Changeset 389 for draft-ietf-httpbis
- Timestamp:
- 15/11/08 00:20:37 (14 years ago)
- Location:
- draft-ietf-httpbis/latest
- Files:
-
- 2 edited
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draft-ietf-httpbis/latest/p1-messaging.html
r385 r389 365 365 <link rel="Index" href="#rfc.index"> 366 366 <link rel="Chapter" title="1 Introduction" href="#rfc.section.1"> 367 <link rel="Chapter" title="2 Notational Conventions and Generic Grammar" href="#rfc.section.2"> 368 <link rel="Chapter" title="3 Protocol Parameters" href="#rfc.section.3"> 369 <link rel="Chapter" title="4 HTTP Message" href="#rfc.section.4"> 370 <link rel="Chapter" title="5 Request" href="#rfc.section.5"> 371 <link rel="Chapter" title="6 Response" href="#rfc.section.6"> 372 <link rel="Chapter" title="7 Connections" href="#rfc.section.7"> 373 <link rel="Chapter" title="8 Header Field Definitions" href="#rfc.section.8"> 374 <link rel="Chapter" title="9 IANA Considerations" href="#rfc.section.9"> 375 <link rel="Chapter" title="10 Security Considerations" href="#rfc.section.10"> 376 <link rel="Chapter" title="11 Acknowledgments" href="#rfc.section.11"> 377 <link rel="Chapter" href="#rfc.section.12" title="12 References"> 367 <link rel="Chapter" title="2 Protocol Parameters" href="#rfc.section.2"> 368 <link rel="Chapter" title="3 HTTP Message" href="#rfc.section.3"> 369 <link rel="Chapter" title="4 Request" href="#rfc.section.4"> 370 <link rel="Chapter" title="5 Response" href="#rfc.section.5"> 371 <link rel="Chapter" title="6 Connections" href="#rfc.section.6"> 372 <link rel="Chapter" title="7 Header Field Definitions" href="#rfc.section.7"> 373 <link rel="Chapter" title="8 IANA Considerations" href="#rfc.section.8"> 374 <link rel="Chapter" title="9 Security Considerations" href="#rfc.section.9"> 375 <link rel="Chapter" title="10 Acknowledgments" href="#rfc.section.10"> 376 <link rel="Chapter" href="#rfc.section.11" title="11 References"> 378 377 <link rel="Appendix" title="A Tolerant Applications" href="#rfc.section.A"> 379 378 <link rel="Appendix" title="B Compatibility with Previous Versions" href="#rfc.section.B"> … … 476 475 <tr> 477 476 <td class="header left"></td> 478 <td class="header right">November 1 4, 2008</td>477 <td class="header right">November 15, 2008</td> 479 478 </tr> 480 479 </table> … … 516 515 <li class="tocline0">1. <a href="#introduction">Introduction</a><ul class="toc"> 517 516 <li class="tocline1">1.1 <a href="#intro.requirements">Requirements</a></li> 518 <li class="tocline1">1.2 <a href="#intro.overall.operation">Overall Operation</a></li> 519 </ul> 520 </li> 521 <li class="tocline0">2. <a href="#notation">Notational Conventions and Generic Grammar</a><ul class="toc"> 522 <li class="tocline1">2.1 <a href="#notation.abnf">ABNF Extension: #rule</a></li> 523 <li class="tocline1">2.2 <a href="#basic.rules">Basic Rules</a></li> 524 <li class="tocline1">2.3 <a href="#abnf.dependencies">ABNF Rules defined in other Parts of the Specification</a></li> 525 </ul> 526 </li> 527 <li class="tocline0">3. <a href="#protocol.parameters">Protocol Parameters</a><ul class="toc"> 528 <li class="tocline1">3.1 <a href="#http.version">HTTP Version</a></li> 529 <li class="tocline1">3.2 <a href="#uri">Uniform Resource Identifiers</a><ul class="toc"> 530 <li class="tocline1">3.2.1 <a href="#http.uri">http URI scheme</a></li> 531 <li class="tocline1">3.2.2 <a href="#uri.comparison">URI Comparison</a></li> 517 <li class="tocline1">1.2 <a href="#notation">Notational Conventions and Generic Grammar</a><ul class="toc"> 518 <li class="tocline1">1.2.1 <a href="#notation.abnf">ABNF Extension: #rule</a></li> 519 <li class="tocline1">1.2.2 <a href="#basic.rules">Basic Rules</a></li> 520 <li class="tocline1">1.2.3 <a href="#abnf.dependencies">ABNF Rules defined in other Parts of the Specification</a></li> 532 521 </ul> 533 522 </li> 534 <li class="tocline1">3.3 <a href="#date.time.formats">Date/Time Formats</a><ul class="toc"> 535 <li class="tocline1">3.3.1 <a href="#full.date">Full Date</a></li> 523 <li class="tocline1">1.3 <a href="#intro.overall.operation">Overall Operation</a></li> 524 </ul> 525 </li> 526 <li class="tocline0">2. <a href="#protocol.parameters">Protocol Parameters</a><ul class="toc"> 527 <li class="tocline1">2.1 <a href="#http.version">HTTP Version</a></li> 528 <li class="tocline1">2.2 <a href="#uri">Uniform Resource Identifiers</a><ul class="toc"> 529 <li class="tocline1">2.2.1 <a href="#http.uri">http URI scheme</a></li> 530 <li class="tocline1">2.2.2 <a href="#uri.comparison">URI Comparison</a></li> 536 531 </ul> 537 532 </li> 538 <li class="tocline1"> 3.4 <a href="#transfer.codings">Transfer Codings</a><ul class="toc">539 <li class="tocline1"> 3.4.1 <a href="#chunked.transfer.encoding">Chunked Transfer Coding</a></li>533 <li class="tocline1">2.3 <a href="#date.time.formats">Date/Time Formats</a><ul class="toc"> 534 <li class="tocline1">2.3.1 <a href="#full.date">Full Date</a></li> 540 535 </ul> 541 536 </li> 542 <li class="tocline1">3.5 <a href="#product.tokens">Product Tokens</a></li> 543 </ul> 544 </li> 545 <li class="tocline0">4. <a href="#http.message">HTTP Message</a><ul class="toc"> 546 <li class="tocline1">4.1 <a href="#message.types">Message Types</a></li> 547 <li class="tocline1">4.2 <a href="#message.headers">Message Headers</a></li> 548 <li class="tocline1">4.3 <a href="#message.body">Message Body</a></li> 549 <li class="tocline1">4.4 <a href="#message.length">Message Length</a></li> 550 <li class="tocline1">4.5 <a href="#general.header.fields">General Header Fields</a></li> 551 </ul> 552 </li> 553 <li class="tocline0">5. <a href="#request">Request</a><ul class="toc"> 554 <li class="tocline1">5.1 <a href="#request-line">Request-Line</a><ul class="toc"> 555 <li class="tocline1">5.1.1 <a href="#method">Method</a></li> 556 <li class="tocline1">5.1.2 <a href="#request-uri">Request-URI</a></li> 537 <li class="tocline1">2.4 <a href="#transfer.codings">Transfer Codings</a><ul class="toc"> 538 <li class="tocline1">2.4.1 <a href="#chunked.transfer.encoding">Chunked Transfer Coding</a></li> 557 539 </ul> 558 540 </li> 559 <li class="tocline1"> 5.2 <a href="#the.resource.identified.by.a.request">The Resource Identified by a Request</a></li>541 <li class="tocline1">2.5 <a href="#product.tokens">Product Tokens</a></li> 560 542 </ul> 561 543 </li> 562 <li class="tocline0">6. <a href="#response">Response</a><ul class="toc"> 563 <li class="tocline1">6.1 <a href="#status-line">Status-Line</a><ul class="toc"> 564 <li class="tocline1">6.1.1 <a href="#status.code.and.reason.phrase">Status Code and Reason Phrase</a></li> 544 <li class="tocline0">3. <a href="#http.message">HTTP Message</a><ul class="toc"> 545 <li class="tocline1">3.1 <a href="#message.types">Message Types</a></li> 546 <li class="tocline1">3.2 <a href="#message.headers">Message Headers</a></li> 547 <li class="tocline1">3.3 <a href="#message.body">Message Body</a></li> 548 <li class="tocline1">3.4 <a href="#message.length">Message Length</a></li> 549 <li class="tocline1">3.5 <a href="#general.header.fields">General Header Fields</a></li> 550 </ul> 551 </li> 552 <li class="tocline0">4. <a href="#request">Request</a><ul class="toc"> 553 <li class="tocline1">4.1 <a href="#request-line">Request-Line</a><ul class="toc"> 554 <li class="tocline1">4.1.1 <a href="#method">Method</a></li> 555 <li class="tocline1">4.1.2 <a href="#request-uri">Request-URI</a></li> 556 </ul> 557 </li> 558 <li class="tocline1">4.2 <a href="#the.resource.identified.by.a.request">The Resource Identified by a Request</a></li> 559 </ul> 560 </li> 561 <li class="tocline0">5. <a href="#response">Response</a><ul class="toc"> 562 <li class="tocline1">5.1 <a href="#status-line">Status-Line</a><ul class="toc"> 563 <li class="tocline1">5.1.1 <a href="#status.code.and.reason.phrase">Status Code and Reason Phrase</a></li> 565 564 </ul> 566 565 </li> 567 566 </ul> 568 567 </li> 569 <li class="tocline0"> 7. <a href="#connections">Connections</a><ul class="toc">570 <li class="tocline1"> 7.1 <a href="#persistent.connections">Persistent Connections</a><ul class="toc">571 <li class="tocline1"> 7.1.1 <a href="#persistent.purpose">Purpose</a></li>572 <li class="tocline1"> 7.1.2 <a href="#persistent.overall">Overall Operation</a><ul class="toc">573 <li class="tocline1"> 7.1.2.1 <a href="#persistent.negotiation">Negotiation</a></li>574 <li class="tocline1"> 7.1.2.2 <a href="#pipelining">Pipelining</a></li>568 <li class="tocline0">6. <a href="#connections">Connections</a><ul class="toc"> 569 <li class="tocline1">6.1 <a href="#persistent.connections">Persistent Connections</a><ul class="toc"> 570 <li class="tocline1">6.1.1 <a href="#persistent.purpose">Purpose</a></li> 571 <li class="tocline1">6.1.2 <a href="#persistent.overall">Overall Operation</a><ul class="toc"> 572 <li class="tocline1">6.1.2.1 <a href="#persistent.negotiation">Negotiation</a></li> 573 <li class="tocline1">6.1.2.2 <a href="#pipelining">Pipelining</a></li> 575 574 </ul> 576 575 </li> 577 <li class="tocline1"> 7.1.3 <a href="#persistent.proxy">Proxy Servers</a></li>578 <li class="tocline1"> 7.1.4 <a href="#persistent.practical">Practical Considerations</a></li>576 <li class="tocline1">6.1.3 <a href="#persistent.proxy">Proxy Servers</a></li> 577 <li class="tocline1">6.1.4 <a href="#persistent.practical">Practical Considerations</a></li> 579 578 </ul> 580 579 </li> 581 <li class="tocline1"> 7.2 <a href="#message.transmission.requirements">Message Transmission Requirements</a><ul class="toc">582 <li class="tocline1"> 7.2.1 <a href="#persistent.flow">Persistent Connections and Flow Control</a></li>583 <li class="tocline1"> 7.2.2 <a href="#persistent.monitor">Monitoring Connections for Error Status Messages</a></li>584 <li class="tocline1"> 7.2.3 <a href="#use.of.the.100.status">Use of the 100 (Continue) Status</a></li>585 <li class="tocline1"> 7.2.4 <a href="#connection.premature">Client Behavior if Server Prematurely Closes Connection</a></li>580 <li class="tocline1">6.2 <a href="#message.transmission.requirements">Message Transmission Requirements</a><ul class="toc"> 581 <li class="tocline1">6.2.1 <a href="#persistent.flow">Persistent Connections and Flow Control</a></li> 582 <li class="tocline1">6.2.2 <a href="#persistent.monitor">Monitoring Connections for Error Status Messages</a></li> 583 <li class="tocline1">6.2.3 <a href="#use.of.the.100.status">Use of the 100 (Continue) Status</a></li> 584 <li class="tocline1">6.2.4 <a href="#connection.premature">Client Behavior if Server Prematurely Closes Connection</a></li> 586 585 </ul> 587 586 </li> 588 587 </ul> 589 588 </li> 590 <li class="tocline0"> 8. <a href="#header.fields">Header Field Definitions</a><ul class="toc">591 <li class="tocline1"> 8.1 <a href="#header.connection">Connection</a></li>592 <li class="tocline1"> 8.2 <a href="#header.content-length">Content-Length</a></li>593 <li class="tocline1"> 8.3 <a href="#header.date">Date</a><ul class="toc">594 <li class="tocline1"> 8.3.1 <a href="#clockless.origin.server.operation">Clockless Origin Server Operation</a></li>589 <li class="tocline0">7. <a href="#header.fields">Header Field Definitions</a><ul class="toc"> 590 <li class="tocline1">7.1 <a href="#header.connection">Connection</a></li> 591 <li class="tocline1">7.2 <a href="#header.content-length">Content-Length</a></li> 592 <li class="tocline1">7.3 <a href="#header.date">Date</a><ul class="toc"> 593 <li class="tocline1">7.3.1 <a href="#clockless.origin.server.operation">Clockless Origin Server Operation</a></li> 595 594 </ul> 596 595 </li> 597 <li class="tocline1"> 8.4 <a href="#header.host">Host</a></li>598 <li class="tocline1"> 8.5 <a href="#header.te">TE</a></li>599 <li class="tocline1"> 8.6 <a href="#header.trailer">Trailer</a></li>600 <li class="tocline1"> 8.7 <a href="#header.transfer-encoding">Transfer-Encoding</a></li>601 <li class="tocline1"> 8.8 <a href="#header.upgrade">Upgrade</a></li>602 <li class="tocline1"> 8.9 <a href="#header.via">Via</a></li>596 <li class="tocline1">7.4 <a href="#header.host">Host</a></li> 597 <li class="tocline1">7.5 <a href="#header.te">TE</a></li> 598 <li class="tocline1">7.6 <a href="#header.trailer">Trailer</a></li> 599 <li class="tocline1">7.7 <a href="#header.transfer-encoding">Transfer-Encoding</a></li> 600 <li class="tocline1">7.8 <a href="#header.upgrade">Upgrade</a></li> 601 <li class="tocline1">7.9 <a href="#header.via">Via</a></li> 603 602 </ul> 604 603 </li> 605 <li class="tocline0"> 9. <a href="#IANA.considerations">IANA Considerations</a><ul class="toc">606 <li class="tocline1"> 9.1 <a href="#message.header.registration">Message Header Registration</a></li>607 <li class="tocline1"> 9.2 <a href="#uri.scheme.registration">URI Scheme Registration</a></li>608 <li class="tocline1"> 9.3 <a href="#internet.media.type.http">Internet Media Type Registrations</a><ul class="toc">609 <li class="tocline1"> 9.3.1 <a href="#internet.media.type.message.http">Internet Media Type message/http</a></li>610 <li class="tocline1"> 9.3.2 <a href="#internet.media.type.application.http">Internet Media Type application/http</a></li>604 <li class="tocline0">8. <a href="#IANA.considerations">IANA Considerations</a><ul class="toc"> 605 <li class="tocline1">8.1 <a href="#message.header.registration">Message Header Registration</a></li> 606 <li class="tocline1">8.2 <a href="#uri.scheme.registration">URI Scheme Registration</a></li> 607 <li class="tocline1">8.3 <a href="#internet.media.type.http">Internet Media Type Registrations</a><ul class="toc"> 608 <li class="tocline1">8.3.1 <a href="#internet.media.type.message.http">Internet Media Type message/http</a></li> 609 <li class="tocline1">8.3.2 <a href="#internet.media.type.application.http">Internet Media Type application/http</a></li> 611 610 </ul> 612 611 </li> 613 612 </ul> 614 613 </li> 615 <li class="tocline0"> 10. <a href="#security.considerations">Security Considerations</a><ul class="toc">616 <li class="tocline1"> 10.1 <a href="#personal.information">Personal Information</a></li>617 <li class="tocline1"> 10.2 <a href="#abuse.of.server.log.information">Abuse of Server Log Information</a></li>618 <li class="tocline1"> 10.3 <a href="#attack.pathname">Attacks Based On File and Path Names</a></li>619 <li class="tocline1"> 10.4 <a href="#dns.spoofing">DNS Spoofing</a></li>620 <li class="tocline1"> 10.5 <a href="#attack.proxies">Proxies and Caching</a></li>621 <li class="tocline1"> 10.6 <a href="#attack.DoS">Denial of Service Attacks on Proxies</a></li>614 <li class="tocline0">9. <a href="#security.considerations">Security Considerations</a><ul class="toc"> 615 <li class="tocline1">9.1 <a href="#personal.information">Personal Information</a></li> 616 <li class="tocline1">9.2 <a href="#abuse.of.server.log.information">Abuse of Server Log Information</a></li> 617 <li class="tocline1">9.3 <a href="#attack.pathname">Attacks Based On File and Path Names</a></li> 618 <li class="tocline1">9.4 <a href="#dns.spoofing">DNS Spoofing</a></li> 619 <li class="tocline1">9.5 <a href="#attack.proxies">Proxies and Caching</a></li> 620 <li class="tocline1">9.6 <a href="#attack.DoS">Denial of Service Attacks on Proxies</a></li> 622 621 </ul> 623 622 </li> 624 <li class="tocline0">1 1. <a href="#ack">Acknowledgments</a></li>625 <li class="tocline0">1 2. <a href="#rfc.references">References</a><ul class="toc">626 <li class="tocline1">1 2.1 <a href="#rfc.references.1">Normative References</a></li>627 <li class="tocline1">1 2.2 <a href="#rfc.references.2">Informative References</a></li>623 <li class="tocline0">10. <a href="#ack">Acknowledgments</a></li> 624 <li class="tocline0">11. <a href="#rfc.references">References</a><ul class="toc"> 625 <li class="tocline1">11.1 <a href="#rfc.references.1">Normative References</a></li> 626 <li class="tocline1">11.2 <a href="#rfc.references.2">Informative References</a></li> 628 627 </ul> 629 628 </li> … … 675 674 <p id="rfc.section.1.1.p.2">An implementation is not compliant if it fails to satisfy one or more of the <em class="bcp14">MUST</em> or <em class="bcp14">REQUIRED</em> level requirements for the protocols it implements. An implementation that satisfies all the <em class="bcp14">MUST</em> or <em class="bcp14">REQUIRED</em> level and all the <em class="bcp14">SHOULD</em> level requirements for its protocols is said to be "unconditionally compliant"; one that satisfies all the <em class="bcp14">MUST</em> level requirements but not all the <em class="bcp14">SHOULD</em> level requirements for its protocols is said to be "conditionally compliant." 676 675 </p> 677 <h2 id="rfc.section.1.2"><a href="#rfc.section.1.2">1.2</a> <a id="intro.overall.operation" href="#intro.overall.operation">Overall Operation</a></h2> 678 <p id="rfc.section.1.2.p.1">HTTP is a request/response protocol. A client sends a request to the server in the form of a request method, URI, and protocol 679 version, followed by a MIME-like message containing request modifiers, client information, and possible body content over 680 a connection with a server. The server responds with a status line, including the message's protocol version and a success 681 or error code, followed by a MIME-like message containing server information, entity metainformation, and possible entity-body 682 content. The relationship between HTTP and MIME is described in <a href="p3-payload.html#differences.between.http.entities.and.rfc.2045.entities" title="Differences Between HTTP Entities and RFC 2045 Entities">Appendix A</a> of <a href="#Part3" id="rfc.xref.Part3.2"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>. 683 </p> 684 <p id="rfc.section.1.2.p.2">Most HTTP communication is initiated by a user agent and consists of a request to be applied to a resource on some origin 685 server. In the simplest case, this may be accomplished via a single connection (v) between the user agent (UA) and the origin 686 server (O). 687 </p> 688 <div id="rfc.figure.u.1"></div><pre class="drawing"> request chain ------------------------> 689 UA -------------------v------------------- O 690 <----------------------- response chain 691 </pre><p id="rfc.section.1.2.p.4">A more complicated situation occurs when one or more intermediaries are present in the request/response chain. There are three 692 common forms of intermediary: proxy, gateway, and tunnel. A proxy is a forwarding agent, receiving requests for a URI in its 693 absolute form, rewriting all or part of the message, and forwarding the reformatted request toward the server identified by 694 the URI. A gateway is a receiving agent, acting as a layer above some other server(s) and, if necessary, translating the requests 695 to the underlying server's protocol. A tunnel acts as a relay point between two connections without changing the messages; 696 tunnels are used when the communication needs to pass through an intermediary (such as a firewall) even when the intermediary 697 cannot understand the contents of the messages. 698 </p> 699 <div id="rfc.figure.u.2"></div><pre class="drawing"> request chain --------------------------------------> 700 UA -----v----- A -----v----- B -----v----- C -----v----- O 701 <------------------------------------- response chain 702 </pre><p id="rfc.section.1.2.p.6">The figure above shows three intermediaries (A, B, and C) between the user agent and origin server. A request or response 703 message that travels the whole chain will pass through four separate connections. This distinction is important because some 704 HTTP communication options may apply only to the connection with the nearest, non-tunnel neighbor, only to the end-points 705 of the chain, or to all connections along the chain. Although the diagram is linear, each participant may be engaged in multiple, 706 simultaneous communications. For example, B may be receiving requests from many clients other than A, and/or forwarding requests 707 to servers other than C, at the same time that it is handling A's request. 708 </p> 709 <p id="rfc.section.1.2.p.7">Any party to the communication which is not acting as a tunnel may employ an internal cache for handling requests. The effect 710 of a cache is that the request/response chain is shortened if one of the participants along the chain has a cached response 711 applicable to that request. The following illustrates the resulting chain if B has a cached copy of an earlier response from 712 O (via C) for a request which has not been cached by UA or A. 713 </p> 714 <div id="rfc.figure.u.3"></div><pre class="drawing"> request chain ----------> 715 UA -----v----- A -----v----- B - - - - - - C - - - - - - O 716 <--------- response chain 717 </pre><p id="rfc.section.1.2.p.9">Not all responses are usefully cacheable, and some requests may contain modifiers which place special requirements on cache 718 behavior. HTTP requirements for cache behavior and cacheable responses are defined in <a href="p6-cache.html#caching" title="Introduction">Section 1</a> of <a href="#Part6" id="rfc.xref.Part6.1"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>. 719 </p> 720 <p id="rfc.section.1.2.p.10">In fact, there are a wide variety of architectures and configurations of caches and proxies currently being experimented with 721 or deployed across the World Wide Web. These systems include national hierarchies of proxy caches to save transoceanic bandwidth, 722 systems that broadcast or multicast cache entries, organizations that distribute subsets of cached data via CD-ROM, and so 723 on. HTTP systems are used in corporate intranets over high-bandwidth links, and for access via PDAs with low-power radio links 724 and intermittent connectivity. The goal of HTTP/1.1 is to support the wide diversity of configurations already deployed while 725 introducing protocol constructs that meet the needs of those who build web applications that require high reliability and, 726 failing that, at least reliable indications of failure. 727 </p> 728 <p id="rfc.section.1.2.p.11">HTTP communication usually takes place over TCP/IP connections. The default port is TCP 80 (<<a href="http://www.iana.org/assignments/port-numbers">http://www.iana.org/assignments/port-numbers</a>>), but other ports can be used. This does not preclude HTTP from being implemented on top of any other protocol on the Internet, 729 or on other networks. HTTP only presumes a reliable transport; any protocol that provides such guarantees can be used; the 730 mapping of the HTTP/1.1 request and response structures onto the transport data units of the protocol in question is outside 731 the scope of this specification. 732 </p> 733 <p id="rfc.section.1.2.p.12">In HTTP/1.0, most implementations used a new connection for each request/response exchange. In HTTP/1.1, a connection may 734 be used for one or more request/response exchanges, although connections may be closed for a variety of reasons (see <a href="#persistent.connections" title="Persistent Connections">Section 7.1</a>). 735 </p> 736 <h1 id="rfc.section.2"><a href="#rfc.section.2">2.</a> <a id="notation" href="#notation">Notational Conventions and Generic Grammar</a></h1> 737 <h2 id="rfc.section.2.1"><a href="#rfc.section.2.1">2.1</a> <a id="notation.abnf" href="#notation.abnf">ABNF Extension: #rule</a></h2> 738 <p id="rfc.section.2.1.p.1">One extension to the ABNF rules of <a href="#RFC5234" id="rfc.xref.RFC5234.1"><cite title="Augmented BNF for Syntax Specifications: ABNF">[RFC5234]</cite></a> is used to improve readability. 739 </p> 740 <p id="rfc.section.2.1.p.2">A construct "#" is defined, similar to "*", for defining lists of elements. The full form is "<n>#<m>element" indicating at 676 <h2 id="rfc.section.1.2"><a href="#rfc.section.1.2">1.2</a> <a id="notation" href="#notation">Notational Conventions and Generic Grammar</a></h2> 677 <h3 id="rfc.section.1.2.1"><a href="#rfc.section.1.2.1">1.2.1</a> <a id="notation.abnf" href="#notation.abnf">ABNF Extension: #rule</a></h3> 678 <p id="rfc.section.1.2.1.p.1">One extension to the ABNF rules of <a href="#RFC5234" id="rfc.xref.RFC5234.1"><cite title="Augmented BNF for Syntax Specifications: ABNF">[RFC5234]</cite></a> is used to improve readability. 679 </p> 680 <p id="rfc.section.1.2.1.p.2">A construct "#" is defined, similar to "*", for defining lists of elements. The full form is "<n>#<m>element" indicating at 741 681 least <n> and at most <m> elements, each separated by one or more commas (",") and <em class="bcp14">OPTIONAL</em> linear white space (OWS). This makes the usual form of lists very easy; a rule such as 742 682 </p> 743 <div id="rfc.figure.u. 4"></div><pre class="text"> ( *<a href="#rule.whitespace" class="smpl">OWS</a> element *( *<a href="#rule.whitespace" class="smpl">OWS</a> "," *<a href="#rule.whitespace" class="smpl">OWS</a> element ))</pre><p id="rfc.section.2.1.p.3">can be shown as </p>744 <div id="rfc.figure.u. 5"></div><pre class="text"> 1#element</pre><p id="rfc.section.2.1.p.4">Wherever this construct is used, null elements are allowed, but do not contribute to the count of elements present. That is,683 <div id="rfc.figure.u.1"></div><pre class="text"> ( *<a href="#rule.whitespace" class="smpl">OWS</a> element *( *<a href="#rule.whitespace" class="smpl">OWS</a> "," *<a href="#rule.whitespace" class="smpl">OWS</a> element ))</pre><p id="rfc.section.1.2.1.p.3">can be shown as </p> 684 <div id="rfc.figure.u.2"></div><pre class="text"> 1#element</pre><p id="rfc.section.1.2.1.p.4">Wherever this construct is used, null elements are allowed, but do not contribute to the count of elements present. That is, 745 685 "(element), , (element) " is permitted, but counts as only two elements. Therefore, where at least one element is required, 746 686 at least one non-null element <em class="bcp14">MUST</em> be present. Default values are 0 and infinity so that "#element" allows any number, including zero; "1#element" requires at 747 687 least one; and "1#2element" allows one or two. 748 688 </p> 749 <p id="rfc.section. 2.1.p.5"> <span class="comment">[abnf.list: At a later point of time, we may want to add an appendix containing the whole ABNF, with the list rules expanded to strict689 <p id="rfc.section.1.2.1.p.5"> <span class="comment">[abnf.list: At a later point of time, we may want to add an appendix containing the whole ABNF, with the list rules expanded to strict 750 690 RFC 5234 notation.]</span> 751 691 </p> 752 <h 2 id="rfc.section.2.2"><a href="#rfc.section.2.2">2.2</a> <a id="basic.rules" href="#basic.rules">Basic Rules</a></h2>692 <h3 id="rfc.section.1.2.2"><a href="#rfc.section.1.2.2">1.2.2</a> <a id="basic.rules" href="#basic.rules">Basic Rules</a></h3> 753 693 <div id="core.rules"> 754 <p id="rfc.section. 2.2.p.1"> This specification uses the Augmented Backus-Naur Form (ABNF) notation of <a href="#RFC5234" id="rfc.xref.RFC5234.2"><cite title="Augmented BNF for Syntax Specifications: ABNF">[RFC5234]</cite></a>. The following core rules are included by reference, as defined in <a href="#RFC5234" id="rfc.xref.RFC5234.3"><cite title="Augmented BNF for Syntax Specifications: ABNF">[RFC5234]</cite></a>, <a href="http://tools.ietf.org/html/rfc5234#section-B.1">Appendix B.1</a>: ALPHA (letters), CHAR (any <a href="#USASCII" id="rfc.xref.USASCII.1"><cite title="Coded Character Set -- 7-bit American Standard Code for Information Interchange">[USASCII]</cite></a> character, excluding NUL), CR (carriage return), CRLF (CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double quote),694 <p id="rfc.section.1.2.2.p.1"> This specification uses the Augmented Backus-Naur Form (ABNF) notation of <a href="#RFC5234" id="rfc.xref.RFC5234.2"><cite title="Augmented BNF for Syntax Specifications: ABNF">[RFC5234]</cite></a>. The following core rules are included by reference, as defined in <a href="#RFC5234" id="rfc.xref.RFC5234.3"><cite title="Augmented BNF for Syntax Specifications: ABNF">[RFC5234]</cite></a>, <a href="http://tools.ietf.org/html/rfc5234#section-B.1">Appendix B.1</a>: ALPHA (letters), CHAR (any <a href="#USASCII" id="rfc.xref.USASCII.1"><cite title="Coded Character Set -- 7-bit American Standard Code for Information Interchange">[USASCII]</cite></a> character, excluding NUL), CR (carriage return), CRLF (CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double quote), 755 695 HEXDIG (hexadecimal 0-9/A-F/a-f), HTAB (horizontal tab), LF (line feed), OCTET (any 8-bit sequence of data), SP (space) and 756 696 WSP (white space). … … 758 698 </div> 759 699 <div id="rule.CRLF"> 760 <p id="rfc.section. 2.2.p.2"> HTTP/1.1 defines the sequence CR LF as the end-of-line marker for all protocol elements except the entity-body (see <a href="#tolerant.applications" title="Tolerant Applications">Appendix A</a> for tolerant applications). The end-of-line marker within an entity-body is defined by its associated media type, as described761 in <a href="p3-payload.html#media.types" title="Media Types">Section 3.3</a> of <a href="#Part3" id="rfc.xref.Part3. 3"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>.700 <p id="rfc.section.1.2.2.p.2"> HTTP/1.1 defines the sequence CR LF as the end-of-line marker for all protocol elements except the entity-body (see <a href="#tolerant.applications" title="Tolerant Applications">Appendix A</a> for tolerant applications). The end-of-line marker within an entity-body is defined by its associated media type, as described 701 in <a href="p3-payload.html#media.types" title="Media Types">Section 3.3</a> of <a href="#Part3" id="rfc.xref.Part3.2"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>. 762 702 </p> 763 703 </div> 764 704 <div id="rule.LWS"> 765 <p id="rfc.section. 2.2.p.3">All linear white space (LWS) in header field-values has the same semantics as SP. A recipient <em class="bcp14">MAY</em> replace any such linear white space with a single SP before interpreting the field value or forwarding the message downstream.705 <p id="rfc.section.1.2.2.p.3">All linear white space (LWS) in header field-values has the same semantics as SP. A recipient <em class="bcp14">MAY</em> replace any such linear white space with a single SP before interpreting the field value or forwarding the message downstream. 766 706 </p> 767 707 </div> 768 <p id="rfc.section. 2.2.p.4">Historically, HTTP/1.1 header field values allow linear white space folding across multiple lines. However, this specification769 deprecates its use; senders <em class="bcp14">MUST NOT</em> produce messages that include LWS folding (i.e., use the obs-fold rule), except within the message/http media type (<a href="#internet.media.type.message.http" title="Internet Media Type message/http">Section 9.3.1</a>). Receivers <em class="bcp14">SHOULD</em> still parse folded linear white space.770 </p> 771 <p id="rfc.section. 2.2.p.5">This specification uses three rules to denote the use of linear white space; BWS ("Bad" White Space), OWS (Optional White708 <p id="rfc.section.1.2.2.p.4">Historically, HTTP/1.1 header field values allow linear white space folding across multiple lines. However, this specification 709 deprecates its use; senders <em class="bcp14">MUST NOT</em> produce messages that include LWS folding (i.e., use the obs-fold rule), except within the message/http media type (<a href="#internet.media.type.message.http" title="Internet Media Type message/http">Section 8.3.1</a>). Receivers <em class="bcp14">SHOULD</em> still parse folded linear white space. 710 </p> 711 <p id="rfc.section.1.2.2.p.5">This specification uses three rules to denote the use of linear white space; BWS ("Bad" White Space), OWS (Optional White 772 712 Space), and RWS (Required White Space). 773 713 </p> 774 <p id="rfc.section. 2.2.p.6">"Bad" white space is allowed by the BNF, but senders <em class="bcp14">SHOULD NOT</em> produce it in messages. Receivers <em class="bcp14">MUST</em> accept it in incoming messages.775 </p> 776 <p id="rfc.section. 2.2.p.7">Required white space is used when at least one linear white space character is required to separate field tokens. In all such714 <p id="rfc.section.1.2.2.p.6">"Bad" white space is allowed by the BNF, but senders <em class="bcp14">SHOULD NOT</em> produce it in messages. Receivers <em class="bcp14">MUST</em> accept it in incoming messages. 715 </p> 716 <p id="rfc.section.1.2.2.p.7">Required white space is used when at least one linear white space character is required to separate field tokens. In all such 777 717 cases, a single SP character <em class="bcp14">SHOULD</em> be used. 778 718 </p> 779 719 <div id="rule.whitespace"> 780 <p id="rfc.section. 2.2.p.8"> </p>720 <p id="rfc.section.1.2.2.p.8"> </p> 781 721 </div> 782 <div id="rfc.figure.u. 6"></div><pre class="inline"><span id="rfc.iref.g.1"></span><span id="rfc.iref.g.2"></span><span id="rfc.iref.g.3"></span> <a href="#rule.whitespace" class="smpl">OWS</a> = *( [ obs-fold ] <a href="#core.rules" class="smpl">WSP</a> )722 <div id="rfc.figure.u.3"></div><pre class="inline"><span id="rfc.iref.g.1"></span><span id="rfc.iref.g.2"></span><span id="rfc.iref.g.3"></span> <a href="#rule.whitespace" class="smpl">OWS</a> = *( [ obs-fold ] <a href="#core.rules" class="smpl">WSP</a> ) 783 723 ; "optional" white space 784 724 <a href="#rule.whitespace" class="smpl">RWS</a> = 1*( [ obs-fold ] <a href="#core.rules" class="smpl">WSP</a> ) … … 788 728 <a href="#rule.whitespace" class="smpl">obs-fold</a> = <a href="#core.rules" class="smpl">CRLF</a> 789 729 </pre><div id="rule.TEXT"> 790 <p id="rfc.section. 2.2.p.10"> The TEXT rule is only used for descriptive field contents and values that are not intended to be interpreted by the message730 <p id="rfc.section.1.2.2.p.10"> The TEXT rule is only used for descriptive field contents and values that are not intended to be interpreted by the message 791 731 parser. Words of *TEXT <em class="bcp14">MAY</em> contain characters from character sets other than ISO-8859-1 <a href="#ISO-8859-1" id="rfc.xref.ISO-8859-1.1"><cite title="Information technology -- 8-bit single-byte coded graphic character sets -- Part 1: Latin alphabet No. 1">[ISO-8859-1]</cite></a> only when encoded according to the rules of <a href="#RFC2047" id="rfc.xref.RFC2047.1"><cite title="MIME (Multipurpose Internet Mail Extensions) Part Three: Message Header Extensions for Non-ASCII Text">[RFC2047]</cite></a>. 792 732 </p> 793 733 </div> 794 <div id="rfc.figure.u. 7"></div><pre class="inline"><span id="rfc.iref.g.4"></span> <a href="#rule.TEXT" class="smpl">TEXT</a> = %x20-7E / %x80-FF / <a href="#rule.whitespace" class="smpl">OWS</a>734 <div id="rfc.figure.u.4"></div><pre class="inline"><span id="rfc.iref.g.4"></span> <a href="#rule.TEXT" class="smpl">TEXT</a> = %x20-7E / %x80-FF / <a href="#rule.whitespace" class="smpl">OWS</a> 795 735 ; any <a href="#core.rules" class="smpl">OCTET</a> except <a href="#core.rules" class="smpl">CTL</a>s, but including <a href="#rule.whitespace" class="smpl">OWS</a> 796 </pre><p id="rfc.section. 2.2.p.12">A CRLF is allowed in the definition of TEXT only as part of a header field continuation. It is expected that the folding LWS736 </pre><p id="rfc.section.1.2.2.p.12">A CRLF is allowed in the definition of TEXT only as part of a header field continuation. It is expected that the folding LWS 797 737 will be replaced with a single SP before interpretation of the TEXT value. 798 738 </p> 799 739 <div id="rule.token.separators"> 800 <p id="rfc.section. 2.2.p.13"> Many HTTP/1.1 header field values consist of words separated by LWS or special characters. These special characters <em class="bcp14">MUST</em> be in a quoted string to be used within a parameter value (as defined in <a href="#transfer.codings" title="Transfer Codings">Section 3.4</a>).740 <p id="rfc.section.1.2.2.p.13"> Many HTTP/1.1 header field values consist of words separated by LWS or special characters. These special characters <em class="bcp14">MUST</em> be in a quoted string to be used within a parameter value (as defined in <a href="#transfer.codings" title="Transfer Codings">Section 2.4</a>). 801 741 </p> 802 742 </div> 803 <div id="rfc.figure.u. 8"></div><pre class="inline"><span id="rfc.iref.g.5"></span><span id="rfc.iref.g.6"></span> <a href="#rule.token.separators" class="smpl">tchar</a> = "!" / "#" / "$" / "%" / "&" / "'" / "*"743 <div id="rfc.figure.u.5"></div><pre class="inline"><span id="rfc.iref.g.5"></span><span id="rfc.iref.g.6"></span> <a href="#rule.token.separators" class="smpl">tchar</a> = "!" / "#" / "$" / "%" / "&" / "'" / "*" 804 744 / "+" / "-" / "." / "^" / "_" / "`" / "|" / "~" 805 745 / <a href="#core.rules" class="smpl">DIGIT</a> / <a href="#core.rules" class="smpl">ALPHA</a> … … 807 747 <a href="#rule.token.separators" class="smpl">token</a> = 1*<a href="#rule.token.separators" class="smpl">tchar</a> 808 748 </pre><div id="rule.comment"> 809 <p id="rfc.section. 2.2.p.15"> Comments can be included in some HTTP header fields by surrounding the comment text with parentheses. Comments are only allowed749 <p id="rfc.section.1.2.2.p.15"> Comments can be included in some HTTP header fields by surrounding the comment text with parentheses. Comments are only allowed 810 750 in fields containing "comment" as part of their field value definition. In all other fields, parentheses are considered part 811 751 of the field value. 812 752 </p> 813 753 </div> 814 <div id="rfc.figure.u. 9"></div><pre class="inline"><span id="rfc.iref.g.7"></span><span id="rfc.iref.g.8"></span> <a href="#rule.comment" class="smpl">comment</a> = "(" *( <a href="#rule.comment" class="smpl">ctext</a> / <a href="#rule.quoted-pair" class="smpl">quoted-pair</a> / <a href="#rule.comment" class="smpl">comment</a> ) ")"754 <div id="rfc.figure.u.6"></div><pre class="inline"><span id="rfc.iref.g.7"></span><span id="rfc.iref.g.8"></span> <a href="#rule.comment" class="smpl">comment</a> = "(" *( <a href="#rule.comment" class="smpl">ctext</a> / <a href="#rule.quoted-pair" class="smpl">quoted-pair</a> / <a href="#rule.comment" class="smpl">comment</a> ) ")" 815 755 <a href="#rule.comment" class="smpl">ctext</a> = <any <a href="#rule.TEXT" class="smpl">TEXT</a> excluding "(" and ")"> 816 756 </pre><div id="rule.quoted-string"> 817 <p id="rfc.section. 2.2.p.17"> A string of text is parsed as a single word if it is quoted using double-quote marks.</p>757 <p id="rfc.section.1.2.2.p.17"> A string of text is parsed as a single word if it is quoted using double-quote marks.</p> 818 758 </div> 819 <div id="rfc.figure.u. 10"></div><pre class="inline"><span id="rfc.iref.g.9"></span><span id="rfc.iref.g.10"></span> <a href="#rule.quoted-string" class="smpl">quoted-string</a> = <a href="#core.rules" class="smpl">DQUOTE</a> *(<a href="#rule.quoted-string" class="smpl">qdtext</a> / <a href="#rule.quoted-pair" class="smpl">quoted-pair</a> ) <a href="#core.rules" class="smpl">DQUOTE</a>759 <div id="rfc.figure.u.7"></div><pre class="inline"><span id="rfc.iref.g.9"></span><span id="rfc.iref.g.10"></span> <a href="#rule.quoted-string" class="smpl">quoted-string</a> = <a href="#core.rules" class="smpl">DQUOTE</a> *(<a href="#rule.quoted-string" class="smpl">qdtext</a> / <a href="#rule.quoted-pair" class="smpl">quoted-pair</a> ) <a href="#core.rules" class="smpl">DQUOTE</a> 820 760 <a href="#rule.quoted-string" class="smpl">qdtext</a> = <any <a href="#rule.TEXT" class="smpl">TEXT</a> excluding <a href="#core.rules" class="smpl">DQUOTE</a> and "\"> 821 761 </pre><div id="rule.quoted-pair"> 822 <p id="rfc.section. 2.2.p.19"> The backslash character ("\") <em class="bcp14">MAY</em> be used as a single-character quoting mechanism only within quoted-string and comment constructs.762 <p id="rfc.section.1.2.2.p.19"> The backslash character ("\") <em class="bcp14">MAY</em> be used as a single-character quoting mechanism only within quoted-string and comment constructs. 823 763 </p> 824 764 </div> 825 <div id="rfc.figure.u. 11"></div><pre class="inline"><span id="rfc.iref.g.11"></span><span id="rfc.iref.g.12"></span> <a href="#rule.quoted-pair" class="smpl">quoted-text</a> = %x01-09 /765 <div id="rfc.figure.u.8"></div><pre class="inline"><span id="rfc.iref.g.11"></span><span id="rfc.iref.g.12"></span> <a href="#rule.quoted-pair" class="smpl">quoted-text</a> = %x01-09 / 826 766 %x0B-0C / 827 767 %x0E-FF ; Characters excluding NUL, <a href="#core.rules" class="smpl">CR</a> and <a href="#core.rules" class="smpl">LF</a> 828 768 <a href="#rule.quoted-pair" class="smpl">quoted-pair</a> = "\" <a href="#rule.quoted-pair" class="smpl">quoted-text</a> 829 </pre><h 2 id="rfc.section.2.3"><a href="#rfc.section.2.3">2.3</a> <a id="abnf.dependencies" href="#abnf.dependencies">ABNF Rules defined in other Parts of the Specification</a></h2>830 <p id="rfc.section. 2.3.p.1">The ABNF rules below are defined in other parts:</p>831 <div id="rfc.figure.u. 12"></div><pre class="inline"> <a href="#abnf.dependencies" class="smpl">request-header</a> = <request-header, defined in <a href="#Part2" id="rfc.xref.Part2.1"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>, <a href="p2-semantics.html#request.header.fields" title="Request Header Fields">Section 4</a>>769 </pre><h3 id="rfc.section.1.2.3"><a href="#rfc.section.1.2.3">1.2.3</a> <a id="abnf.dependencies" href="#abnf.dependencies">ABNF Rules defined in other Parts of the Specification</a></h3> 770 <p id="rfc.section.1.2.3.p.1">The ABNF rules below are defined in other parts:</p> 771 <div id="rfc.figure.u.9"></div><pre class="inline"> <a href="#abnf.dependencies" class="smpl">request-header</a> = <request-header, defined in <a href="#Part2" id="rfc.xref.Part2.1"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>, <a href="p2-semantics.html#request.header.fields" title="Request Header Fields">Section 4</a>> 832 772 <a href="#abnf.dependencies" class="smpl">response-header</a> = <response-header, defined in <a href="#Part2" id="rfc.xref.Part2.2"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>, <a href="p2-semantics.html#response.header.fields" title="Response Header Fields">Section 6</a>> 833 </pre><div id="rfc.figure.u.13"></div><pre class="inline"> <a href="#abnf.dependencies" class="smpl">accept-params</a> = <accept-params, 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" title="Accept">Section 6.1</a>> 834 <a href="#abnf.dependencies" class="smpl">entity-body</a> = <entity-body, defined in <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#entity.body" title="Entity Body">Section 4.2</a>> 835 <a href="#abnf.dependencies" class="smpl">entity-header</a> = <entity-header, defined in <a href="#Part3" id="rfc.xref.Part3.6"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>, <a href="p3-payload.html#entity.header.fields" title="Entity Header Fields">Section 4.1</a>> 836 </pre><div id="rfc.figure.u.14"></div><pre class="inline"> <a href="#abnf.dependencies" class="smpl">Cache-Control</a> = <Cache-Control, 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.pragma" title="Pragma">Section 16.4</a>> 837 <a href="#abnf.dependencies" class="smpl">Pragma</a> = <Pragma, defined in <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.pragma" title="Pragma">Section 16.4</a>> 838 <a href="#abnf.dependencies" class="smpl">Warning</a> = <Warning, defined in <a href="#Part6" id="rfc.xref.Part6.4"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>, <a href="p6-cache.html#header.warning" title="Warning">Section 16.6</a>> 839 </pre><h1 id="rfc.section.3"><a href="#rfc.section.3">3.</a> <a id="protocol.parameters" href="#protocol.parameters">Protocol Parameters</a></h1> 840 <h2 id="rfc.section.3.1"><a href="#rfc.section.3.1">3.1</a> <a id="http.version" href="#http.version">HTTP Version</a></h2> 841 <p id="rfc.section.3.1.p.1">HTTP uses a "<major>.<minor>" numbering scheme to indicate versions of the protocol. The protocol versioning policy is intended 773 </pre><div id="rfc.figure.u.10"></div><pre class="inline"> <a href="#abnf.dependencies" class="smpl">accept-params</a> = <accept-params, 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" title="Accept">Section 6.1</a>> 774 <a href="#abnf.dependencies" class="smpl">entity-body</a> = <entity-body, 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#entity.body" title="Entity Body">Section 4.2</a>> 775 <a href="#abnf.dependencies" class="smpl">entity-header</a> = <entity-header, defined in <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#entity.header.fields" title="Entity Header Fields">Section 4.1</a>> 776 </pre><div id="rfc.figure.u.11"></div><pre class="inline"> <a href="#abnf.dependencies" class="smpl">Cache-Control</a> = <Cache-Control, 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.pragma" title="Pragma">Section 16.4</a>> 777 <a href="#abnf.dependencies" class="smpl">Pragma</a> = <Pragma, 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.pragma" title="Pragma">Section 16.4</a>> 778 <a href="#abnf.dependencies" class="smpl">Warning</a> = <Warning, defined in <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.warning" title="Warning">Section 16.6</a>> 779 </pre><h2 id="rfc.section.1.3"><a href="#rfc.section.1.3">1.3</a> <a id="intro.overall.operation" href="#intro.overall.operation">Overall Operation</a></h2> 780 <p id="rfc.section.1.3.p.1">HTTP is a request/response protocol. A client sends a request to the server in the form of a request method, URI, and protocol 781 version, followed by a MIME-like message containing request modifiers, client information, and possible body content over 782 a connection with a server. The server responds with a status line, including the message's protocol version and a success 783 or error code, followed by a MIME-like message containing server information, entity metainformation, and possible entity-body 784 content. The relationship between HTTP and MIME is described in <a href="p3-payload.html#differences.between.http.entities.and.rfc.2045.entities" title="Differences Between HTTP Entities and RFC 2045 Entities">Appendix A</a> of <a href="#Part3" id="rfc.xref.Part3.6"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>. 785 </p> 786 <p id="rfc.section.1.3.p.2">Most HTTP communication is initiated by a user agent and consists of a request to be applied to a resource on some origin 787 server. In the simplest case, this may be accomplished via a single connection (v) between the user agent (UA) and the origin 788 server (O). 789 </p> 790 <div id="rfc.figure.u.12"></div><pre class="drawing"> request chain ------------------------> 791 UA -------------------v------------------- O 792 <----------------------- response chain 793 </pre><p id="rfc.section.1.3.p.4">A more complicated situation occurs when one or more intermediaries are present in the request/response chain. There are three 794 common forms of intermediary: proxy, gateway, and tunnel. A proxy is a forwarding agent, receiving requests for a URI in its 795 absolute form, rewriting all or part of the message, and forwarding the reformatted request toward the server identified by 796 the URI. A gateway is a receiving agent, acting as a layer above some other server(s) and, if necessary, translating the requests 797 to the underlying server's protocol. A tunnel acts as a relay point between two connections without changing the messages; 798 tunnels are used when the communication needs to pass through an intermediary (such as a firewall) even when the intermediary 799 cannot understand the contents of the messages. 800 </p> 801 <div id="rfc.figure.u.13"></div><pre class="drawing"> request chain --------------------------------------> 802 UA -----v----- A -----v----- B -----v----- C -----v----- O 803 <------------------------------------- response chain 804 </pre><p id="rfc.section.1.3.p.6">The figure above shows three intermediaries (A, B, and C) between the user agent and origin server. A request or response 805 message that travels the whole chain will pass through four separate connections. This distinction is important because some 806 HTTP communication options may apply only to the connection with the nearest, non-tunnel neighbor, only to the end-points 807 of the chain, or to all connections along the chain. Although the diagram is linear, each participant may be engaged in multiple, 808 simultaneous communications. For example, B may be receiving requests from many clients other than A, and/or forwarding requests 809 to servers other than C, at the same time that it is handling A's request. 810 </p> 811 <p id="rfc.section.1.3.p.7">Any party to the communication which is not acting as a tunnel may employ an internal cache for handling requests. The effect 812 of a cache is that the request/response chain is shortened if one of the participants along the chain has a cached response 813 applicable to that request. The following illustrates the resulting chain if B has a cached copy of an earlier response from 814 O (via C) for a request which has not been cached by UA or A. 815 </p> 816 <div id="rfc.figure.u.14"></div><pre class="drawing"> request chain ----------> 817 UA -----v----- A -----v----- B - - - - - - C - - - - - - O 818 <--------- response chain 819 </pre><p id="rfc.section.1.3.p.9">Not all responses are usefully cacheable, and some requests may contain modifiers which place special requirements on cache 820 behavior. HTTP requirements for cache behavior and cacheable responses are defined in <a href="p6-cache.html#caching" title="Introduction">Section 1</a> of <a href="#Part6" id="rfc.xref.Part6.4"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>. 821 </p> 822 <p id="rfc.section.1.3.p.10">In fact, there are a wide variety of architectures and configurations of caches and proxies currently being experimented with 823 or deployed across the World Wide Web. These systems include national hierarchies of proxy caches to save transoceanic bandwidth, 824 systems that broadcast or multicast cache entries, organizations that distribute subsets of cached data via CD-ROM, and so 825 on. HTTP systems are used in corporate intranets over high-bandwidth links, and for access via PDAs with low-power radio links 826 and intermittent connectivity. The goal of HTTP/1.1 is to support the wide diversity of configurations already deployed while 827 introducing protocol constructs that meet the needs of those who build web applications that require high reliability and, 828 failing that, at least reliable indications of failure. 829 </p> 830 <p id="rfc.section.1.3.p.11">HTTP communication usually takes place over TCP/IP connections. The default port is TCP 80 (<<a href="http://www.iana.org/assignments/port-numbers">http://www.iana.org/assignments/port-numbers</a>>), but other ports can be used. This does not preclude HTTP from being implemented on top of any other protocol on the Internet, 831 or on other networks. HTTP only presumes a reliable transport; any protocol that provides such guarantees can be used; the 832 mapping of the HTTP/1.1 request and response structures onto the transport data units of the protocol in question is outside 833 the scope of this specification. 834 </p> 835 <p id="rfc.section.1.3.p.12">In HTTP/1.0, most implementations used a new connection for each request/response exchange. In HTTP/1.1, a connection may 836 be used for one or more request/response exchanges, although connections may be closed for a variety of reasons (see <a href="#persistent.connections" title="Persistent Connections">Section 6.1</a>). 837 </p> 838 <h1 id="rfc.section.2"><a href="#rfc.section.2">2.</a> <a id="protocol.parameters" href="#protocol.parameters">Protocol Parameters</a></h1> 839 <h2 id="rfc.section.2.1"><a href="#rfc.section.2.1">2.1</a> <a id="http.version" href="#http.version">HTTP Version</a></h2> 840 <p id="rfc.section.2.1.p.1">HTTP uses a "<major>.<minor>" numbering scheme to indicate versions of the protocol. The protocol versioning policy is intended 842 841 to allow the sender to indicate the format of a message and its capacity for understanding further HTTP communication, rather 843 842 than the features obtained via that communication. No change is made to the version number for the addition of message components … … 847 846 of a message within the protocol is changed. See <a href="#RFC2145" id="rfc.xref.RFC2145.1"><cite title="Use and Interpretation of HTTP Version Numbers">[RFC2145]</cite></a> for a fuller explanation. 848 847 </p> 849 <p id="rfc.section. 3.1.p.2">The version of an HTTP message is indicated by an HTTP-Version field in the first line of the message. HTTP-Version is case-sensitive.</p>848 <p id="rfc.section.2.1.p.2">The version of an HTTP message is indicated by an HTTP-Version field in the first line of the message. HTTP-Version is case-sensitive.</p> 850 849 <div id="rfc.figure.u.15"></div><pre class="inline"><span id="rfc.iref.g.13"></span><span id="rfc.iref.g.14"></span> <a href="#http.version" class="smpl">HTTP-Version</a> = <a href="#http.version" class="smpl">HTTP-Prot-Name</a> "/" 1*<a href="#core.rules" class="smpl">DIGIT</a> "." 1*<a href="#core.rules" class="smpl">DIGIT</a> 851 850 <a href="#http.version" class="smpl">HTTP-Prot-Name</a> = %x48.54.54.50 ; "HTTP", case-sensitive 852 </pre><p id="rfc.section. 3.1.p.4">Note that the major and minor numbers <em class="bcp14">MUST</em> be treated as separate integers and that each <em class="bcp14">MAY</em> be incremented higher than a single digit. Thus, HTTP/2.4 is a lower version than HTTP/2.13, which in turn is lower than HTTP/12.3.851 </pre><p id="rfc.section.2.1.p.4">Note that the major and minor numbers <em class="bcp14">MUST</em> be treated as separate integers and that each <em class="bcp14">MAY</em> be incremented higher than a single digit. Thus, HTTP/2.4 is a lower version than HTTP/2.13, which in turn is lower than HTTP/12.3. 853 852 Leading zeros <em class="bcp14">MUST</em> be ignored by recipients and <em class="bcp14">MUST NOT</em> be sent. 854 853 </p> 855 <p id="rfc.section. 3.1.p.5">An application that sends a request or response message that includes HTTP-Version of "HTTP/1.1" <em class="bcp14">MUST</em> be at least conditionally compliant with this specification. Applications that are at least conditionally compliant with this854 <p id="rfc.section.2.1.p.5">An application that sends a request or response message that includes HTTP-Version of "HTTP/1.1" <em class="bcp14">MUST</em> be at least conditionally compliant with this specification. Applications that are at least conditionally compliant with this 856 855 specification <em class="bcp14">SHOULD</em> use an HTTP-Version of "HTTP/1.1" in their messages, and <em class="bcp14">MUST</em> do so for any message that is not compatible with HTTP/1.0. For more details on when to send specific HTTP-Version values, 857 856 see <a href="#RFC2145" id="rfc.xref.RFC2145.2"><cite title="Use and Interpretation of HTTP Version Numbers">[RFC2145]</cite></a>. 858 857 </p> 859 <p id="rfc.section. 3.1.p.6">The HTTP version of an application is the highest HTTP version for which the application is at least conditionally compliant.</p>860 <p id="rfc.section. 3.1.p.7">Proxy and gateway applications need to be careful when forwarding messages in protocol versions different from that of the858 <p id="rfc.section.2.1.p.6">The HTTP version of an application is the highest HTTP version for which the application is at least conditionally compliant.</p> 859 <p id="rfc.section.2.1.p.7">Proxy and gateway applications need to be careful when forwarding messages in protocol versions different from that of the 861 860 application. Since the protocol version indicates the protocol capability of the sender, a proxy/gateway <em class="bcp14">MUST NOT</em> send a message with a version indicator which is greater than its actual version. If a higher version request is received, 862 861 the proxy/gateway <em class="bcp14">MUST</em> either downgrade the request version, or respond with an error, or switch to tunnel behavior. 863 862 </p> 864 <p id="rfc.section. 3.1.p.8">Due to interoperability problems with HTTP/1.0 proxies discovered since the publication of <a href="#RFC2068" id="rfc.xref.RFC2068.1"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2068]</cite></a>, caching proxies <em class="bcp14">MUST</em>, gateways <em class="bcp14">MAY</em>, and tunnels <em class="bcp14">MUST NOT</em> upgrade the request to the highest version they support. The proxy/gateway's response to that request <em class="bcp14">MUST</em> be in the same major version as the request.865 </p> 866 <p id="rfc.section. 3.1.p.9"> </p>863 <p id="rfc.section.2.1.p.8">Due to interoperability problems with HTTP/1.0 proxies discovered since the publication of <a href="#RFC2068" id="rfc.xref.RFC2068.1"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2068]</cite></a>, caching proxies <em class="bcp14">MUST</em>, gateways <em class="bcp14">MAY</em>, and tunnels <em class="bcp14">MUST NOT</em> upgrade the request to the highest version they support. The proxy/gateway's response to that request <em class="bcp14">MUST</em> be in the same major version as the request. 864 </p> 865 <p id="rfc.section.2.1.p.9"> </p> 867 866 <dl class="empty"> 868 867 <dd> <b>Note:</b> Converting between versions of HTTP may involve modification of header fields required or forbidden by the versions involved. 869 868 </dd> 870 869 </dl> 871 <h2 id="rfc.section. 3.2"><a href="#rfc.section.3.2">3.2</a> <a id="uri" href="#uri">Uniform Resource Identifiers</a></h2>872 <p id="rfc.section. 3.2.p.1">Uniform Resource Identifiers (URIs) <a href="#RFC3986" id="rfc.xref.RFC3986.2"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a> are used in HTTP to indicate the target of a request and to identify additional resources related to that resource, the request,870 <h2 id="rfc.section.2.2"><a href="#rfc.section.2.2">2.2</a> <a id="uri" href="#uri">Uniform Resource Identifiers</a></h2> 871 <p id="rfc.section.2.2.p.1">Uniform Resource Identifiers (URIs) <a href="#RFC3986" id="rfc.xref.RFC3986.2"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a> are used in HTTP to indicate the target of a request and to identify additional resources related to that resource, the request, 873 872 or the response. Each protocol element in HTTP that allows a URI reference will indicate in its ABNF whether the element allows 874 873 only a URI in absolute form, any relative reference, or some limited subset of the URI-reference grammar. Unless otherwise 875 874 indicated, relative URI references are to be parsed relative to the URI corresponding to the request target (the base URI). 876 875 </p> 877 <p id="rfc.section. 3.2.p.2">This specification adopts the definitions of "URI-reference", "absolute-URI", "fragment", "port", "host", "path-abempty",876 <p id="rfc.section.2.2.p.2">This specification adopts the definitions of "URI-reference", "absolute-URI", "fragment", "port", "host", "path-abempty", 878 877 "path-absolute", "query", and "authority" from <a href="#RFC3986" id="rfc.xref.RFC3986.3"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a>: 879 878 </p> … … 889 888 <a href="#uri" class="smpl">relative-part</a> = <relative-part, defined in <a href="#RFC3986" id="rfc.xref.RFC3986.12"><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>> 890 889 <a href="#uri" class="smpl">relativeURI</a> = <a href="#uri" class="smpl">relative-part</a> [ "?" <a href="#uri" class="smpl">query</a> ] 891 </pre><p id="rfc.section. 3.2.p.4">HTTP does not place an a priori limit on the length of a URI. Servers <em class="bcp14">MUST</em> be able to handle the URI of any resource they serve, and <em class="bcp14">SHOULD</em> be able to handle URIs of unbounded length if they provide GET-based forms that could generate such URIs. A server <em class="bcp14">SHOULD</em> return 414 (Request-URI Too Long) status if a URI is longer than the server can handle (see <a href="p2-semantics.html#status.414" title="414 Request-URI Too Long">Section 9.4.15</a> of <a href="#Part2" id="rfc.xref.Part2.3"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>).892 </p> 893 <p id="rfc.section. 3.2.p.5"> </p>890 </pre><p id="rfc.section.2.2.p.4">HTTP does not place an a priori limit on the length of a URI. Servers <em class="bcp14">MUST</em> be able to handle the URI of any resource they serve, and <em class="bcp14">SHOULD</em> be able to handle URIs of unbounded length if they provide GET-based forms that could generate such URIs. A server <em class="bcp14">SHOULD</em> return 414 (Request-URI Too Long) status if a URI is longer than the server can handle (see <a href="p2-semantics.html#status.414" title="414 Request-URI Too Long">Section 9.4.15</a> of <a href="#Part2" id="rfc.xref.Part2.3"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>). 891 </p> 892 <p id="rfc.section.2.2.p.5"> </p> 894 893 <dl class="empty"> 895 894 <dd> <b>Note:</b> Servers ought to be cautious about depending on URI lengths above 255 bytes, because some older client or proxy implementations … … 897 896 </dd> 898 897 </dl> 899 <h3 id="rfc.section. 3.2.1"><a href="#rfc.section.3.2.1">3.2.1</a> <a id="http.uri" href="#http.uri">http URI scheme</a></h3>898 <h3 id="rfc.section.2.2.1"><a href="#rfc.section.2.2.1">2.2.1</a> <a id="http.uri" href="#http.uri">http URI scheme</a></h3> 900 899 <div id="rfc.iref.h.1"></div> 901 900 <div id="rfc.iref.u.1"></div> 902 <p id="rfc.section. 3.2.1.p.1">The "http" scheme is used to locate network resources via the HTTP protocol. This section defines the syntax and semantics901 <p id="rfc.section.2.2.1.p.1">The "http" scheme is used to locate network resources via the HTTP protocol. This section defines the syntax and semantics 903 902 for identifiers using the http or https URI schemes. 904 903 </p> 905 904 <div id="rfc.figure.u.17"></div><pre class="inline"><span id="rfc.iref.g.24"></span> <a href="#http.uri" class="smpl">http-URI</a> = "http:" "//" <a href="#uri" class="smpl">authority</a> <a href="#uri" class="smpl">path-abempty</a> [ "?" <a href="#uri" class="smpl">query</a> ] 906 </pre><p id="rfc.section. 3.2.1.p.3">If the port is empty or not given, port 80 is assumed. The semantics are that the identified resource is located at the server907 listening for TCP connections on that port of that host, and the Request-URI for the resource is path-absolute (<a href="#request-uri" title="Request-URI">Section 5.1.2</a>). The use of IP addresses in URLs <em class="bcp14">SHOULD</em> be avoided whenever possible (see <a href="#RFC1900" id="rfc.xref.RFC1900.1"><cite title="Renumbering Needs Work">[RFC1900]</cite></a>). If the path-absolute is not present in the URL, it <em class="bcp14">MUST</em> be given as "/" when used as a Request-URI for a resource (<a href="#request-uri" title="Request-URI">Section 5.1.2</a>). If a proxy receives a host name which is not a fully qualified domain name, it <em class="bcp14">MAY</em> add its domain to the host name it received. If a proxy receives a fully qualified domain name, the proxy <em class="bcp14">MUST NOT</em> change the host name.905 </pre><p id="rfc.section.2.2.1.p.3">If the port is empty or not given, port 80 is assumed. The semantics are that the identified resource is located at the server 906 listening for TCP connections on that port of that host, and the Request-URI for the resource is path-absolute (<a href="#request-uri" title="Request-URI">Section 4.1.2</a>). The use of IP addresses in URLs <em class="bcp14">SHOULD</em> be avoided whenever possible (see <a href="#RFC1900" id="rfc.xref.RFC1900.1"><cite title="Renumbering Needs Work">[RFC1900]</cite></a>). If the path-absolute is not present in the URL, it <em class="bcp14">MUST</em> be given as "/" when used as a Request-URI for a resource (<a href="#request-uri" title="Request-URI">Section 4.1.2</a>). If a proxy receives a host name which is not a fully qualified domain name, it <em class="bcp14">MAY</em> add its domain to the host name it received. If a proxy receives a fully qualified domain name, the proxy <em class="bcp14">MUST NOT</em> change the host name. 908 907 </p> 909 908 <dl class="empty"> … … 911 910 </dd> 912 911 </dl> 913 <h3 id="rfc.section. 3.2.2"><a href="#rfc.section.3.2.2">3.2.2</a> <a id="uri.comparison" href="#uri.comparison">URI Comparison</a></h3>914 <p id="rfc.section. 3.2.2.p.1">When comparing two URIs to decide if they match or not, a client <em class="bcp14">SHOULD</em> use a case-sensitive octet-by-octet comparison of the entire URIs, with these exceptions:912 <h3 id="rfc.section.2.2.2"><a href="#rfc.section.2.2.2">2.2.2</a> <a id="uri.comparison" href="#uri.comparison">URI Comparison</a></h3> 913 <p id="rfc.section.2.2.2.p.1">When comparing two URIs to decide if they match or not, a client <em class="bcp14">SHOULD</em> use a case-sensitive octet-by-octet comparison of the entire URIs, with these exceptions: 915 914 </p> 916 915 <ul> … … 922 921 <li>An empty path-absolute is equivalent to an path-absolute of "/".</li> 923 922 </ul> 924 <p id="rfc.section. 3.2.2.p.2">Characters other than those in the "reserved" set (see <a href="#RFC3986" id="rfc.xref.RFC3986.13"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a>, <a href="http://tools.ietf.org/html/rfc3986#section-2.2">Section 2.2</a>) are equivalent to their ""%" <a href="#core.rules" class="smpl">HEXDIG</a> <a href="#core.rules" class="smpl">HEXDIG</a>" encoding.925 </p> 926 <p id="rfc.section. 3.2.2.p.3">For example, the following three URIs are equivalent:</p>923 <p id="rfc.section.2.2.2.p.2">Characters other than those in the "reserved" set (see <a href="#RFC3986" id="rfc.xref.RFC3986.13"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a>, <a href="http://tools.ietf.org/html/rfc3986#section-2.2">Section 2.2</a>) are equivalent to their ""%" <a href="#core.rules" class="smpl">HEXDIG</a> <a href="#core.rules" class="smpl">HEXDIG</a>" encoding. 924 </p> 925 <p id="rfc.section.2.2.2.p.3">For example, the following three URIs are equivalent:</p> 927 926 <div id="rfc.figure.u.18"></div><pre class="text"> http://example.com:80/~smith/home.html 928 927 http://EXAMPLE.com/%7Esmith/home.html 929 928 http://EXAMPLE.com:/%7esmith/home.html 930 </pre><h2 id="rfc.section. 3.3"><a href="#rfc.section.3.3">3.3</a> <a id="date.time.formats" href="#date.time.formats">Date/Time Formats</a></h2>931 <h3 id="rfc.section. 3.3.1"><a href="#rfc.section.3.3.1">3.3.1</a> <a id="full.date" href="#full.date">Full Date</a></h3>932 <p id="rfc.section. 3.3.1.p.1">HTTP applications have historically allowed three different formats for the representation of date/time stamps:</p>929 </pre><h2 id="rfc.section.2.3"><a href="#rfc.section.2.3">2.3</a> <a id="date.time.formats" href="#date.time.formats">Date/Time Formats</a></h2> 930 <h3 id="rfc.section.2.3.1"><a href="#rfc.section.2.3.1">2.3.1</a> <a id="full.date" href="#full.date">Full Date</a></h3> 931 <p id="rfc.section.2.3.1.p.1">HTTP applications have historically allowed three different formats for the representation of date/time stamps:</p> 933 932 <div id="rfc.figure.u.19"></div><pre class="text"> Sun, 06 Nov 1994 08:49:37 GMT ; RFC 1123 934 933 Sunday, 06-Nov-94 08:49:37 GMT ; obsolete RFC 850 format 935 934 Sun Nov 6 08:49:37 1994 ; ANSI C's asctime() format 936 </pre><p id="rfc.section. 3.3.1.p.3">The first format is preferred as an Internet standard and represents a fixed-length subset of that defined by <a href="#RFC1123" id="rfc.xref.RFC1123.1"><cite title="Requirements for Internet Hosts - Application and Support">[RFC1123]</cite></a>. The other formats are described here only for compatibility with obsolete implementations. HTTP/1.1 clients and servers935 </pre><p id="rfc.section.2.3.1.p.3">The first format is preferred as an Internet standard and represents a fixed-length subset of that defined by <a href="#RFC1123" id="rfc.xref.RFC1123.1"><cite title="Requirements for Internet Hosts - Application and Support">[RFC1123]</cite></a>. The other formats are described here only for compatibility with obsolete implementations. HTTP/1.1 clients and servers 937 936 that parse the date value <em class="bcp14">MUST</em> accept all three formats (for compatibility with HTTP/1.0), though they <em class="bcp14">MUST</em> only generate the RFC 1123 format for representing HTTP-date values in header fields. See <a href="#tolerant.applications" title="Tolerant Applications">Appendix A</a> for further information. 938 937 </p> … … 942 941 </dd> 943 942 </dl> 944 <p id="rfc.section. 3.3.1.p.5">All HTTP date/time stamps <em class="bcp14">MUST</em> be represented in Greenwich Mean Time (GMT), without exception. For the purposes of HTTP, GMT is exactly equal to UTC (Coordinated943 <p id="rfc.section.2.3.1.p.5">All HTTP date/time stamps <em class="bcp14">MUST</em> be represented in Greenwich Mean Time (GMT), without exception. For the purposes of HTTP, GMT is exactly equal to UTC (Coordinated 945 944 Universal Time). This is indicated in the first two formats by the inclusion of "GMT" as the three-letter abbreviation for 946 945 time zone, and <em class="bcp14">MUST</em> be assumed when reading the asctime format. HTTP-date is case sensitive and <em class="bcp14">MUST NOT</em> include additional LWS beyond that specifically included as SP in the grammar. … … 997 996 s-Nov = %x4E.6F.76 ; "Nov", case-sensitive 998 997 s-Dec = %x44.65.63 ; "Dec", case-sensitive 999 </pre><p id="rfc.section. 3.3.1.p.7"> <b>Note:</b> HTTP requirements for the date/time stamp format apply only to their usage within the protocol stream. Clients and servers998 </pre><p id="rfc.section.2.3.1.p.7"> <b>Note:</b> HTTP requirements for the date/time stamp format apply only to their usage within the protocol stream. Clients and servers 1000 999 are not required to use these formats for user presentation, request logging, etc. 1001 1000 </p> 1002 <h2 id="rfc.section. 3.4"><a href="#rfc.section.3.4">3.4</a> <a id="transfer.codings" href="#transfer.codings">Transfer Codings</a></h2>1003 <p id="rfc.section. 3.4.p.1">Transfer-coding values are used to indicate an encoding transformation that has been, can be, or may need to be applied to1001 <h2 id="rfc.section.2.4"><a href="#rfc.section.2.4">2.4</a> <a id="transfer.codings" href="#transfer.codings">Transfer Codings</a></h2> 1002 <p id="rfc.section.2.4.p.1">Transfer-coding values are used to indicate an encoding transformation that has been, can be, or may need to be applied to 1004 1003 an entity-body in order to ensure "safe transport" through the network. This differs from a content coding in that the transfer-coding 1005 1004 is a property of the message, not of the original entity. … … 1008 1007 <a href="#transfer.codings" class="smpl">transfer-extension</a> = <a href="#rule.token.separators" class="smpl">token</a> *( <a href="#rule.whitespace" class="smpl">OWS</a> ";" <a href="#rule.whitespace" class="smpl">OWS</a> <a href="#transfer.codings" class="smpl">parameter</a> ) 1009 1008 </pre><div id="rule.parameter"> 1010 <p id="rfc.section. 3.4.p.3"> Parameters are in the form of attribute/value pairs.</p>1009 <p id="rfc.section.2.4.p.3"> Parameters are in the form of attribute/value pairs.</p> 1011 1010 </div> 1012 1011 <div id="rfc.figure.u.22"></div><pre class="inline"><span id="rfc.iref.g.39"></span><span id="rfc.iref.g.40"></span><span id="rfc.iref.g.41"></span> <a href="#transfer.codings" class="smpl">parameter</a> = <a href="#rule.parameter" class="smpl">attribute</a> <a href="#rule.whitespace" class="smpl">BWS</a> "=" <a href="#rule.whitespace" class="smpl">BWS</a> <a href="#rule.parameter" class="smpl">value</a> 1013 1012 <a href="#rule.parameter" class="smpl">attribute</a> = <a href="#rule.token.separators" class="smpl">token</a> 1014 1013 <a href="#rule.parameter" class="smpl">value</a> = <a href="#rule.token.separators" class="smpl">token</a> / <a href="#rule.quoted-string" class="smpl">quoted-string</a> 1015 </pre><p id="rfc.section. 3.4.p.5">All transfer-coding values are case-insensitive. HTTP/1.1 uses transfer-coding values in the TE header field (<a href="#header.te" id="rfc.xref.header.te.1" title="TE">Section 8.5</a>) and in the Transfer-Encoding header field (<a href="#header.transfer-encoding" id="rfc.xref.header.transfer-encoding.1" title="Transfer-Encoding">Section 8.7</a>).1016 </p> 1017 <p id="rfc.section. 3.4.p.6">Whenever a transfer-coding is applied to a message-body, the set of transfer-codings <em class="bcp14">MUST</em> include "chunked", unless the message indicates it is terminated by closing the connection. When the "chunked" transfer-coding1014 </pre><p id="rfc.section.2.4.p.5">All transfer-coding values are case-insensitive. HTTP/1.1 uses transfer-coding values in the TE header field (<a href="#header.te" id="rfc.xref.header.te.1" title="TE">Section 7.5</a>) and in the Transfer-Encoding header field (<a href="#header.transfer-encoding" id="rfc.xref.header.transfer-encoding.1" title="Transfer-Encoding">Section 7.7</a>). 1015 </p> 1016 <p id="rfc.section.2.4.p.6">Whenever a transfer-coding is applied to a message-body, the set of transfer-codings <em class="bcp14">MUST</em> include "chunked", unless the message indicates it is terminated by closing the connection. When the "chunked" transfer-coding 1018 1017 is used, it <em class="bcp14">MUST</em> be the last transfer-coding applied to the message-body. The "chunked" transfer-coding <em class="bcp14">MUST NOT</em> be applied more than once to a message-body. These rules allow the recipient to determine the transfer-length of the message 1019 (<a href="#message.length" title="Message Length">Section 4.4</a>).1020 </p> 1021 <p id="rfc.section. 3.4.p.7">Transfer-codings are analogous to the Content-Transfer-Encoding values of MIME <a href="#RFC2045" id="rfc.xref.RFC2045.2"><cite title="Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies">[RFC2045]</cite></a>, which were designed to enable safe transport of binary data over a 7-bit transport service. However, safe transport has1018 (<a href="#message.length" title="Message Length">Section 3.4</a>). 1019 </p> 1020 <p id="rfc.section.2.4.p.7">Transfer-codings are analogous to the Content-Transfer-Encoding values of MIME <a href="#RFC2045" id="rfc.xref.RFC2045.2"><cite title="Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies">[RFC2045]</cite></a>, which were designed to enable safe transport of binary data over a 7-bit transport service. However, safe transport has 1022 1021 a different focus for an 8bit-clean transfer protocol. In HTTP, the only unsafe characteristic of message-bodies is the difficulty 1023 in determining the exact body length (<a href="#message.length" title="Message Length">Section 4.4</a>), or the desire to encrypt data over a shared transport.1024 </p> 1025 <p id="rfc.section. 3.4.p.8">The Internet Assigned Numbers Authority (IANA) acts as a registry for transfer-coding value tokens. Initially, the registry1026 contains the following tokens: "chunked" (<a href="#chunked.transfer.encoding" title="Chunked Transfer Coding">Section 3.4.1</a>), "gzip", "compress", and "deflate" (<a href="p3-payload.html#content.codings" title="Content Codings">Section 3.2</a> of <a href="#Part3" id="rfc.xref.Part3.7"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>).1027 </p> 1028 <p id="rfc.section. 3.4.p.9">New transfer-coding value tokens <em class="bcp14">SHOULD</em> be registered in the same way as new content-coding value tokens (<a href="p3-payload.html#content.codings" title="Content Codings">Section 3.2</a> of <a href="#Part3" id="rfc.xref.Part3.8"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>).1029 </p> 1030 <p id="rfc.section. 3.4.p.10">A server which receives an entity-body with a transfer-coding it does not understand <em class="bcp14">SHOULD</em> return 501 (Not Implemented), and close the connection. A server <em class="bcp14">MUST NOT</em> send transfer-codings to an HTTP/1.0 client.1031 </p> 1032 <h3 id="rfc.section. 3.4.1"><a href="#rfc.section.3.4.1">3.4.1</a> <a id="chunked.transfer.encoding" href="#chunked.transfer.encoding">Chunked Transfer Coding</a></h3>1033 <p id="rfc.section. 3.4.1.p.1">The chunked encoding modifies the body of a message in order to transfer it as a series of chunks, each with its own size1022 in determining the exact body length (<a href="#message.length" title="Message Length">Section 3.4</a>), or the desire to encrypt data over a shared transport. 1023 </p> 1024 <p id="rfc.section.2.4.p.8">The Internet Assigned Numbers Authority (IANA) acts as a registry for transfer-coding value tokens. Initially, the registry 1025 contains the following tokens: "chunked" (<a href="#chunked.transfer.encoding" title="Chunked Transfer Coding">Section 2.4.1</a>), "gzip", "compress", and "deflate" (<a href="p3-payload.html#content.codings" title="Content Codings">Section 3.2</a> of <a href="#Part3" id="rfc.xref.Part3.7"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>). 1026 </p> 1027 <p id="rfc.section.2.4.p.9">New transfer-coding value tokens <em class="bcp14">SHOULD</em> be registered in the same way as new content-coding value tokens (<a href="p3-payload.html#content.codings" title="Content Codings">Section 3.2</a> of <a href="#Part3" id="rfc.xref.Part3.8"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>). 1028 </p> 1029 <p id="rfc.section.2.4.p.10">A server which receives an entity-body with a transfer-coding it does not understand <em class="bcp14">SHOULD</em> return 501 (Not Implemented), and close the connection. A server <em class="bcp14">MUST NOT</em> send transfer-codings to an HTTP/1.0 client. 1030 </p> 1031 <h3 id="rfc.section.2.4.1"><a href="#rfc.section.2.4.1">2.4.1</a> <a id="chunked.transfer.encoding" href="#chunked.transfer.encoding">Chunked Transfer Coding</a></h3> 1032 <p id="rfc.section.2.4.1.p.1">The chunked encoding modifies the body of a message in order to transfer it as a series of chunks, each with its own size 1034 1033 indicator, followed by an <em class="bcp14">OPTIONAL</em> trailer containing entity-header fields. This allows dynamically produced content to be transferred along with the information 1035 1034 necessary for the recipient to verify that it has received the full message. … … 1051 1050 <a href="#chunked.transfer.encoding" class="smpl">chunk-data</a> = 1*<a href="#core.rules" class="smpl">OCTET</a> ; a sequence of chunk-size octets 1052 1051 <a href="#chunked.transfer.encoding" class="smpl">trailer-part</a> = *(<a href="#abnf.dependencies" class="smpl">entity-header</a> <a href="#core.rules" class="smpl">CRLF</a>) 1053 </pre><p id="rfc.section. 3.4.1.p.3">The chunk-size field is a string of hex digits indicating the size of the chunk-data in octets. The chunked encoding is ended1052 </pre><p id="rfc.section.2.4.1.p.3">The chunk-size field is a string of hex digits indicating the size of the chunk-data in octets. The chunked encoding is ended 1054 1053 by any chunk whose size is zero, followed by the trailer, which is terminated by an empty line. 1055 1054 </p> 1056 <p id="rfc.section. 3.4.1.p.4">The trailer allows the sender to include additional HTTP header fields at the end of the message. The Trailer header field1057 can be used to indicate which header fields are included in a trailer (see <a href="#header.trailer" id="rfc.xref.header.trailer.1" title="Trailer">Section 8.6</a>).1058 </p> 1059 <p id="rfc.section. 3.4.1.p.5">A server using chunked transfer-coding in a response <em class="bcp14">MUST NOT</em> use the trailer for any header fields unless at least one of the following is true:1055 <p id="rfc.section.2.4.1.p.4">The trailer allows the sender to include additional HTTP header fields at the end of the message. The Trailer header field 1056 can be used to indicate which header fields are included in a trailer (see <a href="#header.trailer" id="rfc.xref.header.trailer.1" title="Trailer">Section 7.6</a>). 1057 </p> 1058 <p id="rfc.section.2.4.1.p.5">A server using chunked transfer-coding in a response <em class="bcp14">MUST NOT</em> use the trailer for any header fields unless at least one of the following is true: 1060 1059 </p> 1061 1060 <ol> 1062 1061 <li>the request included a TE header field that indicates "trailers" is acceptable in the transfer-coding of the response, as 1063 described in <a href="#header.te" id="rfc.xref.header.te.2" title="TE">Section 8.5</a>; or,1062 described in <a href="#header.te" id="rfc.xref.header.te.2" title="TE">Section 7.5</a>; or, 1064 1063 </li> 1065 1064 <li>the server is the origin server for the response, the trailer fields consist entirely of optional metadata, and the recipient … … 1068 1067 </li> 1069 1068 </ol> 1070 <p id="rfc.section. 3.4.1.p.6">This requirement prevents an interoperability failure when the message is being received by an HTTP/1.1 (or later) proxy and1069 <p id="rfc.section.2.4.1.p.6">This requirement prevents an interoperability failure when the message is being received by an HTTP/1.1 (or later) proxy and 1071 1070 forwarded to an HTTP/1.0 recipient. It avoids a situation where compliance with the protocol would have necessitated a possibly 1072 1071 infinite buffer on the proxy. 1073 1072 </p> 1074 <p id="rfc.section. 3.4.1.p.7">A process for decoding the "chunked" transfer-coding can be represented in pseudo-code as:</p>1073 <p id="rfc.section.2.4.1.p.7">A process for decoding the "chunked" transfer-coding can be represented in pseudo-code as:</p> 1075 1074 <div id="rfc.figure.u.24"></div><pre class="text"> length := 0 1076 1075 read chunk-size, chunk-ext (if any) and CRLF … … 1088 1087 Content-Length := length 1089 1088 Remove "chunked" from Transfer-Encoding 1090 </pre><p id="rfc.section. 3.4.1.p.9">All HTTP/1.1 applications <em class="bcp14">MUST</em> be able to receive and decode the "chunked" transfer-coding, and <em class="bcp14">MUST</em> ignore chunk-ext extensions they do not understand.1091 </p> 1092 <h2 id="rfc.section. 3.5"><a href="#rfc.section.3.5">3.5</a> <a id="product.tokens" href="#product.tokens">Product Tokens</a></h2>1093 <p id="rfc.section. 3.5.p.1">Product tokens are used to allow communicating applications to identify themselves by software name and version. Most fields1089 </pre><p id="rfc.section.2.4.1.p.9">All HTTP/1.1 applications <em class="bcp14">MUST</em> be able to receive and decode the "chunked" transfer-coding, and <em class="bcp14">MUST</em> ignore chunk-ext extensions they do not understand. 1090 </p> 1091 <h2 id="rfc.section.2.5"><a href="#rfc.section.2.5">2.5</a> <a id="product.tokens" href="#product.tokens">Product Tokens</a></h2> 1092 <p id="rfc.section.2.5.p.1">Product tokens are used to allow communicating applications to identify themselves by software name and version. Most fields 1094 1093 using product tokens also allow sub-products which form a significant part of the application to be listed, separated by white 1095 1094 space. By convention, the products are listed in order of their significance for identifying the application. … … 1097 1096 <div id="rfc.figure.u.25"></div><pre class="inline"><span id="rfc.iref.g.51"></span><span id="rfc.iref.g.52"></span> <a href="#product.tokens" class="smpl">product</a> = <a href="#rule.token.separators" class="smpl">token</a> ["/" <a href="#product.tokens" class="smpl">product-version</a>] 1098 1097 <a href="#product.tokens" class="smpl">product-version</a> = <a href="#rule.token.separators" class="smpl">token</a> 1099 </pre><p id="rfc.section. 3.5.p.3">Examples:</p>1098 </pre><p id="rfc.section.2.5.p.3">Examples:</p> 1100 1099 <div id="rfc.figure.u.26"></div><pre class="text"> User-Agent: CERN-LineMode/2.15 libwww/2.17b3 1101 1100 Server: Apache/0.8.4 1102 </pre><p id="rfc.section. 3.5.p.5">Product tokens <em class="bcp14">SHOULD</em> be short and to the point. They <em class="bcp14">MUST NOT</em> be used for advertising or other non-essential information. Although any token character <em class="bcp14">MAY</em> appear in a product-version, this token <em class="bcp14">SHOULD</em> only be used for a version identifier (i.e., successive versions of the same product <em class="bcp14">SHOULD</em> only differ in the product-version portion of the product value).1103 </p> 1104 <h1 id="rfc.section. 4"><a href="#rfc.section.4">4.</a> <a id="http.message" href="#http.message">HTTP Message</a></h1>1105 <h2 id="rfc.section. 4.1"><a href="#rfc.section.4.1">4.1</a> <a id="message.types" href="#message.types">Message Types</a></h2>1106 <p id="rfc.section. 4.1.p.1">HTTP messages consist of requests from client to server and responses from server to client.</p>1101 </pre><p id="rfc.section.2.5.p.5">Product tokens <em class="bcp14">SHOULD</em> be short and to the point. They <em class="bcp14">MUST NOT</em> be used for advertising or other non-essential information. Although any token character <em class="bcp14">MAY</em> appear in a product-version, this token <em class="bcp14">SHOULD</em> only be used for a version identifier (i.e., successive versions of the same product <em class="bcp14">SHOULD</em> only differ in the product-version portion of the product value). 1102 </p> 1103 <h1 id="rfc.section.3"><a href="#rfc.section.3">3.</a> <a id="http.message" href="#http.message">HTTP Message</a></h1> 1104 <h2 id="rfc.section.3.1"><a href="#rfc.section.3.1">3.1</a> <a id="message.types" href="#message.types">Message Types</a></h2> 1105 <p id="rfc.section.3.1.p.1">HTTP messages consist of requests from client to server and responses from server to client.</p> 1107 1106 <div id="rfc.figure.u.27"></div><pre class="inline"><span id="rfc.iref.g.53"></span> <a href="#message.types" class="smpl">HTTP-message</a> = <a href="#request" class="smpl">Request</a> / <a href="#response" class="smpl">Response</a> ; HTTP/1.1 messages 1108 </pre><p id="rfc.section. 4.1.p.3">Request (<a href="#request" title="Request">Section 5</a>) and Response (<a href="#response" title="Response">Section 6</a>) messages use the generic message format of <a href="#RFC5322" id="rfc.xref.RFC5322.2"><cite title="Internet Message Format">[RFC5322]</cite></a> for transferring entities (the payload of the message). Both types of message consist of a start-line, zero or more header1107 </pre><p id="rfc.section.3.1.p.3">Request (<a href="#request" title="Request">Section 4</a>) and Response (<a href="#response" title="Response">Section 5</a>) messages use the generic message format of <a href="#RFC5322" id="rfc.xref.RFC5322.2"><cite title="Internet Message Format">[RFC5322]</cite></a> for transferring entities (the payload of the message). Both types of message consist of a start-line, zero or more header 1109 1108 fields (also known as "headers"), an empty line (i.e., a line with nothing preceding the CRLF) indicating the end of the header 1110 1109 fields, and possibly a message-body. … … 1115 1114 [ <a href="#message.body" class="smpl">message-body</a> ] 1116 1115 <a href="#message.types" class="smpl">start-line</a> = <a href="#request-line" class="smpl">Request-Line</a> / <a href="#status-line" class="smpl">Status-Line</a> 1117 </pre><p id="rfc.section. 4.1.p.5">In the interest of robustness, servers <em class="bcp14">SHOULD</em> ignore any empty line(s) received where a Request-Line is expected. In other words, if the server is reading the protocol1116 </pre><p id="rfc.section.3.1.p.5">In the interest of robustness, servers <em class="bcp14">SHOULD</em> ignore any empty line(s) received where a Request-Line is expected. In other words, if the server is reading the protocol 1118 1117 stream at the beginning of a message and receives a CRLF first, it should ignore the CRLF. 1119 1118 </p> 1120 <p id="rfc.section. 4.1.p.6">Certain buggy HTTP/1.0 client implementations generate extra CRLF's after a POST request. To restate what is explicitly forbidden1119 <p id="rfc.section.3.1.p.6">Certain buggy HTTP/1.0 client implementations generate extra CRLF's after a POST request. To restate what is explicitly forbidden 1121 1120 by the BNF, an HTTP/1.1 client <em class="bcp14">MUST NOT</em> preface or follow a request with an extra CRLF. 1122 1121 </p> 1123 <h2 id="rfc.section. 4.2"><a href="#rfc.section.4.2">4.2</a> <a id="message.headers" href="#message.headers">Message Headers</a></h2>1124 <p id="rfc.section. 4.2.p.1">HTTP header fields, which include general-header (<a href="#general.header.fields" title="General Header Fields">Section 4.5</a>), request-header (<a href="p2-semantics.html#request.header.fields" title="Request Header Fields">Section 4</a> of <a href="#Part2" id="rfc.xref.Part2.4"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>), response-header (<a href="p2-semantics.html#response.header.fields" title="Response Header Fields">Section 6</a> of <a href="#Part2" id="rfc.xref.Part2.5"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>), and entity-header (<a href="p3-payload.html#entity.header.fields" title="Entity Header Fields">Section 4.1</a> of <a href="#Part3" id="rfc.xref.Part3.9"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>) fields, follow the same generic format as that given in <a href="http://tools.ietf.org/html/rfc5322#section-2.1">Section 2.1</a> of <a href="#RFC5322" id="rfc.xref.RFC5322.3"><cite title="Internet Message Format">[RFC5322]</cite></a>. Each header field consists of a name followed by a colon (":") and the field value. Field names are case-insensitive. The1122 <h2 id="rfc.section.3.2"><a href="#rfc.section.3.2">3.2</a> <a id="message.headers" href="#message.headers">Message Headers</a></h2> 1123 <p id="rfc.section.3.2.p.1">HTTP header fields, which include general-header (<a href="#general.header.fields" title="General Header Fields">Section 3.5</a>), request-header (<a href="p2-semantics.html#request.header.fields" title="Request Header Fields">Section 4</a> of <a href="#Part2" id="rfc.xref.Part2.4"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>), response-header (<a href="p2-semantics.html#response.header.fields" title="Response Header Fields">Section 6</a> of <a href="#Part2" id="rfc.xref.Part2.5"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>), and entity-header (<a href="p3-payload.html#entity.header.fields" title="Entity Header Fields">Section 4.1</a> of <a href="#Part3" id="rfc.xref.Part3.9"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>) fields, follow the same generic format as that given in <a href="http://tools.ietf.org/html/rfc5322#section-2.1">Section 2.1</a> of <a href="#RFC5322" id="rfc.xref.RFC5322.3"><cite title="Internet Message Format">[RFC5322]</cite></a>. Each header field consists of a name followed by a colon (":") and the field value. Field names are case-insensitive. The 1125 1124 field value <em class="bcp14">MAY</em> be preceded by any amount of LWS, though a single SP is preferred. Header fields can be extended over multiple lines by preceding 1126 1125 each extra line with at least one SP or HTAB. Applications ought to follow "common form", where one is known or indicated, … … 1132 1131 <a href="#message.headers" class="smpl">field-value</a> = *( <a href="#message.headers" class="smpl">field-content</a> / <a href="#rule.whitespace" class="smpl">OWS</a> ) 1133 1132 <a href="#message.headers" class="smpl">field-content</a> = <field content> 1134 </pre><p id="rfc.section. 4.2.p.3"> <span class="comment">[rfc.comment.1: whitespace between field-name and colon is an error and MUST NOT be accepted]</span>1135 </p> 1136 <p id="rfc.section. 4.2.p.4">The field-content does not include any leading or trailing LWS: linear white space occurring before the first non-whitespace1133 </pre><p id="rfc.section.3.2.p.3"> <span class="comment">[rfc.comment.1: whitespace between field-name and colon is an error and MUST NOT be accepted]</span> 1134 </p> 1135 <p id="rfc.section.3.2.p.4">The field-content does not include any leading or trailing LWS: linear white space occurring before the first non-whitespace 1137 1136 character of the field-value or after the last non-whitespace character of the field-value. Such leading or trailing LWS <em class="bcp14">MAY</em> be removed without changing the semantics of the field value. Any LWS that occurs between field-content <em class="bcp14">MAY</em> be replaced with a single SP before interpreting the field value or forwarding the message downstream. 1138 1137 </p> 1139 <p id="rfc.section. 4.2.p.5">The order in which header fields with differing field names are received is not significant. However, it is "good practice"1138 <p id="rfc.section.3.2.p.5">The order in which header fields with differing field names are received is not significant. However, it is "good practice" 1140 1139 to send general-header fields first, followed by request-header or response-header fields, and ending with the entity-header 1141 1140 fields. 1142 1141 </p> 1143 <p id="rfc.section. 4.2.p.6">Multiple message-header fields with the same field-name <em class="bcp14">MAY</em> be present in a message if and only if the entire field-value for that header field is defined as a comma-separated list [i.e.,1142 <p id="rfc.section.3.2.p.6">Multiple message-header fields with the same field-name <em class="bcp14">MAY</em> be present in a message if and only if the entire field-value for that header field is defined as a comma-separated list [i.e., 1144 1143 #(values)]. It <em class="bcp14">MUST</em> be possible to combine the multiple header fields into one "field-name: field-value" pair, without changing the semantics 1145 1144 of the message, by appending each subsequent field-value to the first, each separated by a comma. The order in which header … … 1147 1146 thus a proxy <em class="bcp14">MUST NOT</em> change the order of these field values when a message is forwarded. 1148 1147 </p> 1149 <p id="rfc.section. 4.2.p.7"> </p>1148 <p id="rfc.section.3.2.p.7"> </p> 1150 1149 <dl class="empty"> 1151 1150 <dd> <b>Note:</b> the "Set-Cookie" header as implemented in practice (as opposed to how it is specified in <a href="#RFC2109" id="rfc.xref.RFC2109.1"><cite title="HTTP State Management Mechanism">[RFC2109]</cite></a>) can occur multiple times, but does not use the list syntax, and thus cannot be combined into a single line. (See Appendix … … 1153 1152 </dd> 1154 1153 </dl> 1155 <h2 id="rfc.section. 4.3"><a href="#rfc.section.4.3">4.3</a> <a id="message.body" href="#message.body">Message Body</a></h2>1156 <p id="rfc.section. 4.3.p.1">The message-body (if any) of an HTTP message is used to carry the entity-body associated with the request or response. The1154 <h2 id="rfc.section.3.3"><a href="#rfc.section.3.3">3.3</a> <a id="message.body" href="#message.body">Message Body</a></h2> 1155 <p id="rfc.section.3.3.p.1">The message-body (if any) of an HTTP message is used to carry the entity-body associated with the request or response. The 1157 1156 message-body differs from the entity-body only when a transfer-coding has been applied, as indicated by the Transfer-Encoding 1158 header field (<a href="#header.transfer-encoding" id="rfc.xref.header.transfer-encoding.2" title="Transfer-Encoding">Section 8.7</a>).1157 header field (<a href="#header.transfer-encoding" id="rfc.xref.header.transfer-encoding.2" title="Transfer-Encoding">Section 7.7</a>). 1159 1158 </p> 1160 1159 <div id="rfc.figure.u.30"></div><pre class="inline"><span id="rfc.iref.g.60"></span> <a href="#message.body" class="smpl">message-body</a> = <a href="#abnf.dependencies" class="smpl">entity-body</a> 1161 1160 / <entity-body encoded as per <a href="#header.transfer-encoding" class="smpl">Transfer-Encoding</a>> 1162 </pre><p id="rfc.section. 4.3.p.3">Transfer-Encoding <em class="bcp14">MUST</em> be used to indicate any transfer-codings applied by an application to ensure safe and proper transfer of the message. Transfer-Encoding1163 is a property of the message, not of the entity, and thus <em class="bcp14">MAY</em> be added or removed by any application along the request/response chain. (However, <a href="#transfer.codings" title="Transfer Codings">Section 3.4</a> places restrictions on when certain transfer-codings may be used.)1164 </p> 1165 <p id="rfc.section. 4.3.p.4">The rules for when a message-body is allowed in a message differ for requests and responses.</p>1166 <p id="rfc.section. 4.3.p.5">The presence of a message-body in a request is signaled by the inclusion of a Content-Length or Transfer-Encoding header field1161 </pre><p id="rfc.section.3.3.p.3">Transfer-Encoding <em class="bcp14">MUST</em> be used to indicate any transfer-codings applied by an application to ensure safe and proper transfer of the message. Transfer-Encoding 1162 is a property of the message, not of the entity, and thus <em class="bcp14">MAY</em> be added or removed by any application along the request/response chain. (However, <a href="#transfer.codings" title="Transfer Codings">Section 2.4</a> places restrictions on when certain transfer-codings may be used.) 1163 </p> 1164 <p id="rfc.section.3.3.p.4">The rules for when a message-body is allowed in a message differ for requests and responses.</p> 1165 <p id="rfc.section.3.3.p.5">The presence of a message-body in a request is signaled by the inclusion of a Content-Length or Transfer-Encoding header field 1167 1166 in the request's message-headers. A message-body <em class="bcp14">MUST NOT</em> be included in a request if the specification of the request method (<a href="p2-semantics.html#method" title="Method">Section 3</a> of <a href="#Part2" id="rfc.xref.Part2.6"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>) explicitly disallows an entity-body in requests. When a request message contains both a message-body of non-zero length 1168 1167 and a method that does not define any semantics for that request message-body, then an origin server <em class="bcp14">SHOULD</em> either ignore the message-body or respond with an appropriate error message (e.g., 413). A proxy or gateway, when presented 1169 1168 the same request, <em class="bcp14">SHOULD</em> either forward the request inbound with the message-body or ignore the message-body when determining a response. 1170 1169 </p> 1171 <p id="rfc.section. 4.3.p.6">For response messages, whether or not a message-body is included with a message is dependent on both the request method and1172 the response status code (<a href="#status.code.and.reason.phrase" title="Status Code and Reason Phrase">Section 6.1.1</a>). All responses to the HEAD request method <em class="bcp14">MUST NOT</em> include a message-body, even though the presence of entity-header fields might lead one to believe they do. All 1xx (informational),1170 <p id="rfc.section.3.3.p.6">For response messages, whether or not a message-body is included with a message is dependent on both the request method and 1171 the response status code (<a href="#status.code.and.reason.phrase" title="Status Code and Reason Phrase">Section 5.1.1</a>). All responses to the HEAD request method <em class="bcp14">MUST NOT</em> include a message-body, even though the presence of entity-header fields might lead one to believe they do. All 1xx (informational), 1173 1172 204 (No Content), and 304 (Not Modified) responses <em class="bcp14">MUST NOT</em> include a message-body. All other responses do include a message-body, although it <em class="bcp14">MAY</em> be of zero length. 1174 1173 </p> 1175 <h2 id="rfc.section. 4.4"><a href="#rfc.section.4.4">4.4</a> <a id="message.length" href="#message.length">Message Length</a></h2>1176 <p id="rfc.section. 4.4.p.1">The transfer-length of a message is the length of the message-body as it appears in the message; that is, after any transfer-codings1174 <h2 id="rfc.section.3.4"><a href="#rfc.section.3.4">3.4</a> <a id="message.length" href="#message.length">Message Length</a></h2> 1175 <p id="rfc.section.3.4.p.1">The transfer-length of a message is the length of the message-body as it appears in the message; that is, after any transfer-codings 1177 1176 have been applied. When a message-body is included with a message, the transfer-length of that body is determined by one of 1178 1177 the following (in order of precedence): 1179 1178 </p> 1180 <p id="rfc.section. 4.4.p.2"> </p>1179 <p id="rfc.section.3.4.p.2"> </p> 1181 1180 <ol> 1182 1181 <li> … … 1186 1185 </li> 1187 1186 <li> 1188 <p>If a Transfer-Encoding header field (<a href="#header.transfer-encoding" id="rfc.xref.header.transfer-encoding.3" title="Transfer-Encoding">Section 8.7</a>) is present and the "chunked" transfer-coding (<a href="#transfer.codings" title="Transfer Codings">Section 3.4</a>) is used, the transfer-length is defined by the use of this transfer-coding. If a Transfer-Encoding header field is present1187 <p>If a Transfer-Encoding header field (<a href="#header.transfer-encoding" id="rfc.xref.header.transfer-encoding.3" title="Transfer-Encoding">Section 7.7</a>) is present and the "chunked" transfer-coding (<a href="#transfer.codings" title="Transfer Codings">Section 2.4</a>) is used, the transfer-length is defined by the use of this transfer-coding. If a Transfer-Encoding header field is present 1189 1188 and the "chunked" transfer-coding is not present, the transfer-length is defined by the sender closing the connection. 1190 1189 </p> 1191 1190 </li> 1192 1191 <li> 1193 <p>If a Content-Length header field (<a href="#header.content-length" id="rfc.xref.header.content-length.1" title="Content-Length">Section 8.2</a>) is present, its decimal value in OCTETs represents both the entity-length and the transfer-length. The Content-Length header1192 <p>If a Content-Length header field (<a href="#header.content-length" id="rfc.xref.header.content-length.1" title="Content-Length">Section 7.2</a>) is present, its decimal value in OCTETs represents both the entity-length and the transfer-length. The Content-Length header 1194 1193 field <em class="bcp14">MUST NOT</em> be sent if these two lengths are different (i.e., if a Transfer-Encoding header field is present). If a message is received 1195 1194 with both a Transfer-Encoding header field and a Content-Length header field, the latter <em class="bcp14">MUST</em> be ignored. … … 1212 1211 </li> 1213 1212 </ol> 1214 <p id="rfc.section. 4.4.p.3">For compatibility with HTTP/1.0 applications, HTTP/1.1 requests containing a message-body <em class="bcp14">MUST</em> include a valid Content-Length header field unless the server is known to be HTTP/1.1 compliant. If a request contains a message-body1213 <p id="rfc.section.3.4.p.3">For compatibility with HTTP/1.0 applications, HTTP/1.1 requests containing a message-body <em class="bcp14">MUST</em> include a valid Content-Length header field unless the server is known to be HTTP/1.1 compliant. If a request contains a message-body 1215 1214 and a Content-Length is not given, the server <em class="bcp14">SHOULD</em> respond with 400 (Bad Request) if it cannot determine the length of the message, or with 411 (Length Required) if it wishes 1216 1215 to insist on receiving a valid Content-Length. 1217 1216 </p> 1218 <p id="rfc.section. 4.4.p.4">All HTTP/1.1 applications that receive entities <em class="bcp14">MUST</em> accept the "chunked" transfer-coding (<a href="#transfer.codings" title="Transfer Codings">Section 3.4</a>), thus allowing this mechanism to be used for messages when the message length cannot be determined in advance.1219 </p> 1220 <p id="rfc.section. 4.4.p.5">Messages <em class="bcp14">MUST NOT</em> include both a Content-Length header field and a transfer-coding. If the message does include a transfer-coding, the Content-Length <em class="bcp14">MUST</em> be ignored.1221 </p> 1222 <p id="rfc.section. 4.4.p.6">When a Content-Length is given in a message where a message-body is allowed, its field value <em class="bcp14">MUST</em> exactly match the number of OCTETs in the message-body. HTTP/1.1 user agents <em class="bcp14">MUST</em> notify the user when an invalid length is received and detected.1223 </p> 1224 <h2 id="rfc.section. 4.5"><a href="#rfc.section.4.5">4.5</a> <a id="general.header.fields" href="#general.header.fields">General Header Fields</a></h2>1225 <p id="rfc.section. 4.5.p.1">There are a few header fields which have general applicability for both request and response messages, but which do not apply1217 <p id="rfc.section.3.4.p.4">All HTTP/1.1 applications that receive entities <em class="bcp14">MUST</em> accept the "chunked" transfer-coding (<a href="#transfer.codings" title="Transfer Codings">Section 2.4</a>), thus allowing this mechanism to be used for messages when the message length cannot be determined in advance. 1218 </p> 1219 <p id="rfc.section.3.4.p.5">Messages <em class="bcp14">MUST NOT</em> include both a Content-Length header field and a transfer-coding. If the message does include a transfer-coding, the Content-Length <em class="bcp14">MUST</em> be ignored. 1220 </p> 1221 <p id="rfc.section.3.4.p.6">When a Content-Length is given in a message where a message-body is allowed, its field value <em class="bcp14">MUST</em> exactly match the number of OCTETs in the message-body. HTTP/1.1 user agents <em class="bcp14">MUST</em> notify the user when an invalid length is received and detected. 1222 </p> 1223 <h2 id="rfc.section.3.5"><a href="#rfc.section.3.5">3.5</a> <a id="general.header.fields" href="#general.header.fields">General Header Fields</a></h2> 1224 <p id="rfc.section.3.5.p.1">There are a few header fields which have general applicability for both request and response messages, but which do not apply 1226 1225 to the entity being transferred. These header fields apply only to the message being transmitted. 1227 1226 </p> 1228 1227 <div id="rfc.figure.u.31"></div><pre class="inline"><span id="rfc.iref.g.61"></span> <a href="#general.header.fields" class="smpl">general-header</a> = <a href="#abnf.dependencies" class="smpl">Cache-Control</a> ; <a href="#Part6" id="rfc.xref.Part6.5"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>, <a href="p6-cache.html#header.cache-control" title="Cache-Control">Section 16.2</a> 1229 / <a href="#header.connection" class="smpl">Connection</a> ; <a href="#header.connection" id="rfc.xref.header.connection.1" title="Connection">Section 8.1</a>1230 / <a href="#header.date" class="smpl">Date</a> ; <a href="#header.date" id="rfc.xref.header.date.1" title="Date">Section 8.3</a>1228 / <a href="#header.connection" class="smpl">Connection</a> ; <a href="#header.connection" id="rfc.xref.header.connection.1" title="Connection">Section 7.1</a> 1229 / <a href="#header.date" class="smpl">Date</a> ; <a href="#header.date" id="rfc.xref.header.date.1" title="Date">Section 7.3</a> 1231 1230 / <a href="#abnf.dependencies" class="smpl">Pragma</a> ; <a href="#Part6" id="rfc.xref.Part6.6"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>, <a href="p6-cache.html#header.pragma" title="Pragma">Section 16.4</a> 1232 / <a href="#header.trailer" class="smpl">Trailer</a> ; <a href="#header.trailer" id="rfc.xref.header.trailer.2" title="Trailer">Section 8.6</a>1233 / <a href="#header.transfer-encoding" class="smpl">Transfer-Encoding</a> ; <a href="#header.transfer-encoding" id="rfc.xref.header.transfer-encoding.4" title="Transfer-Encoding">Section 8.7</a>1234 / <a href="#header.upgrade" class="smpl">Upgrade</a> ; <a href="#header.upgrade" id="rfc.xref.header.upgrade.1" title="Upgrade">Section 8.8</a>1235 / <a href="#header.via" class="smpl">Via</a> ; <a href="#header.via" id="rfc.xref.header.via.1" title="Via">Section 8.9</a>1231 / <a href="#header.trailer" class="smpl">Trailer</a> ; <a href="#header.trailer" id="rfc.xref.header.trailer.2" title="Trailer">Section 7.6</a> 1232 / <a href="#header.transfer-encoding" class="smpl">Transfer-Encoding</a> ; <a href="#header.transfer-encoding" id="rfc.xref.header.transfer-encoding.4" title="Transfer-Encoding">Section 7.7</a> 1233 / <a href="#header.upgrade" class="smpl">Upgrade</a> ; <a href="#header.upgrade" id="rfc.xref.header.upgrade.1" title="Upgrade">Section 7.8</a> 1234 / <a href="#header.via" class="smpl">Via</a> ; <a href="#header.via" id="rfc.xref.header.via.1" title="Via">Section 7.9</a> 1236 1235 / <a href="#abnf.dependencies" class="smpl">Warning</a> ; <a href="#Part6" id="rfc.xref.Part6.7"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>, <a href="p6-cache.html#header.warning" title="Warning">Section 16.6</a> 1237 </pre><p id="rfc.section. 4.5.p.3">General-header field names can be extended reliably only in combination with a change in the protocol version. However, new1236 </pre><p id="rfc.section.3.5.p.3">General-header field names can be extended reliably only in combination with a change in the protocol version. However, new 1238 1237 or experimental header fields may be given the semantics of general header fields if all parties in the communication recognize 1239 1238 them to be general-header fields. Unrecognized header fields are treated as entity-header fields. 1240 1239 </p> 1241 <h1 id="rfc.section. 5"><a href="#rfc.section.5">5.</a> <a id="request" href="#request">Request</a></h1>1242 <p id="rfc.section. 5.p.1">A request message from a client to a server includes, within the first line of that message, the method to be applied to the1240 <h1 id="rfc.section.4"><a href="#rfc.section.4">4.</a> <a id="request" href="#request">Request</a></h1> 1241 <p id="rfc.section.4.p.1">A request message from a client to a server includes, within the first line of that message, the method to be applied to the 1243 1242 resource, the identifier of the resource, and the protocol version in use. 1244 1243 </p> 1245 <div id="rfc.figure.u.32"></div><pre class="inline"><span id="rfc.iref.g.62"></span> <a href="#request" class="smpl">Request</a> = <a href="#request-line" class="smpl">Request-Line</a> ; <a href="#request-line" title="Request-Line">Section 5.1</a>1246 *(( <a href="#general.header.fields" class="smpl">general-header</a> ; <a href="#general.header.fields" title="General Header Fields">Section 4.5</a>1244 <div id="rfc.figure.u.32"></div><pre class="inline"><span id="rfc.iref.g.62"></span> <a href="#request" class="smpl">Request</a> = <a href="#request-line" class="smpl">Request-Line</a> ; <a href="#request-line" title="Request-Line">Section 4.1</a> 1245 *(( <a href="#general.header.fields" class="smpl">general-header</a> ; <a href="#general.header.fields" title="General Header Fields">Section 3.5</a> 1247 1246 / <a href="#abnf.dependencies" class="smpl">request-header</a> ; <a href="#Part2" id="rfc.xref.Part2.7"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>, <a href="p2-semantics.html#request.header.fields" title="Request Header Fields">Section 4</a> 1248 1247 / <a href="#abnf.dependencies" class="smpl">entity-header</a> ) <a href="#core.rules" class="smpl">CRLF</a>) ; <a href="#Part3" id="rfc.xref.Part3.10"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>, <a href="p3-payload.html#entity.header.fields" title="Entity Header Fields">Section 4.1</a> 1249 1248 <a href="#core.rules" class="smpl">CRLF</a> 1250 [ <a href="#message.body" class="smpl">message-body</a> ] ; <a href="#message.body" title="Message Body">Section 4.3</a>1251 </pre><h2 id="rfc.section. 5.1"><a href="#rfc.section.5.1">5.1</a> <a id="request-line" href="#request-line">Request-Line</a></h2>1252 <p id="rfc.section. 5.1.p.1">The Request-Line begins with a method token, followed by the Request-URI and the protocol version, and ending with CRLF. The1249 [ <a href="#message.body" class="smpl">message-body</a> ] ; <a href="#message.body" title="Message Body">Section 3.3</a> 1250 </pre><h2 id="rfc.section.4.1"><a href="#rfc.section.4.1">4.1</a> <a id="request-line" href="#request-line">Request-Line</a></h2> 1251 <p id="rfc.section.4.1.p.1">The Request-Line begins with a method token, followed by the Request-URI and the protocol version, and ending with CRLF. The 1253 1252 elements are separated by SP characters. No CR or LF is allowed except in the final CRLF sequence. 1254 1253 </p> 1255 1254 <div id="rfc.figure.u.33"></div><pre class="inline"><span id="rfc.iref.g.63"></span> <a href="#request-line" class="smpl">Request-Line</a> = <a href="#method" class="smpl">Method</a> <a href="#core.rules" class="smpl">SP</a> <a href="#request-uri" class="smpl">Request-URI</a> <a href="#core.rules" class="smpl">SP</a> <a href="#http.version" class="smpl">HTTP-Version</a> <a href="#core.rules" class="smpl">CRLF</a> 1256 </pre><h3 id="rfc.section. 5.1.1"><a href="#rfc.section.5.1.1">5.1.1</a> <a id="method" href="#method">Method</a></h3>1257 <p id="rfc.section. 5.1.1.p.1">The Method token indicates the method to be performed on the resource identified by the Request-URI. The method is case-sensitive.</p>1255 </pre><h3 id="rfc.section.4.1.1"><a href="#rfc.section.4.1.1">4.1.1</a> <a id="method" href="#method">Method</a></h3> 1256 <p id="rfc.section.4.1.1.p.1">The Method token indicates the method to be performed on the resource identified by the Request-URI. The method is case-sensitive.</p> 1258 1257 <div id="rfc.figure.u.34"></div><pre class="inline"><span id="rfc.iref.g.64"></span><span id="rfc.iref.g.65"></span> <a href="#method" class="smpl">Method</a> = <a href="#rule.token.separators" class="smpl">token</a> 1259 </pre><h3 id="rfc.section. 5.1.2"><a href="#rfc.section.5.1.2">5.1.2</a> <a id="request-uri" href="#request-uri">Request-URI</a></h3>1260 <p id="rfc.section. 5.1.2.p.1">The Request-URI is a Uniform Resource Identifier (<a href="#uri" title="Uniform Resource Identifiers">Section 3.2</a>) and identifies the resource upon which to apply the request.1258 </pre><h3 id="rfc.section.4.1.2"><a href="#rfc.section.4.1.2">4.1.2</a> <a id="request-uri" href="#request-uri">Request-URI</a></h3> 1259 <p id="rfc.section.4.1.2.p.1">The Request-URI is a Uniform Resource Identifier (<a href="#uri" title="Uniform Resource Identifiers">Section 2.2</a>) and identifies the resource upon which to apply the request. 1261 1260 </p> 1262 1261 <div id="rfc.figure.u.35"></div><pre class="inline"><span id="rfc.iref.g.66"></span> <a href="#request-uri" class="smpl">Request-URI</a> = "*" … … 1264 1263 / ( <a href="#uri" class="smpl">path-absolute</a> [ "?" <a href="#uri" class="smpl">query</a> ] ) 1265 1264 / <a href="#uri" class="smpl">authority</a> 1266 </pre><p id="rfc.section. 5.1.2.p.3">The four options for Request-URI are dependent on the nature of the request. The asterisk "*" means that the request does1265 </pre><p id="rfc.section.4.1.2.p.3">The four options for Request-URI are dependent on the nature of the request. The asterisk "*" means that the request does 1267 1266 not apply to a particular resource, but to the server itself, and is only allowed when the method used does not necessarily 1268 1267 apply to a resource. One example would be 1269 1268 </p> 1270 1269 <div id="rfc.figure.u.36"></div><pre class="text"> OPTIONS * HTTP/1.1 1271 </pre><p id="rfc.section. 5.1.2.p.5">The absolute-URI form is <em class="bcp14">REQUIRED</em> when the request is being made to a proxy. The proxy is requested to forward the request or service it from a valid cache,1270 </pre><p id="rfc.section.4.1.2.p.5">The absolute-URI form is <em class="bcp14">REQUIRED</em> when the request is being made to a proxy. The proxy is requested to forward the request or service it from a valid cache, 1272 1271 and return the response. Note that the proxy <em class="bcp14">MAY</em> forward the request on to another proxy or directly to the server specified by the absolute-URI. In order to avoid request 1273 1272 loops, a proxy <em class="bcp14">MUST</em> be able to recognize all of its server names, including any aliases, local variations, and the numeric IP address. An example … … 1275 1274 </p> 1276 1275 <div id="rfc.figure.u.37"></div><pre class="text"> GET http://www.example.org/pub/WWW/TheProject.html HTTP/1.1 1277 </pre><p id="rfc.section. 5.1.2.p.7">To allow for transition to absolute-URIs in all requests in future versions of HTTP, all HTTP/1.1 servers <em class="bcp14">MUST</em> accept the absolute-URI form in requests, even though HTTP/1.1 clients will only generate them in requests to proxies.1278 </p> 1279 <p id="rfc.section. 5.1.2.p.8">The authority form is only used by the CONNECT method (<a href="p2-semantics.html#CONNECT" title="CONNECT">Section 8.9</a> of <a href="#Part2" id="rfc.xref.Part2.8"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>).1280 </p> 1281 <p id="rfc.section. 5.1.2.p.9">The most common form of Request-URI is that used to identify a resource on an origin server or gateway. In this case the absolute1282 path of the URI <em class="bcp14">MUST</em> be transmitted (see <a href="#http.uri" title="http URI scheme">Section 3.2.1</a>, path-absolute) as the Request-URI, and the network location of the URI (authority) <em class="bcp14">MUST</em> be transmitted in a Host header field. For example, a client wishing to retrieve the resource above directly from the origin1276 </pre><p id="rfc.section.4.1.2.p.7">To allow for transition to absolute-URIs in all requests in future versions of HTTP, all HTTP/1.1 servers <em class="bcp14">MUST</em> accept the absolute-URI form in requests, even though HTTP/1.1 clients will only generate them in requests to proxies. 1277 </p> 1278 <p id="rfc.section.4.1.2.p.8">The authority form is only used by the CONNECT method (<a href="p2-semantics.html#CONNECT" title="CONNECT">Section 8.9</a> of <a href="#Part2" id="rfc.xref.Part2.8"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>). 1279 </p> 1280 <p id="rfc.section.4.1.2.p.9">The most common form of Request-URI is that used to identify a resource on an origin server or gateway. In this case the absolute 1281 path of the URI <em class="bcp14">MUST</em> be transmitted (see <a href="#http.uri" title="http URI scheme">Section 2.2.1</a>, path-absolute) as the Request-URI, and the network location of the URI (authority) <em class="bcp14">MUST</em> be transmitted in a Host header field. For example, a client wishing to retrieve the resource above directly from the origin 1283 1282 server would create a TCP connection to port 80 of the host "www.example.org" and send the lines: 1284 1283 </p> 1285 1284 <div id="rfc.figure.u.38"></div><pre class="text"> GET /pub/WWW/TheProject.html HTTP/1.1 1286 1285 Host: www.example.org 1287 </pre><p id="rfc.section. 5.1.2.p.11">followed by the remainder of the Request. Note that the absolute path cannot be empty; if none is present in the original1286 </pre><p id="rfc.section.4.1.2.p.11">followed by the remainder of the Request. Note that the absolute path cannot be empty; if none is present in the original 1288 1287 URI, it <em class="bcp14">MUST</em> be given as "/" (the server root). 1289 1288 </p> 1290 <p id="rfc.section. 5.1.2.p.12">The Request-URI is transmitted in the format specified in <a href="#http.uri" title="http URI scheme">Section 3.2.1</a>. If the Request-URI is encoded using the "% <a href="#core.rules" class="smpl">HEXDIG</a> <a href="#core.rules" class="smpl">HEXDIG</a>" encoding (<a href="#RFC3986" id="rfc.xref.RFC3986.14"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a>, <a href="http://tools.ietf.org/html/rfc3986#section-2.4">Section 2.4</a>), the origin server <em class="bcp14">MUST</em> decode the Request-URI in order to properly interpret the request. Servers <em class="bcp14">SHOULD</em> respond to invalid Request-URIs with an appropriate status code.1291 </p> 1292 <p id="rfc.section. 5.1.2.p.13">A transparent proxy <em class="bcp14">MUST NOT</em> rewrite the "path-absolute" part of the received Request-URI when forwarding it to the next inbound server, except as noted1289 <p id="rfc.section.4.1.2.p.12">The Request-URI is transmitted in the format specified in <a href="#http.uri" title="http URI scheme">Section 2.2.1</a>. If the Request-URI is encoded using the "% <a href="#core.rules" class="smpl">HEXDIG</a> <a href="#core.rules" class="smpl">HEXDIG</a>" encoding (<a href="#RFC3986" id="rfc.xref.RFC3986.14"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a>, <a href="http://tools.ietf.org/html/rfc3986#section-2.4">Section 2.4</a>), the origin server <em class="bcp14">MUST</em> decode the Request-URI in order to properly interpret the request. Servers <em class="bcp14">SHOULD</em> respond to invalid Request-URIs with an appropriate status code. 1290 </p> 1291 <p id="rfc.section.4.1.2.p.13">A transparent proxy <em class="bcp14">MUST NOT</em> rewrite the "path-absolute" part of the received Request-URI when forwarding it to the next inbound server, except as noted 1293 1292 above to replace a null path-absolute with "/". 1294 1293 </p> 1295 <p id="rfc.section. 5.1.2.p.14"> </p>1294 <p id="rfc.section.4.1.2.p.14"> </p> 1296 1295 <dl class="empty"> 1297 1296 <dd> <b>Note:</b> The "no rewrite" rule prevents the proxy from changing the meaning of the request when the origin server is improperly using … … 1300 1299 </dd> 1301 1300 </dl> 1302 <h2 id="rfc.section. 5.2"><a href="#rfc.section.5.2">5.2</a> <a id="the.resource.identified.by.a.request" href="#the.resource.identified.by.a.request">The Resource Identified by a Request</a></h2>1303 <p id="rfc.section. 5.2.p.1">The exact resource identified by an Internet request is determined by examining both the Request-URI and the Host header field.</p>1304 <p id="rfc.section. 5.2.p.2">An origin server that does not allow resources to differ by the requested host <em class="bcp14">MAY</em> ignore the Host header field value when determining the resource identified by an HTTP/1.1 request. (But see <a href="#changes.to.simplify.multi-homed.web.servers.and.conserve.ip.addresses" title="Changes to Simplify Multi-homed Web Servers and Conserve IP Addresses">Appendix B.1.1</a> for other requirements on Host support in HTTP/1.1.)1305 </p> 1306 <p id="rfc.section. 5.2.p.3">An origin server that does differentiate resources based on the host requested (sometimes referred to as virtual hosts or1301 <h2 id="rfc.section.4.2"><a href="#rfc.section.4.2">4.2</a> <a id="the.resource.identified.by.a.request" href="#the.resource.identified.by.a.request">The Resource Identified by a Request</a></h2> 1302 <p id="rfc.section.4.2.p.1">The exact resource identified by an Internet request is determined by examining both the Request-URI and the Host header field.</p> 1303 <p id="rfc.section.4.2.p.2">An origin server that does not allow resources to differ by the requested host <em class="bcp14">MAY</em> ignore the Host header field value when determining the resource identified by an HTTP/1.1 request. (But see <a href="#changes.to.simplify.multi-homed.web.servers.and.conserve.ip.addresses" title="Changes to Simplify Multi-homed Web Servers and Conserve IP Addresses">Appendix B.1.1</a> for other requirements on Host support in HTTP/1.1.) 1304 </p> 1305 <p id="rfc.section.4.2.p.3">An origin server that does differentiate resources based on the host requested (sometimes referred to as virtual hosts or 1307 1306 vanity host names) <em class="bcp14">MUST</em> use the following rules for determining the requested resource on an HTTP/1.1 request: 1308 1307 </p> … … 1316 1315 </li> 1317 1316 </ol> 1318 <p id="rfc.section. 5.2.p.4">Recipients of an HTTP/1.0 request that lacks a Host header field <em class="bcp14">MAY</em> attempt to use heuristics (e.g., examination of the URI path for something unique to a particular host) in order to determine1317 <p id="rfc.section.4.2.p.4">Recipients of an HTTP/1.0 request that lacks a Host header field <em class="bcp14">MAY</em> attempt to use heuristics (e.g., examination of the URI path for something unique to a particular host) in order to determine 1319 1318 what exact resource is being requested. 1320 1319 </p> 1321 <h1 id="rfc.section. 6"><a href="#rfc.section.6">6.</a> <a id="response" href="#response">Response</a></h1>1322 <p id="rfc.section. 6.p.1">After receiving and interpreting a request message, a server responds with an HTTP response message.</p>1323 <div id="rfc.figure.u.39"></div><pre class="inline"><span id="rfc.iref.g.67"></span> <a href="#response" class="smpl">Response</a> = <a href="#status-line" class="smpl">Status-Line</a> ; <a href="#status-line" title="Status-Line">Section 6.1</a>1324 *(( <a href="#general.header.fields" class="smpl">general-header</a> ; <a href="#general.header.fields" title="General Header Fields">Section 4.5</a>1320 <h1 id="rfc.section.5"><a href="#rfc.section.5">5.</a> <a id="response" href="#response">Response</a></h1> 1321 <p id="rfc.section.5.p.1">After receiving and interpreting a request message, a server responds with an HTTP response message.</p> 1322 <div id="rfc.figure.u.39"></div><pre class="inline"><span id="rfc.iref.g.67"></span> <a href="#response" class="smpl">Response</a> = <a href="#status-line" class="smpl">Status-Line</a> ; <a href="#status-line" title="Status-Line">Section 5.1</a> 1323 *(( <a href="#general.header.fields" class="smpl">general-header</a> ; <a href="#general.header.fields" title="General Header Fields">Section 3.5</a> 1325 1324 / <a href="#abnf.dependencies" class="smpl">response-header</a> ; <a href="#Part2" id="rfc.xref.Part2.9"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>, <a href="p2-semantics.html#response.header.fields" title="Response Header Fields">Section 6</a> 1326 1325 / <a href="#abnf.dependencies" class="smpl">entity-header</a> ) <a href="#core.rules" class="smpl">CRLF</a>) ; <a href="#Part3" id="rfc.xref.Part3.11"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>, <a href="p3-payload.html#entity.header.fields" title="Entity Header Fields">Section 4.1</a> 1327 1326 <a href="#core.rules" class="smpl">CRLF</a> 1328 [ <a href="#message.body" class="smpl">message-body</a> ] ; <a href="#message.body" title="Message Body">Section 4.3</a>1329 </pre><h2 id="rfc.section. 6.1"><a href="#rfc.section.6.1">6.1</a> <a id="status-line" href="#status-line">Status-Line</a></h2>1330 <p id="rfc.section. 6.1.p.1">The first line of a Response message is the Status-Line, consisting of the protocol version followed by a numeric status code1327 [ <a href="#message.body" class="smpl">message-body</a> ] ; <a href="#message.body" title="Message Body">Section 3.3</a> 1328 </pre><h2 id="rfc.section.5.1"><a href="#rfc.section.5.1">5.1</a> <a id="status-line" href="#status-line">Status-Line</a></h2> 1329 <p id="rfc.section.5.1.p.1">The first line of a Response message is the Status-Line, consisting of the protocol version followed by a numeric status code 1331 1330 and its associated textual phrase, with each element separated by SP characters. No CR or LF is allowed except in the final 1332 1331 CRLF sequence. 1333 1332 </p> 1334 1333 <div id="rfc.figure.u.40"></div><pre class="inline"><span id="rfc.iref.g.68"></span> <a href="#status-line" class="smpl">Status-Line</a> = <a href="#http.version" class="smpl">HTTP-Version</a> <a href="#core.rules" class="smpl">SP</a> <a href="#status.code.and.reason.phrase" class="smpl">Status-Code</a> <a href="#core.rules" class="smpl">SP</a> <a href="#status.code.and.reason.phrase" class="smpl">Reason-Phrase</a> <a href="#core.rules" class="smpl">CRLF</a> 1335 </pre><h3 id="rfc.section. 6.1.1"><a href="#rfc.section.6.1.1">6.1.1</a> <a id="status.code.and.reason.phrase" href="#status.code.and.reason.phrase">Status Code and Reason Phrase</a></h3>1336 <p id="rfc.section. 6.1.1.p.1">The Status-Code element is a 3-digit integer result code of the attempt to understand and satisfy the request. These codes1334 </pre><h3 id="rfc.section.5.1.1"><a href="#rfc.section.5.1.1">5.1.1</a> <a id="status.code.and.reason.phrase" href="#status.code.and.reason.phrase">Status Code and Reason Phrase</a></h3> 1335 <p id="rfc.section.5.1.1.p.1">The Status-Code element is a 3-digit integer result code of the attempt to understand and satisfy the request. These codes 1337 1336 are fully defined in <a href="p2-semantics.html#status.codes" title="Status Code Definitions">Section 9</a> of <a href="#Part2" id="rfc.xref.Part2.10"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>. The Reason Phrase exists for the sole purpose of providing a textual description associated with the numeric status code, 1338 1337 out of deference to earlier Internet application protocols that were more frequently used with interactive text clients. A 1339 1338 client <em class="bcp14">SHOULD</em> ignore the content of the Reason Phrase. 1340 1339 </p> 1341 <p id="rfc.section. 6.1.1.p.2">The first digit of the Status-Code defines the class of response. The last two digits do not have any categorization role.1340 <p id="rfc.section.5.1.1.p.2">The first digit of the Status-Code defines the class of response. The last two digits do not have any categorization role. 1342 1341 There are 5 values for the first digit: 1343 1342 </p> … … 1351 1350 <div id="rfc.figure.u.41"></div><pre class="inline"><span id="rfc.iref.g.69"></span><span id="rfc.iref.g.70"></span><span id="rfc.iref.g.71"></span> <a href="#status.code.and.reason.phrase" class="smpl">Status-Code</a> = 3<a href="#core.rules" class="smpl">DIGIT</a> 1352 1351 <a href="#status.code.and.reason.phrase" class="smpl">Reason-Phrase</a> = *<<a href="#rule.TEXT" class="smpl">TEXT</a>, excluding <a href="#core.rules" class="smpl">CR</a>, <a href="#core.rules" class="smpl">LF</a>> 1353 </pre><h1 id="rfc.section. 7"><a href="#rfc.section.7">7.</a> <a id="connections" href="#connections">Connections</a></h1>1354 <h2 id="rfc.section. 7.1"><a href="#rfc.section.7.1">7.1</a> <a id="persistent.connections" href="#persistent.connections">Persistent Connections</a></h2>1355 <h3 id="rfc.section. 7.1.1"><a href="#rfc.section.7.1.1">7.1.1</a> <a id="persistent.purpose" href="#persistent.purpose">Purpose</a></h3>1356 <p id="rfc.section. 7.1.1.p.1">Prior to persistent connections, a separate TCP connection was established to fetch each URL, increasing the load on HTTP1352 </pre><h1 id="rfc.section.6"><a href="#rfc.section.6">6.</a> <a id="connections" href="#connections">Connections</a></h1> 1353 <h2 id="rfc.section.6.1"><a href="#rfc.section.6.1">6.1</a> <a id="persistent.connections" href="#persistent.connections">Persistent Connections</a></h2> 1354 <h3 id="rfc.section.6.1.1"><a href="#rfc.section.6.1.1">6.1.1</a> <a id="persistent.purpose" href="#persistent.purpose">Purpose</a></h3> 1355 <p id="rfc.section.6.1.1.p.1">Prior to persistent connections, a separate TCP connection was established to fetch each URL, increasing the load on HTTP 1357 1356 servers and causing congestion on the Internet. The use of inline images and other associated data often require a client 1358 1357 to make multiple requests of the same server in a short amount of time. Analysis of these performance problems and results 1359 1358 from a prototype implementation are available <a href="#Pad1995" id="rfc.xref.Pad1995.1"><cite title="Improving HTTP Latency">[Pad1995]</cite></a> <a href="#Spe" id="rfc.xref.Spe.1"><cite title="Analysis of HTTP Performance Problems">[Spe]</cite></a>. Implementation experience and measurements of actual HTTP/1.1 (<cite title="Hypertext Transfer Protocol -- HTTP/1.1" id="rfc.xref.RFC2068.2">RFC 2068</cite>) implementations show good results <a href="#Nie1997" id="rfc.xref.Nie1997.1"><cite title="Network Performance Effects of HTTP/1.1, CSS1, and PNG">[Nie1997]</cite></a>. Alternatives have also been explored, for example, T/TCP <a href="#Tou1998" id="rfc.xref.Tou1998.1"><cite title="Analysis of HTTP Performance">[Tou1998]</cite></a>. 1360 1359 </p> 1361 <p id="rfc.section. 7.1.1.p.2">Persistent HTTP connections have a number of advantages: </p>1360 <p id="rfc.section.6.1.1.p.2">Persistent HTTP connections have a number of advantages: </p> 1362 1361 <ul> 1363 1362 <li>By opening and closing fewer TCP connections, CPU time is saved in routers and hosts (clients, servers, proxies, gateways, … … 1376 1375 </li> 1377 1376 </ul> 1378 <p id="rfc.section. 7.1.1.p.3">HTTP implementations <em class="bcp14">SHOULD</em> implement persistent connections.1379 </p> 1380 <h3 id="rfc.section. 7.1.2"><a href="#rfc.section.7.1.2">7.1.2</a> <a id="persistent.overall" href="#persistent.overall">Overall Operation</a></h3>1381 <p id="rfc.section. 7.1.2.p.1">A significant difference between HTTP/1.1 and earlier versions of HTTP is that persistent connections are the default behavior1377 <p id="rfc.section.6.1.1.p.3">HTTP implementations <em class="bcp14">SHOULD</em> implement persistent connections. 1378 </p> 1379 <h3 id="rfc.section.6.1.2"><a href="#rfc.section.6.1.2">6.1.2</a> <a id="persistent.overall" href="#persistent.overall">Overall Operation</a></h3> 1380 <p id="rfc.section.6.1.2.p.1">A significant difference between HTTP/1.1 and earlier versions of HTTP is that persistent connections are the default behavior 1382 1381 of any HTTP connection. That is, unless otherwise indicated, the client <em class="bcp14">SHOULD</em> assume that the server will maintain a persistent connection, even after error responses from the server. 1383 1382 </p> 1384 <p id="rfc.section. 7.1.2.p.2">Persistent connections provide a mechanism by which a client and a server can signal the close of a TCP connection. This signaling1385 takes place using the Connection header field (<a href="#header.connection" id="rfc.xref.header.connection.2" title="Connection">Section 8.1</a>). Once a close has been signaled, the client <em class="bcp14">MUST NOT</em> send any more requests on that connection.1386 </p> 1387 <h4 id="rfc.section. 7.1.2.1"><a href="#rfc.section.7.1.2.1">7.1.2.1</a> <a id="persistent.negotiation" href="#persistent.negotiation">Negotiation</a></h4>1388 <p id="rfc.section. 7.1.2.1.p.1">An HTTP/1.1 server <em class="bcp14">MAY</em> assume that a HTTP/1.1 client intends to maintain a persistent connection unless a Connection header including the connection-token1383 <p id="rfc.section.6.1.2.p.2">Persistent connections provide a mechanism by which a client and a server can signal the close of a TCP connection. This signaling 1384 takes place using the Connection header field (<a href="#header.connection" id="rfc.xref.header.connection.2" title="Connection">Section 7.1</a>). Once a close has been signaled, the client <em class="bcp14">MUST NOT</em> send any more requests on that connection. 1385 </p> 1386 <h4 id="rfc.section.6.1.2.1"><a href="#rfc.section.6.1.2.1">6.1.2.1</a> <a id="persistent.negotiation" href="#persistent.negotiation">Negotiation</a></h4> 1387 <p id="rfc.section.6.1.2.1.p.1">An HTTP/1.1 server <em class="bcp14">MAY</em> assume that a HTTP/1.1 client intends to maintain a persistent connection unless a Connection header including the connection-token 1389 1388 "close" was sent in the request. If the server chooses to close the connection immediately after sending the response, it <em class="bcp14">SHOULD</em> send a Connection header including the connection-token close. 1390 1389 </p> 1391 <p id="rfc.section. 7.1.2.1.p.2">An HTTP/1.1 client <em class="bcp14">MAY</em> expect a connection to remain open, but would decide to keep it open based on whether the response from a server contains1390 <p id="rfc.section.6.1.2.1.p.2">An HTTP/1.1 client <em class="bcp14">MAY</em> expect a connection to remain open, but would decide to keep it open based on whether the response from a server contains 1392 1391 a Connection header with the connection-token close. In case the client does not want to maintain a connection for more than 1393 1392 that request, it <em class="bcp14">SHOULD</em> send a Connection header including the connection-token close. 1394 1393 </p> 1395 <p id="rfc.section. 7.1.2.1.p.3">If either the client or the server sends the close token in the Connection header, that request becomes the last one for the1394 <p id="rfc.section.6.1.2.1.p.3">If either the client or the server sends the close token in the Connection header, that request becomes the last one for the 1396 1395 connection. 1397 1396 </p> 1398 <p id="rfc.section. 7.1.2.1.p.4">Clients and servers <em class="bcp14">SHOULD NOT</em> assume that a persistent connection is maintained for HTTP versions less than 1.1 unless it is explicitly signaled. See <a href="#compatibility.with.http.1.0.persistent.connections" title="Compatibility with HTTP/1.0 Persistent Connections">Appendix B.2</a> for more information on backward compatibility with HTTP/1.0 clients.1399 </p> 1400 <p id="rfc.section. 7.1.2.1.p.5">In order to remain persistent, all messages on the connection <em class="bcp14">MUST</em> have a self-defined message length (i.e., one not defined by closure of the connection), as described in <a href="#message.length" title="Message Length">Section 4.4</a>.1401 </p> 1402 <h4 id="rfc.section. 7.1.2.2"><a href="#rfc.section.7.1.2.2">7.1.2.2</a> <a id="pipelining" href="#pipelining">Pipelining</a></h4>1403 <p id="rfc.section. 7.1.2.2.p.1">A client that supports persistent connections <em class="bcp14">MAY</em> "pipeline" its requests (i.e., send multiple requests without waiting for each response). A server <em class="bcp14">MUST</em> send its responses to those requests in the same order that the requests were received.1404 </p> 1405 <p id="rfc.section. 7.1.2.2.p.2">Clients which assume persistent connections and pipeline immediately after connection establishment <em class="bcp14">SHOULD</em> be prepared to retry their connection if the first pipelined attempt fails. If a client does such a retry, it <em class="bcp14">MUST NOT</em> pipeline before it knows the connection is persistent. Clients <em class="bcp14">MUST</em> also be prepared to resend their requests if the server closes the connection before sending all of the corresponding responses.1406 </p> 1407 <p id="rfc.section. 7.1.2.2.p.3">Clients <em class="bcp14">SHOULD NOT</em> pipeline requests using non-idempotent methods or non-idempotent sequences of methods (see <a href="p2-semantics.html#idempotent.methods" title="Idempotent Methods">Section 8.1.2</a> of <a href="#Part2" id="rfc.xref.Part2.11"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>). Otherwise, a premature termination of the transport connection could lead to indeterminate results. A client wishing to1397 <p id="rfc.section.6.1.2.1.p.4">Clients and servers <em class="bcp14">SHOULD NOT</em> assume that a persistent connection is maintained for HTTP versions less than 1.1 unless it is explicitly signaled. See <a href="#compatibility.with.http.1.0.persistent.connections" title="Compatibility with HTTP/1.0 Persistent Connections">Appendix B.2</a> for more information on backward compatibility with HTTP/1.0 clients. 1398 </p> 1399 <p id="rfc.section.6.1.2.1.p.5">In order to remain persistent, all messages on the connection <em class="bcp14">MUST</em> have a self-defined message length (i.e., one not defined by closure of the connection), as described in <a href="#message.length" title="Message Length">Section 3.4</a>. 1400 </p> 1401 <h4 id="rfc.section.6.1.2.2"><a href="#rfc.section.6.1.2.2">6.1.2.2</a> <a id="pipelining" href="#pipelining">Pipelining</a></h4> 1402 <p id="rfc.section.6.1.2.2.p.1">A client that supports persistent connections <em class="bcp14">MAY</em> "pipeline" its requests (i.e., send multiple requests without waiting for each response). A server <em class="bcp14">MUST</em> send its responses to those requests in the same order that the requests were received. 1403 </p> 1404 <p id="rfc.section.6.1.2.2.p.2">Clients which assume persistent connections and pipeline immediately after connection establishment <em class="bcp14">SHOULD</em> be prepared to retry their connection if the first pipelined attempt fails. If a client does such a retry, it <em class="bcp14">MUST NOT</em> pipeline before it knows the connection is persistent. Clients <em class="bcp14">MUST</em> also be prepared to resend their requests if the server closes the connection before sending all of the corresponding responses. 1405 </p> 1406 <p id="rfc.section.6.1.2.2.p.3">Clients <em class="bcp14">SHOULD NOT</em> pipeline requests using non-idempotent methods or non-idempotent sequences of methods (see <a href="p2-semantics.html#idempotent.methods" title="Idempotent Methods">Section 8.1.2</a> of <a href="#Part2" id="rfc.xref.Part2.11"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>). Otherwise, a premature termination of the transport connection could lead to indeterminate results. A client wishing to 1408 1407 send a non-idempotent request <em class="bcp14">SHOULD</em> wait to send that request until it has received the response status for the previous request. 1409 1408 </p> 1410 <h3 id="rfc.section. 7.1.3"><a href="#rfc.section.7.1.3">7.1.3</a> <a id="persistent.proxy" href="#persistent.proxy">Proxy Servers</a></h3>1411 <p id="rfc.section. 7.1.3.p.1">It is especially important that proxies correctly implement the properties of the Connection header field as specified in <a href="#header.connection" id="rfc.xref.header.connection.3" title="Connection">Section 8.1</a>.1412 </p> 1413 <p id="rfc.section. 7.1.3.p.2">The proxy server <em class="bcp14">MUST</em> signal persistent connections separately with its clients and the origin servers (or other proxy servers) that it connects1409 <h3 id="rfc.section.6.1.3"><a href="#rfc.section.6.1.3">6.1.3</a> <a id="persistent.proxy" href="#persistent.proxy">Proxy Servers</a></h3> 1410 <p id="rfc.section.6.1.3.p.1">It is especially important that proxies correctly implement the properties of the Connection header field as specified in <a href="#header.connection" id="rfc.xref.header.connection.3" title="Connection">Section 7.1</a>. 1411 </p> 1412 <p id="rfc.section.6.1.3.p.2">The proxy server <em class="bcp14">MUST</em> signal persistent connections separately with its clients and the origin servers (or other proxy servers) that it connects 1414 1413 to. Each persistent connection applies to only one transport link. 1415 1414 </p> 1416 <p id="rfc.section. 7.1.3.p.3">A proxy server <em class="bcp14">MUST NOT</em> establish a HTTP/1.1 persistent connection with an HTTP/1.0 client (but see <a href="#RFC2068" id="rfc.xref.RFC2068.3"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2068]</cite></a> for information and discussion of the problems with the Keep-Alive header implemented by many HTTP/1.0 clients).1417 </p> 1418 <h3 id="rfc.section. 7.1.4"><a href="#rfc.section.7.1.4">7.1.4</a> <a id="persistent.practical" href="#persistent.practical">Practical Considerations</a></h3>1419 <p id="rfc.section. 7.1.4.p.1">Servers will usually have some time-out value beyond which they will no longer maintain an inactive connection. Proxy servers1415 <p id="rfc.section.6.1.3.p.3">A proxy server <em class="bcp14">MUST NOT</em> establish a HTTP/1.1 persistent connection with an HTTP/1.0 client (but see <a href="#RFC2068" id="rfc.xref.RFC2068.3"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2068]</cite></a> for information and discussion of the problems with the Keep-Alive header implemented by many HTTP/1.0 clients). 1416 </p> 1417 <h3 id="rfc.section.6.1.4"><a href="#rfc.section.6.1.4">6.1.4</a> <a id="persistent.practical" href="#persistent.practical">Practical Considerations</a></h3> 1418 <p id="rfc.section.6.1.4.p.1">Servers will usually have some time-out value beyond which they will no longer maintain an inactive connection. Proxy servers 1420 1419 might make this a higher value since it is likely that the client will be making more connections through the same server. 1421 1420 The use of persistent connections places no requirements on the length (or existence) of this time-out for either the client 1422 1421 or the server. 1423 1422 </p> 1424 <p id="rfc.section. 7.1.4.p.2">When a client or server wishes to time-out it <em class="bcp14">SHOULD</em> issue a graceful close on the transport connection. Clients and servers <em class="bcp14">SHOULD</em> both constantly watch for the other side of the transport close, and respond to it as appropriate. If a client or server does1423 <p id="rfc.section.6.1.4.p.2">When a client or server wishes to time-out it <em class="bcp14">SHOULD</em> issue a graceful close on the transport connection. Clients and servers <em class="bcp14">SHOULD</em> both constantly watch for the other side of the transport close, and respond to it as appropriate. If a client or server does 1425 1424 not detect the other side's close promptly it could cause unnecessary resource drain on the network. 1426 1425 </p> 1427 <p id="rfc.section. 7.1.4.p.3">A client, server, or proxy <em class="bcp14">MAY</em> close the transport connection at any time. For example, a client might have started to send a new request at the same time1426 <p id="rfc.section.6.1.4.p.3">A client, server, or proxy <em class="bcp14">MAY</em> close the transport connection at any time. For example, a client might have started to send a new request at the same time 1428 1427 that the server has decided to close the "idle" connection. From the server's point of view, the connection is being closed 1429 1428 while it was idle, but from the client's point of view, a request is in progress. 1430 1429 </p> 1431 <p id="rfc.section. 7.1.4.p.4">This means that clients, servers, and proxies <em class="bcp14">MUST</em> be able to recover from asynchronous close events. Client software <em class="bcp14">SHOULD</em> reopen the transport connection and retransmit the aborted sequence of requests without user interaction so long as the request1430 <p id="rfc.section.6.1.4.p.4">This means that clients, servers, and proxies <em class="bcp14">MUST</em> be able to recover from asynchronous close events. Client software <em class="bcp14">SHOULD</em> reopen the transport connection and retransmit the aborted sequence of requests without user interaction so long as the request 1432 1431 sequence is idempotent (see <a href="p2-semantics.html#idempotent.methods" title="Idempotent Methods">Section 8.1.2</a> of <a href="#Part2" id="rfc.xref.Part2.12"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>). Non-idempotent methods or sequences <em class="bcp14">MUST NOT</em> be automatically retried, although user agents <em class="bcp14">MAY</em> offer a human operator the choice of retrying the request(s). Confirmation by user-agent software with semantic understanding 1433 1432 of the application <em class="bcp14">MAY</em> substitute for user confirmation. The automatic retry <em class="bcp14">SHOULD NOT</em> be repeated if the second sequence of requests fails. 1434 1433 </p> 1435 <p id="rfc.section. 7.1.4.p.5">Servers <em class="bcp14">SHOULD</em> always respond to at least one request per connection, if at all possible. Servers <em class="bcp14">SHOULD NOT</em> close a connection in the middle of transmitting a response, unless a network or client failure is suspected.1436 </p> 1437 <p id="rfc.section. 7.1.4.p.6">Clients that use persistent connections <em class="bcp14">SHOULD</em> limit the number of simultaneous connections that they maintain to a given server. A single-user client <em class="bcp14">SHOULD NOT</em> maintain more than 2 connections with any server or proxy. A proxy <em class="bcp14">SHOULD</em> use up to 2*N connections to another server or proxy, where N is the number of simultaneously active users. These guidelines1434 <p id="rfc.section.6.1.4.p.5">Servers <em class="bcp14">SHOULD</em> always respond to at least one request per connection, if at all possible. Servers <em class="bcp14">SHOULD NOT</em> close a connection in the middle of transmitting a response, unless a network or client failure is suspected. 1435 </p> 1436 <p id="rfc.section.6.1.4.p.6">Clients that use persistent connections <em class="bcp14">SHOULD</em> limit the number of simultaneous connections that they maintain to a given server. A single-user client <em class="bcp14">SHOULD NOT</em> maintain more than 2 connections with any server or proxy. A proxy <em class="bcp14">SHOULD</em> use up to 2*N connections to another server or proxy, where N is the number of simultaneously active users. These guidelines 1438 1437 are intended to improve HTTP response times and avoid congestion. 1439 1438 </p> 1440 <h2 id="rfc.section. 7.2"><a href="#rfc.section.7.2">7.2</a> <a id="message.transmission.requirements" href="#message.transmission.requirements">Message Transmission Requirements</a></h2>1441 <h3 id="rfc.section. 7.2.1"><a href="#rfc.section.7.2.1">7.2.1</a> <a id="persistent.flow" href="#persistent.flow">Persistent Connections and Flow Control</a></h3>1442 <p id="rfc.section. 7.2.1.p.1">HTTP/1.1 servers <em class="bcp14">SHOULD</em> maintain persistent connections and use TCP's flow control mechanisms to resolve temporary overloads, rather than terminating1439 <h2 id="rfc.section.6.2"><a href="#rfc.section.6.2">6.2</a> <a id="message.transmission.requirements" href="#message.transmission.requirements">Message Transmission Requirements</a></h2> 1440 <h3 id="rfc.section.6.2.1"><a href="#rfc.section.6.2.1">6.2.1</a> <a id="persistent.flow" href="#persistent.flow">Persistent Connections and Flow Control</a></h3> 1441 <p id="rfc.section.6.2.1.p.1">HTTP/1.1 servers <em class="bcp14">SHOULD</em> maintain persistent connections and use TCP's flow control mechanisms to resolve temporary overloads, rather than terminating 1443 1442 connections with the expectation that clients will retry. The latter technique can exacerbate network congestion. 1444 1443 </p> 1445 <h3 id="rfc.section. 7.2.2"><a href="#rfc.section.7.2.2">7.2.2</a> <a id="persistent.monitor" href="#persistent.monitor">Monitoring Connections for Error Status Messages</a></h3>1446 <p id="rfc.section. 7.2.2.p.1">An HTTP/1.1 (or later) client sending a message-body <em class="bcp14">SHOULD</em> monitor the network connection for an error status while it is transmitting the request. If the client sees an error status,1447 it <em class="bcp14">SHOULD</em> immediately cease transmitting the body. If the body is being sent using a "chunked" encoding (<a href="#transfer.codings" title="Transfer Codings">Section 3.4</a>), a zero length chunk and empty trailer <em class="bcp14">MAY</em> be used to prematurely mark the end of the message. If the body was preceded by a Content-Length header, the client <em class="bcp14">MUST</em> close the connection.1448 </p> 1449 <h3 id="rfc.section. 7.2.3"><a href="#rfc.section.7.2.3">7.2.3</a> <a id="use.of.the.100.status" href="#use.of.the.100.status">Use of the 100 (Continue) Status</a></h3>1450 <p id="rfc.section. 7.2.3.p.1">The purpose of the 100 (Continue) status (see <a href="p2-semantics.html#status.100" title="100 Continue">Section 9.1.1</a> of <a href="#Part2" id="rfc.xref.Part2.13"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>) is to allow a client that is sending a request message with a request body to determine if the origin server is willing1444 <h3 id="rfc.section.6.2.2"><a href="#rfc.section.6.2.2">6.2.2</a> <a id="persistent.monitor" href="#persistent.monitor">Monitoring Connections for Error Status Messages</a></h3> 1445 <p id="rfc.section.6.2.2.p.1">An HTTP/1.1 (or later) client sending a message-body <em class="bcp14">SHOULD</em> monitor the network connection for an error status while it is transmitting the request. If the client sees an error status, 1446 it <em class="bcp14">SHOULD</em> immediately cease transmitting the body. If the body is being sent using a "chunked" encoding (<a href="#transfer.codings" title="Transfer Codings">Section 2.4</a>), a zero length chunk and empty trailer <em class="bcp14">MAY</em> be used to prematurely mark the end of the message. If the body was preceded by a Content-Length header, the client <em class="bcp14">MUST</em> close the connection. 1447 </p> 1448 <h3 id="rfc.section.6.2.3"><a href="#rfc.section.6.2.3">6.2.3</a> <a id="use.of.the.100.status" href="#use.of.the.100.status">Use of the 100 (Continue) Status</a></h3> 1449 <p id="rfc.section.6.2.3.p.1">The purpose of the 100 (Continue) status (see <a href="p2-semantics.html#status.100" title="100 Continue">Section 9.1.1</a> of <a href="#Part2" id="rfc.xref.Part2.13"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>) is to allow a client that is sending a request message with a request body to determine if the origin server is willing 1451 1450 to accept the request (based on the request headers) before the client sends the request body. In some cases, it might either 1452 1451 be inappropriate or highly inefficient for the client to send the body if the server will reject the message without looking 1453 1452 at the body. 1454 1453 </p> 1455 <p id="rfc.section. 7.2.3.p.2">Requirements for HTTP/1.1 clients: </p>1454 <p id="rfc.section.6.2.3.p.2">Requirements for HTTP/1.1 clients: </p> 1456 1455 <ul> 1457 1456 <li>If a client will wait for a 100 (Continue) response before sending the request body, it <em class="bcp14">MUST</em> send an Expect request-header field (<a href="p2-semantics.html#header.expect" title="Expect">Section 10.2</a> of <a href="#Part2" id="rfc.xref.Part2.14"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>) with the "100-continue" expectation. … … 1460 1459 </li> 1461 1460 </ul> 1462 <p id="rfc.section. 7.2.3.p.3">Because of the presence of older implementations, the protocol allows ambiguous situations in which a client may send "Expect:1461 <p id="rfc.section.6.2.3.p.3">Because of the presence of older implementations, the protocol allows ambiguous situations in which a client may send "Expect: 1463 1462 100-continue" without receiving either a 417 (Expectation Failed) status or a 100 (Continue) status. Therefore, when a client 1464 1463 sends this header field to an origin server (possibly via a proxy) from which it has never seen a 100 (Continue) status, the 1465 1464 client <em class="bcp14">SHOULD NOT</em> wait for an indefinite period before sending the request body. 1466 1465 </p> 1467 <p id="rfc.section. 7.2.3.p.4">Requirements for HTTP/1.1 origin servers: </p>1466 <p id="rfc.section.6.2.3.p.4">Requirements for HTTP/1.1 origin servers: </p> 1468 1467 <ul> 1469 1468 <li>Upon receiving a request which includes an Expect request-header field with the "100-continue" expectation, an origin server <em class="bcp14">MUST</em> either respond with 100 (Continue) status and continue to read from the input stream, or respond with a final status code. … … 1489 1488 </li> 1490 1489 </ul> 1491 <p id="rfc.section. 7.2.3.p.5">Requirements for HTTP/1.1 proxies: </p>1490 <p id="rfc.section.6.2.3.p.5">Requirements for HTTP/1.1 proxies: </p> 1492 1491 <ul> 1493 1492 <li>If a proxy receives a request that includes an Expect request-header field with the "100-continue" expectation, and the proxy … … 1504 1503 </li> 1505 1504 </ul> 1506 <h3 id="rfc.section. 7.2.4"><a href="#rfc.section.7.2.4">7.2.4</a> <a id="connection.premature" href="#connection.premature">Client Behavior if Server Prematurely Closes Connection</a></h3>1507 <p id="rfc.section. 7.2.4.p.1">If an HTTP/1.1 client sends a request which includes a request body, but which does not include an Expect request-header field1505 <h3 id="rfc.section.6.2.4"><a href="#rfc.section.6.2.4">6.2.4</a> <a id="connection.premature" href="#connection.premature">Client Behavior if Server Prematurely Closes Connection</a></h3> 1506 <p id="rfc.section.6.2.4.p.1">If an HTTP/1.1 client sends a request which includes a request body, but which does not include an Expect request-header field 1508 1507 with the "100-continue" expectation, and if the client is not directly connected to an HTTP/1.1 origin server, and if the 1509 1508 client sees the connection close before receiving any status from the server, the client <em class="bcp14">SHOULD</em> retry the request. If the client does retry this request, it <em class="bcp14">MAY</em> use the following "binary exponential backoff" algorithm to be assured of obtaining a reliable response: … … 1522 1521 </li> 1523 1522 </ol> 1524 <p id="rfc.section. 7.2.4.p.2">If at any point an error status is received, the client </p>1523 <p id="rfc.section.6.2.4.p.2">If at any point an error status is received, the client </p> 1525 1524 <ul> 1526 1525 <li><em class="bcp14">SHOULD NOT</em> continue and … … 1529 1528 </li> 1530 1529 </ul> 1531 <h1 id="rfc.section. 8"><a href="#rfc.section.8">8.</a> <a id="header.fields" href="#header.fields">Header Field Definitions</a></h1>1532 <p id="rfc.section. 8.p.1">This section defines the syntax and semantics of HTTP/1.1 header fields related to message framing and transport protocols.</p>1533 <p id="rfc.section. 8.p.2">For entity-header fields, both sender and recipient refer to either the client or the server, depending on who sends and who1530 <h1 id="rfc.section.7"><a href="#rfc.section.7">7.</a> <a id="header.fields" href="#header.fields">Header Field Definitions</a></h1> 1531 <p id="rfc.section.7.p.1">This section defines the syntax and semantics of HTTP/1.1 header fields related to message framing and transport protocols.</p> 1532 <p id="rfc.section.7.p.2">For entity-header fields, both sender and recipient refer to either the client or the server, depending on who sends and who 1534 1533 receives the entity. 1535 1534 </p> 1536 1535 <div id="rfc.iref.c.1"></div> 1537 1536 <div id="rfc.iref.h.3"></div> 1538 <h2 id="rfc.section. 8.1"><a href="#rfc.section.8.1">8.1</a> <a id="header.connection" href="#header.connection">Connection</a></h2>1539 <p id="rfc.section. 8.1.p.1">The general-header field "Connection" allows the sender to specify options that are desired for that particular connection1537 <h2 id="rfc.section.7.1"><a href="#rfc.section.7.1">7.1</a> <a id="header.connection" href="#header.connection">Connection</a></h2> 1538 <p id="rfc.section.7.1.p.1">The general-header field "Connection" allows the sender to specify options that are desired for that particular connection 1540 1539 and <em class="bcp14">MUST NOT</em> be communicated by proxies over further connections. 1541 1540 </p> 1542 <p id="rfc.section. 8.1.p.2">The Connection header's value has the following grammar:</p>1541 <p id="rfc.section.7.1.p.2">The Connection header's value has the following grammar:</p> 1543 1542 <div id="rfc.figure.u.42"></div><pre class="inline"><span id="rfc.iref.g.72"></span><span id="rfc.iref.g.73"></span><span id="rfc.iref.g.74"></span> <a href="#header.connection" class="smpl">Connection</a> = "Connection" ":" <a href="#rule.whitespace" class="smpl">OWS</a> <a href="#header.connection" class="smpl">Connection-v</a> 1544 1543 <a href="#header.connection" class="smpl">Connection-v</a> = 1#<a href="#header.connection" class="smpl">connection-token</a> 1545 1544 <a href="#header.connection" class="smpl">connection-token</a> = <a href="#rule.token.separators" class="smpl">token</a> 1546 </pre><p id="rfc.section. 8.1.p.4">HTTP/1.1 proxies <em class="bcp14">MUST</em> parse the Connection header field before a message is forwarded and, for each connection-token in this field, remove any header1545 </pre><p id="rfc.section.7.1.p.4">HTTP/1.1 proxies <em class="bcp14">MUST</em> parse the Connection header field before a message is forwarded and, for each connection-token in this field, remove any header 1547 1546 field(s) from the message with the same name as the connection-token. Connection options are signaled by the presence of a 1548 1547 connection-token in the Connection header field, not by any corresponding additional header field(s), since the additional 1549 1548 header field may not be sent if there are no parameters associated with that connection option. 1550 1549 </p> 1551 <p id="rfc.section. 8.1.p.5">Message headers listed in the Connection header <em class="bcp14">MUST NOT</em> include end-to-end headers, such as Cache-Control.1552 </p> 1553 <p id="rfc.section. 8.1.p.6">HTTP/1.1 defines the "close" connection option for the sender to signal that the connection will be closed after completion1550 <p id="rfc.section.7.1.p.5">Message headers listed in the Connection header <em class="bcp14">MUST NOT</em> include end-to-end headers, such as Cache-Control. 1551 </p> 1552 <p id="rfc.section.7.1.p.6">HTTP/1.1 defines the "close" connection option for the sender to signal that the connection will be closed after completion 1554 1553 of the response. For example, 1555 1554 </p> 1556 1555 <div id="rfc.figure.u.43"></div><pre class="text"> Connection: close 1557 </pre><p id="rfc.section. 8.1.p.8">in either the request or the response header fields indicates that the connection <em class="bcp14">SHOULD NOT</em> be considered `persistent' (<a href="#persistent.connections" title="Persistent Connections">Section 7.1</a>) after the current request/response is complete.1558 </p> 1559 <p id="rfc.section. 8.1.p.9">An HTTP/1.1 client that does not support persistent connections <em class="bcp14">MUST</em> include the "close" connection option in every request message.1560 </p> 1561 <p id="rfc.section. 8.1.p.10">An HTTP/1.1 server that does not support persistent connections <em class="bcp14">MUST</em> include the "close" connection option in every response message that does not have a 1xx (informational) status code.1562 </p> 1563 <p id="rfc.section. 8.1.p.11">A system receiving an HTTP/1.0 (or lower-version) message that includes a Connection header <em class="bcp14">MUST</em>, for each connection-token in this field, remove and ignore any header field(s) from the message with the same name as the1556 </pre><p id="rfc.section.7.1.p.8">in either the request or the response header fields indicates that the connection <em class="bcp14">SHOULD NOT</em> be considered `persistent' (<a href="#persistent.connections" title="Persistent Connections">Section 6.1</a>) after the current request/response is complete. 1557 </p> 1558 <p id="rfc.section.7.1.p.9">An HTTP/1.1 client that does not support persistent connections <em class="bcp14">MUST</em> include the "close" connection option in every request message. 1559 </p> 1560 <p id="rfc.section.7.1.p.10">An HTTP/1.1 server that does not support persistent connections <em class="bcp14">MUST</em> include the "close" connection option in every response message that does not have a 1xx (informational) status code. 1561 </p> 1562 <p id="rfc.section.7.1.p.11">A system receiving an HTTP/1.0 (or lower-version) message that includes a Connection header <em class="bcp14">MUST</em>, for each connection-token in this field, remove and ignore any header field(s) from the message with the same name as the 1564 1563 connection-token. This protects against mistaken forwarding of such header fields by pre-HTTP/1.1 proxies. See <a href="#compatibility.with.http.1.0.persistent.connections" title="Compatibility with HTTP/1.0 Persistent Connections">Appendix B.2</a>. 1565 1564 </p> 1566 1565 <div id="rfc.iref.c.2"></div> 1567 1566 <div id="rfc.iref.h.4"></div> 1568 <h2 id="rfc.section. 8.2"><a href="#rfc.section.8.2">8.2</a> <a id="header.content-length" href="#header.content-length">Content-Length</a></h2>1569 <p id="rfc.section. 8.2.p.1">The entity-header field "Content-Length" indicates the size of the entity-body, in decimal number of OCTETs, sent to the recipient1567 <h2 id="rfc.section.7.2"><a href="#rfc.section.7.2">7.2</a> <a id="header.content-length" href="#header.content-length">Content-Length</a></h2> 1568 <p id="rfc.section.7.2.p.1">The entity-header field "Content-Length" indicates the size of the entity-body, in decimal number of OCTETs, sent to the recipient 1570 1569 or, in the case of the HEAD method, the size of the entity-body that would have been sent had the request been a GET. 1571 1570 </p> 1572 1571 <div id="rfc.figure.u.44"></div><pre class="inline"><span id="rfc.iref.g.75"></span><span id="rfc.iref.g.76"></span> <a href="#header.content-length" class="smpl">Content-Length</a> = "Content-Length" ":" <a href="#rule.whitespace" class="smpl">OWS</a> 1*<a href="#header.content-length" class="smpl">Content-Length-v</a> 1573 1572 <a href="#header.content-length" class="smpl">Content-Length-v</a> = 1*<a href="#core.rules" class="smpl">DIGIT</a> 1574 </pre><p id="rfc.section. 8.2.p.3">An example is</p>1573 </pre><p id="rfc.section.7.2.p.3">An example is</p> 1575 1574 <div id="rfc.figure.u.45"></div><pre class="text"> Content-Length: 3495 1576 </pre><p id="rfc.section. 8.2.p.5">Applications <em class="bcp14">SHOULD</em> use this field to indicate the transfer-length of the message-body, unless this is prohibited by the rules in <a href="#message.length" title="Message Length">Section 4.4</a>.1577 </p> 1578 <p id="rfc.section. 8.2.p.6">Any Content-Length greater than or equal to zero is a valid value. <a href="#message.length" title="Message Length">Section 4.4</a> describes how to determine the length of a message-body if a Content-Length is not given.1579 </p> 1580 <p id="rfc.section. 8.2.p.7">Note that the meaning of this field is significantly different from the corresponding definition in MIME, where it is an optional1575 </pre><p id="rfc.section.7.2.p.5">Applications <em class="bcp14">SHOULD</em> use this field to indicate the transfer-length of the message-body, unless this is prohibited by the rules in <a href="#message.length" title="Message Length">Section 3.4</a>. 1576 </p> 1577 <p id="rfc.section.7.2.p.6">Any Content-Length greater than or equal to zero is a valid value. <a href="#message.length" title="Message Length">Section 3.4</a> describes how to determine the length of a message-body if a Content-Length is not given. 1578 </p> 1579 <p id="rfc.section.7.2.p.7">Note that the meaning of this field is significantly different from the corresponding definition in MIME, where it is an optional 1581 1580 field used within the "message/external-body" content-type. In HTTP, it <em class="bcp14">SHOULD</em> be sent whenever the message's length can be determined prior to being transferred, unless this is prohibited by the rules 1582 in <a href="#message.length" title="Message Length">Section 4.4</a>.1581 in <a href="#message.length" title="Message Length">Section 3.4</a>. 1583 1582 </p> 1584 1583 <div id="rfc.iref.d.1"></div> 1585 1584 <div id="rfc.iref.h.5"></div> 1586 <h2 id="rfc.section. 8.3"><a href="#rfc.section.8.3">8.3</a> <a id="header.date" href="#header.date">Date</a></h2>1587 <p id="rfc.section. 8.3.p.1">The general-header field "Date" represents the date and time at which the message was originated, having the same semantics1588 as orig-date in <a href="http://tools.ietf.org/html/rfc5322#section-3.6.1">Section 3.6.1</a> of <a href="#RFC5322" id="rfc.xref.RFC5322.4"><cite title="Internet Message Format">[RFC5322]</cite></a>. The field value is an HTTP-date, as described in <a href="#full.date" title="Full Date">Section 3.3.1</a>; it <em class="bcp14">MUST</em> be sent in rfc1123-date format.1585 <h2 id="rfc.section.7.3"><a href="#rfc.section.7.3">7.3</a> <a id="header.date" href="#header.date">Date</a></h2> 1586 <p id="rfc.section.7.3.p.1">The general-header field "Date" represents the date and time at which the message was originated, having the same semantics 1587 as orig-date in <a href="http://tools.ietf.org/html/rfc5322#section-3.6.1">Section 3.6.1</a> of <a href="#RFC5322" id="rfc.xref.RFC5322.4"><cite title="Internet Message Format">[RFC5322]</cite></a>. The field value is an HTTP-date, as described in <a href="#full.date" title="Full Date">Section 2.3.1</a>; it <em class="bcp14">MUST</em> be sent in rfc1123-date format. 1589 1588 </p> 1590 1589 <div id="rfc.figure.u.46"></div><pre class="inline"><span id="rfc.iref.g.77"></span><span id="rfc.iref.g.78"></span> <a href="#header.date" class="smpl">Date</a> = "Date" ":" <a href="#rule.whitespace" class="smpl">OWS</a> <a href="#header.date" class="smpl">Date-v</a> 1591 1590 <a href="#header.date" class="smpl">Date-v</a> = <a href="#full.date" class="smpl">HTTP-date</a> 1592 </pre><p id="rfc.section. 8.3.p.3">An example is</p>1591 </pre><p id="rfc.section.7.3.p.3">An example is</p> 1593 1592 <div id="rfc.figure.u.47"></div><pre class="text"> Date: Tue, 15 Nov 1994 08:12:31 GMT 1594 </pre><p id="rfc.section. 8.3.p.5">Origin servers <em class="bcp14">MUST</em> include a Date header field in all responses, except in these cases:1593 </pre><p id="rfc.section.7.3.p.5">Origin servers <em class="bcp14">MUST</em> include a Date header field in all responses, except in these cases: 1595 1594 </p> 1596 1595 <ol> … … 1600 1599 is inconvenient or impossible to generate a valid Date. 1601 1600 </li> 1602 <li>If the server does not have a clock that can provide a reasonable approximation of the current time, its responses <em class="bcp14">MUST NOT</em> include a Date header field. In this case, the rules in <a href="#clockless.origin.server.operation" title="Clockless Origin Server Operation">Section 8.3.1</a> <em class="bcp14">MUST</em> be followed.1601 <li>If the server does not have a clock that can provide a reasonable approximation of the current time, its responses <em class="bcp14">MUST NOT</em> include a Date header field. In this case, the rules in <a href="#clockless.origin.server.operation" title="Clockless Origin Server Operation">Section 7.3.1</a> <em class="bcp14">MUST</em> be followed. 1603 1602 </li> 1604 1603 </ol> 1605 <p id="rfc.section. 8.3.p.6">A received message that does not have a Date header field <em class="bcp14">MUST</em> be assigned one by the recipient if the message will be cached by that recipient or gatewayed via a protocol which requires1604 <p id="rfc.section.7.3.p.6">A received message that does not have a Date header field <em class="bcp14">MUST</em> be assigned one by the recipient if the message will be cached by that recipient or gatewayed via a protocol which requires 1606 1605 a Date. An HTTP implementation without a clock <em class="bcp14">MUST NOT</em> cache responses without revalidating them on every use. An HTTP cache, especially a shared cache, <em class="bcp14">SHOULD</em> use a mechanism, such as NTP <a href="#RFC1305" id="rfc.xref.RFC1305.1"><cite title="Network Time Protocol (Version 3) Specification, Implementation">[RFC1305]</cite></a>, to synchronize its clock with a reliable external standard. 1607 1606 </p> 1608 <p id="rfc.section. 8.3.p.7">Clients <em class="bcp14">SHOULD</em> only send a Date header field in messages that include an entity-body, as in the case of the PUT and POST requests, and even1607 <p id="rfc.section.7.3.p.7">Clients <em class="bcp14">SHOULD</em> only send a Date header field in messages that include an entity-body, as in the case of the PUT and POST requests, and even 1609 1608 then it is optional. A client without a clock <em class="bcp14">MUST NOT</em> send a Date header field in a request. 1610 1609 </p> 1611 <p id="rfc.section. 8.3.p.8">The HTTP-date sent in a Date header <em class="bcp14">SHOULD NOT</em> represent a date and time subsequent to the generation of the message. It <em class="bcp14">SHOULD</em> represent the best available approximation of the date and time of message generation, unless the implementation has no means1610 <p id="rfc.section.7.3.p.8">The HTTP-date sent in a Date header <em class="bcp14">SHOULD NOT</em> represent a date and time subsequent to the generation of the message. It <em class="bcp14">SHOULD</em> represent the best available approximation of the date and time of message generation, unless the implementation has no means 1612 1611 of generating a reasonably accurate date and time. In theory, the date ought to represent the moment just before the entity 1613 1612 is generated. In practice, the date can be generated at any time during the message origination without affecting its semantic 1614 1613 value. 1615 1614 </p> 1616 <h3 id="rfc.section. 8.3.1"><a href="#rfc.section.8.3.1">8.3.1</a> <a id="clockless.origin.server.operation" href="#clockless.origin.server.operation">Clockless Origin Server Operation</a></h3>1617 <p id="rfc.section. 8.3.1.p.1">Some origin server implementations might not have a clock available. An origin server without a clock <em class="bcp14">MUST NOT</em> assign Expires or Last-Modified values to a response, unless these values were associated with the resource by a system or1615 <h3 id="rfc.section.7.3.1"><a href="#rfc.section.7.3.1">7.3.1</a> <a id="clockless.origin.server.operation" href="#clockless.origin.server.operation">Clockless Origin Server Operation</a></h3> 1616 <p id="rfc.section.7.3.1.p.1">Some origin server implementations might not have a clock available. An origin server without a clock <em class="bcp14">MUST NOT</em> assign Expires or Last-Modified values to a response, unless these values were associated with the resource by a system or 1618 1617 user with a reliable clock. It <em class="bcp14">MAY</em> assign an Expires value that is known, at or before server configuration time, to be in the past (this allows "pre-expiration" 1619 1618 of responses without storing separate Expires values for each resource). … … 1621 1620 <div id="rfc.iref.h.6"></div> 1622 1621 <div id="rfc.iref.h.7"></div> 1623 <h2 id="rfc.section. 8.4"><a href="#rfc.section.8.4">8.4</a> <a id="header.host" href="#header.host">Host</a></h2>1624 <p id="rfc.section. 8.4.p.1">The request-header field "Host" specifies the Internet host and port number of the resource being requested, as obtained from1625 the original URI given by the user or referring resource (generally an HTTP URL, as described in <a href="#http.uri" title="http URI scheme">Section 3.2.1</a>). The Host field value <em class="bcp14">MUST</em> represent the naming authority of the origin server or gateway given by the original URL. This allows the origin server or1622 <h2 id="rfc.section.7.4"><a href="#rfc.section.7.4">7.4</a> <a id="header.host" href="#header.host">Host</a></h2> 1623 <p id="rfc.section.7.4.p.1">The request-header field "Host" specifies the Internet host and port number of the resource being requested, as obtained from 1624 the original URI given by the user or referring resource (generally an HTTP URL, as described in <a href="#http.uri" title="http URI scheme">Section 2.2.1</a>). The Host field value <em class="bcp14">MUST</em> represent the naming authority of the origin server or gateway given by the original URL. This allows the origin server or 1626 1625 gateway to differentiate between internally-ambiguous URLs, such as the root "/" URL of a server for multiple host names on 1627 1626 a single IP address. 1628 1627 </p> 1629 1628 <div id="rfc.figure.u.48"></div><pre class="inline"><span id="rfc.iref.g.79"></span><span id="rfc.iref.g.80"></span> <a href="#header.host" class="smpl">Host</a> = "Host" ":" <a href="#rule.whitespace" class="smpl">OWS</a> <a href="#header.host" class="smpl">Host-v</a> 1630 <a href="#header.host" class="smpl">Host-v</a> = <a href="#uri" class="smpl">uri-host</a> [ ":" <a href="#uri" class="smpl">port</a> ] ; <a href="#http.uri" title="http URI scheme">Section 3.2.1</a>1631 </pre><p id="rfc.section. 8.4.p.3">A "host" without any trailing port information implies the default port for the service requested (e.g., "80" for an HTTP1629 <a href="#header.host" class="smpl">Host-v</a> = <a href="#uri" class="smpl">uri-host</a> [ ":" <a href="#uri" class="smpl">port</a> ] ; <a href="#http.uri" title="http URI scheme">Section 2.2.1</a> 1630 </pre><p id="rfc.section.7.4.p.3">A "host" without any trailing port information implies the default port for the service requested (e.g., "80" for an HTTP 1632 1631 URL). For example, a request on the origin server for <http://www.example.org/pub/WWW/> would properly include: 1633 1632 </p> 1634 1633 <div id="rfc.figure.u.49"></div><pre class="text"> GET /pub/WWW/ HTTP/1.1 1635 1634 Host: www.example.org 1636 </pre><p id="rfc.section. 8.4.p.5">A client <em class="bcp14">MUST</em> include a Host header field in all HTTP/1.1 request messages. If the requested URI does not include an Internet host name1635 </pre><p id="rfc.section.7.4.p.5">A client <em class="bcp14">MUST</em> include a Host header field in all HTTP/1.1 request messages. If the requested URI does not include an Internet host name 1637 1636 for the service being requested, then the Host header field <em class="bcp14">MUST</em> be given with an empty value. An HTTP/1.1 proxy <em class="bcp14">MUST</em> ensure that any request message it forwards does contain an appropriate Host header field that identifies the service being 1638 1637 requested by the proxy. All Internet-based HTTP/1.1 servers <em class="bcp14">MUST</em> respond with a 400 (Bad Request) status code to any HTTP/1.1 request message which lacks a Host header field. 1639 1638 </p> 1640 <p id="rfc.section. 8.4.p.6">See Sections <a href="#the.resource.identified.by.a.request" title="The Resource Identified by a Request">5.2</a> and <a href="#changes.to.simplify.multi-homed.web.servers.and.conserve.ip.addresses" title="Changes to Simplify Multi-homed Web Servers and Conserve IP Addresses">B.1.1</a> for other requirements relating to Host.1639 <p id="rfc.section.7.4.p.6">See Sections <a href="#the.resource.identified.by.a.request" title="The Resource Identified by a Request">4.2</a> and <a href="#changes.to.simplify.multi-homed.web.servers.and.conserve.ip.addresses" title="Changes to Simplify Multi-homed Web Servers and Conserve IP Addresses">B.1.1</a> for other requirements relating to Host. 1641 1640 </p> 1642 1641 <div id="rfc.iref.t.1"></div> 1643 1642 <div id="rfc.iref.h.8"></div> 1644 <h2 id="rfc.section. 8.5"><a href="#rfc.section.8.5">8.5</a> <a id="header.te" href="#header.te">TE</a></h2>1645 <p id="rfc.section. 8.5.p.1">The request-header field "TE" indicates what extension transfer-codings it is willing to accept in the response and whether1643 <h2 id="rfc.section.7.5"><a href="#rfc.section.7.5">7.5</a> <a id="header.te" href="#header.te">TE</a></h2> 1644 <p id="rfc.section.7.5.p.1">The request-header field "TE" indicates what extension transfer-codings it is willing to accept in the response and whether 1646 1645 or not it is willing to accept trailer fields in a chunked transfer-coding. Its value may consist of the keyword "trailers" 1647 and/or a comma-separated list of extension transfer-coding names with optional accept parameters (as described in <a href="#transfer.codings" title="Transfer Codings">Section 3.4</a>).1646 and/or a comma-separated list of extension transfer-coding names with optional accept parameters (as described in <a href="#transfer.codings" title="Transfer Codings">Section 2.4</a>). 1648 1647 </p> 1649 1648 <div id="rfc.figure.u.50"></div><pre class="inline"><span id="rfc.iref.g.81"></span><span id="rfc.iref.g.82"></span><span id="rfc.iref.g.83"></span> <a href="#header.te" class="smpl">TE</a> = "TE" ":" <a href="#rule.whitespace" class="smpl">OWS</a> <a href="#header.te" class="smpl">TE-v</a> 1650 1649 <a href="#header.te" class="smpl">TE-v</a> = #<a href="#header.te" class="smpl">t-codings</a> 1651 1650 <a href="#header.te" class="smpl">t-codings</a> = "trailers" / ( <a href="#transfer.codings" class="smpl">transfer-extension</a> [ <a href="#abnf.dependencies" class="smpl">accept-params</a> ] ) 1652 </pre><p id="rfc.section. 8.5.p.3">The presence of the keyword "trailers" indicates that the client is willing to accept trailer fields in a chunked transfer-coding,1653 as defined in <a href="#chunked.transfer.encoding" title="Chunked Transfer Coding">Section 3.4.1</a>. This keyword is reserved for use with transfer-coding values even though it does not itself represent a transfer-coding.1654 </p> 1655 <p id="rfc.section. 8.5.p.4">Examples of its use are:</p>1651 </pre><p id="rfc.section.7.5.p.3">The presence of the keyword "trailers" indicates that the client is willing to accept trailer fields in a chunked transfer-coding, 1652 as defined in <a href="#chunked.transfer.encoding" title="Chunked Transfer Coding">Section 2.4.1</a>. This keyword is reserved for use with transfer-coding values even though it does not itself represent a transfer-coding. 1653 </p> 1654 <p id="rfc.section.7.5.p.4">Examples of its use are:</p> 1656 1655 <div id="rfc.figure.u.51"></div><pre class="text"> TE: deflate 1657 1656 TE: 1658 1657 TE: trailers, deflate;q=0.5 1659 </pre><p id="rfc.section. 8.5.p.6">The TE header field only applies to the immediate connection. Therefore, the keyword <em class="bcp14">MUST</em> be supplied within a Connection header field (<a href="#header.connection" id="rfc.xref.header.connection.4" title="Connection">Section 8.1</a>) whenever TE is present in an HTTP/1.1 message.1660 </p> 1661 <p id="rfc.section. 8.5.p.7">A server tests whether a transfer-coding is acceptable, according to a TE field, using these rules: </p>1658 </pre><p id="rfc.section.7.5.p.6">The TE header field only applies to the immediate connection. Therefore, the keyword <em class="bcp14">MUST</em> be supplied within a Connection header field (<a href="#header.connection" id="rfc.xref.header.connection.4" title="Connection">Section 7.1</a>) whenever TE is present in an HTTP/1.1 message. 1659 </p> 1660 <p id="rfc.section.7.5.p.7">A server tests whether a transfer-coding is acceptable, according to a TE field, using these rules: </p> 1662 1661 <ol> 1663 1662 <li> … … 1682 1681 </li> 1683 1682 </ol> 1684 <p id="rfc.section. 8.5.p.8">If the TE field-value is empty or if no TE field is present, the only transfer-coding is "chunked". A message with no transfer-coding1683 <p id="rfc.section.7.5.p.8">If the TE field-value is empty or if no TE field is present, the only transfer-coding is "chunked". A message with no transfer-coding 1685 1684 is always acceptable. 1686 1685 </p> 1687 1686 <div id="rfc.iref.t.2"></div> 1688 1687 <div id="rfc.iref.h.9"></div> 1689 <h2 id="rfc.section. 8.6"><a href="#rfc.section.8.6">8.6</a> <a id="header.trailer" href="#header.trailer">Trailer</a></h2>1690 <p id="rfc.section. 8.6.p.1">The general field "Trailer" indicates that the given set of header fields is present in the trailer of a message encoded with1688 <h2 id="rfc.section.7.6"><a href="#rfc.section.7.6">7.6</a> <a id="header.trailer" href="#header.trailer">Trailer</a></h2> 1689 <p id="rfc.section.7.6.p.1">The general field "Trailer" indicates that the given set of header fields is present in the trailer of a message encoded with 1691 1690 chunked transfer-coding. 1692 1691 </p> 1693 1692 <div id="rfc.figure.u.52"></div><pre class="inline"><span id="rfc.iref.g.84"></span><span id="rfc.iref.g.85"></span> <a href="#header.trailer" class="smpl">Trailer</a> = "Trailer" ":" <a href="#rule.whitespace" class="smpl">OWS</a> <a href="#header.trailer" class="smpl">Trailer-v</a> 1694 1693 <a href="#header.trailer" class="smpl">Trailer-v</a> = 1#<a href="#message.headers" class="smpl">field-name</a> 1695 </pre><p id="rfc.section. 8.6.p.3">An HTTP/1.1 message <em class="bcp14">SHOULD</em> include a Trailer header field in a message using chunked transfer-coding with a non-empty trailer. Doing so allows the recipient1694 </pre><p id="rfc.section.7.6.p.3">An HTTP/1.1 message <em class="bcp14">SHOULD</em> include a Trailer header field in a message using chunked transfer-coding with a non-empty trailer. Doing so allows the recipient 1696 1695 to know which header fields to expect in the trailer. 1697 1696 </p> 1698 <p id="rfc.section. 8.6.p.4">If no Trailer header field is present, the trailer <em class="bcp14">SHOULD NOT</em> include any header fields. See <a href="#chunked.transfer.encoding" title="Chunked Transfer Coding">Section 3.4.1</a> for restrictions on the use of trailer fields in a "chunked" transfer-coding.1699 </p> 1700 <p id="rfc.section. 8.6.p.5">Message header fields listed in the Trailer header field <em class="bcp14">MUST NOT</em> include the following header fields:1697 <p id="rfc.section.7.6.p.4">If no Trailer header field is present, the trailer <em class="bcp14">SHOULD NOT</em> include any header fields. See <a href="#chunked.transfer.encoding" title="Chunked Transfer Coding">Section 2.4.1</a> for restrictions on the use of trailer fields in a "chunked" transfer-coding. 1698 </p> 1699 <p id="rfc.section.7.6.p.5">Message header fields listed in the Trailer header field <em class="bcp14">MUST NOT</em> include the following header fields: 1701 1700 </p> 1702 1701 <ul> … … 1707 1706 <div id="rfc.iref.t.3"></div> 1708 1707 <div id="rfc.iref.h.10"></div> 1709 <h2 id="rfc.section. 8.7"><a href="#rfc.section.8.7">8.7</a> <a id="header.transfer-encoding" href="#header.transfer-encoding">Transfer-Encoding</a></h2>1710 <p id="rfc.section. 8.7.p.1">The general-header "Transfer-Encoding" field indicates what (if any) type of transformation has been applied to the message1708 <h2 id="rfc.section.7.7"><a href="#rfc.section.7.7">7.7</a> <a id="header.transfer-encoding" href="#header.transfer-encoding">Transfer-Encoding</a></h2> 1709 <p id="rfc.section.7.7.p.1">The general-header "Transfer-Encoding" field indicates what (if any) type of transformation has been applied to the message 1711 1710 body in order to safely transfer it between the sender and the recipient. This differs from the content-coding in that the 1712 1711 transfer-coding is a property of the message, not of the entity. … … 1715 1714 <a href="#header.transfer-encoding" class="smpl">Transfer-Encoding-v</a> 1716 1715 <a href="#header.transfer-encoding" class="smpl">Transfer-Encoding-v</a> = 1#<a href="#transfer.codings" class="smpl">transfer-coding</a> 1717 </pre><p id="rfc.section. 8.7.p.3">Transfer-codings are defined in <a href="#transfer.codings" title="Transfer Codings">Section 3.4</a>. An example is:1716 </pre><p id="rfc.section.7.7.p.3">Transfer-codings are defined in <a href="#transfer.codings" title="Transfer Codings">Section 2.4</a>. An example is: 1718 1717 </p> 1719 1718 <div id="rfc.figure.u.54"></div><pre class="text"> Transfer-Encoding: chunked 1720 </pre><p id="rfc.section. 8.7.p.5">If multiple encodings have been applied to an entity, the transfer-codings <em class="bcp14">MUST</em> be listed in the order in which they were applied. Additional information about the encoding parameters <em class="bcp14">MAY</em> be provided by other entity-header fields not defined by this specification.1721 </p> 1722 <p id="rfc.section. 8.7.p.6">Many older HTTP/1.0 applications do not understand the Transfer-Encoding header.</p>1719 </pre><p id="rfc.section.7.7.p.5">If multiple encodings have been applied to an entity, the transfer-codings <em class="bcp14">MUST</em> be listed in the order in which they were applied. Additional information about the encoding parameters <em class="bcp14">MAY</em> be provided by other entity-header fields not defined by this specification. 1720 </p> 1721 <p id="rfc.section.7.7.p.6">Many older HTTP/1.0 applications do not understand the Transfer-Encoding header.</p> 1723 1722 <div id="rfc.iref.u.3"></div> 1724 1723 <div id="rfc.iref.h.11"></div> 1725 <h2 id="rfc.section. 8.8"><a href="#rfc.section.8.8">8.8</a> <a id="header.upgrade" href="#header.upgrade">Upgrade</a></h2>1726 <p id="rfc.section. 8.8.p.1">The general-header "Upgrade" allows the client to specify what additional communication protocols it supports and would like1724 <h2 id="rfc.section.7.8"><a href="#rfc.section.7.8">7.8</a> <a id="header.upgrade" href="#header.upgrade">Upgrade</a></h2> 1725 <p id="rfc.section.7.8.p.1">The general-header "Upgrade" allows the client to specify what additional communication protocols it supports and would like 1727 1726 to use if the server finds it appropriate to switch protocols. The server <em class="bcp14">MUST</em> use the Upgrade header field within a 101 (Switching Protocols) response to indicate which protocol(s) are being switched. 1728 1727 </p> 1729 1728 <div id="rfc.figure.u.55"></div><pre class="inline"><span id="rfc.iref.g.88"></span><span id="rfc.iref.g.89"></span> <a href="#header.upgrade" class="smpl">Upgrade</a> = "Upgrade" ":" <a href="#rule.whitespace" class="smpl">OWS</a> <a href="#header.upgrade" class="smpl">Upgrade-v</a> 1730 1729 <a href="#header.upgrade" class="smpl">Upgrade-v</a> = 1#<a href="#product.tokens" class="smpl">product</a> 1731 </pre><p id="rfc.section. 8.8.p.3">For example,</p>1730 </pre><p id="rfc.section.7.8.p.3">For example,</p> 1732 1731 <div id="rfc.figure.u.56"></div><pre class="text"> Upgrade: HTTP/2.0, SHTTP/1.3, IRC/6.9, RTA/x11 1733 </pre><p id="rfc.section. 8.8.p.5">The Upgrade header field is intended to provide a simple mechanism for transition from HTTP/1.1 to some other, incompatible1732 </pre><p id="rfc.section.7.8.p.5">The Upgrade header field is intended to provide a simple mechanism for transition from HTTP/1.1 to some other, incompatible 1734 1733 protocol. It does so by allowing the client to advertise its desire to use another protocol, such as a later version of HTTP 1735 1734 with a higher major version number, even though the current request has been made using HTTP/1.1. This eases the difficult … … 1738 1737 the server, possibly according to the nature of the method and/or resource being requested). 1739 1738 </p> 1740 <p id="rfc.section. 8.8.p.6">The Upgrade header field only applies to switching application-layer protocols upon the existing transport-layer connection.1739 <p id="rfc.section.7.8.p.6">The Upgrade header field only applies to switching application-layer protocols upon the existing transport-layer connection. 1741 1740 Upgrade cannot be used to insist on a protocol change; its acceptance and use by the server is optional. The capabilities 1742 1741 and nature of the application-layer communication after the protocol change is entirely dependent upon the new protocol chosen, 1743 1742 although the first action after changing the protocol <em class="bcp14">MUST</em> be a response to the initial HTTP request containing the Upgrade header field. 1744 1743 </p> 1745 <p id="rfc.section. 8.8.p.7">The Upgrade header field only applies to the immediate connection. Therefore, the upgrade keyword <em class="bcp14">MUST</em> be supplied within a Connection header field (<a href="#header.connection" id="rfc.xref.header.connection.5" title="Connection">Section 8.1</a>) whenever Upgrade is present in an HTTP/1.1 message.1746 </p> 1747 <p id="rfc.section. 8.8.p.8">The Upgrade header field cannot be used to indicate a switch to a protocol on a different connection. For that purpose, it1744 <p id="rfc.section.7.8.p.7">The Upgrade header field only applies to the immediate connection. Therefore, the upgrade keyword <em class="bcp14">MUST</em> be supplied within a Connection header field (<a href="#header.connection" id="rfc.xref.header.connection.5" title="Connection">Section 7.1</a>) whenever Upgrade is present in an HTTP/1.1 message. 1745 </p> 1746 <p id="rfc.section.7.8.p.8">The Upgrade header field cannot be used to indicate a switch to a protocol on a different connection. For that purpose, it 1748 1747 is more appropriate to use a 301, 302, 303, or 305 redirection response. 1749 1748 </p> 1750 <p id="rfc.section. 8.8.p.9">This specification only defines the protocol name "HTTP" for use by the family of Hypertext Transfer Protocols, as defined1751 by the HTTP version rules of <a href="#http.version" title="HTTP Version">Section 3.1</a> and future updates to this specification. Any token can be used as a protocol name; however, it will only be useful if both1749 <p id="rfc.section.7.8.p.9">This specification only defines the protocol name "HTTP" for use by the family of Hypertext Transfer Protocols, as defined 1750 by the HTTP version rules of <a href="#http.version" title="HTTP Version">Section 2.1</a> and future updates to this specification. Any token can be used as a protocol name; however, it will only be useful if both 1752 1751 the client and server associate the name with the same protocol. 1753 1752 </p> 1754 1753 <div id="rfc.iref.v.1"></div> 1755 1754 <div id="rfc.iref.h.12"></div> 1756 <h2 id="rfc.section. 8.9"><a href="#rfc.section.8.9">8.9</a> <a id="header.via" href="#header.via">Via</a></h2>1757 <p id="rfc.section. 8.9.p.1">The general-header field "Via" <em class="bcp14">MUST</em> be used by gateways and proxies to indicate the intermediate protocols and recipients between the user agent and the server1755 <h2 id="rfc.section.7.9"><a href="#rfc.section.7.9">7.9</a> <a id="header.via" href="#header.via">Via</a></h2> 1756 <p id="rfc.section.7.9.p.1">The general-header field "Via" <em class="bcp14">MUST</em> be used by gateways and proxies to indicate the intermediate protocols and recipients between the user agent and the server 1758 1757 on requests, and between the origin server and the client on responses. It is analogous to the "Received" field defined in <a href="http://tools.ietf.org/html/rfc5322#section-3.6.7">Section 3.6.7</a> of <a href="#RFC5322" id="rfc.xref.RFC5322.5"><cite title="Internet Message Format">[RFC5322]</cite></a> and is intended to be used for tracking message forwards, avoiding request loops, and identifying the protocol capabilities 1759 1758 of all senders along the request/response chain. … … 1767 1766 <a href="#header.via" class="smpl">received-by</a> = ( <a href="#uri" class="smpl">uri-host</a> [ ":" <a href="#uri" class="smpl">port</a> ] ) / <a href="#header.via" class="smpl">pseudonym</a> 1768 1767 <a href="#header.via" class="smpl">pseudonym</a> = <a href="#rule.token.separators" class="smpl">token</a> 1769 </pre><p id="rfc.section. 8.9.p.3">The received-protocol indicates the protocol version of the message received by the server or client along each segment of1768 </pre><p id="rfc.section.7.9.p.3">The received-protocol indicates the protocol version of the message received by the server or client along each segment of 1770 1769 the request/response chain. The received-protocol version is appended to the Via field value when the message is forwarded 1771 1770 so that information about the protocol capabilities of upstream applications remains visible to all recipients. 1772 1771 </p> 1773 <p id="rfc.section. 8.9.p.4">The protocol-name is optional if and only if it would be "HTTP". The received-by field is normally the host and optional port1772 <p id="rfc.section.7.9.p.4">The protocol-name is optional if and only if it would be "HTTP". The received-by field is normally the host and optional port 1774 1773 number of a recipient server or client that subsequently forwarded the message. However, if the real host is considered to 1775 1774 be sensitive information, it <em class="bcp14">MAY</em> be replaced by a pseudonym. If the port is not given, it <em class="bcp14">MAY</em> be assumed to be the default port of the received-protocol. 1776 1775 </p> 1777 <p id="rfc.section. 8.9.p.5">Multiple Via field values represents each proxy or gateway that has forwarded the message. Each recipient <em class="bcp14">MUST</em> append its information such that the end result is ordered according to the sequence of forwarding applications.1778 </p> 1779 <p id="rfc.section. 8.9.p.6">Comments <em class="bcp14">MAY</em> be used in the Via header field to identify the software of the recipient proxy or gateway, analogous to the User-Agent and1776 <p id="rfc.section.7.9.p.5">Multiple Via field values represents each proxy or gateway that has forwarded the message. Each recipient <em class="bcp14">MUST</em> append its information such that the end result is ordered according to the sequence of forwarding applications. 1777 </p> 1778 <p id="rfc.section.7.9.p.6">Comments <em class="bcp14">MAY</em> be used in the Via header field to identify the software of the recipient proxy or gateway, analogous to the User-Agent and 1780 1779 Server header fields. However, all comments in the Via field are optional and <em class="bcp14">MAY</em> be removed by any recipient prior to forwarding the message. 1781 1780 </p> 1782 <p id="rfc.section. 8.9.p.7">For example, a request message could be sent from an HTTP/1.0 user agent to an internal proxy code-named "fred", which uses1781 <p id="rfc.section.7.9.p.7">For example, a request message could be sent from an HTTP/1.0 user agent to an internal proxy code-named "fred", which uses 1783 1782 HTTP/1.1 to forward the request to a public proxy at p.example.net, which completes the request by forwarding it to the origin 1784 1783 server at www.example.com. The request received by www.example.com would then have the following Via header field: 1785 1784 </p> 1786 1785 <div id="rfc.figure.u.58"></div><pre class="text"> Via: 1.0 fred, 1.1 p.example.net (Apache/1.1) 1787 </pre><p id="rfc.section. 8.9.p.9">Proxies and gateways used as a portal through a network firewall <em class="bcp14">SHOULD NOT</em>, by default, forward the names and ports of hosts within the firewall region. This information <em class="bcp14">SHOULD</em> only be propagated if explicitly enabled. If not enabled, the received-by host of any host behind the firewall <em class="bcp14">SHOULD</em> be replaced by an appropriate pseudonym for that host.1788 </p> 1789 <p id="rfc.section. 8.9.p.10">For organizations that have strong privacy requirements for hiding internal structures, a proxy <em class="bcp14">MAY</em> combine an ordered subsequence of Via header field entries with identical received-protocol values into a single such entry.1786 </pre><p id="rfc.section.7.9.p.9">Proxies and gateways used as a portal through a network firewall <em class="bcp14">SHOULD NOT</em>, by default, forward the names and ports of hosts within the firewall region. This information <em class="bcp14">SHOULD</em> only be propagated if explicitly enabled. If not enabled, the received-by host of any host behind the firewall <em class="bcp14">SHOULD</em> be replaced by an appropriate pseudonym for that host. 1787 </p> 1788 <p id="rfc.section.7.9.p.10">For organizations that have strong privacy requirements for hiding internal structures, a proxy <em class="bcp14">MAY</em> combine an ordered subsequence of Via header field entries with identical received-protocol values into a single such entry. 1790 1789 For example, 1791 1790 </p> 1792 1791 <div id="rfc.figure.u.59"></div><pre class="text"> Via: 1.0 ricky, 1.1 ethel, 1.1 fred, 1.0 lucy 1793 </pre><p id="rfc.section. 8.9.p.12">could be collapsed to</p>1792 </pre><p id="rfc.section.7.9.p.12">could be collapsed to</p> 1794 1793 <div id="rfc.figure.u.60"></div><pre class="text"> Via: 1.0 ricky, 1.1 mertz, 1.0 lucy 1795 </pre><p id="rfc.section. 8.9.p.14">Applications <em class="bcp14">SHOULD NOT</em> combine multiple entries unless they are all under the same organizational control and the hosts have already been replaced1794 </pre><p id="rfc.section.7.9.p.14">Applications <em class="bcp14">SHOULD NOT</em> combine multiple entries unless they are all under the same organizational control and the hosts have already been replaced 1796 1795 by pseudonyms. Applications <em class="bcp14">MUST NOT</em> combine entries which have different received-protocol values. 1797 1796 </p> 1798 <h1 id="rfc.section. 9"><a href="#rfc.section.9">9.</a> <a id="IANA.considerations" href="#IANA.considerations">IANA Considerations</a></h1>1799 <h2 id="rfc.section. 9.1"><a href="#rfc.section.9.1">9.1</a> <a id="message.header.registration" href="#message.header.registration">Message Header Registration</a></h2>1800 <p id="rfc.section. 9.1.p.1">The Message Header Registry located at <<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>> should be updated with the permanent registrations below (see <a href="#RFC3864" id="rfc.xref.RFC3864.1"><cite title="Registration Procedures for Message Header Fields">[RFC3864]</cite></a>):1797 <h1 id="rfc.section.8"><a href="#rfc.section.8">8.</a> <a id="IANA.considerations" href="#IANA.considerations">IANA Considerations</a></h1> 1798 <h2 id="rfc.section.8.1"><a href="#rfc.section.8.1">8.1</a> <a id="message.header.registration" href="#message.header.registration">Message Header Registration</a></h2> 1799 <p id="rfc.section.8.1.p.1">The Message Header Registry located at <<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>> should be updated with the permanent registrations below (see <a href="#RFC3864" id="rfc.xref.RFC3864.1"><cite title="Registration Procedures for Message Header Fields">[RFC3864]</cite></a>): 1801 1800 </p> 1802 1801 <div id="rfc.table.1"> … … 1816 1815 <td>http</td> 1817 1816 <td>standard</td> 1818 <td> <a href="#header.connection" id="rfc.xref.header.connection.6" title="Connection">Section 8.1</a>1817 <td> <a href="#header.connection" id="rfc.xref.header.connection.6" title="Connection">Section 7.1</a> 1819 1818 </td> 1820 1819 </tr> … … 1823 1822 <td>http</td> 1824 1823 <td>standard</td> 1825 <td> <a href="#header.content-length" id="rfc.xref.header.content-length.2" title="Content-Length">Section 8.2</a>1824 <td> <a href="#header.content-length" id="rfc.xref.header.content-length.2" title="Content-Length">Section 7.2</a> 1826 1825 </td> 1827 1826 </tr> … … 1830 1829 <td>http</td> 1831 1830 <td>standard</td> 1832 <td> <a href="#header.date" id="rfc.xref.header.date.2" title="Date">Section 8.3</a>1831 <td> <a href="#header.date" id="rfc.xref.header.date.2" title="Date">Section 7.3</a> 1833 1832 </td> 1834 1833 </tr> … … 1837 1836 <td>http</td> 1838 1837 <td>standard</td> 1839 <td> <a href="#header.host" id="rfc.xref.header.host.1" title="Host">Section 8.4</a>1838 <td> <a href="#header.host" id="rfc.xref.header.host.1" title="Host">Section 7.4</a> 1840 1839 </td> 1841 1840 </tr> … … 1844 1843 <td>http</td> 1845 1844 <td>standard</td> 1846 <td> <a href="#header.te" id="rfc.xref.header.te.3" title="TE">Section 8.5</a>1845 <td> <a href="#header.te" id="rfc.xref.header.te.3" title="TE">Section 7.5</a> 1847 1846 </td> 1848 1847 </tr> … … 1851 1850 <td>http</td> 1852 1851 <td>standard</td> 1853 <td> <a href="#header.trailer" id="rfc.xref.header.trailer.3" title="Trailer">Section 8.6</a>1852 <td> <a href="#header.trailer" id="rfc.xref.header.trailer.3" title="Trailer">Section 7.6</a> 1854 1853 </td> 1855 1854 </tr> … … 1858 1857 <td>http</td> 1859 1858 <td>standard</td> 1860 <td> <a href="#header.transfer-encoding" id="rfc.xref.header.transfer-encoding.5" title="Transfer-Encoding">Section 8.7</a>1859 <td> <a href="#header.transfer-encoding" id="rfc.xref.header.transfer-encoding.5" title="Transfer-Encoding">Section 7.7</a> 1861 1860 </td> 1862 1861 </tr> … … 1865 1864 <td>http</td> 1866 1865 <td>standard</td> 1867 <td> <a href="#header.upgrade" id="rfc.xref.header.upgrade.2" title="Upgrade">Section 8.8</a>1866 <td> <a href="#header.upgrade" id="rfc.xref.header.upgrade.2" title="Upgrade">Section 7.8</a> 1868 1867 </td> 1869 1868 </tr> … … 1872 1871 <td>http</td> 1873 1872 <td>standard</td> 1874 <td> <a href="#header.via" id="rfc.xref.header.via.2" title="Via">Section 8.9</a>1873 <td> <a href="#header.via" id="rfc.xref.header.via.2" title="Via">Section 7.9</a> 1875 1874 </td> 1876 1875 </tr> … … 1878 1877 </table> 1879 1878 </div> 1880 <p id="rfc.section. 9.1.p.2">The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".</p>1881 <h2 id="rfc.section. 9.2"><a href="#rfc.section.9.2">9.2</a> <a id="uri.scheme.registration" href="#uri.scheme.registration">URI Scheme Registration</a></h2>1882 <p id="rfc.section. 9.2.p.1">The entry for the "http" URI Scheme in the registry located at <<a href="http://www.iana.org/assignments/uri-schemes.html">http://www.iana.org/assignments/uri-schemes.html</a>> should be updated to point to <a href="#http.uri" title="http URI scheme">Section 3.2.1</a> of this document (see <a href="#RFC4395" id="rfc.xref.RFC4395.1"><cite title="Guidelines and Registration Procedures for New URI Schemes">[RFC4395]</cite></a>).1883 </p> 1884 <h2 id="rfc.section. 9.3"><a href="#rfc.section.9.3">9.3</a> <a id="internet.media.type.http" href="#internet.media.type.http">Internet Media Type Registrations</a></h2>1885 <p id="rfc.section. 9.3.p.1">This document serves as the specification for the Internet media types "message/http" and "application/http". The following1879 <p id="rfc.section.8.1.p.2">The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".</p> 1880 <h2 id="rfc.section.8.2"><a href="#rfc.section.8.2">8.2</a> <a id="uri.scheme.registration" href="#uri.scheme.registration">URI Scheme Registration</a></h2> 1881 <p id="rfc.section.8.2.p.1">The entry for the "http" URI Scheme in the registry located at <<a href="http://www.iana.org/assignments/uri-schemes.html">http://www.iana.org/assignments/uri-schemes.html</a>> should be updated to point to <a href="#http.uri" title="http URI scheme">Section 2.2.1</a> of this document (see <a href="#RFC4395" id="rfc.xref.RFC4395.1"><cite title="Guidelines and Registration Procedures for New URI Schemes">[RFC4395]</cite></a>). 1882 </p> 1883 <h2 id="rfc.section.8.3"><a href="#rfc.section.8.3">8.3</a> <a id="internet.media.type.http" href="#internet.media.type.http">Internet Media Type Registrations</a></h2> 1884 <p id="rfc.section.8.3.p.1">This document serves as the specification for the Internet media types "message/http" and "application/http". The following 1886 1885 is to be registered with IANA (see <a href="#RFC4288" id="rfc.xref.RFC4288.1"><cite title="Media Type Specifications and Registration Procedures">[RFC4288]</cite></a>). 1887 1886 </p> 1888 1887 <div id="rfc.iref.m.1"></div> 1889 1888 <div id="rfc.iref.m.2"></div> 1890 <h3 id="rfc.section. 9.3.1"><a href="#rfc.section.9.3.1">9.3.1</a> <a id="internet.media.type.message.http" href="#internet.media.type.message.http">Internet Media Type message/http</a></h3>1891 <p id="rfc.section. 9.3.1.p.1">The message/http type can be used to enclose a single HTTP request or response message, provided that it obeys the MIME restrictions1889 <h3 id="rfc.section.8.3.1"><a href="#rfc.section.8.3.1">8.3.1</a> <a id="internet.media.type.message.http" href="#internet.media.type.message.http">Internet Media Type message/http</a></h3> 1890 <p id="rfc.section.8.3.1.p.1">The message/http type can be used to enclose a single HTTP request or response message, provided that it obeys the MIME restrictions 1892 1891 for all "message" types regarding line length and encodings. 1893 1892 </p> 1894 <p id="rfc.section. 9.3.1.p.2"> </p>1893 <p id="rfc.section.8.3.1.p.2"> </p> 1895 1894 <dl> 1896 1895 <dt>Type name:</dt> … … 1918 1917 <dd>none</dd> 1919 1918 <dt>Published specification:</dt> 1920 <dd>This specification (see <a href="#internet.media.type.message.http" title="Internet Media Type message/http">Section 9.3.1</a>).1919 <dd>This specification (see <a href="#internet.media.type.message.http" title="Internet Media Type message/http">Section 8.3.1</a>). 1921 1920 </dd> 1922 1921 <dt>Applications that use this media type:</dt> … … 1943 1942 <div id="rfc.iref.m.3"></div> 1944 1943 <div id="rfc.iref.a.1"></div> 1945 <h3 id="rfc.section. 9.3.2"><a href="#rfc.section.9.3.2">9.3.2</a> <a id="internet.media.type.application.http" href="#internet.media.type.application.http">Internet Media Type application/http</a></h3>1946 <p id="rfc.section. 9.3.2.p.1">The application/http type can be used to enclose a pipeline of one or more HTTP request or response messages (not intermixed).</p>1947 <p id="rfc.section. 9.3.2.p.2"> </p>1944 <h3 id="rfc.section.8.3.2"><a href="#rfc.section.8.3.2">8.3.2</a> <a id="internet.media.type.application.http" href="#internet.media.type.application.http">Internet Media Type application/http</a></h3> 1945 <p id="rfc.section.8.3.2.p.1">The application/http type can be used to enclose a pipeline of one or more HTTP request or response messages (not intermixed).</p> 1946 <p id="rfc.section.8.3.2.p.2"> </p> 1948 1947 <dl> 1949 1948 <dt>Type name:</dt> … … 1973 1972 <dd>none</dd> 1974 1973 <dt>Published specification:</dt> 1975 <dd>This specification (see <a href="#internet.media.type.application.http" title="Internet Media Type application/http">Section 9.3.2</a>).1974 <dd>This specification (see <a href="#internet.media.type.application.http" title="Internet Media Type application/http">Section 8.3.2</a>). 1976 1975 </dd> 1977 1976 <dt>Applications that use this media type:</dt> … … 1996 1995 <dd>IESG</dd> 1997 1996 </dl> 1998 <h1 id="rfc.section. 10"><a href="#rfc.section.10">10.</a> <a id="security.considerations" href="#security.considerations">Security Considerations</a></h1>1999 <p id="rfc.section. 10.p.1">This section is meant to inform application developers, information providers, and users of the security limitations in HTTP/1.11997 <h1 id="rfc.section.9"><a href="#rfc.section.9">9.</a> <a id="security.considerations" href="#security.considerations">Security Considerations</a></h1> 1998 <p id="rfc.section.9.p.1">This section is meant to inform application developers, information providers, and users of the security limitations in HTTP/1.1 2000 1999 as described by this document. The discussion does not include definitive solutions to the problems revealed, though it does 2001 2000 make some suggestions for reducing security risks. 2002 2001 </p> 2003 <h2 id="rfc.section. 10.1"><a href="#rfc.section.10.1">10.1</a> <a id="personal.information" href="#personal.information">Personal Information</a></h2>2004 <p id="rfc.section. 10.1.p.1">HTTP clients are often privy to large amounts of personal information (e.g. the user's name, location, mail address, passwords,2002 <h2 id="rfc.section.9.1"><a href="#rfc.section.9.1">9.1</a> <a id="personal.information" href="#personal.information">Personal Information</a></h2> 2003 <p id="rfc.section.9.1.p.1">HTTP clients are often privy to large amounts of personal information (e.g. the user's name, location, mail address, passwords, 2005 2004 encryption keys, etc.), and <em class="bcp14">SHOULD</em> be very careful to prevent unintentional leakage of this information. We very strongly recommend that a convenient interface 2006 2005 be provided for the user to control dissemination of such information, and that designers and implementors be particularly … … 2008 2007 highly adverse publicity for the implementor's company. 2009 2008 </p> 2010 <h2 id="rfc.section. 10.2"><a href="#rfc.section.10.2">10.2</a> <a id="abuse.of.server.log.information" href="#abuse.of.server.log.information">Abuse of Server Log Information</a></h2>2011 <p id="rfc.section. 10.2.p.1">A server is in the position to save personal data about a user's requests which might identify their reading patterns or subjects2009 <h2 id="rfc.section.9.2"><a href="#rfc.section.9.2">9.2</a> <a id="abuse.of.server.log.information" href="#abuse.of.server.log.information">Abuse of Server Log Information</a></h2> 2010 <p id="rfc.section.9.2.p.1">A server is in the position to save personal data about a user's requests which might identify their reading patterns or subjects 2012 2011 of interest. This information is clearly confidential in nature and its handling can be constrained by law in certain countries. 2013 2012 People using HTTP to provide data are responsible for ensuring that such material is not distributed without the permission 2014 2013 of any individuals that are identifiable by the published results. 2015 2014 </p> 2016 <h2 id="rfc.section. 10.3"><a href="#rfc.section.10.3">10.3</a> <a id="attack.pathname" href="#attack.pathname">Attacks Based On File and Path Names</a></h2>2017 <p id="rfc.section. 10.3.p.1">Implementations of HTTP origin servers <em class="bcp14">SHOULD</em> be careful to restrict the documents returned by HTTP requests to be only those that were intended by the server administrators.2015 <h2 id="rfc.section.9.3"><a href="#rfc.section.9.3">9.3</a> <a id="attack.pathname" href="#attack.pathname">Attacks Based On File and Path Names</a></h2> 2016 <p id="rfc.section.9.3.p.1">Implementations of HTTP origin servers <em class="bcp14">SHOULD</em> be careful to restrict the documents returned by HTTP requests to be only those that were intended by the server administrators. 2018 2017 If an HTTP server translates HTTP URIs directly into file system calls, the server <em class="bcp14">MUST</em> take special care not to serve files that were not intended to be delivered to HTTP clients. For example, UNIX, Microsoft 2019 2018 Windows, and other operating systems use ".." as a path component to indicate a directory level above the current one. On … … 2023 2022 bugs in such HTTP server implementations have turned into security risks. 2024 2023 </p> 2025 <h2 id="rfc.section. 10.4"><a href="#rfc.section.10.4">10.4</a> <a id="dns.spoofing" href="#dns.spoofing">DNS Spoofing</a></h2>2026 <p id="rfc.section. 10.4.p.1">Clients using HTTP rely heavily on the Domain Name Service, and are thus generally prone to security attacks based on the2024 <h2 id="rfc.section.9.4"><a href="#rfc.section.9.4">9.4</a> <a id="dns.spoofing" href="#dns.spoofing">DNS Spoofing</a></h2> 2025 <p id="rfc.section.9.4.p.1">Clients using HTTP rely heavily on the Domain Name Service, and are thus generally prone to security attacks based on the 2027 2026 deliberate mis-association of IP addresses and DNS names. Clients need to be cautious in assuming the continuing validity 2028 2027 of an IP number/DNS name association. 2029 2028 </p> 2030 <p id="rfc.section. 10.4.p.2">In particular, HTTP clients <em class="bcp14">SHOULD</em> rely on their name resolver for confirmation of an IP number/DNS name association, rather than caching the result of previous2029 <p id="rfc.section.9.4.p.2">In particular, HTTP clients <em class="bcp14">SHOULD</em> rely on their name resolver for confirmation of an IP number/DNS name association, rather than caching the result of previous 2031 2030 host name lookups. Many platforms already can cache host name lookups locally when appropriate, and they <em class="bcp14">SHOULD</em> be configured to do so. It is proper for these lookups to be cached, however, only when the TTL (Time To Live) information 2032 2031 reported by the name server makes it likely that the cached information will remain useful. 2033 2032 </p> 2034 <p id="rfc.section. 10.4.p.3">If HTTP clients cache the results of host name lookups in order to achieve a performance improvement, they <em class="bcp14">MUST</em> observe the TTL information reported by DNS.2035 </p> 2036 <p id="rfc.section. 10.4.p.4">If HTTP clients do not observe this rule, they could be spoofed when a previously-accessed server's IP address changes. As2033 <p id="rfc.section.9.4.p.3">If HTTP clients cache the results of host name lookups in order to achieve a performance improvement, they <em class="bcp14">MUST</em> observe the TTL information reported by DNS. 2034 </p> 2035 <p id="rfc.section.9.4.p.4">If HTTP clients do not observe this rule, they could be spoofed when a previously-accessed server's IP address changes. As 2037 2036 network renumbering is expected to become increasingly common <a href="#RFC1900" id="rfc.xref.RFC1900.2"><cite title="Renumbering Needs Work">[RFC1900]</cite></a>, the possibility of this form of attack will grow. Observing this requirement thus reduces this potential security vulnerability. 2038 2037 </p> 2039 <p id="rfc.section. 10.4.p.5">This requirement also improves the load-balancing behavior of clients for replicated servers using the same DNS name and reduces2038 <p id="rfc.section.9.4.p.5">This requirement also improves the load-balancing behavior of clients for replicated servers using the same DNS name and reduces 2040 2039 the likelihood of a user's experiencing failure in accessing sites which use that strategy. 2041 2040 </p> 2042 <h2 id="rfc.section. 10.5"><a href="#rfc.section.10.5">10.5</a> <a id="attack.proxies" href="#attack.proxies">Proxies and Caching</a></h2>2043 <p id="rfc.section. 10.5.p.1">By their very nature, HTTP proxies are men-in-the-middle, and represent an opportunity for man-in-the-middle attacks. Compromise2041 <h2 id="rfc.section.9.5"><a href="#rfc.section.9.5">9.5</a> <a id="attack.proxies" href="#attack.proxies">Proxies and Caching</a></h2> 2042 <p id="rfc.section.9.5.p.1">By their very nature, HTTP proxies are men-in-the-middle, and represent an opportunity for man-in-the-middle attacks. Compromise 2044 2043 of the systems on which the proxies run can result in serious security and privacy problems. Proxies have access to security-related 2045 2044 information, personal information about individual users and organizations, and proprietary information belonging to users … … 2047 2046 might be used in the commission of a wide range of potential attacks. 2048 2047 </p> 2049 <p id="rfc.section. 10.5.p.2">Proxy operators should protect the systems on which proxies run as they would protect any system that contains or transports2048 <p id="rfc.section.9.5.p.2">Proxy operators should protect the systems on which proxies run as they would protect any system that contains or transports 2050 2049 sensitive information. In particular, log information gathered at proxies often contains highly sensitive personal information, 2051 2050 and/or information about organizations. Log information should be carefully guarded, and appropriate guidelines for use developed 2052 and followed. (<a href="#abuse.of.server.log.information" title="Abuse of Server Log Information">Section 10.2</a>).2053 </p> 2054 <p id="rfc.section. 10.5.p.3">Proxy implementors should consider the privacy and security implications of their design and coding decisions, and of the2051 and followed. (<a href="#abuse.of.server.log.information" title="Abuse of Server Log Information">Section 9.2</a>). 2052 </p> 2053 <p id="rfc.section.9.5.p.3">Proxy implementors should consider the privacy and security implications of their design and coding decisions, and of the 2055 2054 configuration options they provide to proxy operators (especially the default configuration). 2056 2055 </p> 2057 <p id="rfc.section. 10.5.p.4">Users of a proxy need to be aware that they are no trustworthier than the people who run the proxy; HTTP itself cannot solve2056 <p id="rfc.section.9.5.p.4">Users of a proxy need to be aware that they are no trustworthier than the people who run the proxy; HTTP itself cannot solve 2058 2057 this problem. 2059 2058 </p> 2060 <p id="rfc.section. 10.5.p.5">The judicious use of cryptography, when appropriate, may suffice to protect against a broad range of security and privacy2059 <p id="rfc.section.9.5.p.5">The judicious use of cryptography, when appropriate, may suffice to protect against a broad range of security and privacy 2061 2060 attacks. Such cryptography is beyond the scope of the HTTP/1.1 specification. 2062 2061 </p> 2063 <h2 id="rfc.section. 10.6"><a href="#rfc.section.10.6">10.6</a> <a id="attack.DoS" href="#attack.DoS">Denial of Service Attacks on Proxies</a></h2>2064 <p id="rfc.section. 10.6.p.1">They exist. They are hard to defend against. Research continues. Beware.</p>2065 <h1 id="rfc.section.1 1"><a href="#rfc.section.11">11.</a> <a id="ack" href="#ack">Acknowledgments</a></h1>2066 <p id="rfc.section.1 1.p.1">HTTP has evolved considerably over the years. It has benefited from a large and active developer community--the many people2062 <h2 id="rfc.section.9.6"><a href="#rfc.section.9.6">9.6</a> <a id="attack.DoS" href="#attack.DoS">Denial of Service Attacks on Proxies</a></h2> 2063 <p id="rfc.section.9.6.p.1">They exist. They are hard to defend against. Research continues. Beware.</p> 2064 <h1 id="rfc.section.10"><a href="#rfc.section.10">10.</a> <a id="ack" href="#ack">Acknowledgments</a></h1> 2065 <p id="rfc.section.10.p.1">HTTP has evolved considerably over the years. It has benefited from a large and active developer community--the many people 2067 2066 who have participated on the www-talk mailing list--and it is that community which has been most responsible for the success 2068 2067 of HTTP and of the World-Wide Web in general. Marc Andreessen, Robert Cailliau, Daniel W. Connolly, Bob Denny, John Franks, … … 2070 2069 and Marc VanHeyningen deserve special recognition for their efforts in defining early aspects of the protocol. 2071 2070 </p> 2072 <p id="rfc.section.1 1.p.2">This document has benefited greatly from the comments of all those participating in the HTTP-WG. In addition to those already2071 <p id="rfc.section.10.p.2">This document has benefited greatly from the comments of all those participating in the HTTP-WG. In addition to those already 2073 2072 mentioned, the following individuals have contributed to this specification: 2074 2073 </p> 2075 <p id="rfc.section.1 1.p.3">Gary Adams, Harald Tveit Alvestrand, Keith Ball, Brian Behlendorf, Paul Burchard, Maurizio Codogno, Mike Cowlishaw, Roman2074 <p id="rfc.section.10.p.3">Gary Adams, Harald Tveit Alvestrand, Keith Ball, Brian Behlendorf, Paul Burchard, Maurizio Codogno, Mike Cowlishaw, Roman 2076 2075 Czyborra, Michael A. Dolan, Daniel DuBois, David J. Fiander, Alan Freier, Marc Hedlund, Greg Herlihy, Koen Holtman, Alex Hopmann, 2077 2076 Bob Jernigan, Shel Kaphan, Rohit Khare, John Klensin, Martijn Koster, Alexei Kosut, David M. Kristol, Daniel LaLiberte, Ben … … 2081 2080 Weinman, Francois Yergeau, Mary Ellen Zurko, Josh Cohen. 2082 2081 </p> 2083 <p id="rfc.section.1 1.p.4">Thanks to the "cave men" of Palo Alto. You know who you are.</p>2084 <p id="rfc.section.1 1.p.5">Jim Gettys (the editor of <a href="#RFC2616" id="rfc.xref.RFC2616.2"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>) wishes particularly to thank Roy Fielding, the editor of <a href="#RFC2068" id="rfc.xref.RFC2068.5"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2068]</cite></a>, along with John Klensin, Jeff Mogul, Paul Leach, Dave Kristol, Koen Holtman, John Franks, Josh Cohen, Alex Hopmann, Scott2082 <p id="rfc.section.10.p.4">Thanks to the "cave men" of Palo Alto. You know who you are.</p> 2083 <p id="rfc.section.10.p.5">Jim Gettys (the editor of <a href="#RFC2616" id="rfc.xref.RFC2616.2"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>) wishes particularly to thank Roy Fielding, the editor of <a href="#RFC2068" id="rfc.xref.RFC2068.5"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2068]</cite></a>, along with John Klensin, Jeff Mogul, Paul Leach, Dave Kristol, Koen Holtman, John Franks, Josh Cohen, Alex Hopmann, Scott 2085 2084 Lawrence, and Larry Masinter for their help. And thanks go particularly to Jeff Mogul and Scott Lawrence for performing the 2086 2085 "MUST/MAY/SHOULD" audit. 2087 2086 </p> 2088 <p id="rfc.section.1 1.p.6">The Apache Group, Anselm Baird-Smith, author of Jigsaw, and Henrik Frystyk implemented RFC 2068 early, and we wish to thank2087 <p id="rfc.section.10.p.6">The Apache Group, Anselm Baird-Smith, author of Jigsaw, and Henrik Frystyk implemented RFC 2068 early, and we wish to thank 2089 2088 them for the discovery of many of the problems that this document attempts to rectify. 2090 2089 </p> 2091 <p id="rfc.section.1 1.p.7">This specification makes heavy use of the augmented BNF and generic constructs defined by David H. Crocker for <a href="#RFC5234" id="rfc.xref.RFC5234.4"><cite title="Augmented BNF for Syntax Specifications: ABNF">[RFC5234]</cite></a>. Similarly, it reuses many of the definitions provided by Nathaniel Borenstein and Ned Freed for MIME <a href="#RFC2045" id="rfc.xref.RFC2045.3"><cite title="Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies">[RFC2045]</cite></a>. We hope that their inclusion in this specification will help reduce past confusion over the relationship between HTTP and2090 <p id="rfc.section.10.p.7">This specification makes heavy use of the augmented BNF and generic constructs defined by David H. Crocker for <a href="#RFC5234" id="rfc.xref.RFC5234.4"><cite title="Augmented BNF for Syntax Specifications: ABNF">[RFC5234]</cite></a>. Similarly, it reuses many of the definitions provided by Nathaniel Borenstein and Ned Freed for MIME <a href="#RFC2045" id="rfc.xref.RFC2045.3"><cite title="Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies">[RFC2045]</cite></a>. We hope that their inclusion in this specification will help reduce past confusion over the relationship between HTTP and 2092 2091 Internet mail message formats. 2093 2092 </p> 2094 <h1 id="rfc.references"><a id="rfc.section.1 2" href="#rfc.section.12">12.</a> References2093 <h1 id="rfc.references"><a id="rfc.section.11" href="#rfc.section.11">11.</a> References 2095 2094 </h1> 2096 <h2 id="rfc.references.1"><a href="#rfc.section.1 2.1" id="rfc.section.12.1">12.1</a> Normative References2095 <h2 id="rfc.references.1"><a href="#rfc.section.11.1" id="rfc.section.11.1">11.1</a> Normative References 2097 2096 </h2> 2098 2097 <table summary="Normative References"> … … 2154 2153 </tr> 2155 2154 </table> 2156 <h2 id="rfc.references.2"><a href="#rfc.section.1 2.2" id="rfc.section.12.2">12.2</a> Informative References2155 <h2 id="rfc.references.2"><a href="#rfc.section.11.2" id="rfc.section.11.2">11.2</a> Informative References 2157 2156 </h2> 2158 2157 <table summary="Informative References"> … … 2349 2348 <p id="rfc.section.B.1.p.1">This section summarizes major differences between versions HTTP/1.0 and HTTP/1.1.</p> 2350 2349 <h3 id="rfc.section.B.1.1"><a href="#rfc.section.B.1.1">B.1.1</a> <a id="changes.to.simplify.multi-homed.web.servers.and.conserve.ip.addresses" href="#changes.to.simplify.multi-homed.web.servers.and.conserve.ip.addresses">Changes to Simplify Multi-homed Web Servers and Conserve IP Addresses</a></h3> 2351 <p id="rfc.section.B.1.1.p.1">The requirements that clients and servers support the Host request-header, report an error if the Host request-header (<a href="#header.host" id="rfc.xref.header.host.2" title="Host">Section 8.4</a>) is missing from an HTTP/1.1 request, and accept absolute URIs (<a href="#request-uri" title="Request-URI">Section 5.1.2</a>) are among the most important changes defined by this specification.2350 <p id="rfc.section.B.1.1.p.1">The requirements that clients and servers support the Host request-header, report an error if the Host request-header (<a href="#header.host" id="rfc.xref.header.host.2" title="Host">Section 7.4</a>) is missing from an HTTP/1.1 request, and accept absolute URIs (<a href="#request-uri" title="Request-URI">Section 4.1.2</a>) are among the most important changes defined by this specification. 2352 2351 </p> 2353 2352 <p id="rfc.section.B.1.1.p.2">Older HTTP/1.0 clients assumed a one-to-one relationship of IP addresses and servers; there was no other established mechanism … … 2382 2381 Therefore, we need some other mechanism for indicating a persistent connection is desired, which is safe to use even when 2383 2382 talking to an old proxy that ignores Connection. Persistent connections are the default for HTTP/1.1 messages; we introduce 2384 a new keyword (Connection: close) for declaring non-persistence. See <a href="#header.connection" id="rfc.xref.header.connection.7" title="Connection">Section 8.1</a>.2383 a new keyword (Connection: close) for declaring non-persistence. See <a href="#header.connection" id="rfc.xref.header.connection.7" title="Connection">Section 7.1</a>. 2385 2384 </p> 2386 2385 <p id="rfc.section.B.2.p.3">The original HTTP/1.0 form of persistent connections (the Connection: Keep-Alive and Keep-Alive header) is documented in <a href="#RFC2068" id="rfc.xref.RFC2068.7"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2068]</cite></a>. … … 2392 2391 <p id="rfc.section.B.3.p.2">Transfer-coding and message lengths all interact in ways that required fixing exactly when chunked encoding is used (to allow 2393 2392 for transfer encoding that may not be self delimiting); it was important to straighten out exactly how message lengths are 2394 computed. (Sections <a href="#transfer.codings" title="Transfer Codings"> 3.4</a>, <a href="#message.length" title="Message Length">4.4</a>, <a href="#header.content-length" id="rfc.xref.header.content-length.3" title="Content-Length">8.2</a>, see also <a href="#Part3" id="rfc.xref.Part3.14"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>, <a href="#Part5" id="rfc.xref.Part5.1"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a> and <a href="#Part6" id="rfc.xref.Part6.8"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>)2393 computed. (Sections <a href="#transfer.codings" title="Transfer Codings">2.4</a>, <a href="#message.length" title="Message Length">3.4</a>, <a href="#header.content-length" id="rfc.xref.header.content-length.3" title="Content-Length">7.2</a>, see also <a href="#Part3" id="rfc.xref.Part3.14"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>, <a href="#Part5" id="rfc.xref.Part5.1"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a> and <a href="#Part6" id="rfc.xref.Part6.8"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) 2395 2394 </p> 2396 2395 <p id="rfc.section.B.3.p.3">The use and interpretation of HTTP version numbers has been clarified by <a href="#RFC2145" id="rfc.xref.RFC2145.3"><cite title="Use and Interpretation of HTTP Version Numbers">[RFC2145]</cite></a>. Require proxies to upgrade requests to highest protocol version they support to deal with problems discovered in HTTP/1.0 2397 implementations (<a href="#http.version" title="HTTP Version">Section 3.1</a>)2396 implementations (<a href="#http.version" title="HTTP Version">Section 2.1</a>) 2398 2397 </p> 2399 2398 <p id="rfc.section.B.3.p.4">Transfer-coding had significant problems, particularly with interactions with chunked encoding. The solution is that transfer-codings … … 2401 2400 codings), a new header field (TE) and enabling trailer headers in the future. Transfer encoding is a major performance benefit, 2402 2401 so it was worth fixing <a href="#Nie1997" id="rfc.xref.Nie1997.2"><cite title="Network Performance Effects of HTTP/1.1, CSS1, and PNG">[Nie1997]</cite></a>. TE also solves another, obscure, downward interoperability problem that could have occurred due to interactions between 2403 authentication trailers, chunked encoding and HTTP/1.0 clients.(Section <a href="#transfer.codings" title="Transfer Codings"> 3.4</a>, <a href="#chunked.transfer.encoding" title="Chunked Transfer Coding">3.4.1</a>, and <a href="#header.te" id="rfc.xref.header.te.4" title="TE">8.5</a>)2402 authentication trailers, chunked encoding and HTTP/1.0 clients.(Section <a href="#transfer.codings" title="Transfer Codings">2.4</a>, <a href="#chunked.transfer.encoding" title="Chunked Transfer Coding">2.4.1</a>, and <a href="#header.te" id="rfc.xref.header.te.4" title="TE">7.5</a>) 2404 2403 </p> 2405 2404 <h2 id="rfc.section.B.4"><a href="#rfc.section.B.4">B.4</a> <a id="changes.from.rfc.2616" href="#changes.from.rfc.2616">Changes from RFC 2616</a></h2> 2406 2405 <p id="rfc.section.B.4.p.1">Rules about implicit linear white space between certain grammar productions have been removed; now it's only allowed when 2407 2406 specifically pointed out in the ABNF. The CHAR rule does not allow the NUL character anymore (this affects the comment and 2408 quoted-string rules). Furthermore, the quoted-pair rule does not allow escaping NUL, CR or LF anymore. (<a href="#basic.rules" title="Basic Rules">Section 2.2</a>)2409 </p> 2410 <p id="rfc.section.B.4.p.2">Clarify that HTTP-Version is case sensitive. (<a href="#http.version" title="HTTP Version">Section 3.1</a>)2411 </p> 2412 <p id="rfc.section.B.4.p.3">Remove reference to non-existant identity transfer-coding value tokens. (Sections <a href="#transfer.codings" title="Transfer Codings"> 3.4</a> and <a href="#message.length" title="Message Length">4.4</a>)2413 </p> 2414 <p id="rfc.section.B.4.p.4">Clarification that the chunk length does not include the count of the octets in the chunk header and trailer. (<a href="#chunked.transfer.encoding" title="Chunked Transfer Coding">Section 3.4.1</a>)2415 </p> 2416 <p id="rfc.section.B.4.p.5">Update use of abs_path production from RFC1808 to the path-absolute + query components of RFC3986. (<a href="#request-uri" title="Request-URI">Section 5.1.2</a>)2417 </p> 2418 <p id="rfc.section.B.4.p.6">Clarify exactly when close connection options must be sent. (<a href="#header.connection" id="rfc.xref.header.connection.8" title="Connection">Section 8.1</a>)2407 quoted-string rules). Furthermore, the quoted-pair rule does not allow escaping NUL, CR or LF anymore. (<a href="#basic.rules" title="Basic Rules">Section 1.2.2</a>) 2408 </p> 2409 <p id="rfc.section.B.4.p.2">Clarify that HTTP-Version is case sensitive. (<a href="#http.version" title="HTTP Version">Section 2.1</a>) 2410 </p> 2411 <p id="rfc.section.B.4.p.3">Remove reference to non-existant identity transfer-coding value tokens. (Sections <a href="#transfer.codings" title="Transfer Codings">2.4</a> and <a href="#message.length" title="Message Length">3.4</a>) 2412 </p> 2413 <p id="rfc.section.B.4.p.4">Clarification that the chunk length does not include the count of the octets in the chunk header and trailer. (<a href="#chunked.transfer.encoding" title="Chunked Transfer Coding">Section 2.4.1</a>) 2414 </p> 2415 <p id="rfc.section.B.4.p.5">Update use of abs_path production from RFC1808 to the path-absolute + query components of RFC3986. (<a href="#request-uri" title="Request-URI">Section 4.1.2</a>) 2416 </p> 2417 <p id="rfc.section.B.4.p.6">Clarify exactly when close connection options must be sent. (<a href="#header.connection" id="rfc.xref.header.connection.8" title="Connection">Section 7.1</a>) 2419 2418 </p> 2420 2419 <h1 id="rfc.section.C"><a href="#rfc.section.C">C.</a> <a id="terminology" href="#terminology">Terminology</a></h1> … … 2428 2427 </p> 2429 2428 <dl class="empty"> 2430 <dd>The basic unit of HTTP communication, consisting of a structured sequence of octets matching the syntax defined in <a href="#http.message" title="HTTP Message">Section 4</a> and transmitted via the connection.2429 <dd>The basic unit of HTTP communication, consisting of a structured sequence of octets matching the syntax defined in <a href="#http.message" title="HTTP Message">Section 3</a> and transmitted via the connection. 2431 2430 </dd> 2432 2431 </dl> … … 2434 2433 </p> 2435 2434 <dl class="empty"> 2436 <dd>An HTTP request message, as defined in <a href="#request" title="Request">Section 5</a>.2435 <dd>An HTTP request message, as defined in <a href="#request" title="Request">Section 4</a>. 2437 2436 </dd> 2438 2437 </dl> … … 2440 2439 </p> 2441 2440 <dl class="empty"> 2442 <dd>An HTTP response message, as defined in <a href="#response" title="Response">Section 6</a>.2441 <dd>An HTTP response message, as defined in <a href="#response" title="Response">Section 5</a>. 2443 2442 </dd> 2444 2443 </dl> … … 2446 2445 </p> 2447 2446 <dl class="empty"> 2448 <dd>A network data object or service that can be identified by a URI, as defined in <a href="#uri" title="Uniform Resource Identifiers">Section 3.2</a>. Resources may be available in multiple representations (e.g. multiple languages, data formats, size, and resolutions) or2447 <dd>A network data object or service that can be identified by a URI, as defined in <a href="#uri" title="Uniform Resource Identifiers">Section 2.2</a>. Resources may be available in multiple representations (e.g. multiple languages, data formats, size, and resolutions) or 2449 2448 vary in other ways. 2450 2449 </dd> … … 2733 2732 <ul class="ind"> 2734 2733 <li class="indline0"><a id="rfc.index.A" href="#rfc.index.A"><b>A</b></a><ul class="ind"> 2735 <li class="indline1">application/http Media Type <a class="iref" href="#rfc.iref.a.1"><b> 9.3.2</b></a></li>2734 <li class="indline1">application/http Media Type <a class="iref" href="#rfc.iref.a.1"><b>8.3.2</b></a></li> 2736 2735 </ul> 2737 2736 </li> … … 2741 2740 <li class="indline1">client <a class="iref" href="#rfc.iref.c.5">C</a></li> 2742 2741 <li class="indline1">connection <a class="iref" href="#rfc.iref.c.3">C</a></li> 2743 <li class="indline1">Connection header <a class="iref" href="#rfc.xref.header.connection.1"> 4.5</a>, <a class="iref" href="#rfc.xref.header.connection.2">7.1.2</a>, <a class="iref" href="#rfc.xref.header.connection.3">7.1.3</a>, <a class="iref" href="#rfc.iref.c.1"><b>8.1</b></a>, <a class="iref" href="#rfc.xref.header.connection.4">8.5</a>, <a class="iref" href="#rfc.xref.header.connection.5">8.8</a>, <a class="iref" href="#rfc.xref.header.connection.6">9.1</a>, <a class="iref" href="#rfc.xref.header.connection.7">B.2</a>, <a class="iref" href="#rfc.xref.header.connection.8">B.4</a></li>2742 <li class="indline1">Connection header <a class="iref" href="#rfc.xref.header.connection.1">3.5</a>, <a class="iref" href="#rfc.xref.header.connection.2">6.1.2</a>, <a class="iref" href="#rfc.xref.header.connection.3">6.1.3</a>, <a class="iref" href="#rfc.iref.c.1"><b>7.1</b></a>, <a class="iref" href="#rfc.xref.header.connection.4">7.5</a>, <a class="iref" href="#rfc.xref.header.connection.5">7.8</a>, <a class="iref" href="#rfc.xref.header.connection.6">8.1</a>, <a class="iref" href="#rfc.xref.header.connection.7">B.2</a>, <a class="iref" href="#rfc.xref.header.connection.8">B.4</a></li> 2744 2743 <li class="indline1">content negotiation <a class="iref" href="#rfc.iref.c.4">C</a></li> 2745 <li class="indline1">Content-Length header <a class="iref" href="#rfc.xref.header.content-length.1"> 4.4</a>, <a class="iref" href="#rfc.iref.c.2"><b>8.2</b></a>, <a class="iref" href="#rfc.xref.header.content-length.2">9.1</a>, <a class="iref" href="#rfc.xref.header.content-length.3">B.3</a></li>2744 <li class="indline1">Content-Length header <a class="iref" href="#rfc.xref.header.content-length.1">3.4</a>, <a class="iref" href="#rfc.iref.c.2"><b>7.2</b></a>, <a class="iref" href="#rfc.xref.header.content-length.2">8.1</a>, <a class="iref" href="#rfc.xref.header.content-length.3">B.3</a></li> 2746 2745 </ul> 2747 2746 </li> 2748 2747 <li class="indline0"><a id="rfc.index.D" href="#rfc.index.D"><b>D</b></a><ul class="ind"> 2749 <li class="indline1">Date header <a class="iref" href="#rfc.xref.header.date.1"> 4.5</a>, <a class="iref" href="#rfc.iref.d.1"><b>8.3</b></a>, <a class="iref" href="#rfc.xref.header.date.2">9.1</a></li>2748 <li class="indline1">Date header <a class="iref" href="#rfc.xref.header.date.1">3.5</a>, <a class="iref" href="#rfc.iref.d.1"><b>7.3</b></a>, <a class="iref" href="#rfc.xref.header.date.2">8.1</a></li> 2750 2749 <li class="indline1">downstream <a class="iref" href="#rfc.iref.d.2">C</a></li> 2751 2750 </ul> … … 2759 2758 <li class="indline1"><tt>Grammar</tt> 2760 2759 <ul class="ind"> 2761 <li class="indline1"><tt>absolute-URI</tt> <a class="iref" href="#rfc.iref.g.16"><b> 3.2</b></a></li>2762 <li class="indline1"><tt>asctime-date</tt> <a class="iref" href="#rfc.iref.g.29"><b> 3.3.1</b></a></li>2763 <li class="indline1"><tt>attribute</tt> <a class="iref" href="#rfc.iref.g.40"><b> 3.4</b></a></li>2764 <li class="indline1"><tt>authority</tt> <a class="iref" href="#rfc.iref.g.17"><b> 3.2</b></a></li>2765 <li class="indline1"><tt>BWS</tt> <a class="iref" href="#rfc.iref.g.3"><b> 2.2</b></a></li>2766 <li class="indline1"><tt>chunk</tt> <a class="iref" href="#rfc.iref.g.43"><b> 3.4.1</b></a></li>2767 <li class="indline1"><tt>chunk-data</tt> <a class="iref" href="#rfc.iref.g.49"><b> 3.4.1</b></a></li>2768 <li class="indline1"><tt>chunk-ext</tt> <a class="iref" href="#rfc.iref.g.46"><b> 3.4.1</b></a></li>2769 <li class="indline1"><tt>chunk-ext-name</tt> <a class="iref" href="#rfc.iref.g.47"><b> 3.4.1</b></a></li>2770 <li class="indline1"><tt>chunk-ext-val</tt> <a class="iref" href="#rfc.iref.g.48"><b> 3.4.1</b></a></li>2771 <li class="indline1"><tt>chunk-size</tt> <a class="iref" href="#rfc.iref.g.44"><b> 3.4.1</b></a></li>2772 <li class="indline1"><tt>Chunked-Body</tt> <a class="iref" href="#rfc.iref.g.42"><b> 3.4.1</b></a></li>2773 <li class="indline1"><tt>comment</tt> <a class="iref" href="#rfc.iref.g.7"><b> 2.2</b></a></li>2774 <li class="indline1"><tt>Connection</tt> <a class="iref" href="#rfc.iref.g.72"><b> 8.1</b></a></li>2775 <li class="indline1"><tt>connection-token</tt> <a class="iref" href="#rfc.iref.g.74"><b> 8.1</b></a></li>2776 <li class="indline1"><tt>Connection-v</tt> <a class="iref" href="#rfc.iref.g.73"><b> 8.1</b></a></li>2777 <li class="indline1"><tt>Content-Length</tt> <a class="iref" href="#rfc.iref.g.75"><b> 8.2</b></a></li>2778 <li class="indline1"><tt>Content-Length-v</tt> <a class="iref" href="#rfc.iref.g.76"><b> 8.2</b></a></li>2779 <li class="indline1"><tt>ctext</tt> <a class="iref" href="#rfc.iref.g.8"><b> 2.2</b></a></li>2780 <li class="indline1"><tt>Date</tt> <a class="iref" href="#rfc.iref.g.77"><b> 8.3</b></a></li>2781 <li class="indline1"><tt>Date-v</tt> <a class="iref" href="#rfc.iref.g.78"><b> 8.3</b></a></li>2782 <li class="indline1"><tt>date1</tt> <a class="iref" href="#rfc.iref.g.30"><b> 3.3.1</b></a></li>2783 <li class="indline1"><tt>date2</tt> <a class="iref" href="#rfc.iref.g.31"><b> 3.3.1</b></a></li>2784 <li class="indline1"><tt>date3</tt> <a class="iref" href="#rfc.iref.g.32"><b> 3.3.1</b></a></li>2785 <li class="indline1"><tt>extension-code</tt> <a class="iref" href="#rfc.iref.g.70"><b> 6.1.1</b></a></li>2786 <li class="indline1"><tt>extension-method</tt> <a class="iref" href="#rfc.iref.g.65"><b> 5.1.1</b></a></li>2787 <li class="indline1"><tt>field-content</tt> <a class="iref" href="#rfc.iref.g.59"><b> 4.2</b></a></li>2788 <li class="indline1"><tt>field-name</tt> <a class="iref" href="#rfc.iref.g.57"><b> 4.2</b></a></li>2789 <li class="indline1"><tt>field-value</tt> <a class="iref" href="#rfc.iref.g.58"><b> 4.2</b></a></li>2790 <li class="indline1"><tt>general-header</tt> <a class="iref" href="#rfc.iref.g.61"><b> 4.5</b></a></li>2791 <li class="indline1"><tt>generic-message</tt> <a class="iref" href="#rfc.iref.g.54"><b> 4.1</b></a></li>2792 <li class="indline1"><tt>Host</tt> <a class="iref" href="#rfc.iref.g.79"><b> 8.4</b></a></li>2793 <li class="indline1"><tt>Host-v</tt> <a class="iref" href="#rfc.iref.g.80"><b> 8.4</b></a></li>2794 <li class="indline1"><tt>HTTP-date</tt> <a class="iref" href="#rfc.iref.g.25"><b> 3.3.1</b></a></li>2795 <li class="indline1"><tt>HTTP-message</tt> <a class="iref" href="#rfc.iref.g.53"><b> 4.1</b></a></li>2796 <li class="indline1"><tt>HTTP-Prot-Name</tt> <a class="iref" href="#rfc.iref.g.14"><b> 3.1</b></a></li>2797 <li class="indline1"><tt>http-URI</tt> <a class="iref" href="#rfc.iref.g.24"><b> 3.2.1</b></a></li>2798 <li class="indline1"><tt>HTTP-Version</tt> <a class="iref" href="#rfc.iref.g.13"><b> 3.1</b></a></li>2799 <li class="indline1"><tt>last-chunk</tt> <a class="iref" href="#rfc.iref.g.45"><b> 3.4.1</b></a></li>2800 <li class="indline1"><tt>message-body</tt> <a class="iref" href="#rfc.iref.g.60"><b> 4.3</b></a></li>2801 <li class="indline1"><tt>message-header</tt> <a class="iref" href="#rfc.iref.g.56"><b> 4.2</b></a></li>2802 <li class="indline1"><tt>Method</tt> <a class="iref" href="#rfc.iref.g.64"><b> 5.1.1</b></a></li>2803 <li class="indline1"><tt>month</tt> <a class="iref" href="#rfc.iref.g.36"><b> 3.3.1</b></a></li>2804 <li class="indline1"><tt>obsolete-date</tt> <a class="iref" href="#rfc.iref.g.27"><b> 3.3.1</b></a></li>2805 <li class="indline1"><tt>OWS</tt> <a class="iref" href="#rfc.iref.g.1"><b> 2.2</b></a></li>2806 <li class="indline1"><tt>parameter</tt> <a class="iref" href="#rfc.iref.g.39"><b> 3.4</b></a></li>2807 <li class="indline1"><tt>path-absolute</tt> <a class="iref" href="#rfc.iref.g.18"><b> 3.2</b></a></li>2808 <li class="indline1"><tt>port</tt> <a class="iref" href="#rfc.iref.g.19"><b> 3.2</b></a></li>2809 <li class="indline1"><tt>product</tt> <a class="iref" href="#rfc.iref.g.51"><b> 3.5</b></a></li>2810 <li class="indline1"><tt>product-version</tt> <a class="iref" href="#rfc.iref.g.52"><b> 3.5</b></a></li>2811 <li class="indline1"><tt>protocol-name</tt> <a class="iref" href="#rfc.iref.g.93"><b> 8.9</b></a></li>2812 <li class="indline1"><tt>protocol-version</tt> <a class="iref" href="#rfc.iref.g.94"><b> 8.9</b></a></li>2813 <li class="indline1"><tt>pseudonym</tt> <a class="iref" href="#rfc.iref.g.96"><b> 8.9</b></a></li>2814 <li class="indline1"><tt>qdtext</tt> <a class="iref" href="#rfc.iref.g.10"><b> 2.2</b></a></li>2815 <li class="indline1"><tt>query</tt> <a class="iref" href="#rfc.iref.g.20"><b> 3.2</b></a></li>2816 <li class="indline1"><tt>quoted-pair</tt> <a class="iref" href="#rfc.iref.g.12"><b> 2.2</b></a></li>2817 <li class="indline1"><tt>quoted-string</tt> <a class="iref" href="#rfc.iref.g.9"><b> 2.2</b></a></li>2818 <li class="indline1"><tt>quoted-text</tt> <a class="iref" href="#rfc.iref.g.11"><b> 2.2</b></a></li>2819 <li class="indline1"><tt>Reason-Phrase</tt> <a class="iref" href="#rfc.iref.g.71"><b> 6.1.1</b></a></li>2820 <li class="indline1"><tt>received-by</tt> <a class="iref" href="#rfc.iref.g.95"><b> 8.9</b></a></li>2821 <li class="indline1"><tt>received-protocol</tt> <a class="iref" href="#rfc.iref.g.92"><b> 8.9</b></a></li>2822 <li class="indline1"><tt>relative-part</tt> <a class="iref" href="#rfc.iref.g.23"><b> 3.2</b></a></li>2823 <li class="indline1"><tt>relativeURI</tt> <a class="iref" href="#rfc.iref.g.22"><b> 3.2</b></a></li>2824 <li class="indline1"><tt>Request</tt> <a class="iref" href="#rfc.iref.g.62"><b> 5</b></a></li>2825 <li class="indline1"><tt>Request-Line</tt> <a class="iref" href="#rfc.iref.g.63"><b> 5.1</b></a></li>2826 <li class="indline1"><tt>Request-URI</tt> <a class="iref" href="#rfc.iref.g.66"><b> 5.1.2</b></a></li>2827 <li class="indline1"><tt>Response</tt> <a class="iref" href="#rfc.iref.g.67"><b> 6</b></a></li>2828 <li class="indline1"><tt>rfc1123-date</tt> <a class="iref" href="#rfc.iref.g.26"><b> 3.3.1</b></a></li>2829 <li class="indline1"><tt>rfc850-date</tt> <a class="iref" href="#rfc.iref.g.28"><b> 3.3.1</b></a></li>2830 <li class="indline1"><tt>RWS</tt> <a class="iref" href="#rfc.iref.g.2"><b> 2.2</b></a></li>2831 <li class="indline1"><tt>start-line</tt> <a class="iref" href="#rfc.iref.g.55"><b> 4.1</b></a></li>2832 <li class="indline1"><tt>Status-Code</tt> <a class="iref" href="#rfc.iref.g.69"><b> 6.1.1</b></a></li>2833 <li class="indline1"><tt>Status-Line</tt> <a class="iref" href="#rfc.iref.g.68"><b> 6.1</b></a></li>2834 <li class="indline1"><tt>t-codings</tt> <a class="iref" href="#rfc.iref.g.83"><b> 8.5</b></a></li>2835 <li class="indline1"><tt>tchar</tt> <a class="iref" href="#rfc.iref.g.6"><b> 2.2</b></a></li>2836 <li class="indline1"><tt>TE</tt> <a class="iref" href="#rfc.iref.g.81"><b> 8.5</b></a></li>2837 <li class="indline1"><tt>TE-v</tt> <a class="iref" href="#rfc.iref.g.82"><b> 8.5</b></a></li>2838 <li class="indline1"><tt>TEXT</tt> <a class="iref" href="#rfc.iref.g.4"><b> 2.2</b></a></li>2839 <li class="indline1"><tt>time</tt> <a class="iref" href="#rfc.iref.g.33"><b> 3.3.1</b></a></li>2840 <li class="indline1"><tt>token</tt> <a class="iref" href="#rfc.iref.g.5"><b> 2.2</b></a></li>2841 <li class="indline1"><tt>Trailer</tt> <a class="iref" href="#rfc.iref.g.84"><b> 8.6</b></a></li>2842 <li class="indline1"><tt>trailer-part</tt> <a class="iref" href="#rfc.iref.g.50"><b> 3.4.1</b></a></li>2843 <li class="indline1"><tt>Trailer-v</tt> <a class="iref" href="#rfc.iref.g.85"><b> 8.6</b></a></li>2844 <li class="indline1"><tt>transfer-coding</tt> <a class="iref" href="#rfc.iref.g.37"><b> 3.4</b></a></li>2845 <li class="indline1"><tt>Transfer-Encoding</tt> <a class="iref" href="#rfc.iref.g.86"><b> 8.7</b></a></li>2846 <li class="indline1"><tt>Transfer-Encoding-v</tt> <a class="iref" href="#rfc.iref.g.87"><b> 8.7</b></a></li>2847 <li class="indline1"><tt>transfer-extension</tt> <a class="iref" href="#rfc.iref.g.38"><b> 3.4</b></a></li>2848 <li class="indline1"><tt>Upgrade</tt> <a class="iref" href="#rfc.iref.g.88"><b> 8.8</b></a></li>2849 <li class="indline1"><tt>Upgrade-v</tt> <a class="iref" href="#rfc.iref.g.89"><b> 8.8</b></a></li>2850 <li class="indline1"><tt>uri-host</tt> <a class="iref" href="#rfc.iref.g.21"><b> 3.2</b></a></li>2851 <li class="indline1"><tt>URI-reference</tt> <a class="iref" href="#rfc.iref.g.15"><b> 3.2</b></a></li>2852 <li class="indline1"><tt>value</tt> <a class="iref" href="#rfc.iref.g.41"><b> 3.4</b></a></li>2853 <li class="indline1"><tt>Via</tt> <a class="iref" href="#rfc.iref.g.90"><b> 8.9</b></a></li>2854 <li class="indline1"><tt>Via-v</tt> <a class="iref" href="#rfc.iref.g.91"><b> 8.9</b></a></li>2855 <li class="indline1"><tt>weekday</tt> <a class="iref" href="#rfc.iref.g.35"><b> 3.3.1</b></a></li>2856 <li class="indline1"><tt>wkday</tt> <a class="iref" href="#rfc.iref.g.34"><b> 3.3.1</b></a></li>2760 <li class="indline1"><tt>absolute-URI</tt> <a class="iref" href="#rfc.iref.g.16"><b>2.2</b></a></li> 2761 <li class="indline1"><tt>asctime-date</tt> <a class="iref" href="#rfc.iref.g.29"><b>2.3.1</b></a></li> 2762 <li class="indline1"><tt>attribute</tt> <a class="iref" href="#rfc.iref.g.40"><b>2.4</b></a></li> 2763 <li class="indline1"><tt>authority</tt> <a class="iref" href="#rfc.iref.g.17"><b>2.2</b></a></li> 2764 <li class="indline1"><tt>BWS</tt> <a class="iref" href="#rfc.iref.g.3"><b>1.2.2</b></a></li> 2765 <li class="indline1"><tt>chunk</tt> <a class="iref" href="#rfc.iref.g.43"><b>2.4.1</b></a></li> 2766 <li class="indline1"><tt>chunk-data</tt> <a class="iref" href="#rfc.iref.g.49"><b>2.4.1</b></a></li> 2767 <li class="indline1"><tt>chunk-ext</tt> <a class="iref" href="#rfc.iref.g.46"><b>2.4.1</b></a></li> 2768 <li class="indline1"><tt>chunk-ext-name</tt> <a class="iref" href="#rfc.iref.g.47"><b>2.4.1</b></a></li> 2769 <li class="indline1"><tt>chunk-ext-val</tt> <a class="iref" href="#rfc.iref.g.48"><b>2.4.1</b></a></li> 2770 <li class="indline1"><tt>chunk-size</tt> <a class="iref" href="#rfc.iref.g.44"><b>2.4.1</b></a></li> 2771 <li class="indline1"><tt>Chunked-Body</tt> <a class="iref" href="#rfc.iref.g.42"><b>2.4.1</b></a></li> 2772 <li class="indline1"><tt>comment</tt> <a class="iref" href="#rfc.iref.g.7"><b>1.2.2</b></a></li> 2773 <li class="indline1"><tt>Connection</tt> <a class="iref" href="#rfc.iref.g.72"><b>7.1</b></a></li> 2774 <li class="indline1"><tt>connection-token</tt> <a class="iref" href="#rfc.iref.g.74"><b>7.1</b></a></li> 2775 <li class="indline1"><tt>Connection-v</tt> <a class="iref" href="#rfc.iref.g.73"><b>7.1</b></a></li> 2776 <li class="indline1"><tt>Content-Length</tt> <a class="iref" href="#rfc.iref.g.75"><b>7.2</b></a></li> 2777 <li class="indline1"><tt>Content-Length-v</tt> <a class="iref" href="#rfc.iref.g.76"><b>7.2</b></a></li> 2778 <li class="indline1"><tt>ctext</tt> <a class="iref" href="#rfc.iref.g.8"><b>1.2.2</b></a></li> 2779 <li class="indline1"><tt>Date</tt> <a class="iref" href="#rfc.iref.g.77"><b>7.3</b></a></li> 2780 <li class="indline1"><tt>Date-v</tt> <a class="iref" href="#rfc.iref.g.78"><b>7.3</b></a></li> 2781 <li class="indline1"><tt>date1</tt> <a class="iref" href="#rfc.iref.g.30"><b>2.3.1</b></a></li> 2782 <li class="indline1"><tt>date2</tt> <a class="iref" href="#rfc.iref.g.31"><b>2.3.1</b></a></li> 2783 <li class="indline1"><tt>date3</tt> <a class="iref" href="#rfc.iref.g.32"><b>2.3.1</b></a></li> 2784 <li class="indline1"><tt>extension-code</tt> <a class="iref" href="#rfc.iref.g.70"><b>5.1.1</b></a></li> 2785 <li class="indline1"><tt>extension-method</tt> <a class="iref" href="#rfc.iref.g.65"><b>4.1.1</b></a></li> 2786 <li class="indline1"><tt>field-content</tt> <a class="iref" href="#rfc.iref.g.59"><b>3.2</b></a></li> 2787 <li class="indline1"><tt>field-name</tt> <a class="iref" href="#rfc.iref.g.57"><b>3.2</b></a></li> 2788 <li class="indline1"><tt>field-value</tt> <a class="iref" href="#rfc.iref.g.58"><b>3.2</b></a></li> 2789 <li class="indline1"><tt>general-header</tt> <a class="iref" href="#rfc.iref.g.61"><b>3.5</b></a></li> 2790 <li class="indline1"><tt>generic-message</tt> <a class="iref" href="#rfc.iref.g.54"><b>3.1</b></a></li> 2791 <li class="indline1"><tt>Host</tt> <a class="iref" href="#rfc.iref.g.79"><b>7.4</b></a></li> 2792 <li class="indline1"><tt>Host-v</tt> <a class="iref" href="#rfc.iref.g.80"><b>7.4</b></a></li> 2793 <li class="indline1"><tt>HTTP-date</tt> <a class="iref" href="#rfc.iref.g.25"><b>2.3.1</b></a></li> 2794 <li class="indline1"><tt>HTTP-message</tt> <a class="iref" href="#rfc.iref.g.53"><b>3.1</b></a></li> 2795 <li class="indline1"><tt>HTTP-Prot-Name</tt> <a class="iref" href="#rfc.iref.g.14"><b>2.1</b></a></li> 2796 <li class="indline1"><tt>http-URI</tt> <a class="iref" href="#rfc.iref.g.24"><b>2.2.1</b></a></li> 2797 <li class="indline1"><tt>HTTP-Version</tt> <a class="iref" href="#rfc.iref.g.13"><b>2.1</b></a></li> 2798 <li class="indline1"><tt>last-chunk</tt> <a class="iref" href="#rfc.iref.g.45"><b>2.4.1</b></a></li> 2799 <li class="indline1"><tt>message-body</tt> <a class="iref" href="#rfc.iref.g.60"><b>3.3</b></a></li> 2800 <li class="indline1"><tt>message-header</tt> <a class="iref" href="#rfc.iref.g.56"><b>3.2</b></a></li> 2801 <li class="indline1"><tt>Method</tt> <a class="iref" href="#rfc.iref.g.64"><b>4.1.1</b></a></li> 2802 <li class="indline1"><tt>month</tt> <a class="iref" href="#rfc.iref.g.36"><b>2.3.1</b></a></li> 2803 <li class="indline1"><tt>obsolete-date</tt> <a class="iref" href="#rfc.iref.g.27"><b>2.3.1</b></a></li> 2804 <li class="indline1"><tt>OWS</tt> <a class="iref" href="#rfc.iref.g.1"><b>1.2.2</b></a></li> 2805 <li class="indline1"><tt>parameter</tt> <a class="iref" href="#rfc.iref.g.39"><b>2.4</b></a></li> 2806 <li class="indline1"><tt>path-absolute</tt> <a class="iref" href="#rfc.iref.g.18"><b>2.2</b></a></li> 2807 <li class="indline1"><tt>port</tt> <a class="iref" href="#rfc.iref.g.19"><b>2.2</b></a></li> 2808 <li class="indline1"><tt>product</tt> <a class="iref" href="#rfc.iref.g.51"><b>2.5</b></a></li> 2809 <li class="indline1"><tt>product-version</tt> <a class="iref" href="#rfc.iref.g.52"><b>2.5</b></a></li> 2810 <li class="indline1"><tt>protocol-name</tt> <a class="iref" href="#rfc.iref.g.93"><b>7.9</b></a></li> 2811 <li class="indline1"><tt>protocol-version</tt> <a class="iref" href="#rfc.iref.g.94"><b>7.9</b></a></li> 2812 <li class="indline1"><tt>pseudonym</tt> <a class="iref" href="#rfc.iref.g.96"><b>7.9</b></a></li> 2813 <li class="indline1"><tt>qdtext</tt> <a class="iref" href="#rfc.iref.g.10"><b>1.2.2</b></a></li> 2814 <li class="indline1"><tt>query</tt> <a class="iref" href="#rfc.iref.g.20"><b>2.2</b></a></li> 2815 <li class="indline1"><tt>quoted-pair</tt> <a class="iref" href="#rfc.iref.g.12"><b>1.2.2</b></a></li> 2816 <li class="indline1"><tt>quoted-string</tt> <a class="iref" href="#rfc.iref.g.9"><b>1.2.2</b></a></li> 2817 <li class="indline1"><tt>quoted-text</tt> <a class="iref" href="#rfc.iref.g.11"><b>1.2.2</b></a></li> 2818 <li class="indline1"><tt>Reason-Phrase</tt> <a class="iref" href="#rfc.iref.g.71"><b>5.1.1</b></a></li> 2819 <li class="indline1"><tt>received-by</tt> <a class="iref" href="#rfc.iref.g.95"><b>7.9</b></a></li> 2820 <li class="indline1"><tt>received-protocol</tt> <a class="iref" href="#rfc.iref.g.92"><b>7.9</b></a></li> 2821 <li class="indline1"><tt>relative-part</tt> <a class="iref" href="#rfc.iref.g.23"><b>2.2</b></a></li> 2822 <li class="indline1"><tt>relativeURI</tt> <a class="iref" href="#rfc.iref.g.22"><b>2.2</b></a></li> 2823 <li class="indline1"><tt>Request</tt> <a class="iref" href="#rfc.iref.g.62"><b>4</b></a></li> 2824 <li class="indline1"><tt>Request-Line</tt> <a class="iref" href="#rfc.iref.g.63"><b>4.1</b></a></li> 2825 <li class="indline1"><tt>Request-URI</tt> <a class="iref" href="#rfc.iref.g.66"><b>4.1.2</b></a></li> 2826 <li class="indline1"><tt>Response</tt> <a class="iref" href="#rfc.iref.g.67"><b>5</b></a></li> 2827 <li class="indline1"><tt>rfc1123-date</tt> <a class="iref" href="#rfc.iref.g.26"><b>2.3.1</b></a></li> 2828 <li class="indline1"><tt>rfc850-date</tt> <a class="iref" href="#rfc.iref.g.28"><b>2.3.1</b></a></li> 2829 <li class="indline1"><tt>RWS</tt> <a class="iref" href="#rfc.iref.g.2"><b>1.2.2</b></a></li> 2830 <li class="indline1"><tt>start-line</tt> <a class="iref" href="#rfc.iref.g.55"><b>3.1</b></a></li> 2831 <li class="indline1"><tt>Status-Code</tt> <a class="iref" href="#rfc.iref.g.69"><b>5.1.1</b></a></li> 2832 <li class="indline1"><tt>Status-Line</tt> <a class="iref" href="#rfc.iref.g.68"><b>5.1</b></a></li> 2833 <li class="indline1"><tt>t-codings</tt> <a class="iref" href="#rfc.iref.g.83"><b>7.5</b></a></li> 2834 <li class="indline1"><tt>tchar</tt> <a class="iref" href="#rfc.iref.g.6"><b>1.2.2</b></a></li> 2835 <li class="indline1"><tt>TE</tt> <a class="iref" href="#rfc.iref.g.81"><b>7.5</b></a></li> 2836 <li class="indline1"><tt>TE-v</tt> <a class="iref" href="#rfc.iref.g.82"><b>7.5</b></a></li> 2837 <li class="indline1"><tt>TEXT</tt> <a class="iref" href="#rfc.iref.g.4"><b>1.2.2</b></a></li> 2838 <li class="indline1"><tt>time</tt> <a class="iref" href="#rfc.iref.g.33"><b>2.3.1</b></a></li> 2839 <li class="indline1"><tt>token</tt> <a class="iref" href="#rfc.iref.g.5"><b>1.2.2</b></a></li> 2840 <li class="indline1"><tt>Trailer</tt> <a class="iref" href="#rfc.iref.g.84"><b>7.6</b></a></li> 2841 <li class="indline1"><tt>trailer-part</tt> <a class="iref" href="#rfc.iref.g.50"><b>2.4.1</b></a></li> 2842 <li class="indline1"><tt>Trailer-v</tt> <a class="iref" href="#rfc.iref.g.85"><b>7.6</b></a></li> 2843 <li class="indline1"><tt>transfer-coding</tt> <a class="iref" href="#rfc.iref.g.37"><b>2.4</b></a></li> 2844 <li class="indline1"><tt>Transfer-Encoding</tt> <a class="iref" href="#rfc.iref.g.86"><b>7.7</b></a></li> 2845 <li class="indline1"><tt>Transfer-Encoding-v</tt> <a class="iref" href="#rfc.iref.g.87"><b>7.7</b></a></li> 2846 <li class="indline1"><tt>transfer-extension</tt> <a class="iref" href="#rfc.iref.g.38"><b>2.4</b></a></li> 2847 <li class="indline1"><tt>Upgrade</tt> <a class="iref" href="#rfc.iref.g.88"><b>7.8</b></a></li> 2848 <li class="indline1"><tt>Upgrade-v</tt> <a class="iref" href="#rfc.iref.g.89"><b>7.8</b></a></li> 2849 <li class="indline1"><tt>uri-host</tt> <a class="iref" href="#rfc.iref.g.21"><b>2.2</b></a></li> 2850 <li class="indline1"><tt>URI-reference</tt> <a class="iref" href="#rfc.iref.g.15"><b>2.2</b></a></li> 2851 <li class="indline1"><tt>value</tt> <a class="iref" href="#rfc.iref.g.41"><b>2.4</b></a></li> 2852 <li class="indline1"><tt>Via</tt> <a class="iref" href="#rfc.iref.g.90"><b>7.9</b></a></li> 2853 <li class="indline1"><tt>Via-v</tt> <a class="iref" href="#rfc.iref.g.91"><b>7.9</b></a></li> 2854 <li class="indline1"><tt>weekday</tt> <a class="iref" href="#rfc.iref.g.35"><b>2.3.1</b></a></li> 2855 <li class="indline1"><tt>wkday</tt> <a class="iref" href="#rfc.iref.g.34"><b>2.3.1</b></a></li> 2857 2856 </ul> 2858 2857 </li> … … 2862 2861 <li class="indline1">Headers 2863 2862 <ul class="ind"> 2864 <li class="indline1">Connection <a class="iref" href="#rfc.xref.header.connection.1"> 4.5</a>, <a class="iref" href="#rfc.xref.header.connection.2">7.1.2</a>, <a class="iref" href="#rfc.xref.header.connection.3">7.1.3</a>, <a class="iref" href="#rfc.iref.h.3"><b>8.1</b></a>, <a class="iref" href="#rfc.xref.header.connection.4">8.5</a>, <a class="iref" href="#rfc.xref.header.connection.5">8.8</a>, <a class="iref" href="#rfc.xref.header.connection.6">9.1</a>, <a class="iref" href="#rfc.xref.header.connection.7">B.2</a>, <a class="iref" href="#rfc.xref.header.connection.8">B.4</a></li>2865 <li class="indline1">Content-Length <a class="iref" href="#rfc.xref.header.content-length.1"> 4.4</a>, <a class="iref" href="#rfc.iref.h.4"><b>8.2</b></a>, <a class="iref" href="#rfc.xref.header.content-length.2">9.1</a>, <a class="iref" href="#rfc.xref.header.content-length.3">B.3</a></li>2866 <li class="indline1">Date <a class="iref" href="#rfc.xref.header.date.1"> 4.5</a>, <a class="iref" href="#rfc.iref.h.5"><b>8.3</b></a>, <a class="iref" href="#rfc.xref.header.date.2">9.1</a></li>2867 <li class="indline1">Host <a class="iref" href="#rfc.iref.h.7"><b> 8.4</b></a>, <a class="iref" href="#rfc.xref.header.host.1">9.1</a>, <a class="iref" href="#rfc.xref.header.host.2">B.1.1</a></li>2868 <li class="indline1">TE <a class="iref" href="#rfc.xref.header.te.1"> 3.4</a>, <a class="iref" href="#rfc.xref.header.te.2">3.4.1</a>, <a class="iref" href="#rfc.iref.h.8"><b>8.5</b></a>, <a class="iref" href="#rfc.xref.header.te.3">9.1</a>, <a class="iref" href="#rfc.xref.header.te.4">B.3</a></li>2869 <li class="indline1">Trailer <a class="iref" href="#rfc.xref.header.trailer.1"> 3.4.1</a>, <a class="iref" href="#rfc.xref.header.trailer.2">4.5</a>, <a class="iref" href="#rfc.iref.h.9"><b>8.6</b></a>, <a class="iref" href="#rfc.xref.header.trailer.3">9.1</a></li>2870 <li class="indline1">Transfer-Encoding <a class="iref" href="#rfc.xref.header.transfer-encoding.1"> 3.4</a>, <a class="iref" href="#rfc.xref.header.transfer-encoding.2">4.3</a>, <a class="iref" href="#rfc.xref.header.transfer-encoding.3">4.4</a>, <a class="iref" href="#rfc.xref.header.transfer-encoding.4">4.5</a>, <a class="iref" href="#rfc.iref.h.10"><b>8.7</b></a>, <a class="iref" href="#rfc.xref.header.transfer-encoding.5">9.1</a></li>2871 <li class="indline1">Upgrade <a class="iref" href="#rfc.xref.header.upgrade.1"> 4.5</a>, <a class="iref" href="#rfc.iref.h.11"><b>8.8</b></a>, <a class="iref" href="#rfc.xref.header.upgrade.2">9.1</a></li>2872 <li class="indline1">Via <a class="iref" href="#rfc.xref.header.via.1"> 4.5</a>, <a class="iref" href="#rfc.iref.h.12"><b>8.9</b></a>, <a class="iref" href="#rfc.xref.header.via.2">9.1</a></li>2863 <li class="indline1">Connection <a class="iref" href="#rfc.xref.header.connection.1">3.5</a>, <a class="iref" href="#rfc.xref.header.connection.2">6.1.2</a>, <a class="iref" href="#rfc.xref.header.connection.3">6.1.3</a>, <a class="iref" href="#rfc.iref.h.3"><b>7.1</b></a>, <a class="iref" href="#rfc.xref.header.connection.4">7.5</a>, <a class="iref" href="#rfc.xref.header.connection.5">7.8</a>, <a class="iref" href="#rfc.xref.header.connection.6">8.1</a>, <a class="iref" href="#rfc.xref.header.connection.7">B.2</a>, <a class="iref" href="#rfc.xref.header.connection.8">B.4</a></li> 2864 <li class="indline1">Content-Length <a class="iref" href="#rfc.xref.header.content-length.1">3.4</a>, <a class="iref" href="#rfc.iref.h.4"><b>7.2</b></a>, <a class="iref" href="#rfc.xref.header.content-length.2">8.1</a>, <a class="iref" href="#rfc.xref.header.content-length.3">B.3</a></li> 2865 <li class="indline1">Date <a class="iref" href="#rfc.xref.header.date.1">3.5</a>, <a class="iref" href="#rfc.iref.h.5"><b>7.3</b></a>, <a class="iref" href="#rfc.xref.header.date.2">8.1</a></li> 2866 <li class="indline1">Host <a class="iref" href="#rfc.iref.h.7"><b>7.4</b></a>, <a class="iref" href="#rfc.xref.header.host.1">8.1</a>, <a class="iref" href="#rfc.xref.header.host.2">B.1.1</a></li> 2867 <li class="indline1">TE <a class="iref" href="#rfc.xref.header.te.1">2.4</a>, <a class="iref" href="#rfc.xref.header.te.2">2.4.1</a>, <a class="iref" href="#rfc.iref.h.8"><b>7.5</b></a>, <a class="iref" href="#rfc.xref.header.te.3">8.1</a>, <a class="iref" href="#rfc.xref.header.te.4">B.3</a></li> 2868 <li class="indline1">Trailer <a class="iref" href="#rfc.xref.header.trailer.1">2.4.1</a>, <a class="iref" href="#rfc.xref.header.trailer.2">3.5</a>, <a class="iref" href="#rfc.iref.h.9"><b>7.6</b></a>, <a class="iref" href="#rfc.xref.header.trailer.3">8.1</a></li> 2869 <li class="indline1">Transfer-Encoding <a class="iref" href="#rfc.xref.header.transfer-encoding.1">2.4</a>, <a class="iref" href="#rfc.xref.header.transfer-encoding.2">3.3</a>, <a class="iref" href="#rfc.xref.header.transfer-encoding.3">3.4</a>, <a class="iref" href="#rfc.xref.header.transfer-encoding.4">3.5</a>, <a class="iref" href="#rfc.iref.h.10"><b>7.7</b></a>, <a class="iref" href="#rfc.xref.header.transfer-encoding.5">8.1</a></li> 2870 <li class="indline1">Upgrade <a class="iref" href="#rfc.xref.header.upgrade.1">3.5</a>, <a class="iref" href="#rfc.iref.h.11"><b>7.8</b></a>, <a class="iref" href="#rfc.xref.header.upgrade.2">8.1</a></li> 2871 <li class="indline1">Via <a class="iref" href="#rfc.xref.header.via.1">3.5</a>, <a class="iref" href="#rfc.iref.h.12"><b>7.9</b></a>, <a class="iref" href="#rfc.xref.header.via.2">8.1</a></li> 2873 2872 </ul> 2874 2873 </li> 2875 <li class="indline1">Host header <a class="iref" href="#rfc.iref.h.6"><b> 8.4</b></a>, <a class="iref" href="#rfc.xref.header.host.1">9.1</a>, <a class="iref" href="#rfc.xref.header.host.2">B.1.1</a></li>2876 <li class="indline1">http URI scheme <a class="iref" href="#rfc.iref.h.1"><b> 3.2.1</b></a></li>2877 <li class="indline1">https URI scheme <a class="iref" href="#rfc.iref.h.2"> 3.2.1</a></li>2874 <li class="indline1">Host header <a class="iref" href="#rfc.iref.h.6"><b>7.4</b></a>, <a class="iref" href="#rfc.xref.header.host.1">8.1</a>, <a class="iref" href="#rfc.xref.header.host.2">B.1.1</a></li> 2875 <li class="indline1">http URI scheme <a class="iref" href="#rfc.iref.h.1"><b>2.2.1</b></a></li> 2876 <li class="indline1">https URI scheme <a class="iref" href="#rfc.iref.h.2">2.2.1</a></li> 2878 2877 </ul> 2879 2878 </li> 2880 2879 <li class="indline0"><a id="rfc.index.I" href="#rfc.index.I"><b>I</b></a><ul class="ind"> 2881 2880 <li class="indline1">inbound <a class="iref" href="#rfc.iref.i.1">C</a></li> 2882 <li class="indline1"><em>ISO-8859-1</em> <a class="iref" href="#rfc.xref.ISO-8859-1.1"> 2.2</a>, <a class="iref" href="#ISO-8859-1"><b>12.1</b></a></li>2881 <li class="indline1"><em>ISO-8859-1</em> <a class="iref" href="#rfc.xref.ISO-8859-1.1">1.2.2</a>, <a class="iref" href="#ISO-8859-1"><b>11.1</b></a></li> 2883 2882 </ul> 2884 2883 </li> 2885 2884 <li class="indline0"><a id="rfc.index.K" href="#rfc.index.K"><b>K</b></a><ul class="ind"> 2886 <li class="indline1"><em>Kri2001</em> <a class="iref" href="#rfc.xref.Kri2001.1"> 4.2</a>, <a class="iref" href="#Kri2001"><b>12.2</b></a></li>2885 <li class="indline1"><em>Kri2001</em> <a class="iref" href="#rfc.xref.Kri2001.1">3.2</a>, <a class="iref" href="#Kri2001"><b>11.2</b></a></li> 2887 2886 </ul> 2888 2887 </li> … … 2890 2889 <li class="indline1">Media Type 2891 2890 <ul class="ind"> 2892 <li class="indline1">application/http <a class="iref" href="#rfc.iref.m.3"><b> 9.3.2</b></a></li>2893 <li class="indline1">message/http <a class="iref" href="#rfc.iref.m.1"><b> 9.3.1</b></a></li>2891 <li class="indline1">application/http <a class="iref" href="#rfc.iref.m.3"><b>8.3.2</b></a></li> 2892 <li class="indline1">message/http <a class="iref" href="#rfc.iref.m.1"><b>8.3.1</b></a></li> 2894 2893 </ul> 2895 2894 </li> 2896 2895 <li class="indline1">message <a class="iref" href="#rfc.iref.m.4">C</a></li> 2897 <li class="indline1">message/http Media Type <a class="iref" href="#rfc.iref.m.2"><b> 9.3.1</b></a></li>2896 <li class="indline1">message/http Media Type <a class="iref" href="#rfc.iref.m.2"><b>8.3.1</b></a></li> 2898 2897 </ul> 2899 2898 </li> 2900 2899 <li class="indline0"><a id="rfc.index.N" href="#rfc.index.N"><b>N</b></a><ul class="ind"> 2901 <li class="indline1"><em>Nie1997</em> <a class="iref" href="#rfc.xref.Nie1997.1"> 7.1.1</a>, <a class="iref" href="#Nie1997"><b>12.2</b></a>, <a class="iref" href="#rfc.xref.Nie1997.2">B.3</a></li>2900 <li class="indline1"><em>Nie1997</em> <a class="iref" href="#rfc.xref.Nie1997.1">6.1.1</a>, <a class="iref" href="#Nie1997"><b>11.2</b></a>, <a class="iref" href="#rfc.xref.Nie1997.2">B.3</a></li> 2902 2901 </ul> 2903 2902 </li> … … 2908 2907 </li> 2909 2908 <li class="indline0"><a id="rfc.index.P" href="#rfc.index.P"><b>P</b></a><ul class="ind"> 2910 <li class="indline1"><em>Pad1995</em> <a class="iref" href="#rfc.xref.Pad1995.1"> 7.1.1</a>, <a class="iref" href="#Pad1995"><b>12.2</b></a></li>2911 <li class="indline1"><em>Part2</em> <a class="iref" href="#rfc.xref.Part2.1"> 2.3</a>, <a class="iref" href="#rfc.xref.Part2.2">2.3</a>, <a class="iref" href="#rfc.xref.Part2.3">3.2</a>, <a class="iref" href="#rfc.xref.Part2.4">4.2</a>, <a class="iref" href="#rfc.xref.Part2.5">4.2</a>, <a class="iref" href="#rfc.xref.Part2.6">4.3</a>, <a class="iref" href="#rfc.xref.Part2.7">5</a>, <a class="iref" href="#rfc.xref.Part2.8">5.1.2</a>, <a class="iref" href="#rfc.xref.Part2.9">6</a>, <a class="iref" href="#rfc.xref.Part2.10">6.1.1</a>, <a class="iref" href="#rfc.xref.Part2.11">7.1.2.2</a>, <a class="iref" href="#rfc.xref.Part2.12">7.1.4</a>, <a class="iref" href="#rfc.xref.Part2.13">7.2.3</a>, <a class="iref" href="#rfc.xref.Part2.14">7.2.3</a>, <a class="iref" href="#rfc.xref.Part2.15">7.2.3</a>, <a class="iref" href="#rfc.xref.Part2.16">7.2.3</a>, <a class="iref" href="#Part2"><b>12.1</b></a><ul class="ind">2912 <li class="indline1"><em>Section 3</em> <a class="iref" href="#rfc.xref.Part2.6"> 4.3</a></li>2913 <li class="indline1"><em>Section 4</em> <a class="iref" href="#rfc.xref.Part2.1"> 2.3</a>, <a class="iref" href="#rfc.xref.Part2.4">4.2</a>, <a class="iref" href="#rfc.xref.Part2.7">5</a></li>2914 <li class="indline1"><em>Section 6</em> <a class="iref" href="#rfc.xref.Part2.2"> 2.3</a>, <a class="iref" href="#rfc.xref.Part2.5">4.2</a>, <a class="iref" href="#rfc.xref.Part2.9">6</a></li>2915 <li class="indline1"><em>Section 8.1.2</em> <a class="iref" href="#rfc.xref.Part2.11"> 7.1.2.2</a>, <a class="iref" href="#rfc.xref.Part2.12">7.1.4</a></li>2916 <li class="indline1"><em>Section 8.9</em> <a class="iref" href="#rfc.xref.Part2.8"> 5.1.2</a></li>2917 <li class="indline1"><em>Section 9</em> <a class="iref" href="#rfc.xref.Part2.10"> 6.1.1</a></li>2918 <li class="indline1"><em>Section 9.1.1</em> <a class="iref" href="#rfc.xref.Part2.13"> 7.2.3</a></li>2919 <li class="indline1"><em>Section 9.1</em> <a class="iref" href="#rfc.xref.Part2.16"> 7.2.3</a></li>2920 <li class="indline1"><em>Section 9.4.15</em> <a class="iref" href="#rfc.xref.Part2.3"> 3.2</a></li>2921 <li class="indline1"><em>Section 10.2</em> <a class="iref" href="#rfc.xref.Part2.14"> 7.2.3</a>, <a class="iref" href="#rfc.xref.Part2.15">7.2.3</a></li>2909 <li class="indline1"><em>Pad1995</em> <a class="iref" href="#rfc.xref.Pad1995.1">6.1.1</a>, <a class="iref" href="#Pad1995"><b>11.2</b></a></li> 2910 <li class="indline1"><em>Part2</em> <a class="iref" href="#rfc.xref.Part2.1">1.2.3</a>, <a class="iref" href="#rfc.xref.Part2.2">1.2.3</a>, <a class="iref" href="#rfc.xref.Part2.3">2.2</a>, <a class="iref" href="#rfc.xref.Part2.4">3.2</a>, <a class="iref" href="#rfc.xref.Part2.5">3.2</a>, <a class="iref" href="#rfc.xref.Part2.6">3.3</a>, <a class="iref" href="#rfc.xref.Part2.7">4</a>, <a class="iref" href="#rfc.xref.Part2.8">4.1.2</a>, <a class="iref" href="#rfc.xref.Part2.9">5</a>, <a class="iref" href="#rfc.xref.Part2.10">5.1.1</a>, <a class="iref" href="#rfc.xref.Part2.11">6.1.2.2</a>, <a class="iref" href="#rfc.xref.Part2.12">6.1.4</a>, <a class="iref" href="#rfc.xref.Part2.13">6.2.3</a>, <a class="iref" href="#rfc.xref.Part2.14">6.2.3</a>, <a class="iref" href="#rfc.xref.Part2.15">6.2.3</a>, <a class="iref" href="#rfc.xref.Part2.16">6.2.3</a>, <a class="iref" href="#Part2"><b>11.1</b></a><ul class="ind"> 2911 <li class="indline1"><em>Section 3</em> <a class="iref" href="#rfc.xref.Part2.6">3.3</a></li> 2912 <li class="indline1"><em>Section 4</em> <a class="iref" href="#rfc.xref.Part2.1">1.2.3</a>, <a class="iref" href="#rfc.xref.Part2.4">3.2</a>, <a class="iref" href="#rfc.xref.Part2.7">4</a></li> 2913 <li class="indline1"><em>Section 6</em> <a class="iref" href="#rfc.xref.Part2.2">1.2.3</a>, <a class="iref" href="#rfc.xref.Part2.5">3.2</a>, <a class="iref" href="#rfc.xref.Part2.9">5</a></li> 2914 <li class="indline1"><em>Section 8.1.2</em> <a class="iref" href="#rfc.xref.Part2.11">6.1.2.2</a>, <a class="iref" href="#rfc.xref.Part2.12">6.1.4</a></li> 2915 <li class="indline1"><em>Section 8.9</em> <a class="iref" href="#rfc.xref.Part2.8">4.1.2</a></li> 2916 <li class="indline1"><em>Section 9</em> <a class="iref" href="#rfc.xref.Part2.10">5.1.1</a></li> 2917 <li class="indline1"><em>Section 9.1.1</em> <a class="iref" href="#rfc.xref.Part2.13">6.2.3</a></li> 2918 <li class="indline1"><em>Section 9.1</em> <a class="iref" href="#rfc.xref.Part2.16">6.2.3</a></li> 2919 <li class="indline1"><em>Section 9.4.15</em> <a class="iref" href="#rfc.xref.Part2.3">2.2</a></li> 2920 <li class="indline1"><em>Section 10.2</em> <a class="iref" href="#rfc.xref.Part2.14">6.2.3</a>, <a class="iref" href="#rfc.xref.Part2.15">6.2.3</a></li> 2922 2921 </ul> 2923 2922 </li> 2924 <li class="indline1"><em>Part3</em> <a class="iref" href="#rfc.xref.Part3.1">1</a>, <a class="iref" href="#rfc.xref.Part3.2">1.2 </a>, <a class="iref" href="#rfc.xref.Part3.3">2.2</a>, <a class="iref" href="#rfc.xref.Part3.4">2.3</a>, <a class="iref" href="#rfc.xref.Part3.5">2.3</a>, <a class="iref" href="#rfc.xref.Part3.6">2.3</a>, <a class="iref" href="#rfc.xref.Part3.7">3.4</a>, <a class="iref" href="#rfc.xref.Part3.8">3.4</a>, <a class="iref" href="#rfc.xref.Part3.9">4.2</a>, <a class="iref" href="#rfc.xref.Part3.10">5</a>, <a class="iref" href="#rfc.xref.Part3.11">6</a>, <a class="iref" href="#rfc.xref.Part3.12">8.5</a>, <a class="iref" href="#Part3"><b>12.1</b></a>, <a class="iref" href="#rfc.xref.Part3.13">A</a>, <a class="iref" href="#rfc.xref.Part3.14">B.3</a>, <a class="iref" href="#rfc.xref.Part3.15">C</a>, <a class="iref" href="#rfc.xref.Part3.16">C</a>, <a class="iref" href="#rfc.xref.Part3.17">C</a><ul class="ind">2925 <li class="indline1"><em>Section 3.2</em> <a class="iref" href="#rfc.xref.Part3.7"> 3.4</a>, <a class="iref" href="#rfc.xref.Part3.8">3.4</a></li>2926 <li class="indline1"><em>Section 3.3</em> <a class="iref" href="#rfc.xref.Part3. 3">2.2</a></li>2927 <li class="indline1"><em>Section 3.4</em> <a class="iref" href="#rfc.xref.Part3.12"> 8.5</a></li>2928 <li class="indline1"><em>Section 4.1</em> <a class="iref" href="#rfc.xref.Part3. 6">2.3</a>, <a class="iref" href="#rfc.xref.Part3.9">4.2</a>, <a class="iref" href="#rfc.xref.Part3.10">5</a>, <a class="iref" href="#rfc.xref.Part3.11">6</a></li>2923 <li class="indline1"><em>Part3</em> <a class="iref" href="#rfc.xref.Part3.1">1</a>, <a class="iref" href="#rfc.xref.Part3.2">1.2.2</a>, <a class="iref" href="#rfc.xref.Part3.3">1.2.3</a>, <a class="iref" href="#rfc.xref.Part3.4">1.2.3</a>, <a class="iref" href="#rfc.xref.Part3.5">1.2.3</a>, <a class="iref" href="#rfc.xref.Part3.6">1.3</a>, <a class="iref" href="#rfc.xref.Part3.7">2.4</a>, <a class="iref" href="#rfc.xref.Part3.8">2.4</a>, <a class="iref" href="#rfc.xref.Part3.9">3.2</a>, <a class="iref" href="#rfc.xref.Part3.10">4</a>, <a class="iref" href="#rfc.xref.Part3.11">5</a>, <a class="iref" href="#rfc.xref.Part3.12">7.5</a>, <a class="iref" href="#Part3"><b>11.1</b></a>, <a class="iref" href="#rfc.xref.Part3.13">A</a>, <a class="iref" href="#rfc.xref.Part3.14">B.3</a>, <a class="iref" href="#rfc.xref.Part3.15">C</a>, <a class="iref" href="#rfc.xref.Part3.16">C</a>, <a class="iref" href="#rfc.xref.Part3.17">C</a><ul class="ind"> 2924 <li class="indline1"><em>Section 3.2</em> <a class="iref" href="#rfc.xref.Part3.7">2.4</a>, <a class="iref" href="#rfc.xref.Part3.8">2.4</a></li> 2925 <li class="indline1"><em>Section 3.3</em> <a class="iref" href="#rfc.xref.Part3.2">1.2.2</a></li> 2926 <li class="indline1"><em>Section 3.4</em> <a class="iref" href="#rfc.xref.Part3.12">7.5</a></li> 2927 <li class="indline1"><em>Section 4.1</em> <a class="iref" href="#rfc.xref.Part3.5">1.2.3</a>, <a class="iref" href="#rfc.xref.Part3.9">3.2</a>, <a class="iref" href="#rfc.xref.Part3.10">4</a>, <a class="iref" href="#rfc.xref.Part3.11">5</a></li> 2929 2928 <li class="indline1"><em>Section 4</em> <a class="iref" href="#rfc.xref.Part3.15">C</a></li> 2930 <li class="indline1"><em>Section 4.2</em> <a class="iref" href="#rfc.xref.Part3. 5">2.3</a></li>2929 <li class="indline1"><em>Section 4.2</em> <a class="iref" href="#rfc.xref.Part3.4">1.2.3</a></li> 2931 2930 <li class="indline1"><em>Section 5</em> <a class="iref" href="#rfc.xref.Part3.16">C</a>, <a class="iref" href="#rfc.xref.Part3.17">C</a></li> 2932 <li class="indline1"><em>Section 6.1</em> <a class="iref" href="#rfc.xref.Part3. 4">2.3</a></li>2933 <li class="indline1"><em>Appendix A</em> <a class="iref" href="#rfc.xref.Part3.1">1</a>, <a class="iref" href="#rfc.xref.Part3. 2">1.2</a></li>2931 <li class="indline1"><em>Section 6.1</em> <a class="iref" href="#rfc.xref.Part3.3">1.2.3</a></li> 2932 <li class="indline1"><em>Appendix A</em> <a class="iref" href="#rfc.xref.Part3.1">1</a>, <a class="iref" href="#rfc.xref.Part3.6">1.3</a></li> 2934 2933 </ul> 2935 2934 </li> 2936 <li class="indline1"><em>Part5</em> <a class="iref" href="#Part5"><b>1 2.1</b></a>, <a class="iref" href="#rfc.xref.Part5.1">B.3</a></li>2937 <li class="indline1"><em>Part6</em> <a class="iref" href="#rfc.xref.Part6.1">1.2 </a>, <a class="iref" href="#rfc.xref.Part6.2">2.3</a>, <a class="iref" href="#rfc.xref.Part6.3">2.3</a>, <a class="iref" href="#rfc.xref.Part6.4">2.3</a>, <a class="iref" href="#rfc.xref.Part6.5">4.5</a>, <a class="iref" href="#rfc.xref.Part6.6">4.5</a>, <a class="iref" href="#rfc.xref.Part6.7">4.5</a>, <a class="iref" href="#Part6"><b>12.1</b></a>, <a class="iref" href="#rfc.xref.Part6.8">B.3</a>, <a class="iref" href="#rfc.xref.Part6.9">C</a><ul class="ind">2938 <li class="indline1"><em>Section 1</em> <a class="iref" href="#rfc.xref.Part6. 1">1.2</a>, <a class="iref" href="#rfc.xref.Part6.9">C</a></li>2939 <li class="indline1"><em>Section 16.2</em> <a class="iref" href="#rfc.xref.Part6.5"> 4.5</a></li>2940 <li class="indline1"><em>Section 16.4</em> <a class="iref" href="#rfc.xref.Part6. 2">2.3</a>, <a class="iref" href="#rfc.xref.Part6.3">2.3</a>, <a class="iref" href="#rfc.xref.Part6.6">4.5</a></li>2941 <li class="indline1"><em>Section 16.6</em> <a class="iref" href="#rfc.xref.Part6. 4">2.3</a>, <a class="iref" href="#rfc.xref.Part6.7">4.5</a></li>2935 <li class="indline1"><em>Part5</em> <a class="iref" href="#Part5"><b>11.1</b></a>, <a class="iref" href="#rfc.xref.Part5.1">B.3</a></li> 2936 <li class="indline1"><em>Part6</em> <a class="iref" href="#rfc.xref.Part6.1">1.2.3</a>, <a class="iref" href="#rfc.xref.Part6.2">1.2.3</a>, <a class="iref" href="#rfc.xref.Part6.3">1.2.3</a>, <a class="iref" href="#rfc.xref.Part6.4">1.3</a>, <a class="iref" href="#rfc.xref.Part6.5">3.5</a>, <a class="iref" href="#rfc.xref.Part6.6">3.5</a>, <a class="iref" href="#rfc.xref.Part6.7">3.5</a>, <a class="iref" href="#Part6"><b>11.1</b></a>, <a class="iref" href="#rfc.xref.Part6.8">B.3</a>, <a class="iref" href="#rfc.xref.Part6.9">C</a><ul class="ind"> 2937 <li class="indline1"><em>Section 1</em> <a class="iref" href="#rfc.xref.Part6.4">1.3</a>, <a class="iref" href="#rfc.xref.Part6.9">C</a></li> 2938 <li class="indline1"><em>Section 16.2</em> <a class="iref" href="#rfc.xref.Part6.5">3.5</a></li> 2939 <li class="indline1"><em>Section 16.4</em> <a class="iref" href="#rfc.xref.Part6.1">1.2.3</a>, <a class="iref" href="#rfc.xref.Part6.2">1.2.3</a>, <a class="iref" href="#rfc.xref.Part6.6">3.5</a></li> 2940 <li class="indline1"><em>Section 16.6</em> <a class="iref" href="#rfc.xref.Part6.3">1.2.3</a>, <a class="iref" href="#rfc.xref.Part6.7">3.5</a></li> 2942 2941 </ul> 2943 2942 </li> … … 2950 2949 <li class="indline1">resource <a class="iref" href="#rfc.iref.r.3">C</a></li> 2951 2950 <li class="indline1">response <a class="iref" href="#rfc.iref.r.2">C</a></li> 2952 <li class="indline1"><em>RFC1123</em> <a class="iref" href="#rfc.xref.RFC1123.1"> 3.3.1</a>, <a class="iref" href="#RFC1123"><b>12.2</b></a></li>2953 <li class="indline1"><em>RFC1305</em> <a class="iref" href="#rfc.xref.RFC1305.1"> 8.3</a>, <a class="iref" href="#RFC1305"><b>12.2</b></a></li>2954 <li class="indline1"><em>RFC1436</em> <a class="iref" href="#rfc.xref.RFC1436.1">1</a>, <a class="iref" href="#RFC1436"><b>1 2.2</b></a></li>2955 <li class="indline1"><em>RFC1900</em> <a class="iref" href="#rfc.xref.RFC1900.1"> 3.2.1</a>, <a class="iref" href="#rfc.xref.RFC1900.2">10.4</a>, <a class="iref" href="#RFC1900"><b>12.2</b></a></li>2956 <li class="indline1"><em>RFC1945</em> <a class="iref" href="#RFC1945"><b>1 2.2</b></a>, <a class="iref" href="#rfc.xref.RFC1945.1">B</a></li>2957 <li class="indline1"><em>RFC2045</em> <a class="iref" href="#rfc.xref.RFC2045.1">1</a>, <a class="iref" href="#rfc.xref.RFC2045.2"> 3.4</a>, <a class="iref" href="#rfc.xref.RFC2045.3">11</a>, <a class="iref" href="#RFC2045"><b>12.1</b></a></li>2958 <li class="indline1"><em>RFC2047</em> <a class="iref" href="#rfc.xref.RFC2047.1"> 2.2</a>, <a class="iref" href="#RFC2047"><b>12.1</b></a></li>2959 <li class="indline1"><em>RFC2068</em> <a class="iref" href="#rfc.xref.RFC2068.1"> 3.1</a>, <a class="iref" href="#rfc.xref.RFC2068.2">7.1.1</a>, <a class="iref" href="#rfc.xref.RFC2068.3">7.1.3</a>, <a class="iref" href="#rfc.xref.RFC2068.4">7.2.3</a>, <a class="iref" href="#rfc.xref.RFC2068.5">11</a>, <a class="iref" href="#RFC2068"><b>12.2</b></a>, <a class="iref" href="#rfc.xref.RFC2068.6">B</a>, <a class="iref" href="#rfc.xref.RFC2068.7">B.2</a><ul class="ind">2951 <li class="indline1"><em>RFC1123</em> <a class="iref" href="#rfc.xref.RFC1123.1">2.3.1</a>, <a class="iref" href="#RFC1123"><b>11.2</b></a></li> 2952 <li class="indline1"><em>RFC1305</em> <a class="iref" href="#rfc.xref.RFC1305.1">7.3</a>, <a class="iref" href="#RFC1305"><b>11.2</b></a></li> 2953 <li class="indline1"><em>RFC1436</em> <a class="iref" href="#rfc.xref.RFC1436.1">1</a>, <a class="iref" href="#RFC1436"><b>11.2</b></a></li> 2954 <li class="indline1"><em>RFC1900</em> <a class="iref" href="#rfc.xref.RFC1900.1">2.2.1</a>, <a class="iref" href="#rfc.xref.RFC1900.2">9.4</a>, <a class="iref" href="#RFC1900"><b>11.2</b></a></li> 2955 <li class="indline1"><em>RFC1945</em> <a class="iref" href="#RFC1945"><b>11.2</b></a>, <a class="iref" href="#rfc.xref.RFC1945.1">B</a></li> 2956 <li class="indline1"><em>RFC2045</em> <a class="iref" href="#rfc.xref.RFC2045.1">1</a>, <a class="iref" href="#rfc.xref.RFC2045.2">2.4</a>, <a class="iref" href="#rfc.xref.RFC2045.3">10</a>, <a class="iref" href="#RFC2045"><b>11.1</b></a></li> 2957 <li class="indline1"><em>RFC2047</em> <a class="iref" href="#rfc.xref.RFC2047.1">1.2.2</a>, <a class="iref" href="#RFC2047"><b>11.1</b></a></li> 2958 <li class="indline1"><em>RFC2068</em> <a class="iref" href="#rfc.xref.RFC2068.1">2.1</a>, <a class="iref" href="#rfc.xref.RFC2068.2">6.1.1</a>, <a class="iref" href="#rfc.xref.RFC2068.3">6.1.3</a>, <a class="iref" href="#rfc.xref.RFC2068.4">6.2.3</a>, <a class="iref" href="#rfc.xref.RFC2068.5">10</a>, <a class="iref" href="#RFC2068"><b>11.2</b></a>, <a class="iref" href="#rfc.xref.RFC2068.6">B</a>, <a class="iref" href="#rfc.xref.RFC2068.7">B.2</a><ul class="ind"> 2960 2959 <li class="indline1"><em>Section 19.7.1</em> <a class="iref" href="#rfc.xref.RFC2068.6">B</a></li> 2961 2960 </ul> 2962 2961 </li> 2963 <li class="indline1"><em>RFC2109</em> <a class="iref" href="#rfc.xref.RFC2109.1"> 4.2</a>, <a class="iref" href="#RFC2109"><b>12.2</b></a></li>2964 <li class="indline1"><em>RFC2119</em> <a class="iref" href="#rfc.xref.RFC2119.1">1.1</a>, <a class="iref" href="#RFC2119"><b>1 2.1</b></a>, <a class="iref" href="#rfc.xref.RFC2119.2">B.3</a></li>2965 <li class="indline1"><em>RFC2145</em> <a class="iref" href="#rfc.xref.RFC2145.1"> 3.1</a>, <a class="iref" href="#rfc.xref.RFC2145.2">3.1</a>, <a class="iref" href="#RFC2145"><b>12.2</b></a>, <a class="iref" href="#rfc.xref.RFC2145.3">B.3</a></li>2966 <li class="indline1"><em>RFC2616</em> <a class="iref" href="#rfc.xref.RFC2616.1">1</a>, <a class="iref" href="#rfc.xref.RFC2616.2">1 1</a>, <a class="iref" href="#RFC2616"><b>12.2</b></a>, <a class="iref" href="#rfc.xref.RFC2616.3">D.1</a></li>2967 <li class="indline1"><em>RFC2818</em> <a class="iref" href="#rfc.xref.RFC2818.1"> 3.2.1</a>, <a class="iref" href="#RFC2818"><b>12.2</b></a></li>2968 <li class="indline1"><em>RFC2965</em> <a class="iref" href="#rfc.xref.RFC2965.1"> 4.2</a>, <a class="iref" href="#RFC2965"><b>12.2</b></a></li>2969 <li class="indline1"><em>RFC3864</em> <a class="iref" href="#rfc.xref.RFC3864.1"> 9.1</a>, <a class="iref" href="#RFC3864"><b>12.2</b></a></li>2970 <li class="indline1"><em>RFC3977</em> <a class="iref" href="#rfc.xref.RFC3977.1">1</a>, <a class="iref" href="#RFC3977"><b>1 2.2</b></a></li>2971 <li class="indline1"><em>RFC3986</em> <a class="iref" href="#rfc.xref.RFC3986.1">1</a>, <a class="iref" href="#rfc.xref.RFC3986.2"> 3.2</a>, <a class="iref" href="#rfc.xref.RFC3986.3">3.2</a>, <a class="iref" href="#rfc.xref.RFC3986.4">3.2</a>, <a class="iref" href="#rfc.xref.RFC3986.5">3.2</a>, <a class="iref" href="#rfc.xref.RFC3986.6">3.2</a>, <a class="iref" href="#rfc.xref.RFC3986.7">3.2</a>, <a class="iref" href="#rfc.xref.RFC3986.8">3.2</a>, <a class="iref" href="#rfc.xref.RFC3986.9">3.2</a>, <a class="iref" href="#rfc.xref.RFC3986.10">3.2</a>, <a class="iref" href="#rfc.xref.RFC3986.11">3.2</a>, <a class="iref" href="#rfc.xref.RFC3986.12">3.2</a>, <a class="iref" href="#rfc.xref.RFC3986.13">3.2.2</a>, <a class="iref" href="#rfc.xref.RFC3986.14">5.1.2</a>, <a class="iref" href="#RFC3986"><b>12.1</b></a><ul class="ind">2972 <li class="indline1"><em>Section 2.2</em> <a class="iref" href="#rfc.xref.RFC3986.13"> 3.2.2</a></li>2973 <li class="indline1"><em>Section 2.4</em> <a class="iref" href="#rfc.xref.RFC3986.14"> 5.1.2</a></li>2974 <li class="indline1"><em>Section 3.2.3</em> <a class="iref" href="#rfc.xref.RFC3986.9"> 3.2</a></li>2975 <li class="indline1"><em>Section 3.2.2</em> <a class="iref" href="#rfc.xref.RFC3986.11"> 3.2</a></li>2976 <li class="indline1"><em>Section 3.2</em> <a class="iref" href="#rfc.xref.RFC3986.5"> 3.2</a></li>2977 <li class="indline1"><em>Section 3.3</em> <a class="iref" href="#rfc.xref.RFC3986.7"> 3.2</a>, <a class="iref" href="#rfc.xref.RFC3986.8">3.2</a></li>2978 <li class="indline1"><em>Section 3.4</em> <a class="iref" href="#rfc.xref.RFC3986.10"> 3.2</a></li>2979 <li class="indline1"><em>Section 3.5</em> <a class="iref" href="#rfc.xref.RFC3986.6"> 3.2</a></li>2980 <li class="indline1"><em>Section 4.2</em> <a class="iref" href="#rfc.xref.RFC3986.12"> 3.2</a></li>2981 <li class="indline1"><em>Section 4.3</em> <a class="iref" href="#rfc.xref.RFC3986.4"> 3.2</a></li>2962 <li class="indline1"><em>RFC2109</em> <a class="iref" href="#rfc.xref.RFC2109.1">3.2</a>, <a class="iref" href="#RFC2109"><b>11.2</b></a></li> 2963 <li class="indline1"><em>RFC2119</em> <a class="iref" href="#rfc.xref.RFC2119.1">1.1</a>, <a class="iref" href="#RFC2119"><b>11.1</b></a>, <a class="iref" href="#rfc.xref.RFC2119.2">B.3</a></li> 2964 <li class="indline1"><em>RFC2145</em> <a class="iref" href="#rfc.xref.RFC2145.1">2.1</a>, <a class="iref" href="#rfc.xref.RFC2145.2">2.1</a>, <a class="iref" href="#RFC2145"><b>11.2</b></a>, <a class="iref" href="#rfc.xref.RFC2145.3">B.3</a></li> 2965 <li class="indline1"><em>RFC2616</em> <a class="iref" href="#rfc.xref.RFC2616.1">1</a>, <a class="iref" href="#rfc.xref.RFC2616.2">10</a>, <a class="iref" href="#RFC2616"><b>11.2</b></a>, <a class="iref" href="#rfc.xref.RFC2616.3">D.1</a></li> 2966 <li class="indline1"><em>RFC2818</em> <a class="iref" href="#rfc.xref.RFC2818.1">2.2.1</a>, <a class="iref" href="#RFC2818"><b>11.2</b></a></li> 2967 <li class="indline1"><em>RFC2965</em> <a class="iref" href="#rfc.xref.RFC2965.1">3.2</a>, <a class="iref" href="#RFC2965"><b>11.2</b></a></li> 2968 <li class="indline1"><em>RFC3864</em> <a class="iref" href="#rfc.xref.RFC3864.1">8.1</a>, <a class="iref" href="#RFC3864"><b>11.2</b></a></li> 2969 <li class="indline1"><em>RFC3977</em> <a class="iref" href="#rfc.xref.RFC3977.1">1</a>, <a class="iref" href="#RFC3977"><b>11.2</b></a></li> 2970 <li class="indline1"><em>RFC3986</em> <a class="iref" href="#rfc.xref.RFC3986.1">1</a>, <a class="iref" href="#rfc.xref.RFC3986.2">2.2</a>, <a class="iref" href="#rfc.xref.RFC3986.3">2.2</a>, <a class="iref" href="#rfc.xref.RFC3986.4">2.2</a>, <a class="iref" href="#rfc.xref.RFC3986.5">2.2</a>, <a class="iref" href="#rfc.xref.RFC3986.6">2.2</a>, <a class="iref" href="#rfc.xref.RFC3986.7">2.2</a>, <a class="iref" href="#rfc.xref.RFC3986.8">2.2</a>, <a class="iref" href="#rfc.xref.RFC3986.9">2.2</a>, <a class="iref" href="#rfc.xref.RFC3986.10">2.2</a>, <a class="iref" href="#rfc.xref.RFC3986.11">2.2</a>, <a class="iref" href="#rfc.xref.RFC3986.12">2.2</a>, <a class="iref" href="#rfc.xref.RFC3986.13">2.2.2</a>, <a class="iref" href="#rfc.xref.RFC3986.14">4.1.2</a>, <a class="iref" href="#RFC3986"><b>11.1</b></a><ul class="ind"> 2971 <li class="indline1"><em>Section 2.2</em> <a class="iref" href="#rfc.xref.RFC3986.13">2.2.2</a></li> 2972 <li class="indline1"><em>Section 2.4</em> <a class="iref" href="#rfc.xref.RFC3986.14">4.1.2</a></li> 2973 <li class="indline1"><em>Section 3.2.3</em> <a class="iref" href="#rfc.xref.RFC3986.9">2.2</a></li> 2974 <li class="indline1"><em>Section 3.2.2</em> <a class="iref" href="#rfc.xref.RFC3986.11">2.2</a></li> 2975 <li class="indline1"><em>Section 3.2</em> <a class="iref" href="#rfc.xref.RFC3986.5">2.2</a></li> 2976 <li class="indline1"><em>Section 3.3</em> <a class="iref" href="#rfc.xref.RFC3986.7">2.2</a>, <a class="iref" href="#rfc.xref.RFC3986.8">2.2</a></li> 2977 <li class="indline1"><em>Section 3.4</em> <a class="iref" href="#rfc.xref.RFC3986.10">2.2</a></li> 2978 <li class="indline1"><em>Section 3.5</em> <a class="iref" href="#rfc.xref.RFC3986.6">2.2</a></li> 2979 <li class="indline1"><em>Section 4.2</em> <a class="iref" href="#rfc.xref.RFC3986.12">2.2</a></li> 2980 <li class="indline1"><em>Section 4.3</em> <a class="iref" href="#rfc.xref.RFC3986.4">2.2</a></li> 2982 2981 </ul> 2983 2982 </li> 2984 <li class="indline1"><em>RFC4288</em> <a class="iref" href="#rfc.xref.RFC4288.1"> 9.3</a>, <a class="iref" href="#RFC4288"><b>12.2</b></a></li>2985 <li class="indline1"><em>RFC4395</em> <a class="iref" href="#rfc.xref.RFC4395.1"> 9.2</a>, <a class="iref" href="#RFC4395"><b>12.2</b></a></li>2986 <li class="indline1"><em>RFC5234</em> <a class="iref" href="#rfc.xref.RFC5234.1"> 2.1</a>, <a class="iref" href="#rfc.xref.RFC5234.2">2.2</a>, <a class="iref" href="#rfc.xref.RFC5234.3">2.2</a>, <a class="iref" href="#rfc.xref.RFC5234.4">11</a>, <a class="iref" href="#RFC5234"><b>12.1</b></a><ul class="ind">2987 <li class="indline1"><em>Appendix B.1</em> <a class="iref" href="#rfc.xref.RFC5234.3"> 2.2</a></li>2983 <li class="indline1"><em>RFC4288</em> <a class="iref" href="#rfc.xref.RFC4288.1">8.3</a>, <a class="iref" href="#RFC4288"><b>11.2</b></a></li> 2984 <li class="indline1"><em>RFC4395</em> <a class="iref" href="#rfc.xref.RFC4395.1">8.2</a>, <a class="iref" href="#RFC4395"><b>11.2</b></a></li> 2985 <li class="indline1"><em>RFC5234</em> <a class="iref" href="#rfc.xref.RFC5234.1">1.2.1</a>, <a class="iref" href="#rfc.xref.RFC5234.2">1.2.2</a>, <a class="iref" href="#rfc.xref.RFC5234.3">1.2.2</a>, <a class="iref" href="#rfc.xref.RFC5234.4">10</a>, <a class="iref" href="#RFC5234"><b>11.1</b></a><ul class="ind"> 2986 <li class="indline1"><em>Appendix B.1</em> <a class="iref" href="#rfc.xref.RFC5234.3">1.2.2</a></li> 2988 2987 </ul> 2989 2988 </li> 2990 <li class="indline1"><em>RFC5322</em> <a class="iref" href="#rfc.xref.RFC5322.1">1</a>, <a class="iref" href="#rfc.xref.RFC5322.2"> 4.1</a>, <a class="iref" href="#rfc.xref.RFC5322.3">4.2</a>, <a class="iref" href="#rfc.xref.RFC5322.4">8.3</a>, <a class="iref" href="#rfc.xref.RFC5322.5">8.9</a>, <a class="iref" href="#RFC5322"><b>12.2</b></a><ul class="ind">2991 <li class="indline1"><em>Section 2.1</em> <a class="iref" href="#rfc.xref.RFC5322.3"> 4.2</a></li>2992 <li class="indline1"><em>Section 3.6.1</em> <a class="iref" href="#rfc.xref.RFC5322.4"> 8.3</a></li>2993 <li class="indline1"><em>Section 3.6.7</em> <a class="iref" href="#rfc.xref.RFC5322.5"> 8.9</a></li>2989 <li class="indline1"><em>RFC5322</em> <a class="iref" href="#rfc.xref.RFC5322.1">1</a>, <a class="iref" href="#rfc.xref.RFC5322.2">3.1</a>, <a class="iref" href="#rfc.xref.RFC5322.3">3.2</a>, <a class="iref" href="#rfc.xref.RFC5322.4">7.3</a>, <a class="iref" href="#rfc.xref.RFC5322.5">7.9</a>, <a class="iref" href="#RFC5322"><b>11.2</b></a><ul class="ind"> 2990 <li class="indline1"><em>Section 2.1</em> <a class="iref" href="#rfc.xref.RFC5322.3">3.2</a></li> 2991 <li class="indline1"><em>Section 3.6.1</em> <a class="iref" href="#rfc.xref.RFC5322.4">7.3</a></li> 2992 <li class="indline1"><em>Section 3.6.7</em> <a class="iref" href="#rfc.xref.RFC5322.5">7.9</a></li> 2994 2993 </ul> 2995 2994 </li> 2996 <li class="indline1"><em>RFC959</em> <a class="iref" href="#rfc.xref.RFC959.1">1</a>, <a class="iref" href="#RFC959"><b>1 2.2</b></a></li>2995 <li class="indline1"><em>RFC959</em> <a class="iref" href="#rfc.xref.RFC959.1">1</a>, <a class="iref" href="#RFC959"><b>11.2</b></a></li> 2997 2996 </ul> 2998 2997 </li> 2999 2998 <li class="indline0"><a id="rfc.index.S" href="#rfc.index.S"><b>S</b></a><ul class="ind"> 3000 2999 <li class="indline1">server <a class="iref" href="#rfc.iref.s.1">C</a></li> 3001 <li class="indline1"><em>Spe</em> <a class="iref" href="#rfc.xref.Spe.1"> 7.1.1</a>, <a class="iref" href="#Spe"><b>12.2</b></a></li>3000 <li class="indline1"><em>Spe</em> <a class="iref" href="#rfc.xref.Spe.1">6.1.1</a>, <a class="iref" href="#Spe"><b>11.2</b></a></li> 3002 3001 </ul> 3003 3002 </li> 3004 3003 <li class="indline0"><a id="rfc.index.T" href="#rfc.index.T"><b>T</b></a><ul class="ind"> 3005 <li class="indline1">TE header <a class="iref" href="#rfc.xref.header.te.1"> 3.4</a>, <a class="iref" href="#rfc.xref.header.te.2">3.4.1</a>, <a class="iref" href="#rfc.iref.t.1"><b>8.5</b></a>, <a class="iref" href="#rfc.xref.header.te.3">9.1</a>, <a class="iref" href="#rfc.xref.header.te.4">B.3</a></li>3006 <li class="indline1"><em>Tou1998</em> <a class="iref" href="#rfc.xref.Tou1998.1"> 7.1.1</a>, <a class="iref" href="#Tou1998"><b>12.2</b></a></li>3007 <li class="indline1">Trailer header <a class="iref" href="#rfc.xref.header.trailer.1"> 3.4.1</a>, <a class="iref" href="#rfc.xref.header.trailer.2">4.5</a>, <a class="iref" href="#rfc.iref.t.2"><b>8.6</b></a>, <a class="iref" href="#rfc.xref.header.trailer.3">9.1</a></li>3008 <li class="indline1">Transfer-Encoding header <a class="iref" href="#rfc.xref.header.transfer-encoding.1"> 3.4</a>, <a class="iref" href="#rfc.xref.header.transfer-encoding.2">4.3</a>, <a class="iref" href="#rfc.xref.header.transfer-encoding.3">4.4</a>, <a class="iref" href="#rfc.xref.header.transfer-encoding.4">4.5</a>, <a class="iref" href="#rfc.iref.t.3"><b>8.7</b></a>, <a class="iref" href="#rfc.xref.header.transfer-encoding.5">9.1</a></li>3004 <li class="indline1">TE header <a class="iref" href="#rfc.xref.header.te.1">2.4</a>, <a class="iref" href="#rfc.xref.header.te.2">2.4.1</a>, <a class="iref" href="#rfc.iref.t.1"><b>7.5</b></a>, <a class="iref" href="#rfc.xref.header.te.3">8.1</a>, <a class="iref" href="#rfc.xref.header.te.4">B.3</a></li> 3005 <li class="indline1"><em>Tou1998</em> <a class="iref" href="#rfc.xref.Tou1998.1">6.1.1</a>, <a class="iref" href="#Tou1998"><b>11.2</b></a></li> 3006 <li class="indline1">Trailer header <a class="iref" href="#rfc.xref.header.trailer.1">2.4.1</a>, <a class="iref" href="#rfc.xref.header.trailer.2">3.5</a>, <a class="iref" href="#rfc.iref.t.2"><b>7.6</b></a>, <a class="iref" href="#rfc.xref.header.trailer.3">8.1</a></li> 3007 <li class="indline1">Transfer-Encoding header <a class="iref" href="#rfc.xref.header.transfer-encoding.1">2.4</a>, <a class="iref" href="#rfc.xref.header.transfer-encoding.2">3.3</a>, <a class="iref" href="#rfc.xref.header.transfer-encoding.3">3.4</a>, <a class="iref" href="#rfc.xref.header.transfer-encoding.4">3.5</a>, <a class="iref" href="#rfc.iref.t.3"><b>7.7</b></a>, <a class="iref" href="#rfc.xref.header.transfer-encoding.5">8.1</a></li> 3009 3008 <li class="indline1">tunnel <a class="iref" href="#rfc.iref.t.4">C</a></li> 3010 3009 </ul> 3011 3010 </li> 3012 3011 <li class="indline0"><a id="rfc.index.U" href="#rfc.index.U"><b>U</b></a><ul class="ind"> 3013 <li class="indline1">Upgrade header <a class="iref" href="#rfc.xref.header.upgrade.1"> 4.5</a>, <a class="iref" href="#rfc.iref.u.3"><b>8.8</b></a>, <a class="iref" href="#rfc.xref.header.upgrade.2">9.1</a></li>3012 <li class="indline1">Upgrade header <a class="iref" href="#rfc.xref.header.upgrade.1">3.5</a>, <a class="iref" href="#rfc.iref.u.3"><b>7.8</b></a>, <a class="iref" href="#rfc.xref.header.upgrade.2">8.1</a></li> 3014 3013 <li class="indline1">upstream <a class="iref" href="#rfc.iref.u.5">C</a></li> 3015 3014 <li class="indline1">URI scheme 3016 3015 <ul class="ind"> 3017 <li class="indline1">http <a class="iref" href="#rfc.iref.u.1"><b> 3.2.1</b></a></li>3018 <li class="indline1">https <a class="iref" href="#rfc.iref.u.2"> 3.2.1</a></li>3016 <li class="indline1">http <a class="iref" href="#rfc.iref.u.1"><b>2.2.1</b></a></li> 3017 <li class="indline1">https <a class="iref" href="#rfc.iref.u.2">2.2.1</a></li> 3019 3018 </ul> 3020 3019 </li> 3021 <li class="indline1"><em>USASCII</em> <a class="iref" href="#rfc.xref.USASCII.1"> 2.2</a>, <a class="iref" href="#USASCII"><b>12.1</b></a></li>3020 <li class="indline1"><em>USASCII</em> <a class="iref" href="#rfc.xref.USASCII.1">1.2.2</a>, <a class="iref" href="#USASCII"><b>11.1</b></a></li> 3022 3021 <li class="indline1">user agent <a class="iref" href="#rfc.iref.u.4">C</a></li> 3023 3022 </ul> … … 3025 3024 <li class="indline0"><a id="rfc.index.V" href="#rfc.index.V"><b>V</b></a><ul class="ind"> 3026 3025 <li class="indline1">variant <a class="iref" href="#rfc.iref.v.2">C</a></li> 3027 <li class="indline1">Via header <a class="iref" href="#rfc.xref.header.via.1"> 4.5</a>, <a class="iref" href="#rfc.iref.v.1"><b>8.9</b></a>, <a class="iref" href="#rfc.xref.header.via.2">9.1</a></li>3026 <li class="indline1">Via header <a class="iref" href="#rfc.xref.header.via.1">3.5</a>, <a class="iref" href="#rfc.iref.v.1"><b>7.9</b></a>, <a class="iref" href="#rfc.xref.header.via.2">8.1</a></li> 3028 3027 </ul> 3029 3028 </li> 3030 3029 <li class="indline0"><a id="rfc.index.W" href="#rfc.index.W"><b>W</b></a><ul class="ind"> 3031 <li class="indline1"><em>WAIS</em> <a class="iref" href="#rfc.xref.WAIS.1">1</a>, <a class="iref" href="#WAIS"><b>1 2.2</b></a></li>3030 <li class="indline1"><em>WAIS</em> <a class="iref" href="#rfc.xref.WAIS.1">1</a>, <a class="iref" href="#WAIS"><b>11.2</b></a></li> 3032 3031 </ul> 3033 3032 </li> -
draft-ietf-httpbis/latest/p1-messaging.xml
r385 r389 280 280 </section> 281 281 282 <section title="Overall Operation" anchor="intro.overall.operation">283 <t>284 HTTP is a request/response protocol. A client sends a285 request to the server in the form of a request method, URI, and286 protocol version, followed by a MIME-like message containing request287 modifiers, client information, and possible body content over a288 connection with a server. The server responds with a status line,289 including the message's protocol version and a success or error code,290 followed by a MIME-like message containing server information, entity291 metainformation, and possible entity-body content. The relationship292 between HTTP and MIME is described in &diff2045entity;.293 </t>294 <t>295 Most HTTP communication is initiated by a user agent and consists of296 a request to be applied to a resource on some origin server. In the297 simplest case, this may be accomplished via a single connection (v)298 between the user agent (UA) and the origin server (O).299 </t>300 <figure><artwork type="drawing">301 request chain ------------------------>302 UA -------------------v------------------- O303 <----------------------- response chain304 </artwork></figure>305 <t>306 A more complicated situation occurs when one or more intermediaries307 are present in the request/response chain. There are three common308 forms of intermediary: proxy, gateway, and tunnel. A proxy is a309 forwarding agent, receiving requests for a URI in its absolute form,310 rewriting all or part of the message, and forwarding the reformatted311 request toward the server identified by the URI. A gateway is a312 receiving agent, acting as a layer above some other server(s) and, if313 necessary, translating the requests to the underlying server's314 protocol. A tunnel acts as a relay point between two connections315 without changing the messages; tunnels are used when the316 communication needs to pass through an intermediary (such as a317 firewall) even when the intermediary cannot understand the contents318 of the messages.319 </t>320 <figure><artwork type="drawing">321 request chain -------------------------------------->322 UA -----v----- A -----v----- B -----v----- C -----v----- O323 <------------------------------------- response chain324 </artwork></figure>325 <t>326 The figure above shows three intermediaries (A, B, and C) between the327 user agent and origin server. A request or response message that328 travels the whole chain will pass through four separate connections.329 This distinction is important because some HTTP communication options330 may apply only to the connection with the nearest, non-tunnel331 neighbor, only to the end-points of the chain, or to all connections332 along the chain. Although the diagram is linear, each participant may333 be engaged in multiple, simultaneous communications. For example, B334 may be receiving requests from many clients other than A, and/or335 forwarding requests to servers other than C, at the same time that it336 is handling A's request.337 </t>338 <t>339 Any party to the communication which is not acting as a tunnel may340 employ an internal cache for handling requests. The effect of a cache341 is that the request/response chain is shortened if one of the342 participants along the chain has a cached response applicable to that343 request. The following illustrates the resulting chain if B has a344 cached copy of an earlier response from O (via C) for a request which345 has not been cached by UA or A.346 </t>347 <figure><artwork type="drawing">348 request chain ---------->349 UA -----v----- A -----v----- B - - - - - - C - - - - - - O350 <--------- response chain351 </artwork></figure>352 <t>353 Not all responses are usefully cacheable, and some requests may354 contain modifiers which place special requirements on cache behavior.355 HTTP requirements for cache behavior and cacheable responses are356 defined in &caching;.357 </t>358 <t>359 In fact, there are a wide variety of architectures and configurations360 of caches and proxies currently being experimented with or deployed361 across the World Wide Web. These systems include national hierarchies362 of proxy caches to save transoceanic bandwidth, systems that363 broadcast or multicast cache entries, organizations that distribute364 subsets of cached data via CD-ROM, and so on. HTTP systems are used365 in corporate intranets over high-bandwidth links, and for access via366 PDAs with low-power radio links and intermittent connectivity. The367 goal of HTTP/1.1 is to support the wide diversity of configurations368 already deployed while introducing protocol constructs that meet the369 needs of those who build web applications that require high370 reliability and, failing that, at least reliable indications of371 failure.372 </t>373 <t>374 HTTP communication usually takes place over TCP/IP connections. The375 default port is TCP 80 (<eref target="http://www.iana.org/assignments/port-numbers"/>), but other ports can be used. This does376 not preclude HTTP from being implemented on top of any other protocol377 on the Internet, or on other networks. HTTP only presumes a reliable378 transport; any protocol that provides such guarantees can be used;379 the mapping of the HTTP/1.1 request and response structures onto the380 transport data units of the protocol in question is outside the scope381 of this specification.382 </t>383 <t>384 In HTTP/1.0, most implementations used a new connection for each385 request/response exchange. In HTTP/1.1, a connection may be used for386 one or more request/response exchanges, although connections may be387 closed for a variety of reasons (see <xref target="persistent.connections"/>).388 </t>389 </section>390 </section>391 392 282 <section title="Notational Conventions and Generic Grammar" anchor="notation"> 393 283 … … 600 490 601 491 </section> 492 493 <section title="Overall Operation" anchor="intro.overall.operation"> 494 <t> 495 HTTP is a request/response protocol. A client sends a 496 request to the server in the form of a request method, URI, and 497 protocol version, followed by a MIME-like message containing request 498 modifiers, client information, and possible body content over a 499 connection with a server. The server responds with a status line, 500 including the message's protocol version and a success or error code, 501 followed by a MIME-like message containing server information, entity 502 metainformation, and possible entity-body content. The relationship 503 between HTTP and MIME is described in &diff2045entity;. 504 </t> 505 <t> 506 Most HTTP communication is initiated by a user agent and consists of 507 a request to be applied to a resource on some origin server. In the 508 simplest case, this may be accomplished via a single connection (v) 509 between the user agent (UA) and the origin server (O). 510 </t> 511 <figure><artwork type="drawing"> 512 request chain ------------------------> 513 UA -------------------v------------------- O 514 <----------------------- response chain 515 </artwork></figure> 516 <t> 517 A more complicated situation occurs when one or more intermediaries 518 are present in the request/response chain. There are three common 519 forms of intermediary: proxy, gateway, and tunnel. A proxy is a 520 forwarding agent, receiving requests for a URI in its absolute form, 521 rewriting all or part of the message, and forwarding the reformatted 522 request toward the server identified by the URI. A gateway is a 523 receiving agent, acting as a layer above some other server(s) and, if 524 necessary, translating the requests to the underlying server's 525 protocol. A tunnel acts as a relay point between two connections 526 without changing the messages; tunnels are used when the 527 communication needs to pass through an intermediary (such as a 528 firewall) even when the intermediary cannot understand the contents 529 of the messages. 530 </t> 531 <figure><artwork type="drawing"> 532 request chain --------------------------------------> 533 UA -----v----- A -----v----- B -----v----- C -----v----- O 534 <------------------------------------- response chain 535 </artwork></figure> 536 <t> 537 The figure above shows three intermediaries (A, B, and C) between the 538 user agent and origin server. A request or response message that 539 travels the whole chain will pass through four separate connections. 540 This distinction is important because some HTTP communication options 541 may apply only to the connection with the nearest, non-tunnel 542 neighbor, only to the end-points of the chain, or to all connections 543 along the chain. Although the diagram is linear, each participant may 544 be engaged in multiple, simultaneous communications. For example, B 545 may be receiving requests from many clients other than A, and/or 546 forwarding requests to servers other than C, at the same time that it 547 is handling A's request. 548 </t> 549 <t> 550 Any party to the communication which is not acting as a tunnel may 551 employ an internal cache for handling requests. The effect of a cache 552 is that the request/response chain is shortened if one of the 553 participants along the chain has a cached response applicable to that 554 request. The following illustrates the resulting chain if B has a 555 cached copy of an earlier response from O (via C) for a request which 556 has not been cached by UA or A. 557 </t> 558 <figure><artwork type="drawing"> 559 request chain ----------> 560 UA -----v----- A -----v----- B - - - - - - C - - - - - - O 561 <--------- response chain 562 </artwork></figure> 563 <t> 564 Not all responses are usefully cacheable, and some requests may 565 contain modifiers which place special requirements on cache behavior. 566 HTTP requirements for cache behavior and cacheable responses are 567 defined in &caching;. 568 </t> 569 <t> 570 In fact, there are a wide variety of architectures and configurations 571 of caches and proxies currently being experimented with or deployed 572 across the World Wide Web. These systems include national hierarchies 573 of proxy caches to save transoceanic bandwidth, systems that 574 broadcast or multicast cache entries, organizations that distribute 575 subsets of cached data via CD-ROM, and so on. HTTP systems are used 576 in corporate intranets over high-bandwidth links, and for access via 577 PDAs with low-power radio links and intermittent connectivity. The 578 goal of HTTP/1.1 is to support the wide diversity of configurations 579 already deployed while introducing protocol constructs that meet the 580 needs of those who build web applications that require high 581 reliability and, failing that, at least reliable indications of 582 failure. 583 </t> 584 <t> 585 HTTP communication usually takes place over TCP/IP connections. The 586 default port is TCP 80 (<eref target="http://www.iana.org/assignments/port-numbers"/>), but other ports can be used. This does 587 not preclude HTTP from being implemented on top of any other protocol 588 on the Internet, or on other networks. HTTP only presumes a reliable 589 transport; any protocol that provides such guarantees can be used; 590 the mapping of the HTTP/1.1 request and response structures onto the 591 transport data units of the protocol in question is outside the scope 592 of this specification. 593 </t> 594 <t> 595 In HTTP/1.0, most implementations used a new connection for each 596 request/response exchange. In HTTP/1.1, a connection may be used for 597 one or more request/response exchanges, although connections may be 598 closed for a variety of reasons (see <xref target="persistent.connections"/>). 599 </t> 600 </section> 601 </section> 602 602 603 603 604 <section title="Protocol Parameters" anchor="protocol.parameters">
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