source: draft-ietf-httpbis/13/draft-ietf-httpbis-p2-semantics-13.xml

Last change on this file was 1500, checked in by julian.reschke@…, 8 years ago

fix mime types

  • Property svn:eol-style set to native
  • Property svn:mime-type set to text/xml
File size: 153.9 KB
Line 
1<?xml version="1.0" encoding="UTF-8"?>
2<!--
3    This XML document is the output of clean-for-DTD.xslt; a tool that strips
4    extensions to RFC2629(bis) from documents for processing with xml2rfc.
5-->
6<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
7<?rfc toc="yes" ?>
8<?rfc symrefs="yes" ?>
9<?rfc sortrefs="yes" ?>
10<?rfc compact="yes"?>
11<?rfc subcompact="no" ?>
12<?rfc linkmailto="no" ?>
13<?rfc editing="no" ?>
14<?rfc comments="yes"?>
15<?rfc inline="yes"?>
16<?rfc rfcedstyle="yes"?>
17<!DOCTYPE rfc
18  PUBLIC "" "rfc2629.dtd">
19<rfc obsoletes="2616" updates="2817" category="std" ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-13">
20<front>
21
22  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
23
24  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
25    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
26    <address>
27      <postal>
28        <street>345 Park Ave</street>
29        <city>San Jose</city>
30        <region>CA</region>
31        <code>95110</code>
32        <country>USA</country>
33      </postal>
34      <email>fielding@gbiv.com</email>
35      <uri>http://roy.gbiv.com/</uri>
36    </address>
37  </author>
38
39  <author initials="J." surname="Gettys" fullname="Jim Gettys">
40    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
41    <address>
42      <postal>
43        <street>21 Oak Knoll Road</street>
44        <city>Carlisle</city>
45        <region>MA</region>
46        <code>01741</code>
47        <country>USA</country>
48      </postal>
49      <email>jg@freedesktop.org</email>
50      <uri>http://gettys.wordpress.com/</uri>
51    </address>
52  </author>
53 
54  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
55    <organization abbrev="HP">Hewlett-Packard Company</organization>
56    <address>
57      <postal>
58        <street>HP Labs, Large Scale Systems Group</street>
59        <street>1501 Page Mill Road, MS 1177</street>
60        <city>Palo Alto</city>
61        <region>CA</region>
62        <code>94304</code>
63        <country>USA</country>
64      </postal>
65      <email>JeffMogul@acm.org</email>
66    </address>
67  </author>
68
69  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
70    <organization abbrev="Microsoft">Microsoft Corporation</organization>
71    <address>
72      <postal>
73        <street>1 Microsoft Way</street>
74        <city>Redmond</city>
75        <region>WA</region>
76        <code>98052</code>
77        <country>USA</country>
78      </postal>
79      <email>henrikn@microsoft.com</email>
80    </address>
81  </author>
82
83  <author initials="L." surname="Masinter" fullname="Larry Masinter">
84    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
85    <address>
86      <postal>
87        <street>345 Park Ave</street>
88        <city>San Jose</city>
89        <region>CA</region>
90        <code>95110</code>
91        <country>USA</country>
92      </postal>
93      <email>LMM@acm.org</email>
94      <uri>http://larry.masinter.net/</uri>
95    </address>
96  </author>
97 
98  <author initials="P." surname="Leach" fullname="Paul J. Leach">
99    <organization abbrev="Microsoft">Microsoft Corporation</organization>
100    <address>
101      <postal>
102        <street>1 Microsoft Way</street>
103        <city>Redmond</city>
104        <region>WA</region>
105        <code>98052</code>
106      </postal>
107      <email>paulle@microsoft.com</email>
108    </address>
109  </author>
110   
111  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
112    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
113    <address>
114      <postal>
115        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
116        <street>The Stata Center, Building 32</street>
117        <street>32 Vassar Street</street>
118        <city>Cambridge</city>
119        <region>MA</region>
120        <code>02139</code>
121        <country>USA</country>
122      </postal>
123      <email>timbl@w3.org</email>
124      <uri>http://www.w3.org/People/Berners-Lee/</uri>
125    </address>
126  </author>
127
128  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
129    <organization abbrev="W3C">World Wide Web Consortium</organization>
130    <address>
131      <postal>
132        <street>W3C / ERCIM</street>
133        <street>2004, rte des Lucioles</street>
134        <city>Sophia-Antipolis</city>
135        <region>AM</region>
136        <code>06902</code>
137        <country>France</country>
138      </postal>
139      <email>ylafon@w3.org</email>
140      <uri>http://www.raubacapeu.net/people/yves/</uri>
141    </address>
142  </author>
143
144  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
145    <organization abbrev="greenbytes">greenbytes GmbH</organization>
146    <address>
147      <postal>
148        <street>Hafenweg 16</street>
149        <city>Muenster</city><region>NW</region><code>48155</code>
150        <country>Germany</country>
151      </postal>
152      <phone>+49 251 2807760</phone>
153      <facsimile>+49 251 2807761</facsimile>
154      <email>julian.reschke@greenbytes.de</email>
155      <uri>http://greenbytes.de/tech/webdav/</uri>
156    </address>
157  </author>
158
159  <date month="March" year="2011" day="14"/>
160  <workgroup>HTTPbis Working Group</workgroup>
161
162<abstract>
163<t>
164   The Hypertext Transfer Protocol (HTTP) is an application-level
165   protocol for distributed, collaborative, hypermedia information
166   systems. HTTP has been in use by the World Wide Web global information
167   initiative since 1990. This document is Part 2 of the seven-part specification
168   that defines the protocol referred to as "HTTP/1.1" and, taken together,
169   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
170   as expressed by request methods, request header fields, response status codes,
171   and response header fields.
172</t>
173</abstract>
174
175<note title="Editorial Note (To be removed by RFC Editor)">
176  <t>
177    Discussion of this draft should take place on the HTTPBIS working group
178    mailing list (ietf-http-wg@w3.org). The current issues list is
179    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/>
180    and related documents (including fancy diffs) can be found at
181    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
182  </t>
183  <t>
184    The changes in this draft are summarized in <xref target="changes.since.12"/>.
185  </t>
186</note>
187</front>
188<middle>
189<section title="Introduction" anchor="introduction">
190<t>
191   This document defines HTTP/1.1 request and response semantics.  Each HTTP
192   message, as defined in <xref target="Part1"/>, is in the form of either a request or
193   a response.  An HTTP server listens on a connection for HTTP requests and
194   responds to each request, in the order received on that connection, with
195   one or more HTTP response messages.  This document defines the commonly
196   agreed upon semantics of the HTTP uniform interface, the intentions defined
197   by each request method, and the various response messages that might be
198   expected as a result of applying that method to the target resource.
199</t>
200<t>
201   This document is currently disorganized in order to minimize the changes
202   between drafts and enable reviewers to see the smaller errata changes.
203   A future draft will reorganize the sections to better reflect the content.
204   In particular, the sections will be ordered according to the typical
205   processing of an HTTP request message (after message parsing): resource
206   mapping, methods, request modifying header fields, response status,
207   status modifying header fields, and resource metadata.  The current mess
208   reflects how widely dispersed these topics and associated requirements
209   had become in <xref target="RFC2616"/>.
210</t>
211
212<section title="Requirements" anchor="intro.requirements">
213<t>
214   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
215   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
216   document are to be interpreted as described in <xref target="RFC2119"/>.
217</t>
218<t>
219   An implementation is not compliant if it fails to satisfy one or more
220   of the "MUST" or "REQUIRED" level requirements for the protocols it
221   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
222   level and all the "SHOULD" level requirements for its protocols is said
223   to be "unconditionally compliant"; one that satisfies all the "MUST"
224   level requirements but not all the "SHOULD" level requirements for its
225   protocols is said to be "conditionally compliant".
226</t>
227</section>
228
229<section title="Syntax Notation" anchor="notation">
230 
231 
232 
233 
234 
235<t>
236  This specification uses the ABNF syntax defined in Section 1.2 of <xref target="Part1"/> (which
237  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
238  <xref target="collected.abnf"/> shows the collected ABNF, with the list
239  rule expanded.
240</t>
241<t>
242  The following core rules are included by
243  reference, as defined in <xref target="RFC5234"/>, Appendix B.1:
244  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
245  DIGIT (decimal 0-9), DQUOTE (double quote),
246  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
247  OCTET (any 8-bit sequence of data), SP (space),
248  VCHAR (any visible USASCII character),
249  and WSP (whitespace).
250</t>
251
252<section title="Core Rules" anchor="core.rules">
253 
254 
255 
256 
257 
258<t>
259  The core rules below are defined in Section 1.2.2 of <xref target="Part1"/>:
260</t>
261<figure><artwork type="abnf2616"><![CDATA[
262  quoted-string = <quoted-string, defined in [Part1], Section 1.2.2>
263  token         = <token, defined in [Part1], Section 1.2.2>
264  OWS           = <OWS, defined in [Part1], Section 1.2.2>
265  RWS           = <RWS, defined in [Part1], Section 1.2.2>
266  obs-text      = <obs-text, defined in [Part1], Section 1.2.2>
267]]></artwork></figure>
268</section>
269
270<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
271 
272 
273 
274 
275 
276 
277<t>
278  The ABNF rules below are defined in other parts:
279</t>
280<figure><artwork type="abnf2616"><![CDATA[
281  absolute-URI  = <absolute-URI, defined in [Part1], Section 2.6>
282  comment       = <comment, defined in [Part1], Section 3.2>
283  HTTP-date     = <HTTP-date, defined in [Part1], Section 6.1>
284  partial-URI   = <partial-URI, defined in [Part1], Section 2.6>
285  product       = <product, defined in [Part1], Section 6.3>
286  URI-reference = <URI-reference, defined in [Part1], Section 2.6>
287]]></artwork></figure>
288</section>
289</section>
290</section>
291
292<section title="Method" anchor="method">
293 
294 
295<t>
296   The Method token indicates the request method to be performed on the target
297   resource (Section 4.3 of <xref target="Part1"/>). The method is case-sensitive.
298</t>
299<figure><iref primary="true" item="Grammar" subitem="Method"/><artwork type="abnf2616"><![CDATA[
300  Method         = token
301]]></artwork></figure>
302<t>
303   The list of methods allowed by a resource can be specified in an
304   Allow header field (<xref target="header.allow"/>). The status code of the response
305   always notifies the client whether a method is currently allowed on a
306   resource, since the set of allowed methods can change dynamically. An
307   origin server SHOULD respond with the status code 405 (Method Not Allowed)
308   if the method is known by the origin server but not allowed for the
309   resource, and 501 (Not Implemented) if the method is
310   unrecognized or not implemented by the origin server. The methods GET
311   and HEAD MUST be supported by all general-purpose servers. All other
312   methods are OPTIONAL; however, if the above methods are implemented,
313   they MUST be implemented with the same semantics as those specified
314   in <xref target="method.definitions"/>.
315</t>
316
317<section title="Overview of Methods" anchor="overview.of.methods">
318<t>
319  The methods listed below are defined in <xref target="method.definitions"/>.
320</t>
321<texttable align="left">
322  <ttcol>Method Name</ttcol><ttcol>Defined in...</ttcol>
323 
324  <c>OPTIONS</c> <c><xref target="OPTIONS"/></c>
325  <c>GET</c> <c><xref target="GET"/></c>
326  <c>HEAD</c> <c><xref target="HEAD"/></c>
327  <c>POST</c> <c><xref target="POST"/></c>
328  <c>PUT</c> <c><xref target="PUT"/></c>
329  <c>DELETE</c> <c><xref target="DELETE"/></c>
330  <c>TRACE</c> <c><xref target="TRACE"/></c>
331  <c>CONNECT</c> <c><xref target="CONNECT"/></c>
332</texttable>
333<t>
334  Note that this list is not exhaustive — it does not include request methods defined
335  in other specifications.
336</t>
337</section>
338
339<section title="Method Registry" anchor="method.registry">
340<t>
341  The HTTP Method Registry defines the name space for the Method token in the
342  Request line of an HTTP request.
343</t>
344<t>
345  Registrations MUST include the following fields:
346  <list style="symbols">
347    <t>Method Name (see <xref target="method"/>)</t>
348    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
349    <t>Pointer to specification text</t>
350  </list>
351</t>
352<t>
353  Values to be added to this name space are subject to IETF review
354  (<xref target="RFC5226"/>, Section 4.1).
355</t>
356<t>
357  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
358</t>
359
360<section title="Considerations for New Methods" anchor="considerations.for.new.methods">
361<t>
362   When it is necessary to express new semantics for a HTTP request that
363   aren't specific to a single application or media type, and currently defined
364   methods are inadequate, it may be appropriate to register a new method.
365</t>
366<t>
367   HTTP methods are generic; that is, they are potentially applicable to any
368   resource, not just one particular media type, "type" of resource, or
369   application. As such, it is preferred that new HTTP methods be registered
370   in a document that isn't specific to a single application, so that this is
371   clear.
372</t>
373<t>
374   Due to the parsing rules defined in Section 3.3 of <xref target="Part1"/>, definitions of HTTP
375   methods cannot prohibit the presence of a message-body on either the request
376   or the response message (with responses to HEAD requests being the single
377   exception). Definitions of new methods cannot change this rule, but they can
378   specify that only zero-length bodies (as opposed to absent bodies) are allowed.
379</t>
380<t>
381   New method definitions need to indicate whether they are safe (<xref target="safe.methods"/>) and whether they are idempotent (<xref target="idempotent.methods"/>). They also need to state whether they can be
382   cached (<xref target="Part6"/>); in particular what conditions a cache may store the
383   response, and under what conditions such a stored response may be used to
384   satisfy a subsequent request.
385</t>
386</section>
387
388</section>
389</section>
390
391<section title="Request Header Fields" anchor="request.header.fields">
392 
393<t>
394   The request header fields allow the client to pass additional
395   information about the request, and about the client itself, to the
396   server. These fields act as request modifiers, with semantics
397   equivalent to the parameters on a programming language method
398   invocation.
399</t>
400<texttable align="left">
401  <ttcol>Header Field Name</ttcol>
402  <ttcol>Defined in...</ttcol>
403
404  <c>Accept</c> <c>Section 6.1 of <xref target="Part3"/></c>
405  <c>Accept-Charset</c> <c>Section 6.2 of <xref target="Part3"/></c>
406  <c>Accept-Encoding</c> <c>Section 6.3 of <xref target="Part3"/></c>
407  <c>Accept-Language</c> <c>Section 6.4 of <xref target="Part3"/></c>
408  <c>Authorization</c> <c>Section 4.1 of <xref target="Part7"/></c>
409  <c>Expect</c> <c><xref target="header.expect"/></c>
410  <c>From</c> <c><xref target="header.from"/></c>
411  <c>Host</c> <c>Section 9.4 of <xref target="Part1"/></c>
412  <c>If-Match</c> <c>Section 6.2 of <xref target="Part4"/></c>
413  <c>If-Modified-Since</c> <c>Section 6.3 of <xref target="Part4"/></c>
414  <c>If-None-Match</c> <c>Section 6.4 of <xref target="Part4"/></c>
415  <c>If-Range</c> <c>Section 5.3 of <xref target="Part5"/></c>
416  <c>If-Unmodified-Since</c> <c>Section 6.5 of <xref target="Part4"/></c>
417  <c>Max-Forwards</c> <c><xref target="header.max-forwards"/></c>
418  <c>Proxy-Authorization</c> <c>Section 4.3 of <xref target="Part7"/></c>
419  <c>Range</c> <c>Section 5.4 of <xref target="Part5"/></c>
420  <c>Referer</c> <c><xref target="header.referer"/></c>
421  <c>TE</c> <c>Section 9.5 of <xref target="Part1"/></c>
422  <c>User-Agent</c> <c><xref target="header.user-agent"/></c>
423</texttable>
424</section>
425
426<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
427 
428 
429 
430<t>
431   The Status-Code element is a 3-digit integer result code of the attempt to
432   understand and satisfy the request.
433</t>
434<t>
435   The Reason-Phrase is intended to give a short textual description of the
436   Status-Code and is intended for a human user. The client does not need
437   to examine or display the Reason-Phrase.
438</t>
439<figure><iref primary="true" item="Grammar" subitem="Status-Code"/><iref primary="true" item="Grammar" subitem="extension-code"/><iref primary="true" item="Grammar" subitem="Reason-Phrase"/><artwork type="abnf2616"><![CDATA[
440  Status-Code    = 3DIGIT
441  Reason-Phrase  = *( WSP / VCHAR / obs-text )
442]]></artwork></figure>
443<t>
444   HTTP status codes are extensible. HTTP applications are not required
445   to understand the meaning of all registered status codes, though such
446   understanding is obviously desirable. However, applications MUST
447   understand the class of any status code, as indicated by the first
448   digit, and treat any unrecognized response as being equivalent to the
449   x00 status code of that class, with the exception that an
450   unrecognized response MUST NOT be cached. For example, if an
451   unrecognized status code of 431 is received by the client, it can
452   safely assume that there was something wrong with its request and
453   treat the response as if it had received a 400 status code. In such
454   cases, user agents SHOULD present to the user the representation enclosed
455   with the response, since that representation is likely to include human-readable
456   information which will explain the unusual status.
457</t>
458
459<section title="Overview of Status Codes" anchor="overview.of.status.codes">
460<t> 
461   The status codes listed below are defined in <xref target="status.codes"/>
462   of this specification, Section 3 of <xref target="Part4"/>, Section 3 of <xref target="Part5"/>, and Section 3 of <xref target="Part7"/>.
463   The reason phrases listed here are only recommendations — they can be
464   replaced by local equivalents without affecting the protocol.
465</t>
466<texttable align="left">
467  <ttcol>Status-Code</ttcol>
468  <ttcol>Reason-Phrase</ttcol>
469  <ttcol>Defined in...</ttcol>
470 
471  <c>100</c> <c>Continue</c> <c><xref target="status.100"/></c>
472  <c>101</c> <c>Switching Protocols</c> <c><xref target="status.101"/></c>
473
474  <c>200</c> <c>OK</c> <c><xref target="status.200"/></c>
475  <c>201</c> <c>Created</c> <c><xref target="status.201"/></c>
476  <c>202</c> <c>Accepted</c> <c><xref target="status.202"/></c>
477  <c>203</c> <c>Non-Authoritative Information</c> <c><xref target="status.203"/></c>
478  <c>204</c> <c>No Content</c> <c><xref target="status.204"/></c>
479  <c>205</c> <c>Reset Content</c> <c><xref target="status.205"/></c>
480  <c>206</c> <c>Partial Content</c> <c>Section 3.1 of <xref target="Part5"/></c>
481
482  <c>300</c> <c>Multiple Choices</c> <c><xref target="status.300"/></c>
483  <c>301</c> <c>Moved Permanently</c> <c><xref target="status.301"/></c>
484  <c>302</c> <c>Found</c> <c><xref target="status.302"/></c>
485  <c>303</c> <c>See Other</c> <c><xref target="status.303"/></c>
486  <c>304</c> <c>Not Modified</c> <c>Section 3.1 of <xref target="Part4"/></c>
487  <c>305</c> <c>Use Proxy</c> <c><xref target="status.305"/></c>
488  <c>307</c> <c>Temporary Redirect</c> <c><xref target="status.307"/></c>
489
490  <c>400</c> <c>Bad Request</c> <c><xref target="status.400"/></c>
491  <c>401</c> <c>Unauthorized</c> <c>Section 3.1 of <xref target="Part7"/></c>
492  <c>402</c> <c>Payment Required</c> <c><xref target="status.402"/></c>
493  <c>403</c> <c>Forbidden</c> <c><xref target="status.403"/></c>
494  <c>404</c> <c>Not Found</c> <c><xref target="status.404"/></c>
495  <c>405</c> <c>Method Not Allowed</c> <c><xref target="status.405"/></c>
496  <c>406</c> <c>Not Acceptable</c> <c><xref target="status.406"/></c>
497  <c>407</c> <c>Proxy Authentication Required</c> <c>Section 3.2 of <xref target="Part7"/></c>
498  <c>408</c> <c>Request Time-out</c> <c><xref target="status.408"/></c>
499  <c>409</c> <c>Conflict</c> <c><xref target="status.409"/></c>
500  <c>410</c> <c>Gone</c> <c><xref target="status.410"/></c>
501  <c>411</c> <c>Length Required</c> <c><xref target="status.411"/></c>
502  <c>412</c> <c>Precondition Failed</c> <c>Section 3.2 of <xref target="Part4"/></c>
503  <c>413</c> <c>Request Entity Too Large</c> <c><xref target="status.413"/></c>
504  <c>414</c> <c>URI Too Long</c> <c><xref target="status.414"/></c>
505  <c>415</c> <c>Unsupported Media Type</c> <c><xref target="status.415"/></c>
506  <c>416</c> <c>Requested range not satisfiable</c> <c>Section 3.2 of <xref target="Part5"/></c>
507  <c>417</c> <c>Expectation Failed</c> <c><xref target="status.417"/></c>
508  <c>426</c> <c>Upgrade Required</c> <c><xref target="status.426"/></c>
509
510  <c>500</c> <c>Internal Server Error</c> <c><xref target="status.500"/></c>
511  <c>501</c> <c>Not Implemented</c> <c><xref target="status.501"/></c>
512  <c>502</c> <c>Bad Gateway</c> <c><xref target="status.502"/></c>
513  <c>503</c> <c>Service Unavailable</c> <c><xref target="status.503"/></c>
514  <c>504</c> <c>Gateway Time-out</c> <c><xref target="status.504"/></c>
515  <c>505</c> <c>HTTP Version not supported</c> <c><xref target="status.505"/></c>
516</texttable>
517<t>
518   Note that this list is not exhaustive — it does not include
519   extension status codes defined in other specifications.
520</t>
521</section>
522
523<section title="Status Code Registry" anchor="status.code.registry">
524<t>
525  The HTTP Status Code Registry defines the name space for the Status-Code
526  token in the Status-Line of an HTTP response.
527</t>
528<t>
529  Values to be added to this name space are subject to IETF review
530  (<xref target="RFC5226"/>, Section 4.1).
531</t>
532<t>
533  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
534</t>
535
536<section title="Considerations for New Status Codes" anchor="considerations.for.new.status.codes">
537<t>
538   When it is necessary to express new semantics for a HTTP response that
539   aren't specific to a single application or media type, and currently defined
540   status codes are inadequate, a new status code can be registered.
541</t>
542<t>
543   HTTP status codes are generic; that is, they are potentially applicable to
544   any resource, not just one particular media type, "type" of resource, or
545   application. As such, it is preferred that new HTTP status codes be
546   registered in a document that isn't specific to a single application, so
547   that this is clear.
548</t>
549<t>
550   Definitions of new HTTP status codes typically explain the request
551   conditions that produce a response containing the status code (e.g.,
552   combinations of request headers and/or method(s)), along with any
553   interactions with response headers (e.g., those that are required, those
554   that modify the semantics of the response).
555</t>
556<t>
557   New HTTP status codes are required to fall under one of the categories
558   defined in <xref target="status.codes"/>. To allow existing parsers to
559   properly handle them, new status codes cannot disallow a response body,
560   although they can mandate a zero-length response body. They can require the
561   presence of one or more particular HTTP response header(s).
562</t>
563<t>
564   Likewise, their definitions can specify that caches are allowed to use
565   heuristics to determine their freshness (see <xref target="Part6"/>; by default, it is
566   not allowed), and can define how to determine the resource which they
567   carry a representation for (see <xref target="identifying.response.associated.with.representation"/>; by default,
568   it is anonymous).
569</t>
570</section>
571
572</section>
573
574</section>
575
576<section title="Response Header Fields" anchor="response.header.fields">
577 
578<t>
579   The response header fields allow the server to pass additional
580   information about the response which cannot be placed in the Status-Line.
581   These header fields give information about the server and about
582   further access to the target resource (Section 4.3 of <xref target="Part1"/>).
583</t>
584<texttable align="left">
585  <ttcol>Header Field Name</ttcol><ttcol>Defined in...</ttcol>
586
587  <c>Accept-Ranges</c> <c>Section 5.1 of <xref target="Part5"/></c>
588  <c>Age</c> <c>Section 3.1 of <xref target="Part6"/></c>
589  <c>Allow</c> <c><xref target="header.allow"/></c>
590  <c>ETag</c> <c>Section 6.1 of <xref target="Part4"/></c>
591  <c>Location</c> <c><xref target="header.location"/></c>
592  <c>Proxy-Authenticate</c> <c>Section 4.2 of <xref target="Part7"/></c>
593  <c>Retry-After</c> <c><xref target="header.retry-after"/></c>
594  <c>Server</c> <c><xref target="header.server"/></c>
595  <c>Vary</c> <c>Section 3.5 of <xref target="Part6"/></c>
596  <c>WWW-Authenticate</c> <c>Section 4.4 of <xref target="Part7"/></c>
597</texttable>
598</section>
599
600<section title="Representation" anchor="representation">
601<t>
602   Request and Response messages MAY transfer a representation if not otherwise
603   restricted by the request method or response status code. A representation
604   consists of metadata (representation header fields) and data (representation
605   body).  When a complete or partial representation is enclosed in an HTTP message,
606   it is referred to as the payload of the message. HTTP representations
607   are defined in <xref target="Part3"/>.
608</t>
609<t>
610   A representation body is only present in a message when a message-body is
611   present, as described in Section 3.3 of <xref target="Part1"/>. The representation body is obtained
612   from the message-body by decoding any Transfer-Encoding that might
613   have been applied to ensure safe and proper transfer of the message.
614</t>
615
616<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
617<t>
618   It is sometimes necessary to determine an identifier for the resource
619   associated with a representation.
620</t>
621<t>
622   An HTTP request representation, when present, is always associated with an
623   anonymous (i.e., unidentified) resource.
624</t>
625<t>
626   In the common case, an HTTP response is a representation of the target
627   resource (see Section 4.3 of <xref target="Part1"/>). However, this is not always the
628   case. To determine the URI of the resource a response is associated with,
629   the following rules are used (with the first applicable one being selected):
630</t>
631<t><list style="numbers">
632   <t>If the response status code is 200 or 203 and the request method was GET,
633   the response payload is a representation of the target resource.</t>
634   <t>If the response status code is 204, 206, or 304 and the request method was GET
635   or HEAD, the response payload is a partial representation of the target
636   resource (see Section 2.8 of <xref target="Part6"/>).</t>
637   <t>If the response has a Content-Location header field, and that URI is the same
638   as the effective request URI, the response payload is a representation of the
639   target resource.</t>
640   <t>If the response has a Content-Location header field, and that URI is not the
641   same as the effective request URI, then the response asserts that its
642   payload is a representation of the resource identified by the
643   Content-Location URI. However, such an assertion cannot be trusted unless
644   it can be verified by other means (not defined by HTTP).</t>
645   <t>Otherwise, the response is a representation of an anonymous (i.e.,
646   unidentified) resource.</t>
647</list></t>
648<t>
649  <cref anchor="TODO-req-uri">
650   The comparison function is going to have to be defined somewhere,
651   because we already need to compare URIs for things like cache invalidation.</cref>
652</t>
653</section>
654
655</section>
656
657
658<section title="Method Definitions" anchor="method.definitions">
659<t>
660   The set of common request methods for HTTP/1.1 is defined below. Although
661   this set can be expanded, additional methods cannot be assumed to
662   share the same semantics for separately extended clients and servers.
663</t>
664
665<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
666
667<section title="Safe Methods" anchor="safe.methods">
668<iref item="Safe Methods" primary="true"/>
669<t>
670   Implementors need to be aware that the software represents the user in
671   their interactions over the Internet, and need to allow
672   the user to be aware of any actions they take which might have an
673   unexpected significance to themselves or others.
674</t>
675<t>
676   In particular, the convention has been established that the GET, HEAD,
677   OPTIONS, and TRACE request methods SHOULD NOT have the significance
678   of taking an action other than retrieval. These request methods ought
679   to be considered "safe".
680   This allows user agents to represent other methods, such as POST, PUT
681   and DELETE, in a special way, so that the user is made aware of the
682   fact that a possibly unsafe action is being requested.
683</t>
684<t>
685   Naturally, it is not possible to ensure that the server does not
686   generate side-effects as a result of performing a GET request; in
687   fact, some dynamic resources consider that a feature. The important
688   distinction here is that the user did not request the side-effects,
689   so therefore cannot be held accountable for them.
690</t>
691</section>
692
693<section title="Idempotent Methods" anchor="idempotent.methods">
694<iref item="Idempotent Methods" primary="true"/>
695<t>
696   Request methods can also have the property of "idempotence" in that,
697   aside from error or expiration issues, the intended effect of multiple
698   identical requests is the same as for a single request.
699   PUT, DELETE, and all safe request methods are idempotent.
700   It is important to note that idempotence refers only to changes
701   requested by the client: a server is free to change its state due
702   to multiple requests for the purpose of tracking those requests,
703   versioning of results, etc.
704</t>
705</section>
706</section>
707
708<section title="OPTIONS" anchor="OPTIONS">
709 
710  <iref primary="true" item="OPTIONS method"/>
711  <iref primary="true" item="Methods" subitem="OPTIONS"/>
712<t>
713   The OPTIONS method requests information about the
714   communication options available on the request/response chain
715   identified by the effective request URI. This method allows a client to
716   determine the options and/or requirements associated with a resource,
717   or the capabilities of a server, without implying a resource action
718   or initiating a resource retrieval.
719</t>
720<t>
721   Responses to the OPTIONS method are not cacheable.
722</t>
723<t>
724   If the OPTIONS request includes a message-body (as indicated by the
725   presence of Content-Length or Transfer-Encoding), then the media type
726   MUST be indicated by a Content-Type field. Although this
727   specification does not define any use for such a body, future
728   extensions to HTTP might use the OPTIONS body to make more detailed
729   queries on the server.
730</t>
731<t>
732   If the request-target is an asterisk ("*"), the OPTIONS request is
733   intended to apply to the server in general rather than to a specific
734   resource. Since a server's communication options typically depend on
735   the resource, the "*" request is only useful as a "ping" or "no-op"
736   type of method; it does nothing beyond allowing the client to test
737   the capabilities of the server. For example, this can be used to test
738   a proxy for HTTP/1.1 compliance (or lack thereof).
739</t>
740<t>
741   If the request-target is not an asterisk, the OPTIONS request applies
742   only to the options that are available when communicating with that
743   resource.
744</t>
745<t>
746   A 200 response SHOULD include any header fields that indicate
747   optional features implemented by the server and applicable to that
748   resource (e.g., Allow), possibly including extensions not defined by
749   this specification. The response body, if any, SHOULD also include
750   information about the communication options. The format for such a
751   body is not defined by this specification, but might be defined by
752   future extensions to HTTP. Content negotiation MAY be used to select
753   the appropriate response format. If no response body is included, the
754   response MUST include a Content-Length field with a field-value of
755   "0".
756</t>
757<t>
758   The Max-Forwards header field MAY be used to target a
759   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
760   If no Max-Forwards field is present in the request, then the forwarded
761   request MUST NOT include a Max-Forwards field.
762</t>
763</section>
764
765<section title="GET" anchor="GET">
766 
767  <iref primary="true" item="GET method"/>
768  <iref primary="true" item="Methods" subitem="GET"/>
769<t>
770   The GET method requests transfer of a current representation of
771   the target resource.
772</t>
773<t>  
774   If the target resource is a data-producing process, it is the
775   produced data which shall be returned as the representation in the response and not
776   the source text of the process, unless that text happens to be the output of
777   the process.
778</t>
779<t>
780   The semantics of the GET method change to a "conditional GET" if the
781   request message includes an If-Modified-Since, If-Unmodified-Since,
782   If-Match, If-None-Match, or If-Range header field. A conditional GET
783   requests that the representation be transferred only under the
784   circumstances described by the conditional header field(s). The
785   conditional GET request is intended to reduce unnecessary network
786   usage by allowing cached representations to be refreshed without requiring
787   multiple requests or transferring data already held by the client.
788</t>
789<t>
790   The semantics of the GET method change to a "partial GET" if the
791   request message includes a Range header field. A partial GET requests
792   that only part of the representation be transferred, as described in Section 5.4 of <xref target="Part5"/>.
793   The partial GET request is intended to reduce unnecessary
794   network usage by allowing partially-retrieved representations to be
795   completed without transferring data already held by the client.
796</t>
797<t>
798   The response to a GET request is cacheable and MAY be used to satisfy
799   subsequent GET and HEAD requests (see <xref target="Part6"/>).
800</t>
801<t>
802   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
803</t>
804</section>
805
806<section title="HEAD" anchor="HEAD">
807 
808  <iref primary="true" item="HEAD method"/>
809  <iref primary="true" item="Methods" subitem="HEAD"/>
810<t>
811   The HEAD method is identical to GET except that the server MUST NOT
812   return a message-body in the response. The metadata contained
813   in the HTTP header fields in response to a HEAD request SHOULD be identical
814   to the information sent in response to a GET request. This method can
815   be used for obtaining metadata about the representation implied by the
816   request without transferring the representation body. This method is
817   often used for testing hypertext links for validity, accessibility,
818   and recent modification.
819</t>
820<t>
821   The response to a HEAD request is cacheable and MAY be used to satisfy
822   a subsequent HEAD request; see <xref target="Part6"/>. It also MAY be used to update a previously cached
823   representation from that resource; if the new field values
824   indicate that the cached representation differs from the current representation (as
825   would be indicated by a change in Content-Length, Content-MD5, ETag
826   or Last-Modified), then the cache MUST treat the cache entry as
827   stale.
828</t>
829</section>
830
831<section title="POST" anchor="POST">
832  <iref primary="true" item="POST method"/>
833  <iref primary="true" item="Methods" subitem="POST"/>
834<t>
835   The POST method requests that the origin server accept the
836   representation enclosed in the request as data to be processed by the
837   target resource. POST is designed to allow a uniform method to cover the
838   following functions:
839  <list style="symbols">
840    <t>
841      Annotation of existing resources;
842    </t>
843    <t>
844        Posting a message to a bulletin board, newsgroup, mailing list,
845        or similar group of articles;
846    </t>
847    <t>
848        Providing a block of data, such as the result of submitting a
849        form, to a data-handling process;
850    </t>
851    <t>
852        Extending a database through an append operation.
853    </t>
854  </list>
855</t>
856<t>
857   The actual function performed by the POST method is determined by the
858   server and is usually dependent on the effective request URI.
859</t>
860<t>
861   The action performed by the POST method might not result in a
862   resource that can be identified by a URI. In this case, either 200
863   (OK) or 204 (No Content) is the appropriate response status code,
864   depending on whether or not the response includes a representation that
865   describes the result.
866</t>
867<t>
868   If a resource has been created on the origin server, the response
869   SHOULD be 201 (Created) and contain a representation which describes the
870   status of the request and refers to the new resource, and a Location
871   header field (see <xref target="header.location"/>).
872</t>
873<t>
874   Responses to POST requests are only cacheable when they
875   include explicit freshness information (see Section 2.3.1 of <xref target="Part6"/>). A
876   cached POST response with a Content-Location header field
877   (see Section 6.7 of <xref target="Part3"/>) whose value is the effective
878   Request URI MAY be used to satisfy subsequent GET and HEAD requests.
879</t>
880<t>
881   Note that POST caching is not widely implemented.
882   However, the 303 (See Other) response can be used to direct the
883   user agent to retrieve a cacheable resource.
884</t>
885</section>
886
887<section title="PUT" anchor="PUT">
888  <iref primary="true" item="PUT method"/>
889  <iref primary="true" item="Methods" subitem="PUT"/>
890<t>
891   The PUT method requests that the state of the target resource
892   be created or replaced with the state defined by the representation
893   enclosed in the request message payload.  A successful PUT of a given
894   representation would suggest that a subsequent GET on that same target
895   resource will result in an equivalent representation being returned in
896   a 200 (OK) response.  However, there is no guarantee that such a state
897   change will be observable, since the target resource might be acted
898   upon by other user agents in parallel, or might be subject to dynamic
899   processing by the origin server, before any subsequent GET is received.
900   A successful response only implies that the user agent's intent was
901   achieved at the time of its processing by the origin server.
902</t>
903<t>  
904   If the target resource does not have a current representation and
905   the PUT successfully creates one, then the origin server MUST inform
906   the user agent by sending a 201 (Created) response.  If the target
907   resource does have a current representation and that representation is
908   successfully modified in accordance with the state of the enclosed
909   representation, then either a 200 (OK) or 204 (No Content) response
910   SHOULD be sent to indicate successful completion of the request.
911</t>
912<t>
913   Unrecognized header fields SHOULD be ignored (i.e., not saved
914   as part of the resource state).
915</t>
916<t>
917   An origin server SHOULD verify that the PUT representation is
918   consistent with any constraints which the server has for the target
919   resource that cannot or will not be changed by the PUT.  This is
920   particularly important when the origin server uses internal
921   configuration information related to the URI in order to set the
922   values for representation metadata on GET responses.  When a PUT
923   representation is inconsistent with the target resource, the origin
924   server SHOULD either make them consistent, by transforming the
925   representation or changing the resource configuration, or respond
926   with an appropriate error message containing sufficient information
927   to explain why the representation is unsuitable.  The 409 (Conflict)
928   or 415 (Unsupported Media Type) status codes are suggested, with the
929   latter being specific to constraints on Content-Type values.
930</t>
931<t>
932   For example, if the target resource is configured to always have a
933   Content-Type of "text/html" and the representation being PUT has a
934   Content-Type of "image/jpeg", then the origin server SHOULD do one of:
935   (a) reconfigure the target resource to reflect the new media type;
936   (b) transform the PUT representation to a format consistent with that
937   of the resource before saving it as the new resource state; or,
938   (c) reject the request with a 415 response indicating that the target
939   resource is limited to "text/html", perhaps including a link to a
940   different resource that would be a suitable target for the new
941   representation.
942</t>
943<t>
944   HTTP does not define exactly how a PUT method affects the state
945   of an origin server beyond what can be expressed by the intent of
946   the user agent request and the semantics of the origin server response.
947   It does not define what a resource might be, in any sense of that
948   word, beyond the interface provided via HTTP.  It does not define
949   how resource state is "stored", nor how such storage might change
950   as a result of a change in resource state, nor how the origin server
951   translates resource state into representations.  Generally speaking,
952   all implementation details behind the resource interface are
953   intentionally hidden by the server.
954</t>
955<t>
956   The fundamental difference between the POST and PUT methods is
957   highlighted by the different intent for the target resource.
958   The target resource in a POST request is intended to handle the
959   enclosed representation as a data-accepting process, such as for
960   a gateway to some other protocol or a document that accepts annotations.
961   In contrast, the target resource in a PUT request is intended to
962   take the enclosed representation as a new or replacement value.
963   Hence, the intent of PUT is idempotent and visible to intermediaries,
964   even though the exact effect is only known by the origin server.
965</t>
966<t>
967   Proper interpretation of a PUT request presumes that the user agent
968   knows what target resource is desired.  A service that is intended
969   to select a proper URI on behalf of the client, after receiving
970   a state-changing request, SHOULD be implemented using the POST
971   method rather than PUT.  If the origin server will not make the
972   requested PUT state change to the target resource and instead
973   wishes to have it applied to a different resource, such as when the
974   resource has been moved to a different URI, then the origin server
975   MUST send a 301 (Moved Permanently) response; the user agent MAY
976   then make its own decision regarding whether or not to redirect the
977   request.
978</t>
979<t>
980   A PUT request applied to the target resource MAY have side-effects
981   on other resources.  For example, an article might have a URI for
982   identifying "the current version" (a resource) which is separate
983   from the URIs identifying each particular version (different
984   resources that at one point shared the same state as the current version
985   resource).  A successful PUT request on "the current version" URI might
986   therefore create a new version resource in addition to changing the
987   state of the target resource, and might also cause links to be added
988   between the related resources.
989</t>
990<t>
991   An origin server SHOULD reject any PUT request that contains a
992   Content-Range header field, since it might be misinterpreted as
993   partial content (or might be partial content that is being mistakenly
994   PUT as a full representation).  Partial content updates are
995   possible by targeting a separately identified resource with state
996   that overlaps a portion of the larger resource, or by using a
997   different method that has been specifically defined for partial
998   updates (for example, the PATCH method defined in
999   <xref target="RFC5789"/>).
1000</t>
1001<t>
1002   Responses to the PUT method are not cacheable. If a PUT request passes
1003   through a cache that has one or more stored responses for the effective
1004   request URI, those stored responses will be invalidated (see
1005   Section 2.5 of <xref target="Part6"/>).
1006</t>
1007</section>
1008
1009<section title="DELETE" anchor="DELETE">
1010  <iref primary="true" item="DELETE method"/>
1011  <iref primary="true" item="Methods" subitem="DELETE"/>
1012<t>
1013   The DELETE method requests that the origin server delete the target
1014   resource. This method MAY be overridden by
1015   human intervention (or other means) on the origin server. The client cannot
1016   be guaranteed that the operation has been carried out, even if the
1017   status code returned from the origin server indicates that the action
1018   has been completed successfully. However, the server SHOULD NOT
1019   indicate success unless, at the time the response is given, it
1020   intends to delete the resource or move it to an inaccessible
1021   location.
1022</t>
1023<t>
1024   A successful response SHOULD be 200 (OK) if the response includes an
1025   representation describing the status, 202 (Accepted) if the action has not
1026   yet been enacted, or 204 (No Content) if the action has been enacted
1027   but the response does not include a representation.
1028</t>
1029<t>
1030   Responses to the DELETE method are not cacheable. If a DELETE request
1031   passes through a cache that has one or more stored responses for the
1032   effective request URI, those stored responses will be invalidated (see
1033   Section 2.5 of <xref target="Part6"/>).
1034</t>
1035</section>
1036
1037<section title="TRACE" anchor="TRACE">
1038 
1039  <iref primary="true" item="TRACE method"/>
1040  <iref primary="true" item="Methods" subitem="TRACE"/>
1041<t>
1042   The TRACE method requests a remote, application-layer loop-back
1043   of the request message. The final recipient of the request
1044   SHOULD reflect the message received back to the client as the
1045   message-body of a 200 (OK) response. The final recipient is either the
1046   origin server or the first proxy to receive a Max-Forwards
1047   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1048   A TRACE request MUST NOT include a message-body.
1049</t>
1050<t>
1051   TRACE allows the client to see what is being received at the other
1052   end of the request chain and use that data for testing or diagnostic
1053   information. The value of the Via header field (Section 9.9 of <xref target="Part1"/>) is of
1054   particular interest, since it acts as a trace of the request chain.
1055   Use of the Max-Forwards header field allows the client to limit the
1056   length of the request chain, which is useful for testing a chain of
1057   proxies forwarding messages in an infinite loop.
1058</t>
1059<t>
1060   If the request is valid, the response SHOULD have a Content-Type of
1061   "message/http" (see Section 10.3.1 of <xref target="Part1"/>) and contain a message-body
1062   that encloses a copy of the entire request message.
1063   Responses to the TRACE method are not cacheable.
1064</t>
1065</section>
1066
1067<section title="CONNECT" anchor="CONNECT">
1068  <iref primary="true" item="CONNECT method"/>
1069  <iref primary="true" item="Methods" subitem="CONNECT"/>
1070<t>
1071   The CONNECT method requests that the proxy establish a tunnel
1072   to the request-target and then restrict its behavior to blind
1073   forwarding of packets until the connection is closed.
1074</t>
1075<t>
1076   When using CONNECT, the request-target MUST use the authority form
1077   (Section 4.1.2 of <xref target="Part1"/>); i.e., the request-target consists of only the
1078   host name and port number of the tunnel destination, separated by a colon.
1079   For example,
1080</t>
1081<figure><artwork type="message/http; msgtype=&#34;request&#34;"><![CDATA[
1082  CONNECT server.example.com:80 HTTP/1.1
1083  Host: server.example.com:80
1084 
1085  ]]></artwork></figure>
1086<t>
1087   Other HTTP mechanisms can be used normally with the CONNECT method —
1088   except end-to-end protocol Upgrade requests, since the
1089   tunnel must be established first.
1090</t>
1091<t>
1092   For example, proxy authentication might be used to establish the
1093   authority to create a tunnel:
1094</t>
1095<figure><artwork type="message/http; msgtype=&#34;request&#34;"><![CDATA[
1096  CONNECT server.example.com:80 HTTP/1.1
1097  Host: server.example.com:80
1098  Proxy-Authorization: basic aGVsbG86d29ybGQ=
1099 
1100  ]]></artwork></figure>
1101<t>
1102   Like any other pipelined HTTP/1.1 request, data to be tunnel may be
1103   sent immediately after the blank line. The usual caveats also apply:
1104   data may be discarded if the eventual response is negative, and the
1105   connection may be reset with no response if more than one TCP segment
1106   is outstanding.
1107</t>
1108
1109<section title="Establishing a Tunnel with CONNECT">
1110<t>
1111   Any successful (2xx) response to a CONNECT request indicates that the
1112   proxy has established a connection to the requested host and port,
1113   and has switched to tunneling the current connection to that server
1114   connection.
1115</t>
1116<t>
1117   It may be the case that the proxy itself can only reach the requested
1118   origin server through another proxy.  In this case, the first proxy
1119   SHOULD make a CONNECT request of that next proxy, requesting a tunnel
1120   to the authority.  A proxy MUST NOT respond with any 2xx status code
1121   unless it has either a direct or tunnel connection established to the
1122   authority.
1123</t>
1124<t>
1125   An origin server which receives a CONNECT request for itself MAY
1126   respond with a 2xx status code to indicate that a connection is
1127   established.
1128</t>
1129<t>
1130   If at any point either one of the peers gets disconnected, any
1131   outstanding data that came from that peer will be passed to the other
1132   one, and after that also the other connection will be terminated by
1133   the proxy. If there is outstanding data to that peer undelivered,
1134   that data will be discarded.
1135</t>
1136
1137</section>
1138</section>
1139</section>
1140
1141
1142<section title="Status Code Definitions" anchor="status.codes">
1143<t>
1144   Each Status-Code is described below, including any metadata required
1145   in the response.
1146</t>
1147
1148<section title="Informational 1xx" anchor="status.1xx">
1149<t>
1150   This class of status code indicates a provisional response,
1151   consisting only of the Status-Line and optional header fields, and is
1152   terminated by an empty line. There are no required header fields for this
1153   class of status code. Since HTTP/1.0 did not define any 1xx status
1154   codes, servers MUST NOT send a 1xx response to an HTTP/1.0 client
1155   except under experimental conditions.
1156</t>
1157<t>
1158   A client MUST be prepared to accept one or more 1xx status responses
1159   prior to a regular response, even if the client does not expect a 100
1160   (Continue) status message. Unexpected 1xx status responses MAY be
1161   ignored by a user agent.
1162</t>
1163<t>
1164   Proxies MUST forward 1xx responses, unless the connection between the
1165   proxy and its client has been closed, or unless the proxy itself
1166   requested the generation of the 1xx response. (For example, if a
1167   proxy adds a "Expect: 100-continue" field when it forwards a request,
1168   then it need not forward the corresponding 100 (Continue)
1169   response(s).)
1170</t>
1171
1172<section title="100 Continue" anchor="status.100">
1173  <iref primary="true" item="100 Continue (status code)"/>
1174  <iref primary="true" item="Status Codes" subitem="100 Continue"/>
1175<t>
1176   The client SHOULD continue with its request. This interim response is
1177   used to inform the client that the initial part of the request has
1178   been received and has not yet been rejected by the server. The client
1179   SHOULD continue by sending the remainder of the request or, if the
1180   request has already been completed, ignore this response. The server
1181   MUST send a final response after the request has been completed. See
1182   Section 7.2.3 of <xref target="Part1"/> for detailed discussion of the use and handling of this
1183   status code.
1184</t>
1185</section>
1186
1187<section title="101 Switching Protocols" anchor="status.101">
1188  <iref primary="true" item="101 Switching Protocols (status code)"/>
1189  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols"/>
1190<t>
1191   The server understands and is willing to comply with the client's
1192   request, via the Upgrade message header field (Section 9.8 of <xref target="Part1"/>), for a
1193   change in the application protocol being used on this connection. The
1194   server will switch protocols to those defined by the response's
1195   Upgrade header field immediately after the empty line which
1196   terminates the 101 response.
1197</t>
1198<t>
1199   The protocol SHOULD be switched only when it is advantageous to do
1200   so. For example, switching to a newer version of HTTP is advantageous
1201   over older versions, and switching to a real-time, synchronous
1202   protocol might be advantageous when delivering resources that use
1203   such features.
1204</t>
1205</section>
1206</section>
1207
1208<section title="Successful 2xx" anchor="status.2xx">
1209<t>
1210   This class of status code indicates that the client's request was
1211   successfully received, understood, and accepted.
1212</t>
1213
1214<section title="200 OK" anchor="status.200">
1215  <iref primary="true" item="200 OK (status code)"/>
1216  <iref primary="true" item="Status Codes" subitem="200 OK"/>
1217<t>
1218   The request has succeeded. The payload returned with the response
1219   is dependent on the method used in the request, for example:
1220  <list style="hanging">
1221    <t hangText="GET">
1222          a representation of the target resource is sent in the response;
1223    </t>
1224    <t hangText="HEAD">
1225          the same representation as GET, except without the message-body;
1226    </t>
1227    <t hangText="POST">
1228      a representation describing or containing the result of the action;
1229    </t>
1230    <t hangText="TRACE">
1231      a representation containing the request message as received by the
1232      end server.
1233    </t>
1234  </list>
1235</t>
1236<t>
1237   Caches MAY use a heuristic (see Section 2.3.1.1 of <xref target="Part6"/>) to determine
1238   freshness for 200 responses.
1239</t>
1240</section>
1241
1242<section title="201 Created" anchor="status.201">
1243  <iref primary="true" item="201 Created (status code)"/>
1244  <iref primary="true" item="Status Codes" subitem="201 Created"/>
1245<t>
1246   The request has been fulfilled and has resulted in a new resource being
1247   created. The newly created resource can be referenced by the URI(s)
1248   returned in the payload of the response, with the most specific URI
1249   for the resource given by a Location header field. The response
1250   SHOULD include a payload containing a list of resource
1251   characteristics and location(s) from which the user or user agent can
1252   choose the one most appropriate. The payload format is specified by
1253   the media type given in the Content-Type header field. The origin
1254   server MUST create the resource before returning the 201 status code.
1255   If the action cannot be carried out immediately, the server SHOULD
1256   respond with 202 (Accepted) response instead.
1257</t>
1258<t>
1259   A 201 response MAY contain an ETag response header field indicating
1260   the current value of the entity-tag for the representation of the resource
1261   just created (see Section 6.1 of <xref target="Part4"/>).
1262</t>
1263</section>
1264
1265<section title="202 Accepted" anchor="status.202">
1266  <iref primary="true" item="202 Accepted (status code)"/>
1267  <iref primary="true" item="Status Codes" subitem="202 Accepted"/>
1268<t>
1269   The request has been accepted for processing, but the processing has
1270   not been completed.  The request might or might not eventually be
1271   acted upon, as it might be disallowed when processing actually takes
1272   place. There is no facility for re-sending a status code from an
1273   asynchronous operation such as this.
1274</t>
1275<t>
1276   The 202 response is intentionally non-committal. Its purpose is to
1277   allow a server to accept a request for some other process (perhaps a
1278   batch-oriented process that is only run once per day) without
1279   requiring that the user agent's connection to the server persist
1280   until the process is completed. The representation returned with this
1281   response SHOULD include an indication of the request's current status
1282   and either a pointer to a status monitor or some estimate of when the
1283   user can expect the request to be fulfilled.
1284</t>
1285</section>
1286
1287<section title="203 Non-Authoritative Information" anchor="status.203">
1288  <iref primary="true" item="203 Non-Authoritative Information (status code)"/>
1289  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information"/>
1290<t>
1291   The returned metadata in the header fields is not the
1292   definitive set as available from the origin server, but is gathered
1293   from a local or a third-party copy. The set presented MAY be a subset
1294   or superset of the original version. For example, including local
1295   annotation information about the resource might result in a superset
1296   of the metadata known by the origin server. Use of this
1297   response code is not required and is only appropriate when the
1298   response would otherwise be 200 (OK).
1299</t>
1300<t>
1301   Caches MAY use a heuristic (see Section 2.3.1.1 of <xref target="Part6"/>) to determine
1302   freshness for 203 responses.
1303</t>
1304
1305</section>
1306
1307<section title="204 No Content" anchor="status.204">
1308  <iref primary="true" item="204 No Content (status code)"/>
1309  <iref primary="true" item="Status Codes" subitem="204 No Content"/>
1310<t>
1311   The server has successfully fulfilled the request, but there is no
1312   additional content to return in the response payload body.  The
1313   resource metadata and representation metadata in the response message's
1314   header fields refer to the target resource
1315   and its current representation, respectively, after the requested action.
1316   For example, if a 204 status code is received in response to a PUT
1317   and the response contains an ETag header field, then the value of
1318   that field is the current entity-tag for the representation that
1319   was successfully PUT.
1320</t>
1321<t>
1322   If the client is a user agent, it SHOULD NOT change its document view
1323   from that which caused the request to be sent. This response is
1324   primarily intended to allow input for actions to take place without
1325   causing a change to the user agent's active document view, although
1326   any new or updated metadata SHOULD be applied to the document
1327   currently in the user agent's active view.
1328</t>
1329<t>
1330   The 204 response MUST NOT include a message-body, and thus is always
1331   terminated by the first empty line after the header fields.
1332</t>
1333</section>
1334
1335<section title="205 Reset Content" anchor="status.205">
1336  <iref primary="true" item="205 Reset Content (status code)"/>
1337  <iref primary="true" item="Status Codes" subitem="205 Reset Content"/>
1338<t>
1339   The server has fulfilled the request and the user agent SHOULD reset
1340   the document view which caused the request to be sent. This response
1341   is primarily intended to allow input for actions to take place via
1342   user input, followed by a clearing of the form in which the input is
1343   given so that the user can easily initiate another input action.
1344</t>
1345<t>  
1346   The message-body included with the response MUST be empty. Note that
1347   receivers still need to parse the response according to the algorithm defined
1348   in Section 3.3 of <xref target="Part1"/>.
1349</t>
1350</section>
1351
1352<section title="206 Partial Content" anchor="status.206">
1353  <iref primary="true" item="206 Partial Content (status code)"/>
1354  <iref primary="true" item="Status Codes" subitem="206 Partial Content"/>
1355 
1356<t>
1357   The server has fulfilled the partial GET request for the resource
1358   and the enclosed payload is a partial representation as defined in Section 3.1 of <xref target="Part5"/>.
1359</t>
1360<t>
1361   Caches MAY use a heuristic (see Section 2.3.1.1 of <xref target="Part6"/>) to determine
1362   freshness for 206 responses.
1363</t>
1364</section>
1365</section>
1366
1367<section title="Redirection 3xx" anchor="status.3xx">
1368<t>
1369   This class of status code indicates that further action needs to be
1370   taken by the user agent in order to fulfill the request.  The action
1371   required MAY be carried out by the user agent without interaction
1372   with the user if and only if the method used in the second request is
1373   known to be "safe", as defined in <xref target="safe.methods"/>.
1374   A client SHOULD detect infinite redirection loops, since such loops
1375   generate network traffic for each redirection.
1376</t>
1377<t><list>
1378  <t>
1379    Note: An earlier version of this specification recommended a
1380    maximum of five redirections (<xref target="RFC2068"/>, Section 10.3).
1381    Content developers need to be aware that some clients might
1382    implement such a fixed limitation.
1383  </t>
1384</list></t>
1385
1386<section title="300 Multiple Choices" anchor="status.300">
1387  <iref primary="true" item="300 Multiple Choices (status code)"/>
1388  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices"/>
1389<t>
1390   The target resource has more than one
1391   representation, each with its own specific location, and agent-driven
1392   negotiation information (Section 5 of <xref target="Part3"/>) is being provided so that
1393   the user (or user agent) can select a preferred representation by
1394   redirecting its request to that location.
1395</t>
1396<t>
1397   Unless it was a HEAD request, the response SHOULD include a representation
1398   containing a list of representation metadata and location(s) from
1399   which the user or user agent can choose the one most appropriate. The
1400   data format is specified by the media type given in the Content-Type
1401   header field. Depending upon the format and the capabilities of
1402   the user agent, selection of the most appropriate choice MAY be
1403   performed automatically. However, this specification does not define
1404   any standard for such automatic selection.
1405</t>
1406<t>
1407   If the server has a preferred choice of representation, it SHOULD
1408   include the specific URI for that representation in the Location
1409   field; user agents MAY use the Location field value for automatic
1410   redirection.
1411</t>
1412<t>
1413   Caches MAY use a heuristic (see Section 2.3.1.1 of <xref target="Part6"/>) to determine
1414   freshness for 300 responses.
1415</t>
1416
1417</section>
1418
1419<section title="301 Moved Permanently" anchor="status.301">
1420  <iref primary="true" item="301 Moved Permanently (status code)"/>
1421  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently"/>
1422<t>
1423   The target resource has been assigned a new permanent URI and any
1424   future references to this resource SHOULD use one of the returned
1425   URIs.  Clients with link editing capabilities ought to automatically
1426   re-link references to the effective request URI to one or more of the new
1427   references returned by the server, where possible.
1428</t>
1429<t>
1430   Caches MAY use a heuristic (see Section 2.3.1.1 of <xref target="Part6"/>) to determine
1431   freshness for 301 responses.
1432</t>
1433<t>
1434   The new permanent URI SHOULD be given by the Location field in the
1435   response. Unless the request method was HEAD, the representation of the
1436   response SHOULD contain a short hypertext note with a hyperlink to
1437   the new URI(s).
1438</t>
1439<t>
1440   If the 301 status code is received in response to a request method
1441   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1442   then the request MAY be automatically redirected by the user agent without
1443   confirmation.  Otherwise, the user agent MUST NOT automatically redirect the
1444   request unless it can be confirmed by the user, since this might
1445   change the conditions under which the request was issued.
1446</t>
1447<t><list>
1448  <t>
1449    Note: When automatically redirecting a POST request after
1450    receiving a 301 status code, some existing HTTP/1.0 user agents
1451    will erroneously change it into a GET request.
1452  </t>
1453</list></t>
1454</section>
1455
1456<section title="302 Found" anchor="status.302">
1457  <iref primary="true" item="302 Found (status code)"/>
1458  <iref primary="true" item="Status Codes" subitem="302 Found"/>
1459<t>
1460   The target resource resides temporarily under a different URI.
1461   Since the redirection might be altered on occasion, the client SHOULD
1462   continue to use the effective request URI for future requests.
1463</t>
1464<t>
1465   The temporary URI SHOULD be given by the Location field in the
1466   response. Unless the request method was HEAD, the representation of the
1467   response SHOULD contain a short hypertext note with a hyperlink to
1468   the new URI(s).
1469</t>
1470<t>
1471   If the 302 status code is received in response to a request method
1472   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1473   then the request MAY be automatically redirected by the user agent without
1474   confirmation.  Otherwise, the user agent MUST NOT automatically redirect the
1475   request unless it can be confirmed by the user, since this might
1476   change the conditions under which the request was issued.
1477</t>
1478<t><list>
1479  <t>
1480    Note: HTTP/1.0 (<xref target="RFC1945"/>, Section 9.3)
1481    and the first version of HTTP/1.1 (<xref target="RFC2068"/>, Section 10.3.3)
1482    specify that the client is not allowed to change the method on the
1483    redirected request.  However, most existing user agent implementations
1484    treat 302 as if it were a 303 response, performing a GET on the Location
1485    field-value regardless of the original request method. Therefore, a
1486    previous version of this specification
1487    (<xref target="RFC2616"/>, Section 10.3.3) has added the
1488    status codes
1489    <xref target="status.303" format="none">303</xref> and
1490    <xref target="status.307" format="none">307</xref> for servers that wish
1491    to make unambiguously clear which kind of reaction is expected of the
1492    client.
1493  </t>
1494</list></t>
1495</section>
1496
1497<section title="303 See Other" anchor="status.303">
1498  <iref primary="true" item="303 See Other (status code)"/>
1499  <iref primary="true" item="Status Codes" subitem="303 See Other"/>
1500<t>
1501   The server directs the user agent to a different resource, indicated
1502   by a URI in the Location header field, that provides an indirect
1503   response to the original request.  The user agent MAY perform a GET
1504   request on the URI in the Location field in order to obtain a
1505   representation corresponding to the response, be redirected again,
1506   or end with an error status.  The Location URI is not a substitute
1507   reference for the effective request URI.
1508</t>
1509<t>
1510   The 303 status code is generally applicable to any HTTP method.  It is
1511   primarily used to allow the output of a POST action to redirect
1512   the user agent to a selected resource, since doing so provides the
1513   information corresponding to the POST response in a form that
1514   can be separately identified, bookmarked, and cached independent
1515   of the original request.
1516</t>
1517<t>
1518   A 303 response to a GET request indicates that the requested
1519   resource does not have a representation of its own that can be
1520   transferred by the server over HTTP.  The Location URI indicates a
1521   resource that is descriptive of the target resource, such that the
1522   follow-on representation might be useful to recipients without
1523   implying that it adequately represents the target resource.
1524   Note that answers to the questions of what can be represented, what
1525   representations are adequate, and what might be a useful description
1526   are outside the scope of HTTP and thus entirely determined by the
1527   URI owner(s).
1528</t>
1529<t>
1530   Except for responses to a HEAD request, the representation of a 303
1531   response SHOULD contain a short hypertext note with a hyperlink
1532   to the Location URI.
1533</t>
1534</section>
1535
1536<section title="304 Not Modified" anchor="status.304">
1537  <iref primary="true" item="304 Not Modified (status code)"/>
1538  <iref primary="true" item="Status Codes" subitem="304 Not Modified"/>
1539 
1540<t>
1541   The response to the request has not been modified since the conditions
1542   indicated by the client's conditional GET request, as defined in Section 3.1 of <xref target="Part4"/>.
1543</t>
1544</section>
1545
1546<section title="305 Use Proxy" anchor="status.305">
1547  <iref primary="true" item="305 Use Proxy (status code)"/>
1548  <iref primary="true" item="Status Codes" subitem="305 Use Proxy"/>
1549<t>
1550   The 305 status code was defined in a previous version of this specification
1551   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1552</t>
1553</section>
1554
1555<section title="306 (Unused)" anchor="status.306">
1556  <iref primary="true" item="306 (Unused) (status code)"/>
1557  <iref primary="true" item="Status Codes" subitem="306 (Unused)"/>
1558<t>
1559   The 306 status code was used in a previous version of the
1560   specification, is no longer used, and the code is reserved.
1561</t>
1562</section>
1563
1564<section title="307 Temporary Redirect" anchor="status.307">
1565  <iref primary="true" item="307 Temporary Redirect (status code)"/>
1566  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect"/>
1567<t>
1568   The target resource resides temporarily under a different URI.
1569   Since the redirection can change over time, the client SHOULD
1570   continue to use the effective request URI for future requests.
1571</t>
1572<t>
1573   The temporary URI SHOULD be given by the Location field in the
1574   response. Unless the request method was HEAD, the representation of the
1575   response SHOULD contain a short hypertext note with a hyperlink to
1576   the new URI(s), since many pre-HTTP/1.1 user agents do not
1577   understand the 307 status code. Therefore, the note SHOULD contain the
1578   information necessary for a user to repeat the original request on
1579   the new URI.
1580</t>
1581<t>
1582   If the 307 status code is received in response to a request method
1583   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1584   then the request MAY be automatically redirected by the user agent without
1585   confirmation.  Otherwise, the user agent MUST NOT automatically redirect the
1586   request unless it can be confirmed by the user, since this might
1587   change the conditions under which the request was issued.
1588</t>
1589</section>
1590</section>
1591
1592<section title="Client Error 4xx" anchor="status.4xx">
1593<t>
1594   The 4xx class of status code is intended for cases in which the
1595   client seems to have erred. Except when responding to a HEAD request,
1596   the server SHOULD include a representation containing an explanation of the
1597   error situation, and whether it is a temporary or permanent
1598   condition. These status codes are applicable to any request method.
1599   User agents SHOULD display any included representation to the user.
1600</t>
1601<t>
1602   If the client is sending data, a server implementation using TCP
1603   SHOULD be careful to ensure that the client acknowledges receipt of
1604   the packet(s) containing the response, before the server closes the
1605   input connection. If the client continues sending data to the server
1606   after the close, the server's TCP stack will send a reset packet to
1607   the client, which might erase the client's unacknowledged input buffers
1608   before they can be read and interpreted by the HTTP application.
1609</t>
1610
1611<section title="400 Bad Request" anchor="status.400">
1612  <iref primary="true" item="400 Bad Request (status code)"/>
1613  <iref primary="true" item="Status Codes" subitem="400 Bad Request"/>
1614<t>
1615   The request could not be understood by the server due to malformed
1616   syntax. The client SHOULD NOT repeat the request without
1617   modifications.
1618</t>
1619</section>
1620
1621<section title="401 Unauthorized" anchor="status.401">
1622  <iref primary="true" item="401 Unauthorized (status code)"/>
1623  <iref primary="true" item="Status Codes" subitem="401 Unauthorized"/>
1624 
1625<t>
1626   The request requires user authentication (see Section 3.1 of <xref target="Part7"/>).
1627</t>
1628</section>
1629
1630<section title="402 Payment Required" anchor="status.402">
1631  <iref primary="true" item="402 Payment Required (status code)"/>
1632  <iref primary="true" item="Status Codes" subitem="402 Payment Required"/>
1633<t>
1634   This code is reserved for future use.
1635</t>
1636</section>
1637
1638<section title="403 Forbidden" anchor="status.403">
1639  <iref primary="true" item="403 Forbidden (status code)"/>
1640  <iref primary="true" item="Status Codes" subitem="403 Forbidden"/>
1641<t>
1642   The server understood the request, but is refusing to fulfill it.
1643   Authorization will not help and the request SHOULD NOT  be repeated.
1644   If the request method was not HEAD and the server wishes to make
1645   public why the request has not been fulfilled, it SHOULD describe the
1646   reason for the refusal in the representation.  If the server does not wish to
1647   make this information available to the client, the status code 404
1648   (Not Found) can be used instead.
1649</t>
1650</section>
1651
1652<section title="404 Not Found" anchor="status.404">
1653  <iref primary="true" item="404 Not Found (status code)"/>
1654  <iref primary="true" item="Status Codes" subitem="404 Not Found"/>
1655<t>
1656   The server has not found anything matching the effective request URI. No
1657   indication is given of whether the condition is temporary or
1658   permanent. The 410 (Gone) status code SHOULD be used if the server
1659   knows, through some internally configurable mechanism, that an old
1660   resource is permanently unavailable and has no forwarding address.
1661   This status code is commonly used when the server does not wish to
1662   reveal exactly why the request has been refused, or when no other
1663   response is applicable.
1664</t>
1665</section>
1666
1667<section title="405 Method Not Allowed" anchor="status.405">
1668  <iref primary="true" item="405 Method Not Allowed (status code)"/>
1669  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed"/>
1670<t>
1671   The method specified in the Request-Line is not allowed for the target
1672   resource. The response MUST include an
1673   Allow header field containing a list of valid methods for the requested
1674   resource.
1675</t>
1676</section>
1677
1678<section title="406 Not Acceptable" anchor="status.406">
1679  <iref primary="true" item="406 Not Acceptable (status code)"/>
1680  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable"/>
1681<t>
1682   The resource identified by the request is only capable of generating
1683   response representations which have content characteristics not acceptable
1684   according to the accept header fields sent in the request.
1685</t>
1686<t>
1687   Unless it was a HEAD request, the response SHOULD include a representation
1688   containing a list of available representation characteristics and location(s)
1689   from which the user or user agent can choose the one most
1690   appropriate. The data format is specified by the media type given
1691   in the Content-Type header field. Depending upon the format and the
1692   capabilities of the user agent, selection of the most appropriate
1693   choice MAY be performed automatically. However, this specification
1694   does not define any standard for such automatic selection.
1695</t>
1696<t><list>
1697  <t>
1698    Note: HTTP/1.1 servers are allowed to return responses which are
1699    not acceptable according to the accept header fields sent in the
1700    request. In some cases, this might even be preferable to sending a
1701    406 response. User agents are encouraged to inspect the header fields of
1702    an incoming response to determine if it is acceptable.
1703  </t>
1704</list></t>
1705<t>
1706   If the response could be unacceptable, a user agent SHOULD
1707   temporarily stop receipt of more data and query the user for a
1708   decision on further actions.
1709</t>
1710</section>
1711
1712<section title="407 Proxy Authentication Required" anchor="status.407">
1713  <iref primary="true" item="407 Proxy Authentication Required (status code)"/>
1714  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required"/>
1715<t>
1716   This code is similar to 401 (Unauthorized), but indicates that the
1717   client must first authenticate itself with the proxy (see Section 3.2 of <xref target="Part7"/>).
1718</t>
1719</section>
1720
1721<section title="408 Request Timeout" anchor="status.408">
1722  <iref primary="true" item="408 Request Timeout (status code)"/>
1723  <iref primary="true" item="Status Codes" subitem="408 Request Timeout"/>
1724<t>
1725   The client did not produce a request within the time that the server
1726   was prepared to wait. The client MAY repeat the request without
1727   modifications at any later time.
1728</t>
1729</section>
1730
1731<section title="409 Conflict" anchor="status.409">
1732  <iref primary="true" item="409 Conflict (status code)"/>
1733  <iref primary="true" item="Status Codes" subitem="409 Conflict"/>
1734<t>
1735   The request could not be completed due to a conflict with the current
1736   state of the resource. This code is only allowed in situations where
1737   it is expected that the user might be able to resolve the conflict
1738   and resubmit the request. The response body SHOULD include enough
1739   information for the user to recognize the source of the conflict.
1740   Ideally, the response representation would include enough information for the
1741   user or user agent to fix the problem; however, that might not be
1742   possible and is not required.
1743</t>
1744<t>
1745   Conflicts are most likely to occur in response to a PUT request. For
1746   example, if versioning were being used and the representation being PUT
1747   included changes to a resource which conflict with those made by an
1748   earlier (third-party) request, the server might use the 409 response
1749   to indicate that it can't complete the request. In this case, the
1750   response representation would likely contain a list of the differences
1751   between the two versions in a format defined by the response
1752   Content-Type.
1753</t>
1754</section>
1755
1756<section title="410 Gone" anchor="status.410">
1757  <iref primary="true" item="410 Gone (status code)"/>
1758  <iref primary="true" item="Status Codes" subitem="410 Gone"/>
1759<t>
1760   The target resource is no longer available at the server and no
1761   forwarding address is known. This condition is expected to be
1762   considered permanent. Clients with link editing capabilities SHOULD
1763   delete references to the effective request URI after user approval. If the
1764   server does not know, or has no facility to determine, whether or not
1765   the condition is permanent, the status code 404 (Not Found) SHOULD be
1766   used instead.
1767</t>
1768<t>
1769   The 410 response is primarily intended to assist the task of web
1770   maintenance by notifying the recipient that the resource is
1771   intentionally unavailable and that the server owners desire that
1772   remote links to that resource be removed. Such an event is common for
1773   limited-time, promotional services and for resources belonging to
1774   individuals no longer working at the server's site. It is not
1775   necessary to mark all permanently unavailable resources as "gone" or
1776   to keep the mark for any length of time — that is left to the
1777   discretion of the server owner.
1778</t>
1779<t>
1780   Caches MAY use a heuristic (see Section 2.3.1.1 of <xref target="Part6"/>) to determine freshness
1781   for 410 responses.
1782</t>
1783
1784</section>
1785
1786<section title="411 Length Required" anchor="status.411">
1787  <iref primary="true" item="411 Length Required (status code)"/>
1788  <iref primary="true" item="Status Codes" subitem="411 Length Required"/>
1789<t>
1790   The server refuses to accept the request without a defined Content-Length.
1791   The client MAY repeat the request if it adds a valid
1792   Content-Length header field containing the length of the message-body
1793   in the request message.
1794</t>
1795</section>
1796
1797<section title="412 Precondition Failed" anchor="status.412">
1798  <iref primary="true" item="412 Precondition Failed (status code)"/>
1799  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed"/>
1800 
1801<t>
1802   The precondition given in one or more of the header fields
1803   evaluated to false when it was tested on the server, as defined in
1804   Section 3.2 of <xref target="Part4"/>.
1805</t>
1806</section>
1807
1808<section title="413 Request Entity Too Large" anchor="status.413">
1809  <iref primary="true" item="413 Request Entity Too Large (status code)"/>
1810  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large"/>
1811<t>
1812   The server is refusing to process a request because the request
1813   representation is larger than the server is willing or able to process. The
1814   server MAY close the connection to prevent the client from continuing
1815   the request.
1816</t>
1817<t>
1818   If the condition is temporary, the server SHOULD include a Retry-After
1819   header field to indicate that it is temporary and after what
1820   time the client MAY try again.
1821</t>
1822</section>
1823
1824<section title="414 URI Too Long" anchor="status.414">
1825  <iref primary="true" item="414 URI Too Long (status code)"/>
1826  <iref primary="true" item="Status Codes" subitem="414 URI Too Long"/>
1827<t>
1828   The server is refusing to service the request because the effective request URI
1829   is longer than the server is willing to interpret. This rare
1830   condition is only likely to occur when a client has improperly
1831   converted a POST request to a GET request with long query
1832   information, when the client has descended into a URI "black hole" of
1833   redirection (e.g., a redirected URI prefix that points to a suffix of
1834   itself), or when the server is under attack by a client attempting to
1835   exploit security holes present in some servers using fixed-length
1836   buffers for reading or manipulating the effective request URI.
1837</t>
1838</section>
1839
1840<section title="415 Unsupported Media Type" anchor="status.415">
1841  <iref primary="true" item="415 Unsupported Media Type (status code)"/>
1842  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type"/>
1843<t>
1844   The server is refusing to service the request because the request
1845   payload is in a format not supported by this request method on the
1846   target resource.
1847</t>
1848</section>
1849
1850<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1851  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)"/>
1852  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable"/>
1853 
1854<t>
1855   The request included a Range header field (Section 5.4 of <xref target="Part5"/>) and none of
1856   the range-specifier values in this field overlap the current extent
1857   of the selected resource. See Section 3.2 of <xref target="Part5"/>.
1858</t>
1859</section>
1860
1861<section title="417 Expectation Failed" anchor="status.417">
1862  <iref primary="true" item="417 Expectation Failed (status code)"/>
1863  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed"/>
1864<t>
1865   The expectation given in an Expect header field (see <xref target="header.expect"/>)
1866   could not be met by this server, or, if the server is a proxy,
1867   the server has unambiguous evidence that the request could not be met
1868   by the next-hop server.
1869</t>
1870</section>
1871
1872<section title="426 Upgrade Required" anchor="status.426">
1873  <iref primary="true" item="426 Upgrade Required (status code)"/>
1874  <iref primary="true" item="Status Codes" subitem="426 Upgrade Required"/>
1875<t>
1876   The request can not be completed without a prior protocol upgrade. This
1877   response MUST include an Upgrade header field (Section 9.8 of <xref target="Part1"/>)
1878   specifying the required protocols.
1879</t>
1880<figure>
1881<preamble>Example:</preamble>
1882<artwork type="message/http; msgtype=&#34;request&#34;"><![CDATA[
1883  HTTP/1.1 426 Upgrade Required
1884  Upgrade: HTTP/2.0
1885  Connection: Upgrade
1886 
1887  ]]></artwork></figure>
1888<t>
1889   The server SHOULD include a message body in the 426 response which
1890   indicates in human readable form the reason for the error and describes any
1891   alternative courses which may be available to the user.
1892</t>
1893</section>
1894</section>
1895
1896<section title="Server Error 5xx" anchor="status.5xx">
1897<t>
1898   Response status codes beginning with the digit "5" indicate cases in
1899   which the server is aware that it has erred or is incapable of
1900   performing the request. Except when responding to a HEAD request, the
1901   server SHOULD include a representation containing an explanation of the
1902   error situation, and whether it is a temporary or permanent
1903   condition. User agents SHOULD display any included representation to the
1904   user. These response codes are applicable to any request method.
1905</t>
1906
1907<section title="500 Internal Server Error" anchor="status.500">
1908  <iref primary="true" item="500 Internal Server Error (status code)"/>
1909  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error"/>
1910<t>
1911   The server encountered an unexpected condition which prevented it
1912   from fulfilling the request.
1913</t>
1914</section>
1915
1916<section title="501 Not Implemented" anchor="status.501">
1917  <iref primary="true" item="501 Not Implemented (status code)"/>
1918  <iref primary="true" item="Status Codes" subitem="501 Not Implemented"/>
1919<t>
1920   The server does not support the functionality required to fulfill the
1921   request. This is the appropriate response when the server does not
1922   recognize the request method and is not capable of supporting it for
1923   any resource.
1924</t>
1925</section>
1926
1927<section title="502 Bad Gateway" anchor="status.502">
1928  <iref primary="true" item="502 Bad Gateway (status code)"/>
1929  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway"/>
1930<t>
1931   The server, while acting as a gateway or proxy, received an invalid
1932   response from the upstream server it accessed in attempting to
1933   fulfill the request.
1934</t>
1935</section>
1936
1937<section title="503 Service Unavailable" anchor="status.503">
1938  <iref primary="true" item="503 Service Unavailable (status code)"/>
1939  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable"/>
1940<t>
1941   The server is currently unable to handle the request due to a
1942   temporary overloading or maintenance of the server. The implication
1943   is that this is a temporary condition which will be alleviated after
1944   some delay. If known, the length of the delay MAY be indicated in a
1945   Retry-After header field. If no Retry-After is given, the client SHOULD
1946   handle the response as it would for a 500 response.
1947</t>
1948<t><list>
1949  <t>
1950    Note: The existence of the 503 status code does not imply that a
1951    server must use it when becoming overloaded. Some servers might wish
1952    to simply refuse the connection.
1953  </t>
1954</list></t>
1955</section>
1956
1957<section title="504 Gateway Timeout" anchor="status.504">
1958  <iref primary="true" item="504 Gateway Timeout (status code)"/>
1959  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout"/>
1960<t>
1961   The server, while acting as a gateway or proxy, did not receive a
1962   timely response from the upstream server specified by the URI (e.g.,
1963   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
1964   to access in attempting to complete the request.
1965</t>
1966<t><list>
1967  <t>
1968    Note to implementors: some deployed proxies are known to
1969    return 400 or 500 when DNS lookups time out.
1970  </t>
1971</list></t>
1972</section>
1973
1974<section title="505 HTTP Version Not Supported" anchor="status.505">
1975  <iref primary="true" item="505 HTTP Version Not Supported (status code)"/>
1976  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported"/>
1977<t>
1978   The server does not support, or refuses to support, the protocol
1979   version that was used in the request message. The server is
1980   indicating that it is unable or unwilling to complete the request
1981   using the same major version as the client, as described in Section 2.5 of <xref target="Part1"/>,
1982   other than with this error message. The response SHOULD contain
1983   a representation describing why that version is not supported and what other
1984   protocols are supported by that server.
1985</t>
1986
1987</section>
1988</section>
1989</section>
1990
1991
1992<section title="Header Field Definitions" anchor="header.fields">
1993<t>
1994   This section defines the syntax and semantics of HTTP/1.1 header fields
1995   related to request and response semantics.
1996</t>
1997
1998<section title="Allow" anchor="header.allow">
1999  <iref primary="true" item="Allow header field"/>
2000  <iref primary="true" item="Header Fields" subitem="Allow"/>
2001 
2002 
2003<t>
2004   The "Allow" header field lists the set of methods advertised as
2005   supported by the target resource. The purpose of this field is strictly to
2006   inform the recipient of valid request methods associated with the resource.
2007</t>
2008<figure><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/><artwork type="abnf2616"><![CDATA[
2009  Allow   = "Allow" ":" OWS Allow-v
2010  Allow-v = #Method
2011]]></artwork></figure>
2012<t>
2013   Example of use:
2014</t>
2015<figure><artwork type="example"><![CDATA[
2016  Allow: GET, HEAD, PUT
2017]]></artwork></figure>
2018<t>
2019   The actual set of allowed methods is defined by the origin server at the
2020   time of each request.
2021</t>
2022<t>
2023   A proxy MUST NOT modify the Allow header field — it does not need to
2024   understand all the methods specified in order to handle them according to
2025   the generic message handling rules.
2026</t>
2027</section>
2028
2029<section title="Expect" anchor="header.expect">
2030  <iref primary="true" item="Expect header field"/>
2031  <iref primary="true" item="Header Fields" subitem="Expect"/>
2032 
2033 
2034 
2035 
2036 
2037<t>
2038   The "Expect" header field is used to indicate that particular
2039   server behaviors are required by the client.
2040</t>
2041<figure><iref primary="true" item="Grammar" subitem="Expect"/><iref primary="true" item="Grammar" subitem="Expect-v"/><iref primary="true" item="Grammar" subitem="expectation"/><iref primary="true" item="Grammar" subitem="expectation-extension"/><iref primary="true" item="Grammar" subitem="expect-params"/><artwork type="abnf2616"><![CDATA[
2042  Expect       = "Expect" ":" OWS Expect-v
2043  Expect-v     = 1#expectation
2044 
2045  expectation  = "100-continue" / expectation-extension
2046  expectation-extension = token [ "=" ( token / quoted-string )
2047                           *expect-params ]
2048  expect-params = ";" token [ "=" ( token / quoted-string ) ]
2049]]></artwork></figure>
2050<t>
2051   A server that does not understand or is unable to comply with any of
2052   the expectation values in the Expect field of a request MUST respond
2053   with appropriate error status code. The server MUST respond with a 417
2054   (Expectation Failed) status code if any of the expectations cannot be met
2055   or, if there are other problems with the request, some other 4xx
2056   status code.
2057</t>
2058<t>
2059   This header field is defined with extensible syntax to allow for
2060   future extensions. If a server receives a request containing an
2061   Expect field that includes an expectation-extension that it does not
2062   support, it MUST respond with a 417 (Expectation Failed) status code.
2063</t>
2064<t>
2065   Comparison of expectation values is case-insensitive for unquoted
2066   tokens (including the 100-continue token), and is case-sensitive for
2067   quoted-string expectation-extensions.
2068</t>
2069<t>
2070   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy MUST
2071   return a 417 (Expectation Failed) status code if it receives a request
2072   with an expectation that it cannot meet. However, the Expect
2073   header field itself is end-to-end; it MUST be forwarded if the
2074   request is forwarded.
2075</t>
2076<t>
2077   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
2078   Expect header field.
2079</t>
2080<t>
2081   See Section 7.2.3 of <xref target="Part1"/> for the use of the 100 (Continue) status code.
2082</t>
2083</section>
2084
2085<section title="From" anchor="header.from">
2086  <iref primary="true" item="From header field"/>
2087  <iref primary="true" item="Header Fields" subitem="From"/>
2088 
2089 
2090 
2091<t>
2092   The "From" header field, if given, SHOULD contain an Internet
2093   e-mail address for the human user who controls the requesting user
2094   agent. The address SHOULD be machine-usable, as defined by "mailbox"
2095   in Section 3.4 of <xref target="RFC5322"/>:
2096</t>
2097<figure><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/><artwork type="abnf2616"><![CDATA[
2098  From    = "From" ":" OWS From-v
2099  From-v  = mailbox
2100 
2101  mailbox = <mailbox, defined in [RFC5322], Section 3.4>
2102]]></artwork></figure>
2103<t>
2104   An example is:
2105</t>
2106<figure><artwork type="example"><![CDATA[
2107  From: webmaster@example.org
2108]]></artwork></figure>
2109<t>
2110   This header field MAY be used for logging purposes and as a means for
2111   identifying the source of invalid or unwanted requests. It SHOULD NOT
2112   be used as an insecure form of access protection. The interpretation
2113   of this field is that the request is being performed on behalf of the
2114   person given, who accepts responsibility for the method performed. In
2115   particular, robot agents SHOULD include this header field so that the
2116   person responsible for running the robot can be contacted if problems
2117   occur on the receiving end.
2118</t>
2119<t>
2120   The Internet e-mail address in this field MAY be separate from the
2121   Internet host which issued the request. For example, when a request
2122   is passed through a proxy the original issuer's address SHOULD be
2123   used.
2124</t>
2125<t>
2126   The client SHOULD NOT  send the From header field without the user's
2127   approval, as it might conflict with the user's privacy interests or
2128   their site's security policy. It is strongly recommended that the
2129   user be able to disable, enable, and modify the value of this field
2130   at any time prior to a request.
2131</t>
2132</section>
2133
2134<section title="Location" anchor="header.location">
2135  <iref primary="true" item="Location header field"/>
2136  <iref primary="true" item="Header Fields" subitem="Location"/>
2137 
2138 
2139<t>
2140   The "Location" header field is used to identify a newly created
2141   resource, or to redirect the recipient to a different location for
2142   completion of the request.
2143</t>
2144<t>
2145   For 201 (Created) responses, the Location is the URI of the new resource
2146   which was created by the request. For 3xx responses, the location SHOULD
2147   indicate the server's preferred URI for automatic redirection to the
2148   resource.
2149</t>
2150<t>
2151   The field value consists of a single URI-reference. When it has the form
2152   of a relative reference (<xref target="RFC3986"/>, Section 4.2),
2153   the final value is computed by resolving it against the effective request
2154   URI (<xref target="RFC3986"/>, Section 5).
2155</t>
2156<figure><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/><artwork type="abnf2616"><![CDATA[
2157  Location       = "Location" ":" OWS Location-v
2158  Location-v     = URI-reference
2159]]></artwork></figure>
2160<figure>
2161<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical WSP below, it's necessary this way for xml2rfc-->
2162<artwork type="example"><![CDATA[
2163  Location: http://www.example.org/pub/WWW/People.html#tim
2164]]></artwork></figure><figure><artwork type="example"><![CDATA[  Location: /index.html
2165]]></artwork></figure>
2166<t>
2167   There are circumstances in which a fragment identifier in a Location URI
2168   would not be appropriate:
2169   <list style="symbols">
2170      <t>With a 201 Created response, because in this usage the Location header
2171      field specifies the URI for the entire created resource.</t>
2172      <t>With 305 Use Proxy.</t>
2173   </list>
2174</t>
2175<t><list>
2176  <t>
2177    Note: This specification does not define precedence rules
2178    for the case where the original URI, as navigated to by the user
2179    agent, and the Location header field value both contain fragment
2180    identifiers. Thus be aware that including fragment identifiers might
2181    inconvenience anyone relying on the semantics of the original URI's
2182    fragment identifier.
2183  </t>
2184</list></t>
2185<t><list>
2186  <t>
2187    Note: The Content-Location header field (Section 6.7 of <xref target="Part3"/>) differs
2188    from Location in that the Content-Location identifies the most specific
2189    resource corresponding to the enclosed representation.
2190    It is therefore possible for a response to contain header fields for
2191    both Location and Content-Location.
2192  </t>
2193</list></t>
2194</section>
2195
2196<section title="Max-Forwards" anchor="header.max-forwards">
2197  <iref primary="true" item="Max-Forwards header field"/>
2198  <iref primary="true" item="Header Fields" subitem="Max-Forwards"/>
2199 
2200 
2201<t>
2202   The "Max-Forwards" header field provides a mechanism with the
2203   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2204   methods to limit the number of times that the request is forwarded by
2205   proxies. This can be useful when the client is attempting to
2206   trace a request which appears to be failing or looping in mid-chain.
2207</t>
2208<figure><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/><artwork type="abnf2616"><![CDATA[
2209  Max-Forwards   = "Max-Forwards" ":" OWS Max-Forwards-v
2210  Max-Forwards-v = 1*DIGIT
2211]]></artwork></figure>
2212<t>
2213   The Max-Forwards value is a decimal integer indicating the remaining
2214   number of times this request message can be forwarded.
2215</t>
2216<t>
2217   Each recipient of a TRACE or OPTIONS request
2218   containing a Max-Forwards header field MUST check and update its
2219   value prior to forwarding the request. If the received value is zero
2220   (0), the recipient MUST NOT forward the request; instead, it MUST
2221   respond as the final recipient. If the received Max-Forwards value is
2222   greater than zero, then the forwarded message MUST contain an updated
2223   Max-Forwards field with a value decremented by one (1).
2224</t>
2225<t>
2226   The Max-Forwards header field MAY be ignored for all other request
2227   methods.
2228</t>
2229</section>
2230
2231<section title="Referer" anchor="header.referer">
2232  <iref primary="true" item="Referer header field"/>
2233  <iref primary="true" item="Header Fields" subitem="Referer"/>
2234 
2235 
2236<t>
2237   The "Referer" [sic] header field allows the client to specify the
2238   URI of the resource from which the effective request URI was obtained (the
2239   "referrer", although the header field is misspelled.).
2240</t>
2241<t>
2242   The Referer header field allows servers to generate lists of back-links to
2243   resources for interest, logging, optimized caching, etc. It also allows
2244   obsolete or mistyped links to be traced for maintenance. Some servers use
2245   Referer as a means of controlling where they allow links from (so-called
2246   "deep linking"), but legitimate requests do not always
2247   contain a Referer header field.
2248</t>
2249<t>
2250   If the effective request URI was obtained from a source that does not have its own
2251   URI (e.g., input from the user keyboard), the Referer field MUST either be
2252   sent with the value "about:blank", or not be sent at all. Note that this
2253   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2254</t>
2255<figure><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/><artwork type="abnf2616"><![CDATA[
2256  Referer        = "Referer" ":" OWS Referer-v
2257  Referer-v      = absolute-URI / partial-URI
2258]]></artwork></figure>
2259<t>
2260   Example:
2261</t>
2262<figure><artwork type="example"><![CDATA[
2263  Referer: http://www.example.org/hypertext/Overview.html
2264]]></artwork></figure>
2265<t>
2266   If the field value is a relative URI, it SHOULD be interpreted
2267   relative to the effective request URI. The URI MUST NOT include a fragment. See
2268   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2269</t>
2270</section>
2271
2272<section title="Retry-After" anchor="header.retry-after">
2273  <iref primary="true" item="Retry-After header field"/>
2274  <iref primary="true" item="Header Fields" subitem="Retry-After"/>
2275 
2276 
2277<t>
2278   The header "Retry-After" field can be used with a 503 (Service
2279   Unavailable) response to indicate how long the service is expected to
2280   be unavailable to the requesting client. This field MAY also be used
2281   with any 3xx (Redirection) response to indicate the minimum time the
2282   user-agent is asked wait before issuing the redirected request.
2283</t>
2284<t>
2285   The value of this field can be either an HTTP-date or an integer number
2286   of seconds (in decimal) after the time of the response.
2287</t>
2288<figure><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/><artwork type="abnf2616"><![CDATA[
2289  Retry-After   = "Retry-After" ":" OWS Retry-After-v
2290  Retry-After-v = HTTP-date / delta-seconds
2291]]></artwork></figure>
2292<t anchor="rule.delta-seconds">
2293 
2294   Time spans are non-negative decimal integers, representing time in
2295   seconds.
2296</t>
2297<figure><iref primary="true" item="Grammar" subitem="delta-seconds"/><artwork type="abnf2616"><![CDATA[
2298  delta-seconds  = 1*DIGIT
2299]]></artwork></figure>
2300<t>
2301   Two examples of its use are
2302</t>
2303<figure><artwork type="example"><![CDATA[
2304  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2305  Retry-After: 120
2306]]></artwork></figure>
2307<t>
2308   In the latter example, the delay is 2 minutes.
2309</t>
2310</section>
2311
2312<section title="Server" anchor="header.server">
2313  <iref primary="true" item="Server header field"/>
2314  <iref primary="true" item="Header Fields" subitem="Server"/>
2315 
2316 
2317<t>
2318   The "Server" header field contains information about the
2319   software used by the origin server to handle the request.
2320</t>
2321<t>
2322   The field can contain multiple product tokens (Section 6.3 of <xref target="Part1"/>) and
2323   comments (Section 3.2 of <xref target="Part1"/>) identifying the server and any significant
2324   subproducts. The product tokens are listed in order of their significance
2325   for identifying the application.
2326</t>
2327<figure><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/><artwork type="abnf2616"><![CDATA[
2328  Server         = "Server" ":" OWS Server-v
2329  Server-v       = product
2330                   *( RWS ( product / comment ) )
2331]]></artwork></figure>
2332<t>
2333   Example:
2334</t>
2335<figure><artwork type="example"><![CDATA[
2336  Server: CERN/3.0 libwww/2.17
2337]]></artwork></figure>
2338<t>
2339   If the response is being forwarded through a proxy, the proxy
2340   application MUST NOT modify the Server header field. Instead, it
2341   MUST include a Via field (as described in Section 9.9 of <xref target="Part1"/>).
2342</t>
2343<t><list>
2344  <t>
2345    Note: Revealing the specific software version of the server might
2346    allow the server machine to become more vulnerable to attacks
2347    against software that is known to contain security holes. Server
2348    implementors are encouraged to make this field a configurable
2349    option.
2350  </t>
2351</list></t>
2352</section>
2353
2354<section title="User-Agent" anchor="header.user-agent">
2355  <iref primary="true" item="User-Agent header field"/>
2356  <iref primary="true" item="Header Fields" subitem="User-Agent"/>
2357 
2358 
2359<t>
2360   The "User-Agent" header field contains information about the user
2361   agent originating the request. User agents SHOULD include this field with
2362   requests.
2363</t>
2364<t>
2365   Typically, it is used for statistical purposes, the tracing of protocol
2366   violations, and tailoring responses to avoid particular user agent
2367   limitations.
2368</t>
2369<t>
2370   The field can contain multiple product tokens (Section 6.3 of <xref target="Part1"/>)
2371   and comments (Section 3.2 of <xref target="Part1"/>) identifying the agent and its
2372   significant subproducts. By convention, the product tokens are listed in
2373   order of their significance for identifying the application.
2374</t>
2375<t>
2376   Because this field is usually sent on every request a user agent makes,
2377   implementations are encouraged not to include needlessly fine-grained
2378   detail, and to limit (or even prohibit) the addition of subproducts by third
2379   parties. Overly long and detailed User-Agent field values make requests
2380   larger and can also be used to identify ("fingerprint") the user against
2381   their wishes.
2382</t>
2383<t>
2384   Likewise, implementations are encouraged not to use the product tokens of
2385   other implementations in order to declare compatibility with them, as this
2386   circumvents the purpose of the field. Finally, they are encouraged not to
2387   use comments to identify products; doing so makes the field value more
2388   difficult to parse.
2389</t>
2390<figure><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/><artwork type="abnf2616"><![CDATA[
2391  User-Agent     = "User-Agent" ":" OWS User-Agent-v
2392  User-Agent-v   = product *( RWS ( product / comment ) )
2393]]></artwork></figure>
2394<t>
2395   Example:
2396</t>
2397<figure><artwork type="example"><![CDATA[
2398  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2399]]></artwork></figure>
2400</section>
2401
2402</section>
2403
2404<section title="IANA Considerations" anchor="IANA.considerations">
2405
2406<section title="Method Registry" anchor="method.registration">
2407<t>
2408  The registration procedure for HTTP request methods is defined by
2409  <xref target="method.registry"/> of this document.
2410</t>
2411<t>
2412   The HTTP Method Registry shall be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2413   and be populated with the registrations below:
2414</t>
2415
2416<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2417<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2418   <ttcol>Method</ttcol>
2419   <ttcol>Safe</ttcol>
2420   <ttcol>Reference</ttcol>
2421   <c>CONNECT</c>
2422   <c>no</c>
2423   <c>
2424      <xref target="CONNECT"/>
2425   </c>
2426   <c>DELETE</c>
2427   <c>no</c>
2428   <c>
2429      <xref target="DELETE"/>
2430   </c>
2431   <c>GET</c>
2432   <c>yes</c>
2433   <c>
2434      <xref target="GET"/>
2435   </c>
2436   <c>HEAD</c>
2437   <c>yes</c>
2438   <c>
2439      <xref target="HEAD"/>
2440   </c>
2441   <c>OPTIONS</c>
2442   <c>yes</c>
2443   <c>
2444      <xref target="OPTIONS"/>
2445   </c>
2446   <c>POST</c>
2447   <c>no</c>
2448   <c>
2449      <xref target="POST"/>
2450   </c>
2451   <c>PUT</c>
2452   <c>no</c>
2453   <c>
2454      <xref target="PUT"/>
2455   </c>
2456   <c>TRACE</c>
2457   <c>yes</c>
2458   <c>
2459      <xref target="TRACE"/>
2460   </c>
2461</texttable>
2462<!--(END)-->
2463
2464</section>
2465
2466<section title="Status Code Registry" anchor="status.code.registration">
2467<t>
2468   The registration procedure for HTTP Status Codes — previously defined
2469   in Section 7.1 of <xref target="RFC2817"/> — is now defined
2470   by <xref target="status.code.registry"/> of this document.
2471</t>
2472<t>
2473   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2474   shall be updated with the registrations below:
2475</t>
2476
2477<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2478<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2479   <ttcol>Value</ttcol>
2480   <ttcol>Description</ttcol>
2481   <ttcol>Reference</ttcol>
2482   <c>100</c>
2483   <c>Continue</c>
2484   <c>
2485      <xref target="status.100"/>
2486   </c>
2487   <c>101</c>
2488   <c>Switching Protocols</c>
2489   <c>
2490      <xref target="status.101"/>
2491   </c>
2492   <c>200</c>
2493   <c>OK</c>
2494   <c>
2495      <xref target="status.200"/>
2496   </c>
2497   <c>201</c>
2498   <c>Created</c>
2499   <c>
2500      <xref target="status.201"/>
2501   </c>
2502   <c>202</c>
2503   <c>Accepted</c>
2504   <c>
2505      <xref target="status.202"/>
2506   </c>
2507   <c>203</c>
2508   <c>Non-Authoritative Information</c>
2509   <c>
2510      <xref target="status.203"/>
2511   </c>
2512   <c>204</c>
2513   <c>No Content</c>
2514   <c>
2515      <xref target="status.204"/>
2516   </c>
2517   <c>205</c>
2518   <c>Reset Content</c>
2519   <c>
2520      <xref target="status.205"/>
2521   </c>
2522   <c>300</c>
2523   <c>Multiple Choices</c>
2524   <c>
2525      <xref target="status.300"/>
2526   </c>
2527   <c>301</c>
2528   <c>Moved Permanently</c>
2529   <c>
2530      <xref target="status.301"/>
2531   </c>
2532   <c>302</c>
2533   <c>Found</c>
2534   <c>
2535      <xref target="status.302"/>
2536   </c>
2537   <c>303</c>
2538   <c>See Other</c>
2539   <c>
2540      <xref target="status.303"/>
2541   </c>
2542   <c>305</c>
2543   <c>Use Proxy</c>
2544   <c>
2545      <xref target="status.305"/>
2546   </c>
2547   <c>306</c>
2548   <c>(Unused)</c>
2549   <c>
2550      <xref target="status.306"/>
2551   </c>
2552   <c>307</c>
2553   <c>Temporary Redirect</c>
2554   <c>
2555      <xref target="status.307"/>
2556   </c>
2557   <c>400</c>
2558   <c>Bad Request</c>
2559   <c>
2560      <xref target="status.400"/>
2561   </c>
2562   <c>402</c>
2563   <c>Payment Required</c>
2564   <c>
2565      <xref target="status.402"/>
2566   </c>
2567   <c>403</c>
2568   <c>Forbidden</c>
2569   <c>
2570      <xref target="status.403"/>
2571   </c>
2572   <c>404</c>
2573   <c>Not Found</c>
2574   <c>
2575      <xref target="status.404"/>
2576   </c>
2577   <c>405</c>
2578   <c>Method Not Allowed</c>
2579   <c>
2580      <xref target="status.405"/>
2581   </c>
2582   <c>406</c>
2583   <c>Not Acceptable</c>
2584   <c>
2585      <xref target="status.406"/>
2586   </c>
2587   <c>407</c>
2588   <c>Proxy Authentication Required</c>
2589   <c>
2590      <xref target="status.407"/>
2591   </c>
2592   <c>408</c>
2593   <c>Request Timeout</c>
2594   <c>
2595      <xref target="status.408"/>
2596   </c>
2597   <c>409</c>
2598   <c>Conflict</c>
2599   <c>
2600      <xref target="status.409"/>
2601   </c>
2602   <c>410</c>
2603   <c>Gone</c>
2604   <c>
2605      <xref target="status.410"/>
2606   </c>
2607   <c>411</c>
2608   <c>Length Required</c>
2609   <c>
2610      <xref target="status.411"/>
2611   </c>
2612   <c>413</c>
2613   <c>Request Entity Too Large</c>
2614   <c>
2615      <xref target="status.413"/>
2616   </c>
2617   <c>414</c>
2618   <c>URI Too Long</c>
2619   <c>
2620      <xref target="status.414"/>
2621   </c>
2622   <c>415</c>
2623   <c>Unsupported Media Type</c>
2624   <c>
2625      <xref target="status.415"/>
2626   </c>
2627   <c>417</c>
2628   <c>Expectation Failed</c>
2629   <c>
2630      <xref target="status.417"/>
2631   </c>
2632   <c>426</c>
2633   <c>Upgrade Required</c>
2634   <c>
2635      <xref target="status.426"/>
2636   </c>
2637   <c>500</c>
2638   <c>Internal Server Error</c>
2639   <c>
2640      <xref target="status.500"/>
2641   </c>
2642   <c>501</c>
2643   <c>Not Implemented</c>
2644   <c>
2645      <xref target="status.501"/>
2646   </c>
2647   <c>502</c>
2648   <c>Bad Gateway</c>
2649   <c>
2650      <xref target="status.502"/>
2651   </c>
2652   <c>503</c>
2653   <c>Service Unavailable</c>
2654   <c>
2655      <xref target="status.503"/>
2656   </c>
2657   <c>504</c>
2658   <c>Gateway Timeout</c>
2659   <c>
2660      <xref target="status.504"/>
2661   </c>
2662   <c>505</c>
2663   <c>HTTP Version Not Supported</c>
2664   <c>
2665      <xref target="status.505"/>
2666   </c>
2667</texttable>
2668<!--(END)-->
2669
2670</section>
2671<section title="Header Field Registration" anchor="header.field.registration">
2672<t>
2673   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
2674   with the permanent registrations below (see <xref target="RFC3864"/>):
2675</t>
2676
2677<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2678<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2679   <ttcol>Header Field Name</ttcol>
2680   <ttcol>Protocol</ttcol>
2681   <ttcol>Status</ttcol>
2682   <ttcol>Reference</ttcol>
2683
2684   <c>Allow</c>
2685   <c>http</c>
2686   <c>standard</c>
2687   <c>
2688      <xref target="header.allow"/>
2689   </c>
2690   <c>Expect</c>
2691   <c>http</c>
2692   <c>standard</c>
2693   <c>
2694      <xref target="header.expect"/>
2695   </c>
2696   <c>From</c>
2697   <c>http</c>
2698   <c>standard</c>
2699   <c>
2700      <xref target="header.from"/>
2701   </c>
2702   <c>Location</c>
2703   <c>http</c>
2704   <c>standard</c>
2705   <c>
2706      <xref target="header.location"/>
2707   </c>
2708   <c>Max-Forwards</c>
2709   <c>http</c>
2710   <c>standard</c>
2711   <c>
2712      <xref target="header.max-forwards"/>
2713   </c>
2714   <c>Referer</c>
2715   <c>http</c>
2716   <c>standard</c>
2717   <c>
2718      <xref target="header.referer"/>
2719   </c>
2720   <c>Retry-After</c>
2721   <c>http</c>
2722   <c>standard</c>
2723   <c>
2724      <xref target="header.retry-after"/>
2725   </c>
2726   <c>Server</c>
2727   <c>http</c>
2728   <c>standard</c>
2729   <c>
2730      <xref target="header.server"/>
2731   </c>
2732   <c>User-Agent</c>
2733   <c>http</c>
2734   <c>standard</c>
2735   <c>
2736      <xref target="header.user-agent"/>
2737   </c>
2738</texttable>
2739<!--(END)-->
2740
2741<t>
2742   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2743</t>
2744</section>
2745</section>
2746
2747<section title="Security Considerations" anchor="security.considerations">
2748<t>
2749   This section is meant to inform application developers, information
2750   providers, and users of the security limitations in HTTP/1.1 as
2751   described by this document. The discussion does not include
2752   definitive solutions to the problems revealed, though it does make
2753   some suggestions for reducing security risks.
2754</t>
2755
2756<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2757<t>
2758   Like any generic data transfer protocol, HTTP cannot regulate the
2759   content of the data that is transferred, nor is there any a priori
2760   method of determining the sensitivity of any particular piece of
2761   information within the context of any given request. Therefore,
2762   applications SHOULD supply as much control over this information as
2763   possible to the provider of that information. Four header fields are
2764   worth special mention in this context: Server, Via, Referer and From.
2765</t>
2766<t>
2767   Revealing the specific software version of the server might allow the
2768   server machine to become more vulnerable to attacks against software
2769   that is known to contain security holes. Implementors SHOULD make the
2770   Server header field a configurable option.
2771</t>
2772<t>
2773   Proxies which serve as a portal through a network firewall SHOULD
2774   take special precautions regarding the transfer of header information
2775   that identifies the hosts behind the firewall. In particular, they
2776   SHOULD remove, or replace with sanitized versions, any Via fields
2777   generated behind the firewall.
2778</t>
2779<t>
2780   The Referer header field allows reading patterns to be studied and reverse
2781   links drawn. Although it can be very useful, its power can be abused
2782   if user details are not separated from the information contained in
2783   the Referer. Even when the personal information has been removed, the
2784   Referer header field might indicate a private document's URI whose
2785   publication would be inappropriate.
2786</t>
2787<t>
2788   The information sent in the From field might conflict with the user's
2789   privacy interests or their site's security policy, and hence it
2790   SHOULD NOT  be transmitted without the user being able to disable,
2791   enable, and modify the contents of the field. The user MUST be able
2792   to set the contents of this field within a user preference or
2793   application defaults configuration.
2794</t>
2795<t>
2796   We suggest, though do not require, that a convenient toggle interface
2797   be provided for the user to enable or disable the sending of From and
2798   Referer information.
2799</t>
2800<t>
2801   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header fields can sometimes be used to determine
2802   that a specific client or server have a particular security hole which might
2803   be exploited. Unfortunately, this same information is often used for other
2804   valuable purposes for which HTTP currently has no better mechanism.
2805</t>
2806<t>
2807   Furthermore, the User-Agent header field may contain enough entropy to be
2808   used, possibly in conjunction with other material, to uniquely identify the
2809   user.
2810</t>
2811<t>
2812   Some request methods, like TRACE (<xref target="TRACE"/>), expose information
2813   that was sent in request header fields within the body of their response.
2814   Clients SHOULD be careful with sensitive information, like Cookies,
2815   Authorization credentials, and other header fields that might be used to
2816   collect data from the client.
2817</t>
2818</section>
2819
2820<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2821<t>
2822   Because the source of a link might be private information or might
2823   reveal an otherwise private information source, it is strongly
2824   recommended that the user be able to select whether or not the
2825   Referer field is sent. For example, a browser client could have a
2826   toggle switch for browsing openly/anonymously, which would
2827   respectively enable/disable the sending of Referer and From
2828   information.
2829</t>
2830<t>
2831   Clients SHOULD NOT include a Referer header field in a (non-secure)
2832   HTTP request if the referring page was transferred with a secure
2833   protocol.
2834</t>
2835<t>
2836   Authors of services SHOULD NOT use GET-based forms for the submission of
2837   sensitive data because that data will be placed in the request-target. Many
2838   existing servers, proxies, and user agents log or display the request-target
2839   in places where it might be visible to third parties. Such services can
2840   use POST-based form submission instead.
2841</t>
2842</section>
2843
2844<section title="Location Headers and Spoofing" anchor="location.spoofing">
2845<t>
2846   If a single server supports multiple organizations that do not trust
2847   one another, then it MUST check the values of Location and Content-Location
2848   header fields in responses that are generated under control of
2849   said organizations to make sure that they do not attempt to
2850   invalidate resources over which they have no authority.
2851</t>
2852</section>
2853
2854<section title="Security Considerations for CONNECT">
2855<t>
2856   Since tunneled data is opaque to the proxy, there are additional
2857   risks to tunneling to other well-known or reserved ports.
2858   A HTTP client CONNECTing to port 25 could relay spam
2859   via SMTP, for example. As such, proxies SHOULD restrict CONNECT
2860   access to a small number of known ports.
2861</t>
2862</section>
2863
2864</section>
2865
2866<section title="Acknowledgments" anchor="ack">
2867</section>
2868</middle>
2869<back>
2870
2871<references title="Normative References">
2872
2873<reference anchor="Part1">
2874  <front>
2875    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2876    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2877      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
2878      <address><email>fielding@gbiv.com</email></address>
2879    </author>
2880    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2881      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2882      <address><email>jg@freedesktop.org</email></address>
2883    </author>
2884    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2885      <organization abbrev="HP">Hewlett-Packard Company</organization>
2886      <address><email>JeffMogul@acm.org</email></address>
2887    </author>
2888    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2889      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2890      <address><email>henrikn@microsoft.com</email></address>
2891    </author>
2892    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2893      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
2894      <address><email>LMM@acm.org</email></address>
2895    </author>
2896    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2897      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2898      <address><email>paulle@microsoft.com</email></address>
2899    </author>
2900    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2901      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2902      <address><email>timbl@w3.org</email></address>
2903    </author>
2904    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2905      <organization abbrev="W3C">World Wide Web Consortium</organization>
2906      <address><email>ylafon@w3.org</email></address>
2907    </author>
2908    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2909      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2910      <address><email>julian.reschke@greenbytes.de</email></address>
2911    </author>
2912    <date month="March" year="2011"/>
2913  </front>
2914  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-13"/>
2915 
2916</reference>
2917
2918<reference anchor="Part3">
2919  <front>
2920    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2921    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2922      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
2923      <address><email>fielding@gbiv.com</email></address>
2924    </author>
2925    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2926      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2927      <address><email>jg@freedesktop.org</email></address>
2928    </author>
2929    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2930      <organization abbrev="HP">Hewlett-Packard Company</organization>
2931      <address><email>JeffMogul@acm.org</email></address>
2932    </author>
2933    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2934      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2935      <address><email>henrikn@microsoft.com</email></address>
2936    </author>
2937    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2938      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
2939      <address><email>LMM@acm.org</email></address>
2940    </author>
2941    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2942      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2943      <address><email>paulle@microsoft.com</email></address>
2944    </author>
2945    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2946      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2947      <address><email>timbl@w3.org</email></address>
2948    </author>
2949    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2950      <organization abbrev="W3C">World Wide Web Consortium</organization>
2951      <address><email>ylafon@w3.org</email></address>
2952    </author>
2953    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2954      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2955      <address><email>julian.reschke@greenbytes.de</email></address>
2956    </author>
2957    <date month="March" year="2011"/>
2958  </front>
2959  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-13"/>
2960 
2961</reference>
2962
2963<reference anchor="Part4">
2964  <front>
2965    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2966    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2967      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
2968      <address><email>fielding@gbiv.com</email></address>
2969    </author>
2970    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2971      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2972      <address><email>jg@freedesktop.org</email></address>
2973    </author>
2974    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2975      <organization abbrev="HP">Hewlett-Packard Company</organization>
2976      <address><email>JeffMogul@acm.org</email></address>
2977    </author>
2978    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2979      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2980      <address><email>henrikn@microsoft.com</email></address>
2981    </author>
2982    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2983      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
2984      <address><email>LMM@acm.org</email></address>
2985    </author>
2986    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2987      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2988      <address><email>paulle@microsoft.com</email></address>
2989    </author>
2990    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2991      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2992      <address><email>timbl@w3.org</email></address>
2993    </author>
2994    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2995      <organization abbrev="W3C">World Wide Web Consortium</organization>
2996      <address><email>ylafon@w3.org</email></address>
2997    </author>
2998    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2999      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3000      <address><email>julian.reschke@greenbytes.de</email></address>
3001    </author>
3002    <date month="March" year="2011"/>
3003  </front>
3004  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-13"/>
3005 
3006</reference>
3007
3008<reference anchor="Part5">
3009  <front>
3010    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
3011    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3012      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3013      <address><email>fielding@gbiv.com</email></address>
3014    </author>
3015    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3016      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3017      <address><email>jg@freedesktop.org</email></address>
3018    </author>
3019    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3020      <organization abbrev="HP">Hewlett-Packard Company</organization>
3021      <address><email>JeffMogul@acm.org</email></address>
3022    </author>
3023    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3024      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3025      <address><email>henrikn@microsoft.com</email></address>
3026    </author>
3027    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3028      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3029      <address><email>LMM@acm.org</email></address>
3030    </author>
3031    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3032      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3033      <address><email>paulle@microsoft.com</email></address>
3034    </author>
3035    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3036      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3037      <address><email>timbl@w3.org</email></address>
3038    </author>
3039    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3040      <organization abbrev="W3C">World Wide Web Consortium</organization>
3041      <address><email>ylafon@w3.org</email></address>
3042    </author>
3043    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3044      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3045      <address><email>julian.reschke@greenbytes.de</email></address>
3046    </author>
3047    <date month="March" year="2011"/>
3048  </front>
3049  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-13"/>
3050 
3051</reference>
3052
3053<reference anchor="Part6">
3054  <front>
3055    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
3056    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3057      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3058      <address><email>fielding@gbiv.com</email></address>
3059    </author>
3060    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3061      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3062      <address><email>jg@freedesktop.org</email></address>
3063    </author>
3064    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3065      <organization abbrev="HP">Hewlett-Packard Company</organization>
3066      <address><email>JeffMogul@acm.org</email></address>
3067    </author>
3068    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3069      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3070      <address><email>henrikn@microsoft.com</email></address>
3071    </author>
3072    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3073      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3074      <address><email>LMM@acm.org</email></address>
3075    </author>
3076    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3077      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3078      <address><email>paulle@microsoft.com</email></address>
3079    </author>
3080    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3081      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3082      <address><email>timbl@w3.org</email></address>
3083    </author>
3084    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3085      <organization abbrev="W3C">World Wide Web Consortium</organization>
3086      <address><email>ylafon@w3.org</email></address>
3087    </author>
3088    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
3089      <address><email>mnot@mnot.net</email></address>
3090    </author>
3091    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3092      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3093      <address><email>julian.reschke@greenbytes.de</email></address>
3094    </author>
3095    <date month="March" year="2011"/>
3096  </front>
3097  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-13"/>
3098 
3099</reference>
3100
3101<reference anchor="Part7">
3102  <front>
3103    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
3104    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3105      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3106      <address><email>fielding@gbiv.com</email></address>
3107    </author>
3108    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3109      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3110      <address><email>jg@freedesktop.org</email></address>
3111    </author>
3112    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3113      <organization abbrev="HP">Hewlett-Packard Company</organization>
3114      <address><email>JeffMogul@acm.org</email></address>
3115    </author>
3116    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3117      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3118      <address><email>henrikn@microsoft.com</email></address>
3119    </author>
3120    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3121      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3122      <address><email>LMM@acm.org</email></address>
3123    </author>
3124    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3125      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3126      <address><email>paulle@microsoft.com</email></address>
3127    </author>
3128    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3129      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3130      <address><email>timbl@w3.org</email></address>
3131    </author>
3132    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3133      <organization abbrev="W3C">World Wide Web Consortium</organization>
3134      <address><email>ylafon@w3.org</email></address>
3135    </author>
3136    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3137      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3138      <address><email>julian.reschke@greenbytes.de</email></address>
3139    </author>
3140    <date month="March" year="2011"/>
3141  </front>
3142  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-13"/>
3143 
3144</reference>
3145
3146<reference anchor="RFC2119">
3147  <front>
3148    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3149    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3150      <organization>Harvard University</organization>
3151      <address><email>sob@harvard.edu</email></address>
3152    </author>
3153    <date month="March" year="1997"/>
3154  </front>
3155  <seriesInfo name="BCP" value="14"/>
3156  <seriesInfo name="RFC" value="2119"/>
3157</reference>
3158
3159<reference anchor="RFC3986">
3160 <front>
3161  <title abbrev="URI Generic Syntax">Uniform Resource Identifier (URI): Generic Syntax</title>
3162  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3163    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3164    <address>
3165       <email>timbl@w3.org</email>
3166       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3167    </address>
3168  </author>
3169  <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3170    <organization abbrev="Day Software">Day Software</organization>
3171    <address>
3172      <email>fielding@gbiv.com</email>
3173      <uri>http://roy.gbiv.com/</uri>
3174    </address>
3175  </author>
3176  <author initials="L." surname="Masinter" fullname="Larry Masinter">
3177    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3178    <address>
3179      <email>LMM@acm.org</email>
3180      <uri>http://larry.masinter.net/</uri>
3181    </address>
3182  </author>
3183  <date month="January" year="2005"/>
3184 </front>
3185 <seriesInfo name="STD" value="66"/>
3186 <seriesInfo name="RFC" value="3986"/>
3187</reference>
3188
3189<reference anchor="RFC5234">
3190  <front>
3191    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3192    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3193      <organization>Brandenburg InternetWorking</organization>
3194      <address>
3195        <email>dcrocker@bbiw.net</email>
3196      </address> 
3197    </author>
3198    <author initials="P." surname="Overell" fullname="Paul Overell">
3199      <organization>THUS plc.</organization>
3200      <address>
3201        <email>paul.overell@thus.net</email>
3202      </address>
3203    </author>
3204    <date month="January" year="2008"/>
3205  </front>
3206  <seriesInfo name="STD" value="68"/>
3207  <seriesInfo name="RFC" value="5234"/>
3208</reference>
3209
3210</references>
3211
3212<references title="Informative References">
3213
3214<reference anchor="RFC1945">
3215  <front>
3216    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3217    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3218      <organization>MIT, Laboratory for Computer Science</organization>
3219      <address><email>timbl@w3.org</email></address>
3220    </author>
3221    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3222      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3223      <address><email>fielding@ics.uci.edu</email></address>
3224    </author>
3225    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3226      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3227      <address><email>frystyk@w3.org</email></address>
3228    </author>
3229    <date month="May" year="1996"/>
3230  </front>
3231  <seriesInfo name="RFC" value="1945"/>
3232</reference>
3233
3234<reference anchor="RFC2068">
3235  <front>
3236    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3237    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3238      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3239      <address><email>fielding@ics.uci.edu</email></address>
3240    </author>
3241    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3242      <organization>MIT Laboratory for Computer Science</organization>
3243      <address><email>jg@w3.org</email></address>
3244    </author>
3245    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3246      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3247      <address><email>mogul@wrl.dec.com</email></address>
3248    </author>
3249    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3250      <organization>MIT Laboratory for Computer Science</organization>
3251      <address><email>frystyk@w3.org</email></address>
3252    </author>
3253    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3254      <organization>MIT Laboratory for Computer Science</organization>
3255      <address><email>timbl@w3.org</email></address>
3256    </author>
3257    <date month="January" year="1997"/>
3258  </front>
3259  <seriesInfo name="RFC" value="2068"/>
3260</reference>
3261
3262<reference anchor="RFC2616">
3263  <front>
3264    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3265    <author initials="R." surname="Fielding" fullname="R. Fielding">
3266      <organization>University of California, Irvine</organization>
3267      <address><email>fielding@ics.uci.edu</email></address>
3268    </author>
3269    <author initials="J." surname="Gettys" fullname="J. Gettys">
3270      <organization>W3C</organization>
3271      <address><email>jg@w3.org</email></address>
3272    </author>
3273    <author initials="J." surname="Mogul" fullname="J. Mogul">
3274      <organization>Compaq Computer Corporation</organization>
3275      <address><email>mogul@wrl.dec.com</email></address>
3276    </author>
3277    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3278      <organization>MIT Laboratory for Computer Science</organization>
3279      <address><email>frystyk@w3.org</email></address>
3280    </author>
3281    <author initials="L." surname="Masinter" fullname="L. Masinter">
3282      <organization>Xerox Corporation</organization>
3283      <address><email>masinter@parc.xerox.com</email></address>
3284    </author>
3285    <author initials="P." surname="Leach" fullname="P. Leach">
3286      <organization>Microsoft Corporation</organization>
3287      <address><email>paulle@microsoft.com</email></address>
3288    </author>
3289    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3290      <organization>W3C</organization>
3291      <address><email>timbl@w3.org</email></address>
3292    </author>
3293    <date month="June" year="1999"/>
3294  </front>
3295  <seriesInfo name="RFC" value="2616"/>
3296</reference>
3297
3298<reference anchor="RFC2817">
3299  <front>
3300    <title>Upgrading to TLS Within HTTP/1.1</title>
3301    <author initials="R." surname="Khare" fullname="R. Khare">
3302      <organization>4K Associates / UC Irvine</organization>
3303      <address><email>rohit@4K-associates.com</email></address>
3304    </author>
3305    <author initials="S." surname="Lawrence" fullname="S. Lawrence">
3306      <organization>Agranat Systems, Inc.</organization>
3307      <address><email>lawrence@agranat.com</email></address>
3308    </author>
3309    <date year="2000" month="May"/>
3310  </front>
3311  <seriesInfo name="RFC" value="2817"/>
3312</reference>
3313
3314<reference anchor="RFC3864">
3315  <front>
3316    <title>Registration Procedures for Message Header Fields</title>
3317    <author initials="G." surname="Klyne" fullname="G. Klyne">
3318      <organization>Nine by Nine</organization>
3319      <address><email>GK-IETF@ninebynine.org</email></address>
3320    </author>
3321    <author initials="M." surname="Nottingham" fullname="M. Nottingham">
3322      <organization>BEA Systems</organization>
3323      <address><email>mnot@pobox.com</email></address>
3324    </author>
3325    <author initials="J." surname="Mogul" fullname="J. Mogul">
3326      <organization>HP Labs</organization>
3327      <address><email>JeffMogul@acm.org</email></address>
3328    </author>
3329    <date year="2004" month="September"/>
3330  </front>
3331  <seriesInfo name="BCP" value="90"/>
3332  <seriesInfo name="RFC" value="3864"/>
3333</reference>
3334
3335<reference anchor="RFC5226">
3336  <front>
3337    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3338    <author initials="T." surname="Narten" fullname="T. Narten">
3339      <organization>IBM</organization>
3340      <address><email>narten@us.ibm.com</email></address>
3341    </author>
3342    <author initials="H." surname="Alvestrand" fullname="H. Alvestrand">
3343      <organization>Google</organization>
3344      <address><email>Harald@Alvestrand.no</email></address>
3345    </author>
3346    <date year="2008" month="May"/>
3347  </front>
3348  <seriesInfo name="BCP" value="26"/>
3349  <seriesInfo name="RFC" value="5226"/>
3350</reference>
3351
3352<reference anchor="RFC5322">
3353  <front>
3354    <title>Internet Message Format</title>
3355    <author initials="P." surname="Resnick" fullname="P. Resnick">
3356      <organization>Qualcomm Incorporated</organization>
3357    </author>
3358    <date year="2008" month="October"/>
3359  </front>
3360  <seriesInfo name="RFC" value="5322"/>
3361</reference>
3362
3363<reference anchor="RFC5789">
3364  <front>
3365    <title>PATCH Method for HTTP</title>
3366    <author initials="L." surname="Dusseault" fullname="L. Dusseault">
3367      <organization>Linden Lab</organization>
3368    </author>
3369    <author initials="J." surname="Snell" fullname="J. Snell"/>
3370    <date year="2010" month="March"/>
3371  </front>
3372  <seriesInfo name="RFC" value="5789"/>
3373</reference>
3374
3375</references>
3376
3377<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3378<t>
3379  This document takes over the Status Code Registry, previously defined
3380  in Section 7.1 of <xref target="RFC2817"/>.
3381  (<xref target="status.code.registry"/>)
3382</t>
3383<t>
3384  Clarify definition of POST.
3385  (<xref target="POST"/>)
3386</t>
3387<t>
3388  Remove requirement to handle all Content-* header fields; ban use of
3389  Content-Range with PUT.
3390  (<xref target="PUT"/>)
3391</t>
3392<t>
3393  Take over definition of CONNECT method from <xref target="RFC2817"/>.
3394  (<xref target="CONNECT"/>)
3395</t>
3396<t>
3397  Failed to consider that there are
3398  many other request methods that are safe to automatically redirect,
3399  and further that the user agent is able to make that determination
3400  based on the request method semantics.
3401  (Sections <xref format="counter" target="status.301"/>,
3402  <xref format="counter" target="status.302"/> and
3403  <xref format="counter" target="status.307"/>)
3404</t>
3405<t>
3406  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3407  It used to indicate that the target resource must be accessed through the
3408  proxy given by the Location field. The Location field gave the URI of the
3409  proxy. The recipient was expected to repeat this single request via the proxy.
3410  (<xref target="status.305"/>)
3411</t>
3412<t>
3413  Define status 426 (Upgrade Required) (this was incorporated from
3414  <xref target="RFC2817"/>).
3415  (<xref target="status.426"/>)
3416</t>
3417<t>
3418  Reclassify "Allow" as response header field, removing the option to
3419  specify it in a PUT request.
3420  Relax the server requirement on the contents of the Allow header field and
3421  remove requirement on clients to always trust the header field value.
3422  (<xref target="header.allow"/>)
3423</t>
3424<t>
3425  Correct syntax of Location header field to allow URI references (including
3426  relative references and fragments), as referred symbol "absoluteURI" wasn't
3427  what was expected, and add some clarifications as to when use of fragments
3428  would not be appropriate.
3429  (<xref target="header.location"/>)
3430</t>
3431<t>
3432  Restrict Max-Forwards header field to OPTIONS and TRACE (previously,
3433  extension methods could have used it as well).
3434  (<xref target="header.max-forwards"/>)
3435</t>
3436<t>
3437  Allow Referer field value of "about:blank" as alternative to not specifying it.
3438  (<xref target="header.referer"/>)
3439</t>
3440<t>
3441  In the description of the Server header field, the Via field
3442  was described as a SHOULD. The requirement was and is stated
3443  correctly in the description of the Via header field in Section 9.9 of <xref target="Part1"/>.
3444  (<xref target="header.server"/>)
3445</t>
3446</section>
3447
3448
3449<section title="Collected ABNF" anchor="collected.abnf">
3450<figure>
3451<artwork type="abnf" name="p2-semantics.parsed-abnf"><![CDATA[
3452Allow = "Allow:" OWS Allow-v
3453Allow-v = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3454
3455Expect = "Expect:" OWS Expect-v
3456Expect-v = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3457
3458From = "From:" OWS From-v
3459From-v = mailbox
3460
3461HTTP-date = <HTTP-date, defined in [Part1], Section 6.1>
3462
3463Location = "Location:" OWS Location-v
3464Location-v = URI-reference
3465
3466Max-Forwards = "Max-Forwards:" OWS Max-Forwards-v
3467Max-Forwards-v = 1*DIGIT
3468Method = token
3469
3470OWS = <OWS, defined in [Part1], Section 1.2.2>
3471
3472RWS = <RWS, defined in [Part1], Section 1.2.2>
3473Reason-Phrase = *( WSP / VCHAR / obs-text )
3474Referer = "Referer:" OWS Referer-v
3475Referer-v = absolute-URI / partial-URI
3476Retry-After = "Retry-After:" OWS Retry-After-v
3477Retry-After-v = HTTP-date / delta-seconds
3478
3479Server = "Server:" OWS Server-v
3480Server-v = product *( RWS ( product / comment ) )
3481Status-Code = 3DIGIT
3482
3483URI-reference = <URI-reference, defined in [Part1], Section 2.6>
3484User-Agent = "User-Agent:" OWS User-Agent-v
3485User-Agent-v = product *( RWS ( product / comment ) )
3486
3487absolute-URI = <absolute-URI, defined in [Part1], Section 2.6>
3488
3489comment = <comment, defined in [Part1], Section 3.2>
3490
3491delta-seconds = 1*DIGIT
3492
3493expect-params = ";" token [ "=" ( token / quoted-string ) ]
3494expectation = "100-continue" / expectation-extension
3495expectation-extension = token [ "=" ( token / quoted-string )
3496 *expect-params ]
3497
3498mailbox = <mailbox, defined in [RFC5322], Section 3.4>
3499
3500obs-text = <obs-text, defined in [Part1], Section 1.2.2>
3501
3502partial-URI = <partial-URI, defined in [Part1], Section 2.6>
3503product = <product, defined in [Part1], Section 6.3>
3504
3505quoted-string = <quoted-string, defined in [Part1], Section 1.2.2>
3506
3507token = <token, defined in [Part1], Section 1.2.2>
3508]]></artwork>
3509</figure>
3510<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline"><![CDATA[
3511; Allow defined but not used
3512; Expect defined but not used
3513; From defined but not used
3514; Location defined but not used
3515; Max-Forwards defined but not used
3516; Reason-Phrase defined but not used
3517; Referer defined but not used
3518; Retry-After defined but not used
3519; Server defined but not used
3520; Status-Code defined but not used
3521; User-Agent defined but not used
3522]]></artwork></figure></section>
3523
3524
3525<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3526
3527<section title="Since RFC 2616">
3528<t>
3529  Extracted relevant partitions from <xref target="RFC2616"/>.
3530</t>
3531</section>
3532
3533<section title="Since draft-ietf-httpbis-p2-semantics-00">
3534<t>
3535  Closed issues:
3536  <list style="symbols">
3537    <t>
3538      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3539      "Via is a MUST"
3540      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3541    </t>
3542    <t>
3543      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3544      "Fragments allowed in Location"
3545      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3546    </t>
3547    <t>
3548      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3549      "Safe Methods vs Redirection"
3550      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3551    </t>
3552    <t>
3553      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3554      "Revise description of the POST method"
3555      (<eref target="http://purl.org/NET/http-errata#post"/>)
3556    </t>
3557    <t>
3558      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3559      "Normative and Informative references"
3560    </t>
3561    <t>
3562      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3563      "RFC2606 Compliance"
3564    </t>
3565    <t>
3566      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3567      "Informative references"
3568    </t>
3569    <t>
3570      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3571      "Redundant cross-references"
3572    </t>
3573  </list>
3574</t>
3575<t>
3576  Other changes:
3577  <list style="symbols">
3578    <t>
3579      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3580    </t>
3581  </list>
3582</t>
3583</section>
3584
3585<section title="Since draft-ietf-httpbis-p2-semantics-01">
3586<t>
3587  Closed issues:
3588  <list style="symbols">
3589    <t>
3590      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3591      "PUT side effects"
3592    </t>
3593    <t>
3594      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3595      "Duplicate Host header requirements"
3596    </t>
3597  </list>
3598</t>
3599<t>
3600  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3601  <list style="symbols">
3602    <t>
3603      Move "Product Tokens" section (back) into Part 1, as "token" is used
3604      in the definition of the Upgrade header field.
3605    </t>
3606    <t>
3607      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3608    </t>
3609    <t>
3610      Copy definition of delta-seconds from Part6 instead of referencing it.
3611    </t>
3612  </list>
3613</t>
3614</section>
3615
3616<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3617<t>
3618  Closed issues:
3619  <list style="symbols">
3620    <t>
3621      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3622      "Requiring Allow in 405 responses"
3623    </t>
3624    <t>
3625      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3626      "Status Code Registry"
3627    </t>
3628    <t>
3629      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3630      "Redirection vs. Location"
3631    </t>
3632    <t>
3633      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3634      "Cacheability of 303 response"
3635    </t>
3636    <t>
3637      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3638      "305 Use Proxy"
3639    </t>
3640    <t>
3641      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3642      "Classification for Allow header"
3643    </t>
3644    <t>
3645      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3646      "PUT - 'store under' vs 'store at'"
3647    </t>
3648  </list>
3649</t>
3650<t>
3651  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3652  <list style="symbols">
3653    <t>
3654      Reference RFC 3984, and update header field registrations for headers defined
3655      in this document.
3656    </t>
3657  </list>
3658</t>
3659<t>
3660  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3661  <list style="symbols">
3662    <t>
3663      Replace string literals when the string really is case-sensitive (method).
3664    </t>
3665  </list>
3666</t>
3667</section>
3668
3669<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3670<t>
3671  Closed issues:
3672  <list style="symbols">
3673    <t>
3674      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
3675      "OPTIONS request bodies"
3676    </t>
3677    <t>
3678      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
3679      "Description of CONNECT should refer to RFC2817"
3680    </t>
3681    <t>
3682      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
3683      "Location Content-Location reference request/response mixup"
3684    </t>
3685  </list>
3686</t>
3687<t>
3688  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
3689  <list style="symbols">
3690    <t>
3691      Added initial proposal for registration process, plus initial
3692      content (non-HTTP/1.1 methods to be added by a separate specification).
3693    </t>
3694  </list>
3695</t>
3696</section>
3697
3698<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3699<t>
3700  Closed issues:
3701  <list style="symbols">
3702    <t>
3703      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3704      "Content-*"
3705    </t>
3706    <t>
3707      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3708      "RFC 2822 is updated by RFC 5322"
3709    </t>
3710  </list>
3711</t>
3712<t>
3713  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3714  <list style="symbols">
3715    <t>
3716      Use "/" instead of "|" for alternatives.
3717    </t>
3718    <t>
3719      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3720      whitespace ("OWS") and required whitespace ("RWS").
3721    </t>
3722    <t>
3723      Rewrite ABNFs to spell out whitespace rules, factor out
3724      header field value format definitions.
3725    </t>
3726  </list>
3727</t>
3728</section>
3729
3730<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3731<t>
3732  Closed issues:
3733  <list style="symbols">
3734    <t>
3735      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
3736      "Reason-Phrase BNF"
3737    </t>
3738  </list>
3739</t>
3740<t>
3741  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3742  <list style="symbols">
3743    <t>
3744      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3745    </t>
3746  </list>
3747</t>
3748</section>
3749
3750<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
3751<t>
3752  Closed issues:
3753  <list style="symbols">
3754    <t>
3755      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
3756      "Clarify when Referer is sent"
3757    </t>
3758    <t>
3759      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
3760      "status codes vs methods"
3761    </t>
3762    <t>
3763      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
3764      "Do not require "updates" relation for specs that register status codes or method names"
3765    </t>
3766  </list>
3767</t>
3768</section>
3769
3770<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
3771<t>
3772  Closed issues:
3773  <list style="symbols">
3774    <t>
3775      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
3776      "Idempotency"
3777    </t>
3778    <t>
3779      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
3780      "TRACE security considerations"
3781    </t>
3782    <t>
3783      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
3784      "Clarify rules for determining what entities a response carries"
3785    </t>
3786    <t>
3787      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
3788      "update note citing RFC 1945 and 2068"
3789    </t>
3790    <t>
3791      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
3792      "update note about redirect limit"
3793    </t>
3794    <t>
3795      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
3796      "Location header ABNF should use 'URI'"
3797    </t>
3798    <t>
3799      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
3800      "fragments in Location vs status 303"
3801    </t>
3802    <t>
3803      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
3804      "move IANA registrations for optional status codes"
3805    </t>
3806  </list>
3807</t>
3808<t>
3809  Partly resolved issues:
3810  <list style="symbols">
3811    <t>
3812      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
3813      "Are OPTIONS and TRACE safe?"
3814    </t>
3815  </list>
3816</t>
3817</section>
3818
3819<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
3820<t>
3821  Closed issues:
3822  <list style="symbols">
3823    <t>
3824      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3825      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
3826      status codes when fixing this previously)
3827    </t>
3828  </list>
3829</t>
3830</section>
3831
3832<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
3833<t>
3834  Closed issues:
3835  <list style="symbols">
3836    <t>
3837      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
3838      "Fragment combination / precedence during redirects"
3839    </t>
3840  </list>
3841</t>
3842<t>
3843  Partly resolved issues:
3844  <list style="symbols">
3845    <t>
3846      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
3847      "Location header payload handling"
3848    </t>
3849    <t>
3850      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
3851      "Term for the requested resource's URI"
3852    </t>
3853  </list>
3854</t>
3855</section>
3856
3857<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
3858<t>
3859  Closed issues:
3860  <list style="symbols">
3861    <t>
3862      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
3863      "Clarify 'Requested Variant'"
3864    </t>
3865    <t>
3866      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
3867      "Clarify entity / representation / variant terminology"
3868    </t>
3869    <t>
3870      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/139"/>:
3871      "Methods and Caching"
3872    </t>
3873    <t>
3874      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/190"/>:
3875      "OPTIONS vs Max-Forwards"
3876    </t>
3877    <t>
3878      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/199"/>:
3879      "Status codes and caching"
3880    </t>
3881    <t>
3882      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
3883      "consider removing the 'changes from 2068' sections"
3884    </t>
3885  </list>
3886</t>
3887</section>
3888
3889<section title="Since draft-ietf-httpbis-p2-semantics-11" anchor="changes.since.11">
3890<t>
3891  Closed issues:
3892  <list style="symbols">
3893    <t>
3894      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/229"/>:
3895      "Considerations for new status codes"
3896    </t>
3897    <t>
3898      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/230"/>:
3899      "Considerations for new methods"
3900    </t>
3901    <t>
3902      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/232"/>:
3903      "User-Agent guidelines" (relating to the 'User-Agent' header field)
3904    </t>
3905  </list>
3906</t>
3907</section>
3908
3909<section title="Since draft-ietf-httpbis-p2-semantics-12" anchor="changes.since.12">
3910<t>
3911  Closed issues:
3912  <list style="symbols">
3913    <t>
3914      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
3915      "Fragment combination / precedence during redirects" (added warning
3916      about having a fragid on the redirect may cause inconvenience in
3917      some cases)
3918    </t>
3919    <t>
3920      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/79"/>:
3921      "Content-* vs. PUT"
3922    </t>
3923    <t>
3924      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/88"/>:
3925      "205 Bodies"
3926    </t>
3927    <t>
3928      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/102"/>:
3929      "Understanding Content-* on non-PUT requests"
3930    </t>
3931    <t>
3932      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3933      "Content-*"
3934    </t>
3935    <t>
3936      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/104"/>:
3937      "Header type defaulting"
3938    </t>
3939    <t>
3940      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3941      "PUT - 'store under' vs 'store at'"
3942    </t>
3943    <t>
3944      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/137"/>:
3945      "duplicate ABNF for Reason-Phrase"
3946    </t>
3947    <t>
3948      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/180"/>:
3949      "Note special status of Content-* prefix in header registration procedures"
3950    </t>
3951    <t>
3952      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/203"/>:
3953      "Max-Forwards vs extension methods"
3954    </t>
3955    <t>
3956      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/213"/>:
3957      "What is the value space of HTTP status codes?" (actually fixed in
3958      draft-ietf-httpbis-p2-semantics-11)
3959    </t>
3960    <t>
3961      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/224"/>:
3962      "Header Classification"
3963    </t>
3964    <t>
3965      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/225"/>:
3966      "PUT side effect: invalidation or just stale?"
3967    </t>
3968    <t>
3969      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/226"/>:
3970      "proxies not supporting certain methods"
3971    </t>
3972    <t>
3973      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/239"/>:
3974      "Migrate CONNECT from RFC2817 to p2"
3975    </t>
3976    <t>
3977      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/240"/>:
3978      "Migrate Upgrade details from RFC2817"
3979    </t>
3980    <t>
3981      <eref target="http://trac.tools.ietf.org/wg/httpbis/trac/ticket/267"/>:
3982      "clarify PUT semantics'"
3983    </t>
3984    <t>
3985      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/275"/>:
3986      "duplicate ABNF for 'Method'"
3987    </t>
3988    <t>
3989      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
3990      "untangle ABNFs for header fields"
3991    </t>
3992  </list>
3993</t>
3994</section>
3995
3996</section>
3997
3998</back>
3999</rfc>
Note: See TracBrowser for help on using the repository browser.