Changeset 1032


Ignore:
Timestamp:
Oct 18, 2010, 10:47:51 PM (9 years ago)
Author:
mnot@…
Message:

Expound upon appropriate use and content of User-Agent; addresses #232.

Location:
draft-ietf-httpbis/latest
Files:
2 edited

Legend:

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  • draft-ietf-httpbis/latest/p2-semantics.html

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    346        content: "October 2010";
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    349        content: "HTTP/1.1, Part 2";
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    352        content: "Fielding, et al.";
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    355        content: "Standards Track";
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    373 </style><link rel="Contents" href="#rfc.toc">
    374       <link rel="Author" href="#rfc.authors">
    375       <link rel="Copyright" href="#rfc.copyrightnotice">
    376       <link rel="Index" href="#rfc.index">
    377       <link rel="Chapter" title="1 Introduction" href="#rfc.section.1">
    378       <link rel="Chapter" title="2 Method" href="#rfc.section.2">
    379       <link rel="Chapter" title="3 Request Header Fields" href="#rfc.section.3">
    380       <link rel="Chapter" title="4 Status Code and Reason Phrase" href="#rfc.section.4">
    381       <link rel="Chapter" title="5 Response Header Fields" href="#rfc.section.5">
    382       <link rel="Chapter" title="6 Representation" href="#rfc.section.6">
    383       <link rel="Chapter" title="7 Method Definitions" href="#rfc.section.7">
    384       <link rel="Chapter" title="8 Status Code Definitions" href="#rfc.section.8">
    385       <link rel="Chapter" title="9 Header Field Definitions" href="#rfc.section.9">
    386       <link rel="Chapter" title="10 IANA Considerations" href="#rfc.section.10">
    387       <link rel="Chapter" title="11 Security Considerations" href="#rfc.section.11">
    388       <link rel="Chapter" title="12 Acknowledgments" href="#rfc.section.12">
    389       <link rel="Chapter" href="#rfc.section.13" title="13 References">
    390       <link rel="Appendix" title="A Changes from RFC 2616" href="#rfc.section.A">
    391       <link rel="Appendix" title="B Collected ABNF" href="#rfc.section.B">
    392       <link rel="Appendix" title="C Change Log (to be removed by RFC Editor before publication)" href="#rfc.section.C">
    393       <meta name="generator" content="http://greenbytes.de/tech/webdav/rfc2629.xslt, Revision 1.524, 2010-09-14 12:37:11, XSLT vendor: SAXON 8.9 from Saxonica http://www.saxonica.com/">
    394       <link rel="schema.dct" href="http://purl.org/dc/terms/">
    395       <meta name="dct.creator" content="Fielding, R.">
    396       <meta name="dct.creator" content="Gettys, J.">
    397       <meta name="dct.creator" content="Mogul, J.">
    398       <meta name="dct.creator" content="Frystyk, H.">
    399       <meta name="dct.creator" content="Masinter, L.">
    400       <meta name="dct.creator" content="Leach, P.">
    401       <meta name="dct.creator" content="Berners-Lee, T.">
    402       <meta name="dct.creator" content="Lafon, Y.">
    403       <meta name="dct.creator" content="Reschke, J. F.">
    404       <meta name="dct.identifier" content="urn:ietf:id:draft-ietf-httpbis-p2-semantics-latest">
    405       <meta name="dct.issued" scheme="ISO8601" content="2010-10-11">
    406       <meta name="dct.replaces" content="urn:ietf:rfc:2616">
    407       <meta name="dct.abstract" content="The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypermedia information systems. HTTP has been in use by the World Wide Web global information initiative since 1990. This document is Part 2 of the seven-part specification that defines the protocol referred to as &#34;HTTP/1.1&#34; and, taken together, obsoletes RFC 2616. Part 2 defines the semantics of HTTP messages as expressed by request methods, request-header fields, response status codes, and response-header fields.">
    408       <meta name="description" content="The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypermedia information systems. HTTP has been in use by the World Wide Web global information initiative since 1990. This document is Part 2 of the seven-part specification that defines the protocol referred to as &#34;HTTP/1.1&#34; and, taken together, obsoletes RFC 2616. Part 2 defines the semantics of HTTP messages as expressed by request methods, request-header fields, response status codes, and response-header fields.">
    409    </head>
    410    <body>
    411       <table class="header">
    412          <tbody>
    413             <tr>
    414                <td class="left">HTTPbis Working Group</td>
    415                <td class="right">R. Fielding, Editor</td>
    416             </tr>
    417             <tr>
    418                <td class="left">Internet-Draft</td>
    419                <td class="right">Day Software</td>
    420             </tr>
    421             <tr>
    422                <td class="left">Obsoletes: <a href="http://tools.ietf.org/html/rfc2616">2616</a> (if approved)
    423                </td>
    424                <td class="right">J. Gettys</td>
    425             </tr>
    426             <tr>
    427                <td class="left">Updates: <a href="http://tools.ietf.org/html/rfc2817">2817</a> (if approved)
    428                </td>
    429                <td class="right">Alcatel-Lucent</td>
    430             </tr>
    431             <tr>
    432                <td class="left">Intended status: Standards Track</td>
    433                <td class="right">J. Mogul</td>
    434             </tr>
    435             <tr>
    436                <td class="left">Expires: April 14, 2011</td>
    437                <td class="right">HP</td>
    438             </tr>
    439             <tr>
    440                <td class="left"></td>
    441                <td class="right">H. Frystyk</td>
    442             </tr>
    443             <tr>
    444                <td class="left"></td>
    445                <td class="right">Microsoft</td>
    446             </tr>
    447             <tr>
    448                <td class="left"></td>
    449                <td class="right">L. Masinter</td>
    450             </tr>
    451             <tr>
    452                <td class="left"></td>
    453                <td class="right">Adobe Systems</td>
    454             </tr>
    455             <tr>
    456                <td class="left"></td>
    457                <td class="right">P. Leach</td>
    458             </tr>
    459             <tr>
    460                <td class="left"></td>
    461                <td class="right">Microsoft</td>
    462             </tr>
    463             <tr>
    464                <td class="left"></td>
    465                <td class="right">T. Berners-Lee</td>
    466             </tr>
    467             <tr>
    468                <td class="left"></td>
    469                <td class="right">W3C/MIT</td>
    470             </tr>
    471             <tr>
    472                <td class="left"></td>
    473                <td class="right">Y. Lafon, Editor</td>
    474             </tr>
    475             <tr>
    476                <td class="left"></td>
    477                <td class="right">W3C</td>
    478             </tr>
    479             <tr>
    480                <td class="left"></td>
    481                <td class="right">J. Reschke, Editor</td>
    482             </tr>
    483             <tr>
    484                <td class="left"></td>
    485                <td class="right">greenbytes</td>
    486             </tr>
    487             <tr>
    488                <td class="left"></td>
    489                <td class="right">October 11, 2010</td>
    490             </tr>
    491          </tbody>
    492       </table>
    493       <p class="title">HTTP/1.1, part 2: Message Semantics<br><span class="filename">draft-ietf-httpbis-p2-semantics-latest</span></p>
    494       <h1 id="rfc.abstract"><a href="#rfc.abstract">Abstract</a></h1>
    495       <p>The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypermedia information
    496          systems. HTTP has been in use by the World Wide Web global information initiative since 1990. This document is Part 2 of the
    497          seven-part specification that defines the protocol referred to as "HTTP/1.1" and, taken together, obsoletes RFC 2616. Part
    498          2 defines the semantics of HTTP messages as expressed by request methods, request-header fields, response status codes, and
    499          response-header fields.
    500       </p>
    501       <h1 id="rfc.note.1"><a href="#rfc.note.1">Editorial Note (To be removed by RFC Editor)</a></h1>
    502       <p>Discussion of this draft should take place on the HTTPBIS working group mailing list (ietf-http-wg@w3.org). The current issues
    503          list is at &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/report/3">http://tools.ietf.org/wg/httpbis/trac/report/3</a>&gt; and related documents (including fancy diffs) can be found at &lt;<a href="http://tools.ietf.org/wg/httpbis/">http://tools.ietf.org/wg/httpbis/</a>&gt;.
    504       </p> 
    505       <p>The changes in this draft are summarized in <a href="#changes.since.11" title="Since draft-ietf-httpbis-p2-semantics-11">Appendix&nbsp;C.13</a>.
    506       </p>
    507       <h1><a id="rfc.status" href="#rfc.status">Status of This Memo</a></h1>
    508       <p>This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.</p>
    509       <p>Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute
    510          working documents as Internet-Drafts. The list of current Internet-Drafts is at <a href="http://datatracker.ietf.org/drafts/current/">http://datatracker.ietf.org/drafts/current/</a>.
    511       </p>
    512       <p>Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other
    513          documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as “work
    514          in progress”.
    515       </p>
    516       <p>This Internet-Draft will expire on April 14, 2011.</p>
    517       <h1><a id="rfc.copyrightnotice" href="#rfc.copyrightnotice">Copyright Notice</a></h1>
    518       <p>Copyright © 2010 IETF Trust and the persons identified as the document authors. All rights reserved.</p>
    519       <p>This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (<a href="http://trustee.ietf.org/license-info">http://trustee.ietf.org/license-info</a>) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights
    520          and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License
    521          text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified
    522          BSD License.
    523       </p>
    524       <p>This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November
    525          10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to
    526          allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s)
    527          controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative
    528          works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate
    529          it into languages other than English.
    530       </p>
    531       <hr class="noprint">
    532       <h1 class="np" id="rfc.toc"><a href="#rfc.toc">Table of Contents</a></h1>
    533       <ul class="toc">
    534          <li class="tocline0">1.&nbsp;&nbsp;&nbsp;<a href="#introduction">Introduction</a><ul class="toc">
    535                <li class="tocline1">1.1&nbsp;&nbsp;&nbsp;<a href="#intro.requirements">Requirements</a></li>
    536                <li class="tocline1">1.2&nbsp;&nbsp;&nbsp;<a href="#notation">Syntax Notation</a><ul class="toc">
    537                      <li class="tocline1">1.2.1&nbsp;&nbsp;&nbsp;<a href="#core.rules">Core Rules</a></li>
    538                      <li class="tocline1">1.2.2&nbsp;&nbsp;&nbsp;<a href="#abnf.dependencies">ABNF Rules defined in other Parts of the Specification</a></li>
    539                   </ul>
    540                </li>
    541             </ul>
    542          </li>
    543          <li class="tocline0">2.&nbsp;&nbsp;&nbsp;<a href="#method">Method</a><ul class="toc">
    544                <li class="tocline1">2.1&nbsp;&nbsp;&nbsp;<a href="#method.registry">Method Registry</a></li>
    545             </ul>
    546          </li>
    547          <li class="tocline0">3.&nbsp;&nbsp;&nbsp;<a href="#request.header.fields">Request Header Fields</a></li>
    548          <li class="tocline0">4.&nbsp;&nbsp;&nbsp;<a href="#status.code.and.reason.phrase">Status Code and Reason Phrase</a><ul class="toc">
    549                <li class="tocline1">4.1&nbsp;&nbsp;&nbsp;<a href="#status.code.registry">Status Code Registry</a></li>
    550             </ul>
    551          </li>
    552          <li class="tocline0">5.&nbsp;&nbsp;&nbsp;<a href="#response.header.fields">Response Header Fields</a></li>
    553          <li class="tocline0">6.&nbsp;&nbsp;&nbsp;<a href="#representation">Representation</a><ul class="toc">
    554                <li class="tocline1">6.1&nbsp;&nbsp;&nbsp;<a href="#identifying.response.associated.with.representation">Identifying the Resource Associated with a Representation</a></li>
    555             </ul>
    556          </li>
    557          <li class="tocline0">7.&nbsp;&nbsp;&nbsp;<a href="#method.definitions">Method Definitions</a><ul class="toc">
    558                <li class="tocline1">7.1&nbsp;&nbsp;&nbsp;<a href="#safe.and.idempotent">Safe and Idempotent Methods</a><ul class="toc">
    559                      <li class="tocline1">7.1.1&nbsp;&nbsp;&nbsp;<a href="#safe.methods">Safe Methods</a></li>
    560                      <li class="tocline1">7.1.2&nbsp;&nbsp;&nbsp;<a href="#idempotent.methods">Idempotent Methods</a></li>
    561                   </ul>
    562                </li>
    563                <li class="tocline1">7.2&nbsp;&nbsp;&nbsp;<a href="#OPTIONS">OPTIONS</a></li>
    564                <li class="tocline1">7.3&nbsp;&nbsp;&nbsp;<a href="#GET">GET</a></li>
    565                <li class="tocline1">7.4&nbsp;&nbsp;&nbsp;<a href="#HEAD">HEAD</a></li>
    566                <li class="tocline1">7.5&nbsp;&nbsp;&nbsp;<a href="#POST">POST</a></li>
    567                <li class="tocline1">7.6&nbsp;&nbsp;&nbsp;<a href="#PUT">PUT</a></li>
    568                <li class="tocline1">7.7&nbsp;&nbsp;&nbsp;<a href="#DELETE">DELETE</a></li>
    569                <li class="tocline1">7.8&nbsp;&nbsp;&nbsp;<a href="#TRACE">TRACE</a></li>
    570                <li class="tocline1">7.9&nbsp;&nbsp;&nbsp;<a href="#CONNECT">CONNECT</a></li>
    571             </ul>
    572          </li>
    573          <li class="tocline0">8.&nbsp;&nbsp;&nbsp;<a href="#status.codes">Status Code Definitions</a><ul class="toc">
    574                <li class="tocline1">8.1&nbsp;&nbsp;&nbsp;<a href="#status.1xx">Informational 1xx</a><ul class="toc">
    575                      <li class="tocline1">8.1.1&nbsp;&nbsp;&nbsp;<a href="#status.100">100 Continue</a></li>
    576                      <li class="tocline1">8.1.2&nbsp;&nbsp;&nbsp;<a href="#status.101">101 Switching Protocols</a></li>
    577                   </ul>
    578                </li>
    579                <li class="tocline1">8.2&nbsp;&nbsp;&nbsp;<a href="#status.2xx">Successful 2xx</a><ul class="toc">
    580                      <li class="tocline1">8.2.1&nbsp;&nbsp;&nbsp;<a href="#status.200">200 OK</a></li>
    581                      <li class="tocline1">8.2.2&nbsp;&nbsp;&nbsp;<a href="#status.201">201 Created</a></li>
    582                      <li class="tocline1">8.2.3&nbsp;&nbsp;&nbsp;<a href="#status.202">202 Accepted</a></li>
    583                      <li class="tocline1">8.2.4&nbsp;&nbsp;&nbsp;<a href="#status.203">203 Non-Authoritative Information</a></li>
    584                      <li class="tocline1">8.2.5&nbsp;&nbsp;&nbsp;<a href="#status.204">204 No Content</a></li>
    585                      <li class="tocline1">8.2.6&nbsp;&nbsp;&nbsp;<a href="#status.205">205 Reset Content</a></li>
    586                      <li class="tocline1">8.2.7&nbsp;&nbsp;&nbsp;<a href="#status.206">206 Partial Content</a></li>
    587                   </ul>
    588                </li>
    589                <li class="tocline1">8.3&nbsp;&nbsp;&nbsp;<a href="#status.3xx">Redirection 3xx</a><ul class="toc">
    590                      <li class="tocline1">8.3.1&nbsp;&nbsp;&nbsp;<a href="#status.300">300 Multiple Choices</a></li>
    591                      <li class="tocline1">8.3.2&nbsp;&nbsp;&nbsp;<a href="#status.301">301 Moved Permanently</a></li>
    592                      <li class="tocline1">8.3.3&nbsp;&nbsp;&nbsp;<a href="#status.302">302 Found</a></li>
    593                      <li class="tocline1">8.3.4&nbsp;&nbsp;&nbsp;<a href="#status.303">303 See Other</a></li>
    594                      <li class="tocline1">8.3.5&nbsp;&nbsp;&nbsp;<a href="#status.304">304 Not Modified</a></li>
    595                      <li class="tocline1">8.3.6&nbsp;&nbsp;&nbsp;<a href="#status.305">305 Use Proxy</a></li>
    596                      <li class="tocline1">8.3.7&nbsp;&nbsp;&nbsp;<a href="#status.306">306 (Unused)</a></li>
    597                      <li class="tocline1">8.3.8&nbsp;&nbsp;&nbsp;<a href="#status.307">307 Temporary Redirect</a></li>
    598                   </ul>
    599                </li>
    600                <li class="tocline1">8.4&nbsp;&nbsp;&nbsp;<a href="#status.4xx">Client Error 4xx</a><ul class="toc">
    601                      <li class="tocline1">8.4.1&nbsp;&nbsp;&nbsp;<a href="#status.400">400 Bad Request</a></li>
    602                      <li class="tocline1">8.4.2&nbsp;&nbsp;&nbsp;<a href="#status.401">401 Unauthorized</a></li>
    603                      <li class="tocline1">8.4.3&nbsp;&nbsp;&nbsp;<a href="#status.402">402 Payment Required</a></li>
    604                      <li class="tocline1">8.4.4&nbsp;&nbsp;&nbsp;<a href="#status.403">403 Forbidden</a></li>
    605                      <li class="tocline1">8.4.5&nbsp;&nbsp;&nbsp;<a href="#status.404">404 Not Found</a></li>
    606                      <li class="tocline1">8.4.6&nbsp;&nbsp;&nbsp;<a href="#status.405">405 Method Not Allowed</a></li>
    607                      <li class="tocline1">8.4.7&nbsp;&nbsp;&nbsp;<a href="#status.406">406 Not Acceptable</a></li>
    608                      <li class="tocline1">8.4.8&nbsp;&nbsp;&nbsp;<a href="#status.407">407 Proxy Authentication Required</a></li>
    609                      <li class="tocline1">8.4.9&nbsp;&nbsp;&nbsp;<a href="#status.408">408 Request Timeout</a></li>
    610                      <li class="tocline1">8.4.10&nbsp;&nbsp;&nbsp;<a href="#status.409">409 Conflict</a></li>
    611                      <li class="tocline1">8.4.11&nbsp;&nbsp;&nbsp;<a href="#status.410">410 Gone</a></li>
    612                      <li class="tocline1">8.4.12&nbsp;&nbsp;&nbsp;<a href="#status.411">411 Length Required</a></li>
    613                      <li class="tocline1">8.4.13&nbsp;&nbsp;&nbsp;<a href="#status.412">412 Precondition Failed</a></li>
    614                      <li class="tocline1">8.4.14&nbsp;&nbsp;&nbsp;<a href="#status.413">413 Request Entity Too Large</a></li>
    615                      <li class="tocline1">8.4.15&nbsp;&nbsp;&nbsp;<a href="#status.414">414 URI Too Long</a></li>
    616                      <li class="tocline1">8.4.16&nbsp;&nbsp;&nbsp;<a href="#status.415">415 Unsupported Media Type</a></li>
    617                      <li class="tocline1">8.4.17&nbsp;&nbsp;&nbsp;<a href="#status.416">416 Requested Range Not Satisfiable</a></li>
    618                      <li class="tocline1">8.4.18&nbsp;&nbsp;&nbsp;<a href="#status.417">417 Expectation Failed</a></li>
    619                   </ul>
    620                </li>
    621                <li class="tocline1">8.5&nbsp;&nbsp;&nbsp;<a href="#status.5xx">Server Error 5xx</a><ul class="toc">
    622                      <li class="tocline1">8.5.1&nbsp;&nbsp;&nbsp;<a href="#status.500">500 Internal Server Error</a></li>
    623                      <li class="tocline1">8.5.2&nbsp;&nbsp;&nbsp;<a href="#status.501">501 Not Implemented</a></li>
    624                      <li class="tocline1">8.5.3&nbsp;&nbsp;&nbsp;<a href="#status.502">502 Bad Gateway</a></li>
    625                      <li class="tocline1">8.5.4&nbsp;&nbsp;&nbsp;<a href="#status.503">503 Service Unavailable</a></li>
    626                      <li class="tocline1">8.5.5&nbsp;&nbsp;&nbsp;<a href="#status.504">504 Gateway Timeout</a></li>
    627                      <li class="tocline1">8.5.6&nbsp;&nbsp;&nbsp;<a href="#status.505">505 HTTP Version Not Supported</a></li>
    628                   </ul>
    629                </li>
    630             </ul>
    631          </li>
    632          <li class="tocline0">9.&nbsp;&nbsp;&nbsp;<a href="#header.fields">Header Field Definitions</a><ul class="toc">
    633                <li class="tocline1">9.1&nbsp;&nbsp;&nbsp;<a href="#header.allow">Allow</a></li>
    634                <li class="tocline1">9.2&nbsp;&nbsp;&nbsp;<a href="#header.expect">Expect</a></li>
    635                <li class="tocline1">9.3&nbsp;&nbsp;&nbsp;<a href="#header.from">From</a></li>
    636                <li class="tocline1">9.4&nbsp;&nbsp;&nbsp;<a href="#header.location">Location</a></li>
    637                <li class="tocline1">9.5&nbsp;&nbsp;&nbsp;<a href="#header.max-forwards">Max-Forwards</a></li>
    638                <li class="tocline1">9.6&nbsp;&nbsp;&nbsp;<a href="#header.referer">Referer</a></li>
    639                <li class="tocline1">9.7&nbsp;&nbsp;&nbsp;<a href="#header.retry-after">Retry-After</a></li>
    640                <li class="tocline1">9.8&nbsp;&nbsp;&nbsp;<a href="#header.server">Server</a></li>
    641                <li class="tocline1">9.9&nbsp;&nbsp;&nbsp;<a href="#header.user-agent">User-Agent</a></li>
    642             </ul>
    643          </li>
    644          <li class="tocline0">10.&nbsp;&nbsp;&nbsp;<a href="#IANA.considerations">IANA Considerations</a><ul class="toc">
    645                <li class="tocline1">10.1&nbsp;&nbsp;&nbsp;<a href="#method.registration">Method Registry</a></li>
    646                <li class="tocline1">10.2&nbsp;&nbsp;&nbsp;<a href="#status.code.registration">Status Code Registry</a></li>
    647                <li class="tocline1">10.3&nbsp;&nbsp;&nbsp;<a href="#header.field.registration">Header Field Registration</a></li>
    648             </ul>
    649          </li>
    650          <li class="tocline0">11.&nbsp;&nbsp;&nbsp;<a href="#security.considerations">Security Considerations</a><ul class="toc">
    651                <li class="tocline1">11.1&nbsp;&nbsp;&nbsp;<a href="#security.sensitive">Transfer of Sensitive Information</a></li>
    652                <li class="tocline1">11.2&nbsp;&nbsp;&nbsp;<a href="#encoding.sensitive.information.in.uris">Encoding Sensitive Information in URIs</a></li>
    653                <li class="tocline1">11.3&nbsp;&nbsp;&nbsp;<a href="#location.spoofing">Location Headers and Spoofing</a></li>
    654             </ul>
    655          </li>
    656          <li class="tocline0">12.&nbsp;&nbsp;&nbsp;<a href="#ack">Acknowledgments</a></li>
    657          <li class="tocline0">13.&nbsp;&nbsp;&nbsp;<a href="#rfc.references">References</a><ul class="toc">
    658                <li class="tocline1">13.1&nbsp;&nbsp;&nbsp;<a href="#rfc.references.1">Normative References</a></li>
    659                <li class="tocline1">13.2&nbsp;&nbsp;&nbsp;<a href="#rfc.references.2">Informative References</a></li>
    660             </ul>
    661          </li>
    662          <li class="tocline0"><a href="#rfc.authors">Authors' Addresses</a></li>
    663          <li class="tocline0">A.&nbsp;&nbsp;&nbsp;<a href="#changes.from.rfc.2616">Changes from RFC 2616</a></li>
    664          <li class="tocline0">B.&nbsp;&nbsp;&nbsp;<a href="#collected.abnf">Collected ABNF</a></li>
    665          <li class="tocline0">C.&nbsp;&nbsp;&nbsp;<a href="#change.log">Change Log (to be removed by RFC Editor before publication)</a><ul class="toc">
    666                <li class="tocline1">C.1&nbsp;&nbsp;&nbsp;<a href="#rfc.section.C.1">Since RFC 2616</a></li>
    667                <li class="tocline1">C.2&nbsp;&nbsp;&nbsp;<a href="#rfc.section.C.2">Since draft-ietf-httpbis-p2-semantics-00</a></li>
    668                <li class="tocline1">C.3&nbsp;&nbsp;&nbsp;<a href="#rfc.section.C.3">Since draft-ietf-httpbis-p2-semantics-01</a></li>
    669                <li class="tocline1">C.4&nbsp;&nbsp;&nbsp;<a href="#changes.since.02">Since draft-ietf-httpbis-p2-semantics-02</a></li>
    670                <li class="tocline1">C.5&nbsp;&nbsp;&nbsp;<a href="#changes.since.03">Since draft-ietf-httpbis-p2-semantics-03</a></li>
    671                <li class="tocline1">C.6&nbsp;&nbsp;&nbsp;<a href="#changes.since.04">Since draft-ietf-httpbis-p2-semantics-04</a></li>
    672                <li class="tocline1">C.7&nbsp;&nbsp;&nbsp;<a href="#changes.since.05">Since draft-ietf-httpbis-p2-semantics-05</a></li>
    673                <li class="tocline1">C.8&nbsp;&nbsp;&nbsp;<a href="#changes.since.06">Since draft-ietf-httpbis-p2-semantics-06</a></li>
    674                <li class="tocline1">C.9&nbsp;&nbsp;&nbsp;<a href="#changes.since.07">Since draft-ietf-httpbis-p2-semantics-07</a></li>
    675                <li class="tocline1">C.10&nbsp;&nbsp;&nbsp;<a href="#changes.since.08">Since draft-ietf-httpbis-p2-semantics-08</a></li>
    676                <li class="tocline1">C.11&nbsp;&nbsp;&nbsp;<a href="#changes.since.09">Since draft-ietf-httpbis-p2-semantics-09</a></li>
    677                <li class="tocline1">C.12&nbsp;&nbsp;&nbsp;<a href="#changes.since.10">Since draft-ietf-httpbis-p2-semantics-10</a></li>
    678                <li class="tocline1">C.13&nbsp;&nbsp;&nbsp;<a href="#changes.since.11">Since draft-ietf-httpbis-p2-semantics-11</a></li>
    679             </ul>
    680          </li>
    681          <li class="tocline0"><a href="#rfc.index">Index</a></li>
    682       </ul>
    683       <h1 id="rfc.section.1" class="np"><a href="#rfc.section.1">1.</a>&nbsp;<a id="introduction" href="#introduction">Introduction</a></h1>
    684       <p id="rfc.section.1.p.1">This document defines HTTP/1.1 request and response semantics. Each HTTP message, as defined in <a href="#Part1" id="rfc.xref.Part1.1"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, is in the form of either a request or a response. An HTTP server listens on a connection for HTTP requests and responds
    685          to each request, in the order received on that connection, with one or more HTTP response messages. This document defines
    686          the commonly agreed upon semantics of the HTTP uniform interface, the intentions defined by each request method, and the various
    687          response messages that might be expected as a result of applying that method to the target resource.
    688       </p>
    689       <p id="rfc.section.1.p.2">This document is currently disorganized in order to minimize the changes between drafts and enable reviewers to see the smaller
    690          errata changes. A future draft will reorganize the sections to better reflect the content. In particular, the sections will
    691          be ordered according to the typical processing of an HTTP request message (after message parsing): resource mapping, general
    692          header fields, methods, request modifiers, response status, and resource metadata. The current mess reflects how widely dispersed
    693          these topics and associated requirements had become in <a href="#RFC2616" id="rfc.xref.RFC2616.1"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>.
    694       </p>
    695       <h2 id="rfc.section.1.1"><a href="#rfc.section.1.1">1.1</a>&nbsp;<a id="intro.requirements" href="#intro.requirements">Requirements</a></h2>
    696       <p id="rfc.section.1.1.p.1">The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"
    697          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>.
    698       </p>
    699       <p id="rfc.section.1.1.p.2">An implementation is not compliant if it fails to satisfy one or more of the "MUST" or "REQUIRED" level requirements for the
    700          protocols it implements. An implementation that satisfies all the "MUST" or "REQUIRED" level and all the "SHOULD" level requirements
    701          for its protocols is said to be "unconditionally compliant"; one that satisfies all the "MUST" level requirements but not
    702          all the "SHOULD" level requirements for its protocols is said to be "conditionally compliant".
    703       </p>
    704       <h2 id="rfc.section.1.2"><a href="#rfc.section.1.2">1.2</a>&nbsp;<a id="notation" href="#notation">Syntax Notation</a></h2>
    705       <p id="rfc.section.1.2.p.1">This specification uses the ABNF syntax defined in <a href="p1-messaging.html#notation" title="Syntax Notation">Section 1.2</a> of <a href="#Part1" id="rfc.xref.Part1.2"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a> (which extends the syntax defined in <a href="#RFC5234" id="rfc.xref.RFC5234.1"><cite title="Augmented BNF for Syntax Specifications: ABNF">[RFC5234]</cite></a> with a list rule). <a href="#collected.abnf" title="Collected ABNF">Appendix&nbsp;B</a> shows the collected ABNF, with the list rule expanded.
    706       </p>
    707       <p id="rfc.section.1.2.p.2">The following core rules are included by reference, as defined in <a href="#RFC5234" id="rfc.xref.RFC5234.2"><cite title="Augmented BNF for Syntax Specifications: ABNF">[RFC5234]</cite></a>, <a href="http://tools.ietf.org/html/rfc5234#appendix-B.1">Appendix B.1</a>: ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double quote), HEXDIG
    708          (hexadecimal 0-9/A-F/a-f), LF (line feed), OCTET (any 8-bit sequence of data), SP (space), VCHAR (any visible USASCII character),
    709          and WSP (whitespace).
    710       </p>
    711       <h3 id="rfc.section.1.2.1"><a href="#rfc.section.1.2.1">1.2.1</a>&nbsp;<a id="core.rules" href="#core.rules">Core Rules</a></h3>
    712       <p id="rfc.section.1.2.1.p.1">The core rules below are defined in <a href="p1-messaging.html#basic.rules" title="Basic Rules">Section 1.2.2</a> of <a href="#Part1" id="rfc.xref.Part1.3"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>:
    713       </p>
    714       <div id="rfc.figure.u.1"></div><pre class="inline">  <a href="#core.rules" class="smpl">quoted-string</a> = &lt;quoted-string, defined in <a href="#Part1" id="rfc.xref.Part1.4"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#basic.rules" title="Basic Rules">Section 1.2.2</a>&gt;
    715   <a href="#core.rules" class="smpl">token</a>         = &lt;token, defined in <a href="#Part1" id="rfc.xref.Part1.5"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#basic.rules" title="Basic Rules">Section 1.2.2</a>&gt;
    716   <a href="#core.rules" class="smpl">OWS</a>           = &lt;OWS, defined in <a href="#Part1" id="rfc.xref.Part1.6"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#basic.rules" title="Basic Rules">Section 1.2.2</a>&gt;
    717   <a href="#core.rules" class="smpl">RWS</a>           = &lt;RWS, defined in <a href="#Part1" id="rfc.xref.Part1.7"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#basic.rules" title="Basic Rules">Section 1.2.2</a>&gt;
    718   <a href="#core.rules" class="smpl">obs-text</a>      = &lt;obs-text, defined in <a href="#Part1" id="rfc.xref.Part1.8"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#basic.rules" title="Basic Rules">Section 1.2.2</a>&gt;
    719 </pre><h3 id="rfc.section.1.2.2"><a href="#rfc.section.1.2.2">1.2.2</a>&nbsp;<a id="abnf.dependencies" href="#abnf.dependencies">ABNF Rules defined in other Parts of the Specification</a></h3>
    720       <p id="rfc.section.1.2.2.p.1">The ABNF rules below are defined in other parts:</p>
    721       <div id="rfc.figure.u.2"></div><pre class="inline">  <a href="#abnf.dependencies" class="smpl">absolute-URI</a>  = &lt;absolute-URI, defined in <a href="#Part1" id="rfc.xref.Part1.9"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#uri" title="Uniform Resource Identifiers">Section 2.6</a>&gt;
    722   <a href="#abnf.dependencies" class="smpl">comment</a>       = &lt;comment, defined in <a href="#Part1" id="rfc.xref.Part1.10"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#header.fields" title="Header Fields">Section 3.2</a>&gt;
    723   <a href="#abnf.dependencies" class="smpl">Host</a>          = &lt;Host, defined in <a href="#Part1" id="rfc.xref.Part1.11"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#uri" title="Uniform Resource Identifiers">Section 2.6</a>&gt;
    724   <a href="#abnf.dependencies" class="smpl">HTTP-date</a>     = &lt;HTTP-date, defined in <a href="#Part1" id="rfc.xref.Part1.12"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#date.time.formats.full.date" title="Date/Time Formats: Full Date">Section 6.1</a>&gt;
    725   <a href="#abnf.dependencies" class="smpl">partial-URI</a>   = &lt;partial-URI, defined in <a href="#Part1" id="rfc.xref.Part1.13"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#uri" title="Uniform Resource Identifiers">Section 2.6</a>&gt;
    726   <a href="#abnf.dependencies" class="smpl">product</a>       = &lt;product, defined in <a href="#Part1" id="rfc.xref.Part1.14"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#product.tokens" title="Product Tokens">Section 6.3</a>&gt;
    727   <a href="#abnf.dependencies" class="smpl">TE</a>            = &lt;TE, defined in <a href="#Part1" id="rfc.xref.Part1.15"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#header.te" title="TE">Section 9.5</a>&gt;
    728   <a href="#abnf.dependencies" class="smpl">URI-reference</a> = &lt;URI-reference, defined in <a href="#Part1" id="rfc.xref.Part1.16"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#uri" title="Uniform Resource Identifiers">Section 2.6</a>&gt;
    729 </pre><div id="rfc.figure.u.3"></div><pre class="inline">  <a href="#abnf.dependencies" class="smpl">Accept</a>        = &lt;Accept, defined in <a href="#Part3" id="rfc.xref.Part3.1"><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;
    730   <a href="#abnf.dependencies" class="smpl">Accept-Charset</a> =
    731              &lt;Accept-Charset, defined in <a href="#Part3" id="rfc.xref.Part3.2"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>, <a href="p3-payload.html#header.accept-charset" title="Accept-Charset">Section 6.2</a>&gt;
    732   <a href="#abnf.dependencies" class="smpl">Accept-Encoding</a> =
    733              &lt;Accept-Encoding, defined in <a href="#Part3" id="rfc.xref.Part3.3"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>, <a href="p3-payload.html#header.accept-encoding" title="Accept-Encoding">Section 6.3</a>&gt;
    734   <a href="#abnf.dependencies" class="smpl">Accept-Language</a> =
    735              &lt;Accept-Language, defined in <a href="#Part3" id="rfc.xref.Part3.4"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>, <a href="p3-payload.html#header.accept-language" title="Accept-Language">Section 6.4</a>&gt;
    736 </pre><div id="rfc.figure.u.4"></div><pre class="inline">  <a href="#abnf.dependencies" class="smpl">ETag</a>          = &lt;ETag, defined in <a href="#Part4" id="rfc.xref.Part4.1"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>, <a href="p4-conditional.html#header.etag" title="ETag">Section 6.1</a>&gt;
    737   <a href="#abnf.dependencies" class="smpl">If-Match</a>      = &lt;If-Match, defined in <a href="#Part4" id="rfc.xref.Part4.2"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>, <a href="p4-conditional.html#header.if-match" title="If-Match">Section 6.2</a>&gt;
    738   <a href="#abnf.dependencies" class="smpl">If-Modified-Since</a> =
    739              &lt;If-Modified-Since, defined in <a href="#Part4" id="rfc.xref.Part4.3"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>, <a href="p4-conditional.html#header.if-modified-since" title="If-Modified-Since">Section 6.3</a>&gt;
    740   <a href="#abnf.dependencies" class="smpl">If-None-Match</a> = &lt;If-None-Match, defined in <a href="#Part4" id="rfc.xref.Part4.4"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>, <a href="p4-conditional.html#header.if-none-match" title="If-None-Match">Section 6.4</a>&gt;
    741   <a href="#abnf.dependencies" class="smpl">If-Unmodified-Since</a> =
    742              &lt;If-Unmodified-Since, defined in <a href="#Part4" id="rfc.xref.Part4.5"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>, <a href="p4-conditional.html#header.if-unmodified-since" title="If-Unmodified-Since">Section 6.5</a>&gt;
    743 </pre><div id="rfc.figure.u.5"></div><pre class="inline">  <a href="#abnf.dependencies" class="smpl">Accept-Ranges</a> = &lt;Accept-Ranges, defined in <a href="#Part5" id="rfc.xref.Part5.1"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>, <a href="p5-range.html#header.accept-ranges" title="Accept-Ranges">Section 5.1</a>&gt;
    744   <a href="#abnf.dependencies" class="smpl">If-Range</a>      = &lt;If-Range, defined in <a href="#Part5" id="rfc.xref.Part5.2"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>, <a href="p5-range.html#header.if-range" title="If-Range">Section 5.3</a>&gt;
    745   <a href="#abnf.dependencies" class="smpl">Range</a>         = &lt;Range, defined in <a href="#Part5" id="rfc.xref.Part5.3"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>, <a href="p5-range.html#header.range" title="Range">Section 5.4</a>&gt;
    746 </pre><div id="rfc.figure.u.6"></div><pre class="inline">  <a href="#abnf.dependencies" class="smpl">Age</a>           = &lt;Age, defined in <a href="#Part6" id="rfc.xref.Part6.1"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>, <a href="p6-cache.html#header.age" title="Age">Section 3.1</a>&gt;
    747   <a href="#abnf.dependencies" class="smpl">Vary</a>          = &lt;Vary, defined in <a href="#Part6" id="rfc.xref.Part6.2"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>, <a href="p6-cache.html#header.vary" title="Vary">Section 3.5</a>&gt;
    748 </pre><div id="rfc.figure.u.7"></div><pre class="inline">  <a href="#abnf.dependencies" class="smpl">Authorization</a> = &lt;Authorization, defined in <a href="#Part7" id="rfc.xref.Part7.1"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a>, <a href="p7-auth.html#header.authorization" title="Authorization">Section 4.1</a>&gt;
    749   <a href="#abnf.dependencies" class="smpl">Proxy-Authenticate</a> =
    750              &lt;Proxy-Authenticate, defined in <a href="#Part7" id="rfc.xref.Part7.2"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a>, <a href="p7-auth.html#header.proxy-authenticate" title="Proxy-Authenticate">Section 4.2</a>&gt;
    751   <a href="#abnf.dependencies" class="smpl">Proxy-Authorization</a> =
    752              &lt;Proxy-Authorization, defined in <a href="#Part7" id="rfc.xref.Part7.3"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a>, <a href="p7-auth.html#header.proxy-authorization" title="Proxy-Authorization">Section 4.3</a>&gt;
    753   <a href="#abnf.dependencies" class="smpl">WWW-Authenticate</a> =
    754              &lt;WWW-Authenticate, defined in <a href="#Part7" id="rfc.xref.Part7.4"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a>, <a href="p7-auth.html#header.www-authenticate" title="WWW-Authenticate">Section 4.4</a>&gt;
    755 </pre><h1 id="rfc.section.2"><a href="#rfc.section.2">2.</a>&nbsp;<a id="method" href="#method">Method</a></h1>
    756       <p id="rfc.section.2.p.1">The Method token indicates the method to be performed on the target resource (<a href="p1-messaging.html#effective.request.uri" title="Effective Request URI">Section 4.3</a> of <a href="#Part1" id="rfc.xref.Part1.17"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>). The method is case-sensitive.
    757       </p>
    758       <div id="rfc.figure.u.8"></div><pre class="inline"><span id="rfc.iref.g.1"></span><span id="rfc.iref.g.2"></span>  <a href="#method" class="smpl">Method</a>         = %x4F.50.54.49.4F.4E.53   ; "OPTIONS", <a href="#OPTIONS" id="rfc.xref.OPTIONS.1" title="OPTIONS">Section&nbsp;7.2</a>
    759                  / %x47.45.54               ; "GET", <a href="#GET" id="rfc.xref.GET.1" title="GET">Section&nbsp;7.3</a>
    760                  / %x48.45.41.44            ; "HEAD", <a href="#HEAD" id="rfc.xref.HEAD.1" title="HEAD">Section&nbsp;7.4</a>
    761                  / %x50.4F.53.54            ; "POST", <a href="#POST" id="rfc.xref.POST.1" title="POST">Section&nbsp;7.5</a>
    762                  / %x50.55.54               ; "PUT", <a href="#PUT" id="rfc.xref.PUT.1" title="PUT">Section&nbsp;7.6</a>
    763                  / %x44.45.4C.45.54.45      ; "DELETE", <a href="#DELETE" id="rfc.xref.DELETE.1" title="DELETE">Section&nbsp;7.7</a>
    764                  / %x54.52.41.43.45         ; "TRACE", <a href="#TRACE" id="rfc.xref.TRACE.1" title="TRACE">Section&nbsp;7.8</a>
    765                  / %x43.4F.4E.4E.45.43.54   ; "CONNECT", <a href="#CONNECT" id="rfc.xref.CONNECT.1" title="CONNECT">Section&nbsp;7.9</a>
    766                  / <a href="#method" class="smpl">extension-method</a>
    767   <a href="#method" class="smpl">extension-method</a> = <a href="#core.rules" class="smpl">token</a>
    768 </pre><p id="rfc.section.2.p.3">The list of methods allowed by a resource can be specified in an Allow header field (<a href="#header.allow" id="rfc.xref.header.allow.1" title="Allow">Section&nbsp;9.1</a>). The status code of the response always notifies the client whether a method is currently allowed on a resource, since the
    769          set of allowed methods can change dynamically. An origin server <em class="bcp14">SHOULD</em> respond with the status code 405 (Method Not Allowed) if the method is known by the origin server but not allowed for the
    770          resource, and 501 (Not Implemented) if the method is unrecognized or not implemented by the origin server. The methods GET
    771          and HEAD <em class="bcp14">MUST</em> be supported by all general-purpose servers. All other methods are <em class="bcp14">OPTIONAL</em>; however, if the above methods are implemented, they <em class="bcp14">MUST</em> be implemented with the same semantics as those specified in <a href="#method.definitions" title="Method Definitions">Section&nbsp;7</a>.
    772       </p>
    773       <h2 id="rfc.section.2.1"><a href="#rfc.section.2.1">2.1</a>&nbsp;<a id="method.registry" href="#method.registry">Method Registry</a></h2>
    774       <p id="rfc.section.2.1.p.1">The HTTP Method Registry defines the name space for the Method token in the Request line of an HTTP request.</p>
    775       <p id="rfc.section.2.1.p.2">Registrations <em class="bcp14">MUST</em> include the following fields:
    776       </p>
    777       <ul>
    778          <li>Method Name (see <a href="#method" title="Method">Section&nbsp;2</a>)
    779          </li>
    780          <li>Safe ("yes" or "no", see <a href="#safe.methods" title="Safe Methods">Section&nbsp;7.1.1</a>)
    781          </li>
    782          <li>Pointer to specification text</li>
    783       </ul>
    784       <p id="rfc.section.2.1.p.3">Values to be added to this name space are subject to IETF review (<a href="#RFC5226" id="rfc.xref.RFC5226.1"><cite title="Guidelines for Writing an IANA Considerations Section in RFCs">[RFC5226]</cite></a>, <a href="http://tools.ietf.org/html/rfc5226#section-4.1">Section 4.1</a>).
    785       </p>
    786       <p id="rfc.section.2.1.p.4">The registry itself is maintained at &lt;<a href="http://www.iana.org/assignments/http-methods">http://www.iana.org/assignments/http-methods</a>&gt;.
    787       </p>
    788       <h1 id="rfc.section.3"><a href="#rfc.section.3">3.</a>&nbsp;<a id="request.header.fields" href="#request.header.fields">Request Header Fields</a></h1>
    789       <p id="rfc.section.3.p.1">The request-header fields allow the client to pass additional information about the request, and about the client itself,
    790          to the server. These fields act as request modifiers, with semantics equivalent to the parameters on a programming language
    791          method invocation.
    792       </p>
    793       <div id="rfc.figure.u.9"></div><pre class="inline"><span id="rfc.iref.g.3"></span>  <a href="#request.header.fields" class="smpl">request-header</a> = <a href="#abnf.dependencies" class="smpl">Accept</a>                   ; <a href="#Part3" id="rfc.xref.Part3.5"><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>
    794                  / <a href="#abnf.dependencies" class="smpl">Accept-Charset</a>           ; <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-charset" title="Accept-Charset">Section 6.2</a>
    795                  / <a href="#abnf.dependencies" class="smpl">Accept-Encoding</a>          ; <a href="#Part3" id="rfc.xref.Part3.7"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>, <a href="p3-payload.html#header.accept-encoding" title="Accept-Encoding">Section 6.3</a>
    796                  / <a href="#abnf.dependencies" class="smpl">Accept-Language</a>          ; <a href="#Part3" id="rfc.xref.Part3.8"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>, <a href="p3-payload.html#header.accept-language" title="Accept-Language">Section 6.4</a>
    797                  / <a href="#abnf.dependencies" class="smpl">Authorization</a>            ; <a href="#Part7" id="rfc.xref.Part7.5"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a>, <a href="p7-auth.html#header.authorization" title="Authorization">Section 4.1</a>
    798                  / <a href="#header.expect" class="smpl">Expect</a>                   ; <a href="#header.expect" id="rfc.xref.header.expect.1" title="Expect">Section&nbsp;9.2</a>
    799                  / <a href="#header.from" class="smpl">From</a>                     ; <a href="#header.from" id="rfc.xref.header.from.1" title="From">Section&nbsp;9.3</a>
    800                  / <a href="#abnf.dependencies" class="smpl">Host</a>                     ; <a href="#Part1" id="rfc.xref.Part1.18"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#header.host" title="Host">Section 9.4</a>
    801                  / <a href="#abnf.dependencies" class="smpl">If-Match</a>                 ; <a href="#Part4" id="rfc.xref.Part4.6"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>, <a href="p4-conditional.html#header.if-match" title="If-Match">Section 6.2</a>
    802                  / <a href="#abnf.dependencies" class="smpl">If-Modified-Since</a>        ; <a href="#Part4" id="rfc.xref.Part4.7"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>, <a href="p4-conditional.html#header.if-modified-since" title="If-Modified-Since">Section 6.3</a>
    803                  / <a href="#abnf.dependencies" class="smpl">If-None-Match</a>            ; <a href="#Part4" id="rfc.xref.Part4.8"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>, <a href="p4-conditional.html#header.if-none-match" title="If-None-Match">Section 6.4</a>
    804                  / <a href="#abnf.dependencies" class="smpl">If-Range</a>                 ; <a href="#Part5" id="rfc.xref.Part5.4"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>, <a href="p5-range.html#header.if-range" title="If-Range">Section 5.3</a>
    805                  / <a href="#abnf.dependencies" class="smpl">If-Unmodified-Since</a>      ; <a href="#Part4" id="rfc.xref.Part4.9"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>, <a href="p4-conditional.html#header.if-unmodified-since" title="If-Unmodified-Since">Section 6.5</a>
    806                  / <a href="#header.max-forwards" class="smpl">Max-Forwards</a>             ; <a href="#header.max-forwards" id="rfc.xref.header.max-forwards.1" title="Max-Forwards">Section&nbsp;9.5</a>
    807                  / <a href="#abnf.dependencies" class="smpl">Proxy-Authorization</a>      ; <a href="#Part7" id="rfc.xref.Part7.6"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a>, <a href="p7-auth.html#header.proxy-authorization" title="Proxy-Authorization">Section 4.3</a>
    808                  / <a href="#abnf.dependencies" class="smpl">Range</a>                    ; <a href="#Part5" id="rfc.xref.Part5.5"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>, <a href="p5-range.html#header.range" title="Range">Section 5.4</a>
    809                  / <a href="#header.referer" class="smpl">Referer</a>                  ; <a href="#header.referer" id="rfc.xref.header.referer.1" title="Referer">Section&nbsp;9.6</a>
    810                  / <a href="#abnf.dependencies" class="smpl">TE</a>                       ; <a href="#Part1" id="rfc.xref.Part1.19"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#header.te" title="TE">Section 9.5</a>
    811                  / <a href="#header.user-agent" class="smpl">User-Agent</a>               ; <a href="#header.user-agent" id="rfc.xref.header.user-agent.1" title="User-Agent">Section&nbsp;9.9</a>
    812 </pre><p id="rfc.section.3.p.3">Request-header field names can be extended reliably only in combination with a change in the protocol version. However, new
    813          or experimental header fields <em class="bcp14">MAY</em> be given the semantics of request-header fields if all parties in the communication recognize them to be request-header fields.
    814       </p>
    815       <h1 id="rfc.section.4"><a href="#rfc.section.4">4.</a>&nbsp;<a id="status.code.and.reason.phrase" href="#status.code.and.reason.phrase">Status Code and Reason Phrase</a></h1>
    816       <p id="rfc.section.4.p.1">The Status-Code element is a 3-digit integer result code of the attempt to understand and satisfy the request. The status
    817          codes listed below are defined in <a href="#status.codes" title="Status Code Definitions">Section&nbsp;8</a>, <a href="p4-conditional.html#status.code.definitions" title="Status Code Definitions">Section 3</a> of <a href="#Part4" id="rfc.xref.Part4.10"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>, <a href="p5-range.html#status.code.definitions" title="Status Code Definitions">Section 3</a> of <a href="#Part5" id="rfc.xref.Part5.6"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>, and <a href="p7-auth.html#status.code.definitions" title="Status Code Definitions">Section 3</a> of <a href="#Part7" id="rfc.xref.Part7.7"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a>.
    818       </p>
    819       <p id="rfc.section.4.p.2">The Reason-Phrase is intended to give a short textual description of the Status-Code. The Status-Code is intended for use
    820          by automata and the Reason-Phrase is intended for the human user. The client is not required to examine or display the Reason-Phrase.
    821       </p>
    822       <p id="rfc.section.4.p.3">The individual values of the numeric status codes defined for HTTP/1.1, and an example set of corresponding Reason-Phrase
    823          values, are presented below. The reason phrases listed here are only recommendations -- they <em class="bcp14">MAY</em> be replaced by local equivalents without affecting the protocol.
    824       </p>
    825       <div id="rfc.figure.u.10"></div><pre class="inline"><span id="rfc.iref.g.4"></span><span id="rfc.iref.g.5"></span><span id="rfc.iref.g.6"></span>  <a href="#status.code.and.reason.phrase" class="smpl">Status-Code</a> =
    826        "100"  ; <a href="#status.100" id="rfc.xref.status.100.1" title="100 Continue">Section&nbsp;8.1.1</a>: Continue
    827      / "101"  ; <a href="#status.101" id="rfc.xref.status.101.1" title="101 Switching Protocols">Section&nbsp;8.1.2</a>: Switching Protocols
    828      / "200"  ; <a href="#status.200" id="rfc.xref.status.200.1" title="200 OK">Section&nbsp;8.2.1</a>: OK
    829      / "201"  ; <a href="#status.201" id="rfc.xref.status.201.1" title="201 Created">Section&nbsp;8.2.2</a>: Created
    830      / "202"  ; <a href="#status.202" id="rfc.xref.status.202.1" title="202 Accepted">Section&nbsp;8.2.3</a>: Accepted
    831      / "203"  ; <a href="#status.203" id="rfc.xref.status.203.1" title="203 Non-Authoritative Information">Section&nbsp;8.2.4</a>: Non-Authoritative Information
    832      / "204"  ; <a href="#status.204" id="rfc.xref.status.204.1" title="204 No Content">Section&nbsp;8.2.5</a>: No Content
    833      / "205"  ; <a href="#status.205" id="rfc.xref.status.205.1" title="205 Reset Content">Section&nbsp;8.2.6</a>: Reset Content
    834      / "206"  ; <a href="#Part5" id="rfc.xref.Part5.7"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>, <a href="p5-range.html#status.206" title="206 Partial Content">Section 3.1</a>: Partial Content
    835      / "300"  ; <a href="#status.300" id="rfc.xref.status.300.1" title="300 Multiple Choices">Section&nbsp;8.3.1</a>: Multiple Choices
    836      / "301"  ; <a href="#status.301" id="rfc.xref.status.301.1" title="301 Moved Permanently">Section&nbsp;8.3.2</a>: Moved Permanently
    837      / "302"  ; <a href="#status.302" id="rfc.xref.status.302.1" title="302 Found">Section&nbsp;8.3.3</a>: Found
    838      / "303"  ; <a href="#status.303" id="rfc.xref.status.303.1" title="303 See Other">Section&nbsp;8.3.4</a>: See Other
    839      / "304"  ; <a href="#Part4" id="rfc.xref.Part4.11"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>, <a href="p4-conditional.html#status.304" title="304 Not Modified">Section 3.1</a>: Not Modified
    840      / "305"  ; <a href="#status.305" id="rfc.xref.status.305.1" title="305 Use Proxy">Section&nbsp;8.3.6</a>: Use Proxy
    841      / "307"  ; <a href="#status.307" id="rfc.xref.status.307.1" title="307 Temporary Redirect">Section&nbsp;8.3.8</a>: Temporary Redirect
    842      / "400"  ; <a href="#status.400" id="rfc.xref.status.400.1" title="400 Bad Request">Section&nbsp;8.4.1</a>: Bad Request
    843      / "401"  ; <a href="#Part7" id="rfc.xref.Part7.8"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a>, <a href="p7-auth.html#status.401" title="401 Unauthorized">Section 3.1</a>: Unauthorized
    844      / "402"  ; <a href="#status.402" id="rfc.xref.status.402.1" title="402 Payment Required">Section&nbsp;8.4.3</a>: Payment Required
    845      / "403"  ; <a href="#status.403" id="rfc.xref.status.403.1" title="403 Forbidden">Section&nbsp;8.4.4</a>: Forbidden
    846      / "404"  ; <a href="#status.404" id="rfc.xref.status.404.1" title="404 Not Found">Section&nbsp;8.4.5</a>: Not Found
    847      / "405"  ; <a href="#status.405" id="rfc.xref.status.405.1" title="405 Method Not Allowed">Section&nbsp;8.4.6</a>: Method Not Allowed
    848      / "406"  ; <a href="#status.406" id="rfc.xref.status.406.1" title="406 Not Acceptable">Section&nbsp;8.4.7</a>: Not Acceptable
    849      / "407"  ; <a href="#Part7" id="rfc.xref.Part7.9"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a>, <a href="p7-auth.html#status.407" title="407 Proxy Authentication Required">Section 3.2</a>: Proxy Authentication Required
    850      / "408"  ; <a href="#status.408" id="rfc.xref.status.408.1" title="408 Request Timeout">Section&nbsp;8.4.9</a>: Request Time-out
    851      / "409"  ; <a href="#status.409" id="rfc.xref.status.409.1" title="409 Conflict">Section&nbsp;8.4.10</a>: Conflict
    852      / "410"  ; <a href="#status.410" id="rfc.xref.status.410.1" title="410 Gone">Section&nbsp;8.4.11</a>: Gone
    853      / "411"  ; <a href="#status.411" id="rfc.xref.status.411.1" title="411 Length Required">Section&nbsp;8.4.12</a>: Length Required
    854      / "412"  ; <a href="#Part4" id="rfc.xref.Part4.12"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>, <a href="p4-conditional.html#status.412" title="412 Precondition Failed">Section 3.2</a>: Precondition Failed
    855      / "413"  ; <a href="#status.413" id="rfc.xref.status.413.1" title="413 Request Entity Too Large">Section&nbsp;8.4.14</a>: Request Entity Too Large
    856      / "414"  ; <a href="#status.414" id="rfc.xref.status.414.1" title="414 URI Too Long">Section&nbsp;8.4.15</a>: URI Too Long
    857      / "415"  ; <a href="#status.415" id="rfc.xref.status.415.1" title="415 Unsupported Media Type">Section&nbsp;8.4.16</a>: Unsupported Media Type
    858      / "416"  ; <a href="#Part5" id="rfc.xref.Part5.8"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>, <a href="p5-range.html#status.416" title="416 Requested Range Not Satisfiable">Section 3.2</a>: Requested range not satisfiable
    859      / "417"  ; <a href="#status.417" id="rfc.xref.status.417.1" title="417 Expectation Failed">Section&nbsp;8.4.18</a>: Expectation Failed
    860      / "500"  ; <a href="#status.500" id="rfc.xref.status.500.1" title="500 Internal Server Error">Section&nbsp;8.5.1</a>: Internal Server Error
    861      / "501"  ; <a href="#status.501" id="rfc.xref.status.501.1" title="501 Not Implemented">Section&nbsp;8.5.2</a>: Not Implemented
    862      / "502"  ; <a href="#status.502" id="rfc.xref.status.502.1" title="502 Bad Gateway">Section&nbsp;8.5.3</a>: Bad Gateway
    863      / "503"  ; <a href="#status.503" id="rfc.xref.status.503.1" title="503 Service Unavailable">Section&nbsp;8.5.4</a>: Service Unavailable
    864      / "504"  ; <a href="#status.504" id="rfc.xref.status.504.1" title="504 Gateway Timeout">Section&nbsp;8.5.5</a>: Gateway Time-out
    865      / "505"  ; <a href="#status.505" id="rfc.xref.status.505.1" title="505 HTTP Version Not Supported">Section&nbsp;8.5.6</a>: HTTP Version not supported
    866      / <a href="#status.code.and.reason.phrase" class="smpl">extension-code</a>
    867 
    868   <a href="#status.code.and.reason.phrase" class="smpl">extension-code</a> = 3<a href="#notation" class="smpl">DIGIT</a>
    869   <a href="#status.code.and.reason.phrase" class="smpl">Reason-Phrase</a>  = *( <a href="#notation" class="smpl">WSP</a> / <a href="#notation" class="smpl">VCHAR</a> / <a href="#core.rules" class="smpl">obs-text</a> )
    870 </pre><p id="rfc.section.4.p.5">HTTP status codes are extensible. HTTP applications are not required to understand the meaning of all registered status codes,
    871          though such understanding is obviously desirable. However, applications <em class="bcp14">MUST</em> understand the class of any status code, as indicated by the first digit, and treat any unrecognized response as being equivalent
    872          to the x00 status code of that class, with the exception that an unrecognized response <em class="bcp14">MUST NOT</em> be cached. For example, if an unrecognized status code of 431 is received by the client, it can safely assume that there was
    873          something wrong with its request and treat the response as if it had received a 400 status code. In such cases, user agents <em class="bcp14">SHOULD</em> present to the user the representation enclosed with the response, since that representation is likely to include human-readable
    874          information which will explain the unusual status.
    875       </p>
    876       <h2 id="rfc.section.4.1"><a href="#rfc.section.4.1">4.1</a>&nbsp;<a id="status.code.registry" href="#status.code.registry">Status Code Registry</a></h2>
    877       <p id="rfc.section.4.1.p.1">The HTTP Status Code Registry defines the name space for the Status-Code token in the Status-Line of an HTTP response.</p>
    878       <p id="rfc.section.4.1.p.2">Values to be added to this name space are subject to IETF review (<a href="#RFC5226" id="rfc.xref.RFC5226.2"><cite title="Guidelines for Writing an IANA Considerations Section in RFCs">[RFC5226]</cite></a>, <a href="http://tools.ietf.org/html/rfc5226#section-4.1">Section 4.1</a>).
    879       </p>
    880       <p id="rfc.section.4.1.p.3">The registry itself is maintained at &lt;<a href="http://www.iana.org/assignments/http-status-codes">http://www.iana.org/assignments/http-status-codes</a>&gt;.
    881       </p>
    882       <h1 id="rfc.section.5"><a href="#rfc.section.5">5.</a>&nbsp;<a id="response.header.fields" href="#response.header.fields">Response Header Fields</a></h1>
    883       <p id="rfc.section.5.p.1">The response-header fields allow the server to pass additional information about the response which cannot be placed in the
    884          Status-Line. These header fields give information about the server and about further access to the target resource (<a href="p1-messaging.html#effective.request.uri" title="Effective Request URI">Section 4.3</a> of <a href="#Part1" id="rfc.xref.Part1.20"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>).
    885       </p>
    886       <div id="rfc.figure.u.11"></div><pre class="inline"><span id="rfc.iref.g.7"></span>  <a href="#response.header.fields" class="smpl">response-header</a> = <a href="#abnf.dependencies" class="smpl">Accept-Ranges</a>           ; <a href="#Part5" id="rfc.xref.Part5.9"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>, <a href="p5-range.html#header.accept-ranges" title="Accept-Ranges">Section 5.1</a>
    887                   / <a href="#abnf.dependencies" class="smpl">Age</a>                     ; <a href="#Part6" id="rfc.xref.Part6.3"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>, <a href="p6-cache.html#header.age" title="Age">Section 3.1</a>
    888                   / <a href="#header.allow" class="smpl">Allow</a>                   ; <a href="#header.allow" id="rfc.xref.header.allow.2" title="Allow">Section&nbsp;9.1</a>
    889                   / <a href="#abnf.dependencies" class="smpl">ETag</a>                    ; <a href="#Part4" id="rfc.xref.Part4.13"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>, <a href="p4-conditional.html#header.etag" title="ETag">Section 6.1</a>
    890                   / <a href="#header.location" class="smpl">Location</a>                ; <a href="#header.location" id="rfc.xref.header.location.1" title="Location">Section&nbsp;9.4</a>
    891                   / <a href="#abnf.dependencies" class="smpl">Proxy-Authenticate</a>      ; <a href="#Part7" id="rfc.xref.Part7.10"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a>, <a href="p7-auth.html#header.proxy-authenticate" title="Proxy-Authenticate">Section 4.2</a>
    892                   / <a href="#header.retry-after" class="smpl">Retry-After</a>             ; <a href="#header.retry-after" id="rfc.xref.header.retry-after.1" title="Retry-After">Section&nbsp;9.7</a>
    893                   / <a href="#header.server" class="smpl">Server</a>                  ; <a href="#header.server" id="rfc.xref.header.server.1" title="Server">Section&nbsp;9.8</a>
    894                   / <a href="#abnf.dependencies" class="smpl">Vary</a>                    ; <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.vary" title="Vary">Section 3.5</a>
    895                   / <a href="#abnf.dependencies" class="smpl">WWW-Authenticate</a>        ; <a href="#Part7" id="rfc.xref.Part7.11"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a>, <a href="p7-auth.html#header.www-authenticate" title="WWW-Authenticate">Section 4.4</a>
    896 </pre><p id="rfc.section.5.p.3">Response-header field names can be extended reliably only in combination with a change in the protocol version. However, new
    897          or experimental header fields <em class="bcp14">MAY</em> be given the semantics of response-header fields if all parties in the communication recognize them to be response-header
    898          fields.
    899       </p>
    900       <h1 id="rfc.section.6"><a href="#rfc.section.6">6.</a>&nbsp;<a id="representation" href="#representation">Representation</a></h1>
    901       <p id="rfc.section.6.p.1">Request and Response messages <em class="bcp14">MAY</em> transfer a representation if not otherwise restricted by the request method or response status code. A representation consists
    902          of metadata (representation header fields) and data (representation body). When a complete or partial representation is enclosed
    903          in an HTTP message, it is referred to as the payload of the message. HTTP representations are defined in <a href="#Part3" id="rfc.xref.Part3.9"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>.
    904       </p>
    905       <p id="rfc.section.6.p.2">A representation body is only present in a message when a message-body is present, as described in <a href="p1-messaging.html#message.body" title="Message Body">Section 3.3</a> of <a href="#Part1" id="rfc.xref.Part1.21"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>. The representation body is obtained from the message-body by decoding any Transfer-Encoding that might have been applied
    906          to ensure safe and proper transfer of the message.
    907       </p>
    908       <h2 id="rfc.section.6.1"><a href="#rfc.section.6.1">6.1</a>&nbsp;<a id="identifying.response.associated.with.representation" href="#identifying.response.associated.with.representation">Identifying the Resource Associated with a Representation</a></h2>
    909       <p id="rfc.section.6.1.p.1">It is sometimes necessary to determine an identifier for the resource associated with a representation.</p>
    910       <p id="rfc.section.6.1.p.2">An HTTP request representation, when present, is always associated with an anonymous (i.e., unidentified) resource.</p>
    911       <p id="rfc.section.6.1.p.3">In the common case, an HTTP response is a representation of the target resource (see <a href="p1-messaging.html#effective.request.uri" title="Effective Request URI">Section 4.3</a> of <a href="#Part1" id="rfc.xref.Part1.22"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>). However, this is not always the case. To determine the URI of the resource a response is associated with, the following
    912          rules are used (with the first applicable one being selected):
    913       </p>
    914       <ol>
    915          <li>If the response status code is 200 or 203 and the request method was GET, the response payload is a representation of the
    916             target resource.
    917          </li>
    918          <li>If the response status code is 204, 206, or 304 and the request method was GET or HEAD, the response payload is a partial
    919             representation of the target (see <a href="p6-cache.html#combining.responses" title="Combining Responses">Section 2.8</a> of <a href="#Part6" id="rfc.xref.Part6.5"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>).
    920          </li>
    921          <li>If the response has a Content-Location header field, and that URI is the same as the effective request URI, the response payload
    922             is a representation of the target resource.
    923          </li>
    924          <li>If the response has a Content-Location header field, and that URI is not the same as the effective request URI, then the response
    925             asserts that its payload is a representation of the resource identified by the Content-Location URI. However, such an assertion
    926             cannot be trusted unless it can be verified by other means (not defined by HTTP).
    927          </li>
    928          <li>Otherwise, the response is a representation of an anonymous (i.e., unidentified) resource.</li>
    929       </ol>
    930       <p id="rfc.section.6.1.p.5"> <span class="comment" id="TODO-req-uri">[<a href="#TODO-req-uri" class="smpl">TODO-req-uri</a>: The comparison function is going to have to be defined somewhere, because we already need to compare URIs for things like
    931             cache invalidation.]</span>
    932       </p>
    933       <h1 id="rfc.section.7"><a href="#rfc.section.7">7.</a>&nbsp;<a id="method.definitions" href="#method.definitions">Method Definitions</a></h1>
    934       <p id="rfc.section.7.p.1">The set of common methods for HTTP/1.1 is defined below. Although this set can be expanded, additional methods cannot be assumed
    935          to share the same semantics for separately extended clients and servers.
    936       </p>
    937       <h2 id="rfc.section.7.1"><a href="#rfc.section.7.1">7.1</a>&nbsp;<a id="safe.and.idempotent" href="#safe.and.idempotent">Safe and Idempotent Methods</a></h2>
    938       <div id="rfc.iref.s.1"></div>
    939       <h3 id="rfc.section.7.1.1"><a href="#rfc.section.7.1.1">7.1.1</a>&nbsp;<a id="safe.methods" href="#safe.methods">Safe Methods</a></h3>
    940       <p id="rfc.section.7.1.1.p.1">Implementors need to be aware that the software represents the user in their interactions over the Internet, and need to allow
    941          the user to be aware of any actions they take which might have an unexpected significance to themselves or others.
    942       </p>
    943       <p id="rfc.section.7.1.1.p.2">In particular, the convention has been established that the GET, HEAD, OPTIONS, and TRACE methods <em class="bcp14">SHOULD NOT</em> have the significance of taking an action other than retrieval. These methods ought to be considered "<dfn id="safe">safe</dfn>". This allows user agents to represent other methods, such as POST, PUT and DELETE, in a special way, so that the user is
    944          made aware of the fact that a possibly unsafe action is being requested.
    945       </p>
    946       <p id="rfc.section.7.1.1.p.3">Naturally, it is not possible to ensure that the server does not generate side-effects as a result of performing a GET request;
    947          in fact, some dynamic resources consider that a feature. The important distinction here is that the user did not request the
    948          side-effects, so therefore cannot be held accountable for them.
    949       </p>
    950       <div id="rfc.iref.i.1"></div>
    951       <h3 id="rfc.section.7.1.2"><a href="#rfc.section.7.1.2">7.1.2</a>&nbsp;<a id="idempotent.methods" href="#idempotent.methods">Idempotent Methods</a></h3>
    952       <p id="rfc.section.7.1.2.p.1">Methods can also have the property of "idempotence" in that, aside from error or expiration issues, the intended effect of
    953          multiple identical requests is the same as for a single request. The methods PUT, DELETE, and all safe methods are idempotent.
    954          It is important to note that idempotence refers only to changes requested by the client: a server is free to change its state
    955          due to multiple requests for the purpose of tracking those requests, versioning of results, etc.
    956       </p>
    957       <h2 id="rfc.section.7.2"><a href="#rfc.section.7.2">7.2</a>&nbsp;<a id="OPTIONS" href="#OPTIONS">OPTIONS</a></h2>
    958       <div id="rfc.iref.o.1"></div>
    959       <div id="rfc.iref.m.1"></div>
    960       <p id="rfc.section.7.2.p.1">The OPTIONS method represents a request for information about the communication options available on the request/response
    961          chain identified by the effective request URI. This method allows the client to determine the options and/or requirements
    962          associated with a resource, or the capabilities of a server, without implying a resource action or initiating a resource retrieval.
    963       </p>
    964       <p id="rfc.section.7.2.p.2">Responses to this method are not cacheable.</p>
    965       <p id="rfc.section.7.2.p.3">If the OPTIONS request includes a message-body (as indicated by the presence of Content-Length or Transfer-Encoding), then
    966          the media type <em class="bcp14">MUST</em> be indicated by a Content-Type field. Although this specification does not define any use for such a body, future extensions
    967          to HTTP might use the OPTIONS body to make more detailed queries on the server.
    968       </p>
    969       <p id="rfc.section.7.2.p.4">If the request-target is an asterisk ("*"), the OPTIONS request is intended to apply to the server in general rather than
    970          to a specific resource. Since a server's communication options typically depend on the resource, the "*" request is only useful
    971          as a "ping" or "no-op" type of method; it does nothing beyond allowing the client to test the capabilities of the server.
    972          For example, this can be used to test a proxy for HTTP/1.1 compliance (or lack thereof).
    973       </p>
    974       <p id="rfc.section.7.2.p.5">If the request-target is not an asterisk, the OPTIONS request applies only to the options that are available when communicating
    975          with that resource.
    976       </p>
    977       <p id="rfc.section.7.2.p.6">A 200 response <em class="bcp14">SHOULD</em> include any header fields that indicate optional features implemented by the server and applicable to that resource (e.g.,
    978          Allow), possibly including extensions not defined by this specification. The response body, if any, <em class="bcp14">SHOULD</em> also include information about the communication options. The format for such a body is not defined by this specification,
    979          but might be defined by future extensions to HTTP. Content negotiation <em class="bcp14">MAY</em> be used to select the appropriate response format. If no response body is included, the response <em class="bcp14">MUST</em> include a Content-Length field with a field-value of "0".
    980       </p>
    981       <p id="rfc.section.7.2.p.7">The Max-Forwards request-header field <em class="bcp14">MAY</em> be used to target a specific proxy in the request chain (see <a href="#header.max-forwards" id="rfc.xref.header.max-forwards.2" title="Max-Forwards">Section&nbsp;9.5</a>). If no Max-Forwards field is present in the request, then the forwarded request <em class="bcp14">MUST NOT</em> include a Max-Forwards field.
    982       </p>
    983       <h2 id="rfc.section.7.3"><a href="#rfc.section.7.3">7.3</a>&nbsp;<a id="GET" href="#GET">GET</a></h2>
    984       <div id="rfc.iref.g.8"></div>
    985       <div id="rfc.iref.m.2"></div>
    986       <p id="rfc.section.7.3.p.1">The GET method means retrieve whatever information (in the form of a representation) currently corresponds to the target resource.</p>
    987       <p id="rfc.section.7.3.p.2">If the target resource is a data-producing process, it is the produced data which shall be returned as the representation
    988          in the response and not the source text of the process, unless that text happens to be the output of the process.
    989       </p>
    990       <p id="rfc.section.7.3.p.3">The semantics of the GET method change to a "conditional GET" if the request message includes an If-Modified-Since, If-Unmodified-Since,
    991          If-Match, If-None-Match, or If-Range header field. A conditional GET method requests that the representation be transferred
    992          only under the circumstances described by the conditional header field(s). The conditional GET method is intended to reduce
    993          unnecessary network usage by allowing cached representations to be refreshed without requiring multiple requests or transferring
    994          data already held by the client.
    995       </p>
    996       <p id="rfc.section.7.3.p.4">The semantics of the GET method change to a "partial GET" if the request message includes a Range header field. A partial
    997          GET requests that only part of the representation be transferred, as described in <a href="p5-range.html#header.range" title="Range">Section 5.4</a> of <a href="#Part5" id="rfc.xref.Part5.10"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>. The partial GET method is intended to reduce unnecessary network usage by allowing partially-retrieved representations to
    998          be completed without transferring data already held by the client.
    999       </p>
    1000       <p id="rfc.section.7.3.p.5">The response to a GET request is cacheable and <em class="bcp14">MAY</em> be used to satisfy subsequent GET and HEAD requests (see <a href="#Part6" id="rfc.xref.Part6.6"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>).
    1001       </p>
    1002       <p id="rfc.section.7.3.p.6">See <a href="#encoding.sensitive.information.in.uris" title="Encoding Sensitive Information in URIs">Section&nbsp;11.2</a> for security considerations when used for forms.
    1003       </p>
    1004       <h2 id="rfc.section.7.4"><a href="#rfc.section.7.4">7.4</a>&nbsp;<a id="HEAD" href="#HEAD">HEAD</a></h2>
    1005       <div id="rfc.iref.h.1"></div>
    1006       <div id="rfc.iref.m.3"></div>
    1007       <p id="rfc.section.7.4.p.1">The HEAD method is identical to GET except that the server <em class="bcp14">MUST NOT</em> return a message-body in the response. The metadata contained in the HTTP header fields in response to a HEAD request <em class="bcp14">SHOULD</em> be identical to the information sent in response to a GET request. This method can be used for obtaining metadata about the
    1008          representation implied by the request without transferring the representation body. This method is often used for testing
    1009          hypertext links for validity, accessibility, and recent modification.
    1010       </p>
    1011       <p id="rfc.section.7.4.p.2">The response to a HEAD request is cacheable and <em class="bcp14">MAY</em> be used to satisfy a subsequent HEAD request; see <a href="#Part6" id="rfc.xref.Part6.7"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>. It also <em class="bcp14">MAY</em> be used to update a previously cached representation from that resource; if the new field values indicate that the cached
    1012          representation differs from the current representation (as would be indicated by a change in Content-Length, Content-MD5,
    1013          ETag or Last-Modified), then the cache <em class="bcp14">MUST</em> treat the cache entry as stale.
    1014       </p>
    1015       <div id="rfc.iref.p.1"></div>
    1016       <div id="rfc.iref.m.4"></div>
    1017       <h2 id="rfc.section.7.5"><a href="#rfc.section.7.5">7.5</a>&nbsp;<a id="POST" href="#POST">POST</a></h2>
    1018       <p id="rfc.section.7.5.p.1">The POST method is used to request that the origin server accept the representation enclosed in the request as data to be
    1019          processed by the target resource. POST is designed to allow a uniform method to cover the following functions:
    1020       </p>
    1021       <ul>
    1022          <li>Annotation of existing resources;</li>
    1023          <li>Posting a message to a bulletin board, newsgroup, mailing list, or similar group of articles;</li>
    1024          <li>Providing a block of data, such as the result of submitting a form, to a data-handling process;</li>
    1025          <li>Extending a database through an append operation.</li>
    1026       </ul>
    1027       <p id="rfc.section.7.5.p.2">The actual function performed by the POST method is determined by the server and is usually dependent on the effective request
    1028          URI.
    1029       </p>
    1030       <p id="rfc.section.7.5.p.3">The action performed by the POST method might not result in a resource that can be identified by a URI. In this case, either
    1031          200 (OK) or 204 (No Content) is the appropriate response status code, depending on whether or not the response includes a
    1032          representation that describes the result.
    1033       </p>
    1034       <p id="rfc.section.7.5.p.4">If a resource has been created on the origin server, the response <em class="bcp14">SHOULD</em> be 201 (Created) and contain a representation which describes the status of the request and refers to the new resource, and
    1035          a Location header field (see <a href="#header.location" id="rfc.xref.header.location.2" title="Location">Section&nbsp;9.4</a>).
    1036       </p>
    1037       <p id="rfc.section.7.5.p.5">Responses to POST requests are only cacheable when they include explicit freshness information (see <a href="p6-cache.html#calculating.freshness.lifetime" title="Calculating Freshness Lifetime">Section 2.3.1</a> of <a href="#Part6" id="rfc.xref.Part6.8"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>). A cached POST response with a Content-Location header field (see <a href="p3-payload.html#header.content-location" title="Content-Location">Section 6.7</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>) whose value is the effective Request URI <em class="bcp14">MAY</em> be used to satisfy subsequent GET and HEAD requests.
    1038       </p>
    1039       <p id="rfc.section.7.5.p.6">Note that POST caching is not widely implemented. However, the 303 (See Other) response can be used to direct the user agent
    1040          to retrieve a cacheable resource.
    1041       </p>
    1042       <div id="rfc.iref.p.2"></div>
    1043       <div id="rfc.iref.m.5"></div>
    1044       <h2 id="rfc.section.7.6"><a href="#rfc.section.7.6">7.6</a>&nbsp;<a id="PUT" href="#PUT">PUT</a></h2>
    1045       <p id="rfc.section.7.6.p.1">The PUT method requests that the enclosed representation be stored at the effective request URI. If the effective request
    1046          URI refers to an already existing resource, the enclosed representation <em class="bcp14">SHOULD</em> be considered a modified version of the one residing on the origin server. Otherwise, if the effective request URI does not
    1047          point to an existing resource, and that URI is capable of being defined as a new resource by the requesting user agent, the
    1048          origin server can create the resource with that URI.
    1049       </p>
    1050       <p id="rfc.section.7.6.p.2">If a new resource is created at the effective request URI, the origin server <em class="bcp14">MUST</em> inform the user agent via the 201 (Created) response. If an existing resource is modified, either the 200 (OK) or 204 (No
    1051          Content) response codes <em class="bcp14">SHOULD</em> be sent to indicate successful completion of the request.
    1052       </p>
    1053       <p id="rfc.section.7.6.p.3">If the target resource could not be created or modified, an appropriate error response <em class="bcp14">SHOULD</em> be given that reflects the nature of the problem. The recipient of the representation <em class="bcp14">MUST NOT</em> ignore any Content-* header fields (headers starting with the prefix "Content-") that it does not understand or implement
    1054          and <em class="bcp14">MUST</em> return a 501 (Not Implemented) response in such cases.
    1055       </p>
    1056       <p id="rfc.section.7.6.p.4">If the request passes through a cache that has one or more stored responses for the effective request URI, those stored responses <em class="bcp14">SHOULD</em> be marked as stale if the response to the PUT request has a success status code. Responses to the PUT method are not cacheable.
    1057       </p>
    1058       <p id="rfc.section.7.6.p.5">The fundamental difference between the POST and PUT requests is reflected in the different meaning of the effective request
    1059          URI. The URI in a POST request identifies the resource that will handle the enclosed representation. That resource might be
    1060          a data-accepting process, a gateway to some other protocol, or a document that accepts annotations. In contrast, the URI in
    1061          a PUT request identifies the resource for which enclosed representation is a new or replacement value; the user agent knows
    1062          what URI is intended and the server <em class="bcp14">MUST NOT</em> attempt to apply the request to some other resource. If the server desires that the request be applied to a different URI,
    1063          it <em class="bcp14">MUST</em> send a 301 (Moved Permanently) response; the user agent <em class="bcp14">MAY</em> then make its own decision regarding whether or not to redirect the request.
    1064       </p>
    1065       <p id="rfc.section.7.6.p.6">A single resource <em class="bcp14">MAY</em> be identified by many different URIs. For example, an article might have a URI for identifying "the current version" which
    1066          is separate from the URI identifying each particular version. In this case, a PUT request on a general URI might result in
    1067          several other URIs being defined by the origin server.
    1068       </p>
    1069       <p id="rfc.section.7.6.p.7">HTTP/1.1 does not define how a PUT method affects the state of an origin server.</p>
    1070       <p id="rfc.section.7.6.p.8">Header fields in a PUT request that are recognized as representation metadata <em class="bcp14">SHOULD</em> be applied to the resource created or modified by the PUT. Unrecognized header fields <em class="bcp14">SHOULD</em> be ignored.
    1071       </p>
    1072       <div id="rfc.iref.d.1"></div>
    1073       <div id="rfc.iref.m.6"></div>
    1074       <h2 id="rfc.section.7.7"><a href="#rfc.section.7.7">7.7</a>&nbsp;<a id="DELETE" href="#DELETE">DELETE</a></h2>
    1075       <p id="rfc.section.7.7.p.1">The DELETE method requests that the origin server delete the target resource. This method <em class="bcp14">MAY</em> be overridden by human intervention (or other means) on the origin server. The client cannot be guaranteed that the operation
    1076          has been carried out, even if the status code returned from the origin server indicates that the action has been completed
    1077          successfully. However, the server <em class="bcp14">SHOULD NOT</em> indicate success unless, at the time the response is given, it intends to delete the resource or move it to an inaccessible
    1078          location.
    1079       </p>
    1080       <p id="rfc.section.7.7.p.2">A successful response <em class="bcp14">SHOULD</em> be 200 (OK) if the response includes an representation describing the status, 202 (Accepted) if the action has not yet been
    1081          enacted, or 204 (No Content) if the action has been enacted but the response does not include a representation.
    1082       </p>
    1083       <p id="rfc.section.7.7.p.3">If the request passes through a cache and the effective request URI identifies one or more currently cached representations,
    1084          those entries <em class="bcp14">SHOULD</em> be treated as stale. Responses to the DELETE method are not cacheable.
    1085       </p>
    1086       <h2 id="rfc.section.7.8"><a href="#rfc.section.7.8">7.8</a>&nbsp;<a id="TRACE" href="#TRACE">TRACE</a></h2>
    1087       <div id="rfc.iref.t.1"></div>
    1088       <div id="rfc.iref.m.7"></div>
    1089       <p id="rfc.section.7.8.p.1">The TRACE method is used to invoke a remote, application-layer loop-back of the request message. The final recipient of the
    1090          request <em class="bcp14">SHOULD</em> reflect the message received back to the client as the message-body of a 200 (OK) response. The final recipient is either
    1091          the origin server or the first proxy or gateway to receive a Max-Forwards value of zero (0) in the request (see <a href="#header.max-forwards" id="rfc.xref.header.max-forwards.3" title="Max-Forwards">Section&nbsp;9.5</a>). A TRACE request <em class="bcp14">MUST NOT</em> include a message-body.
    1092       </p>
    1093       <p id="rfc.section.7.8.p.2">TRACE allows the client to see what is being received at the other end of the request chain and use that data for testing
    1094          or diagnostic information. The value of the Via header field (<a href="p1-messaging.html#header.via" title="Via">Section 9.9</a> of <a href="#Part1" id="rfc.xref.Part1.23"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) is of particular interest, since it acts as a trace of the request chain. Use of the Max-Forwards header field allows the
    1095          client to limit the length of the request chain, which is useful for testing a chain of proxies forwarding messages in an
    1096          infinite loop.
    1097       </p>
    1098       <p id="rfc.section.7.8.p.3">If the request is valid, the response <em class="bcp14">SHOULD</em> have a Content-Type of "message/http" (see <a href="p1-messaging.html#internet.media.type.message.http" title="Internet Media Type message/http">Section 10.3.1</a> of <a href="#Part1" id="rfc.xref.Part1.24"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) and contain a message-body that encloses a copy of the entire request message. Responses to the TRACE method are not cacheable.
    1099       </p>
    1100       <div id="rfc.iref.c.1"></div>
    1101       <div id="rfc.iref.m.8"></div>
    1102       <h2 id="rfc.section.7.9"><a href="#rfc.section.7.9">7.9</a>&nbsp;<a id="CONNECT" href="#CONNECT">CONNECT</a></h2>
    1103       <p id="rfc.section.7.9.p.1">This specification reserves the method name CONNECT for use with a proxy that can dynamically switch to being a tunnel (e.g.,
    1104          SSL tunneling <a href="#RFC2817" id="rfc.xref.RFC2817.1"><cite title="Upgrading to TLS Within HTTP/1.1">[RFC2817]</cite></a>).
    1105       </p>
    1106       <h1 id="rfc.section.8"><a href="#rfc.section.8">8.</a>&nbsp;<a id="status.codes" href="#status.codes">Status Code Definitions</a></h1>
    1107       <p id="rfc.section.8.p.1">Each Status-Code is described below, including any metadata required in the response.</p>
    1108       <h2 id="rfc.section.8.1"><a href="#rfc.section.8.1">8.1</a>&nbsp;<a id="status.1xx" href="#status.1xx">Informational 1xx</a></h2>
    1109       <p id="rfc.section.8.1.p.1">This class of status code indicates a provisional response, consisting only of the Status-Line and optional header fields,
    1110          and is terminated by an empty line. There are no required header fields for this class of status code. Since HTTP/1.0 did
    1111          not define any 1xx status codes, servers <em class="bcp14">MUST NOT</em> send a 1xx response to an HTTP/1.0 client except under experimental conditions.
    1112       </p>
    1113       <p id="rfc.section.8.1.p.2">A client <em class="bcp14">MUST</em> be prepared to accept one or more 1xx status responses prior to a regular response, even if the client does not expect a 100
    1114          (Continue) status message. Unexpected 1xx status responses <em class="bcp14">MAY</em> be ignored by a user agent.
    1115       </p>
    1116       <p id="rfc.section.8.1.p.3">Proxies <em class="bcp14">MUST</em> forward 1xx responses, unless the connection between the proxy and its client has been closed, or unless the proxy itself
    1117          requested the generation of the 1xx response. (For example, if a proxy adds a "Expect: 100-continue" field when it forwards
    1118          a request, then it need not forward the corresponding 100 (Continue) response(s).)
    1119       </p>
    1120       <div id="rfc.iref.25"></div>
    1121       <div id="rfc.iref.s.2"></div>
    1122       <h3 id="rfc.section.8.1.1"><a href="#rfc.section.8.1.1">8.1.1</a>&nbsp;<a id="status.100" href="#status.100">100 Continue</a></h3>
    1123       <p id="rfc.section.8.1.1.p.1">The client <em class="bcp14">SHOULD</em> continue with its request. This interim response is used to inform the client that the initial part of the request has been
    1124          received and has not yet been rejected by the server. The client <em class="bcp14">SHOULD</em> continue by sending the remainder of the request or, if the request has already been completed, ignore this response. The
    1125          server <em class="bcp14">MUST</em> send a final response after the request has been completed. See <a href="p1-messaging.html#use.of.the.100.status" title="Use of the 100 (Continue) Status">Section 7.2.3</a> of <a href="#Part1" id="rfc.xref.Part1.25"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a> for detailed discussion of the use and handling of this status code.
    1126       </p>
    1127       <div id="rfc.iref.26"></div>
    1128       <div id="rfc.iref.s.3"></div>
    1129       <h3 id="rfc.section.8.1.2"><a href="#rfc.section.8.1.2">8.1.2</a>&nbsp;<a id="status.101" href="#status.101">101 Switching Protocols</a></h3>
    1130       <p id="rfc.section.8.1.2.p.1">The server understands and is willing to comply with the client's request, via the Upgrade message header field (<a href="p1-messaging.html#header.upgrade" title="Upgrade">Section 9.8</a> of <a href="#Part1" id="rfc.xref.Part1.26"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>), for a change in the application protocol being used on this connection. The server will switch protocols to those defined
    1131          by the response's Upgrade header field immediately after the empty line which terminates the 101 response.
    1132       </p>
    1133       <p id="rfc.section.8.1.2.p.2">The protocol <em class="bcp14">SHOULD</em> be switched only when it is advantageous to do so. For example, switching to a newer version of HTTP is advantageous over
    1134          older versions, and switching to a real-time, synchronous protocol might be advantageous when delivering resources that use
    1135          such features.
    1136       </p>
    1137       <h2 id="rfc.section.8.2"><a href="#rfc.section.8.2">8.2</a>&nbsp;<a id="status.2xx" href="#status.2xx">Successful 2xx</a></h2>
    1138       <p id="rfc.section.8.2.p.1">This class of status code indicates that the client's request was successfully received, understood, and accepted.</p>
    1139       <div id="rfc.iref.27"></div>
    1140       <div id="rfc.iref.s.4"></div>
    1141       <h3 id="rfc.section.8.2.1"><a href="#rfc.section.8.2.1">8.2.1</a>&nbsp;<a id="status.200" href="#status.200">200 OK</a></h3>
    1142       <p id="rfc.section.8.2.1.p.1">The request has succeeded. The payload returned with the response is dependent on the method used in the request, for example: </p>
    1143       <dl>
    1144          <dt>GET</dt>
    1145          <dd>a representation of the target resource is sent in the response;</dd>
    1146          <dt>HEAD</dt>
    1147          <dd>the same representation as GET, except without the message-body;</dd>
    1148          <dt>POST</dt>
    1149          <dd>a representation describing or containing the result of the action;</dd>
    1150          <dt>TRACE</dt>
    1151          <dd>a representation containing the request message as received by the end server.</dd>
    1152       </dl>
    1153       <p id="rfc.section.8.2.1.p.2">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.9"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 200 responses.
    1154       </p>
    1155       <div id="rfc.iref.28"></div>
    1156       <div id="rfc.iref.s.5"></div>
    1157       <h3 id="rfc.section.8.2.2"><a href="#rfc.section.8.2.2">8.2.2</a>&nbsp;<a id="status.201" href="#status.201">201 Created</a></h3>
    1158       <p id="rfc.section.8.2.2.p.1">The request has been fulfilled and has resulted in a new resource being created. The newly created resource can be referenced
    1159          by the URI(s) returned in the payload of the response, with the most specific URI for the resource given by a Location header
    1160          field. The response <em class="bcp14">SHOULD</em> include a payload containing a list of resource characteristics and location(s) from which the user or user agent can choose
    1161          the one most appropriate. The payload format is specified by the media type given in the Content-Type header field. The origin
    1162          server <em class="bcp14">MUST</em> create the resource before returning the 201 status code. If the action cannot be carried out immediately, the server <em class="bcp14">SHOULD</em> respond with 202 (Accepted) response instead.
    1163       </p>
    1164       <p id="rfc.section.8.2.2.p.2">A 201 response <em class="bcp14">MAY</em> contain an ETag response header field indicating the current value of the entity-tag for the representation of the resource
    1165          just created (see <a href="p4-conditional.html#header.etag" title="ETag">Section 6.1</a> of <a href="#Part4" id="rfc.xref.Part4.14"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>).
    1166       </p>
    1167       <div id="rfc.iref.29"></div>
    1168       <div id="rfc.iref.s.6"></div>
    1169       <h3 id="rfc.section.8.2.3"><a href="#rfc.section.8.2.3">8.2.3</a>&nbsp;<a id="status.202" href="#status.202">202 Accepted</a></h3>
    1170       <p id="rfc.section.8.2.3.p.1">The request has been accepted for processing, but the processing has not been completed. The request might or might not eventually
    1171          be acted upon, as it might be disallowed when processing actually takes place. There is no facility for re-sending a status
    1172          code from an asynchronous operation such as this.
    1173       </p>
    1174       <p id="rfc.section.8.2.3.p.2">The 202 response is intentionally non-committal. Its purpose is to allow a server to accept a request for some other process
    1175          (perhaps a batch-oriented process that is only run once per day) without requiring that the user agent's connection to the
    1176          server persist until the process is completed. The representation returned with this response <em class="bcp14">SHOULD</em> include an indication of the request's current status and either a pointer to a status monitor or some estimate of when the
    1177          user can expect the request to be fulfilled.
    1178       </p>
    1179       <div id="rfc.iref.30"></div>
    1180       <div id="rfc.iref.s.7"></div>
    1181       <h3 id="rfc.section.8.2.4"><a href="#rfc.section.8.2.4">8.2.4</a>&nbsp;<a id="status.203" href="#status.203">203 Non-Authoritative Information</a></h3>
    1182       <p id="rfc.section.8.2.4.p.1">The returned metadata in the header fields is not the definitive set as available from the origin server, but is gathered
    1183          from a local or a third-party copy. The set presented <em class="bcp14">MAY</em> be a subset or superset of the original version. For example, including local annotation information about the resource might
    1184          result in a superset of the metadata known by the origin server. Use of this response code is not required and is only appropriate
    1185          when the response would otherwise be 200 (OK).
    1186       </p>
    1187       <p id="rfc.section.8.2.4.p.2">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.10"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 203 responses.
    1188       </p>
    1189       <div id="rfc.iref.31"></div>
    1190       <div id="rfc.iref.s.8"></div>
    1191       <h3 id="rfc.section.8.2.5"><a href="#rfc.section.8.2.5">8.2.5</a>&nbsp;<a id="status.204" href="#status.204">204 No Content</a></h3>
    1192       <p id="rfc.section.8.2.5.p.1">The server has successfully fulfilled the request, but there is no additional content to return in the response payload body.
    1193          The resource metadata and representation metadata in the response message's header fields refer to the target resource and
    1194          its current representation, respectively, after the requested action. For example, if a 204 status code is received in response
    1195          to a PUT and the response contains an ETag header field, then the value of that field is the current entity-tag for the representation
    1196          that was successfully PUT.
    1197       </p>
    1198       <p id="rfc.section.8.2.5.p.2">If the client is a user agent, it <em class="bcp14">SHOULD NOT</em> change its document view from that which caused the request to be sent. This response is primarily intended to allow input
    1199          for actions to take place without causing a change to the user agent's active document view, although any new or updated metadata <em class="bcp14">SHOULD</em> be applied to the document currently in the user agent's active view.
    1200       </p>
    1201       <p id="rfc.section.8.2.5.p.3">The 204 response <em class="bcp14">MUST NOT</em> include a message-body, and thus is always terminated by the first empty line after the header fields.
    1202       </p>
    1203       <div id="rfc.iref.32"></div>
    1204       <div id="rfc.iref.s.9"></div>
    1205       <h3 id="rfc.section.8.2.6"><a href="#rfc.section.8.2.6">8.2.6</a>&nbsp;<a id="status.205" href="#status.205">205 Reset Content</a></h3>
    1206       <p id="rfc.section.8.2.6.p.1">The server has fulfilled the request and the user agent <em class="bcp14">SHOULD</em> reset the document view which caused the request to be sent. This response is primarily intended to allow input for actions
    1207          to take place via user input, followed by a clearing of the form in which the input is given so that the user can easily initiate
    1208          another input action. The response <em class="bcp14">MUST NOT</em> include a message-body.
    1209       </p>
    1210       <div id="rfc.iref.33"></div>
    1211       <div id="rfc.iref.s.10"></div>
    1212       <h3 id="rfc.section.8.2.7"><a href="#rfc.section.8.2.7">8.2.7</a>&nbsp;<a id="status.206" href="#status.206">206 Partial Content</a></h3>
    1213       <p id="rfc.section.8.2.7.p.1">The server has fulfilled the partial GET request for the resource and the enclosed payload is a partial representation as
    1214          defined in <a href="p5-range.html#status.206" title="206 Partial Content">Section 3.1</a> of <a href="#Part5" id="rfc.xref.Part5.11"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>.
    1215       </p>
    1216       <p id="rfc.section.8.2.7.p.2">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.11"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 206 responses.
    1217       </p>
    1218       <h2 id="rfc.section.8.3"><a href="#rfc.section.8.3">8.3</a>&nbsp;<a id="status.3xx" href="#status.3xx">Redirection 3xx</a></h2>
    1219       <p id="rfc.section.8.3.p.1">This class of status code indicates that further action needs to be taken by the user agent in order to fulfill the request.
    1220          The action required <em class="bcp14">MAY</em> be carried out by the user agent without interaction with the user if and only if the method used in the second request is
    1221          known to be "safe", as defined in <a href="#safe.methods" title="Safe Methods">Section&nbsp;7.1.1</a>. A client <em class="bcp14">SHOULD</em> detect infinite redirection loops, since such loops generate network traffic for each redirection.
    1222       </p>
    1223       <div class="note" id="rfc.section.8.3.p.2">
    1224          <p> <b>Note:</b> An earlier version of this specification recommended a maximum of five redirections (<a href="#RFC2068" id="rfc.xref.RFC2068.1"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2068]</cite></a>, <a href="http://tools.ietf.org/html/rfc2068#section-10.3">Section 10.3</a>). Content developers need to be aware that some clients might implement such a fixed limitation.
    1225          </p>
    1226       </div>
    1227       <div id="rfc.iref.34"></div>
    1228       <div id="rfc.iref.s.11"></div>
    1229       <h3 id="rfc.section.8.3.1"><a href="#rfc.section.8.3.1">8.3.1</a>&nbsp;<a id="status.300" href="#status.300">300 Multiple Choices</a></h3>
    1230       <p id="rfc.section.8.3.1.p.1">The target resource has more than one representation, each with its own specific location, and agent-driven negotiation information
    1231          (<a href="p3-payload.html#content.negotiation" title="Content Negotiation">Section 5</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>) is being provided so that the user (or user agent) can select a preferred representation by redirecting its request to that
    1232          location.
    1233       </p>
    1234       <p id="rfc.section.8.3.1.p.2">Unless it was a HEAD request, the response <em class="bcp14">SHOULD</em> include a representation containing a list of representation metadata and location(s) from which the user or user agent can
    1235          choose the one most appropriate. The data format is specified by the media type given in the Content-Type header field. Depending
    1236          upon the format and the capabilities of the user agent, selection of the most appropriate choice <em class="bcp14">MAY</em> be performed automatically. However, this specification does not define any standard for such automatic selection.
    1237       </p>
    1238       <p id="rfc.section.8.3.1.p.3">If the server has a preferred choice of representation, it <em class="bcp14">SHOULD</em> include the specific URI for that representation in the Location field; user agents <em class="bcp14">MAY</em> use the Location field value for automatic redirection.
    1239       </p>
    1240       <p id="rfc.section.8.3.1.p.4">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.12"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 300 responses.
    1241       </p>
    1242       <div id="rfc.iref.35"></div>
    1243       <div id="rfc.iref.s.12"></div>
    1244       <h3 id="rfc.section.8.3.2"><a href="#rfc.section.8.3.2">8.3.2</a>&nbsp;<a id="status.301" href="#status.301">301 Moved Permanently</a></h3>
    1245       <p id="rfc.section.8.3.2.p.1">The target resource has been assigned a new permanent URI and any future references to this resource <em class="bcp14">SHOULD</em> use one of the returned URIs. Clients with link editing capabilities ought to automatically re-link references to the effective
    1246          request URI to one or more of the new references returned by the server, where possible.
    1247       </p>
    1248       <p id="rfc.section.8.3.2.p.2">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.13"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 301 responses.
    1249       </p>
    1250       <p id="rfc.section.8.3.2.p.3">The new permanent URI <em class="bcp14">SHOULD</em> be given by the Location field in the response. Unless the request method was HEAD, the representation of the response <em class="bcp14">SHOULD</em> contain a short hypertext note with a hyperlink to the new URI(s).
    1251       </p>
    1252       <p id="rfc.section.8.3.2.p.4">If the 301 status code is received in response to a request method that is known to be "safe", as defined in <a href="#safe.methods" title="Safe Methods">Section&nbsp;7.1.1</a>, then the request <em class="bcp14">MAY</em> be automatically redirected by the user agent without confirmation. Otherwise, the user agent <em class="bcp14">MUST NOT</em> automatically redirect the request unless it can be confirmed by the user, since this might change the conditions under which
    1253          the request was issued.
    1254       </p>
    1255       <div class="note" id="rfc.section.8.3.2.p.5">
    1256          <p> <b>Note:</b> When automatically redirecting a POST request after receiving a 301 status code, some existing HTTP/1.0 user agents will erroneously
    1257             change it into a GET request.
    1258          </p>
    1259       </div>
    1260       <div id="rfc.iref.36"></div>
    1261       <div id="rfc.iref.s.13"></div>
    1262       <h3 id="rfc.section.8.3.3"><a href="#rfc.section.8.3.3">8.3.3</a>&nbsp;<a id="status.302" href="#status.302">302 Found</a></h3>
    1263       <p id="rfc.section.8.3.3.p.1">The target resource resides temporarily under a different URI. Since the redirection might be altered on occasion, the client <em class="bcp14">SHOULD</em> continue to use the effective request URI for future requests.
    1264       </p>
    1265       <p id="rfc.section.8.3.3.p.2">The temporary URI <em class="bcp14">SHOULD</em> be given by the Location field in the response. Unless the request method was HEAD, the representation of the response <em class="bcp14">SHOULD</em> contain a short hypertext note with a hyperlink to the new URI(s).
    1266       </p>
    1267       <p id="rfc.section.8.3.3.p.3">If the 302 status code is received in response to a request method that is known to be "safe", as defined in <a href="#safe.methods" title="Safe Methods">Section&nbsp;7.1.1</a>, then the request <em class="bcp14">MAY</em> be automatically redirected by the user agent without confirmation. Otherwise, the user agent <em class="bcp14">MUST NOT</em> automatically redirect the request unless it can be confirmed by the user, since this might change the conditions under which
    1268          the request was issued.
    1269       </p>
    1270       <div class="note" id="rfc.section.8.3.3.p.4">
    1271          <p> <b>Note:</b> HTTP/1.0 (<a href="#RFC1945" id="rfc.xref.RFC1945.1"><cite title="Hypertext Transfer Protocol -- HTTP/1.0">[RFC1945]</cite></a>, <a href="http://tools.ietf.org/html/rfc1945#section-9.3">Section 9.3</a>) and the first version of HTTP/1.1 (<a href="#RFC2068" id="rfc.xref.RFC2068.2"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2068]</cite></a>, <a href="http://tools.ietf.org/html/rfc2068#section-10.3.3">Section 10.3.3</a>) specify that the client is not allowed to change the method on the redirected request. However, most existing user agent
    1272             implementations treat 302 as if it were a 303 response, performing a GET on the Location field-value regardless of the original
    1273             request method. Therefore, a previous version of this specification (<a href="#RFC2616" id="rfc.xref.RFC2616.2"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>, <a href="http://tools.ietf.org/html/rfc2616#section-10.3.3">Section 10.3.3</a>) has added the status codes <a href="#status.303" id="rfc.xref.status.303.2">303</a> and <a href="#status.307" id="rfc.xref.status.307.2">307</a> for servers that wish to make unambiguously clear which kind of reaction is expected of the client.
    1274          </p>
    1275       </div>
    1276       <div id="rfc.iref.37"></div>
    1277       <div id="rfc.iref.s.14"></div>
    1278       <h3 id="rfc.section.8.3.4"><a href="#rfc.section.8.3.4">8.3.4</a>&nbsp;<a id="status.303" href="#status.303">303 See Other</a></h3>
    1279       <p id="rfc.section.8.3.4.p.1">The server directs the user agent to a different resource, indicated by a URI in the Location header field, that provides
    1280          an indirect response to the original request. The user agent <em class="bcp14">MAY</em> perform a GET request on the URI in the Location field in order to obtain a representation corresponding to the response,
    1281          be redirected again, or end with an error status. The Location URI is not a substitute reference for the effective request
    1282          URI.
    1283       </p>
    1284       <p id="rfc.section.8.3.4.p.2">The 303 status code is generally applicable to any HTTP method. It is primarily used to allow the output of a POST action
    1285          to redirect the user agent to a selected resource, since doing so provides the information corresponding to the POST response
    1286          in a form that can be separately identified, bookmarked, and cached independent of the original request.
    1287       </p>
    1288       <p id="rfc.section.8.3.4.p.3">A 303 response to a GET request indicates that the requested resource does not have a representation of its own that can be
    1289          transferred by the server over HTTP. The Location URI indicates a resource that is descriptive of the target resource, such
    1290          that the follow-on representation might be useful to recipients without implying that it adequately represents the target
    1291          resource. Note that answers to the questions of what can be represented, what representations are adequate, and what might
    1292          be a useful description are outside the scope of HTTP and thus entirely determined by the URI owner(s).
    1293       </p>
    1294       <p id="rfc.section.8.3.4.p.4">Except for responses to a HEAD request, the representation of a 303 response <em class="bcp14">SHOULD</em> contain a short hypertext note with a hyperlink to the Location URI.
    1295       </p>
    1296       <div id="rfc.iref.38"></div>
    1297       <div id="rfc.iref.s.15"></div>
    1298       <h3 id="rfc.section.8.3.5"><a href="#rfc.section.8.3.5">8.3.5</a>&nbsp;<a id="status.304" href="#status.304">304 Not Modified</a></h3>
    1299       <p id="rfc.section.8.3.5.p.1">The response to the request has not been modified since the conditions indicated by the client's conditional GET request,
    1300          as defined in <a href="p4-conditional.html#status.304" title="304 Not Modified">Section 3.1</a> of <a href="#Part4" id="rfc.xref.Part4.15"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>.
    1301       </p>
    1302       <div id="rfc.iref.39"></div>
    1303       <div id="rfc.iref.s.16"></div>
    1304       <h3 id="rfc.section.8.3.6"><a href="#rfc.section.8.3.6">8.3.6</a>&nbsp;<a id="status.305" href="#status.305">305 Use Proxy</a></h3>
    1305       <p id="rfc.section.8.3.6.p.1">The 305 status code was defined in a previous version of this specification (see <a href="#changes.from.rfc.2616" title="Changes from RFC 2616">Appendix&nbsp;A</a>), and is now deprecated.
    1306       </p>
    1307       <div id="rfc.iref.40"></div>
    1308       <div id="rfc.iref.s.17"></div>
    1309       <h3 id="rfc.section.8.3.7"><a href="#rfc.section.8.3.7">8.3.7</a>&nbsp;<a id="status.306" href="#status.306">306 (Unused)</a></h3>
    1310       <p id="rfc.section.8.3.7.p.1">The 306 status code was used in a previous version of the specification, is no longer used, and the code is reserved.</p>
    1311       <div id="rfc.iref.41"></div>
    1312       <div id="rfc.iref.s.18"></div>
    1313       <h3 id="rfc.section.8.3.8"><a href="#rfc.section.8.3.8">8.3.8</a>&nbsp;<a id="status.307" href="#status.307">307 Temporary Redirect</a></h3>
    1314       <p id="rfc.section.8.3.8.p.1">The target resource resides temporarily under a different URI. Since the redirection can change over time, the client <em class="bcp14">SHOULD</em> continue to use the effective request URI for future requests.
    1315       </p>
    1316       <p id="rfc.section.8.3.8.p.2">The temporary URI <em class="bcp14">SHOULD</em> be given by the Location field in the response. Unless the request method was HEAD, the representation of the response <em class="bcp14">SHOULD</em> contain a short hypertext note with a hyperlink to the new URI(s), since many pre-HTTP/1.1 user agents do not understand the
    1317          307 status code. Therefore, the note <em class="bcp14">SHOULD</em> contain the information necessary for a user to repeat the original request on the new URI.
    1318       </p>
    1319       <p id="rfc.section.8.3.8.p.3">If the 307 status code is received in response to a request method that is known to be "safe", as defined in <a href="#safe.methods" title="Safe Methods">Section&nbsp;7.1.1</a>, then the request <em class="bcp14">MAY</em> be automatically redirected by the user agent without confirmation. Otherwise, the user agent <em class="bcp14">MUST NOT</em> automatically redirect the request unless it can be confirmed by the user, since this might change the conditions under which
    1320          the request was issued.
    1321       </p>
    1322       <h2 id="rfc.section.8.4"><a href="#rfc.section.8.4">8.4</a>&nbsp;<a id="status.4xx" href="#status.4xx">Client Error 4xx</a></h2>
    1323       <p id="rfc.section.8.4.p.1">The 4xx class of status code is intended for cases in which the client seems to have erred. Except when responding to a HEAD
    1324          request, the server <em class="bcp14">SHOULD</em> include a representation containing an explanation of the error situation, and whether it is a temporary or permanent condition.
    1325          These status codes are applicable to any request method. User agents <em class="bcp14">SHOULD</em> display any included representation to the user.
    1326       </p>
    1327       <p id="rfc.section.8.4.p.2">If the client is sending data, a server implementation using TCP <em class="bcp14">SHOULD</em> be careful to ensure that the client acknowledges receipt of the packet(s) containing the response, before the server closes
    1328          the input connection. If the client continues sending data to the server after the close, the server's TCP stack will send
    1329          a reset packet to the client, which might erase the client's unacknowledged input buffers before they can be read and interpreted
    1330          by the HTTP application.
    1331       </p>
    1332       <div id="rfc.iref.42"></div>
    1333       <div id="rfc.iref.s.19"></div>
    1334       <h3 id="rfc.section.8.4.1"><a href="#rfc.section.8.4.1">8.4.1</a>&nbsp;<a id="status.400" href="#status.400">400 Bad Request</a></h3>
    1335       <p id="rfc.section.8.4.1.p.1">The request could not be understood by the server due to malformed syntax. The client <em class="bcp14">SHOULD NOT</em> repeat the request without modifications.
    1336       </p>
    1337       <div id="rfc.iref.43"></div>
    1338       <div id="rfc.iref.s.20"></div>
    1339       <h3 id="rfc.section.8.4.2"><a href="#rfc.section.8.4.2">8.4.2</a>&nbsp;<a id="status.401" href="#status.401">401 Unauthorized</a></h3>
    1340       <p id="rfc.section.8.4.2.p.1">The request requires user authentication (see <a href="p7-auth.html#status.401" title="401 Unauthorized">Section 3.1</a> of <a href="#Part7" id="rfc.xref.Part7.12"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a>).
    1341       </p>
    1342       <div id="rfc.iref.44"></div>
    1343       <div id="rfc.iref.s.21"></div>
    1344       <h3 id="rfc.section.8.4.3"><a href="#rfc.section.8.4.3">8.4.3</a>&nbsp;<a id="status.402" href="#status.402">402 Payment Required</a></h3>
    1345       <p id="rfc.section.8.4.3.p.1">This code is reserved for future use.</p>
    1346       <div id="rfc.iref.45"></div>
    1347       <div id="rfc.iref.s.22"></div>
    1348       <h3 id="rfc.section.8.4.4"><a href="#rfc.section.8.4.4">8.4.4</a>&nbsp;<a id="status.403" href="#status.403">403 Forbidden</a></h3>
    1349       <p id="rfc.section.8.4.4.p.1">The server understood the request, but is refusing to fulfill it. Authorization will not help and the request <em class="bcp14">SHOULD NOT</em> be repeated. If the request method was not HEAD and the server wishes to make public why the request has not been fulfilled,
    1350          it <em class="bcp14">SHOULD</em> describe the reason for the refusal in the representation. If the server does not wish to make this information available
    1351          to the client, the status code 404 (Not Found) can be used instead.
    1352       </p>
    1353       <div id="rfc.iref.46"></div>
    1354       <div id="rfc.iref.s.23"></div>
    1355       <h3 id="rfc.section.8.4.5"><a href="#rfc.section.8.4.5">8.4.5</a>&nbsp;<a id="status.404" href="#status.404">404 Not Found</a></h3>
    1356       <p id="rfc.section.8.4.5.p.1">The server has not found anything matching the effective request URI. No indication is given of whether the condition is temporary
    1357          or permanent. The 410 (Gone) status code <em class="bcp14">SHOULD</em> be used if the server knows, through some internally configurable mechanism, that an old resource is permanently unavailable
    1358          and has no forwarding address. This status code is commonly used when the server does not wish to reveal exactly why the request
    1359          has been refused, or when no other response is applicable.
    1360       </p>
    1361       <div id="rfc.iref.47"></div>
    1362       <div id="rfc.iref.s.24"></div>
    1363       <h3 id="rfc.section.8.4.6"><a href="#rfc.section.8.4.6">8.4.6</a>&nbsp;<a id="status.405" href="#status.405">405 Method Not Allowed</a></h3>
    1364       <p id="rfc.section.8.4.6.p.1">The method specified in the Request-Line is not allowed for the target resource. The response <em class="bcp14">MUST</em> include an Allow header field containing a list of valid methods for the requested resource.
    1365       </p>
    1366       <div id="rfc.iref.48"></div>
    1367       <div id="rfc.iref.s.25"></div>
    1368       <h3 id="rfc.section.8.4.7"><a href="#rfc.section.8.4.7">8.4.7</a>&nbsp;<a id="status.406" href="#status.406">406 Not Acceptable</a></h3>
    1369       <p id="rfc.section.8.4.7.p.1">The resource identified by the request is only capable of generating response representations which have content characteristics
    1370          not acceptable according to the accept header fields sent in the request.
    1371       </p>
    1372       <p id="rfc.section.8.4.7.p.2">Unless it was a HEAD request, the response <em class="bcp14">SHOULD</em> include a representation containing a list of available representation characteristics and location(s) from which the user
    1373          or user agent can choose the one most appropriate. The data format is specified by the media type given in the Content-Type
    1374          header field. Depending upon the format and the capabilities of the user agent, selection of the most appropriate choice <em class="bcp14">MAY</em> be performed automatically. However, this specification does not define any standard for such automatic selection.
    1375       </p>
    1376       <div class="note" id="rfc.section.8.4.7.p.3">
    1377          <p> <b>Note:</b> HTTP/1.1 servers are allowed to return responses which are not acceptable according to the accept header fields sent in the
    1378             request. In some cases, this might even be preferable to sending a 406 response. User agents are encouraged to inspect the
    1379             header fields of an incoming response to determine if it is acceptable.
    1380          </p>
    1381       </div>
    1382       <p id="rfc.section.8.4.7.p.4">If the response could be unacceptable, a user agent <em class="bcp14">SHOULD</em> temporarily stop receipt of more data and query the user for a decision on further actions.
    1383       </p>
    1384       <div id="rfc.iref.49"></div>
    1385       <div id="rfc.iref.s.26"></div>
    1386       <h3 id="rfc.section.8.4.8"><a href="#rfc.section.8.4.8">8.4.8</a>&nbsp;<a id="status.407" href="#status.407">407 Proxy Authentication Required</a></h3>
    1387       <p id="rfc.section.8.4.8.p.1">This code is similar to 401 (Unauthorized), but indicates that the client must first authenticate itself with the proxy (see <a href="p7-auth.html#status.407" title="407 Proxy Authentication Required">Section 3.2</a> of <a href="#Part7" id="rfc.xref.Part7.13"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a>).
    1388       </p>
    1389       <div id="rfc.iref.50"></div>
    1390       <div id="rfc.iref.s.27"></div>
    1391       <h3 id="rfc.section.8.4.9"><a href="#rfc.section.8.4.9">8.4.9</a>&nbsp;<a id="status.408" href="#status.408">408 Request Timeout</a></h3>
    1392       <p id="rfc.section.8.4.9.p.1">The client did not produce a request within the time that the server was prepared to wait. The client <em class="bcp14">MAY</em> repeat the request without modifications at any later time.
    1393       </p>
    1394       <div id="rfc.iref.51"></div>
    1395       <div id="rfc.iref.s.28"></div>
    1396       <h3 id="rfc.section.8.4.10"><a href="#rfc.section.8.4.10">8.4.10</a>&nbsp;<a id="status.409" href="#status.409">409 Conflict</a></h3>
    1397       <p id="rfc.section.8.4.10.p.1">The request could not be completed due to a conflict with the current state of the resource. This code is only allowed in
    1398          situations where it is expected that the user might be able to resolve the conflict and resubmit the request. The response
    1399          body <em class="bcp14">SHOULD</em> include enough information for the user to recognize the source of the conflict. Ideally, the response representation would
    1400          include enough information for the user or user agent to fix the problem; however, that might not be possible and is not required.
    1401       </p>
    1402       <p id="rfc.section.8.4.10.p.2">Conflicts are most likely to occur in response to a PUT request. For example, if versioning were being used and the representation
    1403          being PUT included changes to a resource which conflict with those made by an earlier (third-party) request, the server might
    1404          use the 409 response to indicate that it can't complete the request. In this case, the response representation would likely
    1405          contain a list of the differences between the two versions in a format defined by the response Content-Type.
    1406       </p>
    1407       <div id="rfc.iref.52"></div>
    1408       <div id="rfc.iref.s.29"></div>
    1409       <h3 id="rfc.section.8.4.11"><a href="#rfc.section.8.4.11">8.4.11</a>&nbsp;<a id="status.410" href="#status.410">410 Gone</a></h3>
    1410       <p id="rfc.section.8.4.11.p.1">The target resource is no longer available at the server and no forwarding address is known. This condition is expected to
    1411          be considered permanent. Clients with link editing capabilities <em class="bcp14">SHOULD</em> delete references to the effective request URI after user approval. If the server does not know, or has no facility to determine,
    1412          whether or not the condition is permanent, the status code 404 (Not Found) <em class="bcp14">SHOULD</em> be used instead.
    1413       </p>
    1414       <p id="rfc.section.8.4.11.p.2">The 410 response is primarily intended to assist the task of web maintenance by notifying the recipient that the resource
    1415          is intentionally unavailable and that the server owners desire that remote links to that resource be removed. Such an event
    1416          is common for limited-time, promotional services and for resources belonging to individuals no longer working at the server's
    1417          site. It is not necessary to mark all permanently unavailable resources as "gone" or to keep the mark for any length of time
    1418          -- that is left to the discretion of the server owner.
    1419       </p>
    1420       <p id="rfc.section.8.4.11.p.3">Caches <em class="bcp14">MAY</em> use a heuristic (see <a href="p6-cache.html#heuristic.freshness" title="Calculating Heuristic Freshness">Section 2.3.1.1</a> of <a href="#Part6" id="rfc.xref.Part6.14"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) to determine freshness for 410 responses.
    1421       </p>
    1422       <div id="rfc.iref.53"></div>
    1423       <div id="rfc.iref.s.30"></div>
    1424       <h3 id="rfc.section.8.4.12"><a href="#rfc.section.8.4.12">8.4.12</a>&nbsp;<a id="status.411" href="#status.411">411 Length Required</a></h3>
    1425       <p id="rfc.section.8.4.12.p.1">The server refuses to accept the request without a defined Content-Length. The client <em class="bcp14">MAY</em> repeat the request if it adds a valid Content-Length header field containing the length of the message-body in the request
    1426          message.
    1427       </p>
    1428       <div id="rfc.iref.54"></div>
    1429       <div id="rfc.iref.s.31"></div>
    1430       <h3 id="rfc.section.8.4.13"><a href="#rfc.section.8.4.13">8.4.13</a>&nbsp;<a id="status.412" href="#status.412">412 Precondition Failed</a></h3>
    1431       <p id="rfc.section.8.4.13.p.1">The precondition given in one or more of the request-header fields evaluated to false when it was tested on the server, as
    1432          defined in <a href="p4-conditional.html#status.412" title="412 Precondition Failed">Section 3.2</a> of <a href="#Part4" id="rfc.xref.Part4.16"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>.
    1433       </p>
    1434       <div id="rfc.iref.55"></div>
    1435       <div id="rfc.iref.s.32"></div>
    1436       <h3 id="rfc.section.8.4.14"><a href="#rfc.section.8.4.14">8.4.14</a>&nbsp;<a id="status.413" href="#status.413">413 Request Entity Too Large</a></h3>
    1437       <p id="rfc.section.8.4.14.p.1">The server is refusing to process a request because the request representation is larger than the server is willing or able
    1438          to process. The server <em class="bcp14">MAY</em> close the connection to prevent the client from continuing the request.
    1439       </p>
    1440       <p id="rfc.section.8.4.14.p.2">If the condition is temporary, the server <em class="bcp14">SHOULD</em> include a Retry-After header field to indicate that it is temporary and after what time the client <em class="bcp14">MAY</em> try again.
    1441       </p>
    1442       <div id="rfc.iref.56"></div>
    1443       <div id="rfc.iref.s.33"></div>
    1444       <h3 id="rfc.section.8.4.15"><a href="#rfc.section.8.4.15">8.4.15</a>&nbsp;<a id="status.414" href="#status.414">414 URI Too Long</a></h3>
    1445       <p id="rfc.section.8.4.15.p.1">The server is refusing to service the request because the effective request URI is longer than the server is willing to interpret.
    1446          This rare condition is only likely to occur when a client has improperly converted a POST request to a GET request with long
    1447          query information, when the client has descended into a URI "black hole" of redirection (e.g., a redirected URI prefix that
    1448          points to a suffix of itself), or when the server is under attack by a client attempting to exploit security holes present
    1449          in some servers using fixed-length buffers for reading or manipulating the effective request URI.
    1450       </p>
    1451       <div id="rfc.iref.57"></div>
    1452       <div id="rfc.iref.s.34"></div>
    1453       <h3 id="rfc.section.8.4.16"><a href="#rfc.section.8.4.16">8.4.16</a>&nbsp;<a id="status.415" href="#status.415">415 Unsupported Media Type</a></h3>
    1454       <p id="rfc.section.8.4.16.p.1">The server is refusing to service the request because the representation of the request is in a format not supported by the
    1455          target resource for the requested method.
    1456       </p>
    1457       <div id="rfc.iref.58"></div>
    1458       <div id="rfc.iref.s.35"></div>
    1459       <h3 id="rfc.section.8.4.17"><a href="#rfc.section.8.4.17">8.4.17</a>&nbsp;<a id="status.416" href="#status.416">416 Requested Range Not Satisfiable</a></h3>
    1460       <p id="rfc.section.8.4.17.p.1">The request included a Range request-header field (<a href="p5-range.html#header.range" title="Range">Section 5.4</a> of <a href="#Part5" id="rfc.xref.Part5.12"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>) and none of the range-specifier values in this field overlap the current extent of the selected resource. See <a href="p5-range.html#status.416" title="416 Requested Range Not Satisfiable">Section 3.2</a> of <a href="#Part5" id="rfc.xref.Part5.13"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>.
    1461       </p>
    1462       <div id="rfc.iref.59"></div>
    1463       <div id="rfc.iref.s.36"></div>
    1464       <h3 id="rfc.section.8.4.18"><a href="#rfc.section.8.4.18">8.4.18</a>&nbsp;<a id="status.417" href="#status.417">417 Expectation Failed</a></h3>
    1465       <p id="rfc.section.8.4.18.p.1">The expectation given in an Expect request-header field (see <a href="#header.expect" id="rfc.xref.header.expect.2" title="Expect">Section&nbsp;9.2</a>) could not be met by this server, or, if the server is a proxy, the server has unambiguous evidence that the request could
    1466          not be met by the next-hop server.
    1467       </p>
    1468       <h2 id="rfc.section.8.5"><a href="#rfc.section.8.5">8.5</a>&nbsp;<a id="status.5xx" href="#status.5xx">Server Error 5xx</a></h2>
    1469       <p id="rfc.section.8.5.p.1">Response status codes beginning with the digit "5" indicate cases in which the server is aware that it has erred or is incapable
    1470          of performing the request. Except when responding to a HEAD request, the server <em class="bcp14">SHOULD</em> include a representation containing an explanation of the error situation, and whether it is a temporary or permanent condition.
    1471          User agents <em class="bcp14">SHOULD</em> display any included representation to the user. These response codes are applicable to any request method.
    1472       </p>
    1473       <div id="rfc.iref.60"></div>
    1474       <div id="rfc.iref.s.37"></div>
    1475       <h3 id="rfc.section.8.5.1"><a href="#rfc.section.8.5.1">8.5.1</a>&nbsp;<a id="status.500" href="#status.500">500 Internal Server Error</a></h3>
    1476       <p id="rfc.section.8.5.1.p.1">The server encountered an unexpected condition which prevented it from fulfilling the request.</p>
    1477       <div id="rfc.iref.61"></div>
    1478       <div id="rfc.iref.s.38"></div>
    1479       <h3 id="rfc.section.8.5.2"><a href="#rfc.section.8.5.2">8.5.2</a>&nbsp;<a id="status.501" href="#status.501">501 Not Implemented</a></h3>
    1480       <p id="rfc.section.8.5.2.p.1">The server does not support the functionality required to fulfill the request. This is the appropriate response when the server
    1481          does not recognize the request method and is not capable of supporting it for any resource.
    1482       </p>
    1483       <div id="rfc.iref.62"></div>
    1484       <div id="rfc.iref.s.39"></div>
    1485       <h3 id="rfc.section.8.5.3"><a href="#rfc.section.8.5.3">8.5.3</a>&nbsp;<a id="status.502" href="#status.502">502 Bad Gateway</a></h3>
    1486       <p id="rfc.section.8.5.3.p.1">The server, while acting as a gateway or proxy, received an invalid response from the upstream server it accessed in attempting
    1487          to fulfill the request.
    1488       </p>
    1489       <div id="rfc.iref.63"></div>
    1490       <div id="rfc.iref.s.40"></div>
    1491       <h3 id="rfc.section.8.5.4"><a href="#rfc.section.8.5.4">8.5.4</a>&nbsp;<a id="status.503" href="#status.503">503 Service Unavailable</a></h3>
    1492       <p id="rfc.section.8.5.4.p.1">The server is currently unable to handle the request due to a temporary overloading or maintenance of the server. The implication
    1493          is that this is a temporary condition which will be alleviated after some delay. If known, the length of the delay <em class="bcp14">MAY</em> be indicated in a Retry-After header field. If no Retry-After is given, the client <em class="bcp14">SHOULD</em> handle the response as it would for a 500 response.
    1494       </p>
    1495       <div class="note" id="rfc.section.8.5.4.p.2">
    1496          <p> <b>Note:</b> The existence of the 503 status code does not imply that a server must use it when becoming overloaded. Some servers might
    1497             wish to simply refuse the connection.
    1498          </p>
    1499       </div>
    1500       <div id="rfc.iref.64"></div>
    1501       <div id="rfc.iref.s.41"></div>
    1502       <h3 id="rfc.section.8.5.5"><a href="#rfc.section.8.5.5">8.5.5</a>&nbsp;<a id="status.504" href="#status.504">504 Gateway Timeout</a></h3>
    1503       <p id="rfc.section.8.5.5.p.1">The server, while acting as a gateway or proxy, did not receive a timely response from the upstream server specified by the
    1504          URI (e.g., HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed to access in attempting to complete the request.
    1505       </p>
    1506       <div class="note" id="rfc.section.8.5.5.p.2">
    1507          <p> <b>Note</b> to implementors: some deployed proxies are known to return 400 or 500 when DNS lookups time out.
    1508          </p>
    1509       </div>
    1510       <div id="rfc.iref.65"></div>
    1511       <div id="rfc.iref.s.42"></div>
    1512       <h3 id="rfc.section.8.5.6"><a href="#rfc.section.8.5.6">8.5.6</a>&nbsp;<a id="status.505" href="#status.505">505 HTTP Version Not Supported</a></h3>
    1513       <p id="rfc.section.8.5.6.p.1">The server does not support, or refuses to support, the protocol version that was used in the request message. The server
    1514          is indicating that it is unable or unwilling to complete the request using the same major version as the client, as described
    1515          in <a href="p1-messaging.html#http.version" title="HTTP Version">Section 2.5</a> of <a href="#Part1" id="rfc.xref.Part1.27"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, other than with this error message. The response <em class="bcp14">SHOULD</em> contain a representation describing why that version is not supported and what other protocols are supported by that server.
    1516       </p>
    1517       <h1 id="rfc.section.9"><a href="#rfc.section.9">9.</a>&nbsp;<a id="header.fields" href="#header.fields">Header Field Definitions</a></h1>
    1518       <p id="rfc.section.9.p.1">This section defines the syntax and semantics of HTTP/1.1 header fields related to request and response semantics.</p>
    1519       <div id="rfc.iref.a.1"></div>
    1520       <div id="rfc.iref.h.2"></div>
    1521       <h2 id="rfc.section.9.1"><a href="#rfc.section.9.1">9.1</a>&nbsp;<a id="header.allow" href="#header.allow">Allow</a></h2>
    1522       <p id="rfc.section.9.1.p.1">The "Allow" response-header field lists the set of methods advertised as supported by the target resource. The purpose of
    1523          this field is strictly to inform the recipient of valid methods associated with the resource.
    1524       </p>
    1525       <div id="rfc.figure.u.12"></div><pre class="inline"><span id="rfc.iref.g.9"></span><span id="rfc.iref.g.10"></span>  <a href="#header.allow" class="smpl">Allow</a>   = "Allow" ":" <a href="#core.rules" class="smpl">OWS</a> <a href="#header.allow" class="smpl">Allow-v</a>
    1526   <a href="#header.allow" class="smpl">Allow-v</a> = #<a href="#method" class="smpl">Method</a>
    1527 </pre><p id="rfc.section.9.1.p.3">Example of use:</p>
    1528       <div id="rfc.figure.u.13"></div><pre class="text">  Allow: GET, HEAD, PUT
    1529 </pre><p id="rfc.section.9.1.p.5">The actual set of allowed methods is defined by the origin server at the time of each request.</p>
    1530       <p id="rfc.section.9.1.p.6">A proxy <em class="bcp14">MUST NOT</em> modify the Allow header field even if it does not understand all the methods specified, since the user agent might have other
    1531          means of communicating with the origin server.
    1532       </p>
    1533       <div id="rfc.iref.e.1"></div>
    1534       <div id="rfc.iref.h.3"></div>
    1535       <h2 id="rfc.section.9.2"><a href="#rfc.section.9.2">9.2</a>&nbsp;<a id="header.expect" href="#header.expect">Expect</a></h2>
    1536       <p id="rfc.section.9.2.p.1">The "Expect" request-header field is used to indicate that particular server behaviors are required by the client.</p>
    1537       <div id="rfc.figure.u.14"></div><pre class="inline"><span id="rfc.iref.g.11"></span><span id="rfc.iref.g.12"></span><span id="rfc.iref.g.13"></span><span id="rfc.iref.g.14"></span><span id="rfc.iref.g.15"></span>  <a href="#header.expect" class="smpl">Expect</a>       = "Expect" ":" <a href="#core.rules" class="smpl">OWS</a> <a href="#header.expect" class="smpl">Expect-v</a>
    1538   <a href="#header.expect" class="smpl">Expect-v</a>     = 1#<a href="#header.expect" class="smpl">expectation</a>
    1539  
    1540   <a href="#header.expect" class="smpl">expectation</a>  = "100-continue" / <a href="#header.expect" class="smpl">expectation-extension</a>
    1541   <a href="#header.expect" class="smpl">expectation-extension</a> = <a href="#core.rules" class="smpl">token</a> [ "=" ( <a href="#core.rules" class="smpl">token</a> / <a href="#core.rules" class="smpl">quoted-string</a> )
    1542                            *<a href="#header.expect" class="smpl">expect-params</a> ]
    1543   <a href="#header.expect" class="smpl">expect-params</a> = ";" <a href="#core.rules" class="smpl">token</a> [ "=" ( <a href="#core.rules" class="smpl">token</a> / <a href="#core.rules" class="smpl">quoted-string</a> ) ]
    1544 </pre><p id="rfc.section.9.2.p.3">A server that does not understand or is unable to comply with any of the expectation values in the Expect field of a request <em class="bcp14">MUST</em> respond with appropriate error status code. The server <em class="bcp14">MUST</em> respond with a 417 (Expectation Failed) status code if any of the expectations cannot be met or, if there are other problems
    1545          with the request, some other 4xx status code.
    1546       </p>
    1547       <p id="rfc.section.9.2.p.4">This header field is defined with extensible syntax to allow for future extensions. If a server receives a request containing
    1548          an Expect field that includes an expectation-extension that it does not support, it <em class="bcp14">MUST</em> respond with a 417 (Expectation Failed) status code.
    1549       </p>
    1550       <p id="rfc.section.9.2.p.5">Comparison of expectation values is case-insensitive for unquoted tokens (including the 100-continue token), and is case-sensitive
    1551          for quoted-string expectation-extensions.
    1552       </p>
    1553       <p id="rfc.section.9.2.p.6">The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy <em class="bcp14">MUST</em> return a 417 (Expectation Failed) status code if it receives a request with an expectation that it cannot meet. However, the
    1554          Expect request-header field itself is end-to-end; it <em class="bcp14">MUST</em> be forwarded if the request is forwarded.
    1555       </p>
    1556       <p id="rfc.section.9.2.p.7">Many older HTTP/1.0 and HTTP/1.1 applications do not understand the Expect header field.</p>
    1557       <p id="rfc.section.9.2.p.8">See <a href="p1-messaging.html#use.of.the.100.status" title="Use of the 100 (Continue) Status">Section 7.2.3</a> of <a href="#Part1" id="rfc.xref.Part1.28"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a> for the use of the 100 (Continue) status code.
    1558       </p>
    1559       <div id="rfc.iref.f.1"></div>
    1560       <div id="rfc.iref.h.4"></div>
    1561       <h2 id="rfc.section.9.3"><a href="#rfc.section.9.3">9.3</a>&nbsp;<a id="header.from" href="#header.from">From</a></h2>
    1562       <p id="rfc.section.9.3.p.1">The "From" request-header field, if given, <em class="bcp14">SHOULD</em> contain an Internet e-mail address for the human user who controls the requesting user agent. The address <em class="bcp14">SHOULD</em> be machine-usable, as defined by "mailbox" in <a href="http://tools.ietf.org/html/rfc5322#section-3.4">Section 3.4</a> of <a href="#RFC5322" id="rfc.xref.RFC5322.1"><cite title="Internet Message Format">[RFC5322]</cite></a>:
    1563       </p>
    1564       <div id="rfc.figure.u.15"></div><pre class="inline"><span id="rfc.iref.g.16"></span><span id="rfc.iref.g.17"></span>  <a href="#header.from" class="smpl">From</a>    = "From" ":" <a href="#core.rules" class="smpl">OWS</a> <a href="#header.from" class="smpl">From-v</a>
    1565   <a href="#header.from" class="smpl">From-v</a>  = <a href="#header.from" class="smpl">mailbox</a>
    1566  
    1567   <a href="#header.from" class="smpl">mailbox</a> = &lt;mailbox, defined in <a href="#RFC5322" id="rfc.xref.RFC5322.2"><cite title="Internet Message Format">[RFC5322]</cite></a>, <a href="http://tools.ietf.org/html/rfc5322#section-3.4">Section 3.4</a>&gt;
    1568 </pre><p id="rfc.section.9.3.p.3">An example is:</p>
    1569       <div id="rfc.figure.u.16"></div><pre class="text">  From: webmaster@example.org
    1570 </pre><p id="rfc.section.9.3.p.5">This header field <em class="bcp14">MAY</em> be used for logging purposes and as a means for identifying the source of invalid or unwanted requests. It <em class="bcp14">SHOULD NOT</em> be used as an insecure form of access protection. The interpretation of this field is that the request is being performed
    1571          on behalf of the person given, who accepts responsibility for the method performed. In particular, robot agents <em class="bcp14">SHOULD</em> include this header field so that the person responsible for running the robot can be contacted if problems occur on the receiving
    1572          end.
    1573       </p>
    1574       <p id="rfc.section.9.3.p.6">The Internet e-mail address in this field <em class="bcp14">MAY</em> be separate from the Internet host which issued the request. For example, when a request is passed through a proxy the original
    1575          issuer's address <em class="bcp14">SHOULD</em> be used.
    1576       </p>
    1577       <p id="rfc.section.9.3.p.7">The client <em class="bcp14">SHOULD NOT</em> send the From header field without the user's approval, as it might conflict with the user's privacy interests or their site's
    1578          security policy. It is strongly recommended that the user be able to disable, enable, and modify the value of this field at
    1579          any time prior to a request.
    1580       </p>
    1581       <div id="rfc.iref.l.1"></div>
    1582       <div id="rfc.iref.h.5"></div>
    1583       <h2 id="rfc.section.9.4"><a href="#rfc.section.9.4">9.4</a>&nbsp;<a id="header.location" href="#header.location">Location</a></h2>
    1584       <p id="rfc.section.9.4.p.1">The "Location" response-header field is used to identify a newly created resource, or to redirect the recipient to a different
    1585          location for completion of the request.
    1586       </p>
    1587       <p id="rfc.section.9.4.p.2">For 201 (Created) responses, the Location is the URI of the new resource which was created by the request. For 3xx responses,
    1588          the location <em class="bcp14">SHOULD</em> indicate the server's preferred URI for automatic redirection to the resource.
    1589       </p>
    1590       <p id="rfc.section.9.4.p.3">The field value consists of a single URI-reference. When it has the form of a relative reference (<a href="#RFC3986" id="rfc.xref.RFC3986.1"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a>, <a href="http://tools.ietf.org/html/rfc3986#section-4.2">Section 4.2</a>), the final value is computed by resolving it against the effective request URI (<a href="#RFC3986" id="rfc.xref.RFC3986.2"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a>, <a href="http://tools.ietf.org/html/rfc3986#section-5">Section 5</a>).
    1591       </p>
    1592       <div id="rfc.figure.u.17"></div><pre class="inline"><span id="rfc.iref.g.18"></span><span id="rfc.iref.g.19"></span>  <a href="#header.location" class="smpl">Location</a>       = "Location" ":" <a href="#core.rules" class="smpl">OWS</a> <a href="#header.location" class="smpl">Location-v</a>
    1593   <a href="#header.location" class="smpl">Location-v</a>     = <a href="#abnf.dependencies" class="smpl">URI-reference</a>
    1594 </pre><div id="rfc.figure.u.18"></div>
    1595       <p>Examples are:</p>  <pre class="text">  Location: http://www.example.org/pub/WWW/People.html#tim
    1596 </pre><div id="rfc.figure.u.19"></div><pre class="text">  Location: /index.html
    1597 </pre><p id="rfc.section.9.4.p.7">There are circumstances in which a fragment identifier in a Location URI would not be appropriate: </p>
    1598       <ul>
    1599          <li>With a 201 Created response, because in this usage the Location header field specifies the URI for the entire created resource.</li>
    1600          <li>With 305 Use Proxy.</li>
    1601       </ul>
    1602       <div class="note" id="rfc.section.9.4.p.8">
    1603          <p> <b>Note:</b> This specification does not define precedence rules for the case where the original URI, as navigated to by the user agent,
    1604             and the Location header field value both contain fragment identifiers.
    1605          </p>
    1606       </div>
    1607       <div class="note" id="rfc.section.9.4.p.9">
    1608          <p> <b>Note:</b> The Content-Location header field (<a href="p3-payload.html#header.content-location" title="Content-Location">Section 6.7</a> of <a href="#Part3" id="rfc.xref.Part3.12"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>) differs from Location in that the Content-Location identifies the most specific resource corresponding to the enclosed representation.
    1609             It is therefore possible for a response to contain header fields for both Location and Content-Location.
    1610          </p>
    1611       </div>
    1612       <div id="rfc.iref.m.9"></div>
    1613       <div id="rfc.iref.h.6"></div>
    1614       <h2 id="rfc.section.9.5"><a href="#rfc.section.9.5">9.5</a>&nbsp;<a id="header.max-forwards" href="#header.max-forwards">Max-Forwards</a></h2>
    1615       <p id="rfc.section.9.5.p.1">The "Max-Forwards" request-header field provides a mechanism with the TRACE (<a href="#TRACE" id="rfc.xref.TRACE.2" title="TRACE">Section&nbsp;7.8</a>) and OPTIONS (<a href="#OPTIONS" id="rfc.xref.OPTIONS.2" title="OPTIONS">Section&nbsp;7.2</a>) methods to limit the number of times that the request is forwarded by proxies or gateways. This can be useful when the client
    1616          is attempting to trace a request which appears to be failing or looping in mid-chain.
    1617       </p>
    1618       <div id="rfc.figure.u.20"></div><pre class="inline"><span id="rfc.iref.g.20"></span><span id="rfc.iref.g.21"></span>  <a href="#header.max-forwards" class="smpl">Max-Forwards</a>   = "Max-Forwards" ":" <a href="#core.rules" class="smpl">OWS</a> <a href="#header.max-forwards" class="smpl">Max-Forwards-v</a>
    1619   <a href="#header.max-forwards" class="smpl">Max-Forwards-v</a> = 1*<a href="#notation" class="smpl">DIGIT</a>
    1620 </pre><p id="rfc.section.9.5.p.3">The Max-Forwards value is a decimal integer indicating the remaining number of times this request message can be forwarded.</p>
    1621       <p id="rfc.section.9.5.p.4">Each proxy or gateway recipient of a TRACE or OPTIONS request containing a Max-Forwards header field <em class="bcp14">MUST</em> check and update its value prior to forwarding the request. If the received value is zero (0), the recipient <em class="bcp14">MUST NOT</em> forward the request; instead, it <em class="bcp14">MUST</em> respond as the final recipient. If the received Max-Forwards value is greater than zero, then the forwarded message <em class="bcp14">MUST</em> contain an updated Max-Forwards field with a value decremented by one (1).
    1622       </p>
    1623       <p id="rfc.section.9.5.p.5">The Max-Forwards header field <em class="bcp14">MAY</em> be ignored for all other methods defined by this specification and for any extension methods for which it is not explicitly
    1624          referred to as part of that method definition.
    1625       </p>
    1626       <div id="rfc.iref.r.1"></div>
    1627       <div id="rfc.iref.h.7"></div>
    1628       <h2 id="rfc.section.9.6"><a href="#rfc.section.9.6">9.6</a>&nbsp;<a id="header.referer" href="#header.referer">Referer</a></h2>
    1629       <p id="rfc.section.9.6.p.1">The "Referer" [sic] request-header field allows the client to specify the URI of the resource from which the effective request
    1630          URI was obtained (the "referrer", although the header field is misspelled.).
    1631       </p>
    1632       <p id="rfc.section.9.6.p.2">The Referer header field allows servers to generate lists of back-links to resources for interest, logging, optimized caching,
    1633          etc. It also allows obsolete or mistyped links to be traced for maintenance. Some servers use Referer as a means of controlling
    1634          where they allow links from (so-called "deep linking"), but legitimate requests do not always contain a Referer header field.
    1635       </p>
    1636       <p id="rfc.section.9.6.p.3">If the effective request URI was obtained from a source that does not have its own URI (e.g., input from the user keyboard),
    1637          the Referer field <em class="bcp14">MUST</em> either be sent with the value "about:blank", or not be sent at all. Note that this requirement does not apply to sources with
    1638          non-HTTP URIs (e.g., FTP).
    1639       </p>
    1640       <div id="rfc.figure.u.21"></div><pre class="inline"><span id="rfc.iref.g.22"></span><span id="rfc.iref.g.23"></span>  <a href="#header.referer" class="smpl">Referer</a>        = "Referer" ":" <a href="#core.rules" class="smpl">OWS</a> <a href="#header.referer" class="smpl">Referer-v</a>
    1641   <a href="#header.referer" class="smpl">Referer-v</a>      = <a href="#abnf.dependencies" class="smpl">absolute-URI</a> / <a href="#abnf.dependencies" class="smpl">partial-URI</a>
    1642 </pre><p id="rfc.section.9.6.p.5">Example:</p>
    1643       <div id="rfc.figure.u.22"></div><pre class="text">  Referer: http://www.example.org/hypertext/Overview.html
    1644 </pre><p id="rfc.section.9.6.p.7">If the field value is a relative URI, it <em class="bcp14">SHOULD</em> be interpreted relative to the effective request URI. The URI <em class="bcp14">MUST NOT</em> include a fragment. See <a href="#encoding.sensitive.information.in.uris" title="Encoding Sensitive Information in URIs">Section&nbsp;11.2</a> for security considerations.
    1645       </p>
    1646       <div id="rfc.iref.r.2"></div>
    1647       <div id="rfc.iref.h.8"></div>
    1648       <h2 id="rfc.section.9.7"><a href="#rfc.section.9.7">9.7</a>&nbsp;<a id="header.retry-after" href="#header.retry-after">Retry-After</a></h2>
    1649       <p id="rfc.section.9.7.p.1">The response-header "Retry-After" field can be used with a 503 (Service Unavailable) response to indicate how long the service
    1650          is expected to be unavailable to the requesting client. This field <em class="bcp14">MAY</em> also be used with any 3xx (Redirection) response to indicate the minimum time the user-agent is asked wait before issuing
    1651          the redirected request.
    1652       </p>
    1653       <p id="rfc.section.9.7.p.2">The value of this field can be either an HTTP-date or an integer number of seconds (in decimal) after the time of the response.</p>
    1654       <div id="rfc.figure.u.23"></div><pre class="inline"><span id="rfc.iref.g.24"></span><span id="rfc.iref.g.25"></span>  <a href="#header.retry-after" class="smpl">Retry-After</a>   = "Retry-After" ":" <a href="#core.rules" class="smpl">OWS</a> <a href="#header.retry-after" class="smpl">Retry-After-v</a>
    1655   <a href="#header.retry-after" class="smpl">Retry-After-v</a> = <a href="#abnf.dependencies" class="smpl">HTTP-date</a> / <a href="#rule.delta-seconds" class="smpl">delta-seconds</a>
    1656 </pre><div id="rule.delta-seconds">
    1657          <p id="rfc.section.9.7.p.4">  Time spans are non-negative decimal integers, representing time in seconds.</p>
    1658       </div>
    1659       <div id="rfc.figure.u.24"></div><pre class="inline"><span id="rfc.iref.g.26"></span>  <a href="#rule.delta-seconds" class="smpl">delta-seconds</a>  = 1*<a href="#notation" class="smpl">DIGIT</a>
    1660 </pre><p id="rfc.section.9.7.p.6">Two examples of its use are</p>
    1661       <div id="rfc.figure.u.25"></div><pre class="text">  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
    1662   Retry-After: 120
    1663 </pre><p id="rfc.section.9.7.p.8">In the latter example, the delay is 2 minutes.</p>
    1664       <div id="rfc.iref.s.43"></div>
    1665       <div id="rfc.iref.h.9"></div>
    1666       <h2 id="rfc.section.9.8"><a href="#rfc.section.9.8">9.8</a>&nbsp;<a id="header.server" href="#header.server">Server</a></h2>
    1667       <p id="rfc.section.9.8.p.1">The "Server" response-header field contains information about the software used by the origin server to handle the request.</p>
    1668       <p id="rfc.section.9.8.p.2">The field can contain multiple product tokens (<a href="p1-messaging.html#product.tokens" title="Product Tokens">Section 6.3</a> of <a href="#Part1" id="rfc.xref.Part1.29"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) and comments (<a href="p1-messaging.html#header.fields" title="Header Fields">Section 3.2</a> of <a href="#Part1" id="rfc.xref.Part1.30"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) identifying the server and any significant subproducts. The product tokens are listed in order of their significance for
    1669          identifying the application.
    1670       </p>
    1671       <div id="rfc.figure.u.26"></div><pre class="inline"><span id="rfc.iref.g.27"></span><span id="rfc.iref.g.28"></span>  <a href="#header.server" class="smpl">Server</a>         = "Server" ":" <a href="#core.rules" class="smpl">OWS</a> <a href="#header.server" class="smpl">Server-v</a>
    1672   <a href="#header.server" class="smpl">Server-v</a>       = <a href="#abnf.dependencies" class="smpl">product</a>
    1673                    *( <a href="#core.rules" class="smpl">RWS</a> ( <a href="#abnf.dependencies" class="smpl">product</a> / <a href="#abnf.dependencies" class="smpl">comment</a> ) )
    1674 </pre><p id="rfc.section.9.8.p.4">Example:</p>
    1675       <div id="rfc.figure.u.27"></div><pre class="text">  Server: CERN/3.0 libwww/2.17
    1676 </pre><p id="rfc.section.9.8.p.6">If the response is being forwarded through a proxy, the proxy application <em class="bcp14">MUST NOT</em> modify the Server response-header field. Instead, it <em class="bcp14">MUST</em> include a Via field (as described in <a href="p1-messaging.html#header.via" title="Via">Section 9.9</a> of <a href="#Part1" id="rfc.xref.Part1.31"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>).
    1677       </p>
    1678       <div class="note" id="rfc.section.9.8.p.7">
    1679          <p> <b>Note:</b> Revealing the specific software version of the server might allow the server machine to become more vulnerable to attacks
    1680             against software that is known to contain security holes. Server implementors are encouraged to make this field a configurable
    1681             option.
    1682          </p>
    1683       </div>
    1684       <div id="rfc.iref.u.1"></div>
    1685       <div id="rfc.iref.h.10"></div>
    1686       <h2 id="rfc.section.9.9"><a href="#rfc.section.9.9">9.9</a>&nbsp;<a id="header.user-agent" href="#header.user-agent">User-Agent</a></h2>
    1687       <p id="rfc.section.9.9.p.1">The "User-Agent" request-header field contains information about the user agent originating the request. This is for statistical
    1688          purposes, the tracing of protocol violations, and automated recognition of user agents for the sake of tailoring responses
    1689          to avoid particular user agent limitations.
    1690       </p>
    1691       <p id="rfc.section.9.9.p.2">User agents <em class="bcp14">SHOULD</em> include this field with requests. The field can contain multiple product tokens (<a href="p1-messaging.html#product.tokens" title="Product Tokens">Section 6.3</a> of <a href="#Part1" id="rfc.xref.Part1.32"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) and comments (<a href="p1-messaging.html#header.fields" title="Header Fields">Section 3.2</a> of <a href="#Part1" id="rfc.xref.Part1.33"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) identifying the agent and any subproducts which form a significant part of the user agent. By convention, the product tokens
    1692          are listed in order of their significance for identifying the application.
    1693       </p>
    1694       <div id="rfc.figure.u.28"></div><pre class="inline"><span id="rfc.iref.g.29"></span><span id="rfc.iref.g.30"></span>  <a href="#header.user-agent" class="smpl">User-Agent</a>     = "User-Agent" ":" <a href="#core.rules" class="smpl">OWS</a> <a href="#header.user-agent" class="smpl">User-Agent-v</a>
    1695   <a href="#header.user-agent" class="smpl">User-Agent-v</a>   = <a href="#abnf.dependencies" class="smpl">product</a>
    1696                    *( <a href="#core.rules" class="smpl">RWS</a> ( <a href="#abnf.dependencies" class="smpl">product</a> / <a href="#abnf.dependencies" class="smpl">comment</a> ) )
    1697 </pre><p id="rfc.section.9.9.p.4">Example:</p>
    1698       <div id="rfc.figure.u.29"></div><pre class="text">  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
    1699 </pre><h1 id="rfc.section.10"><a href="#rfc.section.10">10.</a>&nbsp;<a id="IANA.considerations" href="#IANA.considerations">IANA Considerations</a></h1>
    1700       <h2 id="rfc.section.10.1"><a href="#rfc.section.10.1">10.1</a>&nbsp;<a id="method.registration" href="#method.registration">Method Registry</a></h2>
    1701       <p id="rfc.section.10.1.p.1">The registration procedure for HTTP Methods is defined by <a href="#method.registry" title="Method Registry">Section&nbsp;2.1</a> of this document.
    1702       </p>
    1703       <p id="rfc.section.10.1.p.2">The HTTP Method Registry shall be created at &lt;<a href="http://www.iana.org/assignments/http-methods">http://www.iana.org/assignments/http-methods</a>&gt; and be populated with the registrations below:
    1704       </p>
    1705       <div id="rfc.table.1">
    1706          <div id="iana.method.registration.table"></div>
    1707          <table class="tt full left" cellpadding="3" cellspacing="0">
    1708             <thead>
    1709                <tr>
    1710                   <th>Method</th>
    1711                   <th>Safe</th>
    1712                   <th>Reference</th>
    1713                </tr>
    1714             </thead>
    1715             <tbody>
    1716                <tr>
    1717                   <td class="left">CONNECT</td>
    1718                   <td class="left">no</td>
    1719                   <td class="left"> <a href="#CONNECT" id="rfc.xref.CONNECT.2" title="CONNECT">Section&nbsp;7.9</a>
    1720                   </td>
    1721                </tr>
    1722                <tr>
    1723                   <td class="left">DELETE</td>
    1724                   <td class="left">no</td>
    1725                   <td class="left"> <a href="#DELETE" id="rfc.xref.DELETE.2" title="DELETE">Section&nbsp;7.7</a>
    1726                   </td>
    1727                </tr>
    1728                <tr>
    1729                   <td class="left">GET</td>
    1730                   <td class="left">yes</td>
    1731                   <td class="left"> <a href="#GET" id="rfc.xref.GET.2" title="GET">Section&nbsp;7.3</a>
    1732                   </td>
    1733                </tr>
    1734                <tr>
    1735                   <td class="left">HEAD</td>
    1736                   <td class="left">yes</td>
    1737                   <td class="left"> <a href="#HEAD" id="rfc.xref.HEAD.2" title="HEAD">Section&nbsp;7.4</a>
    1738                   </td>
    1739                </tr>
    1740                <tr>
    1741                   <td class="left">OPTIONS</td>
    1742                   <td class="left">yes</td>
    1743                   <td class="left"> <a href="#OPTIONS" id="rfc.xref.OPTIONS.3" title="OPTIONS">Section&nbsp;7.2</a>
    1744                   </td>
    1745                </tr>
    1746                <tr>
    1747                   <td class="left">POST</td>
    1748                   <td class="left">no</td>
    1749                   <td class="left"> <a href="#POST" id="rfc.xref.POST.2" title="POST">Section&nbsp;7.5</a>
    1750                   </td>
    1751                </tr>
    1752                <tr>
    1753                   <td class="left">PUT</td>
    1754                   <td class="left">no</td>
    1755                   <td class="left"> <a href="#PUT" id="rfc.xref.PUT.2" title="PUT">Section&nbsp;7.6</a>
    1756                   </td>
    1757                </tr>
    1758                <tr>
    1759                   <td class="left">TRACE</td>
    1760                   <td class="left">yes</td>
    1761                   <td class="left"> <a href="#TRACE" id="rfc.xref.TRACE.3" title="TRACE">Section&nbsp;7.8</a>
    1762                   </td>
    1763                </tr>
    1764             </tbody>
    1765          </table>
    1766       </div>
    1767       <h2 id="rfc.section.10.2"><a href="#rfc.section.10.2">10.2</a>&nbsp;<a id="status.code.registration" href="#status.code.registration">Status Code Registry</a></h2>
    1768       <p id="rfc.section.10.2.p.1">The registration procedure for HTTP Status Codes -- previously defined in <a href="http://tools.ietf.org/html/rfc2817#section-7.1">Section 7.1</a> of <a href="#RFC2817" id="rfc.xref.RFC2817.2"><cite title="Upgrading to TLS Within HTTP/1.1">[RFC2817]</cite></a> -- is now defined by <a href="#status.code.registry" title="Status Code Registry">Section&nbsp;4.1</a> of this document.
    1769       </p>
    1770       <p id="rfc.section.10.2.p.2">The HTTP Status Code Registry located at &lt;<a href="http://www.iana.org/assignments/http-status-codes">http://www.iana.org/assignments/http-status-codes</a>&gt; shall be updated with the registrations below:
    1771       </p>
    1772       <div id="rfc.table.2">
    1773          <div id="iana.status.code.registration.table"></div>
    1774          <table class="tt full left" cellpadding="3" cellspacing="0">
    1775             <thead>
    1776                <tr>
    1777                   <th>Value</th>
    1778                   <th>Description</th>
    1779                   <th>Reference</th>
    1780                </tr>
    1781             </thead>
    1782             <tbody>
    1783                <tr>
    1784                   <td class="left">100</td>
    1785                   <td class="left">Continue</td>
    1786                   <td class="left"> <a href="#status.100" id="rfc.xref.status.100.2" title="100 Continue">Section&nbsp;8.1.1</a>
    1787                   </td>
    1788                </tr>
    1789                <tr>
    1790                   <td class="left">101</td>
    1791                   <td class="left">Switching Protocols</td>
    1792                   <td class="left"> <a href="#status.101" id="rfc.xref.status.101.2" title="101 Switching Protocols">Section&nbsp;8.1.2</a>
    1793                   </td>
    1794                </tr>
    1795                <tr>
    1796                   <td class="left">200</td>
    1797                   <td class="left">OK</td>
    1798                   <td class="left"> <a href="#status.200" id="rfc.xref.status.200.2" title="200 OK">Section&nbsp;8.2.1</a>
    1799                   </td>
    1800                </tr>
    1801                <tr>
    1802                   <td class="left">201</td>
    1803                   <td class="left">Created</td>
    1804                   <td class="left"> <a href="#status.201" id="rfc.xref.status.201.2" title="201 Created">Section&nbsp;8.2.2</a>
    1805                   </td>
    1806                </tr>
    1807                <tr>
    1808                   <td class="left">202</td>
    1809                   <td class="left">Accepted</td>
    1810                   <td class="left"> <a href="#status.202" id="rfc.xref.status.202.2" title="202 Accepted">Section&nbsp;8.2.3</a>
    1811                   </td>
    1812                </tr>
    1813                <tr>
    1814                   <td class="left">203</td>
    1815                   <td class="left">Non-Authoritative Information</td>
    1816                   <td class="left"> <a href="#status.203" id="rfc.xref.status.203.2" title="203 Non-Authoritative Information">Section&nbsp;8.2.4</a>
    1817                   </td>
    1818                </tr>
    1819                <tr>
    1820                   <td class="left">204</td>
    1821                   <td class="left">No Content</td>
    1822                   <td class="left"> <a href="#status.204" id="rfc.xref.status.204.2" title="204 No Content">Section&nbsp;8.2.5</a>
    1823                   </td>
    1824                </tr>
    1825                <tr>
    1826                   <td class="left">205</td>
    1827                   <td class="left">Reset Content</td>
    1828                   <td class="left"> <a href="#status.205" id="rfc.xref.status.205.2" title="205 Reset Content">Section&nbsp;8.2.6</a>
    1829                   </td>
    1830                </tr>
    1831                <tr>
    1832                   <td class="left">300</td>
    1833                   <td class="left">Multiple Choices</td>
    1834                   <td class="left"> <a href="#status.300" id="rfc.xref.status.300.2" title="300 Multiple Choices">Section&nbsp;8.3.1</a>
    1835                   </td>
    1836                </tr>
    1837                <tr>
    1838                   <td class="left">301</td>
    1839                   <td class="left">Moved Permanently</td>
    1840                   <td class="left"> <a href="#status.301" id="rfc.xref.status.301.2" title="301 Moved Permanently">Section&nbsp;8.3.2</a>
    1841                   </td>
    1842                </tr>
    1843                <tr>
    1844                   <td class="left">302</td>
    1845                   <td class="left">Found</td>
    1846                   <td class="left"> <a href="#status.302" id="rfc.xref.status.302.2" title="302 Found">Section&nbsp;8.3.3</a>
    1847                   </td>
    1848                </tr>
    1849                <tr>
    1850                   <td class="left">303</td>
    1851                   <td class="left">See Other</td>
    1852                   <td class="left"> <a href="#status.303" id="rfc.xref.status.303.3" title="303 See Other">Section&nbsp;8.3.4</a>
    1853                   </td>
    1854                </tr>
    1855                <tr>
    1856                   <td class="left">305</td>
    1857                   <td class="left">Use Proxy</td>
    1858                   <td class="left"> <a href="#status.305" id="rfc.xref.status.305.2" title="305 Use Proxy">Section&nbsp;8.3.6</a>
    1859                   </td>
    1860                </tr>
    1861                <tr>
    1862                   <td class="left">306</td>
    1863                   <td class="left">(Unused)</td>
    1864                   <td class="left"> <a href="#status.306" id="rfc.xref.status.306.1" title="306 (Unused)">Section&nbsp;8.3.7</a>
    1865                   </td>
    1866                </tr>
    1867                <tr>
    1868                   <td class="left">307</td>
    1869                   <td class="left">Temporary Redirect</td>
    1870                   <td class="left"> <a href="#status.307" id="rfc.xref.status.307.3" title="307 Temporary Redirect">Section&nbsp;8.3.8</a>
    1871                   </td>
    1872                </tr>
    1873                <tr>
    1874                   <td class="left">400</td>
    1875                   <td class="left">Bad Request</td>
    1876                   <td class="left"> <a href="#status.400" id="rfc.xref.status.400.2" title="400 Bad Request">Section&nbsp;8.4.1</a>
    1877                   </td>
    1878                </tr>
    1879                <tr>
    1880                   <td class="left">402</td>
    1881                   <td class="left">Payment Required</td>
    1882                   <td class="left"> <a href="#status.402" id="rfc.xref.status.402.2" title="402 Payment Required">Section&nbsp;8.4.3</a>
    1883                   </td>
    1884                </tr>
    1885                <tr>
    1886                   <td class="left">403</td>
    1887                   <td class="left">Forbidden</td>
    1888                   <td class="left"> <a href="#status.403" id="rfc.xref.status.403.2" title="403 Forbidden">Section&nbsp;8.4.4</a>
    1889                   </td>
    1890                </tr>
    1891                <tr>
    1892                   <td class="left">404</td>
    1893                   <td class="left">Not Found</td>
    1894                   <td class="left"> <a href="#status.404" id="rfc.xref.status.404.2" title="404 Not Found">Section&nbsp;8.4.5</a>
    1895                   </td>
    1896                </tr>
    1897                <tr>
    1898                   <td class="left">405</td>
    1899                   <td class="left">Method Not Allowed</td>
    1900                   <td class="left"> <a href="#status.405" id="rfc.xref.status.405.2" title="405 Method Not Allowed">Section&nbsp;8.4.6</a>
    1901                   </td>
    1902                </tr>
    1903                <tr>
    1904                   <td class="left">406</td>
    1905                   <td class="left">Not Acceptable</td>
    1906                   <td class="left"> <a href="#status.406" id="rfc.xref.status.406.2" title="406 Not Acceptable">Section&nbsp;8.4.7</a>
    1907                   </td>
    1908                </tr>
    1909                <tr>
    1910                   <td class="left">407</td>
    1911                   <td class="left">Proxy Authentication Required</td>
    1912                   <td class="left"> <a href="#status.407" id="rfc.xref.status.407.1" title="407 Proxy Authentication Required">Section&nbsp;8.4.8</a>
    1913                   </td>
    1914                </tr>
    1915                <tr>
    1916                   <td class="left">408</td>
    1917                   <td class="left">Request Timeout</td>
    1918                   <td class="left"> <a href="#status.408" id="rfc.xref.status.408.2" title="408 Request Timeout">Section&nbsp;8.4.9</a>
    1919                   </td>
    1920                </tr>
    1921                <tr>
    1922                   <td class="left">409</td>
    1923                   <td class="left">Conflict</td>
    1924                   <td class="left"> <a href="#status.409" id="rfc.xref.status.409.2" title="409 Conflict">Section&nbsp;8.4.10</a>
    1925                   </td>
    1926                </tr>
    1927                <tr>
    1928                   <td class="left">410</td>
    1929                   <td class="left">Gone</td>
    1930                   <td class="left"> <a href="#status.410" id="rfc.xref.status.410.2" title="410 Gone">Section&nbsp;8.4.11</a>
    1931                   </td>
    1932                </tr>
    1933                <tr>
    1934                   <td class="left">411</td>
    1935                   <td class="left">Length Required</td>
    1936                   <td class="left"> <a href="#status.411" id="rfc.xref.status.411.2" title="411 Length Required">Section&nbsp;8.4.12</a>
    1937                   </td>
    1938                </tr>
    1939                <tr>
    1940                   <td class="left">413</td>
    1941                   <td class="left">Request Entity Too Large</td>
    1942                   <td class="left"> <a href="#status.413" id="rfc.xref.status.413.2" title="413 Request Entity Too Large">Section&nbsp;8.4.14</a>
    1943                   </td>
    1944                </tr>
    1945                <tr>
    1946                   <td class="left">414</td>
    1947                   <td class="left">URI Too Long</td>
    1948                   <td class="left"> <a href="#status.414" id="rfc.xref.status.414.2" title="414 URI Too Long">Section&nbsp;8.4.15</a>
    1949                   </td>
    1950                </tr>
    1951                <tr>
    1952                   <td class="left">415</td>
    1953                   <td class="left">Unsupported Media Type</td>
    1954                   <td class="left"> <a href="#status.415" id="rfc.xref.status.415.2" title="415 Unsupported Media Type">Section&nbsp;8.4.16</a>
    1955                   </td>
    1956                </tr>
    1957                <tr>
    1958                   <td class="left">417</td>
    1959                   <td class="left">Expectation Failed</td>
    1960                   <td class="left"> <a href="#status.417" id="rfc.xref.status.417.2" title="417 Expectation Failed">Section&nbsp;8.4.18</a>
    1961                   </td>
    1962                </tr>
    1963                <tr>
    1964                   <td class="left">500</td>
    1965                   <td class="left">Internal Server Error</td>
    1966                   <td class="left"> <a href="#status.500" id="rfc.xref.status.500.2" title="500 Internal Server Error">Section&nbsp;8.5.1</a>
    1967                   </td>
    1968                </tr>
    1969                <tr>
    1970                   <td class="left">501</td>
    1971                   <td class="left">Not Implemented</td>
    1972                   <td class="left"> <a href="#status.501" id="rfc.xref.status.501.2" title="501 Not Implemented">Section&nbsp;8.5.2</a>
    1973                   </td>
    1974                </tr>
    1975                <tr>
    1976                   <td class="left">502</td>
    1977                   <td class="left">Bad Gateway</td>
    1978                   <td class="left"> <a href="#status.502" id="rfc.xref.status.502.2" title="502 Bad Gateway">Section&nbsp;8.5.3</a>
    1979                   </td>
    1980                </tr>
    1981                <tr>
    1982                   <td class="left">503</td>
    1983                   <td class="left">Service Unavailable</td>
    1984                   <td class="left"> <a href="#status.503" id="rfc.xref.status.503.2" title="503 Service Unavailable">Section&nbsp;8.5.4</a>
    1985                   </td>
    1986                </tr>
    1987                <tr>
    1988                   <td class="left">504</td>
    1989                   <td class="left">Gateway Timeout</td>
    1990                   <td class="left"> <a href="#status.504" id="rfc.xref.status.504.2" title="504 Gateway Timeout">Section&nbsp;8.5.5</a>
    1991                   </td>
    1992                </tr>
    1993                <tr>
    1994                   <td class="left">505</td>
    1995                   <td class="left">HTTP Version Not Supported</td>
    1996                   <td class="left"> <a href="#status.505" id="rfc.xref.status.505.2" title="505 HTTP Version Not Supported">Section&nbsp;8.5.6</a>
    1997                   </td>
    1998                </tr>
    1999             </tbody>
    2000          </table>
    2001       </div>
    2002       <h2 id="rfc.section.10.3"><a href="#rfc.section.10.3">10.3</a>&nbsp;<a id="header.field.registration" href="#header.field.registration">Header Field Registration</a></h2>
    2003       <p id="rfc.section.10.3.p.1">The Message Header Field 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; shall 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>):
    2004       </p>
    2005       <div id="rfc.table.3">
    2006          <div id="iana.header.registration.table"></div>
    2007          <table class="tt full left" cellpadding="3" cellspacing="0">
    2008             <thead>
    2009                <tr>
    2010                   <th>Header Field Name</th>
    2011                   <th>Protocol</th>
    2012                   <th>Status</th>
    2013                   <th>Reference</th>
    2014                </tr>
    2015             </thead>
    2016             <tbody>
    2017                <tr>
    2018                   <td class="left">Allow</td>
    2019                   <td class="left">http</td>
    2020                   <td class="left">standard</td>
    2021                   <td class="left"> <a href="#header.allow" id="rfc.xref.header.allow.3" title="Allow">Section&nbsp;9.1</a>
    2022                   </td>
    2023                </tr>
    2024                <tr>
    2025                   <td class="left">Expect</td>
    2026                   <td class="left">http</td>
    2027                   <td class="left">standard</td>
    2028                   <td class="left"> <a href="#header.expect" id="rfc.xref.header.expect.3" title="Expect">Section&nbsp;9.2</a>
    2029                   </td>
    2030                </tr>
    2031                <tr>
    2032                   <td class="left">From</td>
    2033                   <td class="left">http</td>
    2034                   <td class="left">standard</td>
    2035                   <td class="left"> <a href="#header.from" id="rfc.xref.header.from.2" title="From">Section&nbsp;9.3</a>
    2036                   </td>
    2037                </tr>
    2038                <tr>
    2039                   <td class="left">Location</td>
    2040                   <td class="left">http</td>
    2041                   <td class="left">standard</td>
    2042                   <td class="left"> <a href="#header.location" id="rfc.xref.header.location.3" title="Location">Section&nbsp;9.4</a>
    2043                   </td>
    2044                </tr>
    2045                <tr>
    2046                   <td class="left">Max-Forwards</td>
    2047                   <td class="left">http</td>
    2048                   <td class="left">standard</td>
    2049                   <td class="left"> <a href="#header.max-forwards" id="rfc.xref.header.max-forwards.4" title="Max-Forwards">Section&nbsp;9.5</a>
    2050                   </td>
    2051                </tr>
    2052                <tr>
    2053                   <td class="left">Referer</td>
    2054                   <td class="left">http</td>
    2055                   <td class="left">standard</td>
    2056                   <td class="left"> <a href="#header.referer" id="rfc.xref.header.referer.2" title="Referer">Section&nbsp;9.6</a>
    2057                   </td>
    2058                </tr>
    2059                <tr>
    2060                   <td class="left">Retry-After</td>
    2061                   <td class="left">http</td>
    2062                   <td class="left">standard</td>
    2063                   <td class="left"> <a href="#header.retry-after" id="rfc.xref.header.retry-after.2" title="Retry-After">Section&nbsp;9.7</a>
    2064                   </td>
    2065                </tr>
    2066                <tr>
    2067                   <td class="left">Server</td>
    2068                   <td class="left">http</td>
    2069                   <td class="left">standard</td>
    2070                   <td class="left"> <a href="#header.server" id="rfc.xref.header.server.2" title="Server">Section&nbsp;9.8</a>
    2071                   </td>
    2072                </tr>
    2073                <tr>
    2074                   <td class="left">User-Agent</td>
    2075                   <td class="left">http</td>
    2076                   <td class="left">standard</td>
    2077                   <td class="left"> <a href="#header.user-agent" id="rfc.xref.header.user-agent.2" title="User-Agent">Section&nbsp;9.9</a>
    2078                   </td>
    2079                </tr>
    2080             </tbody>
    2081          </table>
    2082       </div>
    2083       <p id="rfc.section.10.3.p.2">The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".</p>
    2084       <h1 id="rfc.section.11"><a href="#rfc.section.11">11.</a>&nbsp;<a id="security.considerations" href="#security.considerations">Security Considerations</a></h1>
    2085       <p id="rfc.section.11.p.1">This section is meant to inform application developers, information providers, and users of the security limitations in HTTP/1.1
    2086          as described by this document. The discussion does not include definitive solutions to the problems revealed, though it does
    2087          make some suggestions for reducing security risks.
    2088       </p>
    2089       <h2 id="rfc.section.11.1"><a href="#rfc.section.11.1">11.1</a>&nbsp;<a id="security.sensitive" href="#security.sensitive">Transfer of Sensitive Information</a></h2>
    2090       <p id="rfc.section.11.1.p.1">Like any generic data transfer protocol, HTTP cannot regulate the content of the data that is transferred, nor is there any
    2091          a priori method of determining the sensitivity of any particular piece of information within the context of any given request.
    2092          Therefore, applications <em class="bcp14">SHOULD</em> supply as much control over this information as possible to the provider of that information. Four header fields are worth
    2093          special mention in this context: Server, Via, Referer and From.
    2094       </p>
    2095       <p id="rfc.section.11.1.p.2">Revealing the specific software version of the server might allow the server machine to become more vulnerable to attacks
    2096          against software that is known to contain security holes. Implementors <em class="bcp14">SHOULD</em> make the Server header field a configurable option.
    2097       </p>
    2098       <p id="rfc.section.11.1.p.3">Proxies which serve as a portal through a network firewall <em class="bcp14">SHOULD</em> take special precautions regarding the transfer of header information that identifies the hosts behind the firewall. In particular,
    2099          they <em class="bcp14">SHOULD</em> remove, or replace with sanitized versions, any Via fields generated behind the firewall.
    2100       </p>
    2101       <p id="rfc.section.11.1.p.4">The Referer header field allows reading patterns to be studied and reverse links drawn. Although it can be very useful, its
    2102          power can be abused if user details are not separated from the information contained in the Referer. Even when the personal
    2103          information has been removed, the Referer header field might indicate a private document's URI whose publication would be
    2104          inappropriate.
    2105       </p>
    2106       <p id="rfc.section.11.1.p.5">The information sent in the From field might conflict with the user's privacy interests or their site's security policy, and
    2107          hence it <em class="bcp14">SHOULD NOT</em> be transmitted without the user being able to disable, enable, and modify the contents of the field. The user <em class="bcp14">MUST</em> be able to set the contents of this field within a user preference or application defaults configuration.
    2108       </p>
    2109       <p id="rfc.section.11.1.p.6">We suggest, though do not require, that a convenient toggle interface be provided for the user to enable or disable the sending
    2110          of From and Referer information.
    2111       </p>
    2112       <p id="rfc.section.11.1.p.7">The User-Agent (<a href="#header.user-agent" id="rfc.xref.header.user-agent.3" title="User-Agent">Section&nbsp;9.9</a>) or Server (<a href="#header.server" id="rfc.xref.header.server.3" title="Server">Section&nbsp;9.8</a>) header fields can sometimes be used to determine that a specific client or server have a particular security hole which
    2113          might be exploited. Unfortunately, this same information is often used for other valuable purposes for which HTTP currently
    2114          has no better mechanism.
    2115       </p>
    2116       <p id="rfc.section.11.1.p.8">Some methods, like TRACE (<a href="#TRACE" id="rfc.xref.TRACE.4" title="TRACE">Section&nbsp;7.8</a>), expose information that was sent in request header fields within the body of their response. Clients <em class="bcp14">SHOULD</em> be careful with sensitive information, like Cookies, Authorization credentials and other header fields that might be used
    2117          to collect data from the client.
    2118       </p>
    2119       <h2 id="rfc.section.11.2"><a href="#rfc.section.11.2">11.2</a>&nbsp;<a id="encoding.sensitive.information.in.uris" href="#encoding.sensitive.information.in.uris">Encoding Sensitive Information in URIs</a></h2>
    2120       <p id="rfc.section.11.2.p.1">Because the source of a link might be private information or might reveal an otherwise private information source, it is strongly
    2121          recommended that the user be able to select whether or not the Referer field is sent. For example, a browser client could
    2122          have a toggle switch for browsing openly/anonymously, which would respectively enable/disable the sending of Referer and From
    2123          information.
    2124       </p>
    2125       <p id="rfc.section.11.2.p.2">Clients <em class="bcp14">SHOULD NOT</em> include a Referer header field in a (non-secure) HTTP request if the referring page was transferred with a secure protocol.
    2126       </p>
    2127       <p id="rfc.section.11.2.p.3">Authors of services <em class="bcp14">SHOULD NOT</em> use GET-based forms for the submission of sensitive data because that data will be placed in the request-target. Many existing
    2128          servers, proxies, and user agents log or display the request-target in places where it might be visible to third parties.
    2129          Such services can use POST-based form submission instead.
    2130       </p>
    2131       <h2 id="rfc.section.11.3"><a href="#rfc.section.11.3">11.3</a>&nbsp;<a id="location.spoofing" href="#location.spoofing">Location Headers and Spoofing</a></h2>
    2132       <p id="rfc.section.11.3.p.1">If a single server supports multiple organizations that do not trust one another, then it <em class="bcp14">MUST</em> check the values of Location and Content-Location header fields in responses that are generated under control of said organizations
    2133          to make sure that they do not attempt to invalidate resources over which they have no authority.
    2134       </p>
    2135       <h1 id="rfc.section.12"><a href="#rfc.section.12">12.</a>&nbsp;<a id="ack" href="#ack">Acknowledgments</a></h1>
    2136       <h1 id="rfc.references"><a id="rfc.section.13" href="#rfc.section.13">13.</a> References
    2137       </h1>
    2138       <h2 id="rfc.references.1"><a href="#rfc.section.13.1" id="rfc.section.13.1">13.1</a> Normative References
    2139       </h2>
    2140       <table>                 
    2141          <tr>
    2142             <td class="reference"><b id="Part1">[Part1]</b></td>
    2143             <td class="top"><a href="mailto:fielding@gbiv.com" title="Day Software">Fielding, R., Ed.</a>, <a href="mailto:jg@freedesktop.org" title="Alcatel-Lucent Bell Labs">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-p1-messaging-latest">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</a>”, Internet-Draft&nbsp;draft-ietf-httpbis-p1-messaging-latest (work in progress), October&nbsp;2010.
    2144             </td>
    2145          </tr>
    2146          <tr>
    2147             <td class="reference"><b id="Part3">[Part3]</b></td>
    2148             <td class="top"><a href="mailto:fielding@gbiv.com" title="Day Software">Fielding, R., Ed.</a>, <a href="mailto:jg@freedesktop.org" title="Alcatel-Lucent Bell Labs">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-latest">HTTP/1.1, part 3: Message Payload and Content Negotiation</a>”, Internet-Draft&nbsp;draft-ietf-httpbis-p3-payload-latest (work in progress), October&nbsp;2010.
    2149             </td>
    2150          </tr>
    2151          <tr>
    2152             <td class="reference"><b id="Part4">[Part4]</b></td>
    2153             <td class="top"><a href="mailto:fielding@gbiv.com" title="Day Software">Fielding, R., Ed.</a>, <a href="mailto:jg@freedesktop.org" title="Alcatel-Lucent Bell Labs">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-p4-conditional-latest">HTTP/1.1, part 4: Conditional Requests</a>”, Internet-Draft&nbsp;draft-ietf-httpbis-p4-conditional-latest (work in progress), October&nbsp;2010.
    2154             </td>
    2155          </tr>
    2156          <tr>
    2157             <td class="reference"><b id="Part5">[Part5]</b></td>
    2158             <td class="top"><a href="mailto:fielding@gbiv.com" title="Day Software">Fielding, R., Ed.</a>, <a href="mailto:jg@freedesktop.org" title="Alcatel-Lucent Bell Labs">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-latest">HTTP/1.1, part 5: Range Requests and Partial Responses</a>”, Internet-Draft&nbsp;draft-ietf-httpbis-p5-range-latest (work in progress), October&nbsp;2010.
    2159             </td>
    2160          </tr>
    2161          <tr>
    2162             <td class="reference"><b id="Part6">[Part6]</b></td>
    2163             <td class="top"><a href="mailto:fielding@gbiv.com" title="Day Software">Fielding, R., Ed.</a>, <a href="mailto:jg@freedesktop.org" title="Alcatel-Lucent Bell Labs">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>, <a href="mailto:mnot@mnot.net">Nottingham, M., 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-latest">HTTP/1.1, part 6: Caching</a>”, Internet-Draft&nbsp;draft-ietf-httpbis-p6-cache-latest (work in progress), October&nbsp;2010.
    2164             </td>
    2165          </tr>
    2166          <tr>
    2167             <td class="reference"><b id="Part7">[Part7]</b></td>
    2168             <td class="top"><a href="mailto:fielding@gbiv.com" title="Day Software">Fielding, R., Ed.</a>, <a href="mailto:jg@freedesktop.org" title="Alcatel-Lucent Bell Labs">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-p7-auth-latest">HTTP/1.1, part 7: Authentication</a>”, Internet-Draft&nbsp;draft-ietf-httpbis-p7-auth-latest (work in progress), October&nbsp;2010.
    2169             </td>
    2170          </tr>
    2171          <tr>
    2172             <td class="reference"><b id="RFC2119">[RFC2119]</b></td>
    2173             <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.
    2174             </td>
    2175          </tr>
    2176          <tr>
    2177             <td class="reference"><b id="RFC3986">[RFC3986]</b></td>
    2178             <td class="top"><a href="mailto:timbl@w3.org" title="World Wide Web Consortium">Berners-Lee, T.</a>, <a href="mailto:fielding@gbiv.com" title="Day Software">Fielding, R.</a>, and <a href="mailto:LMM@acm.org" title="Adobe Systems Incorporated">L. Masinter</a>, “<a href="http://tools.ietf.org/html/rfc3986">Uniform Resource Identifier (URI): Generic Syntax</a>”, STD&nbsp;66, RFC&nbsp;3986, January&nbsp;2005.
    2179             </td>
    2180          </tr>
    2181          <tr>
    2182             <td class="reference"><b id="RFC5234">[RFC5234]</b></td>
    2183             <td class="top"><a href="mailto:dcrocker@bbiw.net" title="Brandenburg InternetWorking">Crocker, D., Ed.</a> and <a href="mailto:paul.overell@thus.net" title="THUS plc.">P. Overell</a>, “<a href="http://tools.ietf.org/html/rfc5234">Augmented BNF for Syntax Specifications: ABNF</a>”, STD&nbsp;68, RFC&nbsp;5234, January&nbsp;2008.
    2184             </td>
    2185          </tr>
    2186       </table>
    2187       <h2 id="rfc.references.2"><a href="#rfc.section.13.2" id="rfc.section.13.2">13.2</a> Informative References
    2188       </h2>
    2189       <table>             
    2190          <tr>
    2191             <td class="reference"><b id="RFC1945">[RFC1945]</b></td>
    2192             <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.
    2193             </td>
    2194          </tr>
    2195          <tr>
    2196             <td class="reference"><b id="RFC2068">[RFC2068]</b></td>
    2197             <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.
    2198             </td>
    2199          </tr>
    2200          <tr>
    2201             <td class="reference"><b id="RFC2616">[RFC2616]</b></td>
    2202             <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.
    2203             </td>
    2204          </tr>
    2205          <tr>
    2206             <td class="reference"><b id="RFC2817">[RFC2817]</b></td>
    2207             <td class="top"><a href="mailto:rohit@4K-associates.com" title="4K Associates / UC Irvine">Khare, R.</a> and <a href="mailto:lawrence@agranat.com" title="Agranat Systems, Inc.">S. Lawrence</a>, “<a href="http://tools.ietf.org/html/rfc2817">Upgrading to TLS Within HTTP/1.1</a>”, RFC&nbsp;2817, May&nbsp;2000.
    2208             </td>
    2209          </tr>
    2210          <tr>
    2211             <td class="reference"><b id="RFC3864">[RFC3864]</b></td>
    2212             <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.
    2213             </td>
    2214          </tr>
    2215          <tr>
    2216             <td class="reference"><b id="RFC5226">[RFC5226]</b></td>
    2217             <td class="top"><a href="mailto:narten@us.ibm.com" title="IBM">Narten, T.</a> and <a href="mailto:Harald@Alvestrand.no" title="Google">H. Alvestrand</a>, “<a href="http://tools.ietf.org/html/rfc5226">Guidelines for Writing an IANA Considerations Section in RFCs</a>”, BCP&nbsp;26, RFC&nbsp;5226, May&nbsp;2008.
    2218             </td>
    2219          </tr>
    2220          <tr>
    2221             <td class="reference"><b id="RFC5322">[RFC5322]</b></td>
    2222             <td class="top">Resnick, P., “<a href="http://tools.ietf.org/html/rfc5322">Internet Message Format</a>”, RFC&nbsp;5322, October&nbsp;2008.
    2223             </td>
    2224          </tr>
    2225       </table>
    2226       <div class="avoidbreak">
    2227          <h1 id="rfc.authors"><a href="#rfc.authors">Authors' Addresses</a></h1>
    2228          <address class="vcard"><span class="vcardline"><span class="fn">Roy T. Fielding</span>
    2229                (editor)
    2230                <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>
    2231          <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">Alcatel-Lucent Bell Labs</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@freedesktop.org"><span class="email">jg@freedesktop.org</span></a></span><span class="vcardline">URI: <a href="http://gettys.wordpress.com/" class="url">http://gettys.wordpress.com/</a></span></address>
    2232          <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>
    2233          <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>
    2234          <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>
    2235          <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>
    2236          <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>
    2237          <address class="vcard"><span class="vcardline"><span class="fn">Yves Lafon</span>
    2238                (editor)
    2239                <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>
    2240          <address class="vcard"><span class="vcardline"><span class="fn">Julian F. Reschke</span>
    2241                (editor)
    2242                <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>
    2243       </div>
    2244       <h1 id="rfc.section.A" class="np"><a href="#rfc.section.A">A.</a>&nbsp;<a id="changes.from.rfc.2616" href="#changes.from.rfc.2616">Changes from RFC 2616</a></h1>
    2245       <p id="rfc.section.A.p.1">This document takes over the Status Code Registry, previously defined in <a href="http://tools.ietf.org/html/rfc2817#section-7.1">Section 7.1</a> of <a href="#RFC2817" id="rfc.xref.RFC2817.3"><cite title="Upgrading to TLS Within HTTP/1.1">[RFC2817]</cite></a>. (<a href="#status.code.registry" title="Status Code Registry">Section&nbsp;4.1</a>)
    2246       </p>
    2247       <p id="rfc.section.A.p.2">Clarify definition of POST. (<a href="#POST" id="rfc.xref.POST.3" title="POST">Section&nbsp;7.5</a>)
    2248       </p>
    2249       <p id="rfc.section.A.p.3">Failed to consider that there are many other request methods that are safe to automatically redirect, and further that the
    2250          user agent is able to make that determination based on the request method semantics. (Sections <a href="#status.301" id="rfc.xref.status.301.3" title="301 Moved Permanently">8.3.2</a>, <a href="#status.302" id="rfc.xref.status.302.3" title="302 Found">8.3.3</a> and <a href="#status.307" id="rfc.xref.status.307.4" title="307 Temporary Redirect">8.3.8</a>)
    2251       </p>
    2252       <p id="rfc.section.A.p.4">Deprecate 305 Use Proxy status code, because user agents did not implement it. It used to indicate that the target resource
    2253          must be accessed through the proxy given by the Location field. The Location field gave the URI of the proxy. The recipient
    2254          was expected to repeat this single request via the proxy. (<a href="#status.305" id="rfc.xref.status.305.3" title="305 Use Proxy">Section&nbsp;8.3.6</a>)
    2255       </p>
    2256       <p id="rfc.section.A.p.5">Reclassify "Allow" as response header field, removing the option to specify it in a PUT request. Relax the server requirement
    2257          on the contents of the Allow header field and remove requirement on clients to always trust the header field value. (<a href="#header.allow" id="rfc.xref.header.allow.4" title="Allow">Section&nbsp;9.1</a>)
    2258       </p>
    2259       <p id="rfc.section.A.p.6">Correct syntax of Location header field to allow URI references (including relative references and fragments), as referred
    2260          symbol "absoluteURI" wasn't what was expected, and add some clarifications as to when use of fragments would not be appropriate.
    2261          (<a href="#header.location" id="rfc.xref.header.location.4" title="Location">Section&nbsp;9.4</a>)
    2262       </p>
    2263       <p id="rfc.section.A.p.7">Allow Referer field value of "about:blank" as alternative to not specifying it. (<a href="#header.referer" id="rfc.xref.header.referer.3" title="Referer">Section&nbsp;9.6</a>)
    2264       </p>
    2265       <p id="rfc.section.A.p.8">In the description of the Server header field, the Via field was described as a SHOULD. The requirement was and is stated
    2266          correctly in the description of the Via header field in <a href="p1-messaging.html#header.via" title="Via">Section 9.9</a> of <a href="#Part1" id="rfc.xref.Part1.34"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>. (<a href="#header.server" id="rfc.xref.header.server.4" title="Server">Section&nbsp;9.8</a>)
    2267       </p>
    2268       <h1 id="rfc.section.B"><a href="#rfc.section.B">B.</a>&nbsp;<a id="collected.abnf" href="#collected.abnf">Collected ABNF</a></h1>
    2269       <div id="rfc.figure.u.30"></div> <pre class="inline"><a href="#abnf.dependencies" class="smpl">Accept</a> = &lt;Accept, defined in [Part3], Section 6.1&gt;
    2270 <a href="#abnf.dependencies" class="smpl">Accept-Charset</a> = &lt;Accept-Charset, defined in [Part3], Section 6.2&gt;
    2271 <a href="#abnf.dependencies" class="smpl">Accept-Encoding</a> = &lt;Accept-Encoding, defined in [Part3], Section 6.3&gt;
    2272 <a href="#abnf.dependencies" class="smpl">Accept-Language</a> = &lt;Accept-Language, defined in [Part3], Section 6.4&gt;
    2273 <a href="#abnf.dependencies" class="smpl">Accept-Ranges</a> = &lt;Accept-Ranges, defined in [Part5], Section 5.1&gt;
    2274 <a href="#abnf.dependencies" class="smpl">Age</a> = &lt;Age, defined in [Part6], Section 3.1&gt;
    2275 <a href="#header.allow" class="smpl">Allow</a> = "Allow:" OWS Allow-v
    2276 <a href="#header.allow" class="smpl">Allow-v</a> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
    2277 <a href="#abnf.dependencies" class="smpl">Authorization</a> = &lt;Authorization, defined in [Part7], Section 4.1&gt;
    2278 
    2279 <a href="#abnf.dependencies" class="smpl">ETag</a> = &lt;ETag, defined in [Part4], Section 6.1&gt;
    2280 <a href="#header.expect" class="smpl">Expect</a> = "Expect:" OWS Expect-v
    2281 <a href="#header.expect" class="smpl">Expect-v</a> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
    2282 
    2283 <a href="#header.from" class="smpl">From</a> = "From:" OWS From-v
    2284 <a href="#header.from" class="smpl">From-v</a> = mailbox
    2285 
    2286 <a href="#abnf.dependencies" class="smpl">HTTP-date</a> = &lt;HTTP-date, defined in [Part1], Section 6.1&gt;
    2287 <a href="#abnf.dependencies" class="smpl">Host</a> = &lt;Host, defined in [Part1], Section 2.6&gt;
    2288 
    2289 <a href="#abnf.dependencies" class="smpl">If-Match</a> = &lt;If-Match, defined in [Part4], Section 6.2&gt;
    2290 If-Modified-Since =
    2291  &lt;If-Modified-Since, defined in [Part4], Section 6.3&gt;
    2292 <a href="#abnf.dependencies" class="smpl">If-None-Match</a> = &lt;If-None-Match, defined in [Part4], Section 6.4&gt;
    2293 <a href="#abnf.dependencies" class="smpl">If-Range</a> = &lt;If-Range, defined in [Part5], Section 5.3&gt;
    2294 If-Unmodified-Since =
    2295  &lt;If-Unmodified-Since, defined in [Part4], Section 6.5&gt;
    2296 
    2297 <a href="#header.location" class="smpl">Location</a> = "Location:" OWS Location-v
    2298 <a href="#header.location" class="smpl">Location-v</a> = URI-reference
    2299 
    2300 <a href="#header.max-forwards" class="smpl">Max-Forwards</a> = "Max-Forwards:" OWS Max-Forwards-v
    2301 <a href="#header.max-forwards" class="smpl">Max-Forwards-v</a> = 1*DIGIT
    2302 <a href="#method" class="smpl">Method</a> = %x4F.50.54.49.4F.4E.53 ; OPTIONS
    2303  / %x47.45.54 ; GET
    2304  / %x48.45.41.44 ; HEAD
    2305  / %x50.4F.53.54 ; POST
    2306  / %x50.55.54 ; PUT
    2307  / %x44.45.4C.45.54.45 ; DELETE
    2308  / %x54.52.41.43.45 ; TRACE
    2309  / %x43.4F.4E.4E.45.43.54 ; CONNECT
    2310  / extension-method
    2311 
    2312 <a href="#core.rules" class="smpl">OWS</a> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
    2313 
    2314 Proxy-Authenticate =
    2315  &lt;Proxy-Authenticate, defined in [Part7], Section 4.2&gt;
    2316 Proxy-Authorization =
    2317  &lt;Proxy-Authorization, defined in [Part7], Section 4.3&gt;
    2318 
    2319 <a href="#core.rules" class="smpl">RWS</a> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
    2320 <a href="#abnf.dependencies" class="smpl">Range</a> = &lt;Range, defined in [Part5], Section 5.4&gt;
    2321 <a href="#status.code.and.reason.phrase" class="smpl">Reason-Phrase</a> = *( WSP / VCHAR / obs-text )
    2322 <a href="#header.referer" class="smpl">Referer</a> = "Referer:" OWS Referer-v
    2323 <a href="#header.referer" class="smpl">Referer-v</a> = absolute-URI / partial-URI
    2324 <a href="#header.retry-after" class="smpl">Retry-After</a> = "Retry-After:" OWS Retry-After-v
    2325 <a href="#header.retry-after" class="smpl">Retry-After-v</a> = HTTP-date / delta-seconds
    2326 
    2327 <a href="#header.server" class="smpl">Server</a> = "Server:" OWS Server-v
    2328 <a href="#header.server" class="smpl">Server-v</a> = product *( RWS ( product / comment ) )
    2329 <a href="#status.code.and.reason.phrase" class="smpl">Status-Code</a> = "100" / "101" / "200" / "201" / "202" / "203" / "204" /
    2330  "205" / "206" / "300" / "301" / "302" / "303" / "304" / "305" /
    2331  "307" / "400" / "401" / "402" / "403" / "404" / "405" / "406" /
    2332  "407" / "408" / "409" / "410" / "411" / "412" / "413" / "414" /
    2333  "415" / "416" / "417" / "500" / "501" / "502" / "503" / "504" /
    2334  "505" / extension-code
    2335 
    2336 <a href="#abnf.dependencies" class="smpl">TE</a> = &lt;TE, defined in [Part1], Section 9.5&gt;
    2337 
    2338 <a href="#abnf.dependencies" class="smpl">URI-reference</a> = &lt;URI-reference, defined in [Part1], Section 2.6&gt;
    2339 <a href="#header.user-agent" class="smpl">User-Agent</a> = "User-Agent:" OWS User-Agent-v
    2340 <a href="#header.user-agent" class="smpl">User-Agent-v</a> = product *( RWS ( product / comment ) )
    2341 
    2342 <a href="#abnf.dependencies" class="smpl">Vary</a> = &lt;Vary, defined in [Part6], Section 3.5&gt;
    2343 
    2344 WWW-Authenticate =
    2345  &lt;WWW-Authenticate, defined in [Part7], Section 4.4&gt;
    2346 
    2347 <a href="#abnf.dependencies" class="smpl">absolute-URI</a> = &lt;absolute-URI, defined in [Part1], Section 2.6&gt;
    2348 
    2349 <a href="#abnf.dependencies" class="smpl">comment</a> = &lt;comment, defined in [Part1], Section 3.2&gt;
    2350 
    2351 <a href="#rule.delta-seconds" class="smpl">delta-seconds</a> = 1*DIGIT
    2352 
    2353 <a href="#header.expect" class="smpl">expect-params</a> = ";" token [ "=" ( token / quoted-string ) ]
    2354 <a href="#header.expect" class="smpl">expectation</a> = "100-continue" / expectation-extension
    2355 <a href="#header.expect" class="smpl">expectation-extension</a> = token [ "=" ( token / quoted-string )
    2356  *expect-params ]
    2357 <a href="#status.code.and.reason.phrase" class="smpl">extension-code</a> = 3DIGIT
    2358 <a href="#method" class="smpl">extension-method</a> = token
    2359 
    2360 <a href="#header.from" class="smpl">mailbox</a> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
    2361 
    2362 <a href="#core.rules" class="smpl">obs-text</a> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
    2363 
    2364 <a href="#abnf.dependencies" class="smpl">partial-URI</a> = &lt;partial-URI, defined in [Part1], Section 2.6&gt;
    2365 <a href="#abnf.dependencies" class="smpl">product</a> = &lt;product, defined in [Part1], Section 6.3&gt;
    2366 
    2367 <a href="#core.rules" class="smpl">quoted-string</a> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
    2368 
    2369 <a href="#request.header.fields" class="smpl">request-header</a> = Accept / Accept-Charset / Accept-Encoding /
    2370  Accept-Language / Authorization / Expect / From / Host / If-Match /
    2371  If-Modified-Since / If-None-Match / If-Range / If-Unmodified-Since /
    2372  Max-Forwards / Proxy-Authorization / Range / Referer / TE /
    2373  User-Agent
    2374 <a href="#response.header.fields" class="smpl">response-header</a> = Accept-Ranges / Age / Allow / ETag / Location /
    2375  Proxy-Authenticate / Retry-After / Server / Vary / WWW-Authenticate
    2376 
    2377 <a href="#core.rules" class="smpl">token</a> = &lt;token, defined in [Part1], Section 1.2.2&gt;
    2378 </pre> <div id="rfc.figure.u.31"></div>
    2379       <p>ABNF diagnostics:</p><pre class="inline">; Reason-Phrase defined but not used
    2380 ; Status-Code defined but not used
    2381 ; request-header defined but not used
    2382 ; response-header defined but not used
    2383 </pre><h1 id="rfc.section.C"><a href="#rfc.section.C">C.</a>&nbsp;<a id="change.log" href="#change.log">Change Log (to be removed by RFC Editor before publication)</a></h1>
    2384       <h2 id="rfc.section.C.1"><a href="#rfc.section.C.1">C.1</a>&nbsp;Since RFC 2616
    2385       </h2>
    2386       <p id="rfc.section.C.1.p.1">Extracted relevant partitions from <a href="#RFC2616" id="rfc.xref.RFC2616.3"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>.
    2387       </p>
    2388       <h2 id="rfc.section.C.2"><a href="#rfc.section.C.2">C.2</a>&nbsp;Since draft-ietf-httpbis-p2-semantics-00
    2389       </h2>
    2390       <p id="rfc.section.C.2.p.1">Closed issues: </p>
    2391       <ul>
    2392          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/5">http://tools.ietf.org/wg/httpbis/trac/ticket/5</a>&gt;: "Via is a MUST" (&lt;<a href="http://purl.org/NET/http-errata#via-must">http://purl.org/NET/http-errata#via-must</a>&gt;)
    2393          </li>
    2394          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/6">http://tools.ietf.org/wg/httpbis/trac/ticket/6</a>&gt;: "Fragments allowed in Location" (&lt;<a href="http://purl.org/NET/http-errata#location-fragments">http://purl.org/NET/http-errata#location-fragments</a>&gt;)
    2395          </li>
    2396          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/10">http://tools.ietf.org/wg/httpbis/trac/ticket/10</a>&gt;: "Safe Methods vs Redirection" (&lt;<a href="http://purl.org/NET/http-errata#saferedirect">http://purl.org/NET/http-errata#saferedirect</a>&gt;)
    2397          </li>
    2398          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/17">http://tools.ietf.org/wg/httpbis/trac/ticket/17</a>&gt;: "Revise description of the POST method" (&lt;<a href="http://purl.org/NET/http-errata#post">http://purl.org/NET/http-errata#post</a>&gt;)
    2399          </li>
    2400          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/35">http://tools.ietf.org/wg/httpbis/trac/ticket/35</a>&gt;: "Normative and Informative references"
    2401          </li>
    2402          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/42">http://tools.ietf.org/wg/httpbis/trac/ticket/42</a>&gt;: "RFC2606 Compliance"
    2403          </li>
    2404          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/65">http://tools.ietf.org/wg/httpbis/trac/ticket/65</a>&gt;: "Informative references"
    2405          </li>
    2406          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/84">http://tools.ietf.org/wg/httpbis/trac/ticket/84</a>&gt;: "Redundant cross-references"
    2407          </li>
    2408       </ul>
    2409       <p id="rfc.section.C.2.p.2">Other changes: </p>
    2410       <ul>
    2411          <li>Move definitions of 304 and 412 condition codes to <a href="#Part4" id="rfc.xref.Part4.17"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>
    2412          </li>
    2413       </ul>
    2414       <h2 id="rfc.section.C.3"><a href="#rfc.section.C.3">C.3</a>&nbsp;Since draft-ietf-httpbis-p2-semantics-01
    2415       </h2>
    2416       <p id="rfc.section.C.3.p.1">Closed issues: </p>
    2417       <ul>
    2418          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/21">http://tools.ietf.org/wg/httpbis/trac/ticket/21</a>&gt;: "PUT side effects"
    2419          </li>
    2420          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/91">http://tools.ietf.org/wg/httpbis/trac/ticket/91</a>&gt;: "Duplicate Host header requirements"
    2421          </li>
    2422       </ul>
    2423       <p id="rfc.section.C.3.p.2">Ongoing work on ABNF conversion (&lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/36">http://tools.ietf.org/wg/httpbis/trac/ticket/36</a>&gt;):
    2424       </p>
    2425       <ul>
    2426          <li>Move "Product Tokens" section (back) into Part 1, as "token" is used in the definition of the Upgrade header field.</li>
    2427          <li>Add explicit references to BNF syntax and rules imported from other parts of the specification.</li>
    2428          <li>Copy definition of delta-seconds from Part6 instead of referencing it.</li>
    2429       </ul>
    2430       <h2 id="rfc.section.C.4"><a href="#rfc.section.C.4">C.4</a>&nbsp;<a id="changes.since.02" href="#changes.since.02">Since draft-ietf-httpbis-p2-semantics-02</a></h2>
    2431       <p id="rfc.section.C.4.p.1">Closed issues: </p>
    2432       <ul>
    2433          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/24">http://tools.ietf.org/wg/httpbis/trac/ticket/24</a>&gt;: "Requiring Allow in 405 responses"
    2434          </li>
    2435          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/59">http://tools.ietf.org/wg/httpbis/trac/ticket/59</a>&gt;: "Status Code Registry"
    2436          </li>
    2437          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/61">http://tools.ietf.org/wg/httpbis/trac/ticket/61</a>&gt;: "Redirection vs. Location"
    2438          </li>
    2439          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/70">http://tools.ietf.org/wg/httpbis/trac/ticket/70</a>&gt;: "Cacheability of 303 response"
    2440          </li>
    2441          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/76">http://tools.ietf.org/wg/httpbis/trac/ticket/76</a>&gt;: "305 Use Proxy"
    2442          </li>
    2443          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/105">http://tools.ietf.org/wg/httpbis/trac/ticket/105</a>&gt;: "Classification for Allow header"
    2444          </li>
    2445          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/112">http://tools.ietf.org/wg/httpbis/trac/ticket/112</a>&gt;: "PUT - 'store under' vs 'store at'"
    2446          </li>
    2447       </ul>
    2448       <p id="rfc.section.C.4.p.2">Ongoing work on IANA Message Header Field Registration (&lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/40">http://tools.ietf.org/wg/httpbis/trac/ticket/40</a>&gt;):
    2449       </p>
    2450       <ul>
    2451          <li>Reference RFC 3984, and update header field registrations for headers defined in this document.</li>
    2452       </ul>
    2453       <p id="rfc.section.C.4.p.3">Ongoing work on ABNF conversion (&lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/36">http://tools.ietf.org/wg/httpbis/trac/ticket/36</a>&gt;):
    2454       </p>
    2455       <ul>
    2456          <li>Replace string literals when the string really is case-sensitive (method).</li>
    2457       </ul>
    2458       <h2 id="rfc.section.C.5"><a href="#rfc.section.C.5">C.5</a>&nbsp;<a id="changes.since.03" href="#changes.since.03">Since draft-ietf-httpbis-p2-semantics-03</a></h2>
    2459       <p id="rfc.section.C.5.p.1">Closed issues: </p>
    2460       <ul>
    2461          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/98">http://tools.ietf.org/wg/httpbis/trac/ticket/98</a>&gt;: "OPTIONS request bodies"
    2462          </li>
    2463          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/119">http://tools.ietf.org/wg/httpbis/trac/ticket/119</a>&gt;: "Description of CONNECT should refer to RFC2817"
    2464          </li>
    2465          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/125">http://tools.ietf.org/wg/httpbis/trac/ticket/125</a>&gt;: "Location Content-Location reference request/response mixup"
    2466          </li>
    2467       </ul>
    2468       <p id="rfc.section.C.5.p.2">Ongoing work on Method Registry (&lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/72">http://tools.ietf.org/wg/httpbis/trac/ticket/72</a>&gt;):
    2469       </p>
    2470       <ul>
    2471          <li>Added initial proposal for registration process, plus initial content (non-HTTP/1.1 methods to be added by a separate specification).</li>
    2472       </ul>
    2473       <h2 id="rfc.section.C.6"><a href="#rfc.section.C.6">C.6</a>&nbsp;<a id="changes.since.04" href="#changes.since.04">Since draft-ietf-httpbis-p2-semantics-04</a></h2>
    2474       <p id="rfc.section.C.6.p.1">Closed issues: </p>
    2475       <ul>
    2476          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/103">http://tools.ietf.org/wg/httpbis/trac/ticket/103</a>&gt;: "Content-*"
    2477          </li>
    2478          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/132">http://tools.ietf.org/wg/httpbis/trac/ticket/132</a>&gt;: "RFC 2822 is updated by RFC 5322"
    2479          </li>
    2480       </ul>
    2481       <p id="rfc.section.C.6.p.2">Ongoing work on ABNF conversion (&lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/36">http://tools.ietf.org/wg/httpbis/trac/ticket/36</a>&gt;):
    2482       </p>
    2483       <ul>
    2484          <li>Use "/" instead of "|" for alternatives.</li>
    2485          <li>Introduce new ABNF rules for "bad" whitespace ("BWS"), optional whitespace ("OWS") and required whitespace ("RWS").</li>
    2486          <li>Rewrite ABNFs to spell out whitespace rules, factor out header field value format definitions.</li>
    2487       </ul>
    2488       <h2 id="rfc.section.C.7"><a href="#rfc.section.C.7">C.7</a>&nbsp;<a id="changes.since.05" href="#changes.since.05">Since draft-ietf-httpbis-p2-semantics-05</a></h2>
    2489       <p id="rfc.section.C.7.p.1">Closed issues: </p>
    2490       <ul>
    2491          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/94">http://tools.ietf.org/wg/httpbis/trac/ticket/94</a>&gt;: "Reason-Phrase BNF"
    2492          </li>
    2493       </ul>
    2494       <p id="rfc.section.C.7.p.2">Final work on ABNF conversion (&lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/36">http://tools.ietf.org/wg/httpbis/trac/ticket/36</a>&gt;):
    2495       </p>
    2496       <ul>
    2497          <li>Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.</li>
    2498       </ul>
    2499       <h2 id="rfc.section.C.8"><a href="#rfc.section.C.8">C.8</a>&nbsp;<a id="changes.since.06" href="#changes.since.06">Since draft-ietf-httpbis-p2-semantics-06</a></h2>
    2500       <p id="rfc.section.C.8.p.1">Closed issues: </p>
    2501       <ul>
    2502          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/144">http://tools.ietf.org/wg/httpbis/trac/ticket/144</a>&gt;: "Clarify when Referer is sent"
    2503          </li>
    2504          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/164">http://tools.ietf.org/wg/httpbis/trac/ticket/164</a>&gt;: "status codes vs methods"
    2505          </li>
    2506          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/170">http://tools.ietf.org/wg/httpbis/trac/ticket/170</a>&gt;: "Do not require "updates" relation for specs that register status codes or method names"
    2507          </li>
    2508       </ul>
    2509       <h2 id="rfc.section.C.9"><a href="#rfc.section.C.9">C.9</a>&nbsp;<a id="changes.since.07" href="#changes.since.07">Since draft-ietf-httpbis-p2-semantics-07</a></h2>
    2510       <p id="rfc.section.C.9.p.1">Closed issues: </p>
    2511       <ul>
    2512          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/27">http://tools.ietf.org/wg/httpbis/trac/ticket/27</a>&gt;: "Idempotency"
    2513          </li>
    2514          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/33">http://tools.ietf.org/wg/httpbis/trac/ticket/33</a>&gt;: "TRACE security considerations"
    2515          </li>
    2516          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/110">http://tools.ietf.org/wg/httpbis/trac/ticket/110</a>&gt;: "Clarify rules for determining what entities a response carries"
    2517          </li>
    2518          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/140">http://tools.ietf.org/wg/httpbis/trac/ticket/140</a>&gt;: "update note citing RFC 1945 and 2068"
    2519          </li>
    2520          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/182">http://tools.ietf.org/wg/httpbis/trac/ticket/182</a>&gt;: "update note about redirect limit"
    2521          </li>
    2522          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/191">http://tools.ietf.org/wg/httpbis/trac/ticket/191</a>&gt;: "Location header ABNF should use 'URI'"
    2523          </li>
    2524          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/192">http://tools.ietf.org/wg/httpbis/trac/ticket/192</a>&gt;: "fragments in Location vs status 303"
    2525          </li>
    2526          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/198">http://tools.ietf.org/wg/httpbis/trac/ticket/198</a>&gt;: "move IANA registrations for optional status codes"
    2527          </li>
    2528       </ul>
    2529       <p id="rfc.section.C.9.p.2">Partly resolved issues: </p>
    2530       <ul>
    2531          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/171">http://tools.ietf.org/wg/httpbis/trac/ticket/171</a>&gt;: "Are OPTIONS and TRACE safe?"
    2532          </li>
    2533       </ul>
    2534       <h2 id="rfc.section.C.10"><a href="#rfc.section.C.10">C.10</a>&nbsp;<a id="changes.since.08" href="#changes.since.08">Since draft-ietf-httpbis-p2-semantics-08</a></h2>
    2535       <p id="rfc.section.C.10.p.1">Closed issues: </p>
    2536       <ul>
    2537          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/10">http://tools.ietf.org/wg/httpbis/trac/ticket/10</a>&gt;: "Safe Methods vs Redirection" (we missed the introduction to the 3xx status codes when fixing this previously)
    2538          </li>
    2539       </ul>
    2540       <h2 id="rfc.section.C.11"><a href="#rfc.section.C.11">C.11</a>&nbsp;<a id="changes.since.09" href="#changes.since.09">Since draft-ietf-httpbis-p2-semantics-09</a></h2>
    2541       <p id="rfc.section.C.11.p.1">Closed issues: </p>
    2542       <ul>
    2543          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/43">http://tools.ietf.org/wg/httpbis/trac/ticket/43</a>&gt;: "Fragment combination / precedence during redirects"
    2544          </li>
    2545       </ul>
    2546       <p id="rfc.section.C.11.p.2">Partly resolved issues: </p>
    2547       <ul>
    2548          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/185">http://tools.ietf.org/wg/httpbis/trac/ticket/185</a>&gt;: "Location header payload handling"
    2549          </li>
    2550          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/196">http://tools.ietf.org/wg/httpbis/trac/ticket/196</a>&gt;: "Term for the requested resource's URI"
    2551          </li>
    2552       </ul>
    2553       <h2 id="rfc.section.C.12"><a href="#rfc.section.C.12">C.12</a>&nbsp;<a id="changes.since.10" href="#changes.since.10">Since draft-ietf-httpbis-p2-semantics-10</a></h2>
    2554       <p id="rfc.section.C.12.p.1">Closed issues: </p>
    2555       <ul>
    2556          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/69">http://tools.ietf.org/wg/httpbis/trac/ticket/69</a>&gt;: "Clarify 'Requested Variant'"
    2557          </li>
    2558          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/109">http://tools.ietf.org/wg/httpbis/trac/ticket/109</a>&gt;: "Clarify entity / representation / variant terminology"
    2559          </li>
    2560          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/139">http://tools.ietf.org/wg/httpbis/trac/ticket/139</a>&gt;: "Methods and Caching"
    2561          </li>
    2562          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/190">http://tools.ietf.org/wg/httpbis/trac/ticket/190</a>&gt;: "OPTIONS vs Max-Forwards"
    2563          </li>
    2564          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/199">http://tools.ietf.org/wg/httpbis/trac/ticket/199</a>&gt;: "Status codes and caching"
    2565          </li>
    2566          <li> &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/220">http://tools.ietf.org/wg/httpbis/trac/ticket/220</a>&gt;: "consider removing the 'changes from 2068' sections"
    2567          </li>
    2568       </ul>
    2569       <h2 id="rfc.section.C.13"><a href="#rfc.section.C.13">C.13</a>&nbsp;<a id="changes.since.11" href="#changes.since.11">Since draft-ietf-httpbis-p2-semantics-11</a></h2>
    2570       <p id="rfc.section.C.13.p.1">None yet.</p>
    2571       <h1 id="rfc.index"><a href="#rfc.index">Index</a></h1>
    2572       <p class="noprint"><a href="#rfc.index.1">1</a> <a href="#rfc.index.2">2</a> <a href="#rfc.index.3">3</a> <a href="#rfc.index.4">4</a> <a href="#rfc.index.5">5</a> <a href="#rfc.index.A">A</a> <a href="#rfc.index.C">C</a> <a href="#rfc.index.D">D</a> <a href="#rfc.index.E">E</a> <a href="#rfc.index.F">F</a> <a href="#rfc.index.G">G</a> <a href="#rfc.index.H">H</a> <a href="#rfc.index.I">I</a> <a href="#rfc.index.L">L</a> <a href="#rfc.index.M">M</a> <a href="#rfc.index.O">O</a> <a href="#rfc.index.P">P</a> <a href="#rfc.index.R">R</a> <a href="#rfc.index.S">S</a> <a href="#rfc.index.T">T</a> <a href="#rfc.index.U">U</a>
    2573       </p>
    2574       <div class="print2col">
    2575          <ul class="ind">
    2576             <li class="indline0"><a id="rfc.index.1" href="#rfc.index.1"><b>1</b></a><ul class="ind">
    2577                   <li class="indline1">100 Continue (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.100.1">4</a>, <a class="iref" href="#rfc.iref.25"><b>8.1.1</b></a>, <a class="iref" href="#rfc.xref.status.100.2">10.2</a></li>
    2578                   <li class="indline1">101 Switching Protocols (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.101.1">4</a>, <a class="iref" href="#rfc.iref.26"><b>8.1.2</b></a>, <a class="iref" href="#rfc.xref.status.101.2">10.2</a></li>
    2579                </ul>
    2580             </li>
    2581             <li class="indline0"><a id="rfc.index.2" href="#rfc.index.2"><b>2</b></a><ul class="ind">
    2582                   <li class="indline1">200 OK (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.200.1">4</a>, <a class="iref" href="#rfc.iref.27"><b>8.2.1</b></a>, <a class="iref" href="#rfc.xref.status.200.2">10.2</a></li>
    2583                   <li class="indline1">201 Created (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.201.1">4</a>, <a class="iref" href="#rfc.iref.28"><b>8.2.2</b></a>, <a class="iref" href="#rfc.xref.status.201.2">10.2</a></li>
    2584                   <li class="indline1">202 Accepted (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.202.1">4</a>, <a class="iref" href="#rfc.iref.29"><b>8.2.3</b></a>, <a class="iref" href="#rfc.xref.status.202.2">10.2</a></li>
    2585                   <li class="indline1">203 Non-Authoritative Information (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.203.1">4</a>, <a class="iref" href="#rfc.iref.30"><b>8.2.4</b></a>, <a class="iref" href="#rfc.xref.status.203.2">10.2</a></li>
    2586                   <li class="indline1">204 No Content (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.204.1">4</a>, <a class="iref" href="#rfc.iref.31"><b>8.2.5</b></a>, <a class="iref" href="#rfc.xref.status.204.2">10.2</a></li>
    2587                   <li class="indline1">205 Reset Content (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.205.1">4</a>, <a class="iref" href="#rfc.iref.32"><b>8.2.6</b></a>, <a class="iref" href="#rfc.xref.status.205.2">10.2</a></li>
    2588                   <li class="indline1">206 Partial Content (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.iref.33"><b>8.2.7</b></a></li>
    2589                </ul>
    2590             </li>
    2591             <li class="indline0"><a id="rfc.index.3" href="#rfc.index.3"><b>3</b></a><ul class="ind">
    2592                   <li class="indline1">300 Multiple Choices (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.300.1">4</a>, <a class="iref" href="#rfc.iref.34"><b>8.3.1</b></a>, <a class="iref" href="#rfc.xref.status.300.2">10.2</a></li>
    2593                   <li class="indline1">301 Moved Permanently (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.301.1">4</a>, <a class="iref" href="#rfc.iref.35"><b>8.3.2</b></a>, <a class="iref" href="#rfc.xref.status.301.2">10.2</a>, <a class="iref" href="#rfc.xref.status.301.3">A</a></li>
    2594                   <li class="indline1">302 Found (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.302.1">4</a>, <a class="iref" href="#rfc.iref.36"><b>8.3.3</b></a>, <a class="iref" href="#rfc.xref.status.302.2">10.2</a>, <a class="iref" href="#rfc.xref.status.302.3">A</a></li>
    2595                   <li class="indline1">303 See Other (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.303.1">4</a>, <a class="iref" href="#rfc.xref.status.303.2">8.3.3</a>, <a class="iref" href="#rfc.iref.37"><b>8.3.4</b></a>, <a class="iref" href="#rfc.xref.status.303.3">10.2</a></li>
    2596                   <li class="indline1">304 Not Modified (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.iref.38"><b>8.3.5</b></a></li>
    2597                   <li class="indline1">305 Use Proxy (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.305.1">4</a>, <a class="iref" href="#rfc.iref.39"><b>8.3.6</b></a>, <a class="iref" href="#rfc.xref.status.305.2">10.2</a>, <a class="iref" href="#rfc.xref.status.305.3">A</a></li>
    2598                   <li class="indline1">306 (Unused) (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.iref.40"><b>8.3.7</b></a>, <a class="iref" href="#rfc.xref.status.306.1">10.2</a></li>
    2599                   <li class="indline1">307 Temporary Redirect (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.307.1">4</a>, <a class="iref" href="#rfc.xref.status.307.2">8.3.3</a>, <a class="iref" href="#rfc.iref.41"><b>8.3.8</b></a>, <a class="iref" href="#rfc.xref.status.307.3">10.2</a>, <a class="iref" href="#rfc.xref.status.307.4">A</a></li>
    2600                </ul>
    2601             </li>
    2602             <li class="indline0"><a id="rfc.index.4" href="#rfc.index.4"><b>4</b></a><ul class="ind">
    2603                   <li class="indline1">400 Bad Request (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.400.1">4</a>, <a class="iref" href="#rfc.iref.42"><b>8.4.1</b></a>, <a class="iref" href="#rfc.xref.status.400.2">10.2</a></li>
    2604                   <li class="indline1">401 Unauthorized (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.iref.43"><b>8.4.2</b></a></li>
    2605                   <li class="indline1">402 Payment Required (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.402.1">4</a>, <a class="iref" href="#rfc.iref.44"><b>8.4.3</b></a>, <a class="iref" href="#rfc.xref.status.402.2">10.2</a></li>
    2606                   <li class="indline1">403 Forbidden (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.403.1">4</a>, <a class="iref" href="#rfc.iref.45"><b>8.4.4</b></a>, <a class="iref" href="#rfc.xref.status.403.2">10.2</a></li>
    2607                   <li class="indline1">404 Not Found (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.404.1">4</a>, <a class="iref" href="#rfc.iref.46"><b>8.4.5</b></a>, <a class="iref" href="#rfc.xref.status.404.2">10.2</a></li>
    2608                   <li class="indline1">405 Method Not Allowed (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.405.1">4</a>, <a class="iref" href="#rfc.iref.47"><b>8.4.6</b></a>, <a class="iref" href="#rfc.xref.status.405.2">10.2</a></li>
    2609                   <li class="indline1">406 Not Acceptable (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.406.1">4</a>, <a class="iref" href="#rfc.iref.48"><b>8.4.7</b></a>, <a class="iref" href="#rfc.xref.status.406.2">10.2</a></li>
    2610                   <li class="indline1">407 Proxy Authentication Required (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.iref.49"><b>8.4.8</b></a>, <a class="iref" href="#rfc.xref.status.407.1">10.2</a></li>
    2611                   <li class="indline1">408 Request Timeout (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.408.1">4</a>, <a class="iref" href="#rfc.iref.50"><b>8.4.9</b></a>, <a class="iref" href="#rfc.xref.status.408.2">10.2</a></li>
    2612                   <li class="indline1">409 Conflict (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.409.1">4</a>, <a class="iref" href="#rfc.iref.51"><b>8.4.10</b></a>, <a class="iref" href="#rfc.xref.status.409.2">10.2</a></li>
    2613                   <li class="indline1">410 Gone (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.410.1">4</a>, <a class="iref" href="#rfc.iref.52"><b>8.4.11</b></a>, <a class="iref" href="#rfc.xref.status.410.2">10.2</a></li>
    2614                   <li class="indline1">411 Length Required (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.411.1">4</a>, <a class="iref" href="#rfc.iref.53"><b>8.4.12</b></a>, <a class="iref" href="#rfc.xref.status.411.2">10.2</a></li>
    2615                   <li class="indline1">412 Precondition Failed (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.iref.54"><b>8.4.13</b></a></li>
    2616                   <li class="indline1">413 Request Entity Too Large (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.413.1">4</a>, <a class="iref" href="#rfc.iref.55"><b>8.4.14</b></a>, <a class="iref" href="#rfc.xref.status.413.2">10.2</a></li>
    2617                   <li class="indline1">414 URI Too Long (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.414.1">4</a>, <a class="iref" href="#rfc.iref.56"><b>8.4.15</b></a>, <a class="iref" href="#rfc.xref.status.414.2">10.2</a></li>
    2618                   <li class="indline1">415 Unsupported Media Type (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.415.1">4</a>, <a class="iref" href="#rfc.iref.57"><b>8.4.16</b></a>, <a class="iref" href="#rfc.xref.status.415.2">10.2</a></li>
    2619                   <li class="indline1">416 Requested Range Not Satisfiable (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.iref.58"><b>8.4.17</b></a></li>
    2620                   <li class="indline1">417 Expectation Failed (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.417.1">4</a>, <a class="iref" href="#rfc.iref.59"><b>8.4.18</b></a>, <a class="iref" href="#rfc.xref.status.417.2">10.2</a></li>
    2621                </ul>
    2622             </li>
    2623             <li class="indline0"><a id="rfc.index.5" href="#rfc.index.5"><b>5</b></a><ul class="ind">
    2624                   <li class="indline1">500 Internal Server Error (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.500.1">4</a>, <a class="iref" href="#rfc.iref.60"><b>8.5.1</b></a>, <a class="iref" href="#rfc.xref.status.500.2">10.2</a></li>
    2625                   <li class="indline1">501 Not Implemented (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.501.1">4</a>, <a class="iref" href="#rfc.iref.61"><b>8.5.2</b></a>, <a class="iref" href="#rfc.xref.status.501.2">10.2</a></li>
    2626                   <li class="indline1">502 Bad Gateway (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.502.1">4</a>, <a class="iref" href="#rfc.iref.62"><b>8.5.3</b></a>, <a class="iref" href="#rfc.xref.status.502.2">10.2</a></li>
    2627                   <li class="indline1">503 Service Unavailable (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.503.1">4</a>, <a class="iref" href="#rfc.iref.63"><b>8.5.4</b></a>, <a class="iref" href="#rfc.xref.status.503.2">10.2</a></li>
    2628                   <li class="indline1">504 Gateway Timeout (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.504.1">4</a>, <a class="iref" href="#rfc.iref.64"><b>8.5.5</b></a>, <a class="iref" href="#rfc.xref.status.504.2">10.2</a></li>
    2629                   <li class="indline1">505 HTTP Version Not Supported (status code)&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.505.1">4</a>, <a class="iref" href="#rfc.iref.65"><b>8.5.6</b></a>, <a class="iref" href="#rfc.xref.status.505.2">10.2</a></li>
    2630                </ul>
    2631             </li>
    2632             <li class="indline0"><a id="rfc.index.A" href="#rfc.index.A"><b>A</b></a><ul class="ind">
    2633                   <li class="indline1">Allow header&nbsp;&nbsp;<a class="iref" href="#rfc.xref.header.allow.1">2</a>, <a class="iref" href="#rfc.xref.header.allow.2">5</a>, <a class="iref" href="#rfc.iref.a.1"><b>9.1</b></a>, <a class="iref" href="#rfc.xref.header.allow.3">10.3</a>, <a class="iref" href="#rfc.xref.header.allow.4">A</a></li>
    2634                </ul>
    2635             </li>
    2636             <li class="indline0"><a id="rfc.index.C" href="#rfc.index.C"><b>C</b></a><ul class="ind">
    2637                   <li class="indline1">CONNECT method&nbsp;&nbsp;<a class="iref" href="#rfc.xref.CONNECT.1">2</a>, <a class="iref" href="#rfc.iref.c.1"><b>7.9</b></a>, <a class="iref" href="#rfc.xref.CONNECT.2">10.1</a></li>
    2638                </ul>
    2639             </li>
    2640             <li class="indline0"><a id="rfc.index.D" href="#rfc.index.D"><b>D</b></a><ul class="ind">
    2641                   <li class="indline1">DELETE method&nbsp;&nbsp;<a class="iref" href="#rfc.xref.DELETE.1">2</a>, <a class="iref" href="#rfc.iref.d.1"><b>7.7</b></a>, <a class="iref" href="#rfc.xref.DELETE.2">10.1</a></li>
    2642                </ul>
    2643             </li>
    2644             <li class="indline0"><a id="rfc.index.E" href="#rfc.index.E"><b>E</b></a><ul class="ind">
    2645                   <li class="indline1">Expect header&nbsp;&nbsp;<a class="iref" href="#rfc.xref.header.expect.1">3</a>, <a class="iref" href="#rfc.xref.header.expect.2">8.4.18</a>, <a class="iref" href="#rfc.iref.e.1"><b>9.2</b></a>, <a class="iref" href="#rfc.xref.header.expect.3">10.3</a></li>
    2646                </ul>
    2647             </li>
    2648             <li class="indline0"><a id="rfc.index.F" href="#rfc.index.F"><b>F</b></a><ul class="ind">
    2649                   <li class="indline1">From header&nbsp;&nbsp;<a class="iref" href="#rfc.xref.header.from.1">3</a>, <a class="iref" href="#rfc.iref.f.1"><b>9.3</b></a>, <a class="iref" href="#rfc.xref.header.from.2">10.3</a></li>
    2650                </ul>
    2651             </li>
    2652             <li class="indline0"><a id="rfc.index.G" href="#rfc.index.G"><b>G</b></a><ul class="ind">
    2653                   <li class="indline1">GET method&nbsp;&nbsp;<a class="iref" href="#rfc.xref.GET.1">2</a>, <a class="iref" href="#rfc.iref.g.8"><b>7.3</b></a>, <a class="iref" href="#rfc.xref.GET.2">10.1</a></li>
    2654                   <li class="indline1"><tt>Grammar</tt>&nbsp;&nbsp;
    2655                      <ul class="ind">
    2656                         <li class="indline1"><tt>Allow</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.9"><b>9.1</b></a></li>
    2657                         <li class="indline1"><tt>Allow-v</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.10"><b>9.1</b></a></li>
    2658                         <li class="indline1"><tt>delta-seconds</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.26"><b>9.7</b></a></li>
    2659                         <li class="indline1"><tt>Expect</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.11"><b>9.2</b></a></li>
    2660                         <li class="indline1"><tt>expect-params</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.15"><b>9.2</b></a></li>
    2661                         <li class="indline1"><tt>Expect-v</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.12"><b>9.2</b></a></li>
    2662                         <li class="indline1"><tt>expectation</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.13"><b>9.2</b></a></li>
    2663                         <li class="indline1"><tt>expectation-extension</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.14"><b>9.2</b></a></li>
    2664                         <li class="indline1"><tt>extension-code</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.5"><b>4</b></a></li>
    2665                         <li class="indline1"><tt>extension-method</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.2"><b>2</b></a></li>
    2666                         <li class="indline1"><tt>From</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.16"><b>9.3</b></a></li>
    2667                         <li class="indline1"><tt>From-v</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.17"><b>9.3</b></a></li>
    2668                         <li class="indline1"><tt>Location</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.18"><b>9.4</b></a></li>
    2669                         <li class="indline1"><tt>Location-v</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.19"><b>9.4</b></a></li>
    2670                         <li class="indline1"><tt>Max-Forwards</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.20"><b>9.5</b></a></li>
    2671                         <li class="indline1"><tt>Max-Forwards-v</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.21"><b>9.5</b></a></li>
    2672                         <li class="indline1"><tt>Method</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.1"><b>2</b></a></li>
    2673                         <li class="indline1"><tt>Reason-Phrase</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.6"><b>4</b></a></li>
    2674                         <li class="indline1"><tt>Referer</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.22"><b>9.6</b></a></li>
    2675                         <li class="indline1"><tt>Referer-v</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.23"><b>9.6</b></a></li>
    2676                         <li class="indline1"><tt>request-header</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.3"><b>3</b></a></li>
    2677                         <li class="indline1"><tt>response-header</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.7"><b>5</b></a></li>
    2678                         <li class="indline1"><tt>Retry-After</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.24"><b>9.7</b></a></li>
    2679                         <li class="indline1"><tt>Retry-After-v</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.25"><b>9.7</b></a></li>
    2680                         <li class="indline1"><tt>Server</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.27"><b>9.8</b></a></li>
    2681                         <li class="indline1"><tt>Server-v</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.28"><b>9.8</b></a></li>
    2682                         <li class="indline1"><tt>Status-Code</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.4"><b>4</b></a></li>
    2683                         <li class="indline1"><tt>User-Agent</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.29"><b>9.9</b></a></li>
    2684                         <li class="indline1"><tt>User-Agent-v</tt>&nbsp;&nbsp;<a class="iref" href="#rfc.iref.g.30"><b>9.9</b></a></li>
    2685                      </ul>
    2686                   </li>
    2687                </ul>
    2688             </li>
    2689             <li class="indline0"><a id="rfc.index.H" href="#rfc.index.H"><b>H</b></a><ul class="ind">
    2690                   <li class="indline1">HEAD method&nbsp;&nbsp;<a class="iref" href="#rfc.xref.HEAD.1">2</a>, <a class="iref" href="#rfc.iref.h.1"><b>7.4</b></a>, <a class="iref" href="#rfc.xref.HEAD.2">10.1</a></li>
    2691                   <li class="indline1">Headers&nbsp;&nbsp;
    2692                      <ul class="ind">
    2693                         <li class="indline1">Allow&nbsp;&nbsp;<a class="iref" href="#rfc.xref.header.allow.1">2</a>, <a class="iref" href="#rfc.xref.header.allow.2">5</a>, <a class="iref" href="#rfc.iref.h.2"><b>9.1</b></a>, <a class="iref" href="#rfc.xref.header.allow.3">10.3</a>, <a class="iref" href="#rfc.xref.header.allow.4">A</a></li>
    2694                         <li class="indline1">Expect&nbsp;&nbsp;<a class="iref" href="#rfc.xref.header.expect.1">3</a>, <a class="iref" href="#rfc.xref.header.expect.2">8.4.18</a>, <a class="iref" href="#rfc.iref.h.3"><b>9.2</b></a>, <a class="iref" href="#rfc.xref.header.expect.3">10.3</a></li>
    2695                         <li class="indline1">From&nbsp;&nbsp;<a class="iref" href="#rfc.xref.header.from.1">3</a>, <a class="iref" href="#rfc.iref.h.4"><b>9.3</b></a>, <a class="iref" href="#rfc.xref.header.from.2">10.3</a></li>
    2696                         <li class="indline1">Location&nbsp;&nbsp;<a class="iref" href="#rfc.xref.header.location.1">5</a>, <a class="iref" href="#rfc.xref.header.location.2">7.5</a>, <a class="iref" href="#rfc.iref.h.5"><b>9.4</b></a>, <a class="iref" href="#rfc.xref.header.location.3">10.3</a>, <a class="iref" href="#rfc.xref.header.location.4">A</a></li>
    2697                         <li class="indline1">Max-Forwards&nbsp;&nbsp;<a class="iref" href="#rfc.xref.header.max-forwards.1">3</a>, <a class="iref" href="#rfc.xref.header.max-forwards.2">7.2</a>, <a class="iref" href="#rfc.xref.header.max-forwards.3">7.8</a>, <a class="iref" href="#rfc.iref.h.6"><b>9.5</b></a>, <a class="iref" href="#rfc.xref.header.max-forwards.4">10.3</a></li>
    2698                         <li class="indline1">Referer&nbsp;&nbsp;<a class="iref" href="#rfc.xref.header.referer.1">3</a>, <a class="iref" href="#rfc.iref.h.7"><b>9.6</b></a>, <a class="iref" href="#rfc.xref.header.referer.2">10.3</a>, <a class="iref" href="#rfc.xref.header.referer.3">A</a></li>
    2699                         <li class="indline1">Retry-After&nbsp;&nbsp;<a class="iref" href="#rfc.xref.header.retry-after.1">5</a>, <a class="iref" href="#rfc.iref.h.8"><b>9.7</b></a>, <a class="iref" href="#rfc.xref.header.retry-after.2">10.3</a></li>
    2700                         <li class="indline1">Server&nbsp;&nbsp;<a class="iref" href="#rfc.xref.header.server.1">5</a>, <a class="iref" href="#rfc.iref.h.9"><b>9.8</b></a>, <a class="iref" href="#rfc.xref.header.server.2">10.3</a>, <a class="iref" href="#rfc.xref.header.server.3">11.1</a>, <a class="iref" href="#rfc.xref.header.server.4">A</a></li>
    2701                         <li class="indline1">User-Agent&nbsp;&nbsp;<a class="iref" href="#rfc.xref.header.user-agent.1">3</a>, <a class="iref" href="#rfc.iref.h.10"><b>9.9</b></a>, <a class="iref" href="#rfc.xref.header.user-agent.2">10.3</a>, <a class="iref" href="#rfc.xref.header.user-agent.3">11.1</a></li>
    2702                      </ul>
    2703                   </li>
    2704                </ul>
    2705             </li>
    2706             <li class="indline0"><a id="rfc.index.I" href="#rfc.index.I"><b>I</b></a><ul class="ind">
    2707                   <li class="indline1">Idempotent Methods&nbsp;&nbsp;<a class="iref" href="#rfc.iref.i.1"><b>7.1.2</b></a></li>
    2708                </ul>
    2709             </li>
    2710             <li class="indline0"><a id="rfc.index.L" href="#rfc.index.L"><b>L</b></a><ul class="ind">
    2711                   <li class="indline1">Location header&nbsp;&nbsp;<a class="iref" href="#rfc.xref.header.location.1">5</a>, <a class="iref" href="#rfc.xref.header.location.2">7.5</a>, <a class="iref" href="#rfc.iref.l.1"><b>9.4</b></a>, <a class="iref" href="#rfc.xref.header.location.3">10.3</a>, <a class="iref" href="#rfc.xref.header.location.4">A</a></li>
    2712                </ul>
    2713             </li>
    2714             <li class="indline0"><a id="rfc.index.M" href="#rfc.index.M"><b>M</b></a><ul class="ind">
    2715                   <li class="indline1">Max-Forwards header&nbsp;&nbsp;<a class="iref" href="#rfc.xref.header.max-forwards.1">3</a>, <a class="iref" href="#rfc.xref.header.max-forwards.2">7.2</a>, <a class="iref" href="#rfc.xref.header.max-forwards.3">7.8</a>, <a class="iref" href="#rfc.iref.m.9"><b>9.5</b></a>, <a class="iref" href="#rfc.xref.header.max-forwards.4">10.3</a></li>
    2716                   <li class="indline1">Methods&nbsp;&nbsp;
    2717                      <ul class="ind">
    2718                         <li class="indline1">CONNECT&nbsp;&nbsp;<a class="iref" href="#rfc.xref.CONNECT.1">2</a>, <a class="iref" href="#rfc.iref.m.8"><b>7.9</b></a>, <a class="iref" href="#rfc.xref.CONNECT.2">10.1</a></li>
    2719                         <li class="indline1">DELETE&nbsp;&nbsp;<a class="iref" href="#rfc.xref.DELETE.1">2</a>, <a class="iref" href="#rfc.iref.m.6"><b>7.7</b></a>, <a class="iref" href="#rfc.xref.DELETE.2">10.1</a></li>
    2720                         <li class="indline1">GET&nbsp;&nbsp;<a class="iref" href="#rfc.xref.GET.1">2</a>, <a class="iref" href="#rfc.iref.m.2"><b>7.3</b></a>, <a class="iref" href="#rfc.xref.GET.2">10.1</a></li>
    2721                         <li class="indline1">HEAD&nbsp;&nbsp;<a class="iref" href="#rfc.xref.HEAD.1">2</a>, <a class="iref" href="#rfc.iref.m.3"><b>7.4</b></a>, <a class="iref" href="#rfc.xref.HEAD.2">10.1</a></li>
    2722                         <li class="indline1">OPTIONS&nbsp;&nbsp;<a class="iref" href="#rfc.xref.OPTIONS.1">2</a>, <a class="iref" href="#rfc.iref.m.1"><b>7.2</b></a>, <a class="iref" href="#rfc.xref.OPTIONS.2">9.5</a>, <a class="iref" href="#rfc.xref.OPTIONS.3">10.1</a></li>
    2723                         <li class="indline1">POST&nbsp;&nbsp;<a class="iref" href="#rfc.xref.POST.1">2</a>, <a class="iref" href="#rfc.iref.m.4"><b>7.5</b></a>, <a class="iref" href="#rfc.xref.POST.2">10.1</a>, <a class="iref" href="#rfc.xref.POST.3">A</a></li>
    2724                         <li class="indline1">PUT&nbsp;&nbsp;<a class="iref" href="#rfc.xref.PUT.1">2</a>, <a class="iref" href="#rfc.iref.m.5"><b>7.6</b></a>, <a class="iref" href="#rfc.xref.PUT.2">10.1</a></li>
    2725                         <li class="indline1">TRACE&nbsp;&nbsp;<a class="iref" href="#rfc.xref.TRACE.1">2</a>, <a class="iref" href="#rfc.iref.m.7"><b>7.8</b></a>, <a class="iref" href="#rfc.xref.TRACE.2">9.5</a>, <a class="iref" href="#rfc.xref.TRACE.3">10.1</a>, <a class="iref" href="#rfc.xref.TRACE.4">11.1</a></li>
    2726                      </ul>
    2727                   </li>
    2728                </ul>
    2729             </li>
    2730             <li class="indline0"><a id="rfc.index.O" href="#rfc.index.O"><b>O</b></a><ul class="ind">
    2731                   <li class="indline1">OPTIONS method&nbsp;&nbsp;<a class="iref" href="#rfc.xref.OPTIONS.1">2</a>, <a class="iref" href="#rfc.iref.o.1"><b>7.2</b></a>, <a class="iref" href="#rfc.xref.OPTIONS.2">9.5</a>, <a class="iref" href="#rfc.xref.OPTIONS.3">10.1</a></li>
    2732                </ul>
    2733             </li>
    2734             <li class="indline0"><a id="rfc.index.P" href="#rfc.index.P"><b>P</b></a><ul class="ind">
    2735                   <li class="indline1"><em>Part1</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part1.1">1</a>, <a class="iref" href="#rfc.xref.Part1.2">1.2</a>, <a class="iref" href="#rfc.xref.Part1.3">1.2.1</a>, <a class="iref" href="#rfc.xref.Part1.4">1.2.1</a>, <a class="iref" href="#rfc.xref.Part1.5">1.2.1</a>, <a class="iref" href="#rfc.xref.Part1.6">1.2.1</a>, <a class="iref" href="#rfc.xref.Part1.7">1.2.1</a>, <a class="iref" href="#rfc.xref.Part1.8">1.2.1</a>, <a class="iref" href="#rfc.xref.Part1.9">1.2.2</a>, <a class="iref" href="#rfc.xref.Part1.10">1.2.2</a>, <a class="iref" href="#rfc.xref.Part1.11">1.2.2</a>, <a class="iref" href="#rfc.xref.Part1.12">1.2.2</a>, <a class="iref" href="#rfc.xref.Part1.13">1.2.2</a>, <a class="iref" href="#rfc.xref.Part1.14">1.2.2</a>, <a class="iref" href="#rfc.xref.Part1.15">1.2.2</a>, <a class="iref" href="#rfc.xref.Part1.16">1.2.2</a>, <a class="iref" href="#rfc.xref.Part1.17">2</a>, <a class="iref" href="#rfc.xref.Part1.18">3</a>, <a class="iref" href="#rfc.xref.Part1.19">3</a>, <a class="iref" href="#rfc.xref.Part1.20">5</a>, <a class="iref" href="#rfc.xref.Part1.21">6</a>, <a class="iref" href="#rfc.xref.Part1.22">6.1</a>, <a class="iref" href="#rfc.xref.Part1.23">7.8</a>, <a class="iref" href="#rfc.xref.Part1.24">7.8</a>, <a class="iref" href="#rfc.xref.Part1.25">8.1.1</a>, <a class="iref" href="#rfc.xref.Part1.26">8.1.2</a>, <a class="iref" href="#rfc.xref.Part1.27">8.5.6</a>, <a class="iref" href="#rfc.xref.Part1.28">9.2</a>, <a class="iref" href="#rfc.xref.Part1.29">9.8</a>, <a class="iref" href="#rfc.xref.Part1.30">9.8</a>, <a class="iref" href="#rfc.xref.Part1.31">9.8</a>, <a class="iref" href="#rfc.xref.Part1.32">9.9</a>, <a class="iref" href="#rfc.xref.Part1.33">9.9</a>, <a class="iref" href="#Part1"><b>13.1</b></a>, <a class="iref" href="#rfc.xref.Part1.34">A</a><ul class="ind">
    2736                         <li class="indline1"><em>Section 1.2</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part1.2">1.2</a></li>
    2737                         <li class="indline1"><em>Section 1.2.2</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part1.3">1.2.1</a>, <a class="iref" href="#rfc.xref.Part1.4">1.2.1</a>, <a class="iref" href="#rfc.xref.Part1.5">1.2.1</a>, <a class="iref" href="#rfc.xref.Part1.6">1.2.1</a>, <a class="iref" href="#rfc.xref.Part1.7">1.2.1</a>, <a class="iref" href="#rfc.xref.Part1.8">1.2.1</a></li>
    2738                         <li class="indline1"><em>Section 2.5</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part1.27">8.5.6</a></li>
    2739                         <li class="indline1"><em>Section 2.6</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part1.9">1.2.2</a>, <a class="iref" href="#rfc.xref.Part1.11">1.2.2</a>, <a class="iref" href="#rfc.xref.Part1.13">1.2.2</a>, <a class="iref" href="#rfc.xref.Part1.16">1.2.2</a></li>
    2740                         <li class="indline1"><em>Section 3.2</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part1.10">1.2.2</a>, <a class="iref" href="#rfc.xref.Part1.30">9.8</a>, <a class="iref" href="#rfc.xref.Part1.33">9.9</a></li>
    2741                         <li class="indline1"><em>Section 3.3</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part1.21">6</a></li>
    2742                         <li class="indline1"><em>Section 4.3</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part1.17">2</a>, <a class="iref" href="#rfc.xref.Part1.20">5</a>, <a class="iref" href="#rfc.xref.Part1.22">6.1</a></li>
    2743                         <li class="indline1"><em>Section 6.1</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part1.12">1.2.2</a></li>
    2744                         <li class="indline1"><em>Section 6.3</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part1.14">1.2.2</a>, <a class="iref" href="#rfc.xref.Part1.29">9.8</a>, <a class="iref" href="#rfc.xref.Part1.32">9.9</a></li>
    2745                         <li class="indline1"><em>Section 7.2.3</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part1.25">8.1.1</a>, <a class="iref" href="#rfc.xref.Part1.28">9.2</a></li>
    2746                         <li class="indline1"><em>Section 9.4</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part1.18">3</a></li>
    2747                         <li class="indline1"><em>Section 9.5</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part1.15">1.2.2</a>, <a class="iref" href="#rfc.xref.Part1.19">3</a></li>
    2748                         <li class="indline1"><em>Section 9.8</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part1.26">8.1.2</a></li>
    2749                         <li class="indline1"><em>Section 9.9</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part1.23">7.8</a>, <a class="iref" href="#rfc.xref.Part1.31">9.8</a>, <a class="iref" href="#rfc.xref.Part1.34">A</a></li>
    2750                         <li class="indline1"><em>Section 10.3.1</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part1.24">7.8</a></li>
    2751                      </ul>
    2752                   </li>
    2753                   <li class="indline1"><em>Part3</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part3.1">1.2.2</a>, <a class="iref" href="#rfc.xref.Part3.2">1.2.2</a>, <a class="iref" href="#rfc.xref.Part3.3">1.2.2</a>, <a class="iref" href="#rfc.xref.Part3.4">1.2.2</a>, <a class="iref" href="#rfc.xref.Part3.5">3</a>, <a class="iref" href="#rfc.xref.Part3.6">3</a>, <a class="iref" href="#rfc.xref.Part3.7">3</a>, <a class="iref" href="#rfc.xref.Part3.8">3</a>, <a class="iref" href="#rfc.xref.Part3.9">6</a>, <a class="iref" href="#rfc.xref.Part3.10">7.5</a>, <a class="iref" href="#rfc.xref.Part3.11">8.3.1</a>, <a class="iref" href="#rfc.xref.Part3.12">9.4</a>, <a class="iref" href="#Part3"><b>13.1</b></a><ul class="ind">
    2754                         <li class="indline1"><em>Section 5</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part3.11">8.3.1</a></li>
    2755                         <li class="indline1"><em>Section 6.1</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part3.1">1.2.2</a>, <a class="iref" href="#rfc.xref.Part3.5">3</a></li>
    2756                         <li class="indline1"><em>Section 6.2</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part3.2">1.2.2</a>, <a class="iref" href="#rfc.xref.Part3.6">3</a></li>
    2757                         <li class="indline1"><em>Section 6.3</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part3.3">1.2.2</a>, <a class="iref" href="#rfc.xref.Part3.7">3</a></li>
    2758                         <li class="indline1"><em>Section 6.4</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part3.4">1.2.2</a>, <a class="iref" href="#rfc.xref.Part3.8">3</a></li>
    2759                         <li class="indline1"><em>Section 6.7</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part3.10">7.5</a>, <a class="iref" href="#rfc.xref.Part3.12">9.4</a></li>
    2760                      </ul>
    2761                   </li>
    2762                   <li class="indline1"><em>Part4</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part4.1">1.2.2</a>, <a class="iref" href="#rfc.xref.Part4.2">1.2.2</a>, <a class="iref" href="#rfc.xref.Part4.3">1.2.2</a>, <a class="iref" href="#rfc.xref.Part4.4">1.2.2</a>, <a class="iref" href="#rfc.xref.Part4.5">1.2.2</a>, <a class="iref" href="#rfc.xref.Part4.6">3</a>, <a class="iref" href="#rfc.xref.Part4.7">3</a>, <a class="iref" href="#rfc.xref.Part4.8">3</a>, <a class="iref" href="#rfc.xref.Part4.9">3</a>, <a class="iref" href="#rfc.xref.Part4.10">4</a>, <a class="iref" href="#rfc.xref.Part4.11">4</a>, <a class="iref" href="#rfc.xref.Part4.12">4</a>, <a class="iref" href="#rfc.xref.Part4.13">5</a>, <a class="iref" href="#rfc.xref.Part4.14">8.2.2</a>, <a class="iref" href="#rfc.xref.Part4.15">8.3.5</a>, <a class="iref" href="#rfc.xref.Part4.16">8.4.13</a>, <a class="iref" href="#Part4"><b>13.1</b></a>, <a class="iref" href="#rfc.xref.Part4.17">C.2</a><ul class="ind">
    2763                         <li class="indline1"><em>Section 3</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part4.10">4</a></li>
    2764                         <li class="indline1"><em>Section 3.1</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part4.11">4</a>, <a class="iref" href="#rfc.xref.Part4.15">8.3.5</a></li>
    2765                         <li class="indline1"><em>Section 3.2</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part4.12">4</a>, <a class="iref" href="#rfc.xref.Part4.16">8.4.13</a></li>
    2766                         <li class="indline1"><em>Section 6.1</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part4.1">1.2.2</a>, <a class="iref" href="#rfc.xref.Part4.13">5</a>, <a class="iref" href="#rfc.xref.Part4.14">8.2.2</a></li>
    2767                         <li class="indline1"><em>Section 6.2</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part4.2">1.2.2</a>, <a class="iref" href="#rfc.xref.Part4.6">3</a></li>
    2768                         <li class="indline1"><em>Section 6.3</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part4.3">1.2.2</a>, <a class="iref" href="#rfc.xref.Part4.7">3</a></li>
    2769                         <li class="indline1"><em>Section 6.4</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part4.4">1.2.2</a>, <a class="iref" href="#rfc.xref.Part4.8">3</a></li>
    2770                         <li class="indline1"><em>Section 6.5</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part4.5">1.2.2</a>, <a class="iref" href="#rfc.xref.Part4.9">3</a></li>
    2771                      </ul>
    2772                   </li>
    2773                   <li class="indline1"><em>Part5</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part5.1">1.2.2</a>, <a class="iref" href="#rfc.xref.Part5.2">1.2.2</a>, <a class="iref" href="#rfc.xref.Part5.3">1.2.2</a>, <a class="iref" href="#rfc.xref.Part5.4">3</a>, <a class="iref" href="#rfc.xref.Part5.5">3</a>, <a class="iref" href="#rfc.xref.Part5.6">4</a>, <a class="iref" href="#rfc.xref.Part5.7">4</a>, <a class="iref" href="#rfc.xref.Part5.8">4</a>, <a class="iref" href="#rfc.xref.Part5.9">5</a>, <a class="iref" href="#rfc.xref.Part5.10">7.3</a>, <a class="iref" href="#rfc.xref.Part5.11">8.2.7</a>, <a class="iref" href="#rfc.xref.Part5.12">8.4.17</a>, <a class="iref" href="#rfc.xref.Part5.13">8.4.17</a>, <a class="iref" href="#Part5"><b>13.1</b></a><ul class="ind">
    2774                         <li class="indline1"><em>Section 3</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part5.6">4</a></li>
    2775                         <li class="indline1"><em>Section 3.1</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part5.7">4</a>, <a class="iref" href="#rfc.xref.Part5.11">8.2.7</a></li>
    2776                         <li class="indline1"><em>Section 3.2</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part5.8">4</a>, <a class="iref" href="#rfc.xref.Part5.13">8.4.17</a></li>
    2777                         <li class="indline1"><em>Section 5.1</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part5.1">1.2.2</a>, <a class="iref" href="#rfc.xref.Part5.9">5</a></li>
    2778                         <li class="indline1"><em>Section 5.3</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part5.2">1.2.2</a>, <a class="iref" href="#rfc.xref.Part5.4">3</a></li>
    2779                         <li class="indline1"><em>Section 5.4</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part5.3">1.2.2</a>, <a class="iref" href="#rfc.xref.Part5.5">3</a>, <a class="iref" href="#rfc.xref.Part5.10">7.3</a>, <a class="iref" href="#rfc.xref.Part5.12">8.4.17</a></li>
    2780                      </ul>
    2781                   </li>
    2782                   <li class="indline1"><em>Part6</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part6.1">1.2.2</a>, <a class="iref" href="#rfc.xref.Part6.2">1.2.2</a>, <a class="iref" href="#rfc.xref.Part6.3">5</a>, <a class="iref" href="#rfc.xref.Part6.4">5</a>, <a class="iref" href="#rfc.xref.Part6.5">6.1</a>, <a class="iref" href="#rfc.xref.Part6.6">7.3</a>, <a class="iref" href="#rfc.xref.Part6.7">7.4</a>, <a class="iref" href="#rfc.xref.Part6.8">7.5</a>, <a class="iref" href="#rfc.xref.Part6.9">8.2.1</a>, <a class="iref" href="#rfc.xref.Part6.10">8.2.4</a>, <a class="iref" href="#rfc.xref.Part6.11">8.2.7</a>, <a class="iref" href="#rfc.xref.Part6.12">8.3.1</a>, <a class="iref" href="#rfc.xref.Part6.13">8.3.2</a>, <a class="iref" href="#rfc.xref.Part6.14">8.4.11</a>, <a class="iref" href="#Part6"><b>13.1</b></a><ul class="ind">
    2783                         <li class="indline1"><em>Section 2.3.1</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part6.8">7.5</a></li>
    2784                         <li class="indline1"><em>Section 2.3.1.1</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part6.9">8.2.1</a>, <a class="iref" href="#rfc.xref.Part6.10">8.2.4</a>, <a class="iref" href="#rfc.xref.Part6.11">8.2.7</a>, <a class="iref" href="#rfc.xref.Part6.12">8.3.1</a>, <a class="iref" href="#rfc.xref.Part6.13">8.3.2</a>, <a class="iref" href="#rfc.xref.Part6.14">8.4.11</a></li>
    2785                         <li class="indline1"><em>Section 2.8</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part6.5">6.1</a></li>
    2786                         <li class="indline1"><em>Section 3.1</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part6.1">1.2.2</a>, <a class="iref" href="#rfc.xref.Part6.3">5</a></li>
    2787                         <li class="indline1"><em>Section 3.5</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part6.2">1.2.2</a>, <a class="iref" href="#rfc.xref.Part6.4">5</a></li>
    2788                      </ul>
    2789                   </li>
    2790                   <li class="indline1"><em>Part7</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part7.1">1.2.2</a>, <a class="iref" href="#rfc.xref.Part7.2">1.2.2</a>, <a class="iref" href="#rfc.xref.Part7.3">1.2.2</a>, <a class="iref" href="#rfc.xref.Part7.4">1.2.2</a>, <a class="iref" href="#rfc.xref.Part7.5">3</a>, <a class="iref" href="#rfc.xref.Part7.6">3</a>, <a class="iref" href="#rfc.xref.Part7.7">4</a>, <a class="iref" href="#rfc.xref.Part7.8">4</a>, <a class="iref" href="#rfc.xref.Part7.9">4</a>, <a class="iref" href="#rfc.xref.Part7.10">5</a>, <a class="iref" href="#rfc.xref.Part7.11">5</a>, <a class="iref" href="#rfc.xref.Part7.12">8.4.2</a>, <a class="iref" href="#rfc.xref.Part7.13">8.4.8</a>, <a class="iref" href="#Part7"><b>13.1</b></a><ul class="ind">
    2791                         <li class="indline1"><em>Section 3</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part7.7">4</a></li>
    2792                         <li class="indline1"><em>Section 3.1</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part7.8">4</a>, <a class="iref" href="#rfc.xref.Part7.12">8.4.2</a></li>
    2793                         <li class="indline1"><em>Section 3.2</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part7.9">4</a>, <a class="iref" href="#rfc.xref.Part7.13">8.4.8</a></li>
    2794                         <li class="indline1"><em>Section 4.1</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part7.1">1.2.2</a>, <a class="iref" href="#rfc.xref.Part7.5">3</a></li>
    2795                         <li class="indline1"><em>Section 4.2</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part7.2">1.2.2</a>, <a class="iref" href="#rfc.xref.Part7.10">5</a></li>
    2796                         <li class="indline1"><em>Section 4.3</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part7.3">1.2.2</a>, <a class="iref" href="#rfc.xref.Part7.6">3</a></li>
    2797                         <li class="indline1"><em>Section 4.4</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.Part7.4">1.2.2</a>, <a class="iref" href="#rfc.xref.Part7.11">5</a></li>
    2798                      </ul>
    2799                   </li>
    2800                   <li class="indline1">POST method&nbsp;&nbsp;<a class="iref" href="#rfc.xref.POST.1">2</a>, <a class="iref" href="#rfc.iref.p.1"><b>7.5</b></a>, <a class="iref" href="#rfc.xref.POST.2">10.1</a>, <a class="iref" href="#rfc.xref.POST.3">A</a></li>
    2801                   <li class="indline1">PUT method&nbsp;&nbsp;<a class="iref" href="#rfc.xref.PUT.1">2</a>, <a class="iref" href="#rfc.iref.p.2"><b>7.6</b></a>, <a class="iref" href="#rfc.xref.PUT.2">10.1</a></li>
    2802                </ul>
    2803             </li>
    2804             <li class="indline0"><a id="rfc.index.R" href="#rfc.index.R"><b>R</b></a><ul class="ind">
    2805                   <li class="indline1">Referer header&nbsp;&nbsp;<a class="iref" href="#rfc.xref.header.referer.1">3</a>, <a class="iref" href="#rfc.iref.r.1"><b>9.6</b></a>, <a class="iref" href="#rfc.xref.header.referer.2">10.3</a>, <a class="iref" href="#rfc.xref.header.referer.3">A</a></li>
    2806                   <li class="indline1">Retry-After header&nbsp;&nbsp;<a class="iref" href="#rfc.xref.header.retry-after.1">5</a>, <a class="iref" href="#rfc.iref.r.2"><b>9.7</b></a>, <a class="iref" href="#rfc.xref.header.retry-after.2">10.3</a></li>
    2807                   <li class="indline1"><em>RFC1945</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.RFC1945.1">8.3.3</a>, <a class="iref" href="#RFC1945"><b>13.2</b></a><ul class="ind">
    2808                         <li class="indline1"><em>Section 9.3</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.RFC1945.1">8.3.3</a></li>
    2809                      </ul>
    2810                   </li>
    2811                   <li class="indline1"><em>RFC2068</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.RFC2068.1">8.3</a>, <a class="iref" href="#rfc.xref.RFC2068.2">8.3.3</a>, <a class="iref" href="#RFC2068"><b>13.2</b></a><ul class="ind">
    2812                         <li class="indline1"><em>Section 10.3</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.RFC2068.1">8.3</a></li>
    2813                         <li class="indline1"><em>Section 10.3.3</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.RFC2068.2">8.3.3</a></li>
    2814                      </ul>
    2815                   </li>
    2816                   <li class="indline1"><em>RFC2119</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.RFC2119.1">1.1</a>, <a class="iref" href="#RFC2119"><b>13.1</b></a></li>
    2817                   <li class="indline1"><em>RFC2616</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.RFC2616.1">1</a>, <a class="iref" href="#rfc.xref.RFC2616.2">8.3.3</a>, <a class="iref" href="#RFC2616"><b>13.2</b></a>, <a class="iref" href="#rfc.xref.RFC2616.3">C.1</a><ul class="ind">
    2818                         <li class="indline1"><em>Section 10.3.3</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.RFC2616.2">8.3.3</a></li>
    2819                      </ul>
    2820                   </li>
    2821                   <li class="indline1"><em>RFC2817</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.RFC2817.1">7.9</a>, <a class="iref" href="#rfc.xref.RFC2817.2">10.2</a>, <a class="iref" href="#RFC2817"><b>13.2</b></a>, <a class="iref" href="#rfc.xref.RFC2817.3">A</a><ul class="ind">
    2822                         <li class="indline1"><em>Section 7.1</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.RFC2817.2">10.2</a>, <a class="iref" href="#rfc.xref.RFC2817.3">A</a></li>
    2823                      </ul>
    2824                   </li>
    2825                   <li class="indline1"><em>RFC3864</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.RFC3864.1">10.3</a>, <a class="iref" href="#RFC3864"><b>13.2</b></a></li>
    2826                   <li class="indline1"><em>RFC3986</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.RFC3986.1">9.4</a>, <a class="iref" href="#rfc.xref.RFC3986.2">9.4</a>, <a class="iref" href="#RFC3986"><b>13.1</b></a><ul class="ind">
    2827                         <li class="indline1"><em>Section 4.2</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.RFC3986.1">9.4</a></li>
    2828                         <li class="indline1"><em>Section 5</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.RFC3986.2">9.4</a></li>
    2829                      </ul>
    2830                   </li>
    2831                   <li class="indline1"><em>RFC5226</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.RFC5226.1">2.1</a>, <a class="iref" href="#rfc.xref.RFC5226.2">4.1</a>, <a class="iref" href="#RFC5226"><b>13.2</b></a><ul class="ind">
    2832                         <li class="indline1"><em>Section 4.1</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.RFC5226.1">2.1</a>, <a class="iref" href="#rfc.xref.RFC5226.2">4.1</a></li>
    2833                      </ul>
    2834                   </li>
    2835                   <li class="indline1"><em>RFC5234</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.RFC5234.1">1.2</a>, <a class="iref" href="#rfc.xref.RFC5234.2">1.2</a>, <a class="iref" href="#RFC5234"><b>13.1</b></a><ul class="ind">
    2836                         <li class="indline1"><em>Appendix B.1</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.RFC5234.2">1.2</a></li>
    2837                      </ul>
    2838                   </li>
    2839                   <li class="indline1"><em>RFC5322</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.RFC5322.1">9.3</a>, <a class="iref" href="#rfc.xref.RFC5322.2">9.3</a>, <a class="iref" href="#RFC5322"><b>13.2</b></a><ul class="ind">
    2840                         <li class="indline1"><em>Section 3.4</em>&nbsp;&nbsp;<a class="iref" href="#rfc.xref.RFC5322.1">9.3</a>, <a class="iref" href="#rfc.xref.RFC5322.2">9.3</a></li>
    2841                      </ul>
    2842                   </li>
    2843                </ul>
    2844             </li>
    2845             <li class="indline0"><a id="rfc.index.S" href="#rfc.index.S"><b>S</b></a><ul class="ind">
    2846                   <li class="indline1">Safe Methods&nbsp;&nbsp;<a class="iref" href="#rfc.iref.s.1"><b>7.1.1</b></a></li>
    2847                   <li class="indline1">Server header&nbsp;&nbsp;<a class="iref" href="#rfc.xref.header.server.1">5</a>, <a class="iref" href="#rfc.iref.s.43"><b>9.8</b></a>, <a class="iref" href="#rfc.xref.header.server.2">10.3</a>, <a class="iref" href="#rfc.xref.header.server.3">11.1</a>, <a class="iref" href="#rfc.xref.header.server.4">A</a></li>
    2848                   <li class="indline1">Status Codes&nbsp;&nbsp;
    2849                      <ul class="ind">
    2850                         <li class="indline1">100 Continue&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.100.1">4</a>, <a class="iref" href="#rfc.iref.s.2"><b>8.1.1</b></a>, <a class="iref" href="#rfc.xref.status.100.2">10.2</a></li>
    2851                         <li class="indline1">101 Switching Protocols&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.101.1">4</a>, <a class="iref" href="#rfc.iref.s.3"><b>8.1.2</b></a>, <a class="iref" href="#rfc.xref.status.101.2">10.2</a></li>
    2852                         <li class="indline1">200 OK&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.200.1">4</a>, <a class="iref" href="#rfc.iref.s.4"><b>8.2.1</b></a>, <a class="iref" href="#rfc.xref.status.200.2">10.2</a></li>
    2853                         <li class="indline1">201 Created&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.201.1">4</a>, <a class="iref" href="#rfc.iref.s.5"><b>8.2.2</b></a>, <a class="iref" href="#rfc.xref.status.201.2">10.2</a></li>
    2854                         <li class="indline1">202 Accepted&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.202.1">4</a>, <a class="iref" href="#rfc.iref.s.6"><b>8.2.3</b></a>, <a class="iref" href="#rfc.xref.status.202.2">10.2</a></li>
    2855                         <li class="indline1">203 Non-Authoritative Information&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.203.1">4</a>, <a class="iref" href="#rfc.iref.s.7"><b>8.2.4</b></a>, <a class="iref" href="#rfc.xref.status.203.2">10.2</a></li>
    2856                         <li class="indline1">204 No Content&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.204.1">4</a>, <a class="iref" href="#rfc.iref.s.8"><b>8.2.5</b></a>, <a class="iref" href="#rfc.xref.status.204.2">10.2</a></li>
    2857                         <li class="indline1">205 Reset Content&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.205.1">4</a>, <a class="iref" href="#rfc.iref.s.9"><b>8.2.6</b></a>, <a class="iref" href="#rfc.xref.status.205.2">10.2</a></li>
    2858                         <li class="indline1">206 Partial Content&nbsp;&nbsp;<a class="iref" href="#rfc.iref.s.10"><b>8.2.7</b></a></li>
    2859                         <li class="indline1">300 Multiple Choices&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.300.1">4</a>, <a class="iref" href="#rfc.iref.s.11"><b>8.3.1</b></a>, <a class="iref" href="#rfc.xref.status.300.2">10.2</a></li>
    2860                         <li class="indline1">301 Moved Permanently&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.301.1">4</a>, <a class="iref" href="#rfc.iref.s.12"><b>8.3.2</b></a>, <a class="iref" href="#rfc.xref.status.301.2">10.2</a>, <a class="iref" href="#rfc.xref.status.301.3">A</a></li>
    2861                         <li class="indline1">302 Found&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.302.1">4</a>, <a class="iref" href="#rfc.iref.s.13"><b>8.3.3</b></a>, <a class="iref" href="#rfc.xref.status.302.2">10.2</a>, <a class="iref" href="#rfc.xref.status.302.3">A</a></li>
    2862                         <li class="indline1">303 See Other&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.303.1">4</a>, <a class="iref" href="#rfc.xref.status.303.2">8.3.3</a>, <a class="iref" href="#rfc.iref.s.14"><b>8.3.4</b></a>, <a class="iref" href="#rfc.xref.status.303.3">10.2</a></li>
    2863                         <li class="indline1">304 Not Modified&nbsp;&nbsp;<a class="iref" href="#rfc.iref.s.15"><b>8.3.5</b></a></li>
    2864                         <li class="indline1">305 Use Proxy&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.305.1">4</a>, <a class="iref" href="#rfc.iref.s.16"><b>8.3.6</b></a>, <a class="iref" href="#rfc.xref.status.305.2">10.2</a>, <a class="iref" href="#rfc.xref.status.305.3">A</a></li>
    2865                         <li class="indline1">306 (Unused)&nbsp;&nbsp;<a class="iref" href="#rfc.iref.s.17"><b>8.3.7</b></a>, <a class="iref" href="#rfc.xref.status.306.1">10.2</a></li>
    2866                         <li class="indline1">307 Temporary Redirect&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.307.1">4</a>, <a class="iref" href="#rfc.xref.status.307.2">8.3.3</a>, <a class="iref" href="#rfc.iref.s.18"><b>8.3.8</b></a>, <a class="iref" href="#rfc.xref.status.307.3">10.2</a>, <a class="iref" href="#rfc.xref.status.307.4">A</a></li>
    2867                         <li class="indline1">400 Bad Request&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.400.1">4</a>, <a class="iref" href="#rfc.iref.s.19"><b>8.4.1</b></a>, <a class="iref" href="#rfc.xref.status.400.2">10.2</a></li>
    2868                         <li class="indline1">401 Unauthorized&nbsp;&nbsp;<a class="iref" href="#rfc.iref.s.20"><b>8.4.2</b></a></li>
    2869                         <li class="indline1">402 Payment Required&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.402.1">4</a>, <a class="iref" href="#rfc.iref.s.21"><b>8.4.3</b></a>, <a class="iref" href="#rfc.xref.status.402.2">10.2</a></li>
    2870                         <li class="indline1">403 Forbidden&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.403.1">4</a>, <a class="iref" href="#rfc.iref.s.22"><b>8.4.4</b></a>, <a class="iref" href="#rfc.xref.status.403.2">10.2</a></li>
    2871                         <li class="indline1">404 Not Found&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.404.1">4</a>, <a class="iref" href="#rfc.iref.s.23"><b>8.4.5</b></a>, <a class="iref" href="#rfc.xref.status.404.2">10.2</a></li>
    2872                         <li class="indline1">405 Method Not Allowed&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.405.1">4</a>, <a class="iref" href="#rfc.iref.s.24"><b>8.4.6</b></a>, <a class="iref" href="#rfc.xref.status.405.2">10.2</a></li>
    2873                         <li class="indline1">406 Not Acceptable&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.406.1">4</a>, <a class="iref" href="#rfc.iref.s.25"><b>8.4.7</b></a>, <a class="iref" href="#rfc.xref.status.406.2">10.2</a></li>
    2874                         <li class="indline1">407 Proxy Authentication Required&nbsp;&nbsp;<a class="iref" href="#rfc.iref.s.26"><b>8.4.8</b></a>, <a class="iref" href="#rfc.xref.status.407.1">10.2</a></li>
    2875                         <li class="indline1">408 Request Timeout&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.408.1">4</a>, <a class="iref" href="#rfc.iref.s.27"><b>8.4.9</b></a>, <a class="iref" href="#rfc.xref.status.408.2">10.2</a></li>
    2876                         <li class="indline1">409 Conflict&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.409.1">4</a>, <a class="iref" href="#rfc.iref.s.28"><b>8.4.10</b></a>, <a class="iref" href="#rfc.xref.status.409.2">10.2</a></li>
    2877                         <li class="indline1">410 Gone&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.410.1">4</a>, <a class="iref" href="#rfc.iref.s.29"><b>8.4.11</b></a>, <a class="iref" href="#rfc.xref.status.410.2">10.2</a></li>
    2878                         <li class="indline1">411 Length Required&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.411.1">4</a>, <a class="iref" href="#rfc.iref.s.30"><b>8.4.12</b></a>, <a class="iref" href="#rfc.xref.status.411.2">10.2</a></li>
    2879                         <li class="indline1">412 Precondition Failed&nbsp;&nbsp;<a class="iref" href="#rfc.iref.s.31"><b>8.4.13</b></a></li>
    2880                         <li class="indline1">413 Request Entity Too Large&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.413.1">4</a>, <a class="iref" href="#rfc.iref.s.32"><b>8.4.14</b></a>, <a class="iref" href="#rfc.xref.status.413.2">10.2</a></li>
    2881                         <li class="indline1">414 URI Too Long&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.414.1">4</a>, <a class="iref" href="#rfc.iref.s.33"><b>8.4.15</b></a>, <a class="iref" href="#rfc.xref.status.414.2">10.2</a></li>
    2882                         <li class="indline1">415 Unsupported Media Type&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.415.1">4</a>, <a class="iref" href="#rfc.iref.s.34"><b>8.4.16</b></a>, <a class="iref" href="#rfc.xref.status.415.2">10.2</a></li>
    2883                         <li class="indline1">416 Requested Range Not Satisfiable&nbsp;&nbsp;<a class="iref" href="#rfc.iref.s.35"><b>8.4.17</b></a></li>
    2884                         <li class="indline1">417 Expectation Failed&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.417.1">4</a>, <a class="iref" href="#rfc.iref.s.36"><b>8.4.18</b></a>, <a class="iref" href="#rfc.xref.status.417.2">10.2</a></li>
    2885                         <li class="indline1">500 Internal Server Error&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.500.1">4</a>, <a class="iref" href="#rfc.iref.s.37"><b>8.5.1</b></a>, <a class="iref" href="#rfc.xref.status.500.2">10.2</a></li>
    2886                         <li class="indline1">501 Not Implemented&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.501.1">4</a>, <a class="iref" href="#rfc.iref.s.38"><b>8.5.2</b></a>, <a class="iref" href="#rfc.xref.status.501.2">10.2</a></li>
    2887                         <li class="indline1">502 Bad Gateway&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.502.1">4</a>, <a class="iref" href="#rfc.iref.s.39"><b>8.5.3</b></a>, <a class="iref" href="#rfc.xref.status.502.2">10.2</a></li>
    2888                         <li class="indline1">503 Service Unavailable&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.503.1">4</a>, <a class="iref" href="#rfc.iref.s.40"><b>8.5.4</b></a>, <a class="iref" href="#rfc.xref.status.503.2">10.2</a></li>
    2889                         <li class="indline1">504 Gateway Timeout&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.504.1">4</a>, <a class="iref" href="#rfc.iref.s.41"><b>8.5.5</b></a>, <a class="iref" href="#rfc.xref.status.504.2">10.2</a></li>
    2890                         <li class="indline1">505 HTTP Version Not Supported&nbsp;&nbsp;<a class="iref" href="#rfc.xref.status.505.1">4</a>, <a class="iref" href="#rfc.iref.s.42"><b>8.5.6</b></a>, <a class="iref" href="#rfc.xref.status.505.2">10.2</a></li>
    2891                      </ul>
    2892                   </li>
    2893                </ul>
    2894             </li>
    2895             <li class="indline0"><a id="rfc.index.T" href="#rfc.index.T"><b>T</b></a><ul class="ind">
    2896                   <li class="indline1">TRACE method&nbsp;&nbsp;<a class="iref" href="#rfc.xref.TRACE.1">2</a>, <a class="iref" href="#rfc.iref.t.1"><b>7.8</b></a>, <a class="iref" href="#rfc.xref.TRACE.2">9.5</a>, <a class="iref" href="#rfc.xref.TRACE.3">10.1</a>, <a class="iref" href="#rfc.xref.TRACE.4">11.1</a></li>
    2897                </ul>
    2898             </li>
    2899             <li class="indline0"><a id="rfc.index.U" href="#rfc.index.U"><b>U</b></a><ul class="ind">
    2900                   <li class="indline1">User-Agent header&nbsp;&nbsp;<a class="iref" href="#rfc.xref.header.user-agent.1">3</a>, <a class="iref" href="#rfc.iref.u.1"><b>9.9</b></a>, <a class="iref" href="#rfc.xref.header.user-agent.2">10.3</a>, <a class="iref" href="#rfc.xref.header.user-agent.3">11.1</a></li>
    2901                </ul>
    2902             </li>
    2903          </ul>
    2904       </div>
    2905    </body>
    2906 </html>
  • draft-ietf-httpbis/latest/p2-semantics.xml

    r1030 r1032  
    22842284  <x:anchor-alias value="User-Agent"/>
    22852285  <x:anchor-alias value="User-Agent-v"/>
    2286 <t>
    2287    The "User-Agent" request-header field contains information about the
    2288    user agent originating the request. This is for statistical purposes,
    2289    the tracing of protocol violations, and automated recognition of user
    2290    agents for the sake of tailoring responses to avoid particular user
    2291    agent limitations.
    2292 </t>
    2293 <t>
    2294    User agents &SHOULD; include this field with requests. The field can contain
    2295    multiple product tokens (&product-tokens;) and comments (&header-fields;)
    2296    identifying the agent and any subproducts which form a significant part of
    2297    the user agent. By convention, the product tokens are listed in order of
    2298    their significance for identifying the application.
    2299 </t>
     2286
     2287  <t>The "User-Agent" request-header field contains information about the user
     2288  agent originating the request. User agents &SHOULD; include this field with
     2289  requests.</t>
     2290
     2291  <t>Typically, it is used for statistical purposes, the tracing of protocol
     2292  violations, and tailoring responses to avoid particular user agent
     2293  limitations.</t>
     2294
     2295  <t>The field can contain multiple product tokens (&product-tokens;)
     2296  and comments (&header-fields;) identifying the agent and its
     2297  significant subproducts. By convention, the product tokens are listed in
     2298  order of their significance for identifying the application.</t>
     2299
     2300  <t>Because this field is usually sent on every request a user agent makes,
     2301  implementations are encouraged not to include needlessly fine-grained
     2302  detail, and to limit (or even prohibit) the addition of subproducts by third
     2303  parties. Overly long and detailed User-Agent field values make requests
     2304  larger and can also be used to identify ("fingerprint") the user against
     2305  their wishes.</t>
     2306
     2307  <t>Likewise, implementations are encouraged not to use the product tokens of
     2308  other implementations in order to declare compatibility with them, as this
     2309  circumvents the purpose of the field. Finally, they are encouraged not to
     2310  use comments to identify products; doing so makes the field value more
     2311  difficult to parse.</t>
     2312
    23002313<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
    23012314  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
     
    27042717   Referer information.
    27052718</t>
    2706 <t>
    2707    The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
    2708    fields can sometimes be used to determine that a specific client or
    2709    server have a particular security hole which might be exploited.
    2710    Unfortunately, this same information is often used for other valuable
    2711    purposes for which HTTP currently has no better mechanism.
    2712 </t>
     2719
     2720  <t>The User-Agent (<xref target="header.user-agent"/>) or Server (<xref
     2721  target="header.server"/>) header fields can sometimes be used to determine
     2722  that a specific client or server have a particular security hole which might
     2723  be exploited. Unfortunately, this same information is often used for other
     2724  valuable purposes for which HTTP currently has no better mechanism.</t>
     2725
     2726  <t>Furthermore, the User-Agent header field may contain enough entropy to be
     2727  used, possibly in conjunction with other material, to uniquely identify the
     2728  user.</t>
     2729
    27132730<t>
    27142731   Some methods, like TRACE (<xref target="TRACE"/>), expose information
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