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294       content: "HTTP/1.1, Part 2";
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297       content: "Fielding, et al.";
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318</style><link rel="Contents" href="#rfc.toc">
319      <link rel="Author" href="#rfc.authors">
320      <link rel="Copyright" href="#rfc.copyright">
321      <link rel="Index" href="#rfc.index">
322      <link rel="Chapter" title="1 Introduction" href="#rfc.section.1">
323      <link rel="Chapter" title="2 Notational Conventions and Generic Grammar" href="#rfc.section.2">
324      <link rel="Chapter" title="3 Method" href="#rfc.section.3">
325      <link rel="Chapter" title="4 Request Header Fields" href="#rfc.section.4">
326      <link rel="Chapter" title="5 Status Code and Reason Phrase" href="#rfc.section.5">
327      <link rel="Chapter" title="6 Response Header Fields" href="#rfc.section.6">
328      <link rel="Chapter" title="7 Entity" href="#rfc.section.7">
329      <link rel="Chapter" title="8 Method Definitions" href="#rfc.section.8">
330      <link rel="Chapter" title="9 Status Code Definitions" href="#rfc.section.9">
331      <link rel="Chapter" title="10 Header Field Definitions" href="#rfc.section.10">
332      <link rel="Chapter" title="11 IANA Considerations" href="#rfc.section.11">
333      <link rel="Chapter" title="12 Security Considerations" href="#rfc.section.12">
334      <link rel="Chapter" title="13 Acknowledgments" href="#rfc.section.13">
335      <link rel="Chapter" href="#rfc.section.14" title="14 References">
336      <link rel="Appendix" title="A Compatibility with Previous Versions" href="#rfc.section.A">
337      <link rel="Appendix" title="B Change Log (to be removed by RFC Editor before publication)" href="#rfc.section.B">
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339      <link rel="schema.dct" href="">
340      <meta name="dct.creator" content="Fielding, R.">
341      <meta name="dct.creator" content="Gettys, J.">
342      <meta name="dct.creator" content="Mogul, J.">
343      <meta name="dct.creator" content="Frystyk, H.">
344      <meta name="dct.creator" content="Masinter, L.">
345      <meta name="dct.creator" content="Leach, P.">
346      <meta name="dct.creator" content="Berners-Lee, T.">
347      <meta name="dct.creator" content="Lafon, Y.">
348      <meta name="dct.creator" content="Reschke, J. F.">
349      <meta name="dct.identifier" content="urn:ietf:id:draft-ietf-httpbis-p2-semantics-02">
350      <meta name="dct.issued" scheme="ISO8601" content="2008-02-24">
351      <meta name="dct.replaces" content="urn:ietf:rfc:2616">
352      <meta name="dct.abstract" content="The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypermedia information systems. HTTP has been in use by the World Wide Web global information initiative since 1990. This document is Part 2 of the seven-part specification that defines the protocol referred to as &#34;HTTP/1.1&#34; and, taken together, obsoletes RFC 2616. Part 2 defines the semantics of HTTP messages as expressed by request methods, request-header fields, response status codes, and response-header fields.">
353      <meta name="description" content="The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypermedia information systems. HTTP has been in use by the World Wide Web global information initiative since 1990. This document is Part 2 of the seven-part specification that defines the protocol referred to as &#34;HTTP/1.1&#34; and, taken together, obsoletes RFC 2616. Part 2 defines the semantics of HTTP messages as expressed by request methods, request-header fields, response status codes, and response-header fields.">
354   </head>
355   <body>
356      <table class="header">
357         <tbody>
358            <tr>
359               <td class="left">Network Working Group</td>
360               <td class="right">R. Fielding, Editor</td>
361            </tr>
362            <tr>
363               <td class="left">Internet-Draft</td>
364               <td class="right">Day Software</td>
365            </tr>
366            <tr>
367               <td class="left">Obsoletes: <a href="">2616</a> (if approved)
368               </td>
369               <td class="right">J. Gettys</td>
370            </tr>
371            <tr>
372               <td class="left">Intended status: Standards Track</td>
373               <td class="right">One Laptop per Child</td>
374            </tr>
375            <tr>
376               <td class="left">Expires: August 27, 2008</td>
377               <td class="right">J. Mogul</td>
378            </tr>
379            <tr>
380               <td class="left"></td>
381               <td class="right">HP</td>
382            </tr>
383            <tr>
384               <td class="left"></td>
385               <td class="right">H. Frystyk</td>
386            </tr>
387            <tr>
388               <td class="left"></td>
389               <td class="right">Microsoft</td>
390            </tr>
391            <tr>
392               <td class="left"></td>
393               <td class="right">L. Masinter</td>
394            </tr>
395            <tr>
396               <td class="left"></td>
397               <td class="right">Adobe Systems</td>
398            </tr>
399            <tr>
400               <td class="left"></td>
401               <td class="right">P. Leach</td>
402            </tr>
403            <tr>
404               <td class="left"></td>
405               <td class="right">Microsoft</td>
406            </tr>
407            <tr>
408               <td class="left"></td>
409               <td class="right">T. Berners-Lee</td>
410            </tr>
411            <tr>
412               <td class="left"></td>
413               <td class="right">W3C/MIT</td>
414            </tr>
415            <tr>
416               <td class="left"></td>
417               <td class="right">Y. Lafon, Editor</td>
418            </tr>
419            <tr>
420               <td class="left"></td>
421               <td class="right">W3C</td>
422            </tr>
423            <tr>
424               <td class="left"></td>
425               <td class="right">J. Reschke, Editor</td>
426            </tr>
427            <tr>
428               <td class="left"></td>
429               <td class="right">greenbytes</td>
430            </tr>
431            <tr>
432               <td class="left"></td>
433               <td class="right">February 24, 2008</td>
434            </tr>
435         </tbody>
436      </table>
437      <p class="title">HTTP/1.1, part 2: Message Semantics<br><span class="filename">draft-ietf-httpbis-p2-semantics-02</span></p>
438      <div id="rfc.status">
439         <h1><a href="#rfc.status">Status of this Memo</a></h1>
440         <p>By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she
441            is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section
442            6 of BCP 79.
443         </p>
444         <p>Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note
445            that other groups may also distribute working documents as Internet-Drafts.
446         </p>
447         <p>Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other
448            documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as “work
449            in progress”.
450         </p>
451         <p>The list of current Internet-Drafts can be accessed at <a href=""></a>.
452         </p>
453         <p>The list of Internet-Draft Shadow Directories can be accessed at <a href=""></a>.
454         </p>
455         <p>This Internet-Draft will expire on August 27, 2008.</p>
456      </div>
457      <h1 id="rfc.abstract"><a href="#rfc.abstract">Abstract</a></h1>
458      <p>The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypermedia information
459         systems. HTTP has been in use by the World Wide Web global information initiative since 1990. This document is Part 2 of the
460         seven-part specification that defines the protocol referred to as "HTTP/1.1" and, taken together, obsoletes RFC 2616. Part
461         2 defines the semantics of HTTP messages as expressed by request methods, request-header fields, response status codes, and
462         response-header fields.
463      </p>
464      <h1 id="rfc.note.1"><a href="#rfc.note.1">Editorial Note (To be removed by RFC Editor)</a></h1>
465      <p>Discussion of this draft should take place on the HTTPBIS working group mailing list ( The current issues
466         list is at &lt;<a href=""></a>&gt; and related documents (including fancy diffs) can be found at &lt;<a href=""></a>&gt;.
467      </p>
468      <p>This draft incorporates those issue resolutions that were either collected in the original RFC2616 errata list (&lt;<a href=""></a>&gt;), or which were agreed upon on the mailing list between October 2006 and November 2007 (as published in "draft-lafon-rfc2616bis-03").
469      </p>
470      <hr class="noprint">
471      <h1 class="np" id="rfc.toc"><a href="#rfc.toc">Table of Contents</a></h1>
472      <ul class="toc">
473         <li><a href="#rfc.section.1">1.</a>&nbsp;&nbsp;&nbsp;<a href="#introduction">Introduction</a><ul>
474               <li><a href="#rfc.section.1.1">1.1</a>&nbsp;&nbsp;&nbsp;<a href="#intro.requirements">Requirements</a></li>
475            </ul>
476         </li>
477         <li><a href="#rfc.section.2">2.</a>&nbsp;&nbsp;&nbsp;<a href="#notation">Notational Conventions and Generic Grammar</a></li>
478         <li><a href="#rfc.section.3">3.</a>&nbsp;&nbsp;&nbsp;<a href="#method">Method</a></li>
479         <li><a href="#rfc.section.4">4.</a>&nbsp;&nbsp;&nbsp;<a href="#request.header.fields">Request Header Fields</a></li>
480         <li><a href="#rfc.section.5">5.</a>&nbsp;&nbsp;&nbsp;<a href="#status.code.and.reason.phrase">Status Code and Reason Phrase</a></li>
481         <li><a href="#rfc.section.6">6.</a>&nbsp;&nbsp;&nbsp;<a href="#response.header.fields">Response Header Fields</a></li>
482         <li><a href="#rfc.section.7">7.</a>&nbsp;&nbsp;&nbsp;<a href="#entity">Entity</a></li>
483         <li><a href="#rfc.section.8">8.</a>&nbsp;&nbsp;&nbsp;<a href="#method.definitions">Method Definitions</a><ul>
484               <li><a href="#rfc.section.8.1">8.1</a>&nbsp;&nbsp;&nbsp;<a href="#safe.and.idempotent">Safe and Idempotent Methods</a><ul>
485                     <li><a href="#rfc.section.8.1.1">8.1.1</a>&nbsp;&nbsp;&nbsp;<a href="#safe.methods">Safe Methods</a></li>
486                     <li><a href="#rfc.section.8.1.2">8.1.2</a>&nbsp;&nbsp;&nbsp;<a href="#idempotent.methods">Idempotent Methods</a></li>
487                  </ul>
488               </li>
489               <li><a href="#rfc.section.8.2">8.2</a>&nbsp;&nbsp;&nbsp;<a href="#OPTIONS">OPTIONS</a></li>
490               <li><a href="#rfc.section.8.3">8.3</a>&nbsp;&nbsp;&nbsp;<a href="#GET">GET</a></li>
491               <li><a href="#rfc.section.8.4">8.4</a>&nbsp;&nbsp;&nbsp;<a href="#HEAD">HEAD</a></li>
492               <li><a href="#rfc.section.8.5">8.5</a>&nbsp;&nbsp;&nbsp;<a href="#POST">POST</a></li>
493               <li><a href="#rfc.section.8.6">8.6</a>&nbsp;&nbsp;&nbsp;<a href="#PUT">PUT</a></li>
494               <li><a href="#rfc.section.8.7">8.7</a>&nbsp;&nbsp;&nbsp;<a href="#DELETE">DELETE</a></li>
495               <li><a href="#rfc.section.8.8">8.8</a>&nbsp;&nbsp;&nbsp;<a href="#TRACE">TRACE</a></li>
496               <li><a href="#rfc.section.8.9">8.9</a>&nbsp;&nbsp;&nbsp;<a href="#CONNECT">CONNECT</a></li>
497            </ul>
498         </li>
499         <li><a href="#rfc.section.9">9.</a>&nbsp;&nbsp;&nbsp;<a href="">Status Code Definitions</a><ul>
500               <li><a href="#rfc.section.9.1">9.1</a>&nbsp;&nbsp;&nbsp;<a href="#status.1xx">Informational 1xx</a><ul>
501                     <li><a href="#rfc.section.9.1.1">9.1.1</a>&nbsp;&nbsp;&nbsp;<a href="#status.100">100 Continue</a></li>
502                     <li><a href="#rfc.section.9.1.2">9.1.2</a>&nbsp;&nbsp;&nbsp;<a href="#status.101">101 Switching Protocols</a></li>
503                  </ul>
504               </li>
505               <li><a href="#rfc.section.9.2">9.2</a>&nbsp;&nbsp;&nbsp;<a href="#status.2xx">Successful 2xx</a><ul>
506                     <li><a href="#rfc.section.9.2.1">9.2.1</a>&nbsp;&nbsp;&nbsp;<a href="#status.200">200 OK</a></li>
507                     <li><a href="#rfc.section.9.2.2">9.2.2</a>&nbsp;&nbsp;&nbsp;<a href="#status.201">201 Created</a></li>
508                     <li><a href="#rfc.section.9.2.3">9.2.3</a>&nbsp;&nbsp;&nbsp;<a href="#status.202">202 Accepted</a></li>
509                     <li><a href="#rfc.section.9.2.4">9.2.4</a>&nbsp;&nbsp;&nbsp;<a href="#status.203">203 Non-Authoritative Information</a></li>
510                     <li><a href="#rfc.section.9.2.5">9.2.5</a>&nbsp;&nbsp;&nbsp;<a href="#status.204">204 No Content</a></li>
511                     <li><a href="#rfc.section.9.2.6">9.2.6</a>&nbsp;&nbsp;&nbsp;<a href="#status.205">205 Reset Content</a></li>
512                     <li><a href="#rfc.section.9.2.7">9.2.7</a>&nbsp;&nbsp;&nbsp;<a href="#status.206">206 Partial Content</a></li>
513                  </ul>
514               </li>
515               <li><a href="#rfc.section.9.3">9.3</a>&nbsp;&nbsp;&nbsp;<a href="#status.3xx">Redirection 3xx</a><ul>
516                     <li><a href="#rfc.section.9.3.1">9.3.1</a>&nbsp;&nbsp;&nbsp;<a href="#status.300">300 Multiple Choices</a></li>
517                     <li><a href="#rfc.section.9.3.2">9.3.2</a>&nbsp;&nbsp;&nbsp;<a href="#status.301">301 Moved Permanently</a></li>
518                     <li><a href="#rfc.section.9.3.3">9.3.3</a>&nbsp;&nbsp;&nbsp;<a href="#status.302">302 Found</a></li>
519                     <li><a href="#rfc.section.9.3.4">9.3.4</a>&nbsp;&nbsp;&nbsp;<a href="#status.303">303 See Other</a></li>
520                     <li><a href="#rfc.section.9.3.5">9.3.5</a>&nbsp;&nbsp;&nbsp;<a href="#status.304">304 Not Modified</a></li>
521                     <li><a href="#rfc.section.9.3.6">9.3.6</a>&nbsp;&nbsp;&nbsp;<a href="#status.305">305 Use Proxy</a></li>
522                     <li><a href="#rfc.section.9.3.7">9.3.7</a>&nbsp;&nbsp;&nbsp;<a href="#status.306">306 (Unused)</a></li>
523                     <li><a href="#rfc.section.9.3.8">9.3.8</a>&nbsp;&nbsp;&nbsp;<a href="#status.307">307 Temporary Redirect</a></li>
524                  </ul>
525               </li>
526               <li><a href="#rfc.section.9.4">9.4</a>&nbsp;&nbsp;&nbsp;<a href="#status.4xx">Client Error 4xx</a><ul>
527                     <li><a href="#rfc.section.9.4.1">9.4.1</a>&nbsp;&nbsp;&nbsp;<a href="#status.400">400 Bad Request</a></li>
528                     <li><a href="#rfc.section.9.4.2">9.4.2</a>&nbsp;&nbsp;&nbsp;<a href="#status.401">401 Unauthorized</a></li>
529                     <li><a href="#rfc.section.9.4.3">9.4.3</a>&nbsp;&nbsp;&nbsp;<a href="#status.402">402 Payment Required</a></li>
530                     <li><a href="#rfc.section.9.4.4">9.4.4</a>&nbsp;&nbsp;&nbsp;<a href="#status.403">403 Forbidden</a></li>
531                     <li><a href="#rfc.section.9.4.5">9.4.5</a>&nbsp;&nbsp;&nbsp;<a href="#status.404">404 Not Found</a></li>
532                     <li><a href="#rfc.section.9.4.6">9.4.6</a>&nbsp;&nbsp;&nbsp;<a href="#status.405">405 Method Not Allowed</a></li>
533                     <li><a href="#rfc.section.9.4.7">9.4.7</a>&nbsp;&nbsp;&nbsp;<a href="#status.406">406 Not Acceptable</a></li>
534                     <li><a href="#rfc.section.9.4.8">9.4.8</a>&nbsp;&nbsp;&nbsp;<a href="#status.407">407 Proxy Authentication Required</a></li>
535                     <li><a href="#rfc.section.9.4.9">9.4.9</a>&nbsp;&nbsp;&nbsp;<a href="#status.408">408 Request Timeout</a></li>
536                     <li><a href="#rfc.section.9.4.10">9.4.10</a>&nbsp;&nbsp;&nbsp;<a href="#status.409">409 Conflict</a></li>
537                     <li><a href="#rfc.section.9.4.11">9.4.11</a>&nbsp;&nbsp;&nbsp;<a href="#status.410">410 Gone</a></li>
538                     <li><a href="#rfc.section.9.4.12">9.4.12</a>&nbsp;&nbsp;&nbsp;<a href="#status.411">411 Length Required</a></li>
539                     <li><a href="#rfc.section.9.4.13">9.4.13</a>&nbsp;&nbsp;&nbsp;<a href="#status.412">412 Precondition Failed</a></li>
540                     <li><a href="#rfc.section.9.4.14">9.4.14</a>&nbsp;&nbsp;&nbsp;<a href="#status.413">413 Request Entity Too Large</a></li>
541                     <li><a href="#rfc.section.9.4.15">9.4.15</a>&nbsp;&nbsp;&nbsp;<a href="#status.414">414 Request-URI Too Long</a></li>
542                     <li><a href="#rfc.section.9.4.16">9.4.16</a>&nbsp;&nbsp;&nbsp;<a href="#status.415">415 Unsupported Media Type</a></li>
543                     <li><a href="#rfc.section.9.4.17">9.4.17</a>&nbsp;&nbsp;&nbsp;<a href="#status.416">416 Requested Range Not Satisfiable</a></li>
544                     <li><a href="#rfc.section.9.4.18">9.4.18</a>&nbsp;&nbsp;&nbsp;<a href="#status.417">417 Expectation Failed</a></li>
545                  </ul>
546               </li>
547               <li><a href="#rfc.section.9.5">9.5</a>&nbsp;&nbsp;&nbsp;<a href="#status.5xx">Server Error 5xx</a><ul>
548                     <li><a href="#rfc.section.9.5.1">9.5.1</a>&nbsp;&nbsp;&nbsp;<a href="#status.500">500 Internal Server Error</a></li>
549                     <li><a href="#rfc.section.9.5.2">9.5.2</a>&nbsp;&nbsp;&nbsp;<a href="#status.501">501 Not Implemented</a></li>
550                     <li><a href="#rfc.section.9.5.3">9.5.3</a>&nbsp;&nbsp;&nbsp;<a href="#status.502">502 Bad Gateway</a></li>
551                     <li><a href="#rfc.section.9.5.4">9.5.4</a>&nbsp;&nbsp;&nbsp;<a href="#status.503">503 Service Unavailable</a></li>
552                     <li><a href="#rfc.section.9.5.5">9.5.5</a>&nbsp;&nbsp;&nbsp;<a href="#status.504">504 Gateway Timeout</a></li>
553                     <li><a href="#rfc.section.9.5.6">9.5.6</a>&nbsp;&nbsp;&nbsp;<a href="#status.505">505 HTTP Version Not Supported</a></li>
554                  </ul>
555               </li>
556            </ul>
557         </li>
558         <li><a href="#rfc.section.10">10.</a>&nbsp;&nbsp;&nbsp;<a href="#header.fields">Header Field Definitions</a><ul>
559               <li><a href="#rfc.section.10.1">10.1</a>&nbsp;&nbsp;&nbsp;<a href="#header.allow">Allow</a></li>
560               <li><a href="#rfc.section.10.2">10.2</a>&nbsp;&nbsp;&nbsp;<a href="#header.expect">Expect</a></li>
561               <li><a href="#rfc.section.10.3">10.3</a>&nbsp;&nbsp;&nbsp;<a href="#header.from">From</a></li>
562               <li><a href="#rfc.section.10.4">10.4</a>&nbsp;&nbsp;&nbsp;<a href="#header.location">Location</a></li>
563               <li><a href="#rfc.section.10.5">10.5</a>&nbsp;&nbsp;&nbsp;<a href="#header.max-forwards">Max-Forwards</a></li>
564               <li><a href="#rfc.section.10.6">10.6</a>&nbsp;&nbsp;&nbsp;<a href="#header.referer">Referer</a></li>
565               <li><a href="#rfc.section.10.7">10.7</a>&nbsp;&nbsp;&nbsp;<a href="#header.retry-after">Retry-After</a></li>
566               <li><a href="#rfc.section.10.8">10.8</a>&nbsp;&nbsp;&nbsp;<a href="#header.server">Server</a></li>
567               <li><a href="#rfc.section.10.9">10.9</a>&nbsp;&nbsp;&nbsp;<a href="#header.user-agent">User-Agent</a></li>
568            </ul>
569         </li>
570         <li><a href="#rfc.section.11">11.</a>&nbsp;&nbsp;&nbsp;<a href="#IANA.considerations">IANA Considerations</a></li>
571         <li><a href="#rfc.section.12">12.</a>&nbsp;&nbsp;&nbsp;<a href="#security.considerations">Security Considerations</a><ul>
572               <li><a href="#rfc.section.12.1">12.1</a>&nbsp;&nbsp;&nbsp;<a href="#security.sensitive">Transfer of Sensitive Information</a></li>
573               <li><a href="#rfc.section.12.2">12.2</a>&nbsp;&nbsp;&nbsp;<a href="">Encoding Sensitive Information in URIs</a></li>
574               <li><a href="#rfc.section.12.3">12.3</a>&nbsp;&nbsp;&nbsp;<a href="#location.spoofing">Location Headers and Spoofing</a></li>
575            </ul>
576         </li>
577         <li><a href="#rfc.section.13">13.</a>&nbsp;&nbsp;&nbsp;<a href="#ack">Acknowledgments</a></li>
578         <li><a href="#rfc.section.14">14.</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.references">References</a><ul>
579               <li><a href="#rfc.section.14.1">14.1</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.references.1">Normative References</a></li>
580               <li><a href="#rfc.section.14.2">14.2</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.references.2">Informative References</a></li>
581            </ul>
582         </li>
583         <li><a href="#rfc.section.A">A.</a>&nbsp;&nbsp;&nbsp;<a href="#compatibility">Compatibility with Previous Versions</a><ul>
584               <li><a href="#rfc.section.A.1">A.1</a>&nbsp;&nbsp;&nbsp;<a href="#changes.from.rfc.2068">Changes from RFC 2068</a></li>
585               <li><a href="#rfc.section.A.2">A.2</a>&nbsp;&nbsp;&nbsp;<a href="#changes.from.rfc.2616">Changes from RFC 2616</a></li>
586            </ul>
587         </li>
588         <li><a href="#rfc.section.B">B.</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.B">Change Log (to be removed by RFC Editor before publication)</a><ul>
589               <li><a href="#rfc.section.B.1">B.1</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.B.1">Since RFC2616</a></li>
590               <li><a href="#rfc.section.B.2">B.2</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.B.2">Since draft-ietf-httpbis-p2-semantics-00</a></li>
591               <li><a href="#rfc.section.B.3">B.3</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.section.B.3">Since draft-ietf-httpbis-p2-semantics-01</a></li>
592            </ul>
593         </li>
594         <li><a href="#rfc.index">Index</a></li>
595         <li><a href="#rfc.authors">Authors' Addresses</a></li>
596         <li><a href="#rfc.ipr">Intellectual Property and Copyright Statements</a></li>
597      </ul>
598      <div id="introduction">
599         <h1 id="rfc.section.1" class="np"><a href="#rfc.section.1">1.</a>&nbsp;<a href="#introduction">Introduction</a></h1>
600         <p id="rfc.section.1.p.1">This document defines HTTP/1.1 request and response semantics. Each HTTP message, as defined in <a href="#Part1" id="rfc.xref.Part1.1"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, is in the form of either a request or a response. An HTTP server listens on a connection for HTTP requests and responds
601            to each request, in the order received on that connection, with one or more HTTP response messages. This document defines
602            the commonly agreed upon semantics of the HTTP uniform interface, the intentions defined by each request method, and the various
603            response messages that might be expected as a result of applying that method for the requested resource.
604         </p>
605         <p id="rfc.section.1.p.2">This document is currently disorganized in order to minimize the changes between drafts and enable reviewers to see the smaller
606            errata changes. The next draft will reorganize the sections to better reflect the content. In particular, the sections will
607            be ordered according to the typical processing of an HTTP request message (after message parsing): resource mapping, general
608            header fields, methods, request modifiers, response status, and resource metadata. The current mess reflects how widely dispersed
609            these topics and associated requirements had become in <a href="#RFC2616" id="rfc.xref.RFC2616.1"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>.
610         </p>
611         <div id="intro.requirements">
612            <h2 id="rfc.section.1.1"><a href="#rfc.section.1.1">1.1</a>&nbsp;<a href="#intro.requirements">Requirements</a></h2>
613            <p id="rfc.section.1.1.p.1">The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"
614               in this document are to be interpreted as described in <a href="#RFC2119" id="rfc.xref.RFC2119.1"><cite title="Key words for use in RFCs to Indicate Requirement Levels">[RFC2119]</cite></a>.
615            </p>
616            <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."
617            </p>
618         </div>
619      </div>
620      <div id="notation">
621         <h1 id="rfc.section.2"><a href="#rfc.section.2">2.</a>&nbsp;<a href="#notation">Notational Conventions and Generic Grammar</a></h1>
622         <p id="rfc.section.2.p.1">This specification uses the ABNF syntax defined in <a href="p1-messaging.html#notation.abnf" title="Augmented BNF">Section 2.1</a> of <a href="#Part1" id="rfc.xref.Part1.2"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a> and the core rules defined in <a href="p1-messaging.html#basic.rules" title="Basic Rules">Section 2.2</a> of <a href="#Part1" id="rfc.xref.Part1.3"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>: <span class="comment" id="abnf.dep">[<a href="#abnf.dep" class="smpl">abnf.dep</a>: ABNF syntax and basic rules will be adopted from RFC 5234, see &lt;<a href=""></a>&gt;.]</span>
623         </p>
624         <div id="rfc.figure.u.1"></div><pre class="inline">  DIGIT         = &lt;DIGIT, defined in <a href="#Part1" id="rfc.xref.Part1.4"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#basic.rules" title="Basic Rules">Section 2.2</a>&gt;
625</pre><div id="rfc.figure.u.2"></div><pre class="inline">  comment       = &lt;comment, defined in <a href="#Part1" id="rfc.xref.Part1.5"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#basic.rules" title="Basic Rules">Section 2.2</a>&gt;
626  quoted-string = &lt;quoted-string, defined in <a href="#Part1" id="rfc.xref.Part1.6"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#basic.rules" title="Basic Rules">Section 2.2</a>&gt;
627  token         = &lt;token, defined in <a href="#Part1" id="rfc.xref.Part1.7"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#basic.rules" title="Basic Rules">Section 2.2</a>&gt;
628</pre><div id="abnf.dependencies">
629            <p id="rfc.section.2.p.4">The ABNF rules below are defined in other parts:</p>
630         </div>
631         <div id="rfc.figure.u.3"></div><pre class="inline">  absoluteURI   = &lt;absoluteURI, defined in <a href="#Part1" id="rfc.xref.Part1.8"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#general.syntax" title="General Syntax">Section 3.2.1</a>&gt;
632  fragment      = &lt;fragment, defined in <a href="#Part1" id="rfc.xref.Part1.9"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#general.syntax" title="General Syntax">Section 3.2.1</a>&gt;
633  Host          = &lt;Host, defined in <a href="#Part1" id="rfc.xref.Part1.10"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="" title="Host">Section 8.4</a>&gt;
634  HTTP-date     = &lt;HTTP-date, defined in <a href="#Part1" id="rfc.xref.Part1.11"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="" title="Full Date">Section 3.3.1</a>&gt;
635  product       = &lt;product, defined in <a href="#Part1" id="rfc.xref.Part1.12"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#product.tokens" title="Product Tokens">Section 3.5</a>&gt;
636  relativeURI   = &lt;relativeURI, defined in <a href="#Part1" id="rfc.xref.Part1.13"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#general.syntax" title="General Syntax">Section 3.2.1</a>&gt;
637  TE            = &lt;TE, defined in <a href="#Part1" id="rfc.xref.Part1.14"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#header.upgrade" title="Upgrade">Section 8.8</a>&gt;
638</pre><div id="rfc.figure.u.4"></div><pre class="inline">  Accept        = &lt;Accept, defined in <a href="#Part3" id="rfc.xref.Part3.1"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>, <a href="p3-payload.html#header.accept" title="Accept">Section 6.1</a>&gt;
639  Accept-Charset =
640             &lt;Accept-Charset, defined in <a href="#Part3" id="rfc.xref.Part3.2"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>, <a href="p3-payload.html#header.accept-charset" title="Accept-Charset">Section 6.2</a>&gt;
641  Accept-Encoding =
642             &lt;Accept-Encoding, defined in <a href="#Part3" id="rfc.xref.Part3.3"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>, <a href="p3-payload.html#header.accept-encoding" title="Accept-Encoding">Section 6.3</a>&gt;
643  Accept-Language =
644             &lt;Accept-Language, defined in <a href="#Part3" id="rfc.xref.Part3.4"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>, <a href="p3-payload.html#header.accept-language" title="Accept-Language">Section 6.4</a>&gt;
645</pre><div id="rfc.figure.u.5"></div><pre class="inline">  ETag          = &lt;ETag, defined in <a href="#Part4" id="rfc.xref.Part4.1"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>, <a href="p4-conditional.html#header.etag" title="ETag">Section 7.1</a>&gt;
646  If-Match      = &lt;If-Match, defined in <a href="#Part4" id="rfc.xref.Part4.2"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>, <a href="p4-conditional.html#header.if-match" title="If-Match">Section 7.2</a>&gt;
647  If-Modified-Since =
648             &lt;If-Modified-Since, defined in <a href="#Part4" id="rfc.xref.Part4.3"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>, <a href="p4-conditional.html#header.if-modified-since" title="If-Modified-Since">Section 7.3</a>&gt;
649  If-None-Match = &lt;If-None-Match, defined in <a href="#Part4" id="rfc.xref.Part4.4"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>, <a href="p4-conditional.html#header.if-none-match" title="If-None-Match">Section 7.4</a>&gt;
650  If-Unmodified-Since =
651             &lt;If-Unmodified-Since, defined in <a href="#Part4" id="rfc.xref.Part4.5"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>, <a href="p4-conditional.html#header.if-unmodified-since" title="If-Unmodified-Since">Section 7.5</a>&gt;
652</pre><div id="rfc.figure.u.6"></div><pre class="inline">  Accept-Ranges = &lt;Accept-Ranges, defined in <a href="#Part5" id="rfc.xref.Part5.1"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>, <a href="p5-range.html#header.accept-ranges" title="Accept-Ranges">Section 6.1</a>&gt;
653  If-Range      = &lt;If-Range, defined in <a href="#Part5" id="rfc.xref.Part5.2"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>, <a href="p5-range.html#header.if-range" title="If-Range">Section 6.3</a>&gt;
654  Range         = &lt;Range, defined in <a href="#Part5" id="rfc.xref.Part5.3"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>, <a href="p5-range.html#header.range" title="Range">Section 6.4</a>&gt;
655</pre><div id="rfc.figure.u.7"></div><pre class="inline">  Age           = &lt;Age, defined in <a href="#Part6" id="rfc.xref.Part6.1"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>, <a href="p6-cache.html#header.age" title="Age">Section 16.1</a>&gt;
656  Vary          = &lt;Vary, defined in <a href="#Part6" id="rfc.xref.Part6.2"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>, <a href="p6-cache.html#header.vary" title="Vary">Section 16.5</a>&gt;
657</pre><div id="rfc.figure.u.8"></div><pre class="inline">  Authorization = &lt;Authorization, defined in <a href="#Part7" id="rfc.xref.Part7.1"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a>, <a href="p7-auth.html#header.authorization" title="Authorization">Section 4.1</a>&gt;
658  Proxy-Authenticate =
659             &lt;Proxy-Authenticate, defined in <a href="#Part7" id="rfc.xref.Part7.2"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a>, <a href="p7-auth.html#header.proxy-authenticate" title="Proxy-Authenticate">Section 4.2</a>&gt;
660  Proxy-Authorization =
661             &lt;Proxy-Authorization, defined in <a href="#Part7" id="rfc.xref.Part7.3"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a>, <a href="p7-auth.html#header.proxy-authorization" title="Proxy-Authorization">Section 4.3</a>&gt;
662  WWW-Authenticate =
663             &lt;WWW-Authenticate, defined in <a href="#Part7" id="rfc.xref.Part7.4"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a>, <a href="p7-auth.html#header.www-authenticate" title="WWW-Authenticate">Section 4.4</a>&gt;
665      <div id="method">
666         <h1 id="rfc.section.3"><a href="#rfc.section.3">3.</a>&nbsp;<a href="#method">Method</a></h1>
667         <p id="rfc.section.3.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>
668         <div id="rfc.figure.u.9"></div><pre class="inline"><span id="rfc.iref.g.1"></span><span id="rfc.iref.g.2"></span>  Method         = "OPTIONS"                ; <a href="#OPTIONS" id="rfc.xref.OPTIONS.1" title="OPTIONS">Section&nbsp;8.2</a>
669                 | "GET"                    ; <a href="#GET" id="rfc.xref.GET.1" title="GET">Section&nbsp;8.3</a>
670                 | "HEAD"                   ; <a href="#HEAD" id="rfc.xref.HEAD.1" title="HEAD">Section&nbsp;8.4</a>
671                 | "POST"                   ; <a href="#POST" id="rfc.xref.POST.1" title="POST">Section&nbsp;8.5</a>
672                 | "PUT"                    ; <a href="#PUT" id="rfc.xref.PUT.1" title="PUT">Section&nbsp;8.6</a>
673                 | "DELETE"                 ; <a href="#DELETE" id="rfc.xref.DELETE.1" title="DELETE">Section&nbsp;8.7</a>
674                 | "TRACE"                  ; <a href="#TRACE" id="rfc.xref.TRACE.1" title="TRACE">Section&nbsp;8.8</a>
675                 | "CONNECT"                ; <a href="#CONNECT" id="rfc.xref.CONNECT.1" title="CONNECT">Section&nbsp;8.9</a>
676                 | extension-method
677  extension-method = token
678</pre><p id="rfc.section.3.p.3">The list of methods allowed by a resource can be specified in an Allow header field (<a href="#header.allow" id="rfc.xref.header.allow.1" title="Allow">Section&nbsp;10.1</a>). The return code of the response always notifies the client whether a method is currently allowed on a resource, since the
679            set of allowed methods can change dynamically. An origin server <em class="bcp14">SHOULD</em> return the status code 405 (Method Not Allowed) if the method is known by the origin server but not allowed for the requested
680            resource, and 501 (Not Implemented) if the method is unrecognized or not implemented by the origin server. The methods GET
681            and HEAD <em class="bcp14">MUST</em> be supported by all general-purpose servers. All other methods are <em class="bcp14">OPTIONAL</em>; however, if the above methods are implemented, they <em class="bcp14">MUST</em> be implemented with the same semantics as those specified in <a href="#method.definitions" title="Method Definitions">Section&nbsp;8</a>.
682         </p>
683      </div>
684      <div id="request.header.fields">
685         <h1 id="rfc.section.4"><a href="#rfc.section.4">4.</a>&nbsp;<a href="#request.header.fields">Request Header Fields</a></h1>
686         <p id="rfc.section.4.p.1">The request-header fields allow the client to pass additional information about the request, and about the client itself,
687            to the server. These fields act as request modifiers, with semantics equivalent to the parameters on a programming language
688            method invocation.
689         </p>
690         <div id="rfc.figure.u.10"></div><pre class="inline"><span id="rfc.iref.g.3"></span>  request-header = Accept                   ; <a href="#Part3" id="rfc.xref.Part3.5"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>, <a href="p3-payload.html#header.accept" title="Accept">Section 6.1</a>
691                 | Accept-Charset           ; <a href="#Part3" id="rfc.xref.Part3.6"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>, <a href="p3-payload.html#header.accept-charset" title="Accept-Charset">Section 6.2</a>
692                 | Accept-Encoding          ; <a href="#Part3" id="rfc.xref.Part3.7"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>, <a href="p3-payload.html#header.accept-encoding" title="Accept-Encoding">Section 6.3</a>
693                 | Accept-Language          ; <a href="#Part3" id="rfc.xref.Part3.8"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>, <a href="p3-payload.html#header.accept-language" title="Accept-Language">Section 6.4</a>
694                 | Authorization            ; <a href="#Part7" id="rfc.xref.Part7.5"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a>, <a href="p7-auth.html#header.authorization" title="Authorization">Section 4.1</a>
695                 | Expect                   ; <a href="#header.expect" id="rfc.xref.header.expect.1" title="Expect">Section&nbsp;10.2</a>
696                 | From                     ; <a href="#header.from" id="rfc.xref.header.from.1" title="From">Section&nbsp;10.3</a>
697                 | Host                     ; <a href="#Part1" id="rfc.xref.Part1.15"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="" title="Host">Section 8.4</a>
698                 | If-Match                 ; <a href="#Part4" id="rfc.xref.Part4.6"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>, <a href="p4-conditional.html#header.if-match" title="If-Match">Section 7.2</a>
699                 | If-Modified-Since        ; <a href="#Part4" id="rfc.xref.Part4.7"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>, <a href="p4-conditional.html#header.if-modified-since" title="If-Modified-Since">Section 7.3</a>
700                 | If-None-Match            ; <a href="#Part4" id="rfc.xref.Part4.8"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>, <a href="p4-conditional.html#header.if-none-match" title="If-None-Match">Section 7.4</a>
701                 | If-Range                 ; <a href="#Part5" id="rfc.xref.Part5.4"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>, <a href="p5-range.html#header.if-range" title="If-Range">Section 6.3</a>
702                 | If-Unmodified-Since      ; <a href="#Part4" id="rfc.xref.Part4.9"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>, <a href="p4-conditional.html#header.if-unmodified-since" title="If-Unmodified-Since">Section 7.5</a>
703                 | Max-Forwards             ; <a href="#header.max-forwards" id="rfc.xref.header.max-forwards.1" title="Max-Forwards">Section&nbsp;10.5</a>
704                 | Proxy-Authorization      ; <a href="#Part7" id="rfc.xref.Part7.6"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a>, <a href="p7-auth.html#header.proxy-authorization" title="Proxy-Authorization">Section 4.3</a>
705                 | Range                    ; <a href="#Part5" id="rfc.xref.Part5.5"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>, <a href="p5-range.html#header.range" title="Range">Section 6.4</a>
706                 | Referer                  ; <a href="#header.referer" id="rfc.xref.header.referer.1" title="Referer">Section&nbsp;10.6</a>
707                 | TE                       ; <a href="#Part1" id="rfc.xref.Part1.16"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, <a href="p1-messaging.html#header.upgrade" title="Upgrade">Section 8.8</a>
708                 | User-Agent               ; <a href="#header.user-agent" id="rfc.xref.header.user-agent.1" title="User-Agent">Section&nbsp;10.9</a>
709</pre><p id="rfc.section.4.p.3">Request-header field names can be extended reliably only in combination with a change in the protocol version. However, new
710            or experimental header fields <em class="bcp14">MAY</em> be given the semantics of request-header fields if all parties in the communication recognize them to be request-header fields.
711            Unrecognized header fields are treated as entity-header fields.
712         </p>
713      </div>
714      <div id="status.code.and.reason.phrase">
715         <h1 id="rfc.section.5"><a href="#rfc.section.5">5.</a>&nbsp;<a href="#status.code.and.reason.phrase">Status Code and Reason Phrase</a></h1>
716         <p id="rfc.section.5.p.1">The Status-Code element is a 3-digit integer result code of the attempt to understand and satisfy the request. The status
717            codes listed below are defined in <a href="" title="Status Code Definitions">Section&nbsp;9</a>. The Reason-Phrase is intended to give a short textual description of the Status-Code. The Status-Code is intended for use
718            by automata and the Reason-Phrase is intended for the human user. The client is not required to examine or display the Reason-Phrase.
719         </p>
720         <p id="rfc.section.5.p.2">The individual values of the numeric status codes defined for HTTP/1.1, and an example set of corresponding Reason-Phrase's,
721            are presented below. The reason phrases listed here are only recommendations -- they <em class="bcp14">MAY</em> be replaced by local equivalents without affecting the protocol.
722         </p>
723         <div id="rfc.figure.u.11"></div><pre class="inline"><span id="rfc.iref.g.4"></span><span id="rfc.iref.g.5"></span><span id="rfc.iref.g.6"></span>  Status-Code    =
724         "100"  ; <a href="#status.100" id="rfc.xref.status.100.1" title="100 Continue">Section&nbsp;9.1.1</a>: Continue
725       | "101"  ; <a href="#status.101" id="rfc.xref.status.101.1" title="101 Switching Protocols">Section&nbsp;9.1.2</a>: Switching Protocols
726       | "200"  ; <a href="#status.200" id="rfc.xref.status.200.1" title="200 OK">Section&nbsp;9.2.1</a>: OK
727       | "201"  ; <a href="#status.201" id="rfc.xref.status.201.1" title="201 Created">Section&nbsp;9.2.2</a>: Created
728       | "202"  ; <a href="#status.202" id="rfc.xref.status.202.1" title="202 Accepted">Section&nbsp;9.2.3</a>: Accepted
729       | "203"  ; <a href="#status.203" id="rfc.xref.status.203.1" title="203 Non-Authoritative Information">Section&nbsp;9.2.4</a>: Non-Authoritative Information
730       | "204"  ; <a href="#status.204" id="rfc.xref.status.204.1" title="204 No Content">Section&nbsp;9.2.5</a>: No Content
731       | "205"  ; <a href="#status.205" id="rfc.xref.status.205.1" title="205 Reset Content">Section&nbsp;9.2.6</a>: Reset Content
732       | "206"  ; <a href="#status.206" id="rfc.xref.status.206.1" title="206 Partial Content">Section&nbsp;9.2.7</a>: Partial Content
733       | "300"  ; <a href="#status.300" id="rfc.xref.status.300.1" title="300 Multiple Choices">Section&nbsp;9.3.1</a>: Multiple Choices
734       | "301"  ; <a href="#status.301" id="rfc.xref.status.301.1" title="301 Moved Permanently">Section&nbsp;9.3.2</a>: Moved Permanently
735       | "302"  ; <a href="#status.302" id="rfc.xref.status.302.1" title="302 Found">Section&nbsp;9.3.3</a>: Found
736       | "303"  ; <a href="#status.303" id="rfc.xref.status.303.1" title="303 See Other">Section&nbsp;9.3.4</a>: See Other
737       | "304"  ; <a href="#status.304" id="rfc.xref.status.304.1" title="304 Not Modified">Section&nbsp;9.3.5</a>: Not Modified
738       | "305"  ; <a href="#status.305" id="rfc.xref.status.305.1" title="305 Use Proxy">Section&nbsp;9.3.6</a>: Use Proxy
739       | "307"  ; <a href="#status.307" id="rfc.xref.status.307.1" title="307 Temporary Redirect">Section&nbsp;9.3.8</a>: Temporary Redirect
740       | "400"  ; <a href="#status.400" id="rfc.xref.status.400.1" title="400 Bad Request">Section&nbsp;9.4.1</a>: Bad Request
741       | "401"  ; <a href="#status.401" id="rfc.xref.status.401.1" title="401 Unauthorized">Section&nbsp;9.4.2</a>: Unauthorized
742       | "402"  ; <a href="#status.402" id="rfc.xref.status.402.1" title="402 Payment Required">Section&nbsp;9.4.3</a>: Payment Required
743       | "403"  ; <a href="#status.403" id="rfc.xref.status.403.1" title="403 Forbidden">Section&nbsp;9.4.4</a>: Forbidden
744       | "404"  ; <a href="#status.404" id="rfc.xref.status.404.1" title="404 Not Found">Section&nbsp;9.4.5</a>: Not Found
745       | "405"  ; <a href="#status.405" id="rfc.xref.status.405.1" title="405 Method Not Allowed">Section&nbsp;9.4.6</a>: Method Not Allowed
746       | "406"  ; <a href="#status.406" id="rfc.xref.status.406.1" title="406 Not Acceptable">Section&nbsp;9.4.7</a>: Not Acceptable
747       | "407"  ; <a href="#status.407" id="rfc.xref.status.407.1" title="407 Proxy Authentication Required">Section&nbsp;9.4.8</a>: Proxy Authentication Required
748       | "408"  ; <a href="#status.408" id="rfc.xref.status.408.1" title="408 Request Timeout">Section&nbsp;9.4.9</a>: Request Time-out
749       | "409"  ; <a href="#status.409" id="rfc.xref.status.409.1" title="409 Conflict">Section&nbsp;9.4.10</a>: Conflict
750       | "410"  ; <a href="#status.410" id="rfc.xref.status.410.1" title="410 Gone">Section&nbsp;9.4.11</a>: Gone
751       | "411"  ; <a href="#status.411" id="rfc.xref.status.411.1" title="411 Length Required">Section&nbsp;9.4.12</a>: Length Required
752       | "412"  ; <a href="#status.412" id="rfc.xref.status.412.1" title="412 Precondition Failed">Section&nbsp;9.4.13</a>: Precondition Failed
753       | "413"  ; <a href="#status.413" id="rfc.xref.status.413.1" title="413 Request Entity Too Large">Section&nbsp;9.4.14</a>: Request Entity Too Large
754       | "414"  ; <a href="#status.414" id="rfc.xref.status.414.1" title="414 Request-URI Too Long">Section&nbsp;9.4.15</a>: Request-URI Too Large
755       | "415"  ; <a href="#status.415" id="rfc.xref.status.415.1" title="415 Unsupported Media Type">Section&nbsp;9.4.16</a>: Unsupported Media Type
756       | "416"  ; <a href="#status.416" id="rfc.xref.status.416.1" title="416 Requested Range Not Satisfiable">Section&nbsp;9.4.17</a>: Requested range not satisfiable
757       | "417"  ; <a href="#status.417" id="rfc.xref.status.417.1" title="417 Expectation Failed">Section&nbsp;9.4.18</a>: Expectation Failed
758       | "500"  ; <a href="#status.500" id="rfc.xref.status.500.1" title="500 Internal Server Error">Section&nbsp;9.5.1</a>: Internal Server Error
759       | "501"  ; <a href="#status.501" id="rfc.xref.status.501.1" title="501 Not Implemented">Section&nbsp;9.5.2</a>: Not Implemented
760       | "502"  ; <a href="#status.502" id="rfc.xref.status.502.1" title="502 Bad Gateway">Section&nbsp;9.5.3</a>: Bad Gateway
761       | "503"  ; <a href="#status.503" id="rfc.xref.status.503.1" title="503 Service Unavailable">Section&nbsp;9.5.4</a>: Service Unavailable
762       | "504"  ; <a href="#status.504" id="rfc.xref.status.504.1" title="504 Gateway Timeout">Section&nbsp;9.5.5</a>: Gateway Time-out
763       | "505"  ; <a href="#status.505" id="rfc.xref.status.505.1" title="505 HTTP Version Not Supported">Section&nbsp;9.5.6</a>: HTTP Version not supported
764       | extension-code
766  extension-code = 3DIGIT
767  Reason-Phrase  = *&lt;TEXT, excluding CR, LF&gt;
768</pre><p id="rfc.section.5.p.4">HTTP status codes are extensible. HTTP applications are not required to understand the meaning of all registered status codes,
769            though such understanding is obviously desirable. However, applications <em class="bcp14">MUST</em> understand the class of any status code, as indicated by the first digit, and treat any unrecognized response as being equivalent
770            to the x00 status code of that class, with the exception that an unrecognized response <em class="bcp14">MUST NOT</em> be cached. For example, if an unrecognized status code of 431 is received by the client, it can safely assume that there was
771            something wrong with its request and treat the response as if it had received a 400 status code. In such cases, user agents <em class="bcp14">SHOULD</em> present to the user the entity returned with the response, since that entity is likely to include human-readable information
772            which will explain the unusual status.
773         </p>
774      </div>
775      <div id="response.header.fields">
776         <h1 id="rfc.section.6"><a href="#rfc.section.6">6.</a>&nbsp;<a href="#response.header.fields">Response Header Fields</a></h1>
777         <p id="rfc.section.6.p.1">The response-header fields allow the server to pass additional information about the response which cannot be placed in the
778            Status-Line. These header fields give information about the server and about further access to the resource identified by
779            the Request-URI.
780         </p>
781         <div id="rfc.figure.u.12"></div><pre class="inline"><span id="rfc.iref.g.7"></span>  response-header = Accept-Ranges           ; <a href="#Part5" id="rfc.xref.Part5.6"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>, <a href="p5-range.html#header.accept-ranges" title="Accept-Ranges">Section 6.1</a>
782                  | Age                     ; <a href="#Part6" id="rfc.xref.Part6.3"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>, <a href="p6-cache.html#header.age" title="Age">Section 16.1</a>
783                  | ETag                    ; <a href="#Part4" id="rfc.xref.Part4.10"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>, <a href="p4-conditional.html#header.etag" title="ETag">Section 7.1</a>
784                  | Location                ; <a href="#header.location" id="rfc.xref.header.location.1" title="Location">Section&nbsp;10.4</a>
785                  | Proxy-Authenticate      ; <a href="#Part7" id="rfc.xref.Part7.7"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a>, <a href="p7-auth.html#header.proxy-authenticate" title="Proxy-Authenticate">Section 4.2</a>
786                  | Retry-After             ; <a href="#header.retry-after" id="rfc.xref.header.retry-after.1" title="Retry-After">Section&nbsp;10.7</a>
787                  | Server                  ; <a href="#header.server" id="rfc.xref.header.server.1" title="Server">Section&nbsp;10.8</a>
788                  | Vary                    ; <a href="#Part6" id="rfc.xref.Part6.4"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>, <a href="p6-cache.html#header.vary" title="Vary">Section 16.5</a>
789                  | WWW-Authenticate        ; <a href="#Part7" id="rfc.xref.Part7.8"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a>, <a href="p7-auth.html#header.www-authenticate" title="WWW-Authenticate">Section 4.4</a>
790</pre><p id="rfc.section.6.p.3">Response-header field names can be extended reliably only in combination with a change in the protocol version. However, new
791            or experimental header fields <em class="bcp14">MAY</em> be given the semantics of response-header fields if all parties in the communication recognize them to be response-header
792            fields. Unrecognized header fields are treated as entity-header fields.
793         </p>
794      </div>
795      <div id="entity">
796         <h1 id="rfc.section.7"><a href="#rfc.section.7">7.</a>&nbsp;<a href="#entity">Entity</a></h1>
797         <p id="rfc.section.7.p.1">Request and Response messages <em class="bcp14">MAY</em> transfer an entity if not otherwise restricted by the request method or response status code. An entity consists of entity-header
798            fields and an entity-body, although some responses will only include the entity-headers. HTTP entity-body and entity-header
799            fields are defined in <a href="#Part3" id="rfc.xref.Part3.9"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>.
800         </p>
801         <p id="rfc.section.7.p.2">An entity-body is only present in a message when a message-body is present, as described in <a href="p1-messaging.html#message.body" title="Message Body">Section 4.3</a> of <a href="#Part1" id="rfc.xref.Part1.17"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>. The entity-body is obtained from the message-body by decoding any Transfer-Encoding that might have been applied to ensure
802            safe and proper transfer of the message.
803         </p>
804      </div>
805      <div id="method.definitions">
806         <h1 id="rfc.section.8"><a href="#rfc.section.8">8.</a>&nbsp;<a href="#method.definitions">Method Definitions</a></h1>
807         <p id="rfc.section.8.p.1">The set of common methods for HTTP/1.1 is defined below. Although this set can be expanded, additional methods cannot be assumed
808            to share the same semantics for separately extended clients and servers.
809         </p>
810         <div id="safe.and.idempotent">
811            <h2 id="rfc.section.8.1"><a href="#rfc.section.8.1">8.1</a>&nbsp;<a href="#safe.and.idempotent">Safe and Idempotent Methods</a></h2>
812            <div id="safe.methods">
813               <h3 id="rfc.section.8.1.1"><a href="#rfc.section.8.1.1">8.1.1</a>&nbsp;<a href="#safe.methods">Safe Methods</a></h3>
814               <p id="rfc.section.8.1.1.p.1">Implementors should be aware that the software represents the user in their interactions over the Internet, and should be
815                  careful to allow the user to be aware of any actions they might take which may have an unexpected significance to themselves
816                  or others.
817               </p>
818               <p id="rfc.section.8.1.1.p.2">In particular, the convention has been established that the GET and HEAD methods <em class="bcp14">SHOULD NOT</em> have the significance of taking an action other than retrieval. These methods ought to be considered "safe". This allows user
819                  agents to represent other methods, such as POST, PUT and DELETE, in a special way, so that the user is made aware of the fact
820                  that a possibly unsafe action is being requested.
821               </p>
822               <p id="rfc.section.8.1.1.p.3">Naturally, it is not possible to ensure that the server does not generate side-effects as a result of performing a GET request;
823                  in fact, some dynamic resources consider that a feature. The important distinction here is that the user did not request the
824                  side-effects, so therefore cannot be held accountable for them.
825               </p>
826            </div>
827            <div id="idempotent.methods">
828               <h3 id="rfc.section.8.1.2"><a href="#rfc.section.8.1.2">8.1.2</a>&nbsp;<a href="#idempotent.methods">Idempotent Methods</a></h3>
829               <p id="rfc.section.8.1.2.p.1">Methods can also have the property of "idempotence" in that (aside from error or expiration issues) the side-effects of N
830                  &gt; 0 identical requests is the same as for a single request. The methods GET, HEAD, PUT and DELETE share this property. Also,
831                  the methods OPTIONS and TRACE <em class="bcp14">SHOULD NOT</em> have side effects, and so are inherently idempotent.
832               </p>
833               <p id="rfc.section.8.1.2.p.2">However, it is possible that a sequence of several requests is non-idempotent, even if all of the methods executed in that
834                  sequence are idempotent. (A sequence is idempotent if a single execution of the entire sequence always yields a result that
835                  is not changed by a reexecution of all, or part, of that sequence.) For example, a sequence is non-idempotent if its result
836                  depends on a value that is later modified in the same sequence.
837               </p>
838               <p id="rfc.section.8.1.2.p.3">A sequence that never has side effects is idempotent, by definition (provided that no concurrent operations are being executed
839                  on the same set of resources).
840               </p>
841            </div>
842         </div>
843         <div id="OPTIONS">
844            <div id="rfc.iref.o.1"></div>
845            <div id="rfc.iref.m.1"></div>
846            <h2 id="rfc.section.8.2"><a href="#rfc.section.8.2">8.2</a>&nbsp;<a href="#OPTIONS">OPTIONS</a></h2>
847            <p id="rfc.section.8.2.p.1">The OPTIONS method represents a request for information about the communication options available on the request/response
848               chain identified by the Request-URI. This method allows the client to determine the options and/or requirements associated
849               with a resource, or the capabilities of a server, without implying a resource action or initiating a resource retrieval.
850            </p>
851            <p id="rfc.section.8.2.p.2">Responses to this method are not cacheable.</p>
852            <p id="rfc.section.8.2.p.3">If the OPTIONS request includes an entity-body (as indicated by the presence of Content-Length or Transfer-Encoding), then
853               the media type <em class="bcp14">MUST</em> be indicated by a Content-Type field. Although this specification does not define any use for such a body, future extensions
854               to HTTP might use the OPTIONS body to make more detailed queries on the server. A server that does not support such an extension <em class="bcp14">MAY</em> discard the request body.
855            </p>
856            <p id="rfc.section.8.2.p.4">If the Request-URI is an asterisk ("*"), the OPTIONS request is intended to apply to the server in general rather than to
857               a specific resource. Since a server's communication options typically depend on the resource, the "*" request is only useful
858               as a "ping" or "no-op" type of method; it does nothing beyond allowing the client to test the capabilities of the server.
859               For example, this can be used to test a proxy for HTTP/1.1 compliance (or lack thereof).
860            </p>
861            <p id="rfc.section.8.2.p.5">If the Request-URI is not an asterisk, the OPTIONS request applies only to the options that are available when communicating
862               with that resource.
863            </p>
864            <p id="rfc.section.8.2.p.6">A 200 response <em class="bcp14">SHOULD</em> include any header fields that indicate optional features implemented by the server and applicable to that resource (e.g.,
865               Allow), possibly including extensions not defined by this specification. The response body, if any, <em class="bcp14">SHOULD</em> also include information about the communication options. The format for such a body is not defined by this specification,
866               but might be defined by future extensions to HTTP. Content negotiation <em class="bcp14">MAY</em> be used to select the appropriate response format. If no response body is included, the response <em class="bcp14">MUST</em> include a Content-Length field with a field-value of "0".
867            </p>
868            <p id="rfc.section.8.2.p.7">The Max-Forwards request-header field <em class="bcp14">MAY</em> be used to target a specific proxy in the request chain. When a proxy receives an OPTIONS request on an absoluteURI for which
869               request forwarding is permitted, the proxy <em class="bcp14">MUST</em> check for a Max-Forwards field. If the Max-Forwards field-value is zero ("0"), the proxy <em class="bcp14">MUST NOT</em> forward the message; instead, the proxy <em class="bcp14">SHOULD</em> respond with its own communication options. If the Max-Forwards field-value is an integer greater than zero, the proxy <em class="bcp14">MUST</em> decrement the field-value when it forwards the request. If no Max-Forwards field is present in the request, then the forwarded
870               request <em class="bcp14">MUST NOT</em> include a Max-Forwards field.
871            </p>
872         </div>
873         <div id="GET">
874            <div id="rfc.iref.g.8"></div>
875            <div id="rfc.iref.m.2"></div>
876            <h2 id="rfc.section.8.3"><a href="#rfc.section.8.3">8.3</a>&nbsp;<a href="#GET">GET</a></h2>
877            <p id="rfc.section.8.3.p.1">The GET method means retrieve whatever information (in the form of an entity) is identified by the Request-URI. If the Request-URI
878               refers to a data-producing process, it is the produced data which shall be returned as the entity in the response and not
879               the source text of the process, unless that text happens to be the output of the process.
880            </p>
881            <p id="rfc.section.8.3.p.2">The semantics of the GET method change to a "conditional GET" if the request message includes an If-Modified-Since, If-Unmodified-Since,
882               If-Match, If-None-Match, or If-Range header field. A conditional GET method requests that the entity be transferred only under
883               the circumstances described by the conditional header field(s). The conditional GET method is intended to reduce unnecessary
884               network usage by allowing cached entities to be refreshed without requiring multiple requests or transferring data already
885               held by the client.
886            </p>
887            <p id="rfc.section.8.3.p.3">The semantics of the GET method change to a "partial GET" if the request message includes a Range header field. A partial
888               GET requests that only part of the entity be transferred, as described in <a href="p5-range.html#header.range" title="Range">Section 6.4</a> of <a href="#Part5" id="rfc.xref.Part5.7"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>. The partial GET method is intended to reduce unnecessary network usage by allowing partially-retrieved entities to be completed
889               without transferring data already held by the client.
890            </p>
891            <p id="rfc.section.8.3.p.4">The response to a GET request is cacheable if and only if it meets the requirements for HTTP caching described in <a href="#Part6" id="rfc.xref.Part6.5"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>.
892            </p>
893            <p id="rfc.section.8.3.p.5">See <a href="" title="Encoding Sensitive Information in URIs">Section&nbsp;12.2</a> for security considerations when used for forms.
894            </p>
895         </div>
896         <div id="HEAD">
897            <div id="rfc.iref.h.1"></div>
898            <div id="rfc.iref.m.3"></div>
899            <h2 id="rfc.section.8.4"><a href="#rfc.section.8.4">8.4</a>&nbsp;<a href="#HEAD">HEAD</a></h2>
900            <p id="rfc.section.8.4.p.1">The HEAD method is identical to GET except that the server <em class="bcp14">MUST NOT</em> return a message-body in the response. The metainformation contained in the HTTP headers in response to a HEAD request <em class="bcp14">SHOULD</em> be identical to the information sent in response to a GET request. This method can be used for obtaining metainformation about
901               the entity implied by the request without transferring the entity-body itself. This method is often used for testing hypertext
902               links for validity, accessibility, and recent modification.
903            </p>
904            <p id="rfc.section.8.4.p.2">The response to a HEAD request <em class="bcp14">MAY</em> be cacheable in the sense that the information contained in the response <em class="bcp14">MAY</em> be used to update a previously cached entity from that resource. If the new field values indicate that the cached entity differs
905               from the current entity (as would be indicated by a change in Content-Length, Content-MD5, ETag or Last-Modified), then the
906               cache <em class="bcp14">MUST</em> treat the cache entry as stale.
907            </p>
908         </div>
909         <div id="POST">
910            <div id="rfc.iref.p.1"></div>
911            <div id="rfc.iref.m.4"></div>
912            <h2 id="rfc.section.8.5"><a href="#rfc.section.8.5">8.5</a>&nbsp;<a href="#POST">POST</a></h2>
913            <p id="rfc.section.8.5.p.1">The POST method is used to request that the origin server accept the entity enclosed in the request as data to be processed
914               by the resource identified by the Request-URI in the Request-Line. POST is designed to allow a uniform method to cover the
915               following functions:
916            </p>
917            <ul>
918               <li>Annotation of existing resources;</li>
919               <li>Posting a message to a bulletin board, newsgroup, mailing list, or similar group of articles;</li>
920               <li>Providing a block of data, such as the result of submitting a form, to a data-handling process;</li>
921               <li>Extending a database through an append operation.</li>
922            </ul>
923            <p id="rfc.section.8.5.p.2">The actual function performed by the POST method is determined by the server and is usually dependent on the Request-URI.</p>
924            <p id="rfc.section.8.5.p.3">The action performed by the POST method might not result in a resource that can be identified by a URI. In this case, either
925               200 (OK) or 204 (No Content) is the appropriate response status, depending on whether or not the response includes an entity
926               that describes the result.
927            </p>
928            <p id="rfc.section.8.5.p.4">If a resource has been created on the origin server, the response <em class="bcp14">SHOULD</em> be 201 (Created) and contain an entity which describes the status of the request and refers to the new resource, and a Location
929               header (see <a href="#header.location" id="rfc.xref.header.location.2" title="Location">Section&nbsp;10.4</a>).
930            </p>
931            <p id="rfc.section.8.5.p.5">Responses to this method are not cacheable, unless the response includes appropriate Cache-Control or Expires header fields.
932               However, the 303 (See Other) response can be used to direct the user agent to retrieve a cacheable resource.
933            </p>
934         </div>
935         <div id="PUT">
936            <div id="rfc.iref.p.2"></div>
937            <div id="rfc.iref.m.5"></div>
938            <h2 id="rfc.section.8.6"><a href="#rfc.section.8.6">8.6</a>&nbsp;<a href="#PUT">PUT</a></h2>
939            <p id="rfc.section.8.6.p.1">The PUT method requests that the enclosed entity be stored under the supplied Request-URI. If the Request-URI refers to an
940               already existing resource, the enclosed entity <em class="bcp14">SHOULD</em> be considered as a modified version of the one residing on the origin server. If the Request-URI does not point to an existing
941               resource, and that URI is capable of being defined as a new resource by the requesting user agent, the origin server can create
942               the resource with that URI. If a new resource is created at the Request-URI, the origin server <em class="bcp14">MUST</em> inform the user agent via the 201 (Created) response. If an existing resource is modified, either the 200 (OK) or 204 (No
943               Content) response codes <em class="bcp14">SHOULD</em> be sent to indicate successful completion of the request. If the resource could not be created or modified with the Request-URI,
944               an appropriate error response <em class="bcp14">SHOULD</em> be given that reflects the nature of the problem. The recipient of the entity <em class="bcp14">MUST NOT</em> ignore any Content-* (e.g. Content-Range) headers that it does not understand or implement and <em class="bcp14">MUST</em> return a 501 (Not Implemented) response in such cases.
945            </p>
946            <p id="rfc.section.8.6.p.2">If the request passes through a cache and the Request-URI identifies one or more currently cached entities, those entries <em class="bcp14">SHOULD</em> be treated as stale. Responses to this method are not cacheable.
947            </p>
948            <p id="rfc.section.8.6.p.3">The fundamental difference between the POST and PUT requests is reflected in the different meaning of the Request-URI. The
949               URI in a POST request identifies the resource that will handle the enclosed entity. That resource might be a data-accepting
950               process, a gateway to some other protocol, or a separate entity that accepts annotations. In contrast, the URI in a PUT request
951               identifies the entity enclosed with the request -- the user agent knows what URI is intended and the server <em class="bcp14">MUST NOT</em> attempt to apply the request to some other resource. If the server desires that the request be applied to a different URI,
952               it <em class="bcp14">MUST</em> send a 301 (Moved Permanently) response; the user agent <em class="bcp14">MAY</em> then make its own decision regarding whether or not to redirect the request.
953            </p>
954            <p id="rfc.section.8.6.p.4">A single resource <em class="bcp14">MAY</em> be identified by many different URIs. For example, an article might have a URI for identifying "the current version" which
955               is separate from the URI identifying each particular version. In this case, a PUT request on a general URI might result in
956               several other URIs being defined by the origin server.
957            </p>
958            <p id="rfc.section.8.6.p.5">HTTP/1.1 does not define how a PUT method affects the state of an origin server.</p>
959            <p id="rfc.section.8.6.p.6">Unless otherwise specified for a particular entity-header, the entity-headers in the PUT request <em class="bcp14">SHOULD</em> be applied to the resource created or modified by the PUT.
960            </p>
961         </div>
962         <div id="DELETE">
963            <div id="rfc.iref.d.1"></div>
964            <div id="rfc.iref.m.6"></div>
965            <h2 id="rfc.section.8.7"><a href="#rfc.section.8.7">8.7</a>&nbsp;<a href="#DELETE">DELETE</a></h2>
966            <p id="rfc.section.8.7.p.1">The DELETE method requests that the origin server delete the resource identified by the Request-URI. This method <em class="bcp14">MAY</em> be overridden by human intervention (or other means) on the origin server. The client cannot be guaranteed that the operation
967               has been carried out, even if the status code returned from the origin server indicates that the action has been completed
968               successfully. However, the server <em class="bcp14">SHOULD NOT</em> indicate success unless, at the time the response is given, it intends to delete the resource or move it to an inaccessible
969               location.
970            </p>
971            <p id="rfc.section.8.7.p.2">A successful response <em class="bcp14">SHOULD</em> be 200 (OK) if the response includes an entity describing the status, 202 (Accepted) if the action has not yet been enacted,
972               or 204 (No Content) if the action has been enacted but the response does not include an entity.
973            </p>
974            <p id="rfc.section.8.7.p.3">If the request passes through a cache and the Request-URI identifies one or more currently cached entities, those entries <em class="bcp14">SHOULD</em> be treated as stale. Responses to this method are not cacheable.
975            </p>
976         </div>
977         <div id="TRACE">
978            <div id="rfc.iref.t.1"></div>
979            <div id="rfc.iref.m.7"></div>
980            <h2 id="rfc.section.8.8"><a href="#rfc.section.8.8">8.8</a>&nbsp;<a href="#TRACE">TRACE</a></h2>
981            <p id="rfc.section.8.8.p.1">The TRACE method is used to invoke a remote, application-layer loop-back of the request message. The final recipient of the
982               request <em class="bcp14">SHOULD</em> reflect the message received back to the client as the entity-body of a 200 (OK) response. The final recipient is either the
983               origin server or the first proxy or gateway to receive a Max-Forwards value of zero (0) in the request (see <a href="#header.max-forwards" id="rfc.xref.header.max-forwards.2" title="Max-Forwards">Section&nbsp;10.5</a>). A TRACE request <em class="bcp14">MUST NOT</em> include an entity.
984            </p>
985            <p id="rfc.section.8.8.p.2">TRACE allows the client to see what is being received at the other end of the request chain and use that data for testing
986               or diagnostic information. The value of the Via header field (<a href="p1-messaging.html#header.via" title="Via">Section 8.9</a> of <a href="#Part1" id="rfc.xref.Part1.18"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) is of particular interest, since it acts as a trace of the request chain. Use of the Max-Forwards header field allows the
987               client to limit the length of the request chain, which is useful for testing a chain of proxies forwarding messages in an
988               infinite loop.
989            </p>
990            <p id="rfc.section.8.8.p.3">If the request is valid, the response <em class="bcp14">SHOULD</em> contain the entire request message in the entity-body, with a Content-Type of "message/http". Responses to this method <em class="bcp14">MUST NOT</em> be cached.
991            </p>
992         </div>
993         <div id="CONNECT">
994            <div id="rfc.iref.c.1"></div>
995            <div id="rfc.iref.m.8"></div>
996            <h2 id="rfc.section.8.9"><a href="#rfc.section.8.9">8.9</a>&nbsp;<a href="#CONNECT">CONNECT</a></h2>
997            <p id="rfc.section.8.9.p.1">This specification reserves the method name CONNECT for use with a proxy that can dynamically switch to being a tunnel (e.g.
998               SSL tunneling <a href="#Luo1998" id="rfc.xref.Luo1998.1"><cite title="Tunneling TCP based protocols through Web proxy servers">[Luo1998]</cite></a>).
999            </p>
1000         </div>
1001      </div>
1002      <div id="">
1003         <h1 id="rfc.section.9"><a href="#rfc.section.9">9.</a>&nbsp;<a href="">Status Code Definitions</a></h1>
1004         <p id="rfc.section.9.p.1">Each Status-Code is described below, including a description of which method(s) it can follow and any metainformation required
1005            in the response.
1006         </p>
1007         <div id="status.1xx">
1008            <h2 id="rfc.section.9.1"><a href="#rfc.section.9.1">9.1</a>&nbsp;<a href="#status.1xx">Informational 1xx</a></h2>
1009            <p id="rfc.section.9.1.p.1">This class of status code indicates a provisional response, consisting only of the Status-Line and optional headers, and is
1010               terminated by an empty line. There are no required headers for this class of status code. Since HTTP/1.0 did not define any
1011               1xx status codes, servers <em class="bcp14">MUST NOT</em> send a 1xx response to an HTTP/1.0 client except under experimental conditions.
1012            </p>
1013            <p id="rfc.section.9.1.p.2">A client <em class="bcp14">MUST</em> be prepared to accept one or more 1xx status responses prior to a regular response, even if the client does not expect a 100
1014               (Continue) status message. Unexpected 1xx status responses <em class="bcp14">MAY</em> be ignored by a user agent.
1015            </p>
1016            <p id="rfc.section.9.1.p.3">Proxies <em class="bcp14">MUST</em> forward 1xx responses, unless the connection between the proxy and its client has been closed, or unless the proxy itself
1017               requested the generation of the 1xx response. (For example, if a proxy adds a "Expect: 100-continue" field when it forwards
1018               a request, then it need not forward the corresponding 100 (Continue) response(s).)
1019            </p>
1020            <div id="status.100">
1021               <div id="rfc.iref.1.1"></div>
1022               <div id="rfc.iref.s.1"></div>
1023               <h3 id="rfc.section.9.1.1"><a href="#rfc.section.9.1.1">9.1.1</a>&nbsp;<a href="#status.100">100 Continue</a></h3>
1024               <p id="rfc.section.9.1.1.p.1">The client <em class="bcp14">SHOULD</em> continue with its request. This interim response is used to inform the client that the initial part of the request has been
1025                  received and has not yet been rejected by the server. The client <em class="bcp14">SHOULD</em> continue by sending the remainder of the request or, if the request has already been completed, ignore this response. The
1026                  server <em class="bcp14">MUST</em> send a final response after the request has been completed. See <a href="p1-messaging.html#use.of.the.100.status" title="Use of the 100 (Continue) Status">Section 7.2.3</a> of <a href="#Part1" id="rfc.xref.Part1.19"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a> for detailed discussion of the use and handling of this status code.
1027               </p>
1028            </div>
1029            <div id="status.101">
1030               <div id="rfc.iref.1.2"></div>
1031               <div id="rfc.iref.s.2"></div>
1032               <h3 id="rfc.section.9.1.2"><a href="#rfc.section.9.1.2">9.1.2</a>&nbsp;<a href="#status.101">101 Switching Protocols</a></h3>
1033               <p id="rfc.section.9.1.2.p.1">The server understands and is willing to comply with the client's request, via the Upgrade message header field (<a href="p5-range.html#header.range" title="Range">Section 6.4</a> of <a href="#Part5" id="rfc.xref.Part5.8"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>), for a change in the application protocol being used on this connection. The server will switch protocols to those defined
1034                  by the response's Upgrade header field immediately after the empty line which terminates the 101 response.
1035               </p>
1036               <p id="rfc.section.9.1.2.p.2">The protocol <em class="bcp14">SHOULD</em> be switched only when it is advantageous to do so. For example, switching to a newer version of HTTP is advantageous over
1037                  older versions, and switching to a real-time, synchronous protocol might be advantageous when delivering resources that use
1038                  such features.
1039               </p>
1040            </div>
1041         </div>
1042         <div id="status.2xx">
1043            <h2 id="rfc.section.9.2"><a href="#rfc.section.9.2">9.2</a>&nbsp;<a href="#status.2xx">Successful 2xx</a></h2>
1044            <p id="rfc.section.9.2.p.1">This class of status code indicates that the client's request was successfully received, understood, and accepted.</p>
1045            <div id="status.200">
1046               <div id="rfc.iref.2.1"></div>
1047               <div id="rfc.iref.s.3"></div>
1048               <h3 id="rfc.section.9.2.1"><a href="#rfc.section.9.2.1">9.2.1</a>&nbsp;<a href="#status.200">200 OK</a></h3>
1049               <p id="rfc.section.9.2.1.p.1">The request has succeeded. The information returned with the response is dependent on the method used in the request, for
1050                  example:
1051               </p>
1052               <dl>
1053                  <dt>GET</dt>
1054                  <dd>an entity corresponding to the requested resource is sent in the response;</dd>
1055                  <dt>HEAD</dt>
1056                  <dd>the entity-header fields corresponding to the requested resource are sent in the response without any message-body;</dd>
1057                  <dt>POST</dt>
1058                  <dd>an entity describing or containing the result of the action;</dd>
1059                  <dt>TRACE</dt>
1060                  <dd>an entity containing the request message as received by the end server.</dd>
1061               </dl>
1062            </div>
1063            <div id="status.201">
1064               <div id="rfc.iref.2.2"></div>
1065               <div id="rfc.iref.s.4"></div>
1066               <h3 id="rfc.section.9.2.2"><a href="#rfc.section.9.2.2">9.2.2</a>&nbsp;<a href="#status.201">201 Created</a></h3>
1067               <p id="rfc.section.9.2.2.p.1">The request has been fulfilled and resulted in a new resource being created. The newly created resource can be referenced
1068                  by the URI(s) returned in the entity of the response, with the most specific URI for the resource given by a Location header
1069                  field. The response <em class="bcp14">SHOULD</em> include an entity containing a list of resource characteristics and location(s) from which the user or user agent can choose
1070                  the one most appropriate. The entity format is specified by the media type given in the Content-Type header field. The origin
1071                  server <em class="bcp14">MUST</em> create the resource before returning the 201 status code. If the action cannot be carried out immediately, the server <em class="bcp14">SHOULD</em> respond with 202 (Accepted) response instead.
1072               </p>
1073               <p id="rfc.section.9.2.2.p.2">A 201 response <em class="bcp14">MAY</em> contain an ETag response header field indicating the current value of the entity tag for the requested variant just created,
1074                  see <a href="p4-conditional.html#header.etag" title="ETag">Section 7.1</a> of <a href="#Part4" id="rfc.xref.Part4.11"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>.
1075               </p>
1076            </div>
1077            <div id="status.202">
1078               <div id="rfc.iref.2.3"></div>
1079               <div id="rfc.iref.s.5"></div>
1080               <h3 id="rfc.section.9.2.3"><a href="#rfc.section.9.2.3">9.2.3</a>&nbsp;<a href="#status.202">202 Accepted</a></h3>
1081               <p id="rfc.section.9.2.3.p.1">The request has been accepted for processing, but the processing has not been completed. The request might or might not eventually
1082                  be acted upon, as it might be disallowed when processing actually takes place. There is no facility for re-sending a status
1083                  code from an asynchronous operation such as this.
1084               </p>
1085               <p id="rfc.section.9.2.3.p.2">The 202 response is intentionally non-committal. Its purpose is to allow a server to accept a request for some other process
1086                  (perhaps a batch-oriented process that is only run once per day) without requiring that the user agent's connection to the
1087                  server persist until the process is completed. The entity returned with this response <em class="bcp14">SHOULD</em> include an indication of the request's current status and either a pointer to a status monitor or some estimate of when the
1088                  user can expect the request to be fulfilled.
1089               </p>
1090            </div>
1091            <div id="status.203">
1092               <div id="rfc.iref.2.4"></div>
1093               <div id="rfc.iref.s.6"></div>
1094               <h3 id="rfc.section.9.2.4"><a href="#rfc.section.9.2.4">9.2.4</a>&nbsp;<a href="#status.203">203 Non-Authoritative Information</a></h3>
1095               <p id="rfc.section.9.2.4.p.1">The returned metainformation in the entity-header is not the definitive set as available from the origin server, but is gathered
1096                  from a local or a third-party copy. The set presented <em class="bcp14">MAY</em> be a subset or superset of the original version. For example, including local annotation information about the resource might
1097                  result in a superset of the metainformation known by the origin server. Use of this response code is not required and is only
1098                  appropriate when the response would otherwise be 200 (OK).
1099               </p>
1100            </div>
1101            <div id="status.204">
1102               <div id="rfc.iref.2.5"></div>
1103               <div id="rfc.iref.s.7"></div>
1104               <h3 id="rfc.section.9.2.5"><a href="#rfc.section.9.2.5">9.2.5</a>&nbsp;<a href="#status.204">204 No Content</a></h3>
1105               <p id="rfc.section.9.2.5.p.1">The server has fulfilled the request but does not need to return an entity-body, and might want to return updated metainformation.
1106                  The response <em class="bcp14">MAY</em> include new or updated metainformation in the form of entity-headers, which if present <em class="bcp14">SHOULD</em> be associated with the requested variant.
1107               </p>
1108               <p id="rfc.section.9.2.5.p.2">If the client is a user agent, it <em class="bcp14">SHOULD NOT</em> change its document view from that which caused the request to be sent. This response is primarily intended to allow input
1109                  for actions to take place without causing a change to the user agent's active document view, although any new or updated metainformation <em class="bcp14">SHOULD</em> be applied to the document currently in the user agent's active view.
1110               </p>
1111               <p id="rfc.section.9.2.5.p.3">The 204 response <em class="bcp14">MUST NOT</em> include a message-body, and thus is always terminated by the first empty line after the header fields.
1112               </p>
1113            </div>
1114            <div id="status.205">
1115               <div id="rfc.iref.2.6"></div>
1116               <div id="rfc.iref.s.8"></div>
1117               <h3 id="rfc.section.9.2.6"><a href="#rfc.section.9.2.6">9.2.6</a>&nbsp;<a href="#status.205">205 Reset Content</a></h3>
1118               <p id="rfc.section.9.2.6.p.1">The server has fulfilled the request and the user agent <em class="bcp14">SHOULD</em> reset the document view which caused the request to be sent. This response is primarily intended to allow input for actions
1119                  to take place via user input, followed by a clearing of the form in which the input is given so that the user can easily initiate
1120                  another input action. The response <em class="bcp14">MUST NOT</em> include an entity.
1121               </p>
1122            </div>
1123            <div id="status.206">
1124               <div id="rfc.iref.2.7"></div>
1125               <div id="rfc.iref.s.9"></div>
1126               <h3 id="rfc.section.9.2.7"><a href="#rfc.section.9.2.7">9.2.7</a>&nbsp;<a href="#status.206">206 Partial Content</a></h3>
1127               <p id="rfc.section.9.2.7.p.1">The server has fulfilled the partial GET request for the resource and the enclosed entity is a partial representation as defined
1128                  in <a href="#Part5" id="rfc.xref.Part5.9"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>.
1129               </p>
1130            </div>
1131         </div>
1132         <div id="status.3xx">
1133            <h2 id="rfc.section.9.3"><a href="#rfc.section.9.3">9.3</a>&nbsp;<a href="#status.3xx">Redirection 3xx</a></h2>
1134            <p id="rfc.section.9.3.p.1">This class of status code indicates that further action needs to be taken by the user agent in order to fulfill the request.
1135               The action required <em class="bcp14">MAY</em> be carried out by the user agent without interaction with the user if and only if the method used in the second request is
1136               GET or HEAD. A client <em class="bcp14">SHOULD</em> detect infinite redirection loops, since such loops generate network traffic for each redirection.
1137            </p>
1138            <ul class="empty">
1139               <li><b>Note:</b> previous versions of this specification recommended a maximum of five redirections. Content developers should be aware that
1140                  there might be clients that implement such a fixed limitation.
1141               </li>
1142            </ul>
1143            <div id="status.300">
1144               <div id="rfc.iref.3.1"></div>
1145               <div id="rfc.iref.s.10"></div>
1146               <h3 id="rfc.section.9.3.1"><a href="#rfc.section.9.3.1">9.3.1</a>&nbsp;<a href="#status.300">300 Multiple Choices</a></h3>
1147               <p id="rfc.section.9.3.1.p.1">The requested resource corresponds to any one of a set of representations, each with its own specific location, and agent-driven
1148                  negotiation information (<a href="p3-payload.html#content.negotiation" title="Content Negotiation">Section 5</a> of <a href="#Part3" id="rfc.xref.Part3.10"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>) is being provided so that the user (or user agent) can select a preferred representation and redirect its request to that
1149                  location.
1150               </p>
1151               <p id="rfc.section.9.3.1.p.2">Unless it was a HEAD request, the response <em class="bcp14">SHOULD</em> include an entity containing a list of resource characteristics and location(s) from which the user or user agent can choose
1152                  the one most appropriate. The entity format is specified by the media type given in the Content-Type header field. Depending
1153                  upon the format and the capabilities of the user agent, selection of the most appropriate choice <em class="bcp14">MAY</em> be performed automatically. However, this specification does not define any standard for such automatic selection.
1154               </p>
1155               <p id="rfc.section.9.3.1.p.3">If the server has a preferred choice of representation, it <em class="bcp14">SHOULD</em> include the specific URI for that representation in the Location field; user agents <em class="bcp14">MAY</em> use the Location field value for automatic redirection. This response is cacheable unless indicated otherwise.
1156               </p>
1157            </div>
1158            <div id="status.301">
1159               <div id="rfc.iref.3.2"></div>
1160               <div id="rfc.iref.s.11"></div>
1161               <h3 id="rfc.section.9.3.2"><a href="#rfc.section.9.3.2">9.3.2</a>&nbsp;<a href="#status.301">301 Moved Permanently</a></h3>
1162               <p id="rfc.section.9.3.2.p.1">The requested resource has been assigned a new permanent URI and any future references to this resource <em class="bcp14">SHOULD</em> use one of the returned URIs. Clients with link editing capabilities ought to automatically re-link references to the Request-URI
1163                  to one or more of the new references returned by the server, where possible. This response is cacheable unless indicated otherwise.
1164               </p>
1165               <p id="rfc.section.9.3.2.p.2">The new permanent URI <em class="bcp14">SHOULD</em> be given by the Location field in the response. Unless the request method was HEAD, the entity of the response <em class="bcp14">SHOULD</em> contain a short hypertext note with a hyperlink to the new URI(s).
1166               </p>
1167               <p id="rfc.section.9.3.2.p.3">If the 301 status code is received in response to a request method that is known to be "safe", as defined in <a href="#safe.methods" title="Safe Methods">Section&nbsp;8.1.1</a>, then the request <em class="bcp14">MAY</em> be automatically redirected by the user agent without confirmation. Otherwise, the user agent <em class="bcp14">MUST NOT</em> automatically redirect the request unless it can be confirmed by the user, since this might change the conditions under which
1168                  the request was issued.
1169               </p>
1170               <ul class="empty">
1171                  <li><b>Note:</b> When automatically redirecting a POST request after receiving a 301 status code, some existing HTTP/1.0 user agents will erroneously
1172                     change it into a GET request.
1173                  </li>
1174               </ul>
1175            </div>
1176            <div id="status.302">
1177               <div id="rfc.iref.3.3"></div>
1178               <div id="rfc.iref.s.12"></div>
1179               <h3 id="rfc.section.9.3.3"><a href="#rfc.section.9.3.3">9.3.3</a>&nbsp;<a href="#status.302">302 Found</a></h3>
1180               <p id="rfc.section.9.3.3.p.1">The requested resource resides temporarily under a different URI. Since the redirection might be altered on occasion, the
1181                  client <em class="bcp14">SHOULD</em> continue to use the Request-URI for future requests. This response is only cacheable if indicated by a Cache-Control or Expires
1182                  header field.
1183               </p>
1184               <p id="rfc.section.9.3.3.p.2">The temporary URI <em class="bcp14">SHOULD</em> be given by the Location field in the response. Unless the request method was HEAD, the entity of the response <em class="bcp14">SHOULD</em> contain a short hypertext note with a hyperlink to the new URI(s).
1185               </p>
1186               <p id="rfc.section.9.3.3.p.3">If the 302 status code is received in response to a request method that is known to be "safe", as defined in <a href="#safe.methods" title="Safe Methods">Section&nbsp;8.1.1</a>, then the request <em class="bcp14">MAY</em> be automatically redirected by the user agent without confirmation. Otherwise, the user agent <em class="bcp14">MUST NOT</em> automatically redirect the request unless it can be confirmed by the user, since this might change the conditions under which
1187                  the request was issued.
1188               </p>
1189               <ul class="empty">
1190                  <li><b>Note:</b> <a href="#RFC1945" id="rfc.xref.RFC1945.1"><cite title="Hypertext Transfer Protocol -- HTTP/1.0">[RFC1945]</cite></a> and <a href="#RFC2068" id="rfc.xref.RFC2068.1"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2068]</cite></a> specify that the client is not allowed to change the method on the redirected request. However, most existing user agent implementations
1191                     treat 302 as if it were a 303 response, performing a GET on the Location field-value regardless of the original request method.
1192                     The status codes 303 and 307 have been added for servers that wish to make unambiguously clear which kind of reaction is expected
1193                     of the client.
1194                  </li>
1195               </ul>
1196            </div>
1197            <div id="status.303">
1198               <div id="rfc.iref.3.4"></div>
1199               <div id="rfc.iref.s.13"></div>
1200               <h3 id="rfc.section.9.3.4"><a href="#rfc.section.9.3.4">9.3.4</a>&nbsp;<a href="#status.303">303 See Other</a></h3>
1201               <p id="rfc.section.9.3.4.p.1">The response to the request can be found under a different URI and <em class="bcp14">SHOULD</em> be retrieved using a GET method on that resource. This method exists primarily to allow the output of a POST-activated script
1202                  to redirect the user agent to a selected resource. The new URI is not a substitute reference for the originally requested
1203                  resource. The 303 response <em class="bcp14">MUST NOT</em> be cached, but the response to the second (redirected) request might be cacheable.
1204               </p>
1205               <p id="rfc.section.9.3.4.p.2">The different URI <em class="bcp14">SHOULD</em> be given by the Location field in the response. Unless the request method was HEAD, the entity of the response <em class="bcp14">SHOULD</em> contain a short hypertext note with a hyperlink to the new URI(s).
1206               </p>
1207               <ul class="empty">
1208                  <li><b>Note:</b> Many pre-HTTP/1.1 user agents do not understand the 303 status. When interoperability with such clients is a concern, the
1209                     302 status code may be used instead, since most user agents react to a 302 response as described here for 303.
1210                  </li>
1211               </ul>
1212            </div>
1213            <div id="status.304">
1214               <div id="rfc.iref.3.5"></div>
1215               <div id="rfc.iref.s.14"></div>
1216               <h3 id="rfc.section.9.3.5"><a href="#rfc.section.9.3.5">9.3.5</a>&nbsp;<a href="#status.304">304 Not Modified</a></h3>
1217               <p id="rfc.section.9.3.5.p.1">The response to the request has not been modified since the conditions indicated by the client's conditional GET request,
1218                  as defined in <a href="#Part4" id="rfc.xref.Part4.12"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>.
1219               </p>
1220            </div>
1221            <div id="status.305">
1222               <div id="rfc.iref.3.6"></div>
1223               <div id="rfc.iref.s.15"></div>
1224               <h3 id="rfc.section.9.3.6"><a href="#rfc.section.9.3.6">9.3.6</a>&nbsp;<a href="#status.305">305 Use Proxy</a></h3>
1225               <p id="rfc.section.9.3.6.p.1">The requested resource <em class="bcp14">MUST</em> be accessed through the proxy given by the Location field. The Location field gives the URI of the proxy. The recipient is
1226                  expected to repeat this single request via the proxy. 305 responses <em class="bcp14">MUST</em> only be generated by origin servers.
1227               </p>
1228               <ul class="empty">
1229                  <li><b>Note:</b> <a href="#RFC2068" id="rfc.xref.RFC2068.2"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2068]</cite></a> was not clear that 305 was intended to redirect a single request, and to be generated by origin servers only. Not observing
1230                     these limitations has significant security consequences.
1231                  </li>
1232               </ul>
1233            </div>
1234            <div id="status.306">
1235               <div id="rfc.iref.3.7"></div>
1236               <div id="rfc.iref.s.16"></div>
1237               <h3 id="rfc.section.9.3.7"><a href="#rfc.section.9.3.7">9.3.7</a>&nbsp;<a href="#status.306">306 (Unused)</a></h3>
1238               <p id="rfc.section.9.3.7.p.1">The 306 status code was used in a previous version of the specification, is no longer used, and the code is reserved.</p>
1239            </div>
1240            <div id="status.307">
1241               <div id="rfc.iref.3.8"></div>
1242               <div id="rfc.iref.s.17"></div>
1243               <h3 id="rfc.section.9.3.8"><a href="#rfc.section.9.3.8">9.3.8</a>&nbsp;<a href="#status.307">307 Temporary Redirect</a></h3>
1244               <p id="rfc.section.9.3.8.p.1">The requested resource resides temporarily under a different URI. Since the redirection <em class="bcp14">MAY</em> be altered on occasion, the client <em class="bcp14">SHOULD</em> continue to use the Request-URI for future requests. This response is only cacheable if indicated by a Cache-Control or Expires
1245                  header field.
1246               </p>
1247               <p id="rfc.section.9.3.8.p.2">The temporary URI <em class="bcp14">SHOULD</em> be given by the Location field in the response. Unless the request method was HEAD, the entity of the response <em class="bcp14">SHOULD</em> contain a short hypertext note with a hyperlink to the new URI(s) , since many pre-HTTP/1.1 user agents do not understand
1248                  the 307 status. Therefore, the note <em class="bcp14">SHOULD</em> contain the information necessary for a user to repeat the original request on the new URI.
1249               </p>
1250               <p id="rfc.section.9.3.8.p.3">If the 307 status code is received in response to a request method that is known to be "safe", as defined in <a href="#safe.methods" title="Safe Methods">Section&nbsp;8.1.1</a>, then the request <em class="bcp14">MAY</em> be automatically redirected by the user agent without confirmation. Otherwise, the user agent <em class="bcp14">MUST NOT</em> automatically redirect the request unless it can be confirmed by the user, since this might change the conditions under which
1251                  the request was issued.
1252               </p>
1253            </div>
1254         </div>
1255         <div id="status.4xx">
1256            <h2 id="rfc.section.9.4"><a href="#rfc.section.9.4">9.4</a>&nbsp;<a href="#status.4xx">Client Error 4xx</a></h2>
1257            <p id="rfc.section.9.4.p.1">The 4xx class of status code is intended for cases in which the client seems to have erred. Except when responding to a HEAD
1258               request, the server <em class="bcp14">SHOULD</em> include an entity containing an explanation of the error situation, and whether it is a temporary or permanent condition.
1259               These status codes are applicable to any request method. User agents <em class="bcp14">SHOULD</em> display any included entity to the user.
1260            </p>
1261            <p id="rfc.section.9.4.p.2">If the client is sending data, a server implementation using TCP <em class="bcp14">SHOULD</em> be careful to ensure that the client acknowledges receipt of the packet(s) containing the response, before the server closes
1262               the input connection. If the client continues sending data to the server after the close, the server's TCP stack will send
1263               a reset packet to the client, which may erase the client's unacknowledged input buffers before they can be read and interpreted
1264               by the HTTP application.
1265            </p>
1266            <div id="status.400">
1267               <div id="rfc.iref.4.1"></div>
1268               <div id="rfc.iref.s.18"></div>
1269               <h3 id="rfc.section.9.4.1"><a href="#rfc.section.9.4.1">9.4.1</a>&nbsp;<a href="#status.400">400 Bad Request</a></h3>
1270               <p id="rfc.section.9.4.1.p.1">The request could not be understood by the server due to malformed syntax. The client <em class="bcp14">SHOULD NOT</em> repeat the request without modifications.
1271               </p>
1272            </div>
1273            <div id="status.401">
1274               <div id="rfc.iref.4.2"></div>
1275               <div id="rfc.iref.s.19"></div>
1276               <h3 id="rfc.section.9.4.2"><a href="#rfc.section.9.4.2">9.4.2</a>&nbsp;<a href="#status.401">401 Unauthorized</a></h3>
1277               <p id="rfc.section.9.4.2.p.1">The request requires user authentication (see <a href="#Part7" id="rfc.xref.Part7.9"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a>).
1278               </p>
1279            </div>
1280            <div id="status.402">
1281               <div id="rfc.iref.4.3"></div>
1282               <div id="rfc.iref.s.20"></div>
1283               <h3 id="rfc.section.9.4.3"><a href="#rfc.section.9.4.3">9.4.3</a>&nbsp;<a href="#status.402">402 Payment Required</a></h3>
1284               <p id="rfc.section.9.4.3.p.1">This code is reserved for future use.</p>
1285            </div>
1286            <div id="status.403">
1287               <div id="rfc.iref.4.4"></div>
1288               <div id="rfc.iref.s.21"></div>
1289               <h3 id="rfc.section.9.4.4"><a href="#rfc.section.9.4.4">9.4.4</a>&nbsp;<a href="#status.403">403 Forbidden</a></h3>
1290               <p id="rfc.section.9.4.4.p.1">The server understood the request, but is refusing to fulfill it. Authorization will not help and the request <em class="bcp14">SHOULD NOT</em> be repeated. If the request method was not HEAD and the server wishes to make public why the request has not been fulfilled,
1291                  it <em class="bcp14">SHOULD</em> describe the reason for the refusal in the entity. If the server does not wish to make this information available to the client,
1292                  the status code 404 (Not Found) can be used instead.
1293               </p>
1294            </div>
1295            <div id="status.404">
1296               <div id="rfc.iref.4.5"></div>
1297               <div id="rfc.iref.s.22"></div>
1298               <h3 id="rfc.section.9.4.5"><a href="#rfc.section.9.4.5">9.4.5</a>&nbsp;<a href="#status.404">404 Not Found</a></h3>
1299               <p id="rfc.section.9.4.5.p.1">The server has not found anything matching the Request-URI. No indication is given of whether the condition is temporary or
1300                  permanent. The 410 (Gone) status code <em class="bcp14">SHOULD</em> be used if the server knows, through some internally configurable mechanism, that an old resource is permanently unavailable
1301                  and has no forwarding address. This status code is commonly used when the server does not wish to reveal exactly why the request
1302                  has been refused, or when no other response is applicable.
1303               </p>
1304            </div>
1305            <div id="status.405">
1306               <div id="rfc.iref.4.6"></div>
1307               <div id="rfc.iref.s.23"></div>
1308               <h3 id="rfc.section.9.4.6"><a href="#rfc.section.9.4.6">9.4.6</a>&nbsp;<a href="#status.405">405 Method Not Allowed</a></h3>
1309               <p id="rfc.section.9.4.6.p.1">The method specified in the Request-Line is not allowed for the resource identified by the Request-URI. The response <em class="bcp14">MUST</em> include an Allow header containing a list of valid methods for the requested resource.
1310               </p>
1311            </div>
1312            <div id="status.406">
1313               <div id="rfc.iref.4.7"></div>
1314               <div id="rfc.iref.s.24"></div>
1315               <h3 id="rfc.section.9.4.7"><a href="#rfc.section.9.4.7">9.4.7</a>&nbsp;<a href="#status.406">406 Not Acceptable</a></h3>
1316               <p id="rfc.section.9.4.7.p.1">The resource identified by the request is only capable of generating response entities which have content characteristics
1317                  not acceptable according to the accept headers sent in the request.
1318               </p>
1319               <p id="rfc.section.9.4.7.p.2">Unless it was a HEAD request, the response <em class="bcp14">SHOULD</em> include an entity containing a list of available entity characteristics and location(s) from which the user or user agent
1320                  can choose the one most appropriate. The entity format is specified by the media type given in the Content-Type header field.
1321                  Depending upon the format and the capabilities of the user agent, selection of the most appropriate choice <em class="bcp14">MAY</em> be performed automatically. However, this specification does not define any standard for such automatic selection.
1322               </p>
1323               <ul class="empty">
1324                  <li><b>Note:</b> HTTP/1.1 servers are allowed to return responses which are not acceptable according to the accept headers sent in the request.
1325                     In some cases, this may even be preferable to sending a 406 response. User agents are encouraged to inspect the headers of
1326                     an incoming response to determine if it is acceptable.
1327                  </li>
1328               </ul>
1329               <p id="rfc.section.9.4.7.p.3">If the response could be unacceptable, a user agent <em class="bcp14">SHOULD</em> temporarily stop receipt of more data and query the user for a decision on further actions.
1330               </p>
1331            </div>
1332            <div id="status.407">
1333               <div id="rfc.iref.4.8"></div>
1334               <div id="rfc.iref.s.25"></div>
1335               <h3 id="rfc.section.9.4.8"><a href="#rfc.section.9.4.8">9.4.8</a>&nbsp;<a href="#status.407">407 Proxy Authentication Required</a></h3>
1336               <p id="rfc.section.9.4.8.p.1">This code is similar to 401 (Unauthorized), but indicates that the client must first authenticate itself with the proxy (see <a href="#Part7" id="rfc.xref.Part7.10"><cite title="HTTP/1.1, part 7: Authentication">[Part7]</cite></a>).
1337               </p>
1338            </div>
1339            <div id="status.408">
1340               <div id="rfc.iref.4.9"></div>
1341               <div id="rfc.iref.s.26"></div>
1342               <h3 id="rfc.section.9.4.9"><a href="#rfc.section.9.4.9">9.4.9</a>&nbsp;<a href="#status.408">408 Request Timeout</a></h3>
1343               <p id="rfc.section.9.4.9.p.1">The client did not produce a request within the time that the server was prepared to wait. The client <em class="bcp14">MAY</em> repeat the request without modifications at any later time.
1344               </p>
1345            </div>
1346            <div id="status.409">
1347               <div id="rfc.iref.4.10"></div>
1348               <div id="rfc.iref.s.27"></div>
1349               <h3 id="rfc.section.9.4.10"><a href="#rfc.section.9.4.10">9.4.10</a>&nbsp;<a href="#status.409">409 Conflict</a></h3>
1350               <p id="rfc.section.9.4.10.p.1">The request could not be completed due to a conflict with the current state of the resource. This code is only allowed in
1351                  situations where it is expected that the user might be able to resolve the conflict and resubmit the request. The response
1352                  body <em class="bcp14">SHOULD</em> include enough information for the user to recognize the source of the conflict. Ideally, the response entity would include
1353                  enough information for the user or user agent to fix the problem; however, that might not be possible and is not required.
1354               </p>
1355               <p id="rfc.section.9.4.10.p.2">Conflicts are most likely to occur in response to a PUT request. For example, if versioning were being used and the entity
1356                  being PUT included changes to a resource which conflict with those made by an earlier (third-party) request, the server might
1357                  use the 409 response to indicate that it can't complete the request. In this case, the response entity would likely contain
1358                  a list of the differences between the two versions in a format defined by the response Content-Type.
1359               </p>
1360            </div>
1361            <div id="status.410">
1362               <div id="rfc.iref.4.11"></div>
1363               <div id="rfc.iref.s.28"></div>
1364               <h3 id="rfc.section.9.4.11"><a href="#rfc.section.9.4.11">9.4.11</a>&nbsp;<a href="#status.410">410 Gone</a></h3>
1365               <p id="rfc.section.9.4.11.p.1">The requested resource is no longer available at the server and no forwarding address is known. This condition is expected
1366                  to be considered permanent. Clients with link editing capabilities <em class="bcp14">SHOULD</em> delete references to the Request-URI after user approval. If the server does not know, or has no facility to determine, whether
1367                  or not the condition is permanent, the status code 404 (Not Found) <em class="bcp14">SHOULD</em> be used instead. This response is cacheable unless indicated otherwise.
1368               </p>
1369               <p id="rfc.section.9.4.11.p.2">The 410 response is primarily intended to assist the task of web maintenance by notifying the recipient that the resource
1370                  is intentionally unavailable and that the server owners desire that remote links to that resource be removed. Such an event
1371                  is common for limited-time, promotional services and for resources belonging to individuals no longer working at the server's
1372                  site. It is not necessary to mark all permanently unavailable resources as "gone" or to keep the mark for any length of time
1373                  -- that is left to the discretion of the server owner.
1374               </p>
1375            </div>
1376            <div id="status.411">
1377               <div id="rfc.iref.4.12"></div>
1378               <div id="rfc.iref.s.29"></div>
1379               <h3 id="rfc.section.9.4.12"><a href="#rfc.section.9.4.12">9.4.12</a>&nbsp;<a href="#status.411">411 Length Required</a></h3>
1380               <p id="rfc.section.9.4.12.p.1">The server refuses to accept the request without a defined Content-Length. The client <em class="bcp14">MAY</em> repeat the request if it adds a valid Content-Length header field containing the length of the message-body in the request
1381                  message.
1382               </p>
1383            </div>
1384            <div id="status.412">
1385               <div id="rfc.iref.4.13"></div>
1386               <div id="rfc.iref.s.30"></div>
1387               <h3 id="rfc.section.9.4.13"><a href="#rfc.section.9.4.13">9.4.13</a>&nbsp;<a href="#status.412">412 Precondition Failed</a></h3>
1388               <p id="rfc.section.9.4.13.p.1">The precondition given in one or more of the request-header fields evaluated to false when it was tested on the server, as
1389                  defined in <a href="#Part4" id="rfc.xref.Part4.13"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>.
1390               </p>
1391            </div>
1392            <div id="status.413">
1393               <div id="rfc.iref.4.14"></div>
1394               <div id="rfc.iref.s.31"></div>
1395               <h3 id="rfc.section.9.4.14"><a href="#rfc.section.9.4.14">9.4.14</a>&nbsp;<a href="#status.413">413 Request Entity Too Large</a></h3>
1396               <p id="rfc.section.9.4.14.p.1">The server is refusing to process a request because the request entity is larger than the server is willing or able to process.
1397                  The server <em class="bcp14">MAY</em> close the connection to prevent the client from continuing the request.
1398               </p>
1399               <p id="rfc.section.9.4.14.p.2">If the condition is temporary, the server <em class="bcp14">SHOULD</em> include a Retry-After header field to indicate that it is temporary and after what time the client <em class="bcp14">MAY</em> try again.
1400               </p>
1401            </div>
1402            <div id="status.414">
1403               <div id="rfc.iref.4.15"></div>
1404               <div id="rfc.iref.s.32"></div>
1405               <h3 id="rfc.section.9.4.15"><a href="#rfc.section.9.4.15">9.4.15</a>&nbsp;<a href="#status.414">414 Request-URI Too Long</a></h3>
1406               <p id="rfc.section.9.4.15.p.1">The server is refusing to service the request because the Request-URI is longer than the server is willing to interpret. This
1407                  rare condition is only likely to occur when a client has improperly converted a POST request to a GET request with long query
1408                  information, when the client has descended into a URI "black hole" of redirection (e.g., a redirected URI prefix that points
1409                  to a suffix of itself), or when the server is under attack by a client attempting to exploit security holes present in some
1410                  servers using fixed-length buffers for reading or manipulating the Request-URI.
1411               </p>
1412            </div>
1413            <div id="status.415">
1414               <div id="rfc.iref.4.16"></div>
1415               <div id="rfc.iref.s.33"></div>
1416               <h3 id="rfc.section.9.4.16"><a href="#rfc.section.9.4.16">9.4.16</a>&nbsp;<a href="#status.415">415 Unsupported Media Type</a></h3>
1417               <p id="rfc.section.9.4.16.p.1">The server is refusing to service the request because the entity of the request is in a format not supported by the requested
1418                  resource for the requested method.
1419               </p>
1420            </div>
1421            <div id="status.416">
1422               <div id="rfc.iref.4.17"></div>
1423               <div id="rfc.iref.s.34"></div>
1424               <h3 id="rfc.section.9.4.17"><a href="#rfc.section.9.4.17">9.4.17</a>&nbsp;<a href="#status.416">416 Requested Range Not Satisfiable</a></h3>
1425               <p id="rfc.section.9.4.17.p.1">The request included a Range request-header field (<a href="p5-range.html#header.range" title="Range">Section 6.4</a> of <a href="#Part5" id="rfc.xref.Part5.10"><cite title="HTTP/1.1, part 5: Range Requests and Partial Responses">[Part5]</cite></a>) and none of the range-specifier values in this field overlap the current extent of the selected resource.
1426               </p>
1427            </div>
1428            <div id="status.417">
1429               <div id="rfc.iref.4.18"></div>
1430               <div id="rfc.iref.s.35"></div>
1431               <h3 id="rfc.section.9.4.18"><a href="#rfc.section.9.4.18">9.4.18</a>&nbsp;<a href="#status.417">417 Expectation Failed</a></h3>
1432               <p id="rfc.section.9.4.18.p.1">The expectation given in an Expect request-header field (see <a href="#header.expect" id="rfc.xref.header.expect.2" title="Expect">Section&nbsp;10.2</a>) could not be met by this server, or, if the server is a proxy, the server has unambiguous evidence that the request could
1433                  not be met by the next-hop server.
1434               </p>
1435            </div>
1436         </div>
1437         <div id="status.5xx">
1438            <h2 id="rfc.section.9.5"><a href="#rfc.section.9.5">9.5</a>&nbsp;<a href="#status.5xx">Server Error 5xx</a></h2>
1439            <p id="rfc.section.9.5.p.1">Response status codes beginning with the digit "5" indicate cases in which the server is aware that it has erred or is incapable
1440               of performing the request. Except when responding to a HEAD request, the server <em class="bcp14">SHOULD</em> include an entity containing an explanation of the error situation, and whether it is a temporary or permanent condition.
1441               User agents <em class="bcp14">SHOULD</em> display any included entity to the user. These response codes are applicable to any request method.
1442            </p>
1443            <div id="status.500">
1444               <div id="rfc.iref.5.1"></div>
1445               <div id="rfc.iref.s.36"></div>
1446               <h3 id="rfc.section.9.5.1"><a href="#rfc.section.9.5.1">9.5.1</a>&nbsp;<a href="#status.500">500 Internal Server Error</a></h3>
1447               <p id="rfc.section.9.5.1.p.1">The server encountered an unexpected condition which prevented it from fulfilling the request.</p>
1448            </div>
1449            <div id="status.501">
1450               <div id="rfc.iref.5.2"></div>
1451               <div id="rfc.iref.s.37"></div>
1452               <h3 id="rfc.section.9.5.2"><a href="#rfc.section.9.5.2">9.5.2</a>&nbsp;<a href="#status.501">501 Not Implemented</a></h3>
1453               <p id="rfc.section.9.5.2.p.1">The server does not support the functionality required to fulfill the request. This is the appropriate response when the server
1454                  does not recognize the request method and is not capable of supporting it for any resource.
1455               </p>
1456            </div>
1457            <div id="status.502">
1458               <div id="rfc.iref.5.3"></div>
1459               <div id="rfc.iref.s.38"></div>
1460               <h3 id="rfc.section.9.5.3"><a href="#rfc.section.9.5.3">9.5.3</a>&nbsp;<a href="#status.502">502 Bad Gateway</a></h3>
1461               <p id="rfc.section.9.5.3.p.1">The server, while acting as a gateway or proxy, received an invalid response from the upstream server it accessed in attempting
1462                  to fulfill the request.
1463               </p>
1464            </div>
1465            <div id="status.503">
1466               <div id="rfc.iref.5.4"></div>
1467               <div id="rfc.iref.s.39"></div>
1468               <h3 id="rfc.section.9.5.4"><a href="#rfc.section.9.5.4">9.5.4</a>&nbsp;<a href="#status.503">503 Service Unavailable</a></h3>
1469               <p id="rfc.section.9.5.4.p.1">The server is currently unable to handle the request due to a temporary overloading or maintenance of the server. The implication
1470                  is that this is a temporary condition which will be alleviated after some delay. If known, the length of the delay <em class="bcp14">MAY</em> be indicated in a Retry-After header. If no Retry-After is given, the client <em class="bcp14">SHOULD</em> handle the response as it would for a 500 response.
1471               </p>
1472               <ul class="empty">
1473                  <li><b>Note:</b> The existence of the 503 status code does not imply that a server must use it when becoming overloaded. Some servers may wish
1474                     to simply refuse the connection.
1475                  </li>
1476               </ul>
1477            </div>
1478            <div id="status.504">
1479               <div id="rfc.iref.5.5"></div>
1480               <div id="rfc.iref.s.40"></div>
1481               <h3 id="rfc.section.9.5.5"><a href="#rfc.section.9.5.5">9.5.5</a>&nbsp;<a href="#status.504">504 Gateway Timeout</a></h3>
1482               <p id="rfc.section.9.5.5.p.1">The server, while acting as a gateway or proxy, did not receive a timely response from the upstream server specified by the
1483                  URI (e.g. HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed to access in attempting to complete the request.
1484               </p>
1485               <ul class="empty">
1486                  <li><b>Note:</b> Note to implementors: some deployed proxies are known to return 400 or 500 when DNS lookups time out.
1487                  </li>
1488               </ul>
1489            </div>
1490            <div id="status.505">
1491               <div id="rfc.iref.5.6"></div>
1492               <div id="rfc.iref.s.41"></div>
1493               <h3 id="rfc.section.9.5.6"><a href="#rfc.section.9.5.6">9.5.6</a>&nbsp;<a href="#status.505">505 HTTP Version Not Supported</a></h3>
1494               <p id="rfc.section.9.5.6.p.1">The server does not support, or refuses to support, the protocol version that was used in the request message. The server
1495                  is indicating that it is unable or unwilling to complete the request using the same major version as the client, as described
1496                  in <a href="p1-messaging.html#http.version" title="HTTP Version">Section 3.1</a> of <a href="#Part1" id="rfc.xref.Part1.20"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, other than with this error message. The response <em class="bcp14">SHOULD</em> contain an entity describing why that version is not supported and what other protocols are supported by that server.
1497               </p>
1498            </div>
1499         </div>
1500      </div>
1501      <div id="header.fields">
1502         <h1 id="rfc.section.10"><a href="#rfc.section.10">10.</a>&nbsp;<a href="#header.fields">Header Field Definitions</a></h1>
1503         <p id="rfc.section.10.p.1">This section defines the syntax and semantics of HTTP/1.1 header fields related to request and response semantics.</p>
1504         <p id="rfc.section.10.p.2">For entity-header fields, both sender and recipient refer to either the client or the server, depending on who sends and who
1505            receives the entity.
1506         </p>
1507         <div id="header.allow">
1508            <div id="rfc.iref.a.1"></div>
1509            <div id="rfc.iref.h.2"></div>
1510            <h2 id="rfc.section.10.1"><a href="#rfc.section.10.1">10.1</a>&nbsp;<a href="#header.allow">Allow</a></h2>
1511            <p id="rfc.section.10.1.p.1">The Allow entity-header field lists the set of methods supported by the resource identified by the Request-URI. The purpose
1512               of this field is strictly to inform the recipient of valid methods associated with the resource. An Allow header field <em class="bcp14">MUST</em> be present in a 405 (Method Not Allowed) response.
1513            </p>
1514            <div id="rfc.figure.u.13"></div><pre class="inline"><span id="rfc.iref.g.9"></span>  Allow   = "Allow" ":" #Method
1515</pre><p id="rfc.section.10.1.p.3">Example of use:</p>
1516            <div id="rfc.figure.u.14"></div><pre class="text">       Allow: GET, HEAD, PUT
1517</pre><p id="rfc.section.10.1.p.5">This field cannot prevent a client from trying other methods. However, the indications given by the Allow header field value <em class="bcp14">SHOULD</em> be followed. The actual set of allowed methods is defined by the origin server at the time of each request.
1518            </p>
1519            <p id="rfc.section.10.1.p.6">The Allow header field <em class="bcp14">MAY</em> be provided with a PUT request to recommend the methods to be supported by the new or modified resource. The server is not
1520               required to support these methods and <em class="bcp14">SHOULD</em> include an Allow header in the response giving the actual supported methods.
1521            </p>
1522            <p id="rfc.section.10.1.p.7">A proxy <em class="bcp14">MUST NOT</em> modify the Allow header field even if it does not understand all the methods specified, since the user agent might have other
1523               means of communicating with the origin server.
1524            </p>
1525         </div>
1526         <div id="header.expect">
1527            <div id="rfc.iref.e.1"></div>
1528            <div id="rfc.iref.h.3"></div>
1529            <h2 id="rfc.section.10.2"><a href="#rfc.section.10.2">10.2</a>&nbsp;<a href="#header.expect">Expect</a></h2>
1530            <p id="rfc.section.10.2.p.1">The Expect request-header field is used to indicate that particular server behaviors are required by the client.</p>
1531            <div id="rfc.figure.u.15"></div><pre class="inline"><span id="rfc.iref.g.10"></span><span id="rfc.iref.g.11"></span><span id="rfc.iref.g.12"></span><span id="rfc.iref.g.13"></span>  Expect       =  "Expect" ":" 1#expectation
1533  expectation  =  "100-continue" | expectation-extension
1534  expectation-extension =  token [ "=" ( token | quoted-string )
1535                           *expect-params ]
1536  expect-params =  ";" token [ "=" ( token | quoted-string ) ]
1537</pre><p id="rfc.section.10.2.p.3">A server that does not understand or is unable to comply with any of the expectation values in the Expect field of a request <em class="bcp14">MUST</em> respond with appropriate error status. The server <em class="bcp14">MUST</em> respond with a 417 (Expectation Failed) status if any of the expectations cannot be met or, if there are other problems with
1538               the request, some other 4xx status.
1539            </p>
1540            <p id="rfc.section.10.2.p.4">This header field is defined with extensible syntax to allow for future extensions. If a server receives a request containing
1541               an Expect field that includes an expectation-extension that it does not support, it <em class="bcp14">MUST</em> respond with a 417 (Expectation Failed) status.
1542            </p>
1543            <p id="rfc.section.10.2.p.5">Comparison of expectation values is case-insensitive for unquoted tokens (including the 100-continue token), and is case-sensitive
1544               for quoted-string expectation-extensions.
1545            </p>
1546            <p id="rfc.section.10.2.p.6">The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy <em class="bcp14">MUST</em> return a 417 (Expectation Failed) status if it receives a request with an expectation that it cannot meet. However, the Expect
1547               request-header itself is end-to-end; it <em class="bcp14">MUST</em> be forwarded if the request is forwarded.
1548            </p>
1549            <p id="rfc.section.10.2.p.7">Many older HTTP/1.0 and HTTP/1.1 applications do not understand the Expect header.</p>
1550            <p id="rfc.section.10.2.p.8">See <a href="p1-messaging.html#use.of.the.100.status" title="Use of the 100 (Continue) Status">Section 7.2.3</a> of <a href="#Part1" id="rfc.xref.Part1.21"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a> for the use of the 100 (Continue) status.
1551            </p>
1552         </div>
1553         <div id="header.from">
1554            <div id="rfc.iref.f.1"></div>
1555            <div id="rfc.iref.h.4"></div>
1556            <h2 id="rfc.section.10.3"><a href="#rfc.section.10.3">10.3</a>&nbsp;<a href="#header.from">From</a></h2>
1557            <p id="rfc.section.10.3.p.1">The From request-header field, if given, <em class="bcp14">SHOULD</em> contain an Internet e-mail address for the human user who controls the requesting user agent. The address <em class="bcp14">SHOULD</em> be machine-usable, as defined by "mailbox" in <a href="">Section 3.4</a> of <a href="#RFC2822" id="rfc.xref.RFC2822.1"><cite title="Internet Message Format">[RFC2822]</cite></a>:
1558            </p>
1559            <div id="rfc.figure.u.16"></div><pre class="inline"><span id="rfc.iref.g.14"></span>  From    = "From" ":" mailbox
1561  mailbox = &lt;mailbox, defined in <a href="#RFC2822" id="rfc.xref.RFC2822.2"><cite title="Internet Message Format">[RFC2822]</cite></a>, <a href="">Section 3.4</a>&gt;
1562</pre><p id="rfc.section.10.3.p.3">An example is:</p>
1563            <div id="rfc.figure.u.17"></div><pre class="text">    From:
1564</pre><p id="rfc.section.10.3.p.5">This header field <em class="bcp14">MAY</em> be used for logging purposes and as a means for identifying the source of invalid or unwanted requests. It <em class="bcp14">SHOULD NOT</em> be used as an insecure form of access protection. The interpretation of this field is that the request is being performed
1565               on behalf of the person given, who accepts responsibility for the method performed. In particular, robot agents <em class="bcp14">SHOULD</em> include this header so that the person responsible for running the robot can be contacted if problems occur on the receiving
1566               end.
1567            </p>
1568            <p id="rfc.section.10.3.p.6">The Internet e-mail address in this field <em class="bcp14">MAY</em> be separate from the Internet host which issued the request. For example, when a request is passed through a proxy the original
1569               issuer's address <em class="bcp14">SHOULD</em> be used.
1570            </p>
1571            <p id="rfc.section.10.3.p.7">The client <em class="bcp14">SHOULD NOT</em> send the From header field without the user's approval, as it might conflict with the user's privacy interests or their site's
1572               security policy. It is strongly recommended that the user be able to disable, enable, and modify the value of this field at
1573               any time prior to a request.
1574            </p>
1575         </div>
1576         <div id="header.location">
1577            <div id="rfc.iref.l.1"></div>
1578            <div id="rfc.iref.h.5"></div>
1579            <h2 id="rfc.section.10.4"><a href="#rfc.section.10.4">10.4</a>&nbsp;<a href="#header.location">Location</a></h2>
1580            <p id="rfc.section.10.4.p.1">The Location response-header field is used to redirect the recipient to a location other than the Request-URI for completion
1581               of the request or identification of a new resource. For 201 (Created) responses, the Location is that of the new resource
1582               which was created by the request. For 3xx responses, the location <em class="bcp14">SHOULD</em> indicate the server's preferred URI for automatic redirection to the resource. The field value consists of a single absolute
1583               URI.
1584            </p>
1585            <div id="rfc.figure.u.18"></div><pre class="inline"><span id="rfc.iref.g.15"></span>  Location       = "Location" ":" absoluteURI [ "#" fragment ]
1586</pre><p id="rfc.section.10.4.p.3">An example is:</p>
1587            <div id="rfc.figure.u.19"></div><pre class="text">    Location:
1588</pre><p id="rfc.section.10.4.p.5"></p>
1589            <ul class="empty">
1590               <li><b>Note:</b> The Content-Location header field (<a href="p3-payload.html#header.content-location" title="Content-Location">Section 6.7</a> of <a href="#Part3" id="rfc.xref.Part3.11"><cite title="HTTP/1.1, part 3: Message Payload and Content Negotiation">[Part3]</cite></a>) differs from Location in that the Content-Location identifies the original location of the entity enclosed in the request.
1591                  It is therefore possible for a response to contain header fields for both Location and Content-Location.
1592               </li>
1593            </ul>
1594            <p id="rfc.section.10.4.p.6">There are circumstances in which a fragment identifier in a Location URL would not be appropriate: </p>
1595            <ul>
1596               <li>With a 201 Created response, because in this usage the Location header specifies the URL for the entire created resource.</li>
1597               <li>With a 300 Multiple Choices, since the choice decision is intended to be made on resource characteristics and not fragment
1598                  characteristics.
1599               </li>
1600               <li>With 305 Use Proxy.</li>
1601            </ul>
1602         </div>
1603         <div id="header.max-forwards">
1604            <div id="rfc.iref.m.9"></div>
1605            <div id="rfc.iref.h.6"></div>
1606            <h2 id="rfc.section.10.5"><a href="#rfc.section.10.5">10.5</a>&nbsp;<a href="#header.max-forwards">Max-Forwards</a></h2>
1607            <p id="rfc.section.10.5.p.1">The Max-Forwards request-header field provides a mechanism with the TRACE (<a href="#TRACE" id="rfc.xref.TRACE.2" title="TRACE">Section&nbsp;8.8</a>) and OPTIONS (<a href="#OPTIONS" id="rfc.xref.OPTIONS.2" title="OPTIONS">Section&nbsp;8.2</a>) methods to limit the number of proxies or gateways that can forward the request to the next inbound server. This can be
1608               useful when the client is attempting to trace a request chain which appears to be failing or looping in mid-chain.
1609            </p>
1610            <div id="rfc.figure.u.20"></div><pre class="inline"><span id="rfc.iref.g.16"></span>  Max-Forwards   = "Max-Forwards" ":" 1*DIGIT
1611</pre><p id="rfc.section.10.5.p.3">The Max-Forwards value is a decimal integer indicating the remaining number of times this request message may be forwarded.</p>
1612            <p id="rfc.section.10.5.p.4">Each proxy or gateway recipient of a TRACE or OPTIONS request containing a Max-Forwards header field <em class="bcp14">MUST</em> check and update its value prior to forwarding the request. If the received value is zero (0), the recipient <em class="bcp14">MUST NOT</em> forward the request; instead, it <em class="bcp14">MUST</em> respond as the final recipient. If the received Max-Forwards value is greater than zero, then the forwarded message <em class="bcp14">MUST</em> contain an updated Max-Forwards field with a value decremented by one (1).
1613            </p>
1614            <p id="rfc.section.10.5.p.5">The Max-Forwards header field <em class="bcp14">MAY</em> be ignored for all other methods defined by this specification and for any extension methods for which it is not explicitly
1615               referred to as part of that method definition.
1616            </p>
1617         </div>
1618         <div id="header.referer">
1619            <div id="rfc.iref.r.1"></div>
1620            <div id="rfc.iref.h.7"></div>
1621            <h2 id="rfc.section.10.6"><a href="#rfc.section.10.6">10.6</a>&nbsp;<a href="#header.referer">Referer</a></h2>
1622            <p id="rfc.section.10.6.p.1">The Referer[sic] request-header field allows the client to specify, for the server's benefit, the address (URI) of the resource
1623               from which the Request-URI was obtained (the "referrer", although the header field is misspelled.) The Referer request-header
1624               allows a server to generate lists of back-links to resources for interest, logging, optimized caching, etc. It also allows
1625               obsolete or mistyped links to be traced for maintenance. The Referer field <em class="bcp14">MUST NOT</em> be sent if the Request-URI was obtained from a source that does not have its own URI, such as input from the user keyboard.
1626            </p>
1627            <div id="rfc.figure.u.21"></div><pre class="inline"><span id="rfc.iref.g.17"></span>  Referer        = "Referer" ":" ( absoluteURI | relativeURI )
1628</pre><p id="rfc.section.10.6.p.3">Example:</p>
1629            <div id="rfc.figure.u.22"></div><pre class="text">    Referer:
1630</pre><p id="rfc.section.10.6.p.5">If the field value is a relative URI, it <em class="bcp14">SHOULD</em> be interpreted relative to the Request-URI. The URI <em class="bcp14">MUST NOT</em> include a fragment. See <a href="" title="Encoding Sensitive Information in URIs">Section&nbsp;12.2</a> for security considerations.
1631            </p>
1632         </div>
1633         <div id="header.retry-after">
1634            <div id="rfc.iref.r.2"></div>
1635            <div id="rfc.iref.h.8"></div>
1636            <h2 id="rfc.section.10.7"><a href="#rfc.section.10.7">10.7</a>&nbsp;<a href="#header.retry-after">Retry-After</a></h2>
1637            <p id="rfc.section.10.7.p.1">The Retry-After response-header field can be used with a 503 (Service Unavailable) response to indicate how long the service
1638               is expected to be unavailable to the requesting client. This field <em class="bcp14">MAY</em> also be used with any 3xx (Redirection) response to indicate the minimum time the user-agent is asked wait before issuing
1639               the redirected request. The value of this field can be either an HTTP-date or an integer number of seconds (in decimal) after
1640               the time of the response.
1641            </p>
1642            <div id="rfc.figure.u.23"></div><pre class="inline"><span id="rfc.iref.g.18"></span>  Retry-After   = "Retry-After" ":" ( HTTP-date | delta-seconds )
1643</pre><p id="rfc.section.10.7.p.3">Time spans are non-negative decimal integers, representing time in seconds.</p>
1644            <div id="rfc.figure.u.24"></div><pre class="inline"><span id="rfc.iref.g.19"></span>  delta-seconds  = 1*DIGIT
1645</pre><p id="rfc.section.10.7.p.5">Two examples of its use are</p>
1646            <div id="rfc.figure.u.25"></div><pre class="text">    Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
1647    Retry-After: 120
1648</pre><p id="rfc.section.10.7.p.7">In the latter example, the delay is 2 minutes.</p>
1649         </div>
1650         <div id="header.server">
1651            <div id="rfc.iref.s.42"></div>
1652            <div id="rfc.iref.h.9"></div>
1653            <h2 id="rfc.section.10.8"><a href="#rfc.section.10.8">10.8</a>&nbsp;<a href="#header.server">Server</a></h2>
1654            <p id="rfc.section.10.8.p.1">The Server response-header field contains information about the software used by the origin server to handle the request.
1655               The field can contain multiple product tokens (<a href="p1-messaging.html#product.tokens" title="Product Tokens">Section 3.5</a> of <a href="#Part1" id="rfc.xref.Part1.22"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) and comments identifying the server and any significant subproducts. The product tokens are listed in order of their significance
1656               for identifying the application.
1657            </p>
1658            <div id="rfc.figure.u.26"></div><pre class="inline"><span id="rfc.iref.g.20"></span>  Server         = "Server" ":" 1*( product | comment )
1659</pre><p id="rfc.section.10.8.p.3">Example:</p>
1660            <div id="rfc.figure.u.27"></div><pre class="text">    Server: CERN/3.0 libwww/2.17
1661</pre><p id="rfc.section.10.8.p.5">If the response is being forwarded through a proxy, the proxy application <em class="bcp14">MUST NOT</em> modify the Server response-header. Instead, it <em class="bcp14">MUST</em> include a Via field (as described in <a href="p1-messaging.html#header.via" title="Via">Section 8.9</a> of <a href="#Part1" id="rfc.xref.Part1.23"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>).
1662            </p>
1663            <ul class="empty">
1664               <li><b>Note:</b> Revealing the specific software version of the server might allow the server machine to become more vulnerable to attacks
1665                  against software that is known to contain security holes. Server implementors are encouraged to make this field a configurable
1666                  option.
1667               </li>
1668            </ul>
1669         </div>
1670         <div id="header.user-agent">
1671            <div id="rfc.iref.u.1"></div>
1672            <div id="rfc.iref.h.10"></div>
1673            <h2 id="rfc.section.10.9"><a href="#rfc.section.10.9">10.9</a>&nbsp;<a href="#header.user-agent">User-Agent</a></h2>
1674            <p id="rfc.section.10.9.p.1">The User-Agent request-header field contains information about the user agent originating the request. This is for statistical
1675               purposes, the tracing of protocol violations, and automated recognition of user agents for the sake of tailoring responses
1676               to avoid particular user agent limitations. User agents <em class="bcp14">SHOULD</em> include this field with requests. The field can contain multiple product tokens (<a href="p1-messaging.html#product.tokens" title="Product Tokens">Section 3.5</a> of <a href="#Part1" id="rfc.xref.Part1.24"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) and comments identifying the agent and any subproducts which form a significant part of the user agent. By convention, the
1677               product tokens are listed in order of their significance for identifying the application.
1678            </p>
1679            <div id="rfc.figure.u.28"></div><pre class="inline"><span id="rfc.iref.g.21"></span>  User-Agent     = "User-Agent" ":" 1*( product | comment )
1680</pre><p id="rfc.section.10.9.p.3">Example:</p>
1681            <div id="rfc.figure.u.29"></div><pre class="text">    User-Agent: CERN-LineMode/2.15 libwww/2.17b3
1683      </div>
1684      <div id="IANA.considerations">
1685         <h1 id="rfc.section.11"><a href="#rfc.section.11">11.</a>&nbsp;<a href="#IANA.considerations">IANA Considerations</a></h1>
1686         <p id="rfc.section.11.p.1"><span class="comment" id="rfc.comment.1">[<a href="#rfc.comment.1" class="smpl">rfc.comment.1</a>: TBD.]</span>
1687         </p>
1688      </div>
1689      <div id="security.considerations">
1690         <h1 id="rfc.section.12"><a href="#rfc.section.12">12.</a>&nbsp;<a href="#security.considerations">Security Considerations</a></h1>
1691         <p id="rfc.section.12.p.1">This section is meant to inform application developers, information providers, and users of the security limitations in HTTP/1.1
1692            as described by this document. The discussion does not include definitive solutions to the problems revealed, though it does
1693            make some suggestions for reducing security risks.
1694         </p>
1695         <div id="security.sensitive">
1696            <h2 id="rfc.section.12.1"><a href="#rfc.section.12.1">12.1</a>&nbsp;<a href="#security.sensitive">Transfer of Sensitive Information</a></h2>
1697            <p id="rfc.section.12.1.p.1">Like any generic data transfer protocol, HTTP cannot regulate the content of the data that is transferred, nor is there any
1698               a priori method of determining the sensitivity of any particular piece of information within the context of any given request.
1699               Therefore, applications <em class="bcp14">SHOULD</em> supply as much control over this information as possible to the provider of that information. Four header fields are worth
1700               special mention in this context: Server, Via, Referer and From.
1701            </p>
1702            <p id="rfc.section.12.1.p.2">Revealing the specific software version of the server might allow the server machine to become more vulnerable to attacks
1703               against software that is known to contain security holes. Implementors <em class="bcp14">SHOULD</em> make the Server header field a configurable option.
1704            </p>
1705            <p id="rfc.section.12.1.p.3">Proxies which serve as a portal through a network firewall <em class="bcp14">SHOULD</em> take special precautions regarding the transfer of header information that identifies the hosts behind the firewall. In particular,
1706               they <em class="bcp14">SHOULD</em> remove, or replace with sanitized versions, any Via fields generated behind the firewall.
1707            </p>
1708            <p id="rfc.section.12.1.p.4">The Referer header allows reading patterns to be studied and reverse links drawn. Although it can be very useful, its power
1709               can be abused if user details are not separated from the information contained in the Referer. Even when the personal information
1710               has been removed, the Referer header might indicate a private document's URI whose publication would be inappropriate.
1711            </p>
1712            <p id="rfc.section.12.1.p.5">The information sent in the From field might conflict with the user's privacy interests or their site's security policy, and
1713               hence it <em class="bcp14">SHOULD NOT</em> be transmitted without the user being able to disable, enable, and modify the contents of the field. The user <em class="bcp14">MUST</em> be able to set the contents of this field within a user preference or application defaults configuration.
1714            </p>
1715            <p id="rfc.section.12.1.p.6">We suggest, though do not require, that a convenient toggle interface be provided for the user to enable or disable the sending
1716               of From and Referer information.
1717            </p>
1718            <p id="rfc.section.12.1.p.7">The User-Agent (<a href="#header.user-agent" id="rfc.xref.header.user-agent.2" title="User-Agent">Section&nbsp;10.9</a>) or Server (<a href="#header.server" id="rfc.xref.header.server.2" title="Server">Section&nbsp;10.8</a>) header fields can sometimes be used to determine that a specific client or server have a particular security hole which
1719               might be exploited. Unfortunately, this same information is often used for other valuable purposes for which HTTP currently
1720               has no better mechanism.
1721            </p>
1722         </div>
1723         <div id="">
1724            <h2 id="rfc.section.12.2"><a href="#rfc.section.12.2">12.2</a>&nbsp;<a href="">Encoding Sensitive Information in URIs</a></h2>
1725            <p id="rfc.section.12.2.p.1">Because the source of a link might be private information or might reveal an otherwise private information source, it is strongly
1726               recommended that the user be able to select whether or not the Referer field is sent. For example, a browser client could
1727               have a toggle switch for browsing openly/anonymously, which would respectively enable/disable the sending of Referer and From
1728               information.
1729            </p>
1730            <p id="rfc.section.12.2.p.2">Clients <em class="bcp14">SHOULD NOT</em> include a Referer header field in a (non-secure) HTTP request if the referring page was transferred with a secure protocol.
1731            </p>
1732            <p id="rfc.section.12.2.p.3">Authors of services should not use GET-based forms for the submission of sensitive data because that data will be encoded
1733               in the Request-URI. Many existing servers, proxies, and user agents log or display the Request-URI in places where it might
1734               be visible to third parties. Such services can use POST-based form submission instead.
1735            </p>
1736         </div>
1737         <div id="location.spoofing">
1738            <h2 id="rfc.section.12.3"><a href="#rfc.section.12.3">12.3</a>&nbsp;<a href="#location.spoofing">Location Headers and Spoofing</a></h2>
1739            <p id="rfc.section.12.3.p.1">If a single server supports multiple organizations that do not trust one another, then it <em class="bcp14">MUST</em> check the values of Location and Content-Location headers in responses that are generated under control of said organizations
1740               to make sure that they do not attempt to invalidate resources over which they have no authority.
1741            </p>
1742         </div>
1743      </div>
1744      <div id="ack">
1745         <h1 id="rfc.section.13"><a href="#rfc.section.13">13.</a>&nbsp;<a href="#ack">Acknowledgments</a></h1>
1746      </div>
1747      <h1 id="rfc.references"><a id="rfc.section.14" href="#rfc.section.14">14.</a> References
1748      </h1>
1749      <h2 id="rfc.references.1"><a href="#rfc.section.14.1" id="rfc.section.14.1">14.1</a> Normative References
1750      </h2>
1751      <table>
1752         <tr>
1753            <td class="reference"><b id="Part1">[Part1]</b></td>
1754            <td class="top"><a href="" title="Day Software">Fielding, R., Ed.</a>, <a href="" title="One Laptop per Child">Gettys, J.</a>, <a href="" title="Hewlett-Packard Company">Mogul, J.</a>, <a href="" title="Microsoft Corporation">Frystyk, H.</a>, <a href="" title="Adobe Systems, Incorporated">Masinter, L.</a>, <a href="" title="Microsoft Corporation">Leach, P.</a>, <a href="" title="World Wide Web Consortium">Berners-Lee, T.</a>, <a href="" title="World Wide Web Consortium">Lafon, Y., Ed.</a>, and <a href="" title="greenbytes GmbH">J. Reschke, Ed.</a>, “<a href="">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</a>”, Internet-Draft&nbsp;draft-ietf-httpbis-p1-messaging-02 (work in progress), February&nbsp;2008.
1755            </td>
1756         </tr>
1757         <tr>
1758            <td class="reference"><b id="Part3">[Part3]</b></td>
1759            <td class="top"><a href="" title="Day Software">Fielding, R., Ed.</a>, <a href="" title="One Laptop per Child">Gettys, J.</a>, <a href="" title="Hewlett-Packard Company">Mogul, J.</a>, <a href="" title="Microsoft Corporation">Frystyk, H.</a>, <a href="" title="Adobe Systems, Incorporated">Masinter, L.</a>, <a href="" title="Microsoft Corporation">Leach, P.</a>, <a href="" title="World Wide Web Consortium">Berners-Lee, T.</a>, <a href="" title="World Wide Web Consortium">Lafon, Y., Ed.</a>, and <a href="" title="greenbytes GmbH">J. Reschke, Ed.</a>, “<a href="">HTTP/1.1, part 3: Message Payload and Content Negotiation</a>”, Internet-Draft&nbsp;draft-ietf-httpbis-p3-payload-02 (work in progress), February&nbsp;2008.
1760            </td>
1761         </tr>
1762         <tr>
1763            <td class="reference"><b id="Part4">[Part4]</b></td>
1764            <td class="top"><a href="" title="Day Software">Fielding, R., Ed.</a>, <a href="" title="One Laptop per Child">Gettys, J.</a>, <a href="" title="Hewlett-Packard Company">Mogul, J.</a>, <a href="" title="Microsoft Corporation">Frystyk, H.</a>, <a href="" title="Adobe Systems, Incorporated">Masinter, L.</a>, <a href="" title="Microsoft Corporation">Leach, P.</a>, <a href="" title="World Wide Web Consortium">Berners-Lee, T.</a>, <a href="" title="World Wide Web Consortium">Lafon, Y., Ed.</a>, and <a href="" title="greenbytes GmbH">J. Reschke, Ed.</a>, “<a href="">HTTP/1.1, part 4: Conditional Requests</a>”, Internet-Draft&nbsp;draft-ietf-httpbis-p4-conditional-02 (work in progress), February&nbsp;2008.
1765            </td>
1766         </tr>
1767         <tr>
1768            <td class="reference"><b id="Part5">[Part5]</b></td>
1769            <td class="top"><a href="" title="Day Software">Fielding, R., Ed.</a>, <a href="" title="One Laptop per Child">Gettys, J.</a>, <a href="" title="Hewlett-Packard Company">Mogul, J.</a>, <a href="" title="Microsoft Corporation">Frystyk, H.</a>, <a href="" title="Adobe Systems, Incorporated">Masinter, L.</a>, <a href="" title="Microsoft Corporation">Leach, P.</a>, <a href="" title="World Wide Web Consortium">Berners-Lee, T.</a>, <a href="" title="World Wide Web Consortium">Lafon, Y., Ed.</a>, and <a href="" title="greenbytes GmbH">J. Reschke, Ed.</a>, “<a href="">HTTP/1.1, part 5: Range Requests and Partial Responses</a>”, Internet-Draft&nbsp;draft-ietf-httpbis-p5-range-02 (work in progress), February&nbsp;2008.
1770            </td>
1771         </tr>
1772         <tr>
1773            <td class="reference"><b id="Part6">[Part6]</b></td>
1774            <td class="top"><a href="" title="Day Software">Fielding, R., Ed.</a>, <a href="" title="One Laptop per Child">Gettys, J.</a>, <a href="" title="Hewlett-Packard Company">Mogul, J.</a>, <a href="" title="Microsoft Corporation">Frystyk, H.</a>, <a href="" title="Adobe Systems, Incorporated">Masinter, L.</a>, <a href="" title="Microsoft Corporation">Leach, P.</a>, <a href="" title="World Wide Web Consortium">Berners-Lee, T.</a>, <a href="" title="World Wide Web Consortium">Lafon, Y., Ed.</a>, and <a href="" title="greenbytes GmbH">J. Reschke, Ed.</a>, “<a href="">HTTP/1.1, part 6: Caching</a>”, Internet-Draft&nbsp;draft-ietf-httpbis-p6-cache-02 (work in progress), February&nbsp;2008.
1775            </td>
1776         </tr>
1777         <tr>
1778            <td class="reference"><b id="Part7">[Part7]</b></td>
1779            <td class="top"><a href="" title="Day Software">Fielding, R., Ed.</a>, <a href="" title="One Laptop per Child">Gettys, J.</a>, <a href="" title="Hewlett-Packard Company">Mogul, J.</a>, <a href="" title="Microsoft Corporation">Frystyk, H.</a>, <a href="" title="Adobe Systems, Incorporated">Masinter, L.</a>, <a href="" title="Microsoft Corporation">Leach, P.</a>, <a href="" title="World Wide Web Consortium">Berners-Lee, T.</a>, <a href="" title="World Wide Web Consortium">Lafon, Y., Ed.</a>, and <a href="" title="greenbytes GmbH">J. Reschke, Ed.</a>, “<a href="">HTTP/1.1, part 7: Authentication</a>”, Internet-Draft&nbsp;draft-ietf-httpbis-p7-auth-02 (work in progress), February&nbsp;2008.
1780            </td>
1781         </tr>
1782         <tr>
1783            <td class="reference"><b id="RFC2119">[RFC2119]</b></td>
1784            <td class="top"><a href="" title="Harvard University">Bradner, S.</a>, “<a href="">Key words for use in RFCs to Indicate Requirement Levels</a>”, BCP&nbsp;14, RFC&nbsp;2119, March&nbsp;1997.
1785            </td>
1786         </tr>
1787      </table>
1788      <h2 id="rfc.references.2"><a href="#rfc.section.14.2" id="rfc.section.14.2">14.2</a> Informative References
1789      </h2>
1790      <table>
1791         <tr>
1792            <td class="reference"><b id="Luo1998">[Luo1998]</b></td>
1793            <td class="top">Luotonen, A., “<a href="">Tunneling TCP based protocols through Web proxy servers</a>”, Internet-Draft&nbsp;draft-luotonen-web-proxy-tunneling-01 (work in progress), August&nbsp;1998.
1794            </td>
1795         </tr>
1796         <tr>
1797            <td class="reference"><b id="RFC1945">[RFC1945]</b></td>
1798            <td class="top"><a href="" title="MIT, Laboratory for Computer Science">Berners-Lee, T.</a>, <a href="" title="University of California, Irvine, Department of Information and Computer Science">Fielding, R.</a>, and <a href="" title="W3 Consortium, MIT Laboratory for Computer Science">H. Nielsen</a>, “<a href="">Hypertext Transfer Protocol -- HTTP/1.0</a>”, RFC&nbsp;1945, May&nbsp;1996.
1799            </td>
1800         </tr>
1801         <tr>
1802            <td class="reference"><b id="RFC2068">[RFC2068]</b></td>
1803            <td class="top"><a href="" title="University of California, Irvine, Department of Information and Computer Science">Fielding, R.</a>, <a href="" title="MIT Laboratory for Computer Science">Gettys, J.</a>, <a href="" title="Digital Equipment Corporation, Western Research Laboratory">Mogul, J.</a>, <a href="" title="MIT Laboratory for Computer Science">Nielsen, H.</a>, and <a href="" title="MIT Laboratory for Computer Science">T. Berners-Lee</a>, “<a href="">Hypertext Transfer Protocol -- HTTP/1.1</a>”, RFC&nbsp;2068, January&nbsp;1997.
1804            </td>
1805         </tr>
1806         <tr>
1807            <td class="reference"><b id="RFC2616">[RFC2616]</b></td>
1808            <td class="top"><a href="" title="University of California, Irvine">Fielding, R.</a>, <a href="" title="W3C">Gettys, J.</a>, <a href="" title="Compaq Computer Corporation">Mogul, J.</a>, <a href="" title="MIT Laboratory for Computer Science">Frystyk, H.</a>, <a href="" title="Xerox Corporation">Masinter, L.</a>, <a href="" title="Microsoft Corporation">Leach, P.</a>, and <a href="" title="W3C">T. Berners-Lee</a>, “<a href="">Hypertext Transfer Protocol -- HTTP/1.1</a>”, RFC&nbsp;2616, June&nbsp;1999.
1809            </td>
1810         </tr>
1811         <tr>
1812            <td class="reference"><b id="RFC2822">[RFC2822]</b></td>
1813            <td class="top">Resnick, P., “<a href="">Internet Message Format</a>”, RFC&nbsp;2822, April&nbsp;2001.
1814            </td>
1815         </tr>
1816      </table>
1817      <div id="compatibility">
1818         <h1 id="rfc.section.A" class="np"><a href="#rfc.section.A">A.</a>&nbsp;<a href="#compatibility">Compatibility with Previous Versions</a></h1>
1819         <div id="changes.from.rfc.2068">
1820            <h2 id="rfc.section.A.1"><a href="#rfc.section.A.1">A.1</a>&nbsp;<a href="#changes.from.rfc.2068">Changes from RFC 2068</a></h2>
1821            <p id="rfc.section.A.1.p.1">Clarified which error code should be used for inbound server failures (e.g. DNS failures). (<a href="#status.504" id="rfc.xref.status.504.2" title="504 Gateway Timeout">Section&nbsp;9.5.5</a>).
1822            </p>
1823            <p id="rfc.section.A.1.p.2">201 (Created) had a race that required an Etag be sent when a resource is first created. (<a href="#status.201" id="rfc.xref.status.201.2" title="201 Created">Section&nbsp;9.2.2</a>).
1824            </p>
1825            <p id="rfc.section.A.1.p.3">Rewrite of message transmission requirements to make it much harder for implementors to get it wrong, as the consequences
1826               of errors here can have significant impact on the Internet, and to deal with the following problems:
1827            </p>
1828            <ol>
1829               <li>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where this was incorrectly placing a requirement on the behavior of
1830                  an implementation of a future version of HTTP/1.x
1831               </li>
1832               <li>Made it clear that user-agents should retry requests, not "clients" in general.</li>
1833               <li>Converted requirements for clients to ignore unexpected 100 (Continue) responses, and for proxies to forward 100 responses,
1834                  into a general requirement for 1xx responses.
1835               </li>
1836               <li>Modified some TCP-specific language, to make it clearer that non-TCP transports are possible for HTTP.</li>
1837               <li>Require that the origin server <em class="bcp14">MUST NOT</em> wait for the request body before it sends a required 100 (Continue) response.
1838               </li>
1839               <li>Allow, rather than require, a server to omit 100 (Continue) if it has already seen some of the request body.</li>
1840               <li>Allow servers to defend against denial-of-service attacks and broken clients.</li>
1841            </ol>
1842            <p id="rfc.section.A.1.p.4">This change adds the Expect header and 417 status code.</p>
1843            <p id="rfc.section.A.1.p.5">Clean up confusion between 403 and 404 responses. (Section <a href="#status.403" id="rfc.xref.status.403.2" title="403 Forbidden">9.4.4</a>, <a href="#status.404" id="rfc.xref.status.404.2" title="404 Not Found">9.4.5</a>, and <a href="#status.410" id="rfc.xref.status.410.2" title="410 Gone">9.4.11</a>)
1844            </p>
1845            <p id="rfc.section.A.1.p.6">The PATCH<span id="rfc.iref.p.3"></span><span id="rfc.iref.m.10"></span>, LINK<span id="rfc.iref.l.2"></span><span id="rfc.iref.m.11"></span>, UNLINK<span id="rfc.iref.u.2"></span><span id="rfc.iref.m.12"></span> methods were defined but not commonly implemented in previous versions of this specification. See <a href="#RFC2068" id="rfc.xref.RFC2068.3"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2068]</cite></a>.
1846            </p>
1847         </div>
1848         <div id="changes.from.rfc.2616">
1849            <h2 id="rfc.section.A.2"><a href="#rfc.section.A.2">A.2</a>&nbsp;<a href="#changes.from.rfc.2616">Changes from RFC 2616</a></h2>
1850            <p id="rfc.section.A.2.p.1">Clarify definition of POST. (<a href="#POST" id="rfc.xref.POST.2" title="POST">Section&nbsp;8.5</a>)
1851            </p>
1852            <p id="rfc.section.A.2.p.2">Failed to consider that there are many other request methods that are safe to automatically redirect, and further that the
1853               user agent is able to make that determination based on the request method semantics. (Sections <a href="#status.301" id="rfc.xref.status.301.2" title="301 Moved Permanently">9.3.2</a>, <a href="#status.302" id="rfc.xref.status.302.2" title="302 Found">9.3.3</a> and <a href="#status.307" id="rfc.xref.status.307.2" title="307 Temporary Redirect">9.3.8</a> )
1854            </p>
1855            <p id="rfc.section.A.2.p.3">Correct syntax of Location header to allow fragment, as referred symbol wasn't what was expected, and add some clarifications
1856               as to when it would not be appropriate. (<a href="#header.location" id="rfc.xref.header.location.3" title="Location">Section&nbsp;10.4</a>)
1857            </p>
1858            <p id="rfc.section.A.2.p.4">In the description of the Server header, the Via field was described as a SHOULD. The requirement was and is stated correctly
1859               in the description of the Via header in <a href="p1-messaging.html#header.via" title="Via">Section 8.9</a> of <a href="#Part1" id="rfc.xref.Part1.25"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>. (<a href="#header.server" id="rfc.xref.header.server.3" title="Server">Section&nbsp;10.8</a>)
1860            </p>
1861         </div>
1862      </div>
1863      <div>
1864         <h1 id="rfc.section.B"><a href="#rfc.section.B">B.</a>&nbsp;Change Log (to be removed by RFC Editor before publication)
1865         </h1>
1866         <div>
1867            <h2 id="rfc.section.B.1"><a href="#rfc.section.B.1">B.1</a>&nbsp;Since RFC2616
1868            </h2>
1869            <p id="rfc.section.B.1.p.1">Extracted relevant partitions from <a href="#RFC2616" id="rfc.xref.RFC2616.2"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>.
1870            </p>
1871         </div>
1872         <div>
1873            <h2 id="rfc.section.B.2"><a href="#rfc.section.B.2">B.2</a>&nbsp;Since draft-ietf-httpbis-p2-semantics-00
1874            </h2>
1875            <p id="rfc.section.B.2.p.1">Closed issues: </p>
1876            <ul>
1877               <li>&lt;<a href=""></a>&gt;: "Via is a MUST" (&lt;<a href=""></a>&gt;)
1878               </li>
1879               <li>&lt;<a href=""></a>&gt;: "Fragments allowed in Location" (&lt;<a href=""></a>&gt;)
1880               </li>
1881               <li>&lt;<a href=""></a>&gt;: "Safe Methods vs Redirection" (&lt;<a href=""></a>&gt;)
1882               </li>
1883               <li>&lt;<a href=""></a>&gt;: "Revise description of the POST method" (&lt;<a href=""></a>&gt;)
1884               </li>
1885               <li>&lt;<a href=""></a>&gt;: "Normative and Informative references"
1886               </li>
1887               <li>&lt;<a href=""></a>&gt;: "RFC2606 Compliance"
1888               </li>
1889               <li>&lt;<a href=""></a>&gt;: "Informative references"
1890               </li>
1891               <li>&lt;<a href=""></a>&gt;: "Redundant cross-references"
1892               </li>
1893            </ul>
1894            <p id="rfc.section.B.2.p.2">Other changes: </p>
1895            <ul>
1896               <li>Move definitions of 304 and 412 condition codes to <a href="#Part4" id="rfc.xref.Part4.14"><cite title="HTTP/1.1, part 4: Conditional Requests">[Part4]</cite></a>
1897               </li>
1898            </ul>
1899         </div>
1900         <div>
1901            <h2 id="rfc.section.B.3"><a href="#rfc.section.B.3">B.3</a>&nbsp;Since draft-ietf-httpbis-p2-semantics-01
1902            </h2>
1903            <p id="rfc.section.B.3.p.1">Closed issues: </p>
1904            <ul>
1905               <li>&lt;<a href=""></a>&gt;: "PUT side effects"
1906               </li>
1907               <li>&lt;<a href=""></a>&gt;: "Duplicate Host header requirements"
1908               </li>
1909            </ul>
1910            <p id="rfc.section.B.3.p.2">Ongoing work on ABNF conversion (&lt;<a href=""></a>&gt;):
1911            </p>
1912            <ul>
1913               <li>Move "Product Tokens" section (back) into Part 1, as "token" is used in the definition of the Upgrade header.</li>
1914               <li>Add explicit references to BNF syntax and rules imported from other parts of the specification.</li>
1915               <li>Copy definition of delta-seconds from Part6 instead of referencing it.</li>
1916            </ul>
1917         </div>
1918      </div>
1919      <h1 id="rfc.index"><a href="#rfc.index">Index</a></h1>
1920      <p class="noprint"><a href="#rfc.index.1">1</a> <a href="#rfc.index.2">2</a> <a href="#rfc.index.3">3</a> <a href="#rfc.index.4">4</a> <a href="#rfc.index.5">5</a> <a href="#rfc.index.A">A</a> <a href="#rfc.index.C">C</a> <a href="#rfc.index.D">D</a> <a href="#rfc.index.E">E</a> <a href="#rfc.index.F">F</a> <a href="#rfc.index.G">G</a> <a href="#rfc.index.H">H</a> <a href="#rfc.index.L">L</a> <a href="#rfc.index.M">M</a> <a href="#rfc.index.O">O</a> <a href="#rfc.index.P">P</a> <a href="#rfc.index.R">R</a> <a href="#rfc.index.S">S</a> <a href="#rfc.index.T">T</a> <a href="#rfc.index.U">U</a>
1921      </p>
1922      <div class="print2col">
1923         <ul class="ind">
1924            <li><a id="rfc.index.1" href="#rfc.index.1"><b>1</b></a><ul>
1925                  <li>100 Continue (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.100.1">5</a>, <a href="#rfc.iref.1.1"><b>9.1.1</b></a></li>
1926                  <li>101 Switching Protocols (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.101.1">5</a>, <a href="#rfc.iref.1.2"><b>9.1.2</b></a></li>
1927               </ul>
1928            </li>
1929            <li><a id="rfc.index.2" href="#rfc.index.2"><b>2</b></a><ul>
1930                  <li>200 OK (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.200.1">5</a>, <a href="#rfc.iref.2.1"><b>9.2.1</b></a></li>
1931                  <li>201 Created (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.201.1">5</a>, <a href="#rfc.iref.2.2"><b>9.2.2</b></a>, <a href="#rfc.xref.status.201.2">A.1</a></li>
1932                  <li>202 Accepted (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.202.1">5</a>, <a href="#rfc.iref.2.3"><b>9.2.3</b></a></li>
1933                  <li>203 Non-Authoritative Information (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.203.1">5</a>, <a href="#rfc.iref.2.4"><b>9.2.4</b></a></li>
1934                  <li>204 No Content (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.204.1">5</a>, <a href="#rfc.iref.2.5"><b>9.2.5</b></a></li>
1935                  <li>205 Reset Content (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.205.1">5</a>, <a href="#rfc.iref.2.6"><b>9.2.6</b></a></li>
1936                  <li>206 Partial Content (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.206.1">5</a>, <a href="#rfc.iref.2.7"><b>9.2.7</b></a></li>
1937               </ul>
1938            </li>
1939            <li><a id="rfc.index.3" href="#rfc.index.3"><b>3</b></a><ul>
1940                  <li>300 Multiple Choices (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.300.1">5</a>, <a href="#rfc.iref.3.1"><b>9.3.1</b></a></li>
1941                  <li>301 Moved Permanently (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.301.1">5</a>, <a href="#rfc.iref.3.2"><b>9.3.2</b></a>, <a href="#rfc.xref.status.301.2">A.2</a></li>
1942                  <li>302 Found (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.302.1">5</a>, <a href="#rfc.iref.3.3"><b>9.3.3</b></a>, <a href="#rfc.xref.status.302.2">A.2</a></li>
1943                  <li>303 See Other (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.303.1">5</a>, <a href="#rfc.iref.3.4"><b>9.3.4</b></a></li>
1944                  <li>304 Not Modified (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.304.1">5</a>, <a href="#rfc.iref.3.5"><b>9.3.5</b></a></li>
1945                  <li>305 Use Proxy (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.305.1">5</a>, <a href="#rfc.iref.3.6"><b>9.3.6</b></a></li>
1946                  <li>306 (Unused) (status code)&nbsp;&nbsp;<a href="#rfc.iref.3.7"><b>9.3.7</b></a></li>
1947                  <li>307 Temporary Redirect (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.307.1">5</a>, <a href="#rfc.iref.3.8"><b>9.3.8</b></a>, <a href="#rfc.xref.status.307.2">A.2</a></li>
1948               </ul>
1949            </li>
1950            <li><a id="rfc.index.4" href="#rfc.index.4"><b>4</b></a><ul>
1951                  <li>400 Bad Request (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.400.1">5</a>, <a href="#rfc.iref.4.1"><b>9.4.1</b></a></li>
1952                  <li>401 Unauthorized (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.401.1">5</a>, <a href="#rfc.iref.4.2"><b>9.4.2</b></a></li>
1953                  <li>402 Payment Required (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.402.1">5</a>, <a href="#rfc.iref.4.3"><b>9.4.3</b></a></li>
1954                  <li>403 Forbidden (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.403.1">5</a>, <a href="#rfc.iref.4.4"><b>9.4.4</b></a>, <a href="#rfc.xref.status.403.2">A.1</a></li>
1955                  <li>404 Not Found (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.404.1">5</a>, <a href="#rfc.iref.4.5"><b>9.4.5</b></a>, <a href="#rfc.xref.status.404.2">A.1</a></li>
1956                  <li>405 Method Not Allowed (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.405.1">5</a>, <a href="#rfc.iref.4.6"><b>9.4.6</b></a></li>
1957                  <li>406 Not Acceptable (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.406.1">5</a>, <a href="#rfc.iref.4.7"><b>9.4.7</b></a></li>
1958                  <li>407 Proxy Authentication Required (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.407.1">5</a>, <a href="#rfc.iref.4.8"><b>9.4.8</b></a></li>
1959                  <li>408 Request Timeout (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.408.1">5</a>, <a href="#rfc.iref.4.9"><b>9.4.9</b></a></li>
1960                  <li>409 Conflict (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.409.1">5</a>, <a href="#rfc.iref.4.10"><b>9.4.10</b></a></li>
1961                  <li>410 Gone (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.410.1">5</a>, <a href="#rfc.iref.4.11"><b>9.4.11</b></a>, <a href="#rfc.xref.status.410.2">A.1</a></li>
1962                  <li>411 Length Required (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.411.1">5</a>, <a href="#rfc.iref.4.12"><b>9.4.12</b></a></li>
1963                  <li>412 Precondition Failed (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.412.1">5</a>, <a href="#rfc.iref.4.13"><b>9.4.13</b></a></li>
1964                  <li>413 Request Entity Too Large (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.413.1">5</a>, <a href="#rfc.iref.4.14"><b>9.4.14</b></a></li>
1965                  <li>414 Request-URI Too Long (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.414.1">5</a>, <a href="#rfc.iref.4.15"><b>9.4.15</b></a></li>
1966                  <li>415 Unsupported Media Type (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.415.1">5</a>, <a href="#rfc.iref.4.16"><b>9.4.16</b></a></li>
1967                  <li>416 Requested Range Not Satisfiable (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.416.1">5</a>, <a href="#rfc.iref.4.17"><b>9.4.17</b></a></li>
1968                  <li>417 Expectation Failed (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.417.1">5</a>, <a href="#rfc.iref.4.18"><b>9.4.18</b></a></li>
1969               </ul>
1970            </li>
1971            <li><a id="rfc.index.5" href="#rfc.index.5"><b>5</b></a><ul>
1972                  <li>500 Internal Server Error (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.500.1">5</a>, <a href="#rfc.iref.5.1"><b>9.5.1</b></a></li>
1973                  <li>501 Not Implemented (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.501.1">5</a>, <a href="#rfc.iref.5.2"><b>9.5.2</b></a></li>
1974                  <li>502 Bad Gateway (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.502.1">5</a>, <a href="#rfc.iref.5.3"><b>9.5.3</b></a></li>
1975                  <li>503 Service Unavailable (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.503.1">5</a>, <a href="#rfc.iref.5.4"><b>9.5.4</b></a></li>
1976                  <li>504 Gateway Timeout (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.504.1">5</a>, <a href="#rfc.iref.5.5"><b>9.5.5</b></a>, <a href="#rfc.xref.status.504.2">A.1</a></li>
1977                  <li>505 HTTP Version Not Supported (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.505.1">5</a>, <a href="#rfc.iref.5.6"><b>9.5.6</b></a></li>
1978               </ul>
1979            </li>
1980            <li><a id="rfc.index.A" href="#rfc.index.A"><b>A</b></a><ul>
1981                  <li>Allow header&nbsp;&nbsp;<a href="#rfc.xref.header.allow.1">3</a>, <a href="#rfc.iref.a.1"><b>10.1</b></a></li>
1982               </ul>
1983            </li>
1984            <li><a id="rfc.index.C" href="#rfc.index.C"><b>C</b></a><ul>
1985                  <li>CONNECT method&nbsp;&nbsp;<a href="#rfc.xref.CONNECT.1">3</a>, <a href="#rfc.iref.c.1"><b>8.9</b></a></li>
1986               </ul>
1987            </li>
1988            <li><a id="rfc.index.D" href="#rfc.index.D"><b>D</b></a><ul>
1989                  <li>DELETE method&nbsp;&nbsp;<a href="#rfc.xref.DELETE.1">3</a>, <a href="#rfc.iref.d.1"><b>8.7</b></a></li>
1990               </ul>
1991            </li>
1992            <li><a id="rfc.index.E" href="#rfc.index.E"><b>E</b></a><ul>
1993                  <li>Expect header&nbsp;&nbsp;<a href="#rfc.xref.header.expect.1">4</a>, <a href="#rfc.xref.header.expect.2">9.4.18</a>, <a href="#rfc.iref.e.1"><b>10.2</b></a></li>
1994               </ul>
1995            </li>
1996            <li><a id="rfc.index.F" href="#rfc.index.F"><b>F</b></a><ul>
1997                  <li>From header&nbsp;&nbsp;<a href="#rfc.xref.header.from.1">4</a>, <a href="#rfc.iref.f.1"><b>10.3</b></a></li>
1998               </ul>
1999            </li>
2000            <li><a id="rfc.index.G" href="#rfc.index.G"><b>G</b></a><ul>
2001                  <li>GET method&nbsp;&nbsp;<a href="#rfc.xref.GET.1">3</a>, <a href="#rfc.iref.g.8"><b>8.3</b></a></li>
2002                  <li><tt>Grammar</tt>&nbsp;&nbsp;
2003                     <ul>
2004                        <li><tt>Allow</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.9"><b>10.1</b></a></li>
2005                        <li><tt>delta-seconds</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.19"><b>10.7</b></a></li>
2006                        <li><tt>Expect</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.10"><b>10.2</b></a></li>
2007                        <li><tt>expect-params</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.13"><b>10.2</b></a></li>
2008                        <li><tt>expectation</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.11"><b>10.2</b></a></li>
2009                        <li><tt>expectation-extension</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.12"><b>10.2</b></a></li>
2010                        <li><tt>extension-code</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.5"><b>5</b></a></li>
2011                        <li><tt>extension-method</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.2"><b>3</b></a></li>
2012                        <li><tt>From</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.14"><b>10.3</b></a></li>
2013                        <li><tt>Location</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.15"><b>10.4</b></a></li>
2014                        <li><tt>Max-Forwards</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.16"><b>10.5</b></a></li>
2015                        <li><tt>Method</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.1"><b>3</b></a></li>
2016                        <li><tt>Reason-Phrase</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.6"><b>5</b></a></li>
2017                        <li><tt>Referer</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.17"><b>10.6</b></a></li>
2018                        <li><tt>request-header</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.3"><b>4</b></a></li>
2019                        <li><tt>response-header</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.7"><b>6</b></a></li>
2020                        <li><tt>Retry-After</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.18"><b>10.7</b></a></li>
2021                        <li><tt>Server</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.20"><b>10.8</b></a></li>
2022                        <li><tt>Status-Code</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.4"><b>5</b></a></li>
2023                        <li><tt>User-Agent</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.21"><b>10.9</b></a></li>
2024                     </ul>
2025                  </li>
2026               </ul>
2027            </li>
2028            <li><a id="rfc.index.H" href="#rfc.index.H"><b>H</b></a><ul>
2029                  <li>HEAD method&nbsp;&nbsp;<a href="#rfc.xref.HEAD.1">3</a>, <a href="#rfc.iref.h.1"><b>8.4</b></a></li>
2030                  <li>Headers&nbsp;&nbsp;
2031                     <ul>
2032                        <li>Allow&nbsp;&nbsp;<a href="#rfc.xref.header.allow.1">3</a>, <a href="#rfc.iref.h.2"><b>10.1</b></a></li>
2033                        <li>Expect&nbsp;&nbsp;<a href="#rfc.xref.header.expect.1">4</a>, <a href="#rfc.xref.header.expect.2">9.4.18</a>, <a href="#rfc.iref.h.3"><b>10.2</b></a></li>
2034                        <li>From&nbsp;&nbsp;<a href="#rfc.xref.header.from.1">4</a>, <a href="#rfc.iref.h.4"><b>10.3</b></a></li>
2035                        <li>Location&nbsp;&nbsp;<a href="#rfc.xref.header.location.1">6</a>, <a href="#rfc.xref.header.location.2">8.5</a>, <a href="#rfc.iref.h.5"><b>10.4</b></a>, <a href="#rfc.xref.header.location.3">A.2</a></li>
2036                        <li>Max-Forwards&nbsp;&nbsp;<a href="#rfc.xref.header.max-forwards.1">4</a>, <a href="#rfc.xref.header.max-forwards.2">8.8</a>, <a href="#rfc.iref.h.6"><b>10.5</b></a></li>
2037                        <li>Referer&nbsp;&nbsp;<a href="#rfc.xref.header.referer.1">4</a>, <a href="#rfc.iref.h.7"><b>10.6</b></a></li>
2038                        <li>Retry-After&nbsp;&nbsp;<a href="#rfc.xref.header.retry-after.1">6</a>, <a href="#rfc.iref.h.8"><b>10.7</b></a></li>
2039                        <li>Server&nbsp;&nbsp;<a href="#rfc.xref.header.server.1">6</a>, <a href="#rfc.iref.h.9"><b>10.8</b></a>, <a href="#rfc.xref.header.server.2">12.1</a>, <a href="#rfc.xref.header.server.3">A.2</a></li>
2040                        <li>User-Agent&nbsp;&nbsp;<a href="#rfc.xref.header.user-agent.1">4</a>, <a href="#rfc.iref.h.10"><b>10.9</b></a>, <a href="#rfc.xref.header.user-agent.2">12.1</a></li>
2041                     </ul>
2042                  </li>
2043               </ul>
2044            </li>
2045            <li><a id="rfc.index.L" href="#rfc.index.L"><b>L</b></a><ul>
2046                  <li>LINK method&nbsp;&nbsp;<a href="#rfc.iref.l.2"><b>A.1</b></a></li>
2047                  <li>Location header&nbsp;&nbsp;<a href="#rfc.xref.header.location.1">6</a>, <a href="#rfc.xref.header.location.2">8.5</a>, <a href="#rfc.iref.l.1"><b>10.4</b></a>, <a href="#rfc.xref.header.location.3">A.2</a></li>
2048                  <li><em>Luo1998</em>&nbsp;&nbsp;<a href="#rfc.xref.Luo1998.1">8.9</a>, <a href="#Luo1998"><b>14.2</b></a></li>
2049               </ul>
2050            </li>
2051            <li><a id="rfc.index.M" href="#rfc.index.M"><b>M</b></a><ul>
2052                  <li>Max-Forwards header&nbsp;&nbsp;<a href="#rfc.xref.header.max-forwards.1">4</a>, <a href="#rfc.xref.header.max-forwards.2">8.8</a>, <a href="#rfc.iref.m.9"><b>10.5</b></a></li>
2053                  <li>Methods&nbsp;&nbsp;
2054                     <ul>
2055                        <li>CONNECT&nbsp;&nbsp;<a href="#rfc.xref.CONNECT.1">3</a>, <a href="#rfc.iref.m.8"><b>8.9</b></a></li>
2056                        <li>DELETE&nbsp;&nbsp;<a href="#rfc.xref.DELETE.1">3</a>, <a href="#rfc.iref.m.6"><b>8.7</b></a></li>
2057                        <li>GET&nbsp;&nbsp;<a href="#rfc.xref.GET.1">3</a>, <a href="#rfc.iref.m.2"><b>8.3</b></a></li>
2058                        <li>HEAD&nbsp;&nbsp;<a href="#rfc.xref.HEAD.1">3</a>, <a href="#rfc.iref.m.3"><b>8.4</b></a></li>
2059                        <li>LINK&nbsp;&nbsp;<a href="#rfc.iref.m.11"><b>A.1</b></a></li>
2060                        <li>OPTIONS&nbsp;&nbsp;<a href="#rfc.xref.OPTIONS.1">3</a>, <a href="#rfc.iref.m.1"><b>8.2</b></a>, <a href="#rfc.xref.OPTIONS.2">10.5</a></li>
2061                        <li>PATCH&nbsp;&nbsp;<a href="#rfc.iref.m.10"><b>A.1</b></a></li>
2062                        <li>POST&nbsp;&nbsp;<a href="#rfc.xref.POST.1">3</a>, <a href="#rfc.iref.m.4"><b>8.5</b></a>, <a href="#rfc.xref.POST.2">A.2</a></li>
2063                        <li>PUT&nbsp;&nbsp;<a href="#rfc.xref.PUT.1">3</a>, <a href="#rfc.iref.m.5"><b>8.6</b></a></li>
2064                        <li>TRACE&nbsp;&nbsp;<a href="#rfc.xref.TRACE.1">3</a>, <a href="#rfc.iref.m.7"><b>8.8</b></a>, <a href="#rfc.xref.TRACE.2">10.5</a></li>
2065                        <li>UNLINK&nbsp;&nbsp;<a href="#rfc.iref.m.12"><b>A.1</b></a></li>
2066                     </ul>
2067                  </li>
2068               </ul>
2069            </li>
2070            <li><a id="rfc.index.O" href="#rfc.index.O"><b>O</b></a><ul>
2071                  <li>OPTIONS method&nbsp;&nbsp;<a href="#rfc.xref.OPTIONS.1">3</a>, <a href="#rfc.iref.o.1"><b>8.2</b></a>, <a href="#rfc.xref.OPTIONS.2">10.5</a></li>
2072               </ul>
2073            </li>
2074            <li><a id="rfc.index.P" href="#rfc.index.P"><b>P</b></a><ul>
2075                  <li><em>Part1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.1">1</a>, <a href="#rfc.xref.Part1.2">2</a>, <a href="#rfc.xref.Part1.3">2</a>, <a href="#rfc.xref.Part1.4">2</a>, <a href="#rfc.xref.Part1.5">2</a>, <a href="#rfc.xref.Part1.6">2</a>, <a href="#rfc.xref.Part1.7">2</a>, <a href="#rfc.xref.Part1.8">2</a>, <a href="#rfc.xref.Part1.9">2</a>, <a href="#rfc.xref.Part1.10">2</a>, <a href="#rfc.xref.Part1.11">2</a>, <a href="#rfc.xref.Part1.12">2</a>, <a href="#rfc.xref.Part1.13">2</a>, <a href="#rfc.xref.Part1.14">2</a>, <a href="#rfc.xref.Part1.15">4</a>, <a href="#rfc.xref.Part1.16">4</a>, <a href="#rfc.xref.Part1.17">7</a>, <a href="#rfc.xref.Part1.18">8.8</a>, <a href="#rfc.xref.Part1.19">9.1.1</a>, <a href="#rfc.xref.Part1.20">9.5.6</a>, <a href="#rfc.xref.Part1.21">10.2</a>, <a href="#rfc.xref.Part1.22">10.8</a>, <a href="#rfc.xref.Part1.23">10.8</a>, <a href="#rfc.xref.Part1.24">10.9</a>, <a href="#Part1"><b>14.1</b></a>, <a href="#rfc.xref.Part1.25">A.2</a><ul>
2076                        <li><em>Section 2.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.2">2</a></li>
2077                        <li><em>Section 2.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.3">2</a>, <a href="#rfc.xref.Part1.4">2</a>, <a href="#rfc.xref.Part1.5">2</a>, <a href="#rfc.xref.Part1.6">2</a>, <a href="#rfc.xref.Part1.7">2</a></li>
2078                        <li><em>Section 3.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.20">9.5.6</a></li>
2079                        <li><em>Section 3.2.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.8">2</a>, <a href="#rfc.xref.Part1.9">2</a>, <a href="#rfc.xref.Part1.13">2</a></li>
2080                        <li><em>Section 3.3.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.11">2</a></li>
2081                        <li><em>Section 3.5</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.12">2</a>, <a href="#rfc.xref.Part1.22">10.8</a>, <a href="#rfc.xref.Part1.24">10.9</a></li>
2082                        <li><em>Section 4.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.17">7</a></li>
2083                        <li><em>Section 7.2.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.19">9.1.1</a>, <a href="#rfc.xref.Part1.21">10.2</a></li>
2084                        <li><em>Section 8.4</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.10">2</a>, <a href="#rfc.xref.Part1.15">4</a></li>
2085                        <li><em>Section 8.8</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.14">2</a>, <a href="#rfc.xref.Part1.16">4</a></li>
2086                        <li><em>Section 8.9</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.18">8.8</a>, <a href="#rfc.xref.Part1.23">10.8</a>, <a href="#rfc.xref.Part1.25">A.2</a></li>
2087                     </ul>
2088                  </li>
2089                  <li><em>Part3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part3.1">2</a>, <a href="#rfc.xref.Part3.2">2</a>, <a href="#rfc.xref.Part3.3">2</a>, <a href="#rfc.xref.Part3.4">2</a>, <a href="#rfc.xref.Part3.5">4</a>, <a href="#rfc.xref.Part3.6">4</a>, <a href="#rfc.xref.Part3.7">4</a>, <a href="#rfc.xref.Part3.8">4</a>, <a href="#rfc.xref.Part3.9">7</a>, <a href="#rfc.xref.Part3.10">9.3.1</a>, <a href="#rfc.xref.Part3.11">10.4</a>, <a href="#Part3"><b>14.1</b></a><ul>
2090                        <li><em>Section 5</em>&nbsp;&nbsp;<a href="#rfc.xref.Part3.10">9.3.1</a></li>
2091                        <li><em>Section 6.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part3.1">2</a>, <a href="#rfc.xref.Part3.5">4</a></li>
2092                        <li><em>Section 6.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part3.2">2</a>, <a href="#rfc.xref.Part3.6">4</a></li>
2093                        <li><em>Section 6.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part3.3">2</a>, <a href="#rfc.xref.Part3.7">4</a></li>
2094                        <li><em>Section 6.4</em>&nbsp;&nbsp;<a href="#rfc.xref.Part3.4">2</a>, <a href="#rfc.xref.Part3.8">4</a></li>
2095                        <li><em>Section 6.7</em>&nbsp;&nbsp;<a href="#rfc.xref.Part3.11">10.4</a></li>
2096                     </ul>
2097                  </li>
2098                  <li><em>Part4</em>&nbsp;&nbsp;<a href="#rfc.xref.Part4.1">2</a>, <a href="#rfc.xref.Part4.2">2</a>, <a href="#rfc.xref.Part4.3">2</a>, <a href="#rfc.xref.Part4.4">2</a>, <a href="#rfc.xref.Part4.5">2</a>, <a href="#rfc.xref.Part4.6">4</a>, <a href="#rfc.xref.Part4.7">4</a>, <a href="#rfc.xref.Part4.8">4</a>, <a href="#rfc.xref.Part4.9">4</a>, <a href="#rfc.xref.Part4.10">6</a>, <a href="#rfc.xref.Part4.11">9.2.2</a>, <a href="#rfc.xref.Part4.12">9.3.5</a>, <a href="#rfc.xref.Part4.13">9.4.13</a>, <a href="#Part4"><b>14.1</b></a>, <a href="#rfc.xref.Part4.14">B.2</a><ul>
2099                        <li><em>Section 7.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part4.1">2</a>, <a href="#rfc.xref.Part4.10">6</a>, <a href="#rfc.xref.Part4.11">9.2.2</a></li>
2100                        <li><em>Section 7.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part4.2">2</a>, <a href="#rfc.xref.Part4.6">4</a></li>
2101                        <li><em>Section 7.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part4.3">2</a>, <a href="#rfc.xref.Part4.7">4</a></li>
2102                        <li><em>Section 7.4</em>&nbsp;&nbsp;<a href="#rfc.xref.Part4.4">2</a>, <a href="#rfc.xref.Part4.8">4</a></li>
2103                        <li><em>Section 7.5</em>&nbsp;&nbsp;<a href="#rfc.xref.Part4.5">2</a>, <a href="#rfc.xref.Part4.9">4</a></li>
2104                     </ul>
2105                  </li>
2106                  <li><em>Part5</em>&nbsp;&nbsp;<a href="#rfc.xref.Part5.1">2</a>, <a href="#rfc.xref.Part5.2">2</a>, <a href="#rfc.xref.Part5.3">2</a>, <a href="#rfc.xref.Part5.4">4</a>, <a href="#rfc.xref.Part5.5">4</a>, <a href="#rfc.xref.Part5.6">6</a>, <a href="#rfc.xref.Part5.7">8.3</a>, <a href="#rfc.xref.Part5.8">9.1.2</a>, <a href="#rfc.xref.Part5.9">9.2.7</a>, <a href="#rfc.xref.Part5.10">9.4.17</a>, <a href="#Part5"><b>14.1</b></a><ul>
2107                        <li><em>Section 6.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part5.1">2</a>, <a href="#rfc.xref.Part5.6">6</a></li>
2108                        <li><em>Section 6.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part5.2">2</a>, <a href="#rfc.xref.Part5.4">4</a></li>
2109                        <li><em>Section 6.4</em>&nbsp;&nbsp;<a href="#rfc.xref.Part5.3">2</a>, <a href="#rfc.xref.Part5.5">4</a>, <a href="#rfc.xref.Part5.7">8.3</a>, <a href="#rfc.xref.Part5.8">9.1.2</a>, <a href="#rfc.xref.Part5.10">9.4.17</a></li>
2110                     </ul>
2111                  </li>
2112                  <li><em>Part6</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.1">2</a>, <a href="#rfc.xref.Part6.2">2</a>, <a href="#rfc.xref.Part6.3">6</a>, <a href="#rfc.xref.Part6.4">6</a>, <a href="#rfc.xref.Part6.5">8.3</a>, <a href="#Part6"><b>14.1</b></a><ul>
2113                        <li><em>Section 16.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.1">2</a>, <a href="#rfc.xref.Part6.3">6</a></li>
2114                        <li><em>Section 16.5</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.2">2</a>, <a href="#rfc.xref.Part6.4">6</a></li>
2115                     </ul>
2116                  </li>
2117                  <li><em>Part7</em>&nbsp;&nbsp;<a href="#rfc.xref.Part7.1">2</a>, <a href="#rfc.xref.Part7.2">2</a>, <a href="#rfc.xref.Part7.3">2</a>, <a href="#rfc.xref.Part7.4">2</a>, <a href="#rfc.xref.Part7.5">4</a>, <a href="#rfc.xref.Part7.6">4</a>, <a href="#rfc.xref.Part7.7">6</a>, <a href="#rfc.xref.Part7.8">6</a>, <a href="#rfc.xref.Part7.9">9.4.2</a>, <a href="#rfc.xref.Part7.10">9.4.8</a>, <a href="#Part7"><b>14.1</b></a><ul>
2118                        <li><em>Section 4.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part7.1">2</a>, <a href="#rfc.xref.Part7.5">4</a></li>
2119                        <li><em>Section 4.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part7.2">2</a>, <a href="#rfc.xref.Part7.7">6</a></li>
2120                        <li><em>Section 4.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part7.3">2</a>, <a href="#rfc.xref.Part7.6">4</a></li>
2121                        <li><em>Section 4.4</em>&nbsp;&nbsp;<a href="#rfc.xref.Part7.4">2</a>, <a href="#rfc.xref.Part7.8">6</a></li>
2122                     </ul>
2123                  </li>
2124                  <li>PATCH method&nbsp;&nbsp;<a href="#rfc.iref.p.3"><b>A.1</b></a></li>
2125                  <li>POST method&nbsp;&nbsp;<a href="#rfc.xref.POST.1">3</a>, <a href="#rfc.iref.p.1"><b>8.5</b></a>, <a href="#rfc.xref.POST.2">A.2</a></li>
2126                  <li>PUT method&nbsp;&nbsp;<a href="#rfc.xref.PUT.1">3</a>, <a href="#rfc.iref.p.2"><b>8.6</b></a></li>
2127               </ul>
2128            </li>
2129            <li><a id="rfc.index.R" href="#rfc.index.R"><b>R</b></a><ul>
2130                  <li>Referer header&nbsp;&nbsp;<a href="#rfc.xref.header.referer.1">4</a>, <a href="#rfc.iref.r.1"><b>10.6</b></a></li>
2131                  <li>Retry-After header&nbsp;&nbsp;<a href="#rfc.xref.header.retry-after.1">6</a>, <a href="#rfc.iref.r.2"><b>10.7</b></a></li>
2132                  <li><em>RFC1945</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC1945.1">9.3.3</a>, <a href="#RFC1945"><b>14.2</b></a></li>
2133                  <li><em>RFC2068</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2068.1">9.3.3</a>, <a href="#rfc.xref.RFC2068.2">9.3.6</a>, <a href="#RFC2068"><b>14.2</b></a>, <a href="#rfc.xref.RFC2068.3">A.1</a></li>
2134                  <li><em>RFC2119</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2119.1">1.1</a>, <a href="#RFC2119"><b>14.1</b></a></li>
2135                  <li><em>RFC2616</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2616.1">1</a>, <a href="#RFC2616"><b>14.2</b></a>, <a href="#rfc.xref.RFC2616.2">B.1</a></li>
2136                  <li><em>RFC2822</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2822.1">10.3</a>, <a href="#rfc.xref.RFC2822.2">10.3</a>, <a href="#RFC2822"><b>14.2</b></a><ul>
2137                        <li><em>Section 3.4</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2822.1">10.3</a>, <a href="#rfc.xref.RFC2822.2">10.3</a></li>
2138                     </ul>
2139                  </li>
2140               </ul>
2141            </li>
2142            <li><a id="rfc.index.S" href="#rfc.index.S"><b>S</b></a><ul>
2143                  <li>Server header&nbsp;&nbsp;<a href="#rfc.xref.header.server.1">6</a>, <a href="#rfc.iref.s.42"><b>10.8</b></a>, <a href="#rfc.xref.header.server.2">12.1</a>, <a href="#rfc.xref.header.server.3">A.2</a></li>
2144                  <li>Status Codes&nbsp;&nbsp;
2145                     <ul>
2146                        <li>100 Continue&nbsp;&nbsp;<a href="#rfc.xref.status.100.1">5</a>, <a href="#rfc.iref.s.1"><b>9.1.1</b></a></li>
2147                        <li>101 Switching Protocols&nbsp;&nbsp;<a href="#rfc.xref.status.101.1">5</a>, <a href="#rfc.iref.s.2"><b>9.1.2</b></a></li>
2148                        <li>200 OK&nbsp;&nbsp;<a href="#rfc.xref.status.200.1">5</a>, <a href="#rfc.iref.s.3"><b>9.2.1</b></a></li>
2149                        <li>201 Created&nbsp;&nbsp;<a href="#rfc.xref.status.201.1">5</a>, <a href="#rfc.iref.s.4"><b>9.2.2</b></a>, <a href="#rfc.xref.status.201.2">A.1</a></li>
2150                        <li>202 Accepted&nbsp;&nbsp;<a href="#rfc.xref.status.202.1">5</a>, <a href="#rfc.iref.s.5"><b>9.2.3</b></a></li>
2151                        <li>203 Non-Authoritative Information&nbsp;&nbsp;<a href="#rfc.xref.status.203.1">5</a>, <a href="#rfc.iref.s.6"><b>9.2.4</b></a></li>
2152                        <li>204 No Content&nbsp;&nbsp;<a href="#rfc.xref.status.204.1">5</a>, <a href="#rfc.iref.s.7"><b>9.2.5</b></a></li>
2153                        <li>205 Reset Content&nbsp;&nbsp;<a href="#rfc.xref.status.205.1">5</a>, <a href="#rfc.iref.s.8"><b>9.2.6</b></a></li>
2154                        <li>206 Partial Content&nbsp;&nbsp;<a href="#rfc.xref.status.206.1">5</a>, <a href="#rfc.iref.s.9"><b>9.2.7</b></a></li>
2155                        <li>300 Multiple Choices&nbsp;&nbsp;<a href="#rfc.xref.status.300.1">5</a>, <a href="#rfc.iref.s.10"><b>9.3.1</b></a></li>
2156                        <li>301 Moved Permanently&nbsp;&nbsp;<a href="#rfc.xref.status.301.1">5</a>, <a href="#rfc.iref.s.11"><b>9.3.2</b></a>, <a href="#rfc.xref.status.301.2">A.2</a></li>
2157                        <li>302 Found&nbsp;&nbsp;<a href="#rfc.xref.status.302.1">5</a>, <a href="#rfc.iref.s.12"><b>9.3.3</b></a>, <a href="#rfc.xref.status.302.2">A.2</a></li>
2158                        <li>303 See Other&nbsp;&nbsp;<a href="#rfc.xref.status.303.1">5</a>, <a href="#rfc.iref.s.13"><b>9.3.4</b></a></li>
2159                        <li>304 Not Modified&nbsp;&nbsp;<a href="#rfc.xref.status.304.1">5</a>, <a href="#rfc.iref.s.14"><b>9.3.5</b></a></li>
2160                        <li>305 Use Proxy&nbsp;&nbsp;<a href="#rfc.xref.status.305.1">5</a>, <a href="#rfc.iref.s.15"><b>9.3.6</b></a></li>
2161                        <li>306 (Unused)&nbsp;&nbsp;<a href="#rfc.iref.s.16"><b>9.3.7</b></a></li>
2162                        <li>307 Temporary Redirect&nbsp;&nbsp;<a href="#rfc.xref.status.307.1">5</a>, <a href="#rfc.iref.s.17"><b>9.3.8</b></a>, <a href="#rfc.xref.status.307.2">A.2</a></li>
2163                        <li>400 Bad Request&nbsp;&nbsp;<a href="#rfc.xref.status.400.1">5</a>, <a href="#rfc.iref.s.18"><b>9.4.1</b></a></li>
2164                        <li>401 Unauthorized&nbsp;&nbsp;<a href="#rfc.xref.status.401.1">5</a>, <a href="#rfc.iref.s.19"><b>9.4.2</b></a></li>
2165                        <li>402 Payment Required&nbsp;&nbsp;<a href="#rfc.xref.status.402.1">5</a>, <a href="#rfc.iref.s.20"><b>9.4.3</b></a></li>
2166                        <li>403 Forbidden&nbsp;&nbsp;<a href="#rfc.xref.status.403.1">5</a>, <a href="#rfc.iref.s.21"><b>9.4.4</b></a>, <a href="#rfc.xref.status.403.2">A.1</a></li>
2167                        <li>404 Not Found&nbsp;&nbsp;<a href="#rfc.xref.status.404.1">5</a>, <a href="#rfc.iref.s.22"><b>9.4.5</b></a>, <a href="#rfc.xref.status.404.2">A.1</a></li>
2168                        <li>405 Method Not Allowed&nbsp;&nbsp;<a href="#rfc.xref.status.405.1">5</a>, <a href="#rfc.iref.s.23"><b>9.4.6</b></a></li>
2169                        <li>406 Not Acceptable&nbsp;&nbsp;<a href="#rfc.xref.status.406.1">5</a>, <a href="#rfc.iref.s.24"><b>9.4.7</b></a></li>
2170                        <li>407 Proxy Authentication Required&nbsp;&nbsp;<a href="#rfc.xref.status.407.1">5</a>, <a href="#rfc.iref.s.25"><b>9.4.8</b></a></li>
2171                        <li>408 Request Timeout&nbsp;&nbsp;<a href="#rfc.xref.status.408.1">5</a>, <a href="#rfc.iref.s.26"><b>9.4.9</b></a></li>
2172                        <li>409 Conflict&nbsp;&nbsp;<a href="#rfc.xref.status.409.1">5</a>, <a href="#rfc.iref.s.27"><b>9.4.10</b></a></li>
2173                        <li>410 Gone&nbsp;&nbsp;<a href="#rfc.xref.status.410.1">5</a>, <a href="#rfc.iref.s.28"><b>9.4.11</b></a>, <a href="#rfc.xref.status.410.2">A.1</a></li>
2174                        <li>411 Length Required&nbsp;&nbsp;<a href="#rfc.xref.status.411.1">5</a>, <a href="#rfc.iref.s.29"><b>9.4.12</b></a></li>
2175                        <li>412 Precondition Failed&nbsp;&nbsp;<a href="#rfc.xref.status.412.1">5</a>, <a href="#rfc.iref.s.30"><b>9.4.13</b></a></li>
2176                        <li>413 Request Entity Too Large&nbsp;&nbsp;<a href="#rfc.xref.status.413.1">5</a>, <a href="#rfc.iref.s.31"><b>9.4.14</b></a></li>
2177                        <li>414 Request-URI Too Long&nbsp;&nbsp;<a href="#rfc.xref.status.414.1">5</a>, <a href="#rfc.iref.s.32"><b>9.4.15</b></a></li>
2178                        <li>415 Unsupported Media Type&nbsp;&nbsp;<a href="#rfc.xref.status.415.1">5</a>, <a href="#rfc.iref.s.33"><b>9.4.16</b></a></li>
2179                        <li>416 Requested Range Not Satisfiable&nbsp;&nbsp;<a href="#rfc.xref.status.416.1">5</a>, <a href="#rfc.iref.s.34"><b>9.4.17</b></a></li>
2180                        <li>417 Expectation Failed&nbsp;&nbsp;<a href="#rfc.xref.status.417.1">5</a>, <a href="#rfc.iref.s.35"><b>9.4.18</b></a></li>
2181                        <li>500 Internal Server Error&nbsp;&nbsp;<a href="#rfc.xref.status.500.1">5</a>, <a href="#rfc.iref.s.36"><b>9.5.1</b></a></li>
2182                        <li>501 Not Implemented&nbsp;&nbsp;<a href="#rfc.xref.status.501.1">5</a>, <a href="#rfc.iref.s.37"><b>9.5.2</b></a></li>
2183                        <li>502 Bad Gateway&nbsp;&nbsp;<a href="#rfc.xref.status.502.1">5</a>, <a href="#rfc.iref.s.38"><b>9.5.3</b></a></li>
2184                        <li>503 Service Unavailable&nbsp;&nbsp;<a href="#rfc.xref.status.503.1">5</a>, <a href="#rfc.iref.s.39"><b>9.5.4</b></a></li>
2185                        <li>504 Gateway Timeout&nbsp;&nbsp;<a href="#rfc.xref.status.504.1">5</a>, <a href="#rfc.iref.s.40"><b>9.5.5</b></a>, <a href="#rfc.xref.status.504.2">A.1</a></li>
2186                        <li>505 HTTP Version Not Supported&nbsp;&nbsp;<a href="#rfc.xref.status.505.1">5</a>, <a href="#rfc.iref.s.41"><b>9.5.6</b></a></li>
2187                     </ul>
2188                  </li>
2189               </ul>
2190            </li>
2191            <li><a id="rfc.index.T" href="#rfc.index.T"><b>T</b></a><ul>
2192                  <li>TRACE method&nbsp;&nbsp;<a href="#rfc.xref.TRACE.1">3</a>, <a href="#rfc.iref.t.1"><b>8.8</b></a>, <a href="#rfc.xref.TRACE.2">10.5</a></li>
2193               </ul>
2194            </li>
2195            <li><a id="rfc.index.U" href="#rfc.index.U"><b>U</b></a><ul>
2196                  <li>UNLINK method&nbsp;&nbsp;<a href="#rfc.iref.u.2"><b>A.1</b></a></li>
2197                  <li>User-Agent header&nbsp;&nbsp;<a href="#rfc.xref.header.user-agent.1">4</a>, <a href="#rfc.iref.u.1"><b>10.9</b></a>, <a href="#rfc.xref.header.user-agent.2">12.1</a></li>
2198               </ul>
2199            </li>
2200         </ul>
2201      </div>
2202      <div class="avoidbreak">
2203         <h1 id="rfc.authors"><a href="#rfc.authors">Authors' Addresses</a></h1>
2204         <p><b>Roy T. Fielding</b>
2205            (editor)
2206            <br>Day Software<br>23 Corporate Plaza DR, Suite 280<br>Newport Beach, CA&nbsp;92660<br>USA<br>Phone: <a href="tel:+1-949-706-5300">+1-949-706-5300</a><br>Fax: <a href="fax:+1-949-706-5305">+1-949-706-5305</a><br>EMail: <a href=""></a><br>URI: <a href=""></a></p>
2207         <p><b>Jim Gettys</b><br>One Laptop per Child<br>21 Oak Knoll Road<br>Carlisle, MA&nbsp;01741<br>USA<br>EMail: <a href=""></a><br>URI: <a href=""></a></p>
2208         <p><b>Jeffrey C. Mogul</b><br>Hewlett-Packard Company<br>HP Labs, Large Scale Systems Group<br>1501 Page Mill Road, MS 1177<br>Palo Alto, CA&nbsp;94304<br>USA<br>EMail: <a href=""></a></p>
2209         <p><b>Henrik Frystyk Nielsen</b><br>Microsoft Corporation<br>1 Microsoft Way<br>Redmond, WA&nbsp;98052<br>USA<br>EMail: <a href=""></a></p>
2210         <p><b>Larry Masinter</b><br>Adobe Systems, Incorporated<br>345 Park Ave<br>San Jose, CA&nbsp;95110<br>USA<br>EMail: <a href=""></a><br>URI: <a href=""></a></p>
2211         <p><b>Paul J. Leach</b><br>Microsoft Corporation<br>1 Microsoft Way<br>Redmond, WA&nbsp;98052<br>EMail: <a href=""></a></p>
2212         <p><b>Tim Berners-Lee</b><br>World Wide Web Consortium<br>MIT Computer Science and Artificial Intelligence Laboratory<br>The Stata Center, Building 32<br>32 Vassar Street<br>Cambridge, MA&nbsp;02139<br>USA<br>EMail: <a href=""></a><br>URI: <a href=""></a></p>
2213         <p><b>Yves Lafon</b>
2214            (editor)
2215            <br>World Wide Web Consortium<br>W3C / ERCIM<br>2004, rte des Lucioles<br>Sophia-Antipolis, AM&nbsp;06902<br>France<br>EMail: <a href=""></a><br>URI: <a href=""></a></p>
2216         <p><b>Julian F. Reschke</b>
2217            (editor)
2218            <br>greenbytes GmbH<br>Hafenweg 16<br>Muenster, NW&nbsp;48155<br>Germany<br>Phone: <a href="tel:+492512807760">+49 251 2807760</a><br>Fax: <a href="fax:+492512807761">+49 251 2807761</a><br>EMail: <a href=""></a><br>URI: <a href=""></a></p>
2219      </div>
2220      <div id="rfc.copyright">
2221         <h1><a href="#rfc.copyright">Full Copyright Statement</a></h1>
2222         <p>Copyright © The IETF Trust (2008).</p>
2223         <p>This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the
2224            authors retain all their rights.
2225         </p>
2226         <p>This document and the information contained herein are provided on an “AS IS” basis and THE CONTRIBUTOR, THE ORGANIZATION
2230         </p>
2231      </div>
2232      <div id="rfc.ipr">
2233         <h1><a href="#rfc.ipr">Intellectual Property</a></h1>
2234         <p>The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might
2235            be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any
2236            license under such rights might or might not be available; nor does it represent that it has made any independent effort to
2237            identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and
2238            BCP 79.
2239         </p>
2240         <p>Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result
2241            of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users
2242            of this specification can be obtained from the IETF on-line IPR repository at <a href=""></a>.
2243         </p>
2244         <p>The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary
2245            rights that may cover technology that may be required to implement this standard. Please address the information to the IETF
2246            at <a href=""></a>.
2247         </p>
2248      </div>
2249   </body>
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