2.3.p.2">Characters other than those in the "reserved" set (see <a href="#RFC2396" id="rfc.xref.RFC2396.10"><cite title="Uniform Resource Identifiers (URI): Generic Syntax">[RFC2396]</cite></a>) are equivalent to their ""%" HEX HEX" encoding.
    1149       </p>
    1150       <p id="rfc.section.3.2.3.p.3">For example, the following three URIs are equivalent:</p>
    1151       <div id="rfc.figure.u.21"></div><pre class="text">   http://example.com:80/~smith/home.html
     1165                  listening for TCP connections on that port of that host, and the Request-URI for the resource is path-absolute (<a href="#request-uri" title="Request-URI">Section&nbsp;5.1.2</a>). The use of IP addresses in URLs <em class="bcp14">SHOULD</em> be avoided whenever possible (see <a href="#RFC1900" id="rfc.xref.RFC1900.1"><cite title="Renumbering Needs Work">[RFC1900]</cite></a>). If the path-absolute is not present in the URL, it <em class="bcp14">MUST</em> be given as "/" when used as a Request-URI for a resource (<a href="#request-uri" title="Request-URI">Section&nbsp;5.1.2</a>). If a proxy receives a host name which is not a fully qualified domain name, it <em class="bcp14">MAY</em> add its domain to the host name it received. If a proxy receives a fully qualified domain name, the proxy <em class="bcp14">MUST NOT</em> change the host name.
     1166               </p>
     1167            </div>
     1168            <div id="uri.comparison">
     1169               <h3 id="rfc.section.3.2.3"><a href="#rfc.section.3.2.3">3.2.3</a>&nbsp;<a href="#uri.comparison">URI Comparison</a></h3>
     1170               <p id="rfc.section.3.2.3.p.1">When comparing two URIs to decide if they match or not, a client <em class="bcp14">SHOULD</em> use a case-sensitive octet-by-octet comparison of the entire URIs, with these exceptions:
     1171               </p>
     1172               <ul>
     1173                  <li>A port that is empty or not given is equivalent to the default port for that URI-reference;</li>
     1174                  <li>Comparisons of host names <em class="bcp14">MUST</em> be case-insensitive;
     1175                  </li>
     1176                  <li>Comparisons of scheme names <em class="bcp14">MUST</em> be case-insensitive;
     1177                  </li>
     1178                  <li>An empty path-absolute is equivalent to an path-absolute of "/".</li>
     1179               </ul>
     1180               <p id="rfc.section.3.2.3.p.2">Characters other than those in the "reserved" set (see <a href="#RFC2396" id="rfc.xref.RFC2396.10"><cite title="Uniform Resource Identifiers (URI): Generic Syntax">[RFC2396]</cite></a>) are equivalent to their ""%" HEX HEX" encoding.
     1181               </p>
     1182               <p id="rfc.section.3.2.3.p.3">For example, the following three URIs are equivalent:</p>
     1183               <div id="rfc.figure.u.21"></div><pre class="text">   http://example.com:80/~smith/home.html
    11521184   http://EXAMPLE.com/%7Esmith/home.html
    11531185   http://EXAMPLE.com:/%7esmith/home.html
    1154 </pre><h2 id="rfc.section.3.3"><a href="#rfc.section.3.3">3.3</a>&nbsp;<a id="date.time.formats" href="#date.time.formats">Date/Time Formats</a></h2>
    1155       <h3 id="rfc.section.3.3.1"><a href="#rfc.section.3.3.1">3.3.1</a>&nbsp;<a id="full.date" href="#full.date">Full Date</a></h3>
    1156       <p id="rfc.section.3.3.1.p.1">HTTP applications have historically allowed three different formats for the representation of date/time stamps:</p>
    1157       <div id="rfc.figure.u.22"></div><pre class="text">   Sun, 06 Nov 1994 08:49:37 GMT  ; RFC 822, updated by RFC 1123
     1186</pre></div>
     1187         </div>
     1188         <div id="date.time.formats">
     1189            <h2 id="rfc.section.3.3"><a href="#rfc.section.3.3">3.3</a>&nbsp;<a href="#date.time.formats">Date/Time Formats</a></h2>
     1190            <div id="full.date">
     1191               <h3 id="rfc.section.3.3.1"><a href="#rfc.section.3.3.1">3.3.1</a>&nbsp;<a href="#full.date">Full Date</a></h3>
     1192               <p id="rfc.section.3.3.1.p.1">HTTP applications have historically allowed three different formats for the representation of date/time stamps:</p>
     1193               <div id="rfc.figure.u.22"></div><pre class="text">   Sun, 06 Nov 1994 08:49:37 GMT  ; RFC 822, updated by RFC 1123
    11581194   Sunday, 06-Nov-94 08:49:37 GMT ; obsolete RFC 850 format
    11591195   Sun Nov  6 08:49:37 1994       ; ANSI C's asctime() format
    11601196</pre><p id="rfc.section.3.3.1.p.3">The first format is preferred as an Internet standard and represents a fixed-length subset of that defined by <a href="#RFC1123" id="rfc.xref.RFC1123.1"><cite title="Requirements for Internet Hosts - Application and Support">[RFC1123]</cite></a> (an update to <a href="#RFC822" id="rfc.xref.RFC822.1"><cite title="Standard for the format of ARPA Internet text messages">[RFC822]</cite></a>). The other formats are described here only for compatibility with obsolete implementations. HTTP/1.1 clients and servers
    1161          that parse the date value <em class="bcp14">MUST</em> accept all three formats (for compatibility with HTTP/1.0), though they <em class="bcp14">MUST</em> only generate the RFC 1123 format for representing HTTP-date values in header fields. See <a href="#tolerant.applications" title="Tolerant Applications">Appendix&nbsp;B</a> for further information.
    1162       </p>
    1163       <ul class="empty">
    1164          <li> <b>Note:</b> Recipients of date values are encouraged to be robust in accepting date values that may have been sent by non-HTTP applications,
    1165             as is sometimes the case when retrieving or posting messages via proxies/gateways to SMTP or NNTP.
    1166          </li>
    1167       </ul>
    1168       <p id="rfc.section.3.3.1.p.5">All HTTP date/time stamps <em class="bcp14">MUST</em> be represented in Greenwich Mean Time (GMT), without exception. For the purposes of HTTP, GMT is exactly equal to UTC (Coordinated
    1169          Universal Time). This is indicated in the first two formats by the inclusion of "GMT" as the three-letter abbreviation for
    1170          time zone, and <em class="bcp14">MUST</em> be assumed when reading the asctime format. HTTP-date is case sensitive and <em class="bcp14">MUST NOT</em> include additional LWS beyond that specifically included as SP in the grammar.
    1171       </p>
    1172       <div id="rfc.figure.u.23"></div><pre class="inline"><span id="rfc.iref.g.35"></span><span id="rfc.iref.g.36"></span><span id="rfc.iref.g.37"></span><span id="rfc.iref.g.38"></span><span id="rfc.iref.g.39"></span><span id="rfc.iref.g.40"></span><span id="rfc.iref.g.41"></span><span id="rfc.iref.g.42"></span><span id="rfc.iref.g.43"></span><span id="rfc.iref.g.44"></span><span id="rfc.iref.g.45"></span><span id="rfc.iref.g.46"></span>  <a href="#full.date" class="smpl">HTTP-date</a>    = <a href="#full.date" class="smpl">rfc1123-date</a> | <a href="#full.date" class="smpl">obsolete-date</a>
     1197                  that parse the date value <em class="bcp14">MUST</em> accept all three formats (for compatibility with HTTP/1.0), though they <em class="bcp14">MUST</em> only generate the RFC 1123 format for representing HTTP-date values in header fields. See <a href="#tolerant.applications" title="Tolerant Applications">Appendix&nbsp;B</a> for further information.
     1198               </p>
     1199               <ul class="empty">
     1200                  <li><b>Note:</b> Recipients of date values are encouraged to be robust in accepting date values that may have been sent by non-HTTP applications,
     1201                     as is sometimes the case when retrieving or posting messages via proxies/gateways to SMTP or NNTP.
     1202                  </li>
     1203               </ul>
     1204               <p id="rfc.section.3.3.1.p.5">All HTTP date/time stamps <em class="bcp14">MUST</em> be represented in Greenwich Mean Time (GMT), without exception. For the purposes of HTTP, GMT is exactly equal to UTC (Coordinated
     1205                  Universal Time). This is indicated in the first two formats by the inclusion of "GMT" as the three-letter abbreviation for
     1206                  time zone, and <em class="bcp14">MUST</em> be assumed when reading the asctime format. HTTP-date is case sensitive and <em class="bcp14">MUST NOT</em> include additional LWS beyond that specifically included as SP in the grammar.
     1207               </p>
     1208               <div id="rfc.figure.u.23"></div><pre class="inline"><span id="rfc.iref.g.35"></span><span id="rfc.iref.g.36"></span><span id="rfc.iref.g.37"></span><span id="rfc.iref.g.38"></span><span id="rfc.iref.g.39"></span><span id="rfc.iref.g.40"></span><span id="rfc.iref.g.41"></span><span id="rfc.iref.g.42"></span><span id="rfc.iref.g.43"></span><span id="rfc.iref.g.44"></span><span id="rfc.iref.g.45"></span><span id="rfc.iref.g.46"></span>  <a href="#full.date" class="smpl">HTTP-date</a>    = <a href="#full.date" class="smpl">rfc1123-date</a> | <a href="#full.date" class="smpl">obsolete-date</a>
    11731209  <a href="#full.date" class="smpl">obsolete-date</a> = <a href="#full.date" class="smpl">rfc850-date</a> | <a href="#full.date" class="smpl">asctime-date</a>
    11741210  <a href="#full.date" class="smpl">rfc1123-date</a> = <a href="#full.date" class="smpl">wkday</a> "," <a href="#core.rules" class="smpl">SP</a> date1 <a href="#core.rules" class="smpl">SP</a> time <a href="#core.rules" class="smpl">SP</a> "GMT"
     
    11901226               | "May" | "Jun" | "Jul" | "Aug"
    11911227               | "Sep" | "Oct" | "Nov" | "Dec"
    1192 </pre><p id="rfc.section.3.3.1.p.7"> <b>Note:</b> HTTP requirements for the date/time stamp format apply only to their usage within the protocol stream. Clients and servers
    1193          are not required to use these formats for user presentation, request logging, etc.
    1194       </p>
    1195       <h2 id="rfc.section.3.4"><a href="#rfc.section.3.4">3.4</a>&nbsp;<a id="transfer.codings" href="#transfer.codings">Transfer Codings</a></h2>
    1196       <p id="rfc.section.3.4.p.1">Transfer-coding values are used to indicate an encoding transformation that has been, can be, or may need to be applied to
    1197          an entity-body in order to ensure "safe transport" through the network. This differs from a content coding in that the transfer-coding
    1198          is a property of the message, not of the original entity.
    1199       </p>
    1200       <div id="rfc.figure.u.24"></div><pre class="inline"><span id="rfc.iref.g.47"></span><span id="rfc.iref.g.48"></span>  <a href="#transfer.codings" class="smpl">transfer-coding</a>         = "chunked" | <a href="#transfer.codings" class="smpl">transfer-extension</a>
     1228</pre><p id="rfc.section.3.3.1.p.7"><b>Note:</b> HTTP requirements for the date/time stamp format apply only to their usage within the protocol stream. Clients and servers
     1229                  are not required to use these formats for user presentation, request logging, etc.
     1230               </p>
     1231            </div>
     1232         </div>
     1233         <div id="transfer.codings">
     1234            <h2 id="rfc.section.3.4"><a href="#rfc.section.3.4">3.4</a>&nbsp;<a href="#transfer.codings">Transfer Codings</a></h2>
     1235            <p id="rfc.section.3.4.p.1">Transfer-coding values are used to indicate an encoding transformation that has been, can be, or may need to be applied to
     1236               an entity-body in order to ensure "safe transport" through the network. This differs from a content coding in that the transfer-coding
     1237               is a property of the message, not of the original entity.
     1238            </p>
     1239            <div id="rfc.figure.u.24"></div><pre class="inline"><span id="rfc.iref.g.47"></span><span id="rfc.iref.g.48"></span>  <a href="#transfer.codings" class="smpl">transfer-coding</a>         = "chunked" | <a href="#transfer.codings" class="smpl">transfer-extension</a>
    12011240  <a href="#transfer.codings" class="smpl">transfer-extension</a>      = <a href="#rule.token.separators" class="smpl">token</a> *( ";" <a href="#transfer.codings" class="smpl">parameter</a> )
    12021241</pre><div id="rule.parameter">
    1203          <p id="rfc.section.3.4.p.3">      Parameters are in the form of attribute/value pairs.</p>
    1204       </div>
    1205       <div id="rfc.figure.u.25"></div><pre class="inline"><span id="rfc.iref.g.49"></span><span id="rfc.iref.g.50"></span><span id="rfc.iref.g.51"></span>  <a href="#transfer.codings" class="smpl">parameter</a>               = <a href="#rule.parameter" class="smpl">attribute</a> "=" <a href="#rule.parameter" class="smpl">value</a>
     1242               <p id="rfc.section.3.4.p.3">   Parameters are in the form of attribute/value pairs.</p>
     1243            </div>
     1244            <div id="rfc.figure.u.25"></div><pre class="inline"><span id="rfc.iref.g.49"></span><span id="rfc.iref.g.50"></span><span id="rfc.iref.g.51"></span>  <a href="#transfer.codings" class="smpl">parameter</a>               = <a href="#rule.parameter" class="smpl">attribute</a> "=" <a href="#rule.parameter" class="smpl">value</a>
    12061245  <a href="#rule.parameter" class="smpl">attribute</a>               = <a href="#rule.token.separators" class="smpl">token</a>
    12071246  <a href="#rule.parameter" class="smpl">value</a>                   = <a href="#rule.token.separators" class="smpl">token</a> | <a href="#rule.quoted-string" class="smpl">quoted-string</a>
    12081247</pre><p id="rfc.section.3.4.p.5">All transfer-coding values are case-insensitive. HTTP/1.1 uses transfer-coding values in the TE header field (<a href="#header.te" id="rfc.xref.header.te.1" title="TE">Section&nbsp;8.5</a>) and in the Transfer-Encoding header field (<a href="#header.transfer-encoding" id="rfc.xref.header.transfer-encoding.1" title="Transfer-Encoding">Section&nbsp;8.7</a>).
    1209       </p>
    1210       <p id="rfc.section.3.4.p.6">Whenever a transfer-coding is applied to a message-body, the set of transfer-codings <em class="bcp14">MUST</em> include "chunked", unless the message is terminated by closing the connection. When the "chunked" transfer-coding is used,
    1211          it <em class="bcp14">MUST</em> be the last transfer-coding applied to the message-body. The "chunked" transfer-coding <em class="bcp14">MUST NOT</em> be applied more than once to a message-body. These rules allow the recipient to determine the transfer-length of the message
    1212          (<a href="#message.length" title="Message Length">Section&nbsp;4.4</a>).
    1213       </p>
    1214       <p id="rfc.section.3.4.p.7">Transfer-codings are analogous to the Content-Transfer-Encoding values of MIME <a href="#RFC2045" id="rfc.xref.RFC2045.2"><cite title="Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies">[RFC2045]</cite></a>, which were designed to enable safe transport of binary data over a 7-bit transport service. However, safe transport has
    1215          a different focus for an 8bit-clean transfer protocol. In HTTP, the only unsafe characteristic of message-bodies is the difficulty
    1216          in determining the exact body length (<a href="#message.length" title="Message Length">Section&nbsp;4.4</a>), or the desire to encrypt data over a shared transport.
    1217       </p>
    1218       <p id="rfc.section.3.4.p.8">The Internet Assigned Numbers Authority (IANA) acts as a registry for transfer-coding value tokens. Initially, the registry
    1219          contains the following tokens: "chunked" (<a href="#chunked.transfer.encoding" title="Chunked Transfer Coding">Section&nbsp;3.4.1</a>), "gzip", "compress", and "deflate" (<a href="p3-payload.html#content.codings" title="Content Codings">Section 3.2</a> of <a href="#Part3" id="rfc.xref.Part3.9"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>).
    1220       </p>
    1221       <p id="rfc.section.3.4.p.9">New transfer-coding value tokens <em class="bcp14">SHOULD</em> be registered in the same way as new content-coding value tokens (<a href="p3-payload.html#content.codings" title="Content Codings">Section 3.2</a> of <a href="#Part3" id="rfc.xref.Part3.10"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>).
    1222       </p>
    1223       <p id="rfc.section.3.4.p.10">A server which receives an entity-body with a transfer-coding it does not understand <em class="bcp14">SHOULD</em> return 501 (Not Implemented), and close the connection. A server <em class="bcp14">MUST NOT</em> send transfer-codings to an HTTP/1.0 client.
    1224       </p>
    1225       <h3 id="rfc.section.3.4.1"><a href="#rfc.section.3.4.1">3.4.1</a>&nbsp;<a id="chunked.transfer.encoding" href="#chunked.transfer.encoding">Chunked Transfer Coding</a></h3>
    1226       <p id="rfc.section.3.4.1.p.1">The chunked encoding modifies the body of a message in order to transfer it as a series of chunks, each with its own size
    1227          indicator, followed by an <em class="bcp14">OPTIONAL</em> trailer containing entity-header fields. This allows dynamically produced content to be transferred along with the information
    1228          necessary for the recipient to verify that it has received the full message.
    1229       </p>
    1230       <div id="rfc.figure.u.26"></div><pre class="inline"><span id="rfc.iref.g.52"></span><span id="rfc.iref.g.53"></span><span id="rfc.iref.g.54"></span><span id="rfc.iref.g.55"></span><span id="rfc.iref.g.56"></span><span id="rfc.iref.g.57"></span><span id="rfc.iref.g.58"></span><span id="rfc.iref.g.59"></span><span id="rfc.iref.g.60"></span>  <a href="#chunked.transfer.encoding" class="smpl">Chunked-Body</a>   = *<a href="#chunked.transfer.encoding" class="smpl">chunk</a>
     1248            </p>
     1249            <p id="rfc.section.3.4.p.6">Whenever a transfer-coding is applied to a message-body, the set of transfer-codings <em class="bcp14">MUST</em> include "chunked", unless the message is terminated by closing the connection. When the "chunked" transfer-coding is used,
     1250               it <em class="bcp14">MUST</em> be the last transfer-coding applied to the message-body. The "chunked" transfer-coding <em class="bcp14">MUST NOT</em> be applied more than once to a message-body. These rules allow the recipient to determine the transfer-length of the message
     1251               (<a href="#message.length" title="Message Length">Section&nbsp;4.4</a>).
     1252            </p>
     1253            <p id="rfc.section.3.4.p.7">Transfer-codings are analogous to the Content-Transfer-Encoding values of MIME <a href="#RFC2045" id="rfc.xref.RFC2045.2"><cite title="Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies">[RFC2045]</cite></a>, which were designed to enable safe transport of binary data over a 7-bit transport service. However, safe transport has
     1254               a different focus for an 8bit-clean transfer protocol. In HTTP, the only unsafe characteristic of message-bodies is the difficulty
     1255               in determining the exact body length (<a href="#message.length" title="Message Length">Section&nbsp;4.4</a>), or the desire to encrypt data over a shared transport.
     1256            </p>
     1257            <p id="rfc.section.3.4.p.8">The Internet Assigned Numbers Authority (IANA) acts as a registry for transfer-coding value tokens. Initially, the registry
     1258               contains the following tokens: "chunked" (<a href="#chunked.transfer.encoding" title="Chunked Transfer Coding">Section&nbsp;3.4.1</a>), "gzip", "compress", and "deflate" (<a href="p3-payload.html#content.codings" title="Content Codings">Section 3.2</a> of <a href="#Part3" id="rfc.xref.Part3.9"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>).
     1259            </p>
     1260            <p id="rfc.section.3.4.p.9">New transfer-coding value tokens <em class="bcp14">SHOULD</em> be registered in the same way as new content-coding value tokens (<a href="p3-payload.html#content.codings" title="Content Codings">Section 3.2</a> of <a href="#Part3" id="rfc.xref.Part3.10"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>).
     1261            </p>
     1262            <p id="rfc.section.3.4.p.10">A server which receives an entity-body with a transfer-coding it does not understand <em class="bcp14">SHOULD</em> return 501 (Not Implemented), and close the connection. A server <em class="bcp14">MUST NOT</em> send transfer-codings to an HTTP/1.0 client.
     1263            </p>
     1264            <div id="chunked.transfer.encoding">
     1265               <h3 id="rfc.section.3.4.1"><a href="#rfc.section.3.4.1">3.4.1</a>&nbsp;<a href="#chunked.transfer.encoding">Chunked Transfer Coding</a></h3>
     1266               <p id="rfc.section.3.4.1.p.1">The chunked encoding modifies the body of a message in order to transfer it as a series of chunks, each with its own size
     1267                  indicator, followed by an <em class="bcp14">OPTIONAL</em> trailer containing entity-header fields. This allows dynamically produced content to be transferred along with the information
     1268                  necessary for the recipient to verify that it has received the full message.
     1269               </p>
     1270               <div id="rfc.figure.u.26"></div><pre class="inline"><span id="rfc.iref.g.52"></span><span id="rfc.iref.g.53"></span><span id="rfc.iref.g.54"></span><span id="rfc.iref.g.55"></span><span id="rfc.iref.g.56"></span><span id="rfc.iref.g.57"></span><span id="rfc.iref.g.58"></span><span id="rfc.iref.g.59"></span><span id="rfc.iref.g.60"></span>  <a href="#chunked.transfer.encoding" class="smpl">Chunked-Body</a>   = *<a href="#chunked.transfer.encoding" class="smpl">chunk</a>
    12311271                   <a href="#chunked.transfer.encoding" class="smpl">last-chunk</a>
    12321272                   <a href="#chunked.transfer.encoding" class="smpl">trailer-part</a>
     
    12441284  <a href="#chunked.transfer.encoding" class="smpl">trailer-part</a>   = *(<a href="#abnf.dependencies" class="smpl">entity-header</a> <a href="#rule.CRLF" class="smpl">CRLF</a>)
    12451285</pre><p id="rfc.section.3.4.1.p.3">The chunk-size field is a string of hex digits indicating the size of the chunk-data in octets. The chunked encoding is ended
    1246          by any chunk whose size is zero, followed by the trailer, which is terminated by an empty line.
    1247       </p>
    1248       <p id="rfc.section.3.4.1.p.4">The trailer allows the sender to include additional HTTP header fields at the end of the message. The Trailer header field
    1249          can be used to indicate which header fields are included in a trailer (see <a href="#header.trailer" id="rfc.xref.header.trailer.1" title="Trailer">Section&nbsp;8.6</a>).
    1250       </p>
    1251       <p id="rfc.section.3.4.1.p.5">A server using chunked transfer-coding in a response <em class="bcp14">MUST NOT</em> use the trailer for any header fields unless at least one of the following is true:
    1252       </p>
    1253       <ol>
    1254          <li>the request included a TE header field that indicates "trailers" is acceptable in the transfer-coding of the response, as
    1255             described in <a href="#header.te" id="rfc.xref.header.te.2" title="TE">Section&nbsp;8.5</a>; or,
    1256          </li>
    1257          <li>the server is the origin server for the response, the trailer fields consist entirely of optional metadata, and the recipient
    1258             could use the message (in a manner acceptable to the origin server) without receiving this metadata. In other words, the origin
    1259             server is willing to accept the possibility that the trailer fields might be silently discarded along the path to the client.
    1260          </li>
    1261       </ol>
    1262       <p id="rfc.section.3.4.1.p.6">This requirement prevents an interoperability failure when the message is being received by an HTTP/1.1 (or later) proxy and
    1263          forwarded to an HTTP/1.0 recipient. It avoids a situation where compliance with the protocol would have necessitated a possibly
    1264          infinite buffer on the proxy.
    1265       </p>
    1266       <p id="rfc.section.3.4.1.p.7">A process for decoding the "chunked" transfer-coding can be represented in pseudo-code as:</p>
    1267       <div id="rfc.figure.u.27"></div><pre class="text">    length := 0
     1286                  by any chunk whose size is zero, followed by the trailer, which is terminated by an empty line.
     1287               </p>
     1288               <p id="rfc.section.3.4.1.p.4">The trailer allows the sender to include additional HTTP header fields at the end of the message. The Trailer header field
     1289                  can be used to indicate which header fields are included in a trailer (see <a href="#header.trailer" id="rfc.xref.header.trailer.1" title="Trailer">Section&nbsp;8.6</a>).
     1290               </p>
     1291               <p id="rfc.section.3.4.1.p.5">A server using chunked transfer-coding in a response <em class="bcp14">MUST NOT</em> use the trailer for any header fields unless at least one of the following is true:
     1292               </p>
     1293               <ol>
     1294                  <li>the request included a TE header field that indicates "trailers" is acceptable in the transfer-coding of the response, as
     1295                     described in <a href="#header.te" id="rfc.xref.header.te.2" title="TE">Section&nbsp;8.5</a>; or,
     1296                  </li>
     1297                  <li>the server is the origin server for the response, the trailer fields consist entirely of optional metadata, and the recipient
     1298                     could use the message (in a manner acceptable to the origin server) without receiving this metadata. In other words, the origin
     1299                     server is willing to accept the possibility that the trailer fields might be silently discarded along the path to the client.
     1300                  </li>
     1301               </ol>
     1302               <p id="rfc.section.3.4.1.p.6">This requirement prevents an interoperability failure when the message is being received by an HTTP/1.1 (or later) proxy and
     1303                  forwarded to an HTTP/1.0 recipient. It avoids a situation where compliance with the protocol would have necessitated a possibly
     1304                  infinite buffer on the proxy.
     1305               </p>
     1306               <p id="rfc.section.3.4.1.p.7">A process for decoding the "chunked" transfer-coding can be represented in pseudo-code as:</p>
     1307               <div id="rfc.figure.u.27"></div><pre class="text">    length := 0
    12681308    read chunk-size, chunk-extension (if any) and CRLF
    12691309    while (chunk-size &gt; 0) {
     
    12811321    Remove "chunked" from Transfer-Encoding
    12821322</pre><p id="rfc.section.3.4.1.p.9">All HTTP/1.1 applications <em class="bcp14">MUST</em> be able to receive and decode the "chunked" transfer-coding, and <em class="bcp14">MUST</em> ignore chunk-extension extensions they do not understand.
    1283       </p>
    1284       <h2 id="rfc.section.3.5"><a href="#rfc.section.3.5">3.5</a>&nbsp;<a id="product.tokens" href="#product.tokens">Product Tokens</a></h2>
    1285       <p id="rfc.section.3.5.p.1">Product tokens are used to allow communicating applications to identify themselves by software name and version. Most fields
    1286          using product tokens also allow sub-products which form a significant part of the application to be listed, separated by white
    1287          space. By convention, the products are listed in order of their significance for identifying the application.
    1288       </p>
    1289       <div id="rfc.figure.u.28"></div><pre class="inline"><span id="rfc.iref.g.61"></span><span id="rfc.iref.g.62"></span>  <a href="#product.tokens" class="smpl">product</a>         = <a href="#rule.token.separators" class="smpl">token</a> ["/" <a href="#product.tokens" class="smpl">product-version</a>]
     1323               </p>
     1324            </div>
     1325         </div>
     1326         <div id="product.tokens">
     1327            <h2 id="rfc.section.3.5"><a href="#rfc.section.3.5">3.5</a>&nbsp;<a href="#product.tokens">Product Tokens</a></h2>
     1328            <p id="rfc.section.3.5.p.1">Product tokens are used to allow communicating applications to identify themselves by software name and version. Most fields
     1329               using product tokens also allow sub-products which form a significant part of the application to be listed, separated by white
     1330               space. By convention, the products are listed in order of their significance for identifying the application.
     1331            </p>
     1332            <div id="rfc.figure.u.28"></div><pre class="inline"><span id="rfc.iref.g.61"></span><span id="rfc.iref.g.62"></span>  <a href="#product.tokens" class="smpl">product</a>         = <a href="#rule.token.separators" class="smpl">token</a> ["/" <a href="#product.tokens" class="smpl">product-version</a>]
    12901333  <a href="#product.tokens" class="smpl">product-version</a> = <a href="#rule.token.separators" class="smpl">token</a>
    12911334</pre><p id="rfc.section.3.5.p.3">Examples:</p>
    1292       <div id="rfc.figure.u.29"></div><pre class="text">    User-Agent: CERN-LineMode/2.15 libwww/2.17b3
     1335            <div id="rfc.figure.u.29"></div><pre class="text">    User-Agent: CERN-LineMode/2.15 libwww/2.17b3
    12931336    Server: Apache/0.8.4
    12941337</pre><p id="rfc.section.3.5.p.5">Product tokens <em class="bcp14">SHOULD</em> be short and to the point. They <em class="bcp14">MUST NOT</em> be used for advertising or other non-essential information. Although any token character <em class="bcp14">MAY</em> appear in a product-version, this token <em class="bcp14">SHOULD</em> only be used for a version identifier (i.e., successive versions of the same product <em class="bcp14">SHOULD</em> only differ in the product-version portion of the product value).
    1295       </p>
    1296       <h1 id="rfc.section.4"><a href="#rfc.section.4">4.</a>&nbsp;<a id="http.message" href="#http.message">HTTP Message</a></h1>
    1297       <h2 id="rfc.section.4.1"><a href="#rfc.section.4.1">4.1</a>&nbsp;<a id="message.types" href="#message.types">Message Types</a></h2>
    1298       <p id="rfc.section.4.1.p.1">HTTP messages consist of requests from client to server and responses from server to client.</p>
    1299       <div id="rfc.figure.u.30"></div><pre class="inline"><span id="rfc.iref.g.63"></span>  <a href="#message.types" class="smpl">HTTP-message</a>   = <a href="#request" class="smpl">Request</a> | <a href="#response" class="smpl">Response</a>     ; HTTP/1.1 messages
     1338            </p>
     1339         </div>
     1340      </div>
     1341      <div id="http.message">
     1342         <h1 id="rfc.section.4"><a href="#rfc.section.4">4.</a>&nbsp;<a href="#http.message">HTTP Message</a></h1>
     1343         <div id="message.types">
     1344            <h2 id="rfc.section.4.1"><a href="#rfc.section.4.1">4.1</a>&nbsp;<a href="#message.types">Message Types</a></h2>
     1345            <p id="rfc.section.4.1.p.1">HTTP messages consist of requests from client to server and responses from server to client.</p>
     1346            <div id="rfc.figure.u.30"></div><pre class="inline"><span id="rfc.iref.g.63"></span>  <a href="#message.types" class="smpl">HTTP-message</a>   = <a href="#request" class="smpl">Request</a> | <a href="#response" class="smpl">Response</a>     ; HTTP/1.1 messages
    13001347</pre><p id="rfc.section.4.1.p.3">Request (<a href="#request" title="Request">Section&nbsp;5</a>) and Response (<a href="#response" title="Response">Section&nbsp;6</a>) messages use the generic message format of <a href="#RFC2822" id="rfc.xref.RFC2822.2"><cite title="Internet Message Format">[RFC2822]</cite></a> for transferring entities (the payload of the message). Both types of message consist of a start-line, zero or more header
    1301          fields (also known as "headers"), an empty line (i.e., a line with nothing preceding the CRLF) indicating the end of the header
    1302          fields, and possibly a message-body.
    1303       </p>
    1304       <div id="rfc.figure.u.31"></div><pre class="inline"><span id="rfc.iref.g.64"></span><span id="rfc.iref.g.65"></span>  <a href="#message.types" class="smpl">generic-message</a> = <a href="#message.types" class="smpl">start-line</a>
     1348               fields (also known as "headers"), an empty line (i.e., a line with nothing preceding the CRLF) indicating the end of the header
     1349               fields, and possibly a message-body.
     1350            </p>
     1351            <div id="rfc.figure.u.31"></div><pre class="inline"><span id="rfc.iref.g.64"></span><span id="rfc.iref.g.65"></span>  <a href="#message.types" class="smpl">generic-message</a> = <a href="#message.types" class="smpl">start-line</a>
    13051352                    *(<a href="#message.headers" class="smpl">message-header</a> <a href="#rule.CRLF" class="smpl">CRLF</a>)
    13061353                    <a href="#rule.CRLF" class="smpl">CRLF</a>
     
    13081355  <a href="#message.types" class="smpl">start-line</a>      = <a href="#request-line" class="smpl">Request-Line</a> | <a href="#status-line" class="smpl">Status-Line</a>
    13091356</pre><p id="rfc.section.4.1.p.5">In the interest of robustness, servers <em class="bcp14">SHOULD</em> ignore any empty line(s) received where a Request-Line is expected. In other words, if the server is reading the protocol
    1310          stream at the beginning of a message and receives a CRLF first, it should ignore the CRLF.
    1311       </p>
    1312       <p id="rfc.section.4.1.p.6">Certain buggy HTTP/1.0 client implementations generate extra CRLF's after a POST request. To restate what is explicitly forbidden
    1313          by the BNF, an HTTP/1.1 client <em class="bcp14">MUST NOT</em> preface or follow a request with an extra CRLF.
    1314       </p>
    1315       <h2 id="rfc.section.4.2"><a href="#rfc.section.4.2">4.2</a>&nbsp;<a id="message.headers" href="#message.headers">Message Headers</a></h2>
    1316       <p id="rfc.section.4.2.p.1">HTTP header fields, which include general-header (<a href="#general.header.fields" title="General Header Fields">Section&nbsp;4.5</a>), request-header (<a href="p2-semantics.html#request.header.fields" title="Request Header Fields">Section 4</a> of <a href="#Part2" id="rfc.xref.Part2.4"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>), response-header (<a href="p2-semantics.html#response.header.fields" title="Response Header Fields">Section 6</a> of <a href="#Part2" id="rfc.xref.Part2.5"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>), and entity-header (<a href="p3-payload.html#entity.header.fields" title="Entity Header Fields">Section 4.1</a> of <a href="#Part3" id="rfc.xref.Part3.11"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>) fields, follow the same generic format as that given in <a href="http://tools.ietf.org/html/rfc2822#section-2.1">Section 2.1</a> of <a href="#RFC2822" id="rfc.xref.RFC2822.3"><cite title="Internet Message Format">[RFC2822]</cite></a>. Each header field consists of a name followed by a colon (":") and the field value. Field names are case-insensitive. The
    1317          field value <em class="bcp14">MAY</em> be preceded by any amount of LWS, though a single SP is preferred. Header fields can be extended over multiple lines by preceding
    1318          each extra line with at least one SP or HTAB. Applications ought to follow "common form", where one is known or indicated,
    1319          when generating HTTP constructs, since there might exist some implementations that fail to accept anything beyond the common
    1320          forms.
    1321       </p>
    1322       <div id="rfc.figure.u.32"></div><pre class="inline"><span id="rfc.iref.g.66"></span><span id="rfc.iref.g.67"></span><span id="rfc.iref.g.68"></span><span id="rfc.iref.g.69"></span>  <a href="#message.headers" class="smpl">message-header</a> = <a href="#message.headers" class="smpl">field-name</a> ":" [ <a href="#message.headers" class="smpl">field-value</a> ]
     1357               stream at the beginning of a message and receives a CRLF first, it should ignore the CRLF.
     1358            </p>
     1359            <p id="rfc.section.4.1.p.6">Certain buggy HTTP/1.0 client implementations generate extra CRLF's after a POST request. To restate what is explicitly forbidden
     1360               by the BNF, an HTTP/1.1 client <em class="bcp14">MUST NOT</em> preface or follow a request with an extra CRLF.
     1361            </p>
     1362         </div>
     1363         <div id="message.headers">
     1364            <h2 id="rfc.section.4.2"><a href="#rfc.section.4.2">4.2</a>&nbsp;<a href="#message.headers">Message Headers</a></h2>
     1365            <p id="rfc.section.4.2.p.1">HTTP header fields, which include general-header (<a href="#general.header.fields" title="General Header Fields">Section&nbsp;4.5</a>), request-header (<a href="p2-semantics.html#request.header.fields" title="Request Header Fields">Section 4</a> of <a href="#Part2" id="rfc.xref.Part2.4"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>), response-header (<a href="p2-semantics.html#response.header.fields" title="Response Header Fields">Section 6</a> of <a href="#Part2" id="rfc.xref.Part2.5"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>), and entity-header (<a href="p3-payload.html#entity.header.fields" title="Entity Header Fields">Section 4.1</a> of <a href="#Part3" id="rfc.xref.Part3.11"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>) fields, follow the same generic format as that given in <a href="https://tools.ietf.org/html/rfc2822#section-2.1">Section 2.1</a> of <a href="#RFC2822" id="rfc.xref.RFC2822.3"><cite title="Internet Message Format">[RFC2822]</cite></a>. Each header field consists of a name followed by a colon (":") and the field value. Field names are case-insensitive. The
     1366               field value <em class="bcp14">MAY</em> be preceded by any amount of LWS, though a single SP is preferred. Header fields can be extended over multiple lines by preceding
     1367               each extra line with at least one SP or HTAB. Applications ought to follow "common form", where one is known or indicated,
     1368               when generating HTTP constructs, since there might exist some implementations that fail to accept anything beyond the common
     1369               forms.
     1370            </p>
     1371            <div id="rfc.figure.u.32"></div><pre class="inline"><span id="rfc.iref.g.66"></span><span id="rfc.iref.g.67"></span><span id="rfc.iref.g.68"></span><span id="rfc.iref.g.69"></span>  <a href="#message.headers" class="smpl">message-header</a> = <a href="#message.headers" class="smpl">field-name</a> ":" [ <a href="#message.headers" class="smpl">field-value</a> ]
    13231372  <a href="#message.headers" class="smpl">field-name</a>     = <a href="#rule.token.separators" class="smpl">token</a>
    13241373  <a href="#message.headers" class="smpl">field-value</a>    = *( <a href="#message.headers" class="smpl">field-content</a> | <a href="#rule.LWS" class="smpl">LWS</a> )
     
    13281377                   ; of <a href="#rule.token.separators" class="smpl">token</a>, <a href="#rule.token.separators" class="smpl">separators</a>, and <a href="#rule.quoted-string" class="smpl">quoted-string</a>
    13291378</pre><p id="rfc.section.4.2.p.3">The field-content does not include any leading or trailing LWS: linear white space occurring before the first non-whitespace
    1330          character of the field-value or after the last non-whitespace character of the field-value. Such leading or trailing LWS <em class="bcp14">MAY</em> be removed without changing the semantics of the field value. Any LWS that occurs between field-content <em class="bcp14">MAY</em> be replaced with a single SP before interpreting the field value or forwarding the message downstream.
    1331       </p>
    1332       <p id="rfc.section.4.2.p.4">The order in which header fields with differing field names are received is not significant. However, it is "good practice"
    1333          to send general-header fields first, followed by request-header or response-header fields, and ending with the entity-header
    1334          fields.
    1335       </p>
    1336       <p id="rfc.section.4.2.p.5">Multiple message-header fields with the same field-name <em class="bcp14">MAY</em> be present in a message if and only if the entire field-value for that header field is defined as a comma-separated list [i.e.,
    1337          #(values)]. It <em class="bcp14">MUST</em> be possible to combine the multiple header fields into one "field-name: field-value" pair, without changing the semantics
    1338          of the message, by appending each subsequent field-value to the first, each separated by a comma. The order in which header
    1339          fields with the same field-name are received is therefore significant to the interpretation of the combined field value, and
    1340          thus a proxy <em class="bcp14">MUST NOT</em> change the order of these field values when a message is forwarded.
    1341       </p>
    1342       <h2 id="rfc.section.4.3"><a href="#rfc.section.4.3">4.3</a>&nbsp;<a id="message.body" href="#message.body">Message Body</a></h2>
    1343       <p id="rfc.section.4.3.p.1">The message-body (if any) of an HTTP message is used to carry the entity-body associated with the request or response. The
    1344          message-body differs from the entity-body only when a transfer-coding has been applied, as indicated by the Transfer-Encoding
    1345          header field (<a href="#header.transfer-encoding" id="rfc.xref.header.transfer-encoding.2" title="Transfer-Encoding">Section&nbsp;8.7</a>).
    1346       </p>
    1347       <div id="rfc.figure.u.33"></div><pre class="inline"><span id="rfc.iref.g.70"></span>  <a href="#message.body" class="smpl">message-body</a> = <a href="#abnf.dependencies" class="smpl">entity-body</a>
     1379               character of the field-value or after the last non-whitespace character of the field-value. Such leading or trailing LWS <em class="bcp14">MAY</em> be removed without changing the semantics of the field value. Any LWS that occurs between field-content <em class="bcp14">MAY</em> be replaced with a single SP before interpreting the field value or forwarding the message downstream.
     1380            </p>
     1381            <p id="rfc.section.4.2.p.4">The order in which header fields with differing field names are received is not significant. However, it is "good practice"
     1382               to send general-header fields first, followed by request-header or response-header fields, and ending with the entity-header
     1383               fields.
     1384            </p>
     1385            <p id="rfc.section.4.2.p.5">Multiple message-header fields with the same field-name <em class="bcp14">MAY</em> be present in a message if and only if the entire field-value for that header field is defined as a comma-separated list [i.e.,
     1386               #(values)]. It <em class="bcp14">MUST</em> be possible to combine the multiple header fields into one "field-name: field-value" pair, without changing the semantics
     1387               of the message, by appending each subsequent field-value to the first, each separated by a comma. The order in which header
     1388               fields with the same field-name are received is therefore significant to the interpretation of the combined field value, and
     1389               thus a proxy <em class="bcp14">MUST NOT</em> change the order of these field values when a message is forwarded.
     1390            </p>
     1391         </div>
     1392         <div id="message.body">
     1393            <h2 id="rfc.section.4.3"><a href="#rfc.section.4.3">4.3</a>&nbsp;<a href="#message.body">Message Body</a></h2>
     1394            <p id="rfc.section.4.3.p.1">The message-body (if any) of an HTTP message is used to carry the entity-body associated with the request or response. The
     1395               message-body differs from the entity-body only when a transfer-coding has been applied, as indicated by the Transfer-Encoding
     1396               header field (<a href="#header.transfer-encoding" id="rfc.xref.header.transfer-encoding.2" title="Transfer-Encoding">Section&nbsp;8.7</a>).
     1397            </p>
     1398            <div id="rfc.figure.u.33"></div><pre class="inline"><span id="rfc.iref.g.70"></span>  <a href="#message.body" class="smpl">message-body</a> = <a href="#abnf.dependencies" class="smpl">entity-body</a>
    13481399               | &lt;entity-body encoded as per <a href="#header.transfer-encoding" class="smpl">Transfer-Encoding</a>&gt;
    13491400</pre><p id="rfc.section.4.3.p.3">Transfer-Encoding <em class="bcp14">MUST</em> be used to indicate any transfer-codings applied by an application to ensure safe and proper transfer of the message. Transfer-Encoding
    1350          is a property of the message, not of the entity, and thus <em class="bcp14">MAY</em> be added or removed by any application along the request/response chain. (However, <a href="#transfer.codings" title="Transfer Codings">Section&nbsp;3.4</a> places restrictions on when certain transfer-codings may be used.)
    1351       </p>
    1352       <p id="rfc.section.4.3.p.4">The rules for when a message-body is allowed in a message differ for requests and responses.</p>
    1353       <p id="rfc.section.4.3.p.5">The presence of a message-body in a request is signaled by the inclusion of a Content-Length or Transfer-Encoding header field
    1354          in the request's message-headers. A message-body <em class="bcp14">MUST NOT</em> be included in a request if the specification of the request method (<a href="p2-semantics.html#method" title="Method">Section 3</a> of <a href="#Part2" id="rfc.xref.Part2.6"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>) explicitly disallows an entity-body in requests. When a request message contains both a message-body of non-zero length
    1355          and a method that does not define any semantics for that request message-body, then an origin server <em class="bcp14">SHOULD</em> either ignore the message-body or respond with an appropriate error message (e.g., 413). A proxy or gateway, when presented
    1356          the same request, <em class="bcp14">SHOULD</em> either forward the request inbound with the message-body or ignore the message-body when determining a response.
    1357       </p>
    1358       <p id="rfc.section.4.3.p.6">For response messages, whether or not a message-body is included with a message is dependent on both the request method and
    1359          the response status code (<a href="#status.code.and.reason.phrase" title="Status Code and Reason Phrase">Section&nbsp;6.1.1</a>). All responses to the HEAD request method <em class="bcp14">MUST NOT</em> include a message-body, even though the presence of entity-header fields might lead one to believe they do. All 1xx (informational),
    1360          204 (No Content), and 304 (Not Modified) responses <em class="bcp14">MUST NOT</em> include a message-body. All other responses do include a message-body, although it <em class="bcp14">MAY</em> be of zero length.
    1361       </p>
    1362       <h2 id="rfc.section.4.4"><a href="#rfc.section.4.4">4.4</a>&nbsp;<a id="message.length" href="#message.length">Message Length</a></h2>
    1363       <p id="rfc.section.4.4.p.1">The transfer-length of a message is the length of the message-body as it appears in the message; that is, after any transfer-codings
    1364          have been applied. When a message-body is included with a message, the transfer-length of that body is determined by one of
    1365          the following (in order of precedence):
    1366       </p>
    1367       <p id="rfc.section.4.4.p.2"> </p>
    1368       <ol>
    1369          <li>
    1370             <p>Any response message which "<em class="bcp14">MUST NOT</em>" include a message-body (such as the 1xx, 204, and 304 responses and any response to a HEAD request) is always terminated
    1371                by the first empty line after the header fields, regardless of the entity-header fields present in the message.
    1372             </p>
    1373          </li>
    1374          <li>
    1375             <p>If a Transfer-Encoding header field (<a href="#header.transfer-encoding" id="rfc.xref.header.transfer-encoding.3" title="Transfer-Encoding">Section&nbsp;8.7</a>) is present, then the transfer-length is defined by use of the "chunked" transfer-coding (<a href="#transfer.codings" title="Transfer Codings">Section&nbsp;3.4</a>), unless the message is terminated by closing the connection.
    1376             </p>
    1377          </li>
    1378          <li>
    1379             <p>If a Content-Length header field (<a href="#header.content-length" id="rfc.xref.header.content-length.1" title="Content-Length">Section&nbsp;8.2</a>) is present, its decimal value in OCTETs represents both the entity-length and the transfer-length. The Content-Length header
    1380                field <em class="bcp14">MUST NOT</em> be sent if these two lengths are different (i.e., if a Transfer-Encoding header field is present). If a message is received
    1381                with both a Transfer-Encoding header field and a Content-Length header field, the latter <em class="bcp14">MUST</em> be ignored.
    1382             </p>
    1383          </li>
    1384          <li>
    1385             <p>If the message uses the media type "multipart/byteranges", and the transfer-length is not otherwise specified, then this self-delimiting
    1386                media type defines the transfer-length. This media type <em class="bcp14">MUST NOT</em> be used unless the sender knows that the recipient can parse it; the presence in a request of a Range header with multiple
    1387                byte-range specifiers from a 1.1 client implies that the client can parse multipart/byteranges responses.
    1388             </p>
    1389             <ul class="empty">
    1390                <li>A range header might be forwarded by a 1.0 proxy that does not understand multipart/byteranges; in this case the server <em class="bcp14">MUST</em> delimit the message using methods defined in items 1, 3 or 5 of this section.
    1391                </li>
    1392             </ul>
    1393          </li>
    1394          <li>
    1395             <p>By the server closing the connection. (Closing the connection cannot be used to indicate the end of a request body, since
    1396                that would leave no possibility for the server to send back a response.)
    1397             </p>
    1398          </li>
    1399       </ol>
    1400       <p id="rfc.section.4.4.p.3">For compatibility with HTTP/1.0 applications, HTTP/1.1 requests containing a message-body <em class="bcp14">MUST</em> include a valid Content-Length header field unless the server is known to be HTTP/1.1 compliant. If a request contains a message-body
    1401          and a Content-Length is not given, the server <em class="bcp14">SHOULD</em> respond with 400 (Bad Request) if it cannot determine the length of the message, or with 411 (Length Required) if it wishes
    1402          to insist on receiving a valid Content-Length.
    1403       </p>
    1404       <p id="rfc.section.4.4.p.4">All HTTP/1.1 applications that receive entities <em class="bcp14">MUST</em> accept the "chunked" transfer-coding (<a href="#transfer.codings" title="Transfer Codings">Section&nbsp;3.4</a>), thus allowing this mechanism to be used for messages when the message length cannot be determined in advance.
    1405       </p>
    1406       <p id="rfc.section.4.4.p.5">Messages <em class="bcp14">MUST NOT</em> include both a Content-Length header field and a transfer-coding. If the message does include a transfer-coding, the Content-Length <em class="bcp14">MUST</em> be ignored.
    1407       </p>
    1408       <p id="rfc.section.4.4.p.6">When a Content-Length is given in a message where a message-body is allowed, its field value <em class="bcp14">MUST</em> exactly match the number of OCTETs in the message-body. HTTP/1.1 user agents <em class="bcp14">MUST</em> notify the user when an invalid length is received and detected.
    1409       </p>
    1410       <h2 id="rfc.section.4.5"><a href="#rfc.section.4.5">4.5</a>&nbsp;<a id="general.header.fields" href="#general.header.fields">General Header Fields</a></h2>
    1411       <p id="rfc.section.4.5.p.1">There are a few header fields which have general applicability for both request and response messages, but which do not apply
    1412          to the entity being transferred. These header fields apply only to the message being transmitted.
    1413       </p>
    1414       <div id="rfc.figure.u.34"></div><pre class="inline"><span id="rfc.iref.g.71"></span>  <a href="#general.header.fields" class="smpl">general-header</a> = <a href="#abnf.dependencies" class="smpl">Cache-Control</a>            ; <a href="#Part6" id="rfc.xref.Part6.6"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>, <a href="p6-cache.html#header.cache-control" title="Cache-Control">Section 16.2</a>
     1401               is a property of the message, not of the entity, and thus <em class="bcp14">MAY</em> be added or removed by any application along the request/response chain. (However, <a href="#transfer.codings" title="Transfer Codings">Section&nbsp;3.4</a> places restrictions on when certain transfer-codings may be used.)
     1402            </p>
     1403            <p id="rfc.section.4.3.p.4">The rules for when a message-body is allowed in a message differ for requests and responses.</p>
     1404            <p id="rfc.section.4.3.p.5">The presence of a message-body in a request is signaled by the inclusion of a Content-Length or Transfer-Encoding header field
     1405               in the request's message-headers. A message-body <em class="bcp14">MUST NOT</em> be included in a request if the specification of the request method (<a href="p2-semantics.html#method" title="Method">Section 3</a> of <a href="#Part2" id="rfc.xref.Part2.6"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>) explicitly disallows an entity-body in requests. When a request message contains both a message-body of non-zero length
     1406               and a method that does not define any semantics for that request message-body, then an origin server <em class="bcp14">SHOULD</em> either ignore the message-body or respond with an appropriate error message (e.g., 413). A proxy or gateway, when presented
     1407               the same request, <em class="bcp14">SHOULD</em> either forward the request inbound with the message-body or ignore the message-body when determining a response.
     1408            </p>
     1409            <p id="rfc.section.4.3.p.6">For response messages, whether or not a message-body is included with a message is dependent on both the request method and
     1410               the response status code (<a href="#status.code.and.reason.phrase" title="Status Code and Reason Phrase">Section&nbsp;6.1.1</a>). All responses to the HEAD request method <em class="bcp14">MUST NOT</em> include a message-body, even though the presence of entity-header fields might lead one to believe they do. All 1xx (informational),
     1411               204 (No Content), and 304 (Not Modified) responses <em class="bcp14">MUST NOT</em> include a message-body. All other responses do include a message-body, although it <em class="bcp14">MAY</em> be of zero length.
     1412            </p>
     1413         </div>
     1414         <div id="message.length">
     1415            <h2 id="rfc.section.4.4"><a href="#rfc.section.4.4">4.4</a>&nbsp;<a href="#message.length">Message Length</a></h2>
     1416            <p id="rfc.section.4.4.p.1">The transfer-length of a message is the length of the message-body as it appears in the message; that is, after any transfer-codings
     1417               have been applied. When a message-body is included with a message, the transfer-length of that body is determined by one of
     1418               the following (in order of precedence):
     1419            </p>
     1420            <p id="rfc.section.4.4.p.2"></p>
     1421            <ol>
     1422               <li>
     1423                  <p>Any response message which "<em class="bcp14">MUST NOT</em>" include a message-body (such as the 1xx, 204, and 304 responses and any response to a HEAD request) is always terminated
     1424                     by the first empty line after the header fields, regardless of the entity-header fields present in the message.
     1425                  </p>
     1426               </li>
     1427               <li>
     1428                  <p>If a Transfer-Encoding header field (<a href="#header.transfer-encoding" id="rfc.xref.header.transfer-encoding.3" title="Transfer-Encoding">Section&nbsp;8.7</a>) is present, then the transfer-length is defined by use of the "chunked" transfer-coding (<a href="#transfer.codings" title="Transfer Codings">Section&nbsp;3.4</a>), unless the message is terminated by closing the connection.
     1429                  </p>
     1430               </li>
     1431               <li>
     1432                  <p>If a Content-Length header field (<a href="#header.content-length" id="rfc.xref.header.content-length.1" title="Content-Length">Section&nbsp;8.2</a>) is present, its decimal value in OCTETs represents both the entity-length and the transfer-length. The Content-Length header
     1433                     field <em class="bcp14">MUST NOT</em> be sent if these two lengths are different (i.e., if a Transfer-Encoding header field is present). If a message is received
     1434                     with both a Transfer-Encoding header field and a Content-Length header field, the latter <em class="bcp14">MUST</em> be ignored.
     1435                  </p>
     1436               </li>
     1437               <li>
     1438                  <p>If the message uses the media type "multipart/byteranges", and the transfer-length is not otherwise specified, then this self-delimiting
     1439                     media type defines the transfer-length. This media type <em class="bcp14">MUST NOT</em> be used unless the sender knows that the recipient can parse it; the presence in a request of a Range header with multiple
     1440                     byte-range specifiers from a 1.1 client implies that the client can parse multipart/byteranges responses.
     1441                  </p>
     1442                  <ul class="empty">
     1443                     <li>A range header might be forwarded by a 1.0 proxy that does not understand multipart/byteranges; in this case the server <em class="bcp14">MUST</em> delimit the message using methods defined in items 1, 3 or 5 of this section.
     1444                     </li>
     1445                  </ul>
     1446               </li>
     1447               <li>
     1448                  <p>By the server closing the connection. (Closing the connection cannot be used to indicate the end of a request body, since
     1449                     that would leave no possibility for the server to send back a response.)
     1450                  </p>
     1451               </li>
     1452            </ol>
     1453            <p id="rfc.section.4.4.p.3">For compatibility with HTTP/1.0 applications, HTTP/1.1 requests containing a message-body <em class="bcp14">MUST</em> include a valid Content-Length header field unless the server is known to be HTTP/1.1 compliant. If a request contains a message-body
     1454               and a Content-Length is not given, the server <em class="bcp14">SHOULD</em> respond with 400 (Bad Request) if it cannot determine the length of the message, or with 411 (Length Required) if it wishes
     1455               to insist on receiving a valid Content-Length.
     1456            </p>
     1457            <p id="rfc.section.4.4.p.4">All HTTP/1.1 applications that receive entities <em class="bcp14">MUST</em> accept the "chunked" transfer-coding (<a href="#transfer.codings" title="Transfer Codings">Section&nbsp;3.4</a>), thus allowing this mechanism to be used for messages when the message length cannot be determined in advance.
     1458            </p>
     1459            <p id="rfc.section.4.4.p.5">Messages <em class="bcp14">MUST NOT</em> include both a Content-Length header field and a transfer-coding. If the message does include a transfer-coding, the Content-Length <em class="bcp14">MUST</em> be ignored.
     1460            </p>
     1461            <p id="rfc.section.4.4.p.6">When a Content-Length is given in a message where a message-body is allowed, its field value <em class="bcp14">MUST</em> exactly match the number of OCTETs in the message-body. HTTP/1.1 user agents <em class="bcp14">MUST</em> notify the user when an invalid length is received and detected.
     1462            </p>
     1463         </div>
     1464         <div id="general.header.fields">
     1465            <h2 id="rfc.section.4.5"><a href="#rfc.section.4.5">4.5</a>&nbsp;<a href="#general.header.fields">General Header Fields</a></h2>
     1466            <p id="rfc.section.4.5.p.1">There are a few header fields which have general applicability for both request and response messages, but which do not apply
     1467               to the entity being transferred. These header fields apply only to the message being transmitted.
     1468            </p>
     1469            <div id="rfc.figure.u.34"></div><pre class="inline"><span id="rfc.iref.g.71"></span>  <a href="#general.header.fields" class="smpl">general-header</a> = <a href="#abnf.dependencies" class="smpl">Cache-Control</a>            ; <a href="#Part6" id="rfc.xref.Part6.6"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>, <a href="p6-cache.html#header.cache-control" title="Cache-Control">Section 16.2</a>
    14151470                 | <a href="#header.connection" class="smpl">Connection</a>               ; <a href="#header.connection" id="rfc.xref.header.connection.1" title="Connection">Section&nbsp;8.1</a>
    14161471                 | <a href="#header.date" class="smpl">Date</a>                     ; <a href="#header.date" id="rfc.xref.header.date.1" title="Date">Section&nbsp;8.3</a>
     
    14221477                 | <a href="#abnf.dependencies" class="smpl">Warning</a>                  ; <a href="#Part6" id="rfc.xref.Part6.8"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>, <a href="p6-cache.html#header.warning" title="Warning">Section 16.6</a>
    14231478</pre><p id="rfc.section.4.5.p.3">General-header field names can be extended reliably only in combination with a change in the protocol version. However, new
    1424          or experimental header fields may be given the semantics of general header fields if all parties in the communication recognize
    1425          them to be general-header fields. Unrecognized header fields are treated as entity-header fields.
    1426       </p>
    1427       <h1 id="rfc.section.5"><a href="#rfc.section.5">5.</a>&nbsp;<a id="request" href="#request">Request</a></h1>
    1428       <p id="rfc.section.5.p.1">A request message from a client to a server includes, within the first line of that message, the method to be applied to the
    1429          resource, the identifier of the resource, and the protocol version in use.
    1430       </p>
    1431       <div id="rfc.figure.u.35"></div><pre class="inline"><span id="rfc.iref.g.72"></span>  <a href="#request" class="smpl">Request</a>       = <a href="#request-line" class="smpl">Request-Line</a>              ; <a href="#request-line" title="Request-Line">Section&nbsp;5.1</a>
     1479               or experimental header fields may be given the semantics of general header fields if all parties in the communication recognize
     1480               them to be general-header fields. Unrecognized header fields are treated as entity-header fields.
     1481            </p>
     1482         </div>
     1483      </div>
     1484      <div id="request">
     1485         <h1 id="rfc.section.5"><a href="#rfc.section.5">5.</a>&nbsp;<a href="#request">Request</a></h1>
     1486         <p id="rfc.section.5.p.1">A request message from a client to a server includes, within the first line of that message, the method to be applied to the
     1487            resource, the identifier of the resource, and the protocol version in use.
     1488         </p>
     1489         <div id="rfc.figure.u.35"></div><pre class="inline"><span id="rfc.iref.g.72"></span>  <a href="#request" class="smpl">Request</a>       = <a href="#request-line" class="smpl">Request-Line</a>              ; <a href="#request-line" title="Request-Line">Section&nbsp;5.1</a>
    14321490                  *(( <a href="#general.header.fields" class="smpl">general-header</a>        ; <a href="#general.header.fields" title="General Header Fields">Section&nbsp;4.5</a>
    14331491                   | <a href="#abnf.dependencies" class="smpl">request-header</a>         ; <a href="#Part2" id="rfc.xref.Part2.7"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>, <a href="p2-semantics.html#request.header.fields" title="Request Header Fields">Section 4</a>
     
    14351493                  <a href="#rule.CRLF" class="smpl">CRLF</a>
    14361494                  [ <a href="#message.body" class="smpl">message-body</a> ]          ; <a href="#message.body" title="Message Body">Section&nbsp;4.3</a>
    1437 </pre><h2 id="rfc.section.5.1"><a href="#rfc.section.5.1">5.1</a>&nbsp;<a id="request-line" href="#request-line">Request-Line</a></h2>
    1438       <p id="rfc.section.5.1.p.1">The Request-Line begins with a method token, followed by the Request-URI and the protocol version, and ending with CRLF. The
    1439          elements are separated by SP characters. No CR or LF is allowed except in the final CRLF sequence.
    1440       </p>
    1441       <div id="rfc.figure.u.36"></div><pre class="inline"><span id="rfc.iref.g.73"></span>  <a href="#request-line" class="smpl">Request-Line</a>   = <a href="#method" class="smpl">Method</a> <a href="#core.rules" class="smpl">SP</a> <a href="#request-uri" class="smpl">Request-URI</a> <a href="#core.rules" class="smpl">SP</a> <a href="#http.version" class="smpl">HTTP-Version</a> <a href="#rule.CRLF" class="smpl">CRLF</a>
    1442 </pre><h3 id="rfc.section.5.1.1"><a href="#rfc.section.5.1.1">5.1.1</a>&nbsp;<a id="method" href="#method">Method</a></h3>
    1443       <p id="rfc.section.5.1.1.p.1">The Method token indicates the method to be performed on the resource identified by the Request-URI. The method is case-sensitive.</p>
    1444       <div id="rfc.figure.u.37"></div><pre class="inline"><span id="rfc.iref.g.74"></span><span id="rfc.iref.g.75"></span>  <a href="#method" class="smpl">Method</a>         = <a href="#rule.token.separators" class="smpl">token</a>
    1445 </pre><h3 id="rfc.section.5.1.2"><a href="#rfc.section.5.1.2">5.1.2</a>&nbsp;<a id="request-uri" href="#request-uri">Request-URI</a></h3>
    1446       <p id="rfc.section.5.1.2.p.1">The Request-URI is a Uniform Resource Identifier (<a href="#uri" title="Uniform Resource Identifiers">Section&nbsp;3.2</a>) and identifies the resource upon which to apply the request.
    1447       </p>
    1448       <div id="rfc.figure.u.38"></div><pre class="inline"><span id="rfc.iref.g.76"></span>  <a href="#request-uri" class="smpl">Request-URI</a>    = "*"
     1495</pre><div id="request-line">
     1496            <h2 id="rfc.section.5.1"><a href="#rfc.section.5.1">5.1</a>&nbsp;<a href="#request-line">Request-Line</a></h2>
     1497            <p id="rfc.section.5.1.p.1">The Request-Line begins with a method token, followed by the Request-URI and the protocol version, and ending with CRLF. The
     1498               elements are separated by SP characters. No CR or LF is allowed except in the final CRLF sequence.
     1499            </p>
     1500            <div id="rfc.figure.u.36"></div><pre class="inline"><span id="rfc.iref.g.73"></span>  <a href="#request-line" class="smpl">Request-Line</a>   = <a href="#method" class="smpl">Method</a> <a href="#core.rules" class="smpl">SP</a> <a href="#request-uri" class="smpl">Request-URI</a> <a href="#core.rules" class="smpl">SP</a> <a href="#http.version" class="smpl">HTTP-Version</a> <a href="#rule.CRLF" class="smpl">CRLF</a>
     1501</pre><div id="method">
     1502               <h3 id="rfc.section.5.1.1"><a href="#rfc.section.5.1.1">5.1.1</a>&nbsp;<a href="#method">Method</a></h3>
     1503               <p id="rfc.section.5.1.1.p.1">The Method token indicates the method to be performed on the resource identified by the Request-URI. The method is case-sensitive.</p>
     1504               <div id="rfc.figure.u.37"></div><pre class="inline"><span id="rfc.iref.g.74"></span><span id="rfc.iref.g.75"></span>  <a href="#method" class="smpl">Method</a>         = <a href="#rule.token.separators" class="smpl">token</a>
     1505</pre></div>
     1506            <div id="request-uri">
     1507               <h3 id="rfc.section.5.1.2"><a href="#rfc.section.5.1.2">5.1.2</a>&nbsp;<a href="#request-uri">Request-URI</a></h3>
     1508               <p id="rfc.section.5.1.2.p.1">The Request-URI is a Uniform Resource Identifier (<a href="#uri" title="Uniform Resource Identifiers">Section&nbsp;3.2</a>) and identifies the resource upon which to apply the request.
     1509               </p>
     1510               <div id="rfc.figure.u.38"></div><pre class="inline"><span id="rfc.iref.g.76"></span>  <a href="#request-uri" class="smpl">Request-URI</a>    = "*"
    14491511                 | <a href="#general.syntax" class="smpl">absoluteURI</a>
    14501512                 | ( <a href="#general.syntax" class="smpl">path-absolute</a> [ "?" <a href="#general.syntax" class="smpl">query</a> ] )
    14511513                 | <a href="#general.syntax" class="smpl">authority</a>
    14521514</pre><p id="rfc.section.5.1.2.p.3">The four options for Request-URI are dependent on the nature of the request. The asterisk "*" means that the request does
    1453          not apply to a particular resource, but to the server itself, and is only allowed when the method used does not necessarily
    1454          apply to a resource. One example would be
    1455       </p>
    1456       <div id="rfc.figure.u.39"></div><pre class="text">    OPTIONS * HTTP/1.1
     1515                  not apply to a particular resource, but to the server itself, and is only allowed when the method used does not necessarily
     1516                  apply to a resource. One example would be
     1517               </p>
     1518               <div id="rfc.figure.u.39"></div><pre class="text">    OPTIONS * HTTP/1.1
    14571519</pre><p id="rfc.section.5.1.2.p.5">The absoluteURI form is <em class="bcp14">REQUIRED</em> when the request is being made to a proxy. The proxy is requested to forward the request or service it from a valid cache,
    1458          and return the response. Note that the proxy <em class="bcp14">MAY</em> forward the request on to another proxy or directly to the server specified by the absoluteURI. In order to avoid request
    1459          loops, a proxy <em class="bcp14">MUST</em> be able to recognize all of its server names, including any aliases, local variations, and the numeric IP address. An example
    1460          Request-Line would be:
    1461       </p>
    1462       <div id="rfc.figure.u.40"></div><pre class="text">    GET http://www.example.org/pub/WWW/TheProject.html HTTP/1.1
     1520                  and return the response. Note that the proxy <em class="bcp14">MAY</em> forward the request on to another proxy or directly to the server specified by the absoluteURI. In order to avoid request
     1521                  loops, a proxy <em class="bcp14">MUST</em> be able to recognize all of its server names, including any aliases, local variations, and the numeric IP address. An example
     1522                  Request-Line would be:
     1523               </p>
     1524               <div id="rfc.figure.u.40"></div><pre class="text">    GET http://www.example.org/pub/WWW/TheProject.html HTTP/1.1
    14631525</pre><p id="rfc.section.5.1.2.p.7">To allow for transition to absoluteURIs in all requests in future versions of HTTP, all HTTP/1.1 servers <em class="bcp14">MUST</em> accept the absoluteURI form in requests, even though HTTP/1.1 clients will only generate them in requests to proxies.
    1464       </p>
    1465       <p id="rfc.section.5.1.2.p.8">The authority form is only used by the CONNECT method (<a href="p2-semantics.html#CONNECT" title="CONNECT">Section 8.9</a> of <a href="#Part2" id="rfc.xref.Part2.8"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>).
    1466       </p>
    1467       <p id="rfc.section.5.1.2.p.9">The most common form of Request-URI is that used to identify a resource on an origin server or gateway. In this case the absolute
    1468          path of the URI <em class="bcp14">MUST</em> be transmitted (see <a href="#general.syntax" title="General Syntax">Section&nbsp;3.2.1</a>, path-absolute) as the Request-URI, and the network location of the URI (authority) <em class="bcp14">MUST</em> be transmitted in a Host header field. For example, a client wishing to retrieve the resource above directly from the origin
    1469          server would create a TCP connection to port 80 of the host "www.example.org" and send the lines:
    1470       </p>
    1471       <div id="rfc.figure.u.41"></div><pre class="text">    GET /pub/WWW/TheProject.html HTTP/1.1
     1526               </p>
     1527               <p id="rfc.section.5.1.2.p.8">The authority form is only used by the CONNECT method (<a href="p2-semantics.html#CONNECT" title="CONNECT">Section 8.9</a> of <a href="#Part2" id="rfc.xref.Part2.8"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>).
     1528               </p>
     1529               <p id="rfc.section.5.1.2.p.9">The most common form of Request-URI is that used to identify a resource on an origin server or gateway. In this case the absolute
     1530                  path of the URI <em class="bcp14">MUST</em> be transmitted (see <a href="#general.syntax" title="General Syntax">Section&nbsp;3.2.1</a>, path-absolute) as the Request-URI, and the network location of the URI (authority) <em class="bcp14">MUST</em> be transmitted in a Host header field. For example, a client wishing to retrieve the resource above directly from the origin
     1531                  server would create a TCP connection to port 80 of the host "www.example.org" and send the lines:
     1532               </p>
     1533               <div id="rfc.figure.u.41"></div><pre class="text">    GET /pub/WWW/TheProject.html HTTP/1.1
    14721534    Host: www.example.org
    14731535</pre><p id="rfc.section.5.1.2.p.11">followed by the remainder of the Request. Note that the absolute path cannot be empty; if none is present in the original
    1474          URI, it <em class="bcp14">MUST</em> be given as "/" (the server root).
    1475       </p>
    1476       <p id="rfc.section.5.1.2.p.12">The Request-URI is transmitted in the format specified in <a href="#general.syntax" title="General Syntax">Section&nbsp;3.2.1</a>. If the Request-URI is encoded using the "% HEX HEX" encoding <a href="#RFC2396" id="rfc.xref.RFC2396.11"><cite title="Uniform Resource Identifiers (URI): Generic Syntax">[RFC2396]</cite></a>, the origin server <em class="bcp14">MUST</em> decode the Request-URI in order to properly interpret the request. Servers <em class="bcp14">SHOULD</em> respond to invalid Request-URIs with an appropriate status code.
    1477       </p>
    1478       <p id="rfc.section.5.1.2.p.13">A transparent proxy <em class="bcp14">MUST NOT</em> rewrite the "path-absolute" part of the received Request-URI when forwarding it to the next inbound server, except as noted
    1479          above to replace a null path-absolute with "/".
    1480       </p>
    1481       <p id="rfc.section.5.1.2.p.14"> </p>
    1482       <ul class="empty">
    1483          <li> <b>Note:</b> The "no rewrite" rule prevents the proxy from changing the meaning of the request when the origin server is improperly using
    1484             a non-reserved URI character for a reserved purpose. Implementors should be aware that some pre-HTTP/1.1 proxies have been
    1485             known to rewrite the Request-URI.
    1486          </li>
    1487       </ul>
    1488       <h2 id="rfc.section.5.2"><a href="#rfc.section.5.2">5.2</a>&nbsp;<a id="the.resource.identified.by.a.request" href="#the.resource.identified.by.a.request">The Resource Identified by a Request</a></h2>
    1489       <p id="rfc.section.5.2.p.1">The exact resource identified by an Internet request is determined by examining both the Request-URI and the Host header field.</p>
    1490       <p id="rfc.section.5.2.p.2">An origin server that does not allow resources to differ by the requested host <em class="bcp14">MAY</em> ignore the Host header field value when determining the resource identified by an HTTP/1.1 request. (But see <a href="#changes.to.simplify.multi-homed.web.servers.and.conserve.ip.addresses" title="Changes to Simplify Multi-homed Web Servers and Conserve IP Addresses">Appendix&nbsp;D.1.1</a> for other requirements on Host support in HTTP/1.1.)
    1491       </p>
    1492       <p id="rfc.section.5.2.p.3">An origin server that does differentiate resources based on the host requested (sometimes referred to as virtual hosts or
    1493          vanity host names) <em class="bcp14">MUST</em> use the following rules for determining the requested resource on an HTTP/1.1 request:
    1494       </p>
    1495       <ol>
    1496          <li>If Request-URI is an absoluteURI, the host is part of the Request-URI. Any Host header field value in the request <em class="bcp14">MUST</em> be ignored.
    1497          </li>
    1498          <li>If the Request-URI is not an absoluteURI, and the request includes a Host header field, the host is determined by the Host
    1499             header field value.
    1500          </li>
    1501          <li>If the host as determined by rule 1 or 2 is not a valid host on the server, the response <em class="bcp14">MUST</em> be a 400 (Bad Request) error message.
    1502          </li>
    1503       </ol>
    1504       <p id="rfc.section.5.2.p.4">Recipients of an HTTP/1.0 request that lacks a Host header field <em class="bcp14">MAY</em> attempt to use heuristics (e.g., examination of the URI path for something unique to a particular host) in order to determine
    1505          what exact resource is being requested.
    1506       </p>
    1507       <h1 id="rfc.section.6"><a href="#rfc.section.6">6.</a>&nbsp;<a id="response" href="#response">Response</a></h1>
    1508       <p id="rfc.section.6.p.1">After receiving and interpreting a request message, a server responds with an HTTP response message.</p>
    1509       <div id="rfc.figure.u.42"></div><pre class="inline"><span id="rfc.iref.g.77"></span>  <a href="#response" class="smpl">Response</a>      = <a href="#status-line" class="smpl">Status-Line</a>               ; <a href="#status-line" title="Status-Line">Section&nbsp;6.1</a>
     1536                  URI, it <em class="bcp14">MUST</em> be given as "/" (the server root).
     1537               </p>
     1538               <p id="rfc.section.5.1.2.p.12">The Request-URI is transmitted in the format specified in <a href="#general.syntax" title="General Syntax">Section&nbsp;3.2.1</a>. If the Request-URI is encoded using the "% HEX HEX" encoding <a href="#RFC2396" id="rfc.xref.RFC2396.11"><cite title="Uniform Resource Identifiers (URI): Generic Syntax">[RFC2396]</cite></a>, the origin server <em class="bcp14">MUST</em> decode the Request-URI in order to properly interpret the request. Servers <em class="bcp14">SHOULD</em> respond to invalid Request-URIs with an appropriate status code.
     1539               </p>
     1540               <p id="rfc.section.5.1.2.p.13">A transparent proxy <em class="bcp14">MUST NOT</em> rewrite the "path-absolute" part of the received Request-URI when forwarding it to the next inbound server, except as noted
     1541                  above to replace a null path-absolute with "/".
     1542               </p>
     1543               <p id="rfc.section.5.1.2.p.14"></p>
     1544               <ul class="empty">
     1545                  <li><b>Note:</b> The "no rewrite" rule prevents the proxy from changing the meaning of the request when the origin server is improperly using
     1546                     a non-reserved URI character for a reserved purpose. Implementors should be aware that some pre-HTTP/1.1 proxies have been
     1547                     known to rewrite the Request-URI.
     1548                  </li>
     1549               </ul>
     1550            </div>
     1551         </div>
     1552         <div id="the.resource.identified.by.a.request">
     1553            <h2 id="rfc.section.5.2"><a href="#rfc.section.5.2">5.2</a>&nbsp;<a href="#the.resource.identified.by.a.request">The Resource Identified by a Request</a></h2>
     1554            <p id="rfc.section.5.2.p.1">The exact resource identified by an Internet request is determined by examining both the Request-URI and the Host header field.</p>
     1555            <p id="rfc.section.5.2.p.2">An origin server that does not allow resources to differ by the requested host <em class="bcp14">MAY</em> ignore the Host header field value when determining the resource identified by an HTTP/1.1 request. (But see <a href="#changes.to.simplify.multi-homed.web.servers.and.conserve.ip.addresses" title="Changes to Simplify Multi-homed Web Servers and Conserve IP Addresses">Appendix&nbsp;D.1.1</a> for other requirements on Host support in HTTP/1.1.)
     1556            </p>
     1557            <p id="rfc.section.5.2.p.3">An origin server that does differentiate resources based on the host requested (sometimes referred to as virtual hosts or
     1558               vanity host names) <em class="bcp14">MUST</em> use the following rules for determining the requested resource on an HTTP/1.1 request:
     1559            </p>
     1560            <ol>
     1561               <li>If Request-URI is an absoluteURI, the host is part of the Request-URI. Any Host header field value in the request <em class="bcp14">MUST</em> be ignored.
     1562               </li>
     1563               <li>If the Request-URI is not an absoluteURI, and the request includes a Host header field, the host is determined by the Host
     1564                  header field value.
     1565               </li>
     1566               <li>If the host as determined by rule 1 or 2 is not a valid host on the server, the response <em class="bcp14">MUST</em> be a 400 (Bad Request) error message.
     1567               </li>
     1568            </ol>
     1569            <p id="rfc.section.5.2.p.4">Recipients of an HTTP/1.0 request that lacks a Host header field <em class="bcp14">MAY</em> attempt to use heuristics (e.g., examination of the URI path for something unique to a particular host) in order to determine
     1570               what exact resource is being requested.
     1571            </p>
     1572         </div>
     1573      </div>
     1574      <div id="response">
     1575         <h1 id="rfc.section.6"><a href="#rfc.section.6">6.</a>&nbsp;<a href="#response">Response</a></h1>
     1576         <p id="rfc.section.6.p.1">After receiving and interpreting a request message, a server responds with an HTTP response message.</p>
     1577         <div id="rfc.figure.u.42"></div><pre class="inline"><span id="rfc.iref.g.77"></span>  <a href="#response" class="smpl">Response</a>      = <a href="#status-line" class="smpl">Status-Line</a>               ; <a href="#status-line" title="Status-Line">Section&nbsp;6.1</a>
    15101578                  *(( <a href="#general.header.fields" class="smpl">general-header</a>        ; <a href="#general.header.fields" title="General Header Fields">Section&nbsp;4.5</a>
    15111579                   | <a href="#abnf.dependencies" class="smpl">response-header</a>        ; <a href="#Part2" id="rfc.xref.Part2.9"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>, <a href="p2-semantics.html#response.header.fields" title="Response Header Fields">Section 6</a>
     
    15131581                  <a href="#rule.CRLF" class="smpl">CRLF</a>
    15141582                  [ <a href="#message.body" class="smpl">message-body</a> ]          ; <a href="#message.body" title="Message Body">Section&nbsp;4.3</a>
    1515 </pre><h2 id="rfc.section.6.1"><a href="#rfc.section.6.1">6.1</a>&nbsp;<a id="status-line" href="#status-line">Status-Line</a></h2>
    1516       <p id="rfc.section.6.1.p.1">The first line of a Response message is the Status-Line, consisting of the protocol version followed by a numeric status code
    1517          and its associated textual phrase, with each element separated by SP characters. No CR or LF is allowed except in the final
    1518          CRLF sequence.
    1519       </p>
    1520       <div id="rfc.figure.u.43"></div><pre class="inline"><span id="rfc.iref.g.78"></span>  <a href="#status-line" class="smpl">Status-Line</a> = <a href="#http.version" class="smpl">HTTP-Version</a> <a href="#core.rules" class="smpl">SP</a> <a href="#status.code.and.reason.phrase" class="smpl">Status-Code</a> <a href="#core.rules" class="smpl">SP</a> <a href="#status.code.and.reason.phrase" class="smpl">Reason-Phrase</a> <a href="#rule.CRLF" class="smpl">CRLF</a>
    1521 </pre><h3 id="rfc.section.6.1.1"><a href="#rfc.section.6.1.1">6.1.1</a>&nbsp;<a id="status.code.and.reason.phrase" href="#status.code.and.reason.phrase">Status Code and Reason Phrase</a></h3>
    1522       <p id="rfc.section.6.1.1.p.1">The Status-Code element is a 3-digit integer result code of the attempt to understand and satisfy the request. These codes
    1523          are fully defined in <a href="p2-semantics.html#status.codes" title="Status Code Definitions">Section 9</a> of <a href="#Part2" id="rfc.xref.Part2.10"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>. The Reason Phrase exists for the sole purpose of providing a textual description associated with the numeric status code,
    1524          out of deference to earlier Internet application protocols that were more frequently used with interactive text clients. A
    1525          client <em class="bcp14">SHOULD</em> ignore the content of the Reason Phrase.
    1526       </p>
    1527       <p id="rfc.section.6.1.1.p.2">The first digit of the Status-Code defines the class of response. The last two digits do not have any categorization role.
    1528          There are 5 values for the first digit:
    1529       </p>
    1530       <ul>
    1531          <li>1xx: Informational - Request received, continuing process</li>
    1532          <li>2xx: Success - The action was successfully received, understood, and accepted</li>
    1533          <li>3xx: Redirection - Further action must be taken in order to complete the request</li>
    1534          <li>4xx: Client Error - The request contains bad syntax or cannot be fulfilled</li>
    1535          <li>5xx: Server Error - The server failed to fulfill an apparently valid request</li>
    1536       </ul>
    1537       <div id="rfc.figure.u.44"></div><pre class="inline"><span id="rfc.iref.g.79"></span><span id="rfc.iref.g.80"></span><span id="rfc.iref.g.81"></span>  <a href="#status.code.and.reason.phrase" class="smpl">Status-Code</a>    = 3<a href="#core.rules" class="smpl">DIGIT</a>
     1583</pre><div id="status-line">
     1584            <h2 id="rfc.section.6.1"><a href="#rfc.section.6.1">6.1</a>&nbsp;<a href="#status-line">Status-Line</a></h2>
     1585            <p id="rfc.section.6.1.p.1">The first line of a Response message is the Status-Line, consisting of the protocol version followed by a numeric status code
     1586               and its associated textual phrase, with each element separated by SP characters. No CR or LF is allowed except in the final
     1587               CRLF sequence.
     1588            </p>
     1589            <div id="rfc.figure.u.43"></div><pre class="inline"><span id="rfc.iref.g.78"></span>  <a href="#status-line" class="smpl">Status-Line</a> = <a href="#http.version" class="smpl">HTTP-Version</a> <a href="#core.rules" class="smpl">SP</a> <a href="#status.code.and.reason.phrase" class="smpl">Status-Code</a> <a href="#core.rules" class="smpl">SP</a> <a href="#status.code.and.reason.phrase" class="smpl">Reason-Phrase</a> <a href="#rule.CRLF" class="smpl">CRLF</a>
     1590</pre><div id="status.code.and.reason.phrase">
     1591               <h3 id="rfc.section.6.1.1"><a href="#rfc.section.6.1.1">6.1.1</a>&nbsp;<a href="#status.code.and.reason.phrase">Status Code and Reason Phrase</a></h3>
     1592               <p id="rfc.section.6.1.1.p.1">The Status-Code element is a 3-digit integer result code of the attempt to understand and satisfy the request. These codes
     1593                  are fully defined in <a href="p2-semantics.html#status.codes" title="Status Code Definitions">Section 9</a> of <a href="#Part2" id="rfc.xref.Part2.10"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>. The Reason Phrase exists for the sole purpose of providing a textual description associated with the numeric status code,
     1594                  out of deference to earlier Internet application protocols that were more frequently used with interactive text clients. A
     1595                  client <em class="bcp14">SHOULD</em> ignore the content of the Reason Phrase.
     1596               </p>
     1597               <p id="rfc.section.6.1.1.p.2">The first digit of the Status-Code defines the class of response. The last two digits do not have any categorization role.
     1598                  There are 5 values for the first digit:
     1599               </p>
     1600               <ul>
     1601                  <li>1xx: Informational - Request received, continuing process</li>
     1602                  <li>2xx: Success - The action was successfully received, understood, and accepted</li>
     1603                  <li>3xx: Redirection - Further action must be taken in order to complete the request</li>
     1604                  <li>4xx: Client Error - The request contains bad syntax or cannot be fulfilled</li>
     1605                  <li>5xx: Server Error - The server failed to fulfill an apparently valid request</li>
     1606               </ul>
     1607               <div id="rfc.figure.u.44"></div><pre class="inline"><span id="rfc.iref.g.79"></span><span id="rfc.iref.g.80"></span><span id="rfc.iref.g.81"></span>  <a href="#status.code.and.reason.phrase" class="smpl">Status-Code</a>    = 3<a href="#core.rules" class="smpl">DIGIT</a>
    15381608  <a href="#status.code.and.reason.phrase" class="smpl">Reason-Phrase</a>  = *&lt;<a href="#rule.TEXT" class="smpl">TEXT</a>, excluding <a href="#core.rules" class="smpl">CR</a>, <a href="#core.rules" class="smpl">LF</a>&gt;
    1539 </pre><h1 id="rfc.section.7"><a href="#rfc.section.7">7.</a>&nbsp;<a id="connections" href="#connections">Connections</a></h1>
    1540       <h2 id="rfc.section.7.1"><a href="#rfc.section.7.1">7.1</a>&nbsp;<a id="persistent.connections" href="#persistent.connections">Persistent Connections</a></h2>
    1541       <h3 id="rfc.section.7.1.1"><a href="#rfc.section.7.1.1">7.1.1</a>&nbsp;<a id="persistent.purpose" href="#persistent.purpose">Purpose</a></h3>
    1542       <p id="rfc.section.7.1.1.p.1">Prior to persistent connections, a separate TCP connection was established to fetch each URL, increasing the load on HTTP
    1543          servers and causing congestion on the Internet. The use of inline images and other associated data often require a client
    1544          to make multiple requests of the same server in a short amount of time. Analysis of these performance problems and results
    1545          from a prototype implementation are available <a href="#Pad1995" id="rfc.xref.Pad1995.1"><cite title="Improving HTTP Latency">[Pad1995]</cite></a>  <a href="#Spe" id="rfc.xref.Spe.1"><cite title="Analysis of HTTP Performance Problems">[Spe]</cite></a>. Implementation experience and measurements of actual HTTP/1.1 (<cite title="Hypertext Transfer Protocol -- HTTP/1.1" id="rfc.xref.RFC2068.2">RFC 2068</cite>) implementations show good results <a href="#Nie1997" id="rfc.xref.Nie1997.1"><cite title="Network Performance Effects of HTTP/1.1, CSS1, and PNG">[Nie1997]</cite></a>. Alternatives have also been explored, for example, T/TCP <a href="#Tou1998" id="rfc.xref.Tou1998.1"><cite title="Analysis of HTTP Performance">[Tou1998]</cite></a>.
    1546       </p>
    1547       <p id="rfc.section.7.1.1.p.2">Persistent HTTP connections have a number of advantages: </p>
    1548       <ul>
    1549          <li>By opening and closing fewer TCP connections, CPU time is saved in routers and hosts (clients, servers, proxies, gateways,
    1550             tunnels, or caches), and memory used for TCP protocol control blocks can be saved in hosts.
    1551          </li>
    1552          <li>HTTP requests and responses can be pipelined on a connection. Pipelining allows a client to make multiple requests without
    1553             waiting for each response, allowing a single TCP connection to be used much more efficiently, with much lower elapsed time.
    1554          </li>
    1555          <li>Network congestion is reduced by reducing the number of packets caused by TCP opens, and by allowing TCP sufficient time to
    1556             determine the congestion state of the network.
    1557          </li>
    1558          <li>Latency on subsequent requests is reduced since there is no time spent in TCP's connection opening handshake.</li>
    1559          <li>HTTP can evolve more gracefully, since errors can be reported without the penalty of closing the TCP connection. Clients using
    1560             future versions of HTTP might optimistically try a new feature, but if communicating with an older server, retry with old
    1561             semantics after an error is reported.
    1562          </li>
    1563       </ul>
    1564       <p id="rfc.section.7.1.1.p.3">HTTP implementations <em class="bcp14">SHOULD</em> implement persistent connections.
    1565       </p>
    1566       <h3 id="rfc.section.7.1.2"><a href="#rfc.section.7.1.2">7.1.2</a>&nbsp;<a id="persistent.overall" href="#persistent.overall">Overall Operation</a></h3>
    1567       <p id="rfc.section.7.1.2.p.1">A significant difference between HTTP/1.1 and earlier versions of HTTP is that persistent connections are the default behavior
    1568          of any HTTP connection. That is, unless otherwise indicated, the client <em class="bcp14">SHOULD</em> assume that the server will maintain a persistent connection, even after error responses from the server.
    1569       </p>
    1570       <p id="rfc.section.7.1.2.p.2">Persistent connections provide a mechanism by which a client and a server can signal the close of a TCP connection. This signaling
    1571          takes place using the Connection header field (<a href="#header.connection" id="rfc.xref.header.connection.2" title="Connection">Section&nbsp;8.1</a>). Once a close has been signaled, the client <em class="bcp14">MUST NOT</em> send any more requests on that connection.
    1572       </p>
    1573       <h4 id="rfc.section.7.1.2.1"><a href="#rfc.section.7.1.2.1">7.1.2.1</a>&nbsp;<a id="persistent.negotiation" href="#persistent.negotiation">Negotiation</a></h4>
    1574       <p id="rfc.section.7.1.2.1.p.1">An HTTP/1.1 server <em class="bcp14">MAY</em> assume that a HTTP/1.1 client intends to maintain a persistent connection unless a Connection header including the connection-token
    1575          "close" was sent in the request. If the server chooses to close the connection immediately after sending the response, it <em class="bcp14">SHOULD</em> send a Connection header including the connection-token close.
    1576       </p>
    1577       <p id="rfc.section.7.1.2.1.p.2">An HTTP/1.1 client <em class="bcp14">MAY</em> expect a connection to remain open, but would decide to keep it open based on whether the response from a server contains
    1578          a Connection header with the connection-token close. In case the client does not want to maintain a connection for more than
    1579          that request, it <em class="bcp14">SHOULD</em> send a Connection header including the connection-token close.
    1580       </p>
    1581       <p id="rfc.section.7.1.2.1.p.3">If either the client or the server sends the close token in the Connection header, that request becomes the last one for the
    1582          connection.
    1583       </p>
    1584       <p id="rfc.section.7.1.2.1.p.4">Clients and servers <em class="bcp14">SHOULD NOT</em> assume that a persistent connection is maintained for HTTP versions less than 1.1 unless it is explicitly signaled. See <a href="#compatibility.with.http.1.0.persistent.connections" title="Compatibility with HTTP/1.0 Persistent Connections">Appendix&nbsp;D.2</a> for more information on backward compatibility with HTTP/1.0 clients.
    1585       </p>
    1586       <p id="rfc.section.7.1.2.1.p.5">In order to remain persistent, all messages on the connection <em class="bcp14">MUST</em> have a self-defined message length (i.e., one not defined by closure of the connection), as described in <a href="#message.length" title="Message Length">Section&nbsp;4.4</a>.
    1587       </p>
    1588       <h4 id="rfc.section.7.1.2.2"><a href="#rfc.section.7.1.2.2">7.1.2.2</a>&nbsp;<a id="pipelining" href="#pipelining">Pipelining</a></h4>
    1589       <p id="rfc.section.7.1.2.2.p.1">A client that supports persistent connections <em class="bcp14">MAY</em> "pipeline" its requests (i.e., send multiple requests without waiting for each response). A server <em class="bcp14">MUST</em> send its responses to those requests in the same order that the requests were received.
    1590       </p>
    1591       <p id="rfc.section.7.1.2.2.p.2">Clients which assume persistent connections and pipeline immediately after connection establishment <em class="bcp14">SHOULD</em> be prepared to retry their connection if the first pipelined attempt fails. If a client does such a retry, it <em class="bcp14">MUST NOT</em> pipeline before it knows the connection is persistent. Clients <em class="bcp14">MUST</em> also be prepared to resend their requests if the server closes the connection before sending all of the corresponding responses.
    1592       </p>
    1593       <p id="rfc.section.7.1.2.2.p.3">Clients <em class="bcp14">SHOULD NOT</em> pipeline requests using non-idempotent methods or non-idempotent sequences of methods (see <a href="p2-semantics.html#idempotent.methods" title="Idempotent Methods">Section 8.1.2</a> of <a href="#Part2" id="rfc.xref.Part2.11"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>). Otherwise, a premature termination of the transport connection could lead to indeterminate results. A client wishing to
    1594          send a non-idempotent request <em class="bcp14">SHOULD</em> wait to send that request until it has received the response status for the previous request.
    1595       </p>
    1596       <h3 id="rfc.section.7.1.3"><a href="#rfc.section.7.1.3">7.1.3</a>&nbsp;<a id="persistent.proxy" href="#persistent.proxy">Proxy Servers</a></h3>
    1597       <p id="rfc.section.7.1.3.p.1">It is especially important that proxies correctly implement the properties of the Connection header field as specified in <a href="#header.connection" id="rfc.xref.header.connection.3" title="Connection">Section&nbsp;8.1</a>.
    1598       </p>
    1599       <p id="rfc.section.7.1.3.p.2">The proxy server <em class="bcp14">MUST</em> signal persistent connections separately with its clients and the origin servers (or other proxy servers) that it connects
    1600          to. Each persistent connection applies to only one transport link.
    1601       </p>
    1602       <p id="rfc.section.7.1.3.p.3">A proxy server <em class="bcp14">MUST NOT</em> establish a HTTP/1.1 persistent connection with an HTTP/1.0 client (but see <a href="#RFC2068" id="rfc.xref.RFC2068.3"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2068]</cite></a> for information and discussion of the problems with the Keep-Alive header implemented by many HTTP/1.0 clients).
    1603       </p>
    1604       <h3 id="rfc.section.7.1.4"><a href="#rfc.section.7.1.4">7.1.4</a>&nbsp;<a id="persistent.practical" href="#persistent.practical">Practical Considerations</a></h3>
    1605       <p id="rfc.section.7.1.4.p.1">Servers will usually have some time-out value beyond which they will no longer maintain an inactive connection. Proxy servers
    1606          might make this a higher value since it is likely that the client will be making more connections through the same server.
    1607          The use of persistent connections places no requirements on the length (or existence) of this time-out for either the client
    1608          or the server.
    1609       </p>
    1610       <p id="rfc.section.7.1.4.p.2">When a client or server wishes to time-out it <em class="bcp14">SHOULD</em> issue a graceful close on the transport connection. Clients and servers <em class="bcp14">SHOULD</em> both constantly watch for the other side of the transport close, and respond to it as appropriate. If a client or server does
    1611          not detect the other side's close promptly it could cause unnecessary resource drain on the network.
    1612       </p>
    1613       <p id="rfc.section.7.1.4.p.3">A client, server, or proxy <em class="bcp14">MAY</em> close the transport connection at any time. For example, a client might have started to send a new request at the same time
    1614          that the server has decided to close the "idle" connection. From the server's point of view, the connection is being closed
    1615          while it was idle, but from the client's point of view, a request is in progress.
    1616       </p>
    1617       <p id="rfc.section.7.1.4.p.4">This means that clients, servers, and proxies <em class="bcp14">MUST</em> be able to recover from asynchronous close events. Client software <em class="bcp14">SHOULD</em> reopen the transport connection and retransmit the aborted sequence of requests without user interaction so long as the request
    1618          sequence is idempotent (see <a href="p2-semantics.html#idempotent.methods" title="Idempotent Methods">Section 8.1.2</a> of <a href="#Part2" id="rfc.xref.Part2.12"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>). Non-idempotent methods or sequences <em class="bcp14">MUST NOT</em> be automatically retried, although user agents <em class="bcp14">MAY</em> offer a human operator the choice of retrying the request(s). Confirmation by user-agent software with semantic understanding
    1619          of the application <em class="bcp14">MAY</em> substitute for user confirmation. The automatic retry <em class="bcp14">SHOULD NOT</em> be repeated if the second sequence of requests fails.
    1620       </p>
    1621       <p id="rfc.section.7.1.4.p.5">Servers <em class="bcp14">SHOULD</em> always respond to at least one request per connection, if at all possible. Servers <em class="bcp14">SHOULD NOT</em> close a connection in the middle of transmitting a response, unless a network or client failure is suspected.
    1622       </p>
    1623       <p id="rfc.section.7.1.4.p.6">Clients that use persistent connections <em class="bcp14">SHOULD</em> limit the number of simultaneous connections that they maintain to a given server. A single-user client <em class="bcp14">SHOULD NOT</em> maintain more than 2 connections with any server or proxy. A proxy <em class="bcp14">SHOULD</em> use up to 2*N connections to another server or proxy, where N is the number of simultaneously active users. These guidelines
    1624          are intended to improve HTTP response times and avoid congestion.
    1625       </p>
    1626       <h2 id="rfc.section.7.2"><a href="#rfc.section.7.2">7.2</a>&nbsp;<a id="message.transmission.requirements" href="#message.transmission.requirements">Message Transmission Requirements</a></h2>
    1627       <h3 id="rfc.section.7.2.1"><a href="#rfc.section.7.2.1">7.2.1</a>&nbsp;<a id="persistent.flow" href="#persistent.flow">Persistent Connections and Flow Control</a></h3>
    1628       <p id="rfc.section.7.2.1.p.1">HTTP/1.1 servers <em class="bcp14">SHOULD</em> maintain persistent connections and use TCP's flow control mechanisms to resolve temporary overloads, rather than terminating
    1629          connections with the expectation that clients will retry. The latter technique can exacerbate network congestion.
    1630       </p>
    1631       <h3 id="rfc.section.7.2.2"><a href="#rfc.section.7.2.2">7.2.2</a>&nbsp;<a id="persistent.monitor" href="#persistent.monitor">Monitoring Connections for Error Status Messages</a></h3>
    1632       <p id="rfc.section.7.2.2.p.1">An HTTP/1.1 (or later) client sending a message-body <em class="bcp14">SHOULD</em> monitor the network connection for an error status while it is transmitting the request. If the client sees an error status,
    1633          it <em class="bcp14">SHOULD</em> immediately cease transmitting the body. If the body is being sent using a "chunked" encoding (<a href="#transfer.codings" title="Transfer Codings">Section&nbsp;3.4</a>), a zero length chunk and empty trailer <em class="bcp14">MAY</em> be used to prematurely mark the end of the message. If the body was preceded by a Content-Length header, the client <em class="bcp14">MUST</em> close the connection.
    1634       </p>
    1635       <h3 id="rfc.section.7.2.3"><a href="#rfc.section.7.2.3">7.2.3</a>&nbsp;<a id="use.of.the.100.status" href="#use.of.the.100.status">Use of the 100 (Continue) Status</a></h3>
    1636       <p id="rfc.section.7.2.3.p.1">The purpose of the 100 (Continue) status (see <a href="p2-semantics.html#status.100" title="100 Continue">Section 9.1.1</a> of <a href="#Part2" id="rfc.xref.Part2.13"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>) is to allow a client that is sending a request message with a request body to determine if the origin server is willing
    1637          to accept the request (based on the request headers) before the client sends the request body. In some cases, it might either
    1638          be inappropriate or highly inefficient for the client to send the body if the server will reject the message without looking
    1639          at the body.
    1640       </p>
    1641       <p id="rfc.section.7.2.3.p.2">Requirements for HTTP/1.1 clients: </p>
    1642       <ul>
    1643          <li>If a client will wait for a 100 (Continue) response before sending the request body, it <em class="bcp14">MUST</em> send an Expect request-header field (<a href="p2-semantics.html#header.expect" title="Expect">Section 10.2</a> of <a href="#Part2" id="rfc.xref.Part2.14"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>) with the "100-continue" expectation.
    1644          </li>
    1645          <li>A client <em class="bcp14">MUST NOT</em> send an Expect request-header field (<a href="p2-semantics.html#header.expect" title="Expect">Section 10.2</a> of <a href="#Part2" id="rfc.xref.Part2.15"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>) with the "100-continue" expectation if it does not intend to send a request body.
    1646          </li>
    1647       </ul>
    1648       <p id="rfc.section.7.2.3.p.3">Because of the presence of older implementations, the protocol allows ambiguous situations in which a client may send "Expect:
    1649          100-continue" without receiving either a 417 (Expectation Failed) status or a 100 (Continue) status. Therefore, when a client
    1650          sends this header field to an origin server (possibly via a proxy) from which it has never seen a 100 (Continue) status, the
    1651          client <em class="bcp14">SHOULD NOT</em> wait for an indefinite period before sending the request body.
    1652       </p>
    1653       <p id="rfc.section.7.2.3.p.4">Requirements for HTTP/1.1 origin servers: </p>
    1654       <ul>
    1655          <li>Upon receiving a request which includes an Expect request-header field with the "100-continue" expectation, an origin server <em class="bcp14">MUST</em> either respond with 100 (Continue) status and continue to read from the input stream, or respond with a final status code.
    1656             The origin server <em class="bcp14">MUST NOT</em> wait for the request body before sending the 100 (Continue) response. If it responds with a final status code, it <em class="bcp14">MAY</em> close the transport connection or it <em class="bcp14">MAY</em> continue to read and discard the rest of the request. It <em class="bcp14">MUST NOT</em> perform the requested method if it returns a final status code.
    1657          </li>
    1658          <li>An origin server <em class="bcp14">SHOULD NOT</em> send a 100 (Continue) response if the request message does not include an Expect request-header field with the "100-continue"
    1659             expectation, and <em class="bcp14">MUST NOT</em> send a 100 (Continue) response if such a request comes from an HTTP/1.0 (or earlier) client. There is an exception to this
    1660             rule: for compatibility with <a href="#RFC2068" id="rfc.xref.RFC2068.4"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2068]</cite></a>, a server <em class="bcp14">MAY</em> send a 100 (Continue) status in response to an HTTP/1.1 PUT or POST request that does not include an Expect request-header
    1661             field with the "100-continue" expectation. This exception, the purpose of which is to minimize any client processing delays
    1662             associated with an undeclared wait for 100 (Continue) status, applies only to HTTP/1.1 requests, and not to requests with
    1663             any other HTTP-version value.
    1664          </li>
    1665          <li>An origin server <em class="bcp14">MAY</em> omit a 100 (Continue) response if it has already received some or all of the request body for the corresponding request.
    1666          </li>
    1667          <li>An origin server that sends a 100 (Continue) response <em class="bcp14">MUST</em> ultimately send a final status code, once the request body is received and processed, unless it terminates the transport connection
    1668             prematurely.
    1669          </li>
    1670          <li>If an origin server receives a request that does not include an Expect request-header field with the "100-continue" expectation,
    1671             the request includes a request body, and the server responds with a final status code before reading the entire request body
    1672             from the transport connection, then the server <em class="bcp14">SHOULD NOT</em> close the transport connection until it has read the entire request, or until the client closes the connection. Otherwise,
    1673             the client might not reliably receive the response message. However, this requirement is not be construed as preventing a
    1674             server from defending itself against denial-of-service attacks, or from badly broken client implementations.
    1675          </li>
    1676       </ul>
    1677       <p id="rfc.section.7.2.3.p.5">Requirements for HTTP/1.1 proxies: </p>
    1678       <ul>
    1679          <li>If a proxy receives a request that includes an Expect request-header field with the "100-continue" expectation, and the proxy
    1680             either knows that the next-hop server complies with HTTP/1.1 or higher, or does not know the HTTP version of the next-hop
    1681             server, it <em class="bcp14">MUST</em> forward the request, including the Expect header field.
    1682          </li>
    1683          <li>If the proxy knows that the version of the next-hop server is HTTP/1.0 or lower, it <em class="bcp14">MUST NOT</em> forward the request, and it <em class="bcp14">MUST</em> respond with a 417 (Expectation Failed) status.
    1684          </li>
    1685          <li>Proxies <em class="bcp14">SHOULD</em> maintain a cache recording the HTTP version numbers received from recently-referenced next-hop servers.
    1686          </li>
    1687          <li>A proxy <em class="bcp14">MUST NOT</em> forward a 100 (Continue) response if the request message was received from an HTTP/1.0 (or earlier) client and did not include
    1688             an Expect request-header field with the "100-continue" expectation. This requirement overrides the general rule for forwarding
    1689             of 1xx responses (see <a href="p2-semantics.html#status.1xx" title="Informational 1xx">Section 9.1</a> of <a href="#Part2" id="rfc.xref.Part2.16"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>).
    1690          </li>
    1691       </ul>
    1692       <h3 id="rfc.section.7.2.4"><a href="#rfc.section.7.2.4">7.2.4</a>&nbsp;<a id="connection.premature" href="#connection.premature">Client Behavior if Server Prematurely Closes Connection</a></h3>
    1693       <p id="rfc.section.7.2.4.p.1">If an HTTP/1.1 client sends a request which includes a request body, but which does not include an Expect request-header field
    1694          with the "100-continue" expectation, and if the client is not directly connected to an HTTP/1.1 origin server, and if the
    1695          client sees the connection close before receiving any status from the server, the client <em class="bcp14">SHOULD</em> retry the request. If the client does retry this request, it <em class="bcp14">MAY</em> use the following "binary exponential backoff" algorithm to be assured of obtaining a reliable response:
    1696       </p>
    1697       <ol>
    1698          <li>Initiate a new connection to the server</li>
    1699          <li>Transmit the request-headers</li>
    1700          <li>Initialize a variable R to the estimated round-trip time to the server (e.g., based on the time it took to establish the connection),
    1701             or to a constant value of 5 seconds if the round-trip time is not available.
    1702          </li>
    1703          <li>Compute T = R * (2**N), where N is the number of previous retries of this request.</li>
    1704          <li>Wait either for an error response from the server, or for T seconds (whichever comes first)</li>
    1705          <li>If no error response is received, after T seconds transmit the body of the request.</li>
    1706          <li>If client sees that the connection is closed prematurely, repeat from step 1 until the request is accepted, an error response
    1707             is received, or the user becomes impatient and terminates the retry process.
    1708          </li>
    1709       </ol>
    1710       <p id="rfc.section.7.2.4.p.2">If at any point an error status is received, the client </p>
    1711       <ul>
    1712          <li><em class="bcp14">SHOULD NOT</em> continue and
    1713          </li>
    1714          <li><em class="bcp14">SHOULD</em> close the connection if it has not completed sending the request message.
    1715          </li>
    1716       </ul>
    1717       <h1 id="rfc.section.8"><a href="#rfc.section.8">8.</a>&nbsp;<a id="header.fields" href="#header.fields">Header Field Definitions</a></h1>
    1718       <p id="rfc.section.8.p.1">This section defines the syntax and semantics of HTTP/1.1 header fields related to message framing and transport protocols.</p>
    1719       <p id="rfc.section.8.p.2">For entity-header fields, both sender and recipient refer to either the client or the server, depending on who sends and who
    1720          receives the entity.
    1721       </p>
    1722       <div id="rfc.iref.c.6"></div>
    1723       <div id="rfc.iref.h.1"></div>
    1724       <h2 id="rfc.section.8.1"><a href="#rfc.section.8.1">8.1</a>&nbsp;<a id="header.connection" href="#header.connection">Connection</a></h2>
    1725       <p id="rfc.section.8.1.p.1">The Connection general-header field allows the sender to specify options that are desired for that particular connection and <em class="bcp14">MUST NOT</em> be communicated by proxies over further connections.
    1726       </p>
    1727       <p id="rfc.section.8.1.p.2">The Connection header has the following grammar:</p>
    1728       <div id="rfc.figure.u.45"></div><pre class="inline"><span id="rfc.iref.g.82"></span><span id="rfc.iref.g.83"></span>  <a href="#header.connection" class="smpl">Connection</a> = "Connection" ":" 1#(<a href="#header.connection" class="smpl">connection-token</a>)
     1609</pre></div>
     1610         </div>
     1611      </div>
     1612      <div id="connections">
     1613         <h1 id="rfc.section.7"><a href="#rfc.section.7">7.</a>&nbsp;<a href="#connections">Connections</a></h1>
     1614         <div id="persistent.connections">
     1615            <h2 id="rfc.section.7.1"><a href="#rfc.section.7.1">7.1</a>&nbsp;<a href="#persistent.connections">Persistent Connections</a></h2>
     1616            <div id="persistent.purpose">
     1617               <h3 id="rfc.section.7.1.1"><a href="#rfc.section.7.1.1">7.1.1</a>&nbsp;<a href="#persistent.purpose">Purpose</a></h3>
     1618               <p id="rfc.section.7.1.1.p.1">Prior to persistent connections, a separate TCP connection was established to fetch each URL, increasing the load on HTTP
     1619                  servers and causing congestion on the Internet. The use of inline images and other associated data often require a client
     1620                  to make multiple requests of the same server in a short amount of time. Analysis of these performance problems and results
     1621                  from a prototype implementation are available <a href="#Pad1995" id="rfc.xref.Pad1995.1"><cite title="Improving HTTP Latency">[Pad1995]</cite></a> <a href="#Spe" id="rfc.xref.Spe.1"><cite title="Analysis of HTTP Performance Problems">[Spe]</cite></a>. Implementation experience and measurements of actual HTTP/1.1 (<cite title="Hypertext Transfer Protocol -- HTTP/1.1" id="rfc.xref.RFC2068.2">RFC 2068</cite>) implementations show good results <a href="#Nie1997" id="rfc.xref.Nie1997.1"><cite title="Network Performance Effects of HTTP/1.1, CSS1, and PNG">[Nie1997]</cite></a>. Alternatives have also been explored, for example, T/TCP <a href="#Tou1998" id="rfc.xref.Tou1998.1"><cite title="Analysis of HTTP Performance">[Tou1998]</cite></a>.
     1622               </p>
     1623               <p id="rfc.section.7.1.1.p.2">Persistent HTTP connections have a number of advantages: </p>
     1624               <ul>
     1625                  <li>By opening and closing fewer TCP connections, CPU time is saved in routers and hosts (clients, servers, proxies, gateways,
     1626                     tunnels, or caches), and memory used for TCP protocol control blocks can be saved in hosts.
     1627                  </li>
     1628                  <li>HTTP requests and responses can be pipelined on a connection. Pipelining allows a client to make multiple requests without
     1629                     waiting for each response, allowing a single TCP connection to be used much more efficiently, with much lower elapsed time.
     1630                  </li>
     1631                  <li>Network congestion is reduced by reducing the number of packets caused by TCP opens, and by allowing TCP sufficient time to
     1632                     determine the congestion state of the network.
     1633                  </li>
     1634                  <li>Latency on subsequent requests is reduced since there is no time spent in TCP's connection opening handshake.</li>
     1635                  <li>HTTP can evolve more gracefully, since errors can be reported without the penalty of closing the TCP connection. Clients using
     1636                     future versions of HTTP might optimistically try a new feature, but if communicating with an older server, retry with old
     1637                     semantics after an error is reported.
     1638                  </li>
     1639               </ul>
     1640               <p id="rfc.section.7.1.1.p.3">HTTP implementations <em class="bcp14">SHOULD</em> implement persistent connections.
     1641               </p>
     1642            </div>
     1643            <div id="persistent.overall">
     1644               <h3 id="rfc.section.7.1.2"><a href="#rfc.section.7.1.2">7.1.2</a>&nbsp;<a href="#persistent.overall">Overall Operation</a></h3>
     1645               <p id="rfc.section.7.1.2.p.1">A significant difference between HTTP/1.1 and earlier versions of HTTP is that persistent connections are the default behavior
     1646                  of any HTTP connection. That is, unless otherwise indicated, the client <em class="bcp14">SHOULD</em> assume that the server will maintain a persistent connection, even after error responses from the server.
     1647               </p>
     1648               <p id="rfc.section.7.1.2.p.2">Persistent connections provide a mechanism by which a client and a server can signal the close of a TCP connection. This signaling
     1649                  takes place using the Connection header field (<a href="#header.connection" id="rfc.xref.header.connection.2" title="Connection">Section&nbsp;8.1</a>). Once a close has been signaled, the client <em class="bcp14">MUST NOT</em> send any more requests on that connection.
     1650               </p>
     1651               <div id="persistent.negotiation">
     1652                  <h4 id="rfc.section.7.1.2.1"><a href="#rfc.section.7.1.2.1">7.1.2.1</a>&nbsp;<a href="#persistent.negotiation">Negotiation</a></h4>
     1653                  <p id="rfc.section.7.1.2.1.p.1">An HTTP/1.1 server <em class="bcp14">MAY</em> assume that a HTTP/1.1 client intends to maintain a persistent connection unless a Connection header including the connection-token
     1654                     "close" was sent in the request. If the server chooses to close the connection immediately after sending the response, it <em class="bcp14">SHOULD</em> send a Connection header including the connection-token close.
     1655                  </p>
     1656                  <p id="rfc.section.7.1.2.1.p.2">An HTTP/1.1 client <em class="bcp14">MAY</em> expect a connection to remain open, but would decide to keep it open based on whether the response from a server contains
     1657                     a Connection header with the connection-token close. In case the client does not want to maintain a connection for more than
     1658                     that request, it <em class="bcp14">SHOULD</em> send a Connection header including the connection-token close.
     1659                  </p>
     1660                  <p id="rfc.section.7.1.2.1.p.3">If either the client or the server sends the close token in the Connection header, that request becomes the last one for the
     1661                     connection.
     1662                  </p>
     1663                  <p id="rfc.section.7.1.2.1.p.4">Clients and servers <em class="bcp14">SHOULD NOT</em> assume that a persistent connection is maintained for HTTP versions less than 1.1 unless it is explicitly signaled. See <a href="#compatibility.with.http.1.0.persistent.connections" title="Compatibility with HTTP/1.0 Persistent Connections">Appendix&nbsp;D.2</a> for more information on backward compatibility with HTTP/1.0 clients.
     1664                  </p>
     1665                  <p id="rfc.section.7.1.2.1.p.5">In order to remain persistent, all messages on the connection <em class="bcp14">MUST</em> have a self-defined message length (i.e., one not defined by closure of the connection), as described in <a href="#message.length" title="Message Length">Section&nbsp;4.4</a>.
     1666                  </p>
     1667               </div>
     1668               <div id="pipelining">
     1669                  <h4 id="rfc.section.7.1.2.2"><a href="#rfc.section.7.1.2.2">7.1.2.2</a>&nbsp;<a href="#pipelining">Pipelining</a></h4>
     1670                  <p id="rfc.section.7.1.2.2.p.1">A client that supports persistent connections <em class="bcp14">MAY</em> "pipeline" its requests (i.e., send multiple requests without waiting for each response). A server <em class="bcp14">MUST</em> send its responses to those requests in the same order that the requests were received.
     1671                  </p>
     1672                  <p id="rfc.section.7.1.2.2.p.2">Clients which assume persistent connections and pipeline immediately after connection establishment <em class="bcp14">SHOULD</em> be prepared to retry their connection if the first pipelined attempt fails. If a client does such a retry, it <em class="bcp14">MUST NOT</em> pipeline before it knows the connection is persistent. Clients <em class="bcp14">MUST</em> also be prepared to resend their requests if the server closes the connection before sending all of the corresponding responses.
     1673                  </p>
     1674                  <p id="rfc.section.7.1.2.2.p.3">Clients <em class="bcp14">SHOULD NOT</em> pipeline requests using non-idempotent methods or non-idempotent sequences of methods (see <a href="p2-semantics.html#idempotent.methods" title="Idempotent Methods">Section 8.1.2</a> of <a href="#Part2" id="rfc.xref.Part2.11"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>). Otherwise, a premature termination of the transport connection could lead to indeterminate results. A client wishing to
     1675                     send a non-idempotent request <em class="bcp14">SHOULD</em> wait to send that request until it has received the response status for the previous request.
     1676                  </p>
     1677               </div>
     1678            </div>
     1679            <div id="persistent.proxy">
     1680               <h3 id="rfc.section.7.1.3"><a href="#rfc.section.7.1.3">7.1.3</a>&nbsp;<a href="#persistent.proxy">Proxy Servers</a></h3>
     1681               <p id="rfc.section.7.1.3.p.1">It is especially important that proxies correctly implement the properties of the Connection header field as specified in <a href="#header.connection" id="rfc.xref.header.connection.3" title="Connection">Section&nbsp;8.1</a>.
     1682               </p>
     1683               <p id="rfc.section.7.1.3.p.2">The proxy server <em class="bcp14">MUST</em> signal persistent connections separately with its clients and the origin servers (or other proxy servers) that it connects
     1684                  to. Each persistent connection applies to only one transport link.
     1685               </p>
     1686               <p id="rfc.section.7.1.3.p.3">A proxy server <em class="bcp14">MUST NOT</em> establish a HTTP/1.1 persistent connection with an HTTP/1.0 client (but see <a href="#RFC2068" id="rfc.xref.RFC2068.3"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2068]</cite></a> for information and discussion of the problems with the Keep-Alive header implemented by many HTTP/1.0 clients).
     1687               </p>
     1688            </div>
     1689            <div id="persistent.practical">
     1690               <h3 id="rfc.section.7.1.4"><a href="#rfc.section.7.1.4">7.1.4</a>&nbsp;<a href="#persistent.practical">Practical Considerations</a></h3>
     1691               <p id="rfc.section.7.1.4.p.1">Servers will usually have some time-out value beyond which they will no longer maintain an inactive connection. Proxy servers
     1692                  might make this a higher value since it is likely that the client will be making more connections through the same server.
     1693                  The use of persistent connections places no requirements on the length (or existence) of this time-out for either the client
     1694                  or the server.
     1695               </p>
     1696               <p id="rfc.section.7.1.4.p.2">When a client or server wishes to time-out it <em class="bcp14">SHOULD</em> issue a graceful close on the transport connection. Clients and servers <em class="bcp14">SHOULD</em> both constantly watch for the other side of the transport close, and respond to it as appropriate. If a client or server does
     1697                  not detect the other side's close promptly it could cause unnecessary resource drain on the network.
     1698               </p>
     1699               <p id="rfc.section.7.1.4.p.3">A client, server, or proxy <em class="bcp14">MAY</em> close the transport connection at any time. For example, a client might have started to send a new request at the same time
     1700                  that the server has decided to close the "idle" connection. From the server's point of view, the connection is being closed
     1701                  while it was idle, but from the client's point of view, a request is in progress.
     1702               </p>
     1703               <p id="rfc.section.7.1.4.p.4">This means that clients, servers, and proxies <em class="bcp14">MUST</em> be able to recover from asynchronous close events. Client software <em class="bcp14">SHOULD</em> reopen the transport connection and retransmit the aborted sequence of requests without user interaction so long as the request
     1704                  sequence is idempotent (see <a href="p2-semantics.html#idempotent.methods" title="Idempotent Methods">Section 8.1.2</a> of <a href="#Part2" id="rfc.xref.Part2.12"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>). Non-idempotent methods or sequences <em class="bcp14">MUST NOT</em> be automatically retried, although user agents <em class="bcp14">MAY</em> offer a human operator the choice of retrying the request(s). Confirmation by user-agent software with semantic understanding
     1705                  of the application <em class="bcp14">MAY</em> substitute for user confirmation. The automatic retry <em class="bcp14">SHOULD NOT</em> be repeated if the second sequence of requests fails.
     1706               </p>
     1707               <p id="rfc.section.7.1.4.p.5">Servers <em class="bcp14">SHOULD</em> always respond to at least one request per connection, if at all possible. Servers <em class="bcp14">SHOULD NOT</em> close a connection in the middle of transmitting a response, unless a network or client failure is suspected.
     1708               </p>
     1709               <p id="rfc.section.7.1.4.p.6">Clients that use persistent connections <em class="bcp14">SHOULD</em> limit the number of simultaneous connections that they maintain to a given server. A single-user client <em class="bcp14">SHOULD NOT</em> maintain more than 2 connections with any server or proxy. A proxy <em class="bcp14">SHOULD</em> use up to 2*N connections to another server or proxy, where N is the number of simultaneously active users. These guidelines
     1710                  are intended to improve HTTP response times and avoid congestion.
     1711               </p>
     1712            </div>
     1713         </div>
     1714         <div id="message.transmission.requirements">
     1715            <h2 id="rfc.section.7.2"><a href="#rfc.section.7.2">7.2</a>&nbsp;<a href="#message.transmission.requirements">Message Transmission Requirements</a></h2>
     1716            <div id="persistent.flow">
     1717               <h3 id="rfc.section.7.2.1"><a href="#rfc.section.7.2.1">7.2.1</a>&nbsp;<a href="#persistent.flow">Persistent Connections and Flow Control</a></h3>
     1718               <p id="rfc.section.7.2.1.p.1">HTTP/1.1 servers <em class="bcp14">SHOULD</em> maintain persistent connections and use TCP's flow control mechanisms to resolve temporary overloads, rather than terminating
     1719                  connections with the expectation that clients will retry. The latter technique can exacerbate network congestion.
     1720               </p>
     1721            </div>
     1722            <div id="persistent.monitor">
     1723               <h3 id="rfc.section.7.2.2"><a href="#rfc.section.7.2.2">7.2.2</a>&nbsp;<a href="#persistent.monitor">Monitoring Connections for Error Status Messages</a></h3>
     1724               <p id="rfc.section.7.2.2.p.1">An HTTP/1.1 (or later) client sending a message-body <em class="bcp14">SHOULD</em> monitor the network connection for an error status while it is transmitting the request. If the client sees an error status,
     1725                  it <em class="bcp14">SHOULD</em> immediately cease transmitting the body. If the body is being sent using a "chunked" encoding (<a href="#transfer.codings" title="Transfer Codings">Section&nbsp;3.4</a>), a zero length chunk and empty trailer <em class="bcp14">MAY</em> be used to prematurely mark the end of the message. If the body was preceded by a Content-Length header, the client <em class="bcp14">MUST</em> close the connection.
     1726               </p>
     1727            </div>
     1728            <div id="use.of.the.100.status">
     1729               <h3 id="rfc.section.7.2.3"><a href="#rfc.section.7.2.3">7.2.3</a>&nbsp;<a href="#use.of.the.100.status">Use of the 100 (Continue) Status</a></h3>
     1730               <p id="rfc.section.7.2.3.p.1">The purpose of the 100 (Continue) status (see <a href="p2-semantics.html#status.100" title="100 Continue">Section 9.1.1</a> of <a href="#Part2" id="rfc.xref.Part2.13"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>) is to allow a client that is sending a request message with a request body to determine if the origin server is willing
     1731                  to accept the request (based on the request headers) before the client sends the request body. In some cases, it might either
     1732                  be inappropriate or highly inefficient for the client to send the body if the server will reject the message without looking
     1733                  at the body.
     1734               </p>
     1735               <p id="rfc.section.7.2.3.p.2">Requirements for HTTP/1.1 clients: </p>
     1736               <ul>
     1737                  <li>If a client will wait for a 100 (Continue) response before sending the request body, it <em class="bcp14">MUST</em> send an Expect request-header field (<a href="p2-semantics.html#header.expect" title="Expect">Section 10.2</a> of <a href="#Part2" id="rfc.xref.Part2.14"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>) with the "100-continue" expectation.
     1738                  </li>
     1739                  <li>A client <em class="bcp14">MUST NOT</em> send an Expect request-header field (<a href="p2-semantics.html#header.expect" title="Expect">Section 10.2</a> of <a href="#Part2" id="rfc.xref.Part2.15"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>) with the "100-continue" expectation if it does not intend to send a request body.
     1740                  </li>
     1741               </ul>
     1742               <p id="rfc.section.7.2.3.p.3">Because of the presence of older implementations, the protocol allows ambiguous situations in which a client may send "Expect:
     1743                  100-continue" without receiving either a 417 (Expectation Failed) status or a 100 (Continue) status. Therefore, when a client
     1744                  sends this header field to an origin server (possibly via a proxy) from which it has never seen a 100 (Continue) status, the
     1745                  client <em class="bcp14">SHOULD NOT</em> wait for an indefinite period before sending the request body.
     1746               </p>
     1747               <p id="rfc.section.7.2.3.p.4">Requirements for HTTP/1.1 origin servers: </p>
     1748               <ul>
     1749                  <li>Upon receiving a request which includes an Expect request-header field with the "100-continue" expectation, an origin server <em class="bcp14">MUST</em> either respond with 100 (Continue) status and continue to read from the input stream, or respond with a final status code.
     1750                     The origin server <em class="bcp14">MUST NOT</em> wait for the request body before sending the 100 (Continue) response. If it responds with a final status code, it <em class="bcp14">MAY</em> close the transport connection or it <em class="bcp14">MAY</em> continue to read and discard the rest of the request. It <em class="bcp14">MUST NOT</em> perform the requested method if it returns a final status code.
     1751                  </li>
     1752                  <li>An origin server <em class="bcp14">SHOULD NOT</em> send a 100 (Continue) response if the request message does not include an Expect request-header field with the "100-continue"
     1753                     expectation, and <em class="bcp14">MUST NOT</em> send a 100 (Continue) response if such a request comes from an HTTP/1.0 (or earlier) client. There is an exception to this
     1754                     rule: for compatibility with <a href="#RFC2068" id="rfc.xref.RFC2068.4"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2068]</cite></a>, a server <em class="bcp14">MAY</em> send a 100 (Continue) status in response to an HTTP/1.1 PUT or POST request that does not include an Expect request-header
     1755                     field with the "100-continue" expectation. This exception, the purpose of which is to minimize any client processing delays
     1756                     associated with an undeclared wait for 100 (Continue) status, applies only to HTTP/1.1 requests, and not to requests with
     1757                     any other HTTP-version value.
     1758                  </li>
     1759                  <li>An origin server <em class="bcp14">MAY</em> omit a 100 (Continue) response if it has already received some or all of the request body for the corresponding request.
     1760                  </li>
     1761                  <li>An origin server that sends a 100 (Continue) response <em class="bcp14">MUST</em> ultimately send a final status code, once the request body is received and processed, unless it terminates the transport connection
     1762                     prematurely.
     1763                  </li>
     1764                  <li>If an origin server receives a request that does not include an Expect request-header field with the "100-continue" expectation,
     1765                     the request includes a request body, and the server responds with a final status code before reading the entire request body
     1766                     from the transport connection, then the server <em class="bcp14">SHOULD NOT</em> close the transport connection until it has read the entire request, or until the client closes the connection. Otherwise,
     1767                     the client might not reliably receive the response message. However, this requirement is not be construed as preventing a
     1768                     server from defending itself against denial-of-service attacks, or from badly broken client implementations.
     1769                  </li>
     1770               </ul>
     1771               <p id="rfc.section.7.2.3.p.5">Requirements for HTTP/1.1 proxies: </p>
     1772               <ul>
     1773                  <li>If a proxy receives a request that includes an Expect request-header field with the "100-continue" expectation, and the proxy
     1774                     either knows that the next-hop server complies with HTTP/1.1 or higher, or does not know the HTTP version of the next-hop
     1775                     server, it <em class="bcp14">MUST</em> forward the request, including the Expect header field.
     1776                  </li>
     1777                  <li>If the proxy knows that the version of the next-hop server is HTTP/1.0 or lower, it <em class="bcp14">MUST NOT</em> forward the request, and it <em class="bcp14">MUST</em> respond with a 417 (Expectation Failed) status.
     1778                  </li>
     1779                  <li>Proxies <em class="bcp14">SHOULD</em> maintain a cache recording the HTTP version numbers received from recently-referenced next-hop servers.
     1780                  </li>
     1781                  <li>A proxy <em class="bcp14">MUST NOT</em> forward a 100 (Continue) response if the request message was received from an HTTP/1.0 (or earlier) client and did not include
     1782                     an Expect request-header field with the "100-continue" expectation. This requirement overrides the general rule for forwarding
     1783                     of 1xx responses (see <a href="p2-semantics.html#status.1xx" title="Informational 1xx">Section 9.1</a> of <a href="#Part2" id="rfc.xref.Part2.16"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>).
     1784                  </li>
     1785               </ul>
     1786            </div>
     1787            <div id="connection.premature">
     1788               <h3 id="rfc.section.7.2.4"><a href="#rfc.section.7.2.4">7.2.4</a>&nbsp;<a href="#connection.premature">Client Behavior if Server Prematurely Closes Connection</a></h3>
     1789               <p id="rfc.section.7.2.4.p.1">If an HTTP/1.1 client sends a request which includes a request body, but which does not include an Expect request-header field
     1790                  with the "100-continue" expectation, and if the client is not directly connected to an HTTP/1.1 origin server, and if the
     1791                  client sees the connection close before receiving any status from the server, the client <em class="bcp14">SHOULD</em> retry the request. If the client does retry this request, it <em class="bcp14">MAY</em> use the following "binary exponential backoff" algorithm to be assured of obtaining a reliable response:
     1792               </p>
     1793               <ol>
     1794                  <li>Initiate a new connection to the server</li>
     1795                  <li>Transmit the request-headers</li>
     1796                  <li>Initialize a variable R to the estimated round-trip time to the server (e.g., based on the time it took to establish the connection),
     1797                     or to a constant value of 5 seconds if the round-trip time is not available.
     1798                  </li>
     1799                  <li>Compute T = R * (2**N), where N is the number of previous retries of this request.</li>
     1800                  <li>Wait either for an error response from the server, or for T seconds (whichever comes first)</li>
     1801                  <li>If no error response is received, after T seconds transmit the body of the request.</li>
     1802                  <li>If client sees that the connection is closed prematurely, repeat from step 1 until the request is accepted, an error response
     1803                     is received, or the user becomes impatient and terminates the retry process.
     1804                  </li>
     1805               </ol>
     1806               <p id="rfc.section.7.2.4.p.2">If at any point an error status is received, the client </p>
     1807               <ul>
     1808                  <li><em class="bcp14">SHOULD NOT</em> continue and
     1809                  </li>
     1810                  <li><em class="bcp14">SHOULD</em> close the connection if it has not completed sending the request message.
     1811                  </li>
     1812               </ul>
     1813            </div>
     1814         </div>
     1815      </div>
     1816      <div id="header.fields">
     1817         <h1 id="rfc.section.8"><a href="#rfc.section.8">8.</a>&nbsp;<a href="#header.fields">Header Field Definitions</a></h1>
     1818         <p id="rfc.section.8.p.1">This section defines the syntax and semantics of HTTP/1.1 header fields related to message framing and transport protocols.</p>
     1819         <p id="rfc.section.8.p.2">For entity-header fields, both sender and recipient refer to either the client or the server, depending on who sends and who
     1820            receives the entity.
     1821         </p>
     1822         <div id="header.connection">
     1823            <div id="rfc.iref.c.6"></div>
     1824            <div id="rfc.iref.h.1"></div>
     1825            <h2 id="rfc.section.8.1"><a href="#rfc.section.8.1">8.1</a>&nbsp;<a href="#header.connection">Connection</a></h2>
     1826            <p id="rfc.section.8.1.p.1">The Connection general-header field allows the sender to specify options that are desired for that particular connection and <em class="bcp14">MUST NOT</em> be communicated by proxies over further connections.
     1827            </p>
     1828            <p id="rfc.section.8.1.p.2">The Connection header has the following grammar:</p>
     1829            <div id="rfc.figure.u.45"></div><pre class="inline"><span id="rfc.iref.g.82"></span><span id="rfc.iref.g.83"></span>  <a href="#header.connection" class="smpl">Connection</a> = "Connection" ":" 1#(<a href="#header.connection" class="smpl">connection-token</a>)
    17291830  <a href="#header.connection" class="smpl">connection-token</a>  = <a href="#rule.token.separators" class="smpl">token</a>
    17301831</pre><p id="rfc.section.8.1.p.4">HTTP/1.1 proxies <em class="bcp14">MUST</em> parse the Connection header field before a message is forwarded and, for each connection-token in this field, remove any header
    1731          field(s) from the message with the same name as the connection-token. Connection options are signaled by the presence of a
    1732          connection-token in the Connection header field, not by any corresponding additional header field(s), since the additional
    1733          header field may not be sent if there are no parameters associated with that connection option.
    1734       </p>
    1735       <p id="rfc.section.8.1.p.5">Message headers listed in the Connection header <em class="bcp14">MUST NOT</em> include end-to-end headers, such as Cache-Control.
    1736       </p>
    1737       <p id="rfc.section.8.1.p.6">HTTP/1.1 defines the "close" connection option for the sender to signal that the connection will be closed after completion
    1738          of the response. For example,
    1739       </p>
    1740       <div id="rfc.figure.u.46"></div><pre class="text">    Connection: close
     1832               field(s) from the message with the same name as the connection-token. Connection options are signaled by the presence of a
     1833               connection-token in the Connection header field, not by any corresponding additional header field(s), since the additional
     1834               header field may not be sent if there are no parameters associated with that connection option.
     1835            </p>
     1836            <p id="rfc.section.8.1.p.5">Message headers listed in the Connection header <em class="bcp14">MUST NOT</em> include end-to-end headers, such as Cache-Control.
     1837            </p>
     1838            <p id="rfc.section.8.1.p.6">HTTP/1.1 defines the "close" connection option for the sender to signal that the connection will be closed after completion
     1839               of the response. For example,
     1840            </p>
     1841            <div id="rfc.figure.u.46"></div><pre class="text">    Connection: close
    17411842</pre><p id="rfc.section.8.1.p.8">in either the request or the response header fields indicates that the connection <em class="bcp14">SHOULD NOT</em> be considered `persistent' (<a href="#persistent.connections" title="Persistent Connections">Section&nbsp;7.1</a>) after the current request/response is complete.
    1742       </p>
    1743       <p id="rfc.section.8.1.p.9">An HTTP/1.1 client that does not support persistent connections <em class="bcp14">MUST</em> include the "close" connection option in every request message.
    1744       </p>
    1745       <p id="rfc.section.8.1.p.10">An HTTP/1.1 server that does not support persistent connections <em class="bcp14">MUST</em> include the "close" connection option in every response message that does not have a 1xx (informational) status code.
    1746       </p>
    1747       <p id="rfc.section.8.1.p.11">A system receiving an HTTP/1.0 (or lower-version) message that includes a Connection header <em class="bcp14">MUST</em>, for each connection-token in this field, remove and ignore any header field(s) from the message with the same name as the
    1748          connection-token. This protects against mistaken forwarding of such header fields by pre-HTTP/1.1 proxies. See <a href="#compatibility.with.http.1.0.persistent.connections" title="Compatibility with HTTP/1.0 Persistent Connections">Appendix&nbsp;D.2</a>.
    1749       </p>
    1750       <div id="rfc.iref.c.7"></div>
    1751       <div id="rfc.iref.h.2"></div>
    1752       <h2 id="rfc.section.8.2"><a href="#rfc.section.8.2">8.2</a>&nbsp;<a id="header.content-length" href="#header.content-length">Content-Length</a></h2>
    1753       <p id="rfc.section.8.2.p.1">The Content-Length entity-header field indicates the size of the entity-body, in decimal number of OCTETs, sent to the recipient
    1754          or, in the case of the HEAD method, the size of the entity-body that would have been sent had the request been a GET.
    1755       </p>
    1756       <div id="rfc.figure.u.47"></div><pre class="inline"><span id="rfc.iref.g.84"></span>  <a href="#header.content-length" class="smpl">Content-Length</a>    = "Content-Length" ":" 1*<a href="#core.rules" class="smpl">DIGIT</a>
     1843            </p>
     1844            <p id="rfc.section.8.1.p.9">An HTTP/1.1 client that does not support persistent connections <em class="bcp14">MUST</em> include the "close" connection option in every request message.
     1845            </p>
     1846            <p id="rfc.section.8.1.p.10">An HTTP/1.1 server that does not support persistent connections <em class="bcp14">MUST</em> include the "close" connection option in every response message that does not have a 1xx (informational) status code.
     1847            </p>
     1848            <p id="rfc.section.8.1.p.11">A system receiving an HTTP/1.0 (or lower-version) message that includes a Connection header <em class="bcp14">MUST</em>, for each connection-token in this field, remove and ignore any header field(s) from the message with the same name as the
     1849               connection-token. This protects against mistaken forwarding of such header fields by pre-HTTP/1.1 proxies. See <a href="#compatibility.with.http.1.0.persistent.connections" title="Compatibility with HTTP/1.0 Persistent Connections">Appendix&nbsp;D.2</a>.
     1850            </p>
     1851         </div>
     1852         <div id="header.content-length">
     1853            <div id="rfc.iref.c.7"></div>
     1854            <div id="rfc.iref.h.2"></div>
     1855            <h2 id="rfc.section.8.2"><a href="#rfc.section.8.2">8.2</a>&nbsp;<a href="#header.content-length">Content-Length</a></h2>
     1856            <p id="rfc.section.8.2.p.1">The Content-Length entity-header field indicates the size of the entity-body, in decimal number of OCTETs, sent to the recipient
     1857               or, in the case of the HEAD method, the size of the entity-body that would have been sent had the request been a GET.
     1858            </p>
     1859            <div id="rfc.figure.u.47"></div><pre class="inline"><span id="rfc.iref.g.84"></span>  <a href="#header.content-length" class="smpl">Content-Length</a>    = "Content-Length" ":" 1*<a href="#core.rules" class="smpl">DIGIT</a>
    17571860</pre><p id="rfc.section.8.2.p.3">An example is</p>
    1758       <div id="rfc.figure.u.48"></div><pre class="text">    Content-Length: 3495
     1861            <div id="rfc.figure.u.48"></div><pre class="text">    Content-Length: 3495
    17591862</pre><p id="rfc.section.8.2.p.5">Applications <em class="bcp14">SHOULD</em> use this field to indicate the transfer-length of the message-body, unless this is prohibited by the rules in <a href="#message.length" title="Message Length">Section&nbsp;4.4</a>.
    1760       </p>
    1761       <p id="rfc.section.8.2.p.6">Any Content-Length greater than or equal to zero is a valid value. <a href="#message.length" title="Message Length">Section&nbsp;4.4</a> describes how to determine the length of a message-body if a Content-Length is not given.
    1762       </p>
    1763       <p id="rfc.section.8.2.p.7">Note that the meaning of this field is significantly different from the corresponding definition in MIME, where it is an optional
    1764          field used within the "message/external-body" content-type. In HTTP, it <em class="bcp14">SHOULD</em> be sent whenever the message's length can be determined prior to being transferred, unless this is prohibited by the rules
    1765          in <a href="#message.length" title="Message Length">Section&nbsp;4.4</a>.
    1766       </p>
    1767       <div id="rfc.iref.d.2"></div>
    1768       <div id="rfc.iref.h.3"></div>
    1769       <h2 id="rfc.section.8.3"><a href="#rfc.section.8.3">8.3</a>&nbsp;<a id="header.date" href="#header.date">Date</a></h2>
    1770       <p id="rfc.section.8.3.p.1">The Date general-header field represents the date and time at which the message was originated, having the same semantics
    1771          as orig-date in <a href="http://tools.ietf.org/html/rfc2822#section-3.6.1">Section 3.6.1</a> of <a href="#RFC2822" id="rfc.xref.RFC2822.4"><cite title="Internet Message Format">[RFC2822]</cite></a>. The field value is an HTTP-date, as described in <a href="#full.date" title="Full Date">Section&nbsp;3.3.1</a>; it <em class="bcp14">MUST</em> be sent in rfc1123-date format.
    1772       </p>
    1773       <div id="rfc.figure.u.49"></div><pre class="inline"><span id="rfc.iref.g.85"></span>  <a href="#header.date" class="smpl">Date</a>  = "Date" ":" <a href="#full.date" class="smpl">HTTP-date</a>
     1863            </p>
     1864            <p id="rfc.section.8.2.p.6">Any Content-Length greater than or equal to zero is a valid value. <a href="#message.length" title="Message Length">Section&nbsp;4.4</a> describes how to determine the length of a message-body if a Content-Length is not given.
     1865            </p>
     1866            <p id="rfc.section.8.2.p.7">Note that the meaning of this field is significantly different from the corresponding definition in MIME, where it is an optional
     1867               field used within the "message/external-body" content-type. In HTTP, it <em class="bcp14">SHOULD</em> be sent whenever the message's length can be determined prior to being transferred, unless this is prohibited by the rules
     1868               in <a href="#message.length" title="Message Length">Section&nbsp;4.4</a>.
     1869            </p>
     1870         </div>
     1871         <div id="header.date">
     1872            <div id="rfc.iref.d.2"></div>
     1873            <div id="rfc.iref.h.3"></div>
     1874            <h2 id="rfc.section.8.3"><a href="#rfc.section.8.3">8.3</a>&nbsp;<a href="#header.date">Date</a></h2>
     1875            <p id="rfc.section.8.3.p.1">The Date general-header field represents the date and time at which the message was originated, having the same semantics
     1876               as orig-date in <a href="https://tools.ietf.org/html/rfc2822#section-3.6.1">Section 3.6.1</a> of <a href="#RFC2822" id="rfc.xref.RFC2822.4"><cite title="Internet Message Format">[RFC2822]</cite></a>. The field value is an HTTP-date, as described in <a href="#full.date" title="Full Date">Section&nbsp;3.3.1</a>; it <em class="bcp14">MUST</em> be sent in rfc1123-date format.
     1877            </p>
     1878            <div id="rfc.figure.u.49"></div><pre class="inline"><span id="rfc.iref.g.85"></span>  <a href="#header.date" class="smpl">Date</a>  = "Date" ":" <a href="#full.date" class="smpl">HTTP-date</a>
    17741879</pre><p id="rfc.section.8.3.p.3">An example is</p>
    1775       <div id="rfc.figure.u.50"></div><pre class="text">    Date: Tue, 15 Nov 1994 08:12:31 GMT
     1880            <div id="rfc.figure.u.50"></div><pre class="text">    Date: Tue, 15 Nov 1994 08:12:31 GMT
    17761881</pre><p id="rfc.section.8.3.p.5">Origin servers <em class="bcp14">MUST</em> include a Date header field in all responses, except in these cases:
    1777       </p>
    1778       <ol>
    1779          <li>If the response status code is 100 (Continue) or 101 (Switching Protocols), the response <em class="bcp14">MAY</em> include a Date header field, at the server's option.
    1780          </li>
    1781          <li>If the response status code conveys a server error, e.g. 500 (Internal Server Error) or 503 (Service Unavailable), and it
    1782             is inconvenient or impossible to generate a valid Date.
    1783          </li>
    1784          <li>If the server does not have a clock that can provide a reasonable approximation of the current time, its responses <em class="bcp14">MUST NOT</em> include a Date header field. In this case, the rules in <a href="#clockless.origin.server.operation" title="Clockless Origin Server Operation">Section&nbsp;8.3.1</a>  <em class="bcp14">MUST</em> be followed.
    1785          </li>
    1786       </ol>
    1787       <p id="rfc.section.8.3.p.6">A received message that does not have a Date header field <em class="bcp14">MUST</em> be assigned one by the recipient if the message will be cached by that recipient or gatewayed via a protocol which requires
    1788          a Date. An HTTP implementation without a clock <em class="bcp14">MUST NOT</em> cache responses without revalidating them on every use. An HTTP cache, especially a shared cache, <em class="bcp14">SHOULD</em> use a mechanism, such as NTP <a href="#RFC1305" id="rfc.xref.RFC1305.1"><cite title="Network Time Protocol (Version 3) Specification, Implementation">[RFC1305]</cite></a>, to synchronize its clock with a reliable external standard.
    1789       </p>
    1790       <p id="rfc.section.8.3.p.7">Clients <em class="bcp14">SHOULD</em> only send a Date header field in messages that include an entity-body, as in the case of the PUT and POST requests, and even
    1791          then it is optional. A client without a clock <em class="bcp14">MUST NOT</em> send a Date header field in a request.
    1792       </p>
    1793       <p id="rfc.section.8.3.p.8">The HTTP-date sent in a Date header <em class="bcp14">SHOULD NOT</em> represent a date and time subsequent to the generation of the message. It <em class="bcp14">SHOULD</em> represent the best available approximation of the date and time of message generation, unless the implementation has no means
    1794          of generating a reasonably accurate date and time. In theory, the date ought to represent the moment just before the entity
    1795          is generated. In practice, the date can be generated at any time during the message origination without affecting its semantic
    1796          value.
    1797       </p>
    1798       <h3 id="rfc.section.8.3.1"><a href="#rfc.section.8.3.1">8.3.1</a>&nbsp;<a id="clockless.origin.server.operation" href="#clockless.origin.server.operation">Clockless Origin Server Operation</a></h3>
    1799       <p id="rfc.section.8.3.1.p.1">Some origin server implementations might not have a clock available. An origin server without a clock <em class="bcp14">MUST NOT</em> assign Expires or Last-Modified values to a response, unless these values were associated with the resource by a system or
    1800          user with a reliable clock. It <em class="bcp14">MAY</em> assign an Expires value that is known, at or before server configuration time, to be in the past (this allows "pre-expiration"
    1801          of responses without storing separate Expires values for each resource).
    1802       </p>
    1803       <div id="rfc.iref.h.4"></div>
    1804       <div id="rfc.iref.h.5"></div>
    1805       <h2 id="rfc.section.8.4"><a href="#rfc.section.8.4">8.4</a>&nbsp;<a id="header.host" href="#header.host">Host</a></h2>
    1806       <p id="rfc.section.8.4.p.1">The Host request-header field specifies the Internet host and port number of the resource being requested, as obtained from
    1807          the original URI given by the user or referring resource (generally an HTTP URL, as described in <a href="#http.url" title="http URL">Section&nbsp;3.2.2</a>). The Host field value <em class="bcp14">MUST</em> represent the naming authority of the origin server or gateway given by the original URL. This allows the origin server or
    1808          gateway to differentiate between internally-ambiguous URLs, such as the root "/" URL of a server for multiple host names on
    1809          a single IP address.
    1810       </p>
    1811       <div id="rfc.figure.u.51"></div><pre class="inline"><span id="rfc.iref.g.86"></span>  <a href="#header.host" class="smpl">Host</a> = "Host" ":" <a href="#general.syntax" class="smpl">uri-host</a> [ ":" <a href="#general.syntax" class="smpl">port</a> ] ; <a href="#http.url" title="http URL">Section&nbsp;3.2.2</a>
     1882            </p>
     1883            <ol>
     1884               <li>If the response status code is 100 (Continue) or 101 (Switching Protocols), the response <em class="bcp14">MAY</em> include a Date header field, at the server's option.
     1885               </li>
     1886               <li>If the response status code conveys a server error, e.g. 500 (Internal Server Error) or 503 (Service Unavailable), and it
     1887                  is inconvenient or impossible to generate a valid Date.
     1888               </li>
     1889               <li>If the server does not have a clock that can provide a reasonable approximation of the current time, its responses <em class="bcp14">MUST NOT</em> include a Date header field. In this case, the rules in <a href="#clockless.origin.server.operation" title="Clockless Origin Server Operation">Section&nbsp;8.3.1</a> <em class="bcp14">MUST</em> be followed.
     1890               </li>
     1891            </ol>
     1892            <p id="rfc.section.8.3.p.6">A received message that does not have a Date header field <em class="bcp14">MUST</em> be assigned one by the recipient if the message will be cached by that recipient or gatewayed via a protocol which requires
     1893               a Date. An HTTP implementation without a clock <em class="bcp14">MUST NOT</em> cache responses without revalidating them on every use. An HTTP cache, especially a shared cache, <em class="bcp14">SHOULD</em> use a mechanism, such as NTP <a href="#RFC1305" id="rfc.xref.RFC1305.1"><cite title="Network Time Protocol (Version 3) Specification, Implementation">[RFC1305]</cite></a>, to synchronize its clock with a reliable external standard.
     1894            </p>
     1895            <p id="rfc.section.8.3.p.7">Clients <em class="bcp14">SHOULD</em> only send a Date header field in messages that include an entity-body, as in the case of the PUT and POST requests, and even
     1896               then it is optional. A client without a clock <em class="bcp14">MUST NOT</em> send a Date header field in a request.
     1897            </p>
     1898            <p id="rfc.section.8.3.p.8">The HTTP-date sent in a Date header <em class="bcp14">SHOULD NOT</em> represent a date and time subsequent to the generation of the message. It <em class="bcp14">SHOULD</em> represent the best available approximation of the date and time of message generation, unless the implementation has no means
     1899               of generating a reasonably accurate date and time. In theory, the date ought to represent the moment just before the entity
     1900               is generated. In practice, the date can be generated at any time during the message origination without affecting its semantic
     1901               value.
     1902            </p>
     1903            <div id="clockless.origin.server.operation">
     1904               <h3 id="rfc.section.8.3.1"><a href="#rfc.section.8.3.1">8.3.1</a>&nbsp;<a href="#clockless.origin.server.operation">Clockless Origin Server Operation</a></h3>
     1905               <p id="rfc.section.8.3.1.p.1">Some origin server implementations might not have a clock available. An origin server without a clock <em class="bcp14">MUST NOT</em> assign Expires or Last-Modified values to a response, unless these values were associated with the resource by a system or
     1906                  user with a reliable clock. It <em class="bcp14">MAY</em> assign an Expires value that is known, at or before server configuration time, to be in the past (this allows "pre-expiration"
     1907                  of responses without storing separate Expires values for each resource).
     1908               </p>
     1909            </div>
     1910         </div>
     1911         <div id="header.host">
     1912            <div id="rfc.iref.h.4"></div>
     1913            <div id="rfc.iref.h.5"></div>
     1914            <h2 id="rfc.section.8.4"><a href="#rfc.section.8.4">8.4</a>&nbsp;<a href="#header.host">Host</a></h2>
     1915            <p id="rfc.section.8.4.p.1">The Host request-header field specifies the Internet host and port number of the resource being requested, as obtained from
     1916               the original URI given by the user or referring resource (generally an HTTP URL, as described in <a href="#http.url" title="http URL">Section&nbsp;3.2.2</a>). The Host field value <em class="bcp14">MUST</em> represent the naming authority of the origin server or gateway given by the original URL. This allows the origin server or
     1917               gateway to differentiate between internally-ambiguous URLs, such as the root "/" URL of a server for multiple host names on
     1918               a single IP address.
     1919            </p>
     1920            <div id="rfc.figure.u.51"></div><pre class="inline"><span id="rfc.iref.g.86"></span>  <a href="#header.host" class="smpl">Host</a> = "Host" ":" <a href="#general.syntax" class="smpl">uri-host</a> [ ":" <a href="#general.syntax" class="smpl">port</a> ] ; <a href="#http.url" title="http URL">Section&nbsp;3.2.2</a>
    18121921</pre><p id="rfc.section.8.4.p.3">A "host" without any trailing port information implies the default port for the service requested (e.g., "80" for an HTTP
    1813          URL). For example, a request on the origin server for &lt;http://www.example.org/pub/WWW/&gt; would properly include:
    1814       </p>
    1815       <div id="rfc.figure.u.52"></div><pre class="text">    GET /pub/WWW/ HTTP/1.1
     1922               URL). For example, a request on the origin server for &lt;http://www.example.org/pub/WWW/&gt; would properly include:
     1923            </p>
     1924            <div id="rfc.figure.u.52"></div><pre class="text">    GET /pub/WWW/ HTTP/1.1
    18161925    Host: www.example.org
    18171926</pre><p id="rfc.section.8.4.p.5">A client <em class="bcp14">MUST</em> include a Host header field in all HTTP/1.1 request messages. If the requested URI does not include an Internet host name
    1818          for the service being requested, then the Host header field <em class="bcp14">MUST</em> be given with an empty value. An HTTP/1.1 proxy <em class="bcp14">MUST</em> ensure that any request message it forwards does contain an appropriate Host header field that identifies the service being
    1819          requested by the proxy. All Internet-based HTTP/1.1 servers <em class="bcp14">MUST</em> respond with a 400 (Bad Request) status code to any HTTP/1.1 request message which lacks a Host header field.
    1820       </p>
    1821       <p id="rfc.section.8.4.p.6">See Sections <a href="#the.resource.identified.by.a.request" title="The Resource Identified by a Request">5.2</a> and <a href="#changes.to.simplify.multi-homed.web.servers.and.conserve.ip.addresses" title="Changes to Simplify Multi-homed Web Servers and Conserve IP Addresses">D.1.1</a> for other requirements relating to Host.
    1822       </p>
    1823       <div id="rfc.iref.t.2"></div>
    1824       <div id="rfc.iref.h.6"></div>
    1825       <h2 id="rfc.section.8.5"><a href="#rfc.section.8.5">8.5</a>&nbsp;<a id="header.te" href="#header.te">TE</a></h2>
    1826       <p id="rfc.section.8.5.p.1">The TE request-header field indicates what extension transfer-codings it is willing to accept in the response and whether
    1827          or not it is willing to accept trailer fields in a chunked transfer-coding. Its value may consist of the keyword "trailers"
    1828          and/or a comma-separated list of extension transfer-coding names with optional accept parameters (as described in <a href="#transfer.codings" title="Transfer Codings">Section&nbsp;3.4</a>).
    1829       </p>
    1830       <div id="rfc.figure.u.53"></div><pre class="inline"><span id="rfc.iref.g.87"></span><span id="rfc.iref.g.88"></span>  <a href="#header.te" class="smpl">TE</a>        = "TE" ":" #( <a href="#header.te" class="smpl">t-codings</a> )
     1927               for the service being requested, then the Host header field <em class="bcp14">MUST</em> be given with an empty value. An HTTP/1.1 proxy <em class="bcp14">MUST</em> ensure that any request message it forwards does contain an appropriate Host header field that identifies the service being
     1928               requested by the proxy. All Internet-based HTTP/1.1 servers <em class="bcp14">MUST</em> respond with a 400 (Bad Request) status code to any HTTP/1.1 request message which lacks a Host header field.
     1929            </p>
     1930            <p id="rfc.section.8.4.p.6">See Sections <a href="#the.resource.identified.by.a.request" title="The Resource Identified by a Request">5.2</a> and <a href="#changes.to.simplify.multi-homed.web.servers.and.conserve.ip.addresses" title="Changes to Simplify Multi-homed Web Servers and Conserve IP Addresses">D.1.1</a> for other requirements relating to Host.
     1931            </p>
     1932         </div>
     1933         <div id="header.te">
     1934            <div id="rfc.iref.t.2"></div>
     1935            <div id="rfc.iref.h.6"></div>
     1936            <h2 id="rfc.section.8.5"><a href="#rfc.section.8.5">8.5</a>&nbsp;<a href="#header.te">TE</a></h2>
     1937            <p id="rfc.section.8.5.p.1">The TE request-header field indicates what extension transfer-codings it is willing to accept in the response and whether
     1938               or not it is willing to accept trailer fields in a chunked transfer-coding. Its value may consist of the keyword "trailers"
     1939               and/or a comma-separated list of extension transfer-coding names with optional accept parameters (as described in <a href="#transfer.codings" title="Transfer Codings">Section&nbsp;3.4</a>).
     1940            </p>
     1941            <div id="rfc.figure.u.53"></div><pre class="inline"><span id="rfc.iref.g.87"></span><span id="rfc.iref.g.88"></span>  <a href="#header.te" class="smpl">TE</a>        = "TE" ":" #( <a href="#header.te" class="smpl">t-codings</a> )
    18311942  <a href="#header.te" class="smpl">t-codings</a> = "trailers" | ( <a href="#transfer.codings" class="smpl">transfer-extension</a> [ <a href="#abnf.dependencies" class="smpl">accept-params</a> ] )
    18321943</pre><p id="rfc.section.8.5.p.3">The presence of the keyword "trailers" indicates that the client is willing to accept trailer fields in a chunked transfer-coding,
    1833          as defined in <a href="#chunked.transfer.encoding" title="Chunked Transfer Coding">Section&nbsp;3.4.1</a>. This keyword is reserved for use with transfer-coding values even though it does not itself represent a transfer-coding.
    1834       </p>
    1835       <p id="rfc.section.8.5.p.4">Examples of its use are:</p>
    1836       <div id="rfc.figure.u.54"></div><pre class="text">    TE: deflate
     1944               as defined in <a href="#chunked.transfer.encoding" title="Chunked Transfer Coding">Section&nbsp;3.4.1</a>. This keyword is reserved for use with transfer-coding values even though it does not itself represent a transfer-coding.
     1945            </p>
     1946            <p id="rfc.section.8.5.p.4">Examples of its use are:</p>
     1947            <div id="rfc.figure.u.54"></div><pre class="text">    TE: deflate
    18371948    TE:
    18381949    TE: trailers, deflate;q=0.5
    18391950</pre><p id="rfc.section.8.5.p.6">The TE header field only applies to the immediate connection. Therefore, the keyword <em class="bcp14">MUST</em> be supplied within a Connection header field (<a href="#header.connection" id="rfc.xref.header.connection.4" title="Connection">Section&nbsp;8.1</a>) whenever TE is present in an HTTP/1.1 message.
    1840       </p>
    1841       <p id="rfc.section.8.5.p.7">A server tests whether a transfer-coding is acceptable, according to a TE field, using these rules: </p>
    1842       <ol>
    1843          <li>
    1844             <p>The "chunked" transfer-coding is always acceptable. If the keyword "trailers" is listed, the client indicates that it is willing
    1845                to accept trailer fields in the chunked response on behalf of itself and any downstream clients. The implication is that,
    1846                if given, the client is stating that either all downstream clients are willing to accept trailer fields in the forwarded response,
    1847                or that it will attempt to buffer the response on behalf of downstream recipients.
    1848             </p>
    1849             <p> <b>Note:</b> HTTP/1.1 does not define any means to limit the size of a chunked response such that a client can be assured of buffering
    1850                the entire response.
    1851             </p>
    1852          </li>
    1853          <li>
    1854             <p>If the transfer-coding being tested is one of the transfer-codings listed in the TE field, then it is acceptable unless it
    1855                is accompanied by a qvalue of 0. (As defined in <a href="p3-payload.html#quality.values" title="Quality Values">Section 3.4</a> of <a href="#Part3" id="rfc.xref.Part3.14"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>, a qvalue of 0 means "not acceptable.")
    1856             </p>
    1857          </li>
    1858          <li>
    1859             <p>If multiple transfer-codings are acceptable, then the acceptable transfer-coding with the highest non-zero qvalue is preferred.
    1860                The "chunked" transfer-coding always has a qvalue of 1.
    1861             </p>
    1862          </li>
    1863       </ol>
    1864       <p id="rfc.section.8.5.p.8">If the TE field-value is empty or if no TE field is present, the only transfer-coding is "chunked". A message with no transfer-coding
    1865          is always acceptable.
    1866       </p>
    1867       <div id="rfc.iref.t.3"></div>
    1868       <div id="rfc.iref.h.7"></div>
    1869       <h2 id="rfc.section.8.6"><a href="#rfc.section.8.6">8.6</a>&nbsp;<a id="header.trailer" href="#header.trailer">Trailer</a></h2>
    1870       <p id="rfc.section.8.6.p.1">The Trailer general field value indicates that the given set of header fields is present in the trailer of a message encoded
    1871          with chunked transfer-coding.
    1872       </p>
    1873       <div id="rfc.figure.u.55"></div><pre class="inline"><span id="rfc.iref.g.89"></span>  <a href="#header.trailer" class="smpl">Trailer</a>  = "Trailer" ":" 1#<a href="#message.headers" class="smpl">field-name</a>
     1951            </p>
     1952            <p id="rfc.section.8.5.p.7">A server tests whether a transfer-coding is acceptable, according to a TE field, using these rules: </p>
     1953            <ol>
     1954               <li>
     1955                  <p>The "chunked" transfer-coding is always acceptable. If the keyword "trailers" is listed, the client indicates that it is willing
     1956                     to accept trailer fields in the chunked response on behalf of itself and any downstream clients. The implication is that,
     1957                     if given, the client is stating that either all downstream clients are willing to accept trailer fields in the forwarded response,
     1958                     or that it will attempt to buffer the response on behalf of downstream recipients.
     1959                  </p>
     1960                  <p><b>Note:</b> HTTP/1.1 does not define any means to limit the size of a chunked response such that a client can be assured of buffering
     1961                     the entire response.
     1962                  </p>
     1963               </li>
     1964               <li>
     1965                  <p>If the transfer-coding being tested is one of the transfer-codings listed in the TE field, then it is acceptable unless it
     1966                     is accompanied by a qvalue of 0. (As defined in <a href="p3-payload.html#quality.values" title="Quality Values">Section 3.4</a> of <a href="#Part3" id="rfc.xref.Part3.14"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>, a qvalue of 0 means "not acceptable.")
     1967                  </p>
     1968               </li>
     1969               <li>
     1970                  <p>If multiple transfer-codings are acceptable, then the acceptable transfer-coding with the highest non-zero qvalue is preferred.
     1971                     The "chunked" transfer-coding always has a qvalue of 1.
     1972                  </p>
     1973               </li>
     1974            </ol>
     1975            <p id="rfc.section.8.5.p.8">If the TE field-value is empty or if no TE field is present, the only transfer-coding is "chunked". A message with no transfer-coding
     1976               is always acceptable.
     1977            </p>
     1978         </div>
     1979         <div id="header.trailer">
     1980            <div id="rfc.iref.t.3"></div>
     1981            <div id="rfc.iref.h.7"></div>
     1982            <h2 id="rfc.section.8.6"><a href="#rfc.section.8.6">8.6</a>&nbsp;<a href="#header.trailer">Trailer</a></h2>
     1983            <p id="rfc.section.8.6.p.1">The Trailer general field value indicates that the given set of header fields is present in the trailer of a message encoded
     1984               with chunked transfer-coding.
     1985            </p>
     1986            <div id="rfc.figure.u.55"></div><pre class="inline"><span id="rfc.iref.g.89"></span>  <a href="#header.trailer" class="smpl">Trailer</a>  = "Trailer" ":" 1#<a href="#message.headers" class="smpl">field-name</a>
    18741987</pre><p id="rfc.section.8.6.p.3">An HTTP/1.1 message <em class="bcp14">SHOULD</em> include a Trailer header field in a message using chunked transfer-coding with a non-empty trailer. Doing so allows the recipient
    1875          to know which header fields to expect in the trailer.
    1876       </p>
    1877       <p id="rfc.section.8.6.p.4">If no Trailer header field is present, the trailer <em class="bcp14">SHOULD NOT</em> include any header fields. See <a href="#chunked.transfer.encoding" title="Chunked Transfer Coding">Section&nbsp;3.4.1</a> for restrictions on the use of trailer fields in a "chunked" transfer-coding.
    1878       </p>
    1879       <p id="rfc.section.8.6.p.5">Message header fields listed in the Trailer header field <em class="bcp14">MUST NOT</em> include the following header fields:
    1880       </p>
    1881       <ul>
    1882          <li>Transfer-Encoding</li>
    1883          <li>Content-Length</li>
    1884          <li>Trailer</li>
    1885       </ul>
    1886       <div id="rfc.iref.t.4"></div>
    1887       <div id="rfc.iref.h.8"></div>
    1888       <h2 id="rfc.section.8.7"><a href="#rfc.section.8.7">8.7</a>&nbsp;<a id="header.transfer-encoding" href="#header.transfer-encoding">Transfer-Encoding</a></h2>
    1889       <p id="rfc.section.8.7.p.1">The Transfer-Encoding general-header field indicates what (if any) type of transformation has been applied to the message
    1890          body in order to safely transfer it between the sender and the recipient. This differs from the content-coding in that the
    1891          transfer-coding is a property of the message, not of the entity.
    1892       </p>
    1893       <div id="rfc.figure.u.56"></div><pre class="inline"><span id="rfc.iref.g.90"></span>  <a href="#header.transfer-encoding" class="smpl">Transfer-Encoding</a>       = "Transfer-Encoding" ":" 1#<a href="#transfer.codings" class="smpl">transfer-coding</a>
     1988               to know which header fields to expect in the trailer.
     1989            </p>
     1990            <p id="rfc.section.8.6.p.4">If no Trailer header field is present, the trailer <em class="bcp14">SHOULD NOT</em> include any header fields. See <a href="#chunked.transfer.encoding" title="Chunked Transfer Coding">Section&nbsp;3.4.1</a> for restrictions on the use of trailer fields in a "chunked" transfer-coding.
     1991            </p>
     1992            <p id="rfc.section.8.6.p.5">Message header fields listed in the Trailer header field <em class="bcp14">MUST NOT</em> include the following header fields:
     1993            </p>
     1994            <ul>
     1995               <li>Transfer-Encoding</li>
     1996               <li>Content-Length</li>
     1997               <li>Trailer</li>
     1998            </ul>
     1999         </div>
     2000         <div id="header.transfer-encoding">
     2001            <div id="rfc.iref.t.4"></div>
     2002            <div id="rfc.iref.h.8"></div>
     2003            <h2 id="rfc.section.8.7"><a href="#rfc.section.8.7">8.7</a>&nbsp;<a href="#header.transfer-encoding">Transfer-Encoding</a></h2>
     2004            <p id="rfc.section.8.7.p.1">The Transfer-Encoding general-header field indicates what (if any) type of transformation has been applied to the message
     2005               body in order to safely transfer it between the sender and the recipient. This differs from the content-coding in that the
     2006               transfer-coding is a property of the message, not of the entity.
     2007            </p>
     2008            <div id="rfc.figure.u.56"></div><pre class="inline"><span id="rfc.iref.g.90"></span>  <a href="#header.transfer-encoding" class="smpl">Transfer-Encoding</a>       = "Transfer-Encoding" ":" 1#<a href="#transfer.codings" class="smpl">transfer-coding</a>
    18942009</pre><p id="rfc.section.8.7.p.3">Transfer-codings are defined in <a href="#transfer.codings" title="Transfer Codings">Section&nbsp;3.4</a>. An example is:
    1895       </p>
    1896       <div id="rfc.figure.u.57"></div><pre class="text">  Transfer-Encoding: chunked
     2010            </p>
     2011            <div id="rfc.figure.u.57"></div><pre class="text">  Transfer-Encoding: chunked
    18972012</pre><p id="rfc.section.8.7.p.5">If multiple encodings have been applied to an entity, the transfer-codings <em class="bcp14">MUST</em> be listed in the order in which they were applied. Additional information about the encoding parameters <em class="bcp14">MAY</em> be provided by other entity-header fields not defined by this specification.
    1898       </p>
    1899       <p id="rfc.section.8.7.p.6">Many older HTTP/1.0 applications do not understand the Transfer-Encoding header.</p>
    1900       <div id="rfc.iref.u.3"></div>
    1901       <div id="rfc.iref.h.9"></div>
    1902       <h2 id="rfc.section.8.8"><a href="#rfc.section.8.8">8.8</a>&nbsp;<a id="header.upgrade" href="#header.upgrade">Upgrade</a></h2>
    1903       <p id="rfc.section.8.8.p.1">The Upgrade general-header allows the client to specify what additional communication protocols it supports and would like
    1904          to use if the server finds it appropriate to switch protocols. The server <em class="bcp14">MUST</em> use the Upgrade header field within a 101 (Switching Protocols) response to indicate which protocol(s) are being switched.
    1905       </p>
    1906       <div id="rfc.figure.u.58"></div><pre class="inline"><span id="rfc.iref.g.91"></span>  <a href="#header.upgrade" class="smpl">Upgrade</a>        = "Upgrade" ":" 1#<a href="#product.tokens" class="smpl">product</a>
     2013            </p>
     2014            <p id="rfc.section.8.7.p.6">Many older HTTP/1.0 applications do not understand the Transfer-Encoding header.</p>
     2015         </div>
     2016         <div id="header.upgrade">
     2017            <div id="rfc.iref.u.3"></div>
     2018            <div id="rfc.iref.h.9"></div>
     2019            <h2 id="rfc.section.8.8"><a href="#rfc.section.8.8">8.8</a>&nbsp;<a href="#header.upgrade">Upgrade</a></h2>
     2020            <p id="rfc.section.8.8.p.1">The Upgrade general-header allows the client to specify what additional communication protocols it supports and would like
     2021               to use if the server finds it appropriate to switch protocols. The server <em class="bcp14">MUST</em> use the Upgrade header field within a 101 (Switching Protocols) response to indicate which protocol(s) are being switched.
     2022            </p>
     2023            <div id="rfc.figure.u.58"></div><pre class="inline"><span id="rfc.iref.g.91"></span>  <a href="#header.upgrade" class="smpl">Upgrade</a>        = "Upgrade" ":" 1#<a href="#product.tokens" class="smpl">product</a>
    19072024</pre><p id="rfc.section.8.8.p.3">For example,</p>
    1908       <div id="rfc.figure.u.59"></div><pre class="text">    Upgrade: HTTP/2.0, SHTTP/1.3, IRC/6.9, RTA/x11
     2025            <div id="rfc.figure.u.59"></div><pre class="text">    Upgrade: HTTP/2.0, SHTTP/1.3, IRC/6.9, RTA/x11
    19092026</pre><p id="rfc.section.8.8.p.5">The Upgrade header field is intended to provide a simple mechanism for transition from HTTP/1.1 to some other, incompatible
    1910          protocol. It does so by allowing the client to advertise its desire to use another protocol, such as a later version of HTTP
    1911          with a higher major version number, even though the current request has been made using HTTP/1.1. This eases the difficult
    1912          transition between incompatible protocols by allowing the client to initiate a request in the more commonly supported protocol
    1913          while indicating to the server that it would like to use a "better" protocol if available (where "better" is determined by
    1914          the server, possibly according to the nature of the method and/or resource being requested).
    1915       </p>
    1916       <p id="rfc.section.8.8.p.6">The Upgrade header field only applies to switching application-layer protocols upon the existing transport-layer connection.
    1917          Upgrade cannot be used to insist on a protocol change; its acceptance and use by the server is optional. The capabilities
    1918          and nature of the application-layer communication after the protocol change is entirely dependent upon the new protocol chosen,
    1919          although the first action after changing the protocol <em class="bcp14">MUST</em> be a response to the initial HTTP request containing the Upgrade header field.
    1920       </p>
    1921       <p id="rfc.section.8.8.p.7">The Upgrade header field only applies to the immediate connection. Therefore, the upgrade keyword <em class="bcp14">MUST</em> be supplied within a Connection header field (<a href="#header.connection" id="rfc.xref.header.connection.5" title="Connection">Section&nbsp;8.1</a>) whenever Upgrade is present in an HTTP/1.1 message.
    1922       </p>
    1923       <p id="rfc.section.8.8.p.8">The Upgrade header field cannot be used to indicate a switch to a protocol on a different connection. For that purpose, it
    1924          is more appropriate to use a 301, 302, 303, or 305 redirection response.
    1925       </p>
    1926       <p id="rfc.section.8.8.p.9">This specification only defines the protocol name "HTTP" for use by the family of Hypertext Transfer Protocols, as defined
    1927          by the HTTP version rules of <a href="#http.version" title="HTTP Version">Section&nbsp;3.1</a> and future updates to this specification. Any token can be used as a protocol name; however, it will only be useful if both
    1928          the client and server associate the name with the same protocol.
    1929       </p>
    1930       <div id="rfc.iref.v.2"></div>
    1931       <div id="rfc.iref.h.10"></div>
    1932       <h2 id="rfc.section.8.9"><a href="#rfc.section.8.9">8.9</a>&nbsp;<a id="header.via" href="#header.via">Via</a></h2>
    1933       <p id="rfc.section.8.9.p.1">The Via general-header field <em class="bcp14">MUST</em> be used by gateways and proxies to indicate the intermediate protocols and recipients between the user agent and the server
    1934          on requests, and between the origin server and the client on responses. It is analogous to the "Received" field defined in <a href="http://tools.ietf.org/html/rfc2822#section-3.6.7">Section 3.6.7</a> of <a href="#RFC2822" id="rfc.xref.RFC2822.5"><cite title="Internet Message Format">[RFC2822]</cite></a> and is intended to be used for tracking message forwards, avoiding request loops, and identifying the protocol capabilities
    1935          of all senders along the request/response chain.
    1936       </p>
    1937       <div id="rfc.figure.u.60"></div><pre class="inline"><span id="rfc.iref.g.92"></span><span id="rfc.iref.g.93"></span><span id="rfc.iref.g.94"></span><span id="rfc.iref.g.95"></span><span id="rfc.iref.g.96"></span><span id="rfc.iref.g.97"></span>  <a href="#header.via" class="smpl">Via</a> =  "Via" ":" 1#( <a href="#header.via" class="smpl">received-protocol</a> <a href="#header.via" class="smpl">received-by</a> [ <a href="#rule.comment" class="smpl">comment</a> ] )
     2027               protocol. It does so by allowing the client to advertise its desire to use another protocol, such as a later version of HTTP
     2028               with a higher major version number, even though the current request has been made using HTTP/1.1. This eases the difficult
     2029               transition between incompatible protocols by allowing the client to initiate a request in the more commonly supported protocol
     2030               while indicating to the server that it would like to use a "better" protocol if available (where "better" is determined by
     2031               the server, possibly according to the nature of the method and/or resource being requested).
     2032            </p>
     2033            <p id="rfc.section.8.8.p.6">The Upgrade header field only applies to switching application-layer protocols upon the existing transport-layer connection.
     2034               Upgrade cannot be used to insist on a protocol change; its acceptance and use by the server is optional. The capabilities
     2035               and nature of the application-layer communication after the protocol change is entirely dependent upon the new protocol chosen,
     2036               although the first action after changing the protocol <em class="bcp14">MUST</em> be a response to the initial HTTP request containing the Upgrade header field.
     2037            </p>
     2038            <p id="rfc.section.8.8.p.7">The Upgrade header field only applies to the immediate connection. Therefore, the upgrade keyword <em class="bcp14">MUST</em> be supplied within a Connection header field (<a href="#header.connection" id="rfc.xref.header.connection.5" title="Connection">Section&nbsp;8.1</a>) whenever Upgrade is present in an HTTP/1.1 message.
     2039            </p>
     2040            <p id="rfc.section.8.8.p.8">The Upgrade header field cannot be used to indicate a switch to a protocol on a different connection. For that purpose, it
     2041               is more appropriate to use a 301, 302, 303, or 305 redirection response.
     2042            </p>
     2043            <p id="rfc.section.8.8.p.9">This specification only defines the protocol name "HTTP" for use by the family of Hypertext Transfer Protocols, as defined
     2044               by the HTTP version rules of <a href="#http.version" title="HTTP Version">Section&nbsp;3.1</a> and future updates to this specification. Any token can be used as a protocol name; however, it will only be useful if both
     2045               the client and server associate the name with the same protocol.
     2046            </p>
     2047         </div>
     2048         <div id="header.via">
     2049            <div id="rfc.iref.v.2"></div>
     2050            <div id="rfc.iref.h.10"></div>
     2051            <h2 id="rfc.section.8.9"><a href="#rfc.section.8.9">8.9</a>&nbsp;<a href="#header.via">Via</a></h2>
     2052            <p id="rfc.section.8.9.p.1">The Via general-header field <em class="bcp14">MUST</em> be used by gateways and proxies to indicate the intermediate protocols and recipients between the user agent and the server
     2053               on requests, and between the origin server and the client on responses. It is analogous to the "Received" field defined in <a href="https://tools.ietf.org/html/rfc2822#section-3.6.7">Section 3.6.7</a> of <a href="#RFC2822" id="rfc.xref.RFC2822.5"><cite title="Internet Message Format">[RFC2822]</cite></a> and is intended to be used for tracking message forwards, avoiding request loops, and identifying the protocol capabilities
     2054               of all senders along the request/response chain.
     2055            </p>
     2056            <div id="rfc.figure.u.60"></div><pre class="inline"><span id="rfc.iref.g.92"></span><span id="rfc.iref.g.93"></span><span id="rfc.iref.g.94"></span><span id="rfc.iref.g.95"></span><span id="rfc.iref.g.96"></span><span id="rfc.iref.g.97"></span>  <a href="#header.via" class="smpl">Via</a> =  "Via" ":" 1#( <a href="#header.via" class="smpl">received-protocol</a> <a href="#header.via" class="smpl">received-by</a> [ <a href="#rule.comment" class="smpl">comment</a> ] )
    19382057  <a href="#header.via" class="smpl">received-protocol</a> = [ <a href="#header.via" class="smpl">protocol-name</a> "/" ] <a href="#header.via" class="smpl">protocol-version</a>
    19392058  <a href="#header.via" class="smpl">protocol-name</a>     = <a href="#rule.token.separators" class="smpl">token</a>
     
    19422061  <a href="#header.via" class="smpl">pseudonym</a>         = <a href="#rule.token.separators" class="smpl">token</a>
    19432062</pre><p id="rfc.section.8.9.p.3">The received-protocol indicates the protocol version of the message received by the server or client along each segment of
    1944          the request/response chain. The received-protocol version is appended to the Via field value when the message is forwarded
    1945          so that information about the protocol capabilities of upstream applications remains visible to all recipients.
    1946       </p>
    1947       <p id="rfc.section.8.9.p.4">The protocol-name is optional if and only if it would be "HTTP". The received-by field is normally the host and optional port
    1948          number of a recipient server or client that subsequently forwarded the message. However, if the real host is considered to
    1949          be sensitive information, it <em class="bcp14">MAY</em> be replaced by a pseudonym. If the port is not given, it <em class="bcp14">MAY</em> be assumed to be the default port of the received-protocol.
    1950       </p>
    1951       <p id="rfc.section.8.9.p.5">Multiple Via field values represents each proxy or gateway that has forwarded the message. Each recipient <em class="bcp14">MUST</em> append its information such that the end result is ordered according to the sequence of forwarding applications.
    1952       </p>
    1953       <p id="rfc.section.8.9.p.6">Comments <em class="bcp14">MAY</em> be used in the Via header field to identify the software of the recipient proxy or gateway, analogous to the User-Agent and
    1954          Server header fields. However, all comments in the Via field are optional and <em class="bcp14">MAY</em> be removed by any recipient prior to forwarding the message.
    1955       </p>
    1956       <p id="rfc.section.8.9.p.7">For example, a request message could be sent from an HTTP/1.0 user agent to an internal proxy code-named "fred", which uses
    1957          HTTP/1.1 to forward the request to a public proxy at p.example.net, which completes the request by forwarding it to the origin
    1958          server at www.example.com. The request received by www.example.com would then have the following Via header field:
    1959       </p>
    1960       <div id="rfc.figure.u.61"></div><pre class="text">    Via: 1.0 fred, 1.1 p.example.net (Apache/1.1)
     2063               the request/response chain. The received-protocol version is appended to the Via field value when the message is forwarded
     2064               so that information about the protocol capabilities of upstream applications remains visible to all recipients.
     2065            </p>
     2066            <p id="rfc.section.8.9.p.4">The protocol-name is optional if and only if it would be "HTTP". The received-by field is normally the host and optional port
     2067               number of a recipient server or client that subsequently forwarded the message. However, if the real host is considered to
     2068               be sensitive information, it <em class="bcp14">MAY</em> be replaced by a pseudonym. If the port is not given, it <em class="bcp14">MAY</em> be assumed to be the default port of the received-protocol.
     2069            </p>
     2070            <p id="rfc.section.8.9.p.5">Multiple Via field values represents each proxy or gateway that has forwarded the message. Each recipient <em class="bcp14">MUST</em> append its information such that the end result is ordered according to the sequence of forwarding applications.
     2071            </p>
     2072            <p id="rfc.section.8.9.p.6">Comments <em class="bcp14">MAY</em> be used in the Via header field to identify the software of the recipient proxy or gateway, analogous to the User-Agent and
     2073               Server header fields. However, all comments in the Via field are optional and <em class="bcp14">MAY</em> be removed by any recipient prior to forwarding the message.
     2074            </p>
     2075            <p id="rfc.section.8.9.p.7">For example, a request message could be sent from an HTTP/1.0 user agent to an internal proxy code-named "fred", which uses
     2076               HTTP/1.1 to forward the request to a public proxy at p.example.net, which completes the request by forwarding it to the origin
     2077               server at www.example.com. The request received by www.example.com would then have the following Via header field:
     2078            </p>
     2079            <div id="rfc.figure.u.61"></div><pre class="text">    Via: 1.0 fred, 1.1 p.example.net (Apache/1.1)
    19612080</pre><p id="rfc.section.8.9.p.9">Proxies and gateways used as a portal through a network firewall <em class="bcp14">SHOULD NOT</em>, by default, forward the names and ports of hosts within the firewall region. This information <em class="bcp14">SHOULD</em> only be propagated if explicitly enabled. If not enabled, the received-by host of any host behind the firewall <em class="bcp14">SHOULD</em> be replaced by an appropriate pseudonym for that host.
    1962       </p>
    1963       <p id="rfc.section.8.9.p.10">For organizations that have strong privacy requirements for hiding internal structures, a proxy <em class="bcp14">MAY</em> combine an ordered subsequence of Via header field entries with identical received-protocol values into a single such entry.
    1964          For example,
    1965       </p>
    1966       <div id="rfc.figure.u.62"></div><pre class="text">    Via: 1.0 ricky, 1.1 ethel, 1.1 fred, 1.0 lucy
     2081            </p>
     2082            <p id="rfc.section.8.9.p.10">For organizations that have strong privacy requirements for hiding internal structures, a proxy <em class="bcp14">MAY</em> combine an ordered subsequence of Via header field entries with identical received-protocol values into a single such entry.
     2083               For example,
     2084            </p>
     2085            <div id="rfc.figure.u.62"></div><pre class="text">    Via: 1.0 ricky, 1.1 ethel, 1.1 fred, 1.0 lucy
    19672086</pre><p id="rfc.section.8.9.p.12">could be collapsed to</p>
    1968       <div id="rfc.figure.u.63"></div><pre class="text">    Via: 1.0 ricky, 1.1 mertz, 1.0 lucy
     2087            <div id="rfc.figure.u.63"></div><pre class="text">    Via: 1.0 ricky, 1.1 mertz, 1.0 lucy
    19692088</pre><p id="rfc.section.8.9.p.14">Applications <em class="bcp14">SHOULD NOT</em> combine multiple entries unless they are all under the same organizational control and the hosts have already been replaced
    1970          by pseudonyms. Applications <em class="bcp14">MUST NOT</em> combine entries which have different received-protocol values.
    1971       </p>
    1972       <h1 id="rfc.section.9"><a href="#rfc.section.9">9.</a>&nbsp;<a id="IANA.considerations" href="#IANA.considerations">IANA Considerations</a></h1>
    1973       <h2 id="rfc.section.9.1"><a href="#rfc.section.9.1">9.1</a>&nbsp;<a id="message.header.registration" href="#message.header.registration">Message Header Registration</a></h2>
    1974       <p id="rfc.section.9.1.p.1">The Message Header Registry located at &lt;<a href="http://www.iana.org/assignments/message-headers/message-header-index.html">http://www.iana.org/assignments/message-headers/message-header-index.html</a>&gt; should be updated with the permanent registrations below (see <a href="#RFC3864" id="rfc.xref.RFC3864.1"><cite title="Registration Procedures for Message Header Fields">[RFC3864]</cite></a>):
    1975       </p>
    1976       <div id="rfc.table.u.1">
    1977          <table class="tt full center" cellpadding="3" cellspacing="0">
    1978             <thead>
    1979                <tr>
    1980                   <th>Header Field Name</th>
    1981                   <th>Protocol</th>
    1982                   <th>Status</th>
    1983                   <th>Reference</th>
    1984                </tr>
    1985             </thead>
    1986             <tbody>
    1987                <tr>
    1988                   <td class="left">Connection</td>
    1989                   <td class="left">http</td>
    1990                   <td class="left">standard</td>
    1991                   <td class="left"> <a href="#header.connection" id="rfc.xref.header.connection.6" title="Connection">Section&nbsp;8.1</a>
    1992                   </td>
    1993                </tr>
    1994                <tr>
    1995                   <td class="left">Content-Length</td>
    1996                   <td class="left">http</td>
    1997                   <td class="left">standard</td>
    1998                   <td class="left"> <a href="#header.content-length" id="rfc.xref.header.content-length.2" title="Content-Length">Section&nbsp;8.2</a>
    1999                   </td>
    2000                </tr>
    2001                <tr>
    2002                   <td class="left">Date</td>
    2003                   <td class="left">http</td>
    2004                   <td class="left">standard</td>
    2005                   <td class="left"> <a href="#header.date" id="rfc.xref.header.date.2" title="Date">Section&nbsp;8.3</a>
    2006                   </td>
    2007                </tr>
    2008                <tr>
    2009                   <td class="left">Host</td>
    2010                   <td class="left">http</td>
    2011                   <td class="left">standard</td>
    2012                   <td class="left"> <a href="#header.host" id="rfc.xref.header.host.1" title="Host">Section&nbsp;8.4</a>
    2013                   </td>
    2014                </tr>
    2015                <tr>
    2016                   <td class="left">TE</td>
    2017                   <td class="left">http</td>
    2018                   <td class="left">standard</td>
    2019                   <td class="left"> <a href="#header.te" id="rfc.xref.header.te.3" title="TE">Section&nbsp;8.5</a>
    2020                   </td>
    2021                </tr>
    2022                <tr>
    2023                   <td class="left">Trailer</td>
    2024                   <td class="left">http</td>
    2025                   <td class="left">standard</td>
    2026                   <td class="left"> <a href="#header.trailer" id="rfc.xref.header.trailer.3" title="Trailer">Section&nbsp;8.6</a>
    2027                   </td>
    2028                </tr>
    2029                <tr>
    2030                   <td class="left">Transfer-Encoding</td>
    2031                   <td class="left">http</td>
    2032                   <td class="left">standard</td>
    2033                   <td class="left"> <a href="#header.transfer-encoding" id="rfc.xref.header.transfer-encoding.5" title="Transfer-Encoding">Section&nbsp;8.7</a>
    2034                   </td>
    2035                </tr>
    2036                <tr>
    2037                   <td class="left">Upgrade</td>
    2038                   <td class="left">http</td>
    2039                   <td class="left">standard</td>
    2040                   <td class="left"> <a href="#header.upgrade" id="rfc.xref.header.upgrade.2" title="Upgrade">Section&nbsp;8.8</a>
    2041                   </td>
    2042                </tr>
    2043                <tr>
    2044                   <td class="left">Via</td>
    2045                   <td class="left">http</td>
    2046                   <td class="left">standard</td>
    2047                   <td class="left"> <a href="#header.via" id="rfc.xref.header.via.2" title="Via">Section&nbsp;8.9</a>
    2048                   </td>
    2049                </tr>
    2050             </tbody>
    2051          </table>
     2089               by pseudonyms. Applications <em class="bcp14">MUST NOT</em> combine entries which have different received-protocol values.
     2090            </p>
     2091         </div>
    20522092      </div>
    2053       <p id="rfc.section.9.1.p.2">The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".</p>
    2054       <h1 id="rfc.section.10"><a href="#rfc.section.10">10.</a>&nbsp;<a id="security.considerations" href="#security.considerations">Security Considerations</a></h1>
    2055       <p id="rfc.section.10.p.1">This section is meant to inform application developers, information providers, and users of the security limitations in HTTP/1.1
    2056          as described by this document. The discussion does not include definitive solutions to the problems revealed, though it does
    2057          make some suggestions for reducing security risks.
    2058       </p>
    2059       <h2 id="rfc.section.10.1"><a href="#rfc.section.10.1">10.1</a>&nbsp;<a id="personal.information" href="#personal.information">Personal Information</a></h2>
    2060       <p id="rfc.section.10.1.p.1">HTTP clients are often privy to large amounts of personal information (e.g. the user's name, location, mail address, passwords,
    2061          encryption keys, etc.), and <em class="bcp14">SHOULD</em> be very careful to prevent unintentional leakage of this information. We very strongly recommend that a convenient interface
    2062          be provided for the user to control dissemination of such information, and that designers and implementors be particularly
    2063          careful in this area. History shows that errors in this area often create serious security and/or privacy problems and generate
    2064          highly adverse publicity for the implementor's company.
    2065       </p>
    2066       <h2 id="rfc.section.10.2"><a href="#rfc.section.10.2">10.2</a>&nbsp;<a id="abuse.of.server.log.information" href="#abuse.of.server.log.information">Abuse of Server Log Information</a></h2>
    2067       <p id="rfc.section.10.2.p.1">A server is in the position to save personal data about a user's requests which might identify their reading patterns or subjects
    2068          of interest. This information is clearly confidential in nature and its handling can be constrained by law in certain countries.
    2069          People using HTTP to provide data are responsible for ensuring that such material is not distributed without the permission
    2070          of any individuals that are identifiable by the published results.
    2071       </p>
    2072       <h2 id="rfc.section.10.3"><a href="#rfc.section.10.3">10.3</a>&nbsp;<a id="attack.pathname" href="#attack.pathname">Attacks Based On File and Path Names</a></h2>
    2073       <p id="rfc.section.10.3.p.1">Implementations of HTTP origin servers <em class="bcp14">SHOULD</em> be careful to restrict the documents returned by HTTP requests to be only those that were intended by the server administrators.
    2074          If an HTTP server translates HTTP URIs directly into file system calls, the server <em class="bcp14">MUST</em> take special care not to serve files that were not intended to be delivered to HTTP clients. For example, UNIX, Microsoft
    2075          Windows, and other operating systems use ".." as a path component to indicate a directory level above the current one. On
    2076          such a system, an HTTP server <em class="bcp14">MUST</em> disallow any such construct in the Request-URI if it would otherwise allow access to a resource outside those intended to
    2077          be accessible via the HTTP server. Similarly, files intended for reference only internally to the server (such as access control
    2078          files, configuration files, and script code) <em class="bcp14">MUST</em> be protected from inappropriate retrieval, since they might contain sensitive information. Experience has shown that minor
    2079          bugs in such HTTP server implementations have turned into security risks.
    2080       </p>
    2081       <h2 id="rfc.section.10.4"><a href="#rfc.section.10.4">10.4</a>&nbsp;<a id="dns.spoofing" href="#dns.spoofing">DNS Spoofing</a></h2>
    2082       <p id="rfc.section.10.4.p.1">Clients using HTTP rely heavily on the Domain Name Service, and are thus generally prone to security attacks based on the
    2083          deliberate mis-association of IP addresses and DNS names. Clients need to be cautious in assuming the continuing validity
    2084          of an IP number/DNS name association.
    2085       </p>
    2086       <p id="rfc.section.10.4.p.2">In particular, HTTP clients <em class="bcp14">SHOULD</em> rely on their name resolver for confirmation of an IP number/DNS name association, rather than caching the result of previous
    2087          host name lookups. Many platforms already can cache host name lookups locally when appropriate, and they <em class="bcp14">SHOULD</em> be configured to do so. It is proper for these lookups to be cached, however, only when the TTL (Time To Live) information
    2088          reported by the name server makes it likely that the cached information will remain useful.
    2089       </p>
    2090       <p id="rfc.section.10.4.p.3">If HTTP clients cache the results of host name lookups in order to achieve a performance improvement, they <em class="bcp14">MUST</em> observe the TTL information reported by DNS.
    2091       </p>
    2092       <p id="rfc.section.10.4.p.4">If HTTP clients do not observe this rule, they could be spoofed when a previously-accessed server's IP address changes. As
    2093          network renumbering is expected to become increasingly common <a href="#RFC1900" id="rfc.xref.RFC1900.2"><cite title="Renumbering Needs Work">[RFC1900]</cite></a>, the possibility of this form of attack will grow. Observing this requirement thus reduces this potential security vulnerability.
    2094       </p>
    2095       <p id="rfc.section.10.4.p.5">This requirement also improves the load-balancing behavior of clients for replicated servers using the same DNS name and reduces
    2096          the likelihood of a user's experiencing failure in accessing sites which use that strategy.
    2097       </p>
    2098       <h2 id="rfc.section.10.5"><a href="#rfc.section.10.5">10.5</a>&nbsp;<a id="attack.proxies" href="#attack.proxies">Proxies and Caching</a></h2>
    2099       <p id="rfc.section.10.5.p.1">By their very nature, HTTP proxies are men-in-the-middle, and represent an opportunity for man-in-the-middle attacks. Compromise
    2100          of the systems on which the proxies run can result in serious security and privacy problems. Proxies have access to security-related
    2101          information, personal information about individual users and organizations, and proprietary information belonging to users
    2102          and content providers. A compromised proxy, or a proxy implemented or configured without regard to security and privacy considerations,
    2103          might be used in the commission of a wide range of potential attacks.
    2104       </p>
    2105       <p id="rfc.section.10.5.p.2">Proxy operators should protect the systems on which proxies run as they would protect any system that contains or transports
    2106          sensitive information. In particular, log information gathered at proxies often contains highly sensitive personal information,
    2107          and/or information about organizations. Log information should be carefully guarded, and appropriate guidelines for use developed
    2108          and followed. (<a href="#abuse.of.server.log.information" title="Abuse of Server Log Information">Section&nbsp;10.2</a>).
    2109       </p>
    2110       <p id="rfc.section.10.5.p.3">Proxy implementors should consider the privacy and security implications of their design and coding decisions, and of the
    2111          configuration options they provide to proxy operators (especially the default configuration).
    2112       </p>
    2113       <p id="rfc.section.10.5.p.4">Users of a proxy need to be aware that they are no trustworthier than the people who run the proxy; HTTP itself cannot solve
    2114          this problem.
    2115       </p>
    2116       <p id="rfc.section.10.5.p.5">The judicious use of cryptography, when appropriate, may suffice to protect against a broad range of security and privacy
    2117          attacks. Such cryptography is beyond the scope of the HTTP/1.1 specification.
    2118       </p>
    2119       <h2 id="rfc.section.10.6"><a href="#rfc.section.10.6">10.6</a>&nbsp;<a id="attack.DoS" href="#attack.DoS">Denial of Service Attacks on Proxies</a></h2>
    2120       <p id="rfc.section.10.6.p.1">They exist. They are hard to defend against. Research continues. Beware.</p>
    2121       <h1 id="rfc.section.11"><a href="#rfc.section.11">11.</a>&nbsp;<a id="ack" href="#ack">Acknowledgments</a></h1>
    2122       <p id="rfc.section.11.p.1">This specification makes heavy use of the augmented BNF and generic constructs defined by David H. Crocker for <a href="#RFC822ABNF" id="rfc.xref.RFC822ABNF.2"><cite title="Standard for the format of ARPA Internet text messages">[RFC822ABNF]</cite></a>. Similarly, it reuses many of the definitions provided by Nathaniel Borenstein and Ned Freed for MIME <a href="#RFC2045" id="rfc.xref.RFC2045.3"><cite title="Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies">[RFC2045]</cite></a>. We hope that their inclusion in this specification will help reduce past confusion over the relationship between HTTP and
    2123          Internet mail message formats.
    2124       </p>
    2125       <p id="rfc.section.11.p.2">HTTP has evolved considerably over the years. It has benefited from a large and active developer community--the many people
    2126          who have participated on the www-talk mailing list--and it is that community which has been most responsible for the success
    2127          of HTTP and of the World-Wide Web in general. Marc Andreessen, Robert Cailliau, Daniel W. Connolly, Bob Denny, John Franks,
    2128          Jean-Francois Groff, Phillip M. Hallam-Baker, Hakon W. Lie, Ari Luotonen, Rob McCool, Lou Montulli, Dave Raggett, Tony Sanders,
    2129          and Marc VanHeyningen deserve special recognition for their efforts in defining early aspects of the protocol.
    2130       </p>
    2131       <p id="rfc.section.11.p.3">This document has benefited greatly from the comments of all those participating in the HTTP-WG. In addition to those already
    2132          mentioned, the following individuals have contributed to this specification:
    2133       </p>
    2134       <p id="rfc.section.11.p.4">Gary Adams, Harald Tveit Alvestrand, Keith Ball, Brian Behlendorf, Paul Burchard, Maurizio Codogno, Mike Cowlishaw, Roman
    2135          Czyborra, Michael A. Dolan, Daniel DuBois, David J. Fiander, Alan Freier, Marc Hedlund, Greg Herlihy, Koen Holtman, Alex Hopmann,
    2136          Bob Jernigan, Shel Kaphan, Rohit Khare, John Klensin, Martijn Koster, Alexei Kosut, David M. Kristol, Daniel LaLiberte, Ben
    2137          Laurie, Paul J. Leach, Albert Lunde, John C. Mallery, Jean-Philippe Martin-Flatin, Mitra, David Morris, Gavin Nicol, Ross
    2138          Patterson, Bill Perry, Jeffrey Perry, Scott Powers, Owen Rees, Luigi Rizzo, David Robinson, Marc Salomon, Rich Salz, Allan
    2139          M. Schiffman, Jim Seidman, Chuck Shotton, Eric W. Sink, Simon E. Spero, Richard N. Taylor, Robert S. Thau, Bill (BearHeart)
    2140          Weinman, Francois Yergeau, Mary Ellen Zurko, Josh Cohen.
    2141       </p>
    2142       <p id="rfc.section.11.p.5">Thanks to the "cave men" of Palo Alto. You know who you are.</p>
    2143       <p id="rfc.section.11.p.6">Jim Gettys (the editor of <a href="#RFC2616" id="rfc.xref.RFC2616.3"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>) wishes particularly to thank Roy Fielding, the editor of <a href="#RFC2068" id="rfc.xref.RFC2068.5"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2068]</cite></a>, along with John Klensin, Jeff Mogul, Paul Leach, Dave Kristol, Koen Holtman, John Franks, Josh Cohen, Alex Hopmann, Scott
    2144          Lawrence, and Larry Masinter for their help. And thanks go particularly to Jeff Mogul and Scott Lawrence for performing the
    2145          "MUST/MAY/SHOULD" audit.
    2146       </p>
    2147       <p id="rfc.section.11.p.7">The Apache Group, Anselm Baird-Smith, author of Jigsaw, and Henrik Frystyk implemented RFC 2068 early, and we wish to thank
    2148          them for the discovery of many of the problems that this document attempts to rectify.
    2149       </p>
     2093      <div id="IANA.considerations">
     2094         <h1 id="rfc.section.9"><a href="#rfc.section.9">9.</a>&nbsp;<a href="#IANA.considerations">IANA Considerations</a></h1>
     2095         <div id="message.header.registration">
     2096            <h2 id="rfc.section.9.1"><a href="#rfc.section.9.1">9.1</a>&nbsp;<a href="#message.header.registration">Message Header Registration</a></h2>
     2097            <p id="rfc.section.9.1.p.1">The Message Header Registry located at &lt;<a href="http://www.iana.org/assignments/message-headers/message-header-index.html">http://www.iana.org/assignments/message-headers/message-header-index.html</a>&gt; should be updated with the permanent registrations below (see <a href="#RFC3864" id="rfc.xref.RFC3864.1"><cite title="Registration Procedures for Message Header Fields">[RFC3864]</cite></a>):
     2098            </p>
     2099            <div id="rfc.table.u.1">
     2100               <table class="tt full center" cellpadding="3" cellspacing="0">
     2101                  <thead>
     2102                     <tr>
     2103                        <th>Header Field Name</th>
     2104                        <th>Protocol</th>
     2105                        <th>Status</th>
     2106                        <th>Reference</th>
     2107                     </tr>
     2108                  </thead>
     2109                  <tbody>
     2110                     <tr>
     2111                        <td class="left">Connection</td>
     2112                        <td class="left">http</td>
     2113                        <td class="left">standard</td>
     2114                        <td class="left"><a href="#header.connection" id="rfc.xref.header.connection.6" title="Connection">Section&nbsp;8.1</a>
     2115                        </td>
     2116                     </tr>
     2117                     <tr>
     2118                        <td class="left">Content-Length</td>
     2119                        <td class="left">http</td>
     2120                        <td class="left">standard</td>
     2121                        <td class="left"><a href="#header.content-length" id="rfc.xref.header.content-length.2" title="Content-Length">Section&nbsp;8.2</a>
     2122                        </td>
     2123                     </tr>
     2124                     <tr>
     2125                        <td class="left">Date</td>
     2126                        <td class="left">http</td>
     2127                        <td class="left">standard</td>
     2128                        <td class="left"><a href="#header.date" id="rfc.xref.header.date.2" title="Date">Section&nbsp;8.3</a>
     2129                        </td>
     2130                     </tr>
     2131                     <tr>
     2132                        <td class="left">Host</td>
     2133                        <td class="left">http</td>
     2134                        <td class="left">standard</td>
     2135                        <td class="left"><a href="#header.host" id="rfc.xref.header.host.1" title="Host">Section&nbsp;8.4</a>
     2136                        </td>
     2137                     </tr>
     2138                     <tr>
     2139                        <td class="left">TE</td>
     2140                        <td class="left">http</td>
     2141                        <td class="left">standard</td>
     2142                        <td class="left"><a href="#header.te" id="rfc.xref.header.te.3" title="TE">Section&nbsp;8.5</a>
     2143                        </td>
     2144                     </tr>
     2145                     <tr>
     2146                        <td class="left">Trailer</td>
     2147                        <td class="left">http</td>
     2148                        <td class="left">standard</td>
     2149                        <td class="left"><a href="#header.trailer" id="rfc.xref.header.trailer.3" title="Trailer">Section&nbsp;8.6</a>
     2150                        </td>
     2151                     </tr>
     2152                     <tr>
     2153                        <td class="left">Transfer-Encoding</td>
     2154                        <td class="left">http</td>
     2155                        <td class="left">standard</td>
     2156                        <td class="left"><a href="#header.transfer-encoding" id="rfc.xref.header.transfer-encoding.5" title="Transfer-Encoding">Section&nbsp;8.7</a>
     2157                        </td>
     2158                     </tr>
     2159                     <tr>
     2160                        <td class="left">Upgrade</td>
     2161                        <td class="left">http</td>
     2162                        <td class="left">standard</td>
     2163                        <td class="left"><a href="#header.upgrade" id="rfc.xref.header.upgrade.2" title="Upgrade">Section&nbsp;8.8</a>
     2164                        </td>
     2165                     </tr>
     2166                     <tr>
     2167                        <td class="left">Via</td>
     2168                        <td class="left">http</td>
     2169                        <td class="left">standard</td>
     2170                        <td class="left"><a href="#header.via" id="rfc.xref.header.via.2" title="Via">Section&nbsp;8.9</a>
     2171                        </td>
     2172                     </tr>
     2173                  </tbody>
     2174               </table>
     2175            </div>
     2176            <p id="rfc.section.9.1.p.2">The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".</p>
     2177         </div>
     2178      </div>
     2179      <div id="security.considerations">
     2180         <h1 id="rfc.section.10"><a href="#rfc.section.10">10.</a>&nbsp;<a href="#security.considerations">Security Considerations</a></h1>
     2181         <p id="rfc.section.10.p.1">This section is meant to inform application developers, information providers, and users of the security limitations in HTTP/1.1
     2182            as described by this document. The discussion does not include definitive solutions to the problems revealed, though it does
     2183            make some suggestions for reducing security risks.
     2184         </p>
     2185         <div id="personal.information">
     2186            <h2 id="rfc.section.10.1"><a href="#rfc.section.10.1">10.1</a>&nbsp;<a href="#personal.information">Personal Information</a></h2>
     2187            <p id="rfc.section.10.1.p.1">HTTP clients are often privy to large amounts of personal information (e.g. the user's name, location, mail address, passwords,
     2188               encryption keys, etc.), and <em class="bcp14">SHOULD</em> be very careful to prevent unintentional leakage of this information. We very strongly recommend that a convenient interface
     2189               be provided for the user to control dissemination of such information, and that designers and implementors be particularly
     2190               careful in this area. History shows that errors in this area often create serious security and/or privacy problems and generate
     2191               highly adverse publicity for the implementor's company.
     2192            </p>
     2193         </div>
     2194         <div id="abuse.of.server.log.information">
     2195            <h2 id="rfc.section.10.2"><a href="#rfc.section.10.2">10.2</a>&nbsp;<a href="#abuse.of.server.log.information">Abuse of Server Log Information</a></h2>
     2196            <p id="rfc.section.10.2.p.1">A server is in the position to save personal data about a user's requests which might identify their reading patterns or subjects
     2197               of interest. This information is clearly confidential in nature and its handling can be constrained by law in certain countries.
     2198               People using HTTP to provide data are responsible for ensuring that such material is not distributed without the permission
     2199               of any individuals that are identifiable by the published results.
     2200            </p>
     2201         </div>
     2202         <div id="attack.pathname">
     2203            <h2 id="rfc.section.10.3"><a href="#rfc.section.10.3">10.3</a>&nbsp;<a href="#attack.pathname">Attacks Based On File and Path Names</a></h2>
     2204            <p id="rfc.section.10.3.p.1">Implementations of HTTP origin servers <em class="bcp14">SHOULD</em> be careful to restrict the documents returned by HTTP requests to be only those that were intended by the server administrators.
     2205               If an HTTP server translates HTTP URIs directly into file system calls, the server <em class="bcp14">MUST</em> take special care not to serve files that were not intended to be delivered to HTTP clients. For example, UNIX, Microsoft
     2206               Windows, and other operating systems use ".." as a path component to indicate a directory level above the current one. On
     2207               such a system, an HTTP server <em class="bcp14">MUST</em> disallow any such construct in the Request-URI if it would otherwise allow access to a resource outside those intended to
     2208               be accessible via the HTTP server. Similarly, files intended for reference only internally to the server (such as access control
     2209               files, configuration files, and script code) <em class="bcp14">MUST</em> be protected from inappropriate retrieval, since they might contain sensitive information. Experience has shown that minor
     2210               bugs in such HTTP server implementations have turned into security risks.
     2211            </p>
     2212         </div>
     2213         <div id="dns.spoofing">
     2214            <h2 id="rfc.section.10.4"><a href="#rfc.section.10.4">10.4</a>&nbsp;<a href="#dns.spoofing">DNS Spoofing</a></h2>
     2215            <p id="rfc.section.10.4.p.1">Clients using HTTP rely heavily on the Domain Name Service, and are thus generally prone to security attacks based on the
     2216               deliberate mis-association of IP addresses and DNS names. Clients need to be cautious in assuming the continuing validity
     2217               of an IP number/DNS name association.
     2218            </p>
     2219            <p id="rfc.section.10.4.p.2">In particular, HTTP clients <em class="bcp14">SHOULD</em> rely on their name resolver for confirmation of an IP number/DNS name association, rather than caching the result of previous
     2220               host name lookups. Many platforms already can cache host name lookups locally when appropriate, and they <em class="bcp14">SHOULD</em> be configured to do so. It is proper for these lookups to be cached, however, only when the TTL (Time To Live) information
     2221               reported by the name server makes it likely that the cached information will remain useful.
     2222            </p>
     2223            <p id="rfc.section.10.4.p.3">If HTTP clients cache the results of host name lookups in order to achieve a performance improvement, they <em class="bcp14">MUST</em> observe the TTL information reported by DNS.
     2224            </p>
     2225            <p id="rfc.section.10.4.p.4">If HTTP clients do not observe this rule, they could be spoofed when a previously-accessed server's IP address changes. As
     2226               network renumbering is expected to become increasingly common <a href="#RFC1900" id="rfc.xref.RFC1900.2"><cite title="Renumbering Needs Work">[RFC1900]</cite></a>, the possibility of this form of attack will grow. Observing this requirement thus reduces this potential security vulnerability.
     2227            </p>
     2228            <p id="rfc.section.10.4.p.5">This requirement also improves the load-balancing behavior of clients for replicated servers using the same DNS name and reduces
     2229               the likelihood of a user's experiencing failure in accessing sites which use that strategy.
     2230            </p>
     2231         </div>
     2232         <div id="attack.proxies">
     2233            <h2 id="rfc.section.10.5"><a href="#rfc.section.10.5">10.5</a>&nbsp;<a href="#attack.proxies">Proxies and Caching</a></h2>
     2234            <p id="rfc.section.10.5.p.1">By their very nature, HTTP proxies are men-in-the-middle, and represent an opportunity for man-in-the-middle attacks. Compromise
     2235               of the systems on which the proxies run can result in serious security and privacy problems. Proxies have access to security-related
     2236               information, personal information about individual users and organizations, and proprietary information belonging to users
     2237               and content providers. A compromised proxy, or a proxy implemented or configured without regard to security and privacy considerations,
     2238               might be used in the commission of a wide range of potential attacks.
     2239            </p>
     2240            <p id="rfc.section.10.5.p.2">Proxy operators should protect the systems on which proxies run as they would protect any system that contains or transports
     2241               sensitive information. In particular, log information gathered at proxies often contains highly sensitive personal information,
     2242               and/or information about organizations. Log information should be carefully guarded, and appropriate guidelines for use developed
     2243               and followed. (<a href="#abuse.of.server.log.information" title="Abuse of Server Log Information">Section&nbsp;10.2</a>).
     2244            </p>
     2245            <p id="rfc.section.10.5.p.3">Proxy implementors should consider the privacy and security implications of their design and coding decisions, and of the
     2246               configuration options they provide to proxy operators (especially the default configuration).
     2247            </p>
     2248            <p id="rfc.section.10.5.p.4">Users of a proxy need to be aware that they are no trustworthier than the people who run the proxy; HTTP itself cannot solve
     2249               this problem.
     2250            </p>
     2251            <p id="rfc.section.10.5.p.5">The judicious use of cryptography, when appropriate, may suffice to protect against a broad range of security and privacy
     2252               attacks. Such cryptography is beyond the scope of the HTTP/1.1 specification.
     2253            </p>
     2254         </div>
     2255         <div id="attack.DoS">
     2256            <h2 id="rfc.section.10.6"><a href="#rfc.section.10.6">10.6</a>&nbsp;<a href="#attack.DoS">Denial of Service Attacks on Proxies</a></h2>
     2257            <p id="rfc.section.10.6.p.1">They exist. They are hard to defend against. Research continues. Beware.</p>
     2258         </div>
     2259      </div>
     2260      <div id="ack">
     2261         <h1 id="rfc.section.11"><a href="#rfc.section.11">11.</a>&nbsp;<a href="#ack">Acknowledgments</a></h1>
     2262         <p id="rfc.section.11.p.1">This specification makes heavy use of the augmented BNF and generic constructs defined by David H. Crocker for <a href="#RFC822ABNF" id="rfc.xref.RFC822ABNF.2"><cite title="Standard for the format of ARPA Internet text messages">[RFC822ABNF]</cite></a>. Similarly, it reuses many of the definitions provided by Nathaniel Borenstein and Ned Freed for MIME <a href="#RFC2045" id="rfc.xref.RFC2045.3"><cite title="Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies">[RFC2045]</cite></a>. We hope that their inclusion in this specification will help reduce past confusion over the relationship between HTTP and
     2263            Internet mail message formats.
     2264         </p>
     2265         <p id="rfc.section.11.p.2">HTTP has evolved considerably over the years. It has benefited from a large and active developer community--the many people
     2266            who have participated on the www-talk mailing list--and it is that community which has been most responsible for the success
     2267            of HTTP and of the World-Wide Web in general. Marc Andreessen, Robert Cailliau, Daniel W. Connolly, Bob Denny, John Franks,
     2268            Jean-Francois Groff, Phillip M. Hallam-Baker, Hakon W. Lie, Ari Luotonen, Rob McCool, Lou Montulli, Dave Raggett, Tony Sanders,
     2269            and Marc VanHeyningen deserve special recognition for their efforts in defining early aspects of the protocol.
     2270         </p>
     2271         <p id="rfc.section.11.p.3">This document has benefited greatly from the comments of all those participating in the HTTP-WG. In addition to those already
     2272            mentioned, the following individuals have contributed to this specification:
     2273         </p>
     2274         <p id="rfc.section.11.p.4">Gary Adams, Harald Tveit Alvestrand, Keith Ball, Brian Behlendorf, Paul Burchard, Maurizio Codogno, Mike Cowlishaw, Roman
     2275            Czyborra, Michael A. Dolan, Daniel DuBois, David J. Fiander, Alan Freier, Marc Hedlund, Greg Herlihy, Koen Holtman, Alex Hopmann,
     2276            Bob Jernigan, Shel Kaphan, Rohit Khare, John Klensin, Martijn Koster, Alexei Kosut, David M. Kristol, Daniel LaLiberte, Ben
     2277            Laurie, Paul J. Leach, Albert Lunde, John C. Mallery, Jean-Philippe Martin-Flatin, Mitra, David Morris, Gavin Nicol, Ross
     2278            Patterson, Bill Perry, Jeffrey Perry, Scott Powers, Owen Rees, Luigi Rizzo, David Robinson, Marc Salomon, Rich Salz, Allan
     2279            M. Schiffman, Jim Seidman, Chuck Shotton, Eric W. Sink, Simon E. Spero, Richard N. Taylor, Robert S. Thau, Bill (BearHeart)
     2280            Weinman, Francois Yergeau, Mary Ellen Zurko, Josh Cohen.
     2281         </p>
     2282         <p id="rfc.section.11.p.5">Thanks to the "cave men" of Palo Alto. You know who you are.</p>
     2283         <p id="rfc.section.11.p.6">Jim Gettys (the editor of <a href="#RFC2616" id="rfc.xref.RFC2616.3"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>) wishes particularly to thank Roy Fielding, the editor of <a href="#RFC2068" id="rfc.xref.RFC2068.5"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2068]</cite></a>, along with John Klensin, Jeff Mogul, Paul Leach, Dave Kristol, Koen Holtman, John Franks, Josh Cohen, Alex Hopmann, Scott
     2284            Lawrence, and Larry Masinter for their help. And thanks go particularly to Jeff Mogul and Scott Lawrence for performing the
     2285            "MUST/MAY/SHOULD" audit.
     2286         </p>
     2287         <p id="rfc.section.11.p.7">The Apache Group, Anselm Baird-Smith, author of Jigsaw, and Henrik Frystyk implemented RFC 2068 early, and we wish to thank
     2288            them for the discovery of many of the problems that this document attempts to rectify.
     2289         </p>
     2290      </div>
    21502291      <h1 id="rfc.references"><a id="rfc.section.12" href="#rfc.section.12">12.</a> References
    21512292      </h1>
    21522293      <h2 id="rfc.references.1"><a href="#rfc.section.12.1" id="rfc.section.12.1">12.1</a> Normative References
    21532294      </h2>
    2154       <table>                     
     2295      <table>
    21552296         <tr>
    21562297            <td class="reference"><b id="ISO-8859-1">[ISO-8859-1]</b></td>
     
    21592300         <tr>
    21602301            <td class="reference"><b id="Part2">[Part2]</b></td>
    2161             <td class="top"><a href="mailto:fielding@gbiv.com" title="Day Software">Fielding, R., Ed.</a>, <a href="mailto:jg@laptop.org" title="One Laptop per Child">Gettys, J.</a>, <a href="mailto:JeffMogul@acm.org" title="Hewlett-Packard Company">Mogul, J.</a>, <a href="mailto:henrikn@microsoft.com" title="Microsoft Corporation">Frystyk, H.</a>, <a href="mailto:LMM@acm.org" title="Adobe Systems, Incorporated">Masinter, L.</a>, <a href="mailto:paulle@microsoft.com" title="Microsoft Corporation">Leach, P.</a>, <a href="mailto:timbl@w3.org" title="World Wide Web Consortium">Berners-Lee, T.</a>, <a href="mailto:ylafon@w3.org" title="World Wide Web Consortium">Lafon, Y., Ed.</a>, and <a href="mailto:julian.reschke@greenbytes.de" title="greenbytes GmbH">J. Reschke, Ed.</a>, “<a href="http://tools.ietf.org/html/draft-ietf-httpbis-p2-semantics-03">HTTP/1.1, part 2: Message Semantics</a>”, Internet-Draft&nbsp;draft-ietf-httpbis-p2-semantics-03 (work in progress), June&nbsp;2008.
     2302            <td class="top"><a href="mailto:fielding@gbiv.com" title="Day Software">Fielding, R., Ed.</a>, <a href="mailto:jg@laptop.org" title="One Laptop per Child">Gettys, J.</a>, <a href="mailto:JeffMogul@acm.org" title="Hewlett-Packard Company">Mogul, J.</a>, <a href="mailto:henrikn@microsoft.com" title="Microsoft Corporation">Frystyk, H.</a>, <a href="mailto:LMM@acm.org" title="Adobe Systems, Incorporated">Masinter, L.</a>, <a href="mailto:paulle@microsoft.com" title="Microsoft Corporation">Leach, P.</a>, <a href="mailto:timbl@w3.org" title="World Wide Web Consortium">Berners-Lee, T.</a>, <a href="mailto:ylafon@w3.org" title="World Wide Web Consortium">Lafon, Y., Ed.</a>, and <a href="mailto:julian.reschke@greenbytes.de" title="greenbytes GmbH">J. Reschke, Ed.</a>, “<a href="https://tools.ietf.org/html/draft-ietf-httpbis-p2-semantics-03">HTTP/1.1, part 2: Message Semantics</a>”, Internet-Draft&nbsp;draft-ietf-httpbis-p2-semantics-03 (work in progress), June&nbsp;2008.
    21622303            </td>
    21632304         </tr>
    21642305         <tr>
    21652306            <td class="reference"><b id="Part3">[Part3]</b></td>
    2166             <td class="top"><a href="mailto:fielding@gbiv.com" title="Day Software">Fielding, R., Ed.</a>, <a href="mailto:jg@laptop.org" title="One Laptop per Child">Gettys, J.</a>, <a href="mailto:JeffMogul@acm.org" title="Hewlett-Packard Company">Mogul, J.</a>, <a href="mailto:henrikn@microsoft.com" title="Microsoft Corporation">Frystyk, H.</a>, <a href="mailto:LMM@acm.org" title="Adobe Systems, Incorporated">Masinter, L.</a>, <a href="mailto:paulle@microsoft.com" title="Microsoft Corporation">Leach, P.</a>, <a href="mailto:timbl@w3.org" title="World Wide Web Consortium">Berners-Lee, T.</a>, <a href="mailto:ylafon@w3.org" title="World Wide Web Consortium">Lafon, Y., Ed.</a>, and <a href="mailto:julian.reschke@greenbytes.de" title="greenbytes GmbH">J. Reschke, Ed.</a>, “<a href="http://tools.ietf.org/html/draft-ietf-httpbis-p3-payload-03">HTTP/1.1, part 3: Message Payload and Content Negotiation</a>”, Internet-Draft&nbsp;draft-ietf-httpbis-p3-payload-03 (work in progress), June&nbsp;2008.
     2307            <td class="top"><a href="mailto:fielding@gbiv.com" title="Day Software">Fielding, R., Ed.</a>, <a href="mailto:jg@laptop.org" title="One Laptop per Child">Gettys, J.</a>, <a href="mailto:JeffMogul@acm.org" title="Hewlett-Packard Company">Mogul, J.</a>, <a href="mailto:henrikn@microsoft.com" title="Microsoft Corporation">Frystyk, H.</a>, <a href="mailto:LMM@acm.org" title="Adobe Systems, Incorporated">Masinter, L.</a>, <a href="mailto:paulle@microsoft.com" title="Microsoft Corporation">Leach, P.</a>, <a href="mailto:timbl@w3.org" title="World Wide Web Consortium">Berners-Lee, T.</a>, <a href="mailto:ylafon@w3.org" title="World Wide Web Consortium">Lafon, Y., Ed.</a>, and <a href="mailto:julian.reschke@greenbytes.de" title="greenbytes GmbH">J. Reschke, Ed.</a>, “<a href="https://tools.ietf.org/html/draft-ietf-httpbis-p3-payload-03">HTTP/1.1, part 3: Message Payload and Content Negotiation</a>”, Internet-Draft&nbsp;draft-ietf-httpbis-p3-payload-03 (work in progress), June&nbsp;2008.
    21672308            </td>
    21682309         </tr>
    21692310         <tr>
    21702311            <td class="reference"><b id="Part5">[Part5]</b></td>
    2171             <td class="top"><a href="mailto:fielding@gbiv.com" title="Day Software">Fielding, R., Ed.</a>, <a href="mailto:jg@laptop.org" title="One Laptop per Child">Gettys, J.</a>, <a href="mailto:JeffMogul@acm.org" title="Hewlett-Packard Company">Mogul, J.</a>, <a href="mailto:henrikn@microsoft.com" title="Microsoft Corporation">Frystyk, H.</a>, <a href="mailto:LMM@acm.org" title="Adobe Systems, Incorporated">Masinter, L.</a>, <a href="mailto:paulle@microsoft.com" title="Microsoft Corporation">Leach, P.</a>, <a href="mailto:timbl@w3.org" title="World Wide Web Consortium">Berners-Lee, T.</a>, <a href="mailto:ylafon@w3.org" title="World Wide Web Consortium">Lafon, Y., Ed.</a>, and <a href="mailto:julian.reschke@greenbytes.de" title="greenbytes GmbH">J. Reschke, Ed.</a>, “<a href="http://tools.ietf.org/html/draft-ietf-httpbis-p5-range-03">HTTP/1.1, part 5: Range Requests and Partial Responses</a>”, Internet-Draft&nbsp;draft-ietf-httpbis-p5-range-03 (work in progress), June&nbsp;2008.
     2312            <td class="top"><a href="mailto:fielding@gbiv.com" title="Day Software">Fielding, R., Ed.</a>, <a href="mailto:jg@laptop.org" title="One Laptop per Child">Gettys, J.</a>, <a href="mailto:JeffMogul@acm.org" title="Hewlett-Packard Company">Mogul, J.</a>, <a href="mailto:henrikn@microsoft.com" title="Microsoft Corporation">Frystyk, H.</a>, <a href="mailto:LMM@acm.org" title="Adobe Systems, Incorporated">Masinter, L.</a>, <a href="mailto:paulle@microsoft.com" title="Microsoft Corporation">Leach, P.</a>, <a href="mailto:timbl@w3.org" title="World Wide Web Consortium">Berners-Lee, T.</a>, <a href="mailto:ylafon@w3.org" title="World Wide Web Consortium">Lafon, Y., Ed.</a>, and <a href="mailto:julian.reschke@greenbytes.de" title="greenbytes GmbH">J. Reschke, Ed.</a>, “<a href="https://tools.ietf.org/html/draft-ietf-httpbis-p5-range-03">HTTP/1.1, part 5: Range Requests and Partial Responses</a>”, Internet-Draft&nbsp;draft-ietf-httpbis-p5-range-03 (work in progress), June&nbsp;2008.
    21722313            </td>
    21732314         </tr>
    21742315         <tr>
    21752316            <td class="reference"><b id="Part6">[Part6]</b></td>
    2176             <td class="top"><a href="mailto:fielding@gbiv.com" title="Day Software">Fielding, R., Ed.</a>, <a href="mailto:jg@laptop.org" title="One Laptop per Child">Gettys, J.</a>, <a href="mailto:JeffMogul@acm.org" title="Hewlett-Packard Company">Mogul, J.</a>, <a href="mailto:henrikn@microsoft.com" title="Microsoft Corporation">Frystyk, H.</a>, <a href="mailto:LMM@acm.org" title="Adobe Systems, Incorporated">Masinter, L.</a>, <a href="mailto:paulle@microsoft.com" title="Microsoft Corporation">Leach, P.</a>, <a href="mailto:timbl@w3.org" title="World Wide Web Consortium">Berners-Lee, T.</a>, <a href="mailto:ylafon@w3.org" title="World Wide Web Consortium">Lafon, Y., Ed.</a>, and <a href="mailto:julian.reschke@greenbytes.de" title="greenbytes GmbH">J. Reschke, Ed.</a>, “<a href="http://tools.ietf.org/html/draft-ietf-httpbis-p6-cache-03">HTTP/1.1, part 6: Caching</a>”, Internet-Draft&nbsp;draft-ietf-httpbis-p6-cache-03 (work in progress), June&nbsp;2008.
     2317            <td class="top"><a href="mailto:fielding@gbiv.com" title="Day Software">Fielding, R., Ed.</a>, <a href="mailto:jg@laptop.org" title="One Laptop per Child">Gettys, J.</a>, <a href="mailto:JeffMogul@acm.org" title="Hewlett-Packard Company">Mogul, J.</a>, <a href="mailto:henrikn@microsoft.com" title="Microsoft Corporation">Frystyk, H.</a>, <a href="mailto:LMM@acm.org" title="Adobe Systems, Incorporated">Masinter, L.</a>, <a href="mailto:paulle@microsoft.com" title="Microsoft Corporation">Leach, P.</a>, <a href="mailto:timbl@w3.org" title="World Wide Web Consortium">Berners-Lee, T.</a>, <a href="mailto:ylafon@w3.org" title="World Wide Web Consortium">Lafon, Y., Ed.</a>, and <a href="mailto:julian.reschke@greenbytes.de" title="greenbytes GmbH">J. Reschke, Ed.</a>, “<a href="https://tools.ietf.org/html/draft-ietf-httpbis-p6-cache-03">HTTP/1.1, part 6: Caching</a>”, Internet-Draft&nbsp;draft-ietf-httpbis-p6-cache-03 (work in progress), June&nbsp;2008.
    21772318            </td>
    21782319         </tr>
    21792320         <tr>
    21802321            <td class="reference"><b id="RFC2045">[RFC2045]</b></td>
    2181             <td class="top"><a href="mailto:ned@innosoft.com" title="Innosoft International, Inc.">Freed, N.</a> and <a href="mailto:nsb@nsb.fv.com" title="First Virtual Holdings">N. Borenstein</a>, “<a href="http://tools.ietf.org/html/rfc2045">Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies</a>”, RFC&nbsp;2045, November&nbsp;1996.
     2322            <td class="top"><a href="mailto:ned@innosoft.com" title="Innosoft International, Inc.">Freed, N.</a> and <a href="mailto:nsb@nsb.fv.com" title="First Virtual Holdings">N. Borenstein</a>, “<a href="https://tools.ietf.org/html/rfc2045">Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies</a>”, RFC&nbsp;2045, November&nbsp;1996.
    21822323            </td>
    21832324         </tr>
    21842325         <tr>
    21852326            <td class="reference"><b id="RFC2047">[RFC2047]</b></td>
    2186             <td class="top"><a href="mailto:moore@cs.utk.edu" title="University of Tennessee">Moore, K.</a>, “<a href="http://tools.ietf.org/html/rfc2047">MIME (Multipurpose Internet Mail Extensions) Part Three: Message Header Extensions for Non-ASCII Text</a>”, RFC&nbsp;2047, November&nbsp;1996.
     2327            <td class="top"><a href="mailto:moore@cs.utk.edu" title="University of Tennessee">Moore, K.</a>, “<a href="https://tools.ietf.org/html/rfc2047">MIME (Multipurpose Internet Mail Extensions) Part Three: Message Header Extensions for Non-ASCII Text</a>”, RFC&nbsp;2047, November&nbsp;1996.
    21872328            </td>
    21882329         </tr>
    21892330         <tr>
    21902331            <td class="reference"><b id="RFC2119">[RFC2119]</b></td>
    2191             <td class="top"><a href="mailto:sob@harvard.edu" title="Harvard University">Bradner, S.</a>, “<a href="http://tools.ietf.org/html/rfc2119">Key words for use in RFCs to Indicate Requirement Levels</a>”, BCP&nbsp;14, RFC&nbsp;2119, March&nbsp;1997.
     2332            <td class="top"><a href="mailto:sob@harvard.edu" title="Harvard University">Bradner, S.</a>, “<a href="https://tools.ietf.org/html/rfc2119">Key words for use in RFCs to Indicate Requirement Levels</a>”, BCP&nbsp;14, RFC&nbsp;2119, March&nbsp;1997.
    21922333            </td>
    21932334         </tr>
    21942335         <tr>
    21952336            <td class="reference"><b id="RFC2396">[RFC2396]</b></td>
    2196             <td class="top"><a href="mailto:timbl@w3.org" title="World Wide Web Consortium">Berners-Lee, T.</a>, <a href="mailto:fielding@ics.uci.edu" title="Department of Information and Computer Science">Fielding, R.</a>, and <a href="mailto:masinter@parc.xerox.com" title="Xerox PARC">L. Masinter</a>, “<a href="http://tools.ietf.org/html/rfc2396">Uniform Resource Identifiers (URI): Generic Syntax</a>”, RFC&nbsp;2396, August&nbsp;1998.
     2337            <td class="top"><a href="mailto:timbl@w3.org" title="World Wide Web Consortium">Berners-Lee, T.</a>, <a href="mailto:fielding@ics.uci.edu" title="Department of Information and Computer Science">Fielding, R.</a>, and <a href="mailto:masinter@parc.xerox.com" title="Xerox PARC">L. Masinter</a>, “<a href="https://tools.ietf.org/html/rfc2396">Uniform Resource Identifiers (URI): Generic Syntax</a>”, RFC&nbsp;2396, August&nbsp;1998.
    21972338            </td>
    21982339         </tr>
    21992340         <tr>
    22002341            <td class="reference"><b id="RFC822ABNF">[RFC822ABNF]</b></td>
    2201             <td class="top"><a href="mailto:DCrocker@UDel-Relay" title="University of Delaware, Dept. of Electrical Engineering">Crocker, D.</a>, “<a href="http://tools.ietf.org/html/rfc822">Standard for the format of ARPA Internet text messages</a>”, STD&nbsp;11, RFC&nbsp;822, August&nbsp;1982.
     2342            <td class="top"><a href="mailto:DCrocker@UDel-Relay" title="University of Delaware, Dept. of Electrical Engineering">Crocker, D.</a>, “<a href="https://tools.ietf.org/html/rfc822">Standard for the format of ARPA Internet text messages</a>”, STD&nbsp;11, RFC&nbsp;822, August&nbsp;1982.
    22022343            </td>
    22032344         </tr>
     
    22092350      <h2 id="rfc.references.2"><a href="#rfc.section.12.2" id="rfc.section.12.2">12.2</a> Informative References
    22102351      </h2>
    2211       <table>                                                 
     2352      <table>
    22122353         <tr>
    22132354            <td class="reference"><b id="Nie1997">[Nie1997]</b></td>
     
    22242365         <tr>
    22252366            <td class="reference"><b id="RFC1123">[RFC1123]</b></td>
    2226             <td class="top"><a href="mailto:Braden@ISI.EDU" title="University of Southern California (USC), Information Sciences Institute">Braden, R.</a>, “<a href="http://tools.ietf.org/html/rfc1123">Requirements for Internet Hosts - Application and Support</a>”, STD&nbsp;3, RFC&nbsp;1123, October&nbsp;1989.
     2367            <td class="top"><a href="mailto:Braden@ISI.EDU" title="University of Southern California (USC), Information Sciences Institute">Braden, R.</a>, “<a href="https://tools.ietf.org/html/rfc1123">Requirements for Internet Hosts - Application and Support</a>”, STD&nbsp;3, RFC&nbsp;1123, October&nbsp;1989.
    22272368            </td>
    22282369         </tr>
    22292370         <tr>
    22302371            <td class="reference"><b id="RFC1305">[RFC1305]</b></td>
    2231             <td class="top"><a href="mailto:mills@udel.edu" title="University of Delaware, Electrical Engineering Department">Mills, D.</a>, “<a href="http://tools.ietf.org/html/rfc1305">Network Time Protocol (Version 3) Specification, Implementation</a>”, RFC&nbsp;1305, March&nbsp;1992.
     2372            <td class="top"><a href="mailto:mills@udel.edu" title="University of Delaware, Electrical Engineering Department">Mills, D.</a>, “<a href="https://tools.ietf.org/html/rfc1305">Network Time Protocol (Version 3) Specification, Implementation</a>”, RFC&nbsp;1305, March&nbsp;1992.
    22322373            </td>
    22332374         </tr>
    22342375         <tr>
    22352376            <td class="reference"><b id="RFC1436">[RFC1436]</b></td>
    2236             <td class="top"><a href="mailto:fxa@boombox.micro.umn.edu" title="University of Minnesota, Computer and Information Services">Anklesaria, F.</a>, <a href="mailto:mpm@boombox.micro.umn.edu" title="University of Minnesota, Computer and Information Services">McCahill, M.</a>, <a href="mailto:lindner@boombox.micro.umn.edu" title="University of Minnesota, Computer and Information Services">Lindner, P.</a>, <a href="mailto:dmj@boombox.micro.umn.edu" title="University of Minnesota, Computer and Information Services">Johnson, D.</a>, <a href="mailto:daniel@boombox.micro.umn.edu" title="University of Minnesota, Computer and Information Services">Torrey, D.</a>, and <a href="mailto:alberti@boombox.micro.umn.edu" title="University of Minnesota, Computer and Information Services">B. Alberti</a>, “<a href="http://tools.ietf.org/html/rfc1436">The Internet Gopher Protocol (a distributed document search and retrieval protocol)</a>”, RFC&nbsp;1436, March&nbsp;1993.
     2377            <td class="top"><a href="mailto:fxa@boombox.micro.umn.edu" title="University of Minnesota, Computer and Information Services">Anklesaria, F.</a>, <a href="mailto:mpm@boombox.micro.umn.edu" title="University of Minnesota, Computer and Information Services">McCahill, M.</a>, <a href="mailto:lindner@boombox.micro.umn.edu" title="University of Minnesota, Computer and Information Services">Lindner, P.</a>, <a href="mailto:dmj@boombox.micro.umn.edu" title="University of Minnesota, Computer and Information Services">Johnson, D.</a>, <a href="mailto:daniel@boombox.micro.umn.edu" title="University of Minnesota, Computer and Information Services">Torrey, D.</a>, and <a href="mailto:alberti@boombox.micro.umn.edu" title="University of Minnesota, Computer and Information Services">B. Alberti</a>, “<a href="https://tools.ietf.org/html/rfc1436">The Internet Gopher Protocol (a distributed document search and retrieval protocol)</a>”, RFC&nbsp;1436, March&nbsp;1993.
    22372378            </td>
    22382379         </tr>
    22392380         <tr>
    22402381            <td class="reference"><b id="RFC1630">[RFC1630]</b></td>
    2241             <td class="top"><a href="mailto:timbl@info.cern.ch" title="CERN, World-Wide Web project">Berners-Lee, T.</a>, “<a href="http://tools.ietf.org/html/rfc1630">Universal Resource Identifiers in WWW: A Unifying Syntax for the Expression of Names and Addresses of Objects on the Network
     2382            <td class="top"><a href="mailto:timbl@info.cern.ch" title="CERN, World-Wide Web project">Berners-Lee, T.</a>, “<a href="https://tools.ietf.org/html/rfc1630">Universal Resource Identifiers in WWW: A Unifying Syntax for the Expression of Names and Addresses of Objects on the Network
    22422383                  as used in the World-Wide Web</a>”, RFC&nbsp;1630, June&nbsp;1994.
    22432384            </td>
     
    22452386         <tr>
    22462387            <td class="reference"><b id="RFC1737">[RFC1737]</b></td>
    2247             <td class="top"><a href="mailto:masinter@parc.xerox.com" title="Xerox Palo Alto Research Center">Masinter, L.</a> and <a href="mailto:sollins@lcs.mit.edu" title="MIT Laboratory for Computer Science">K. Sollins</a>, “<a href="http://tools.ietf.org/html/rfc1737">Functional Requirements for Uniform Resource Names</a>”, RFC&nbsp;1737, December&nbsp;1994.
     2388            <td class="top"><a href="mailto:masinter@parc.xerox.com" title="Xerox Palo Alto Research Center">Masinter, L.</a> and <a href="mailto:sollins@lcs.mit.edu" title="MIT Laboratory for Computer Science">K. Sollins</a>, “<a href="https://tools.ietf.org/html/rfc1737">Functional Requirements for Uniform Resource Names</a>”, RFC&nbsp;1737, December&nbsp;1994.
    22482389            </td>
    22492390         </tr>
    22502391         <tr>
    22512392            <td class="reference"><b id="RFC1738">[RFC1738]</b></td>
    2252             <td class="top"><a href="mailto:timbl@info.cern.ch" title="CERN, World-Wide Web project">Berners-Lee, T.</a>, <a href="mailto:masinter@parc.xerox.com" title="Xerox PARC">Masinter, L.</a>, and <a href="mailto:mpm@boombox.micro.umn.edu" title="University of Minnesota, Computer and Information Services">M. McCahill</a>, “<a href="http://tools.ietf.org/html/rfc1738">Uniform Resource Locators (URL)</a>”, RFC&nbsp;1738, December&nbsp;1994.
     2393            <td class="top"><a href="mailto:timbl@info.cern.ch" title="CERN, World-Wide Web project">Berners-Lee, T.</a>, <a href="mailto:masinter@parc.xerox.com" title="Xerox PARC">Masinter, L.</a>, and <a href="mailto:mpm@boombox.micro.umn.edu" title="University of Minnesota, Computer and Information Services">M. McCahill</a>, “<a href="https://tools.ietf.org/html/rfc1738">Uniform Resource Locators (URL)</a>”, RFC&nbsp;1738, December&nbsp;1994.
    22532394            </td>
    22542395         </tr>
    22552396         <tr>
    22562397            <td class="reference"><b id="RFC1808">[RFC1808]</b></td>
    2257             <td class="top"><a href="mailto:fielding@ics.uci.edu" title="University of California Irvine, Department of Information and Computer Science">Fielding, R.</a>, “<a href="http://tools.ietf.org/html/rfc1808">Relative Uniform Resource Locators</a>”, RFC&nbsp;1808, June&nbsp;1995.
     2398            <td class="top"><a href="mailto:fielding@ics.uci.edu" title="University of California Irvine, Department of Information and Computer Science">Fielding, R.</a>, “<a href="https://tools.ietf.org/html/rfc1808">Relative Uniform Resource Locators</a>”, RFC&nbsp;1808, June&nbsp;1995.
    22582399            </td>
    22592400         </tr>
    22602401         <tr>
    22612402            <td class="reference"><b id="RFC1900">[RFC1900]</b></td>
    2262             <td class="top"><a href="mailto:brian@dxcoms.cern.ch" title="CERN, Computing and Networks Division">Carpenter, B.</a> and <a href="mailto:yakov@cisco.com" title="cisco Systems">Y. Rekhter</a>, “<a href="http://tools.ietf.org/html/rfc1900">Renumbering Needs Work</a>”, RFC&nbsp;1900, February&nbsp;1996.
     2403            <td class="top"><a href="mailto:brian@dxcoms.cern.ch" title="CERN, Computing and Networks Division">Carpenter, B.</a> and <a href="mailto:yakov@cisco.com" title="cisco Systems">Y. Rekhter</a>, “<a href="https://tools.ietf.org/html/rfc1900">Renumbering Needs Work</a>”, RFC&nbsp;1900, February&nbsp;1996.
    22632404            </td>
    22642405         </tr>
    22652406         <tr>
    22662407            <td class="reference"><b id="RFC1945">[RFC1945]</b></td>
    2267             <td class="top"><a href="mailto:timbl@w3.org" title="MIT, Laboratory for Computer Science">Berners-Lee, T.</a>, <a href="mailto:fielding@ics.uci.edu" title="University of California, Irvine, Department of Information and Computer Science">Fielding, R.</a>, and <a href="mailto:frystyk@w3.org" title="W3 Consortium, MIT Laboratory for Computer Science">H. Nielsen</a>, “<a href="http://tools.ietf.org/html/rfc1945">Hypertext Transfer Protocol -- HTTP/1.0</a>”, RFC&nbsp;1945, May&nbsp;1996.
     2408            <td class="top"><a href="mailto:timbl@w3.org" title="MIT, Laboratory for Computer Science">Berners-Lee, T.</a>, <a href="mailto:fielding@ics.uci.edu" title="University of California, Irvine, Department of Information and Computer Science">Fielding, R.</a>, and <a href="mailto:frystyk@w3.org" title="W3 Consortium, MIT Laboratory for Computer Science">H. Nielsen</a>, “<a href="https://tools.ietf.org/html/rfc1945">Hypertext Transfer Protocol -- HTTP/1.0</a>”, RFC&nbsp;1945, May&nbsp;1996.
    22682409            </td>
    22692410         </tr>
    22702411         <tr>
    22712412            <td class="reference"><b id="RFC2068">[RFC2068]</b></td>
    2272             <td class="top"><a href="mailto:fielding@ics.uci.edu" title="University of California, Irvine, Department of Information and Computer Science">Fielding, R.</a>, <a href="mailto:jg@w3.org" title="MIT Laboratory for Computer Science">Gettys, J.</a>, <a href="mailto:mogul@wrl.dec.com" title="Digital Equipment Corporation, Western Research Laboratory">Mogul, J.</a>, <a href="mailto:frystyk@w3.org" title="MIT Laboratory for Computer Science">Nielsen, H.</a>, and <a href="mailto:timbl@w3.org" title="MIT Laboratory for Computer Science">T. Berners-Lee</a>, “<a href="http://tools.ietf.org/html/rfc2068">Hypertext Transfer Protocol -- HTTP/1.1</a>”, RFC&nbsp;2068, January&nbsp;1997.
     2413            <td class="top"><a href="mailto:fielding@ics.uci.edu" title="University of California, Irvine, Department of Information and Computer Science">Fielding, R.</a>, <a href="mailto:jg@w3.org" title="MIT Laboratory for Computer Science">Gettys, J.</a>, <a href="mailto:mogul@wrl.dec.com" title="Digital Equipment Corporation, Western Research Laboratory">Mogul, J.</a>, <a href="mailto:frystyk@w3.org" title="MIT Laboratory for Computer Science">Nielsen, H.</a>, and <a href="mailto:timbl@w3.org" title="MIT Laboratory for Computer Science">T. Berners-Lee</a>, “<a href="https://tools.ietf.org/html/rfc2068">Hypertext Transfer Protocol -- HTTP/1.1</a>”, RFC&nbsp;2068, January&nbsp;1997.
    22732414            </td>
    22742415         </tr>
    22752416         <tr>
    22762417            <td class="reference"><b id="RFC2145">[RFC2145]</b></td>
    2277             <td class="top"><a href="mailto:mogul@wrl.dec.com" title="Western Research Laboratory">Mogul, J.</a>, <a href="mailto:fielding@ics.uci.edu" title="Department of Information and Computer Science">Fielding, R.</a>, <a href="mailto:jg@w3.org" title="MIT Laboratory for Computer Science">Gettys, J.</a>, and <a href="mailto:frystyk@w3.org" title="W3 Consortium">H. Nielsen</a>, “<a href="http://tools.ietf.org/html/rfc2145">Use and Interpretation of HTTP Version Numbers</a>”, RFC&nbsp;2145, May&nbsp;1997.
     2418            <td class="top"><a href="mailto:mogul@wrl.dec.com" title="Western Research Laboratory">Mogul, J.</a>, <a href="mailto:fielding@ics.uci.edu" title="Department of Information and Computer Science">Fielding, R.</a>, <a href="mailto:jg@w3.org" title="MIT Laboratory for Computer Science">Gettys, J.</a>, and <a href="mailto:frystyk@w3.org" title="W3 Consortium">H. Nielsen</a>, “<a href="https://tools.ietf.org/html/rfc2145">Use and Interpretation of HTTP Version Numbers</a>”, RFC&nbsp;2145, May&nbsp;1997.
    22782419            </td>
    22792420         </tr>
    22802421         <tr>
    22812422            <td class="reference"><b id="RFC2324">[RFC2324]</b></td>
    2282             <td class="top"><a href="mailto:masinter@parc.xerox.com" title="Xerox Palo Alto Research Center">Masinter, L.</a>, “<a href="http://tools.ietf.org/html/rfc2324">Hyper Text Coffee Pot Control Protocol (HTCPCP/1.0)</a>”, RFC&nbsp;2324, April&nbsp;1998.
     2423            <td class="top"><a href="mailto:masinter@parc.xerox.com" title="Xerox Palo Alto Research Center">Masinter, L.</a>, “<a href="https://tools.ietf.org/html/rfc2324">Hyper Text Coffee Pot Control Protocol (HTCPCP/1.0)</a>”, RFC&nbsp;2324, April&nbsp;1998.
    22832424            </td>
    22842425         </tr>
    22852426         <tr>
    22862427            <td class="reference"><b id="RFC2616">[RFC2616]</b></td>
    2287             <td class="top"><a href="mailto:fielding@ics.uci.edu" title="University of California, Irvine">Fielding, R.</a>, <a href="mailto:jg@w3.org" title="W3C">Gettys, J.</a>, <a href="mailto:mogul@wrl.dec.com" title="Compaq Computer Corporation">Mogul, J.</a>, <a href="mailto:frystyk@w3.org" title="MIT Laboratory for Computer Science">Frystyk, H.</a>, <a href="mailto:masinter@parc.xerox.com" title="Xerox Corporation">Masinter, L.</a>, <a href="mailto:paulle@microsoft.com" title="Microsoft Corporation">Leach, P.</a>, and <a href="mailto:timbl@w3.org" title="W3C">T. Berners-Lee</a>, “<a href="http://tools.ietf.org/html/rfc2616">Hypertext Transfer Protocol -- HTTP/1.1</a>”, RFC&nbsp;2616, June&nbsp;1999.
     2428            <td class="top"><a href="mailto:fielding@ics.uci.edu" title="University of California, Irvine">Fielding, R.</a>, <a href="mailto:jg@w3.org" title="W3C">Gettys, J.</a>, <a href="mailto:mogul@wrl.dec.com" title="Compaq Computer Corporation">Mogul, J.</a>, <a href="mailto:frystyk@w3.org" title="MIT Laboratory for Computer Science">Frystyk, H.</a>, <a href="mailto:masinter@parc.xerox.com" title="Xerox Corporation">Masinter, L.</a>, <a href="mailto:paulle@microsoft.com" title="Microsoft Corporation">Leach, P.</a>, and <a href="mailto:timbl@w3.org" title="W3C">T. Berners-Lee</a>, “<a href="https://tools.ietf.org/html/rfc2616">Hypertext Transfer Protocol -- HTTP/1.1</a>”, RFC&nbsp;2616, June&nbsp;1999.
    22882429            </td>
    22892430         </tr>
    22902431         <tr>
    22912432            <td class="reference"><b id="RFC2821">[RFC2821]</b></td>
    2292             <td class="top"><a href="mailto:klensin@research.att.com" title="AT&amp;T Laboratories">Klensin, J.</a>, “<a href="http://tools.ietf.org/html/rfc2821">Simple Mail Transfer Protocol</a>”, RFC&nbsp;2821, April&nbsp;2001.
     2433            <td class="top"><a href="mailto:klensin@research.att.com" title="AT&amp;T Laboratories">Klensin, J.</a>, “<a href="https://tools.ietf.org/html/rfc2821">Simple Mail Transfer Protocol</a>”, RFC&nbsp;2821, April&nbsp;2001.
    22932434            </td>
    22942435         </tr>
    22952436         <tr>
    22962437            <td class="reference"><b id="RFC2822">[RFC2822]</b></td>
    2297             <td class="top">Resnick, P., “<a href="http://tools.ietf.org/html/rfc2822">Internet Message Format</a>”, RFC&nbsp;2822, April&nbsp;2001.
     2438            <td class="top">Resnick, P., “<a href="https://tools.ietf.org/html/rfc2822">Internet Message Format</a>”, RFC&nbsp;2822, April&nbsp;2001.
    22982439            </td>
    22992440         </tr>
    23002441         <tr>
    23012442            <td class="reference"><b id="RFC3864">[RFC3864]</b></td>
    2302             <td class="top"><a href="mailto:GK-IETF@ninebynine.org" title="Nine by Nine">Klyne, G.</a>, <a href="mailto:mnot@pobox.com" title="BEA Systems">Nottingham, M.</a>, and <a href="mailto:JeffMogul@acm.org" title="HP Labs">J. Mogul</a>, “<a href="http://tools.ietf.org/html/rfc3864">Registration Procedures for Message Header Fields</a>”, BCP&nbsp;90, RFC&nbsp;3864, September&nbsp;2004.
     2443            <td class="top"><a href="mailto:GK-IETF@ninebynine.org" title="Nine by Nine">Klyne, G.</a>, <a href="mailto:mnot@pobox.com" title="BEA Systems">Nottingham, M.</a>, and <a href="mailto:JeffMogul@acm.org" title="HP Labs">J. Mogul</a>, “<a href="https://tools.ietf.org/html/rfc3864">Registration Procedures for Message Header Fields</a>”, BCP&nbsp;90, RFC&nbsp;3864, September&nbsp;2004.
    23032444            </td>
    23042445         </tr>
    23052446         <tr>
    23062447            <td class="reference"><b id="RFC3977">[RFC3977]</b></td>
    2307             <td class="top"><a href="mailto:clive@demon.net" title="THUS plc">Feather, C.</a>, “<a href="http://tools.ietf.org/html/rfc3977">Network News Transfer Protocol (NNTP)</a>”, RFC&nbsp;3977, October&nbsp;2006.
     2448            <td class="top"><a href="mailto:clive@demon.net" title="THUS plc">Feather, C.</a>, “<a href="https://tools.ietf.org/html/rfc3977">Network News Transfer Protocol (NNTP)</a>”, RFC&nbsp;3977, October&nbsp;2006.
    23082449            </td>
    23092450         </tr>
    23102451         <tr>
    23112452            <td class="reference"><b id="RFC4288">[RFC4288]</b></td>
    2312             <td class="top"><a href="mailto:ned.freed@mrochek.com" title="Sun Microsystems">Freed, N.</a> and <a href="mailto:klensin+ietf@jck.com">J. Klensin</a>, “<a href="http://tools.ietf.org/html/rfc4288">Media Type Specifications and Registration Procedures</a>”, BCP&nbsp;13, RFC&nbsp;4288, December&nbsp;2005.
     2453            <td class="top"><a href="mailto:ned.freed@mrochek.com" title="Sun Microsystems">Freed, N.</a> and <a href="mailto:klensin+ietf@jck.com">J. Klensin</a>, “<a href="https://tools.ietf.org/html/rfc4288">Media Type Specifications and Registration Procedures</a>”, BCP&nbsp;13, RFC&nbsp;4288, December&nbsp;2005.
    23132454            </td>
    23142455         </tr>
    23152456         <tr>
    23162457            <td class="reference"><b id="RFC822">[RFC822]</b></td>
    2317             <td class="top"><a href="mailto:DCrocker@UDel-Relay" title="University of Delaware, Dept. of Electrical Engineering">Crocker, D.</a>, “<a href="http://tools.ietf.org/html/rfc822">Standard for the format of ARPA Internet text messages</a>”, STD&nbsp;11, RFC&nbsp;822, August&nbsp;1982.
     2458            <td class="top"><a href="mailto:DCrocker@UDel-Relay" title="University of Delaware, Dept. of Electrical Engineering">Crocker, D.</a>, “<a href="https://tools.ietf.org/html/rfc822">Standard for the format of ARPA Internet text messages</a>”, STD&nbsp;11, RFC&nbsp;822, August&nbsp;1982.
    23182459            </td>
    23192460         </tr>
    23202461         <tr>
    23212462            <td class="reference"><b id="RFC959">[RFC959]</b></td>
    2322             <td class="top">Postel, J. and J. Reynolds, “<a href="http://tools.ietf.org/html/rfc959">File Transfer Protocol</a>”, STD&nbsp;9, RFC&nbsp;959, October&nbsp;1985.
     2463            <td class="top">Postel, J. and J. Reynolds, “<a href="https://tools.ietf.org/html/rfc959">File Transfer Protocol</a>”, STD&nbsp;9, RFC&nbsp;959, October&nbsp;1985.
    23232464            </td>
    23242465         </tr>
     
    23382479         </tr>
    23392480      </table>
    2340       <div class="avoidbreak">
    2341          <h1 id="rfc.authors"><a href="#rfc.authors">Authors' Addresses</a></h1>
    2342          <address class="vcard"><span class="vcardline"><span class="fn">Roy T. Fielding</span>
    2343                (editor)
    2344                <span class="n hidden"><span class="family-name">Fielding</span><span class="given-name">Roy T.</span></span></span><span class="org vcardline">Day Software</span><span class="adr"><span class="street-address vcardline">23 Corporate Plaza DR, Suite 280</span><span class="vcardline"><span class="locality">Newport Beach</span>, <span class="region">CA</span>&nbsp;<span class="postal-code">92660</span></span><span class="country-name vcardline">USA</span></span><span class="vcardline tel">Phone: <a href="tel:+1-949-706-5300"><span class="value">+1-949-706-5300</span></a></span><span class="vcardline tel"><span class="type">Fax</span>: <a href="fax:+1-949-706-5305"><span class="value">+1-949-706-5305</span></a></span><span class="vcardline">EMail: <a href="mailto:fielding@gbiv.com"><span class="email">fielding@gbiv.com</span></a></span><span class="vcardline">URI: <a href="http://roy.gbiv.com/" class="url">http://roy.gbiv.com/</a></span></address>
    2345          <address class="vcard"><span class="vcardline"><span class="fn">Jim Gettys</span><span class="n hidden"><span class="family-name">Gettys</span><span class="given-name">Jim</span></span></span><span class="org vcardline">One Laptop per Child</span><span class="adr"><span class="street-address vcardline">21 Oak Knoll Road</span><span class="vcardline"><span class="locality">Carlisle</span>, <span class="region">MA</span>&nbsp;<span class="postal-code">01741</span></span><span class="country-name vcardline">USA</span></span><span class="vcardline">EMail: <a href="mailto:jg@laptop.org"><span class="email">jg@laptop.org</span></a></span><span class="vcardline">URI: <a href="http://www.laptop.org/" class="url">http://www.laptop.org/</a></span></address>
    2346          <address class="vcard"><span class="vcardline"><span class="fn">Jeffrey C. Mogul</span><span class="n hidden"><span class="family-name">Mogul</span><span class="given-name">Jeffrey C.</span></span></span><span class="org vcardline">Hewlett-Packard Company</span><span class="adr"><span class="street-address vcardline">HP Labs, Large Scale Systems Group</span><span class="street-address vcardline">1501 Page Mill Road, MS 1177</span><span class="vcardline"><span class="locality">Palo Alto</span>, <span class="region">CA</span>&nbsp;<span class="postal-code">94304</span></span><span class="country-name vcardline">USA</span></span><span class="vcardline">EMail: <a href="mailto:JeffMogul@acm.org"><span class="email">JeffMogul@acm.org</span></a></span></address>
    2347          <address class="vcard"><span class="vcardline"><span class="fn">Henrik Frystyk Nielsen</span><span class="n hidden"><span class="family-name">Frystyk</span></span></span><span class="org vcardline">Microsoft Corporation</span><span class="adr"><span class="street-address vcardline">1 Microsoft Way</span><span class="vcardline"><span class="locality">Redmond</span>, <span class="region">WA</span>&nbsp;<span class="postal-code">98052</span></span><span class="country-name vcardline">USA</span></span><span class="vcardline">EMail: <a href="mailto:henrikn@microsoft.com"><span class="email">henrikn@microsoft.com</span></a></span></address>
    2348          <address class="vcard"><span class="vcardline"><span class="fn">Larry Masinter</span><span class="n hidden"><span class="family-name">Masinter</span><span class="given-name">Larry</span></span></span><span class="org vcardline">Adobe Systems, Incorporated</span><span class="adr"><span class="street-address vcardline">345 Park Ave</span><span class="vcardline"><span class="locality">San Jose</span>, <span class="region">CA</span>&nbsp;<span class="postal-code">95110</span></span><span class="country-name vcardline">USA</span></span><span class="vcardline">EMail: <a href="mailto:LMM@acm.org"><span class="email">LMM@acm.org</span></a></span><span class="vcardline">URI: <a href="http://larry.masinter.net/" class="url">http://larry.masinter.net/</a></span></address>
    2349          <address class="vcard"><span class="vcardline"><span class="fn">Paul J. Leach</span><span class="n hidden"><span class="family-name">Leach</span><span class="given-name">Paul J.</span></span></span><span class="org vcardline">Microsoft Corporation</span><span class="adr"><span class="street-address vcardline">1 Microsoft Way</span><span class="vcardline"><span class="locality">Redmond</span>, <span class="region">WA</span>&nbsp;<span class="postal-code">98052</span></span></span><span class="vcardline">EMail: <a href="mailto:paulle@microsoft.com"><span class="email">paulle@microsoft.com</span></a></span></address>
    2350          <address class="vcard"><span class="vcardline"><span class="fn">Tim Berners-Lee</span><span class="n hidden"><span class="family-name">Berners-Lee</span><span class="given-name">Tim</span></span></span><span class="org vcardline">World Wide Web Consortium</span><span class="adr"><span class="street-address vcardline">MIT Computer Science and Artificial Intelligence Laboratory</span><span class="street-address vcardline">The Stata Center, Building 32</span><span class="street-address vcardline">32 Vassar Street</span><span class="vcardline"><span class="locality">Cambridge</span>, <span class="region">MA</span>&nbsp;<span class="postal-code">02139</span></span><span class="country-name vcardline">USA</span></span><span class="vcardline">EMail: <a href="mailto:timbl@w3.org"><span class="email">timbl@w3.org</span></a></span><span class="vcardline">URI: <a href="http://www.w3.org/People/Berners-Lee/" class="url">http://www.w3.org/People/Berners-Lee/</a></span></address>
    2351          <address class="vcard"><span class="vcardline"><span class="fn">Yves Lafon</span>
    2352                (editor)
    2353                <span class="n hidden"><span class="family-name">Lafon</span><span class="given-name">Yves</span></span></span><span class="org vcardline">World Wide Web Consortium</span><span class="adr"><span class="street-address vcardline">W3C / ERCIM</span><span class="street-address vcardline">2004, rte des Lucioles</span><span class="vcardline"><span class="locality">Sophia-Antipolis</span>, <span class="region">AM</span>&nbsp;<span class="postal-code">06902</span></span><span class="country-name vcardline">France</span></span><span class="vcardline">EMail: <a href="mailto:ylafon@w3.org"><span class="email">ylafon@w3.org</span></a></span><span class="vcardline">URI: <a href="http://www.raubacapeu.net/people/yves/" class="url">http://www.raubacapeu.net/people/yves/</a></span></address>
    2354          <address class="vcard"><span class="vcardline"><span class="fn">Julian F. Reschke</span>
    2355                (editor)
    2356                <span class="n hidden"><span class="family-name">Reschke</span><span class="given-name">Julian F.</span></span></span><span class="org vcardline">greenbytes GmbH</span><span class="adr"><span class="street-address vcardline">Hafenweg 16</span><span class="vcardline"><span class="locality">Muenster</span>, <span class="region">NW</span>&nbsp;<span class="postal-code">48155</span></span><span class="country-name vcardline">Germany</span></span><span class="vcardline tel">Phone: <a href="tel:+492512807760"><span class="value">+49 251 2807760</span></a></span><span class="vcardline tel"><span class="type">Fax</span>: <a href="fax:+492512807761"><span class="value">+49 251 2807761</span></a></span><span class="vcardline">EMail: <a href="mailto:julian.reschke@greenbytes.de"><span class="email">julian.reschke@greenbytes.de</span></a></span><span class="vcardline">URI: <a href="http://greenbytes.de/tech/webdav/" class="url">http://greenbytes.de/tech/webdav/</a></span></address>
     2481      <div id="internet.media.type.http">
     2482         <h1 id="rfc.section.A" class="np"><a href="#rfc.section.A">A.</a>&nbsp;<a href="#internet.media.type.http">Internet Media Types</a></h1>
     2483         <p id="rfc.section.A.p.1">In addition to defining HTTP/1.1, this document serves as the specification for the Internet media type "message/http" and
     2484            "application/http". The following is to be registered with IANA <a href="#RFC4288" id="rfc.xref.RFC4288.1"><cite title="Media Type Specifications and Registration Procedures">[RFC4288]</cite></a>.
     2485         </p>
     2486         <div id="internet.media.type.message.http">
     2487            <div id="rfc.iref.m.2"></div>
     2488            <div id="rfc.iref.m.3"></div>
     2489            <h2 id="rfc.section.A.1"><a href="#rfc.section.A.1">A.1</a>&nbsp;<a href="#internet.media.type.message.http">Internet Media Type message/http</a></h2>
     2490            <p id="rfc.section.A.1.p.1">The message/http type can be used to enclose a single HTTP request or response message, provided that it obeys the MIME restrictions
     2491               for all "message" types regarding line length and encodings.
     2492            </p>
     2493            <p id="rfc.section.A.1.p.2"></p>
     2494            <dl>
     2495               <dt>Type name:</dt>
     2496               <dd>message</dd>
     2497               <dt>Subtype name:</dt>
     2498               <dd>http</dd>
     2499               <dt>Required parameters:</dt>
     2500               <dd>none</dd>
     2501               <dt>Optional parameters:</dt>
     2502               <dd>version, msgtype
     2503                  <dl>
     2504                     <dt>version:</dt>
     2505                     <dd>The HTTP-Version number of the enclosed message (e.g., "1.1"). If not present, the version can be determined from the first
     2506                        line of the body.
     2507                     </dd>
     2508                     <dt>msgtype:</dt>
     2509                     <dd>The message type -- "request" or "response". If not present, the type can be determined from the first line of the body.</dd>
     2510                  </dl>
     2511               </dd>
     2512               <dt>Encoding considerations:</dt>
     2513               <dd>only "7bit", "8bit", or "binary" are permitted</dd>
     2514               <dt>Security considerations:</dt>
     2515               <dd>none</dd>
     2516               <dt>Interoperability considerations:</dt>
     2517               <dd>none</dd>
     2518               <dt>Published specification:</dt>
     2519               <dd>This specification (see <a href="#internet.media.type.message.http" title="Internet Media Type message/http">Appendix&nbsp;A.1</a>).
     2520               </dd>
     2521               <dt>Applications that use this media type:</dt>
     2522               <dt>Additional information:</dt>
     2523               <dd>
     2524                  <dl>
     2525                     <dt>Magic number(s):</dt>
     2526                     <dd>none</dd>
     2527                     <dt>File extension(s):</dt>
     2528                     <dd>none</dd>
     2529                     <dt>Macintosh file type code(s):</dt>
     2530                     <dd>none</dd>
     2531                  </dl>
     2532               </dd>
     2533               <dt>Person and email address to contact for further information:</dt>
     2534               <dd>See Authors Section.</dd>
     2535               <dt>Intended usage:</dt>
     2536               <dd>COMMON</dd>
     2537               <dt>Restrictions on usage:</dt>
     2538               <dd>none</dd>
     2539               <dt>Author/Change controller:</dt>
     2540               <dd>IESG</dd>
     2541            </dl>
     2542         </div>
     2543         <div id="internet.media.type.application.http">
     2544            <div id="rfc.iref.m.4"></div>
     2545            <div id="rfc.iref.a.1"></div>
     2546            <h2 id="rfc.section.A.2"><a href="#rfc.section.A.2">A.2</a>&nbsp;<a href="#internet.media.type.application.http">Internet Media Type application/http</a></h2>
     2547            <p id="rfc.section.A.2.p.1">The application/http type can be used to enclose a pipeline of one or more HTTP request or response messages (not intermixed).</p>
     2548            <p id="rfc.section.A.2.p.2"></p>
     2549            <dl>
     2550               <dt>Type name:</dt>
     2551               <dd>application</dd>
     2552               <dt>Subtype name:</dt>
     2553               <dd>http</dd>
     2554               <dt>Required parameters:</dt>
     2555               <dd>none</dd>
     2556               <dt>Optional parameters:</dt>
     2557               <dd>version, msgtype
     2558                  <dl>
     2559                     <dt>version:</dt>
     2560                     <dd>The HTTP-Version number of the enclosed messages (e.g., "1.1"). If not present, the version can be determined from the first
     2561                        line of the body.
     2562                     </dd>
     2563                     <dt>msgtype:</dt>
     2564                     <dd>The message type -- "request" or "response". If not present, the type can be determined from the first line of the body.</dd>
     2565                  </dl>
     2566               </dd>
     2567               <dt>Encoding considerations:</dt>
     2568               <dd>HTTP messages enclosed by this type are in "binary" format; use of an appropriate Content-Transfer-Encoding is required when
     2569                  transmitted via E-mail.
     2570               </dd>
     2571               <dt>Security considerations:</dt>
     2572               <dd>none</dd>
     2573               <dt>Interoperability considerations:</dt>
     2574               <dd>none</dd>
     2575               <dt>Published specification:</dt>
     2576               <dd>This specification (see <a href="#internet.media.type.application.http" title="Internet Media Type application/http">Appendix&nbsp;A.2</a>).
     2577               </dd>
     2578               <dt>Applications that use this media type:</dt>
     2579               <dt>Additional information:</dt>
     2580               <dd>
     2581                  <dl>
     2582                     <dt>Magic number(s):</dt>
     2583                     <dd>none</dd>
     2584                     <dt>File extension(s):</dt>
     2585                     <dd>none</dd>
     2586                     <dt>Macintosh file type code(s):</dt>
     2587                     <dd>none</dd>
     2588                  </dl>
     2589               </dd>
     2590               <dt>Person and email address to contact for further information:</dt>
     2591               <dd>See Authors Section.</dd>
     2592               <dt>Intended usage:</dt>
     2593               <dd>COMMON</dd>
     2594               <dt>Restrictions on usage:</dt>
     2595               <dd>none</dd>
     2596               <dt>Author/Change controller:</dt>
     2597               <dd>IESG</dd>
     2598            </dl>
     2599         </div>
    23572600      </div>
    2358       <h1 id="rfc.section.A" class="np"><a href="#rfc.section.A">A.</a>&nbsp;<a id="internet.media.type.http" href="#internet.media.type.http">Internet Media Types</a></h1>
    2359       <p id="rfc.section.A.p.1">In addition to defining HTTP/1.1, this document serves as the specification for the Internet media type "message/http" and
    2360          "application/http". The following is to be registered with IANA <a href="#RFC4288" id="rfc.xref.RFC4288.1"><cite title="Media Type Specifications and Registration Procedures">[RFC4288]</cite></a>.
    2361       </p>
    2362       <div id="rfc.iref.m.2"></div>
    2363       <div id="rfc.iref.m.3"></div>
    2364       <h2 id="rfc.section.A.1"><a href="#rfc.section.A.1">A.1</a>&nbsp;<a id="internet.media.type.message.http" href="#internet.media.type.message.http">Internet Media Type message/http</a></h2>
    2365       <p id="rfc.section.A.1.p.1">The message/http type can be used to enclose a single HTTP request or response message, provided that it obeys the MIME restrictions
    2366          for all "message" types regarding line length and encodings.
    2367       </p>
    2368       <p id="rfc.section.A.1.p.2"> </p>
    2369