source: draft-ietf-httpbis/17/draft-ietf-httpbis-p2-semantics-17.xml @ 1529

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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-17">
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="October" year="2011" day="31"/>
160  <workgroup>HTTPbis Working Group</workgroup>
161
162<abstract>
163<t>
164   The Hypertext Transfer Protocol (HTTP) is an application-level protocol for
165   distributed, collaborative, hypertext information systems. HTTP has been in
166   use by the World Wide Web global information initiative since 1990. This
167   document is Part 2 of the seven-part specification that defines the protocol
168   referred to as "HTTP/1.1" and, taken together, obsoletes RFC 2616.
169</t>
170<t>
171   Part 2 defines the semantics of HTTP messages as expressed by request
172   methods, request header fields, response status codes, and response header
173   fields.
174</t>
175</abstract>
176
177<note title="Editorial Note (To be removed by RFC Editor)">
178  <t>
179    Discussion of this draft should take place on the HTTPBIS working group
180    mailing list (ietf-http-wg@w3.org), which is archived at
181    <eref target="http://lists.w3.org/Archives/Public/ietf-http-wg/"/>.
182  </t>
183  <t>
184    The current issues list is at
185    <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/> and related
186    documents (including fancy diffs) can be found at
187    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
188  </t>
189  <t>
190    The changes in this draft are summarized in <xref target="changes.since.16"/>.
191  </t>
192</note>
193</front>
194<middle>
195<section title="Introduction" anchor="introduction">
196<t>
197   This document defines HTTP/1.1 request and response semantics.  Each HTTP
198   message, as defined in <xref target="Part1"/>, is in the form of either a request or
199   a response.  An HTTP server listens on a connection for HTTP requests and
200   responds to each request, in the order received on that connection, with
201   one or more HTTP response messages.  This document defines the commonly
202   agreed upon semantics of the HTTP uniform interface, the intentions defined
203   by each request method, and the various response messages that might be
204   expected as a result of applying that method to the target resource.
205</t>
206<t>
207   This document is currently disorganized in order to minimize the changes
208   between drafts and enable reviewers to see the smaller errata changes.
209   A future draft will reorganize the sections to better reflect the content.
210   In particular, the sections will be ordered according to the typical
211   processing of an HTTP request message (after message parsing): resource
212   mapping, methods, request modifying header fields, response status,
213   status modifying header fields, and resource metadata.  The current mess
214   reflects how widely dispersed these topics and associated requirements
215   had become in <xref target="RFC2616"/>.
216</t>
217
218<section title="Conformance and Error Handling" anchor="intro.conformance.and.error.handling">
219<t>
220   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
221   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
222   document are to be interpreted as described in <xref target="RFC2119"/>.
223</t>
224<t>
225   This document defines conformance criteria for several roles in HTTP
226   communication, including Senders, Recipients, Clients, Servers, User-Agents,
227   Origin Servers, Intermediaries, Proxies and Gateways. See Section 2 of <xref target="Part1"/>
228   for definitions of these terms.
229</t>
230<t>
231   An implementation is considered conformant if it complies with all of the
232   requirements associated with its role(s). Note that SHOULD-level requirements
233   are relevant here, unless one of the documented exceptions is applicable.
234</t>
235<t>
236   This document also uses ABNF to define valid protocol elements
237   (<xref target="notation"/>). In addition to the prose requirements placed
238   upon them, Senders MUST NOT generate protocol elements that are invalid.
239</t>
240<t>
241   Unless noted otherwise, Recipients MAY take steps to recover a usable
242   protocol element from an invalid construct. However, HTTP does not define
243   specific error handling mechanisms, except in cases where it has direct
244   impact on security. This is because different uses of the protocol require
245   different error handling strategies; for example, a Web browser may wish to
246   transparently recover from a response where the Location header field
247   doesn't parse according to the ABNF, whereby in a systems control protocol
248   using HTTP, this type of error recovery could lead to dangerous consequences.
249</t>
250</section>
251
252<section title="Syntax Notation" anchor="notation">
253 
254 
255 
256 
257 
258 
259<t>
260  This specification uses the ABNF syntax defined in Section 1.2 of <xref target="Part1"/> (which
261  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
262  <xref target="collected.abnf"/> shows the collected ABNF, with the list
263  rule expanded.
264</t>
265<t>
266  The following core rules are included by
267  reference, as defined in <xref target="RFC5234"/>, Appendix B.1:
268  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
269  DIGIT (decimal 0-9), DQUOTE (double quote),
270  HEXDIG (hexadecimal 0-9/A-F/a-f), HTAB (horizontal tab), LF (line feed),
271  OCTET (any 8-bit sequence of data), SP (space), and
272  VCHAR (any visible US-ASCII character).
273</t>
274
275<section title="Core Rules" anchor="core.rules">
276 
277 
278 
279 
280 
281<t>
282  The core rules below are defined in <xref target="Part1"/>:
283</t>
284<figure><artwork type="abnf2616"><![CDATA[
285  OWS           = <OWS, defined in [Part1], Section 1.2.2>
286  RWS           = <RWS, defined in [Part1], Section 1.2.2>
287  obs-text      = <obs-text, defined in [Part1], Section 1.2.2>
288  quoted-string = <quoted-string, defined in [Part1], Section 3.2.3>
289  token         = <token, defined in [Part1], Section 3.2.3>
290]]></artwork></figure>
291</section>
292
293<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
294 
295 
296 
297 
298 
299<t>
300  The ABNF rules below are defined in other parts:
301</t>
302<figure><artwork type="abnf2616"><![CDATA[
303  absolute-URI  = <absolute-URI, defined in [Part1], Section 2.7>
304  comment       = <comment, defined in [Part1], Section 3.2>
305  partial-URI   = <partial-URI, defined in [Part1], Section 2.7>
306  product       = <product, defined in [Part1], Section 5.2>
307  URI-reference = <URI-reference, defined in [Part1], Section 2.7>
308]]></artwork></figure>
309</section>
310</section>
311</section>
312
313<section title="Method" anchor="method">
314 
315 
316<t>
317   The Method token indicates the request method to be performed on the target
318   resource (Section 4.3 of <xref target="Part1"/>). The method is case-sensitive.
319</t>
320<figure><iref primary="true" item="Grammar" subitem="Method"/><artwork type="abnf2616"><![CDATA[
321  Method         = token
322]]></artwork></figure>
323<t>
324   The list of methods allowed by a resource can be specified in an
325   Allow header field (<xref target="header.allow"/>). The status code of the response
326   always notifies the client whether a method is currently allowed on a
327   resource, since the set of allowed methods can change dynamically. An
328   origin server SHOULD respond with the status code 405 (Method Not Allowed)
329   if the method is known by the origin server but not allowed for the
330   resource, and 501 (Not Implemented) if the method is
331   unrecognized or not implemented by the origin server. The methods GET
332   and HEAD MUST be supported by all general-purpose servers. All other
333   methods are OPTIONAL; however, if the above methods are implemented,
334   they MUST be implemented with the same semantics as those specified
335   in <xref target="method.definitions"/>.
336</t>
337
338<section title="Overview of Methods" anchor="overview.of.methods">
339<t>
340  The methods listed below are defined in <xref target="method.definitions"/>.
341</t>
342<texttable align="left">
343  <ttcol>Method Name</ttcol><ttcol>Defined in...</ttcol>
344 
345  <c>OPTIONS</c> <c><xref target="OPTIONS"/></c>
346  <c>GET</c> <c><xref target="GET"/></c>
347  <c>HEAD</c> <c><xref target="HEAD"/></c>
348  <c>POST</c> <c><xref target="POST"/></c>
349  <c>PUT</c> <c><xref target="PUT"/></c>
350  <c>DELETE</c> <c><xref target="DELETE"/></c>
351  <c>TRACE</c> <c><xref target="TRACE"/></c>
352  <c>CONNECT</c> <c><xref target="CONNECT"/></c>
353</texttable>
354<t>
355  Note that this list is not exhaustive — it does not include request methods defined
356  in other specifications.
357</t>
358</section>
359
360<section title="Method Registry" anchor="method.registry">
361<t>
362  The HTTP Method Registry defines the name space for the Method token in the
363  Request line of an HTTP request.
364</t>
365<t>
366  Registrations MUST include the following fields:
367  <list style="symbols">
368    <t>Method Name (see <xref target="method"/>)</t>
369    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
370    <t>Pointer to specification text</t>
371  </list>
372</t>
373<t>
374  Values to be added to this name space are subject to IETF review
375  (<xref target="RFC5226"/>, Section 4.1).
376</t>
377<t>
378  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
379</t>
380
381<section title="Considerations for New Methods" anchor="considerations.for.new.methods">
382<t>
383   When it is necessary to express new semantics for a HTTP request that
384   aren't specific to a single application or media type, and currently defined
385   methods are inadequate, it may be appropriate to register a new method.
386</t>
387<t>
388   HTTP methods are generic; that is, they are potentially applicable to any
389   resource, not just one particular media type, "type" of resource, or
390   application. As such, it is preferred that new HTTP methods be registered
391   in a document that isn't specific to a single application, so that this is
392   clear.
393</t>
394<t>
395   Due to the parsing rules defined in Section 3.3 of <xref target="Part1"/>, definitions of HTTP
396   methods cannot prohibit the presence of a message-body on either the request
397   or the response message (with responses to HEAD requests being the single
398   exception). Definitions of new methods cannot change this rule, but they can
399   specify that only zero-length bodies (as opposed to absent bodies) are allowed.
400</t>
401<t>
402   New method definitions need to indicate whether they are safe (<xref target="safe.methods"/>), what semantics (if any) the request body has,
403   and whether they are idempotent (<xref target="idempotent.methods"/>).
404   They also need to state whether they can be cached (<xref target="Part6"/>); in
405   particular what conditions a cache may store the response, and under what
406   conditions such a stored response may be used to satisfy a subsequent
407   request.
408</t>
409</section>
410
411</section>
412</section>
413
414<section title="Header Fields" anchor="header.fields">
415<t>
416   Header fields are key value pairs that can be used to communicate data about
417   the message, its payload, the target resource, or about the connection
418   itself (i.e., control data).  See Section 3.2 of <xref target="Part1"/> for a general definition
419   of their syntax.
420</t>
421
422<section title="Considerations for Creating Header Fields" anchor="considerations.for.creating.header.fields">
423<t>
424   New header fields are registered using the procedures described in
425   <xref target="RFC3864"/>.
426</t>
427<t>
428   The requirements for header field names are defined in
429   Section 4.1 of <xref target="RFC3864"/>.  Authors of specifications
430   defining new fields are advised to keep the name as short as practical, and
431   not to prefix them with "X-" if they are to be registered (either
432   immediately or in the future).
433</t>
434<t>
435   New header field values typically have their syntax defined using ABNF
436   (<xref target="RFC5234"/>), using the extensions defined in Section 1.2.1 of <xref target="Part1"/>
437   as necessary, and are usually constrained to the range of ASCII characters.
438   Header fields needing a greater range of characters can use an encoding
439   such as the one defined in <xref target="RFC5987"/>.
440</t>
441<t>
442   Because commas (",") are used as a generic delimiter between field-values,
443   they need to be treated with care if they are allowed in the field-value's
444   payload. Typically, components that might contain a comma are protected with
445   double-quotes using the quoted-string ABNF production (Section 3.2.3 of <xref target="Part1"/>).
446</t>
447<t>
448   For example, a textual date and a URI (either of which might contain a comma)
449   could be safely carried in field-values like these:
450</t>
451<figure><artwork type="example"><![CDATA[
452  Example-URI-Field: "http://example.com/a.html,foo",
453                     "http://without-a-comma.example.com/"
454  Example-Date-Field: "Sat, 04 May 1996", "Wed, 14 Sep 2005"
455]]></artwork></figure>
456<t>
457   Many header fields use a format including (case-insensitively) named
458   parameters (for instance, Content-Type, defined in Section 6.8 of <xref target="Part3"/>).
459   Allowing both unquoted (token) and quoted (quoted-string) syntax for the
460   parameter value enables recipients to use existing parser components. When
461   allowing both forms, the meaning of a parameter value ought to be
462   independent of the syntax used for it (for an example, see the notes on
463   parameter handling for media types in Section 2.3 of <xref target="Part3"/>).
464</t>
465<t>
466   Authors of specifications defining new header fields are advised to consider
467   documenting:
468  <list style="symbols">
469    <t>Whether the field is a single value, or whether it can be a list
470      (delimited by commas; see Section 3.2 of <xref target="Part1"/>).<vspace blankLines="1"/>If it does not use the list syntax, document how to treat messages
471      where the header field occurs multiple times (a sensible default would
472      be to ignore the header field, but this might not always be the right
473      choice).<vspace blankLines="1"/>Note that intermediaries and software libraries might combine
474      multiple header field instances into a single one, despite the header
475      field not allowing this. A robust format enables recipients to discover
476      these situations (good example: "Content-Type", as the comma can only
477      appear inside quoted strings; bad example: "Location", as a comma can
478      occur inside a URI).</t>
479    <t>Under what conditions the header field can be used; e.g., only in
480    responses or requests, in all messages, only on responses to a particular
481    request method.</t>
482    <t>Whether it is appropriate to list the field-name in the Connection header
483    (i.e., if the header is to be hop-by-hop, see Section 8.1 of <xref target="Part1"/>).</t>
484    <t>Under what conditions intermediaries are allowed to modify the header
485    field's value, insert or delete it.</t>
486    <t>How the header might interact with caching (see <xref target="Part6"/>).</t>
487    <t>Whether the header field is useful or allowable in trailers (see
488    Section 5.1.1 of <xref target="Part1"/>).</t>
489    <t>Whether the header field should be preserved across redirects.</t>
490  </list>
491</t>
492</section>
493
494<section title="Request Header Fields" anchor="request.header.fields">
495 
496<t>
497   The request header fields allow the client to pass additional
498   information about the request, and about the client itself, to the
499   server. These fields act as request modifiers, with semantics
500   equivalent to the parameters on a programming language method
501   invocation.
502</t>
503<texttable align="left">
504  <ttcol>Header Field Name</ttcol>
505  <ttcol>Defined in...</ttcol>
506
507  <c>Accept</c> <c>Section 6.1 of <xref target="Part3"/></c>
508  <c>Accept-Charset</c> <c>Section 6.2 of <xref target="Part3"/></c>
509  <c>Accept-Encoding</c> <c>Section 6.3 of <xref target="Part3"/></c>
510  <c>Accept-Language</c> <c>Section 6.4 of <xref target="Part3"/></c>
511  <c>Authorization</c> <c>Section 4.1 of <xref target="Part7"/></c>
512  <c>Expect</c> <c><xref target="header.expect"/></c>
513  <c>From</c> <c><xref target="header.from"/></c>
514  <c>Host</c> <c>Section 8.3 of <xref target="Part1"/></c>
515  <c>If-Match</c> <c>Section 3.1 of <xref target="Part4"/></c>
516  <c>If-Modified-Since</c> <c>Section 3.3 of <xref target="Part4"/></c>
517  <c>If-None-Match</c> <c>Section 3.2 of <xref target="Part4"/></c>
518  <c>If-Range</c> <c>Section 5.3 of <xref target="Part5"/></c>
519  <c>If-Unmodified-Since</c> <c>Section 3.4 of <xref target="Part4"/></c>
520  <c>Max-Forwards</c> <c><xref target="header.max-forwards"/></c>
521  <c>Proxy-Authorization</c> <c>Section 4.3 of <xref target="Part7"/></c>
522  <c>Range</c> <c>Section 5.4 of <xref target="Part5"/></c>
523  <c>Referer</c> <c><xref target="header.referer"/></c>
524  <c>TE</c> <c>Section 8.4 of <xref target="Part1"/></c>
525  <c>User-Agent</c> <c><xref target="header.user-agent"/></c>
526</texttable>
527</section>
528
529<section title="Response Header Fields" anchor="response.header.fields">
530 
531<t>
532   The response header fields allow the server to pass additional
533   information about the response which cannot be placed in the Status-Line.
534   These header fields give information about the server and about
535   further access to the target resource (Section 4.3 of <xref target="Part1"/>).
536</t>
537<texttable align="left">
538  <ttcol>Header Field Name</ttcol><ttcol>Defined in...</ttcol>
539
540  <c>Accept-Ranges</c> <c>Section 5.1 of <xref target="Part5"/></c>
541  <c>Age</c> <c>Section 3.1 of <xref target="Part6"/></c>
542  <c>Allow</c> <c><xref target="header.allow"/></c>
543  <c>Date</c> <c><xref target="header.date"/></c>
544  <c>ETag</c> <c>Section 2.3 of <xref target="Part4"/></c>
545  <c>Location</c> <c><xref target="header.location"/></c>
546  <c>Proxy-Authenticate</c> <c>Section 4.2 of <xref target="Part7"/></c>
547  <c>Retry-After</c> <c><xref target="header.retry-after"/></c>
548  <c>Server</c> <c><xref target="header.server"/></c>
549  <c>Vary</c> <c>Section 3.5 of <xref target="Part6"/></c>
550  <c>WWW-Authenticate</c> <c>Section 4.4 of <xref target="Part7"/></c>
551</texttable>
552</section>
553
554</section>
555
556<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
557 
558 
559 
560<t>
561   The Status-Code element is a 3-digit integer result code of the attempt to
562   understand and satisfy the request.
563</t>
564<t>
565   The Reason-Phrase is intended to give a short textual description of the
566   Status-Code and is intended for a human user. The client does not need
567   to examine or display the Reason-Phrase.
568</t>
569<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[
570  Status-Code    = 3DIGIT
571  Reason-Phrase  = *( HTAB / SP / VCHAR / obs-text )
572]]></artwork></figure>
573<t>
574   HTTP status codes are extensible. HTTP applications are not required
575   to understand the meaning of all registered status codes, though such
576   understanding is obviously desirable. However, applications MUST
577   understand the class of any status code, as indicated by the first
578   digit, and treat any unrecognized response as being equivalent to the
579   x00 status code of that class, with the exception that an
580   unrecognized response MUST NOT be cached. For example, if an
581   unrecognized status code of 431 is received by the client, it can
582   safely assume that there was something wrong with its request and
583   treat the response as if it had received a 400 status code. In such
584   cases, user agents SHOULD present to the user the representation enclosed
585   with the response, since that representation is likely to include human-readable
586   information which will explain the unusual status.
587</t>
588
589<section title="Overview of Status Codes" anchor="overview.of.status.codes">
590<t> 
591   The status codes listed below are defined in <xref target="status.codes"/>
592   of this specification, Section 4 of <xref target="Part4"/>, Section 3 of <xref target="Part5"/>, and Section 3 of <xref target="Part7"/>.
593   The reason phrases listed here are only recommendations — they can be
594   replaced by local equivalents without affecting the protocol.
595</t>
596<texttable align="left">
597  <ttcol>Status-Code</ttcol>
598  <ttcol>Reason-Phrase</ttcol>
599  <ttcol>Defined in...</ttcol>
600 
601  <c>100</c> <c>Continue</c> <c><xref target="status.100"/></c>
602  <c>101</c> <c>Switching Protocols</c> <c><xref target="status.101"/></c>
603
604  <c>200</c> <c>OK</c> <c><xref target="status.200"/></c>
605  <c>201</c> <c>Created</c> <c><xref target="status.201"/></c>
606  <c>202</c> <c>Accepted</c> <c><xref target="status.202"/></c>
607  <c>203</c> <c>Non-Authoritative Information</c> <c><xref target="status.203"/></c>
608  <c>204</c> <c>No Content</c> <c><xref target="status.204"/></c>
609  <c>205</c> <c>Reset Content</c> <c><xref target="status.205"/></c>
610  <c>206</c> <c>Partial Content</c> <c>Section 3.1 of <xref target="Part5"/></c>
611
612  <c>300</c> <c>Multiple Choices</c> <c><xref target="status.300"/></c>
613  <c>301</c> <c>Moved Permanently</c> <c><xref target="status.301"/></c>
614  <c>302</c> <c>Found</c> <c><xref target="status.302"/></c>
615  <c>303</c> <c>See Other</c> <c><xref target="status.303"/></c>
616  <c>304</c> <c>Not Modified</c> <c>Section 4.1 of <xref target="Part4"/></c>
617  <c>305</c> <c>Use Proxy</c> <c><xref target="status.305"/></c>
618  <c>307</c> <c>Temporary Redirect</c> <c><xref target="status.307"/></c>
619
620  <c>400</c> <c>Bad Request</c> <c><xref target="status.400"/></c>
621  <c>401</c> <c>Unauthorized</c> <c>Section 3.1 of <xref target="Part7"/></c>
622  <c>402</c> <c>Payment Required</c> <c><xref target="status.402"/></c>
623  <c>403</c> <c>Forbidden</c> <c><xref target="status.403"/></c>
624  <c>404</c> <c>Not Found</c> <c><xref target="status.404"/></c>
625  <c>405</c> <c>Method Not Allowed</c> <c><xref target="status.405"/></c>
626  <c>406</c> <c>Not Acceptable</c> <c><xref target="status.406"/></c>
627  <c>407</c> <c>Proxy Authentication Required</c> <c>Section 3.2 of <xref target="Part7"/></c>
628  <c>408</c> <c>Request Time-out</c> <c><xref target="status.408"/></c>
629  <c>409</c> <c>Conflict</c> <c><xref target="status.409"/></c>
630  <c>410</c> <c>Gone</c> <c><xref target="status.410"/></c>
631  <c>411</c> <c>Length Required</c> <c><xref target="status.411"/></c>
632  <c>412</c> <c>Precondition Failed</c> <c>Section 4.2 of <xref target="Part4"/></c>
633  <c>413</c> <c>Request Representation Too Large</c> <c><xref target="status.413"/></c>
634  <c>414</c> <c>URI Too Long</c> <c><xref target="status.414"/></c>
635  <c>415</c> <c>Unsupported Media Type</c> <c><xref target="status.415"/></c>
636  <c>416</c> <c>Requested range not satisfiable</c> <c>Section 3.2 of <xref target="Part5"/></c>
637  <c>417</c> <c>Expectation Failed</c> <c><xref target="status.417"/></c>
638  <c>426</c> <c>Upgrade Required</c> <c><xref target="status.426"/></c>
639
640  <c>500</c> <c>Internal Server Error</c> <c><xref target="status.500"/></c>
641  <c>501</c> <c>Not Implemented</c> <c><xref target="status.501"/></c>
642  <c>502</c> <c>Bad Gateway</c> <c><xref target="status.502"/></c>
643  <c>503</c> <c>Service Unavailable</c> <c><xref target="status.503"/></c>
644  <c>504</c> <c>Gateway Time-out</c> <c><xref target="status.504"/></c>
645  <c>505</c> <c>HTTP Version not supported</c> <c><xref target="status.505"/></c>
646</texttable>
647<t>
648   Note that this list is not exhaustive — it does not include
649   extension status codes defined in other specifications.
650</t>
651</section>
652
653<section title="Status Code Registry" anchor="status.code.registry">
654<t>
655  The HTTP Status Code Registry defines the name space for the Status-Code
656  token in the Status-Line of an HTTP response.
657</t>
658<t>
659  Values to be added to this name space are subject to IETF review
660  (<xref target="RFC5226"/>, Section 4.1).
661</t>
662<t>
663  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
664</t>
665
666<section title="Considerations for New Status Codes" anchor="considerations.for.new.status.codes">
667<t>
668   When it is necessary to express new semantics for a HTTP response that
669   aren't specific to a single application or media type, and currently defined
670   status codes are inadequate, a new status code can be registered.
671</t>
672<t>
673   HTTP status codes are generic; that is, they are potentially applicable to
674   any resource, not just one particular media type, "type" of resource, or
675   application. As such, it is preferred that new HTTP status codes be
676   registered in a document that isn't specific to a single application, so
677   that this is clear.
678</t>
679<t>
680   Definitions of new HTTP status codes typically explain the request
681   conditions that produce a response containing the status code (e.g.,
682   combinations of request headers and/or method(s)), along with any
683   interactions with response headers (e.g., those that are required, those
684   that modify the semantics of the response).
685</t>
686<t>
687   New HTTP status codes are required to fall under one of the categories
688   defined in <xref target="status.codes"/>. To allow existing parsers to
689   properly handle them, new status codes cannot disallow a response body,
690   although they can mandate a zero-length response body. They can require the
691   presence of one or more particular HTTP response header(s).
692</t>
693<t>
694   Likewise, their definitions can specify that caches are allowed to use
695   heuristics to determine their freshness (see <xref target="Part6"/>; by default, it is
696   not allowed), and can define how to determine the resource which they
697   carry a representation for (see <xref target="identifying.response.associated.with.representation"/>; by default,
698   it is anonymous).
699</t>
700</section>
701
702</section>
703
704</section>
705
706<section title="Representation" anchor="representation">
707<t>
708   Request and Response messages MAY transfer a representation if not otherwise
709   restricted by the request method or response status code. A representation
710   consists of metadata (representation header fields) and data (representation
711   body).  When a complete or partial representation is enclosed in an HTTP message,
712   it is referred to as the payload of the message. HTTP representations
713   are defined in <xref target="Part3"/>.
714</t>
715<t>
716   A representation body is only present in a message when a message-body is
717   present, as described in Section 3.3 of <xref target="Part1"/>. The representation body is obtained
718   from the message-body by decoding any Transfer-Encoding that might
719   have been applied to ensure safe and proper transfer of the message.
720</t>
721
722<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
723<t>
724   It is sometimes necessary to determine an identifier for the resource
725   associated with a representation.
726</t>
727<t>
728   An HTTP request representation, when present, is always associated with an
729   anonymous (i.e., unidentified) resource.
730</t>
731<t>
732   In the common case, an HTTP response is a representation of the target
733   resource (see Section 4.3 of <xref target="Part1"/>). However, this is not always the
734   case. To determine the URI of the resource a response is associated with,
735   the following rules are used (with the first applicable one being selected):
736</t>
737<t><list style="numbers">
738   <t>If the response status code is 200 or 203 and the request method was GET,
739   the response payload is a representation of the target resource.</t>
740   <t>If the response status code is 204, 206, or 304 and the request method was GET
741   or HEAD, the response payload is a partial representation of the target
742   resource.</t>
743   <t>If the response has a Content-Location header field, and that URI is the same
744   as the effective request URI, the response payload is a representation of the
745   target resource.</t>
746   <t>If the response has a Content-Location header field, and that URI is not the
747   same as the effective request URI, then the response asserts that its
748   payload is a representation of the resource identified by the
749   Content-Location URI. However, such an assertion cannot be trusted unless
750   it can be verified by other means (not defined by HTTP).</t>
751   <t>Otherwise, the response is a representation of an anonymous (i.e.,
752   unidentified) resource.</t>
753</list></t>
754<t>
755  <cref anchor="TODO-req-uri">
756   The comparison function is going to have to be defined somewhere,
757   because we already need to compare URIs for things like cache invalidation.</cref>
758</t>
759</section>
760
761</section>
762
763
764<section title="Method Definitions" anchor="method.definitions">
765<t>
766   The set of common request methods for HTTP/1.1 is defined below. Although
767   this set can be expanded, additional methods cannot be assumed to
768   share the same semantics for separately extended clients and servers.
769</t>
770
771<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
772
773<section title="Safe Methods" anchor="safe.methods">
774<iref item="Safe Methods" primary="true"/>
775<t>
776   Implementors need to be aware that the software represents the user in
777   their interactions over the Internet, and need to allow
778   the user to be aware of any actions they take which might have an
779   unexpected significance to themselves or others.
780</t>
781<t>
782   In particular, the convention has been established that the GET, HEAD,
783   OPTIONS, and TRACE request methods SHOULD NOT have the significance
784   of taking an action other than retrieval. These request methods ought
785   to be considered "safe".
786   This allows user agents to represent other methods, such as POST, PUT
787   and DELETE, in a special way, so that the user is made aware of the
788   fact that a possibly unsafe action is being requested.
789</t>
790<t>
791   Naturally, it is not possible to ensure that the server does not
792   generate side-effects as a result of performing a GET request; in
793   fact, some dynamic resources consider that a feature. The important
794   distinction here is that the user did not request the side-effects,
795   so therefore cannot be held accountable for them.
796</t>
797</section>
798
799<section title="Idempotent Methods" anchor="idempotent.methods">
800<iref item="Idempotent Methods" primary="true"/>
801<t>
802   Request methods can also have the property of "idempotence" in that,
803   aside from error or expiration issues, the intended effect of multiple
804   identical requests is the same as for a single request.
805   PUT, DELETE, and all safe request methods are idempotent.
806   It is important to note that idempotence refers only to changes
807   requested by the client: a server is free to change its state due
808   to multiple requests for the purpose of tracking those requests,
809   versioning of results, etc.
810</t>
811</section>
812</section>
813
814<section title="OPTIONS" anchor="OPTIONS">
815 
816  <iref primary="true" item="OPTIONS method"/>
817  <iref primary="true" item="Methods" subitem="OPTIONS"/>
818<t>
819   The OPTIONS method requests information about the
820   communication options available on the request/response chain
821   identified by the effective request URI. This method allows a client to
822   determine the options and/or requirements associated with a resource,
823   or the capabilities of a server, without implying a resource action
824   or initiating a resource retrieval.
825</t>
826<t>
827   Responses to the OPTIONS method are not cacheable.
828</t>
829<t>
830   If the OPTIONS request includes a message-body (as indicated by the
831   presence of Content-Length or Transfer-Encoding), then the media type
832   MUST be indicated by a Content-Type field. Although this
833   specification does not define any use for such a body, future
834   extensions to HTTP might use the OPTIONS body to make more detailed
835   queries on the server.
836</t>
837<t>
838   If the request-target is an asterisk ("*"), the OPTIONS request is
839   intended to apply to the server in general rather than to a specific
840   resource. Since a server's communication options typically depend on
841   the resource, the "*" request is only useful as a "ping" or "no-op"
842   type of method; it does nothing beyond allowing the client to test
843   the capabilities of the server. For example, this can be used to test
844   a proxy for HTTP/1.1 compliance (or lack thereof).
845</t>
846<t>
847   If the request-target is not an asterisk, the OPTIONS request applies
848   only to the options that are available when communicating with that
849   resource.
850</t>
851<t>
852   A 200 response SHOULD include any header fields that indicate
853   optional features implemented by the server and applicable to that
854   resource (e.g., Allow), possibly including extensions not defined by
855   this specification. The response body, if any, SHOULD also include
856   information about the communication options. The format for such a
857   body is not defined by this specification, but might be defined by
858   future extensions to HTTP. Content negotiation MAY be used to select
859   the appropriate response format. If no response body is included, the
860   response MUST include a Content-Length field with a field-value of
861   "0".
862</t>
863<t>
864   The Max-Forwards header field MAY be used to target a
865   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
866   If no Max-Forwards field is present in the request, then the forwarded
867   request MUST NOT include a Max-Forwards field.
868</t>
869</section>
870
871<section title="GET" anchor="GET">
872 
873  <iref primary="true" item="GET method"/>
874  <iref primary="true" item="Methods" subitem="GET"/>
875<t>
876   The GET method requests transfer of a current representation of
877   the target resource.
878</t>
879<t>   
880   If the target resource is a data-producing process, it is the
881   produced data which shall be returned as the representation in the response and not
882   the source text of the process, unless that text happens to be the output of
883   the process.
884</t>
885<t>
886   The semantics of the GET method change to a "conditional GET" if the
887   request message includes an If-Modified-Since, If-Unmodified-Since,
888   If-Match, If-None-Match, or If-Range header field. A conditional GET
889   requests that the representation be transferred only under the
890   circumstances described by the conditional header field(s). The
891   conditional GET request is intended to reduce unnecessary network
892   usage by allowing cached representations to be refreshed without requiring
893   multiple requests or transferring data already held by the client.
894</t>
895<t>
896   The semantics of the GET method change to a "partial GET" if the
897   request message includes a Range header field. A partial GET requests
898   that only part of the representation be transferred, as described in Section 5.4 of <xref target="Part5"/>.
899   The partial GET request is intended to reduce unnecessary
900   network usage by allowing partially-retrieved representations to be
901   completed without transferring data already held by the client.
902</t>
903<t>
904   Bodies on GET requests have no defined semantics. Note that sending a body
905   on a GET request might cause some existing implementations to reject the
906   request.
907</t>
908<t>
909   The response to a GET request is cacheable and MAY be used to satisfy
910   subsequent GET and HEAD requests (see <xref target="Part6"/>).
911</t>
912<t>
913   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
914</t>
915</section>
916
917<section title="HEAD" anchor="HEAD">
918 
919  <iref primary="true" item="HEAD method"/>
920  <iref primary="true" item="Methods" subitem="HEAD"/>
921<t>
922   The HEAD method is identical to GET except that the server MUST NOT
923   return a message-body in the response. The metadata contained
924   in the HTTP header fields in response to a HEAD request SHOULD be identical
925   to the information sent in response to a GET request. This method can
926   be used for obtaining metadata about the representation implied by the
927   request without transferring the representation body. This method is
928   often used for testing hypertext links for validity, accessibility,
929   and recent modification.
930</t>
931<t>
932   The response to a HEAD request is cacheable and MAY be used to satisfy
933   a subsequent HEAD request; see <xref target="Part6"/>. It also MAY be used to update a previously cached
934   representation from that resource; if the new field values
935   indicate that the cached representation differs from the current representation (as
936   would be indicated by a change in Content-Length, ETag
937   or Last-Modified), then the cache MUST treat the cache entry as
938   stale.
939</t>
940<t>
941   Bodies on HEAD requests have no defined semantics. Note that sending a body
942   on a HEAD request might cause some existing implementations to reject the
943   request.
944</t>
945</section>
946
947<section title="POST" anchor="POST">
948  <iref primary="true" item="POST method"/>
949  <iref primary="true" item="Methods" subitem="POST"/>
950<t>
951   The POST method requests that the origin server accept the
952   representation enclosed in the request as data to be processed by the
953   target resource. POST is designed to allow a uniform method to cover the
954   following functions:
955  <list style="symbols">
956    <t>
957      Annotation of existing resources;
958    </t>
959    <t>
960        Posting a message to a bulletin board, newsgroup, mailing list,
961        or similar group of articles;
962    </t>
963    <t>
964        Providing a block of data, such as the result of submitting a
965        form, to a data-handling process;
966    </t>
967    <t>
968        Extending a database through an append operation.
969    </t>
970  </list>
971</t>
972<t>
973   The actual function performed by the POST method is determined by the
974   server and is usually dependent on the effective request URI.
975</t>
976<t>
977   The action performed by the POST method might not result in a
978   resource that can be identified by a URI. In this case, either 200
979   (OK) or 204 (No Content) is the appropriate response status code,
980   depending on whether or not the response includes a representation that
981   describes the result.
982</t>
983<t>
984   If a resource has been created on the origin server, the response
985   SHOULD be 201 (Created) and contain a representation which describes the
986   status of the request and refers to the new resource, and a Location
987   header field (see <xref target="header.location"/>).
988</t>
989<t>
990   Responses to POST requests are only cacheable when they
991   include explicit freshness information (see Section 2.3.1 of <xref target="Part6"/>). A
992   cached POST response with a Content-Location header field
993   (see Section 6.7 of <xref target="Part3"/>) whose value is the effective
994   Request URI MAY be used to satisfy subsequent GET and HEAD requests.
995</t>
996<t>
997   Note that POST caching is not widely implemented.
998   However, the 303 (See Other) response can be used to direct the
999   user agent to retrieve a cacheable resource.
1000</t>
1001</section>
1002
1003<section title="PUT" anchor="PUT">
1004  <iref primary="true" item="PUT method"/>
1005  <iref primary="true" item="Methods" subitem="PUT"/>
1006<t>
1007   The PUT method requests that the state of the target resource
1008   be created or replaced with the state defined by the representation
1009   enclosed in the request message payload.  A successful PUT of a given
1010   representation would suggest that a subsequent GET on that same target
1011   resource will result in an equivalent representation being returned in
1012   a 200 (OK) response.  However, there is no guarantee that such a state
1013   change will be observable, since the target resource might be acted
1014   upon by other user agents in parallel, or might be subject to dynamic
1015   processing by the origin server, before any subsequent GET is received.
1016   A successful response only implies that the user agent's intent was
1017   achieved at the time of its processing by the origin server.
1018</t>
1019<t>   
1020   If the target resource does not have a current representation and
1021   the PUT successfully creates one, then the origin server MUST inform
1022   the user agent by sending a 201 (Created) response.  If the target
1023   resource does have a current representation and that representation is
1024   successfully modified in accordance with the state of the enclosed
1025   representation, then either a 200 (OK) or 204 (No Content) response
1026   SHOULD be sent to indicate successful completion of the request.
1027</t>
1028<t>
1029   Unrecognized header fields SHOULD be ignored (i.e., not saved
1030   as part of the resource state).
1031</t>
1032<t>
1033   An origin server SHOULD verify that the PUT representation is
1034   consistent with any constraints which the server has for the target
1035   resource that cannot or will not be changed by the PUT.  This is
1036   particularly important when the origin server uses internal
1037   configuration information related to the URI in order to set the
1038   values for representation metadata on GET responses.  When a PUT
1039   representation is inconsistent with the target resource, the origin
1040   server SHOULD either make them consistent, by transforming the
1041   representation or changing the resource configuration, or respond
1042   with an appropriate error message containing sufficient information
1043   to explain why the representation is unsuitable.  The 409 (Conflict)
1044   or 415 (Unsupported Media Type) status codes are suggested, with the
1045   latter being specific to constraints on Content-Type values.
1046</t>
1047<t>
1048   For example, if the target resource is configured to always have a
1049   Content-Type of "text/html" and the representation being PUT has a
1050   Content-Type of "image/jpeg", then the origin server SHOULD do one of:
1051   (a) reconfigure the target resource to reflect the new media type;
1052   (b) transform the PUT representation to a format consistent with that
1053   of the resource before saving it as the new resource state; or,
1054   (c) reject the request with a 415 response indicating that the target
1055   resource is limited to "text/html", perhaps including a link to a
1056   different resource that would be a suitable target for the new
1057   representation.
1058</t>
1059<t>
1060   HTTP does not define exactly how a PUT method affects the state
1061   of an origin server beyond what can be expressed by the intent of
1062   the user agent request and the semantics of the origin server response.
1063   It does not define what a resource might be, in any sense of that
1064   word, beyond the interface provided via HTTP.  It does not define
1065   how resource state is "stored", nor how such storage might change
1066   as a result of a change in resource state, nor how the origin server
1067   translates resource state into representations.  Generally speaking,
1068   all implementation details behind the resource interface are
1069   intentionally hidden by the server.
1070</t>
1071<t>
1072   The fundamental difference between the POST and PUT methods is
1073   highlighted by the different intent for the target resource.
1074   The target resource in a POST request is intended to handle the
1075   enclosed representation as a data-accepting process, such as for
1076   a gateway to some other protocol or a document that accepts annotations.
1077   In contrast, the target resource in a PUT request is intended to
1078   take the enclosed representation as a new or replacement value.
1079   Hence, the intent of PUT is idempotent and visible to intermediaries,
1080   even though the exact effect is only known by the origin server.
1081</t>
1082<t>
1083   Proper interpretation of a PUT request presumes that the user agent
1084   knows what target resource is desired.  A service that is intended
1085   to select a proper URI on behalf of the client, after receiving
1086   a state-changing request, SHOULD be implemented using the POST
1087   method rather than PUT.  If the origin server will not make the
1088   requested PUT state change to the target resource and instead
1089   wishes to have it applied to a different resource, such as when the
1090   resource has been moved to a different URI, then the origin server
1091   MUST send a 301 (Moved Permanently) response; the user agent MAY
1092   then make its own decision regarding whether or not to redirect the
1093   request.
1094</t>
1095<t>
1096   A PUT request applied to the target resource MAY have side-effects
1097   on other resources.  For example, an article might have a URI for
1098   identifying "the current version" (a resource) which is separate
1099   from the URIs identifying each particular version (different
1100   resources that at one point shared the same state as the current version
1101   resource).  A successful PUT request on "the current version" URI might
1102   therefore create a new version resource in addition to changing the
1103   state of the target resource, and might also cause links to be added
1104   between the related resources.
1105</t>
1106<t>
1107   An origin server SHOULD reject any PUT request that contains a
1108   Content-Range header field, since it might be misinterpreted as
1109   partial content (or might be partial content that is being mistakenly
1110   PUT as a full representation).  Partial content updates are
1111   possible by targeting a separately identified resource with state
1112   that overlaps a portion of the larger resource, or by using a
1113   different method that has been specifically defined for partial
1114   updates (for example, the PATCH method defined in
1115   <xref target="RFC5789"/>).
1116</t>
1117<t>
1118   Responses to the PUT method are not cacheable. If a PUT request passes
1119   through a cache that has one or more stored responses for the effective
1120   request URI, those stored responses will be invalidated (see
1121   Section 2.5 of <xref target="Part6"/>).
1122</t>
1123</section>
1124
1125<section title="DELETE" anchor="DELETE">
1126  <iref primary="true" item="DELETE method"/>
1127  <iref primary="true" item="Methods" subitem="DELETE"/>
1128<t>
1129   The DELETE method requests that the origin server delete the target
1130   resource. This method MAY be overridden by
1131   human intervention (or other means) on the origin server. The client cannot
1132   be guaranteed that the operation has been carried out, even if the
1133   status code returned from the origin server indicates that the action
1134   has been completed successfully. However, the server SHOULD NOT
1135   indicate success unless, at the time the response is given, it
1136   intends to delete the resource or move it to an inaccessible
1137   location.
1138</t>
1139<t>
1140   A successful response SHOULD be 200 (OK) if the response includes an
1141   representation describing the status, 202 (Accepted) if the action has not
1142   yet been enacted, or 204 (No Content) if the action has been enacted
1143   but the response does not include a representation.
1144</t>
1145<t>
1146   Bodies on DELETE requests have no defined semantics. Note that sending a body
1147   on a DELETE request might cause some existing implementations to reject the
1148   request.
1149</t>
1150<t>
1151   Responses to the DELETE method are not cacheable. If a DELETE request
1152   passes through a cache that has one or more stored responses for the
1153   effective request URI, those stored responses will be invalidated (see
1154   Section 2.5 of <xref target="Part6"/>).
1155</t>
1156</section>
1157
1158<section title="TRACE" anchor="TRACE">
1159 
1160  <iref primary="true" item="TRACE method"/>
1161  <iref primary="true" item="Methods" subitem="TRACE"/>
1162<t>
1163   The TRACE method requests a remote, application-layer loop-back
1164   of the request message. The final recipient of the request
1165   SHOULD reflect the message received back to the client as the
1166   message-body of a 200 (OK) response. The final recipient is either the
1167   origin server or the first proxy to receive a Max-Forwards
1168   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1169   A TRACE request MUST NOT include a message-body.
1170</t>
1171<t>
1172   TRACE allows the client to see what is being received at the other
1173   end of the request chain and use that data for testing or diagnostic
1174   information. The value of the Via header field (Section 8.8 of <xref target="Part1"/>) is of
1175   particular interest, since it acts as a trace of the request chain.
1176   Use of the Max-Forwards header field allows the client to limit the
1177   length of the request chain, which is useful for testing a chain of
1178   proxies forwarding messages in an infinite loop.
1179</t>
1180<t>
1181   If the request is valid, the response SHOULD have a Content-Type of
1182   "message/http" (see Section 9.3.1 of <xref target="Part1"/>) and contain a message-body
1183   that encloses a copy of the entire request message.
1184   Responses to the TRACE method are not cacheable.
1185</t>
1186</section>
1187
1188<section title="CONNECT" anchor="CONNECT">
1189  <iref primary="true" item="CONNECT method"/>
1190  <iref primary="true" item="Methods" subitem="CONNECT"/>
1191<t>
1192   The CONNECT method requests that the proxy establish a tunnel
1193   to the request-target and then restrict its behavior to blind
1194   forwarding of packets until the connection is closed.
1195</t>
1196<t>
1197   When using CONNECT, the request-target MUST use the authority form
1198   (Section 3.1.1.2 of <xref target="Part1"/>); i.e., the request-target consists of only the
1199   host name and port number of the tunnel destination, separated by a colon.
1200   For example,
1201</t>
1202<figure><artwork type="message/http; msgtype=&#34;request&#34;"><![CDATA[
1203  CONNECT server.example.com:80 HTTP/1.1
1204  Host: server.example.com:80
1205 
1206  ]]></artwork></figure>
1207<t>
1208   Other HTTP mechanisms can be used normally with the CONNECT method —
1209   except end-to-end protocol Upgrade requests, since the
1210   tunnel must be established first.
1211</t>
1212<t>
1213   For example, proxy authentication might be used to establish the
1214   authority to create a tunnel:
1215</t>
1216<figure><artwork type="message/http; msgtype=&#34;request&#34;"><![CDATA[
1217  CONNECT server.example.com:80 HTTP/1.1
1218  Host: server.example.com:80
1219  Proxy-Authorization: basic aGVsbG86d29ybGQ=
1220 
1221  ]]></artwork></figure>
1222<t>
1223   Bodies on CONNECT requests have no defined semantics. Note that sending a body
1224   on a CONNECT request might cause some existing implementations to reject the
1225   request.
1226</t>
1227<t>
1228   Like any other pipelined HTTP/1.1 request, data to be tunnel may be
1229   sent immediately after the blank line. The usual caveats also apply:
1230   data may be discarded if the eventual response is negative, and the
1231   connection may be reset with no response if more than one TCP segment
1232   is outstanding.
1233</t>
1234
1235<section title="Establishing a Tunnel with CONNECT">
1236<t>
1237   Any successful (2xx) response to a CONNECT request indicates that the
1238   proxy has established a connection to the requested host and port,
1239   and has switched to tunneling the current connection to that server
1240   connection.
1241</t>
1242<t>
1243   It may be the case that the proxy itself can only reach the requested
1244   origin server through another proxy.  In this case, the first proxy
1245   SHOULD make a CONNECT request of that next proxy, requesting a tunnel
1246   to the authority.  A proxy MUST NOT respond with any 2xx status code
1247   unless it has either a direct or tunnel connection established to the
1248   authority.
1249</t>
1250<t>
1251   An origin server which receives a CONNECT request for itself MAY
1252   respond with a 2xx status code to indicate that a connection is
1253   established.
1254</t>
1255<t>
1256   If at any point either one of the peers gets disconnected, any
1257   outstanding data that came from that peer will be passed to the other
1258   one, and after that also the other connection will be terminated by
1259   the proxy. If there is outstanding data to that peer undelivered,
1260   that data will be discarded.
1261</t>
1262
1263</section>
1264</section>
1265</section>
1266
1267
1268<section title="Status Code Definitions" anchor="status.codes">
1269<t>
1270   The first digit of the Status-Code defines the class of response. The
1271   last two digits do not have any categorization role. There are 5
1272   values for the first digit:
1273  <list style="symbols">
1274    <t>
1275      1xx: Informational - Request received, continuing process
1276    </t>
1277    <t>
1278      2xx: Success - The action was successfully received,
1279        understood, and accepted
1280    </t>
1281    <t>
1282      3xx: Redirection - Further action must be taken in order to
1283        complete the request
1284    </t>
1285    <t>
1286      4xx: Client Error - The request contains bad syntax or cannot
1287        be fulfilled
1288    </t>
1289    <t>
1290      5xx: Server Error - The server failed to fulfill an apparently
1291        valid request
1292    </t>
1293  </list>
1294</t>
1295<t>
1296   Each Status-Code is described below, including any metadata required
1297   in the response.
1298</t>
1299
1300<section title="Informational 1xx" anchor="status.1xx">
1301<t>
1302   This class of status code indicates a provisional response,
1303   consisting only of the Status-Line and optional header fields, and is
1304   terminated by an empty line. There are no required header fields for this
1305   class of status code. Since HTTP/1.0 did not define any 1xx status
1306   codes, servers MUST NOT send a 1xx response to an HTTP/1.0 client
1307   except under experimental conditions.
1308</t>
1309<t>
1310   A client MUST be prepared to accept one or more 1xx status responses
1311   prior to a regular response, even if the client does not expect a 100
1312   (Continue) status message. Unexpected 1xx status responses MAY be
1313   ignored by a user agent.
1314</t>
1315<t>
1316   Proxies MUST forward 1xx responses, unless the connection between the
1317   proxy and its client has been closed, or unless the proxy itself
1318   requested the generation of the 1xx response. (For example, if a
1319   proxy adds a "Expect: 100-continue" field when it forwards a request,
1320   then it need not forward the corresponding 100 (Continue)
1321   response(s).)
1322</t>
1323
1324<section title="100 Continue" anchor="status.100">
1325  <iref primary="true" item="100 Continue (status code)"/>
1326  <iref primary="true" item="Status Codes" subitem="100 Continue"/>
1327<t>
1328   The client SHOULD continue with its request. This interim response is
1329   used to inform the client that the initial part of the request has
1330   been received and has not yet been rejected by the server. The client
1331   SHOULD continue by sending the remainder of the request or, if the
1332   request has already been completed, ignore this response. The server
1333   MUST send a final response after the request has been completed. See
1334   Section 6.2.3 of <xref target="Part1"/> for detailed discussion of the use and handling of this
1335   status code.
1336</t>
1337</section>
1338
1339<section title="101 Switching Protocols" anchor="status.101">
1340  <iref primary="true" item="101 Switching Protocols (status code)"/>
1341  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols"/>
1342<t>
1343   The server understands and is willing to comply with the client's
1344   request, via the Upgrade message header field (Section 8.7 of <xref target="Part1"/>), for a
1345   change in the application protocol being used on this connection. The
1346   server will switch protocols to those defined by the response's
1347   Upgrade header field immediately after the empty line which
1348   terminates the 101 response.
1349</t>
1350<t>
1351   The protocol SHOULD be switched only when it is advantageous to do
1352   so. For example, switching to a newer version of HTTP is advantageous
1353   over older versions, and switching to a real-time, synchronous
1354   protocol might be advantageous when delivering resources that use
1355   such features.
1356</t>
1357</section>
1358</section>
1359
1360<section title="Successful 2xx" anchor="status.2xx">
1361<t>
1362   This class of status code indicates that the client's request was
1363   successfully received, understood, and accepted.
1364</t>
1365
1366<section title="200 OK" anchor="status.200">
1367  <iref primary="true" item="200 OK (status code)"/>
1368  <iref primary="true" item="Status Codes" subitem="200 OK"/>
1369<t>
1370   The request has succeeded. The payload returned with the response
1371   is dependent on the method used in the request, for example:
1372  <list style="hanging">
1373    <t hangText="GET">
1374      a representation of the target resource is sent in the response;
1375    </t>
1376    <t hangText="HEAD">
1377      the same representation as GET, except without the message-body;
1378    </t>
1379    <t hangText="POST">
1380      a representation describing or containing the result of the action;
1381    </t>
1382    <t hangText="TRACE">
1383      a representation containing the request message as received by the
1384      end server.
1385    </t>
1386  </list>
1387</t>
1388<t>
1389   Caches MAY use a heuristic (see Section 2.3.1.1 of <xref target="Part6"/>) to determine
1390   freshness for 200 responses.
1391</t>
1392</section>
1393
1394<section title="201 Created" anchor="status.201">
1395  <iref primary="true" item="201 Created (status code)"/>
1396  <iref primary="true" item="Status Codes" subitem="201 Created"/>
1397<t>
1398   The request has been fulfilled and has resulted in a new resource being
1399   created. The newly created resource can be referenced by the URI(s)
1400   returned in the payload of the response, with the most specific URI
1401   for the resource given by a Location header field. The response
1402   SHOULD include a payload containing a list of resource
1403   characteristics and location(s) from which the user or user agent can
1404   choose the one most appropriate. The payload format is specified by
1405   the media type given in the Content-Type header field. The origin
1406   server MUST create the resource before returning the 201 status code.
1407   If the action cannot be carried out immediately, the server SHOULD
1408   respond with 202 (Accepted) response instead.
1409</t>
1410<t>
1411   A 201 response MAY contain an ETag response header field indicating
1412   the current value of the entity-tag for the representation of the resource
1413   just created (see Section 2.3 of <xref target="Part4"/>).
1414</t>
1415</section>
1416
1417<section title="202 Accepted" anchor="status.202">
1418  <iref primary="true" item="202 Accepted (status code)"/>
1419  <iref primary="true" item="Status Codes" subitem="202 Accepted"/>
1420<t>
1421   The request has been accepted for processing, but the processing has
1422   not been completed.  The request might or might not eventually be
1423   acted upon, as it might be disallowed when processing actually takes
1424   place. There is no facility for re-sending a status code from an
1425   asynchronous operation such as this.
1426</t>
1427<t>
1428   The 202 response is intentionally non-committal. Its purpose is to
1429   allow a server to accept a request for some other process (perhaps a
1430   batch-oriented process that is only run once per day) without
1431   requiring that the user agent's connection to the server persist
1432   until the process is completed. The representation returned with this
1433   response SHOULD include an indication of the request's current status
1434   and either a pointer to a status monitor or some estimate of when the
1435   user can expect the request to be fulfilled.
1436</t>
1437</section>
1438
1439<section title="203 Non-Authoritative Information" anchor="status.203">
1440  <iref primary="true" item="203 Non-Authoritative Information (status code)"/>
1441  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information"/>
1442<t>
1443   The representation in the response has been transformed or otherwise
1444   modified by a transforming proxy (Section 2.4 of <xref target="Part1"/>).  Note that the
1445   behaviour of transforming intermediaries is controlled by the no-transform
1446   Cache-Control directive (Section 3.2 of <xref target="Part6"/>).
1447</t>
1448<t>
1449   This status code is only appropriate when the response status code would
1450   have been 200 (OK) otherwise. When the status code before transformation
1451   would have been different, the 214 Transformation Applied warn-code
1452   (Section 3.6 of <xref target="Part6"/>) is appropriate.
1453</t>
1454<t>
1455   Caches MAY use a heuristic (see Section 2.3.1.1 of <xref target="Part6"/>) to determine
1456   freshness for 203 responses.
1457</t>
1458</section>
1459
1460<section title="204 No Content" anchor="status.204">
1461  <iref primary="true" item="204 No Content (status code)"/>
1462  <iref primary="true" item="Status Codes" subitem="204 No Content"/>
1463<t>
1464   The 204 (No Content) status code indicates that the server has
1465   successfully fulfilled the request and that there is no additional
1466   content to return in the response payload body.  Metadata in the
1467   response header fields refer to the target resource and its current
1468   representation after the requested action.
1469</t>
1470<t>
1471   For example, if a 204 status code is received in response to a PUT
1472   request and the response contains an ETag header field, then the PUT
1473   was successful and the ETag field-value contains the entity-tag for
1474   the new representation of that target resource.
1475</t>
1476<t>
1477   The 204 response allows a server to indicate that the action has been
1478   successfully applied to the target resource while implying that the
1479   user agent SHOULD NOT traverse away from its current "document view"
1480   (if any).  The server assumes that the user agent will provide some
1481   indication of the success to its user, in accord with its own interface,
1482   and apply any new or updated metadata in the response to the active
1483   representation.
1484</t>
1485<t>
1486   For example, a 204 status code is commonly used with document editing
1487   interfaces corresponding to a "save" action, such that the document
1488   being saved remains available to the user for editing. It is also
1489   frequently used with interfaces that expect automated data transfers
1490   to be prevalent, such as within distributed version control systems.
1491</t>
1492<t>
1493   The 204 response MUST NOT include a message-body, and thus is always
1494   terminated by the first empty line after the header fields.
1495</t>
1496</section>
1497
1498<section title="205 Reset Content" anchor="status.205">
1499  <iref primary="true" item="205 Reset Content (status code)"/>
1500  <iref primary="true" item="Status Codes" subitem="205 Reset Content"/>
1501<t>
1502   The server has fulfilled the request and the user agent SHOULD reset
1503   the document view which caused the request to be sent. This response
1504   is primarily intended to allow input for actions to take place via
1505   user input, followed by a clearing of the form in which the input is
1506   given so that the user can easily initiate another input action.
1507</t>
1508<t>   
1509   The message-body included with the response MUST be empty. Note that
1510   receivers still need to parse the response according to the algorithm defined
1511   in Section 3.3 of <xref target="Part1"/>.
1512</t>
1513</section>
1514
1515<section title="206 Partial Content" anchor="status.206">
1516  <iref primary="true" item="206 Partial Content (status code)"/>
1517  <iref primary="true" item="Status Codes" subitem="206 Partial Content"/>
1518 
1519<t>
1520   The server has fulfilled the partial GET request for the resource
1521   and the enclosed payload is a partial representation as defined in Section 3.1 of <xref target="Part5"/>.
1522</t>
1523<t>
1524   Caches MAY use a heuristic (see Section 2.3.1.1 of <xref target="Part6"/>) to determine
1525   freshness for 206 responses.
1526</t>
1527</section>
1528</section>
1529
1530<section title="Redirection 3xx" anchor="status.3xx">
1531<t>
1532   This class of status code indicates that further action needs to be
1533   taken by the user agent in order to fulfill the request.  If the required
1534   action involves a subsequent HTTP request, it MAY be carried out by the
1535   user agent without interaction with the user if and only if the method used
1536   in the second request is known to be "safe", as defined in
1537   <xref target="safe.methods"/>.
1538</t>
1539<t>
1540   There are several types of redirects:
1541   <list style="numbers">
1542      <t>
1543          Redirects of the request to another URI, either temporarily or
1544          permanently. The new URI is specified in the Location header field.
1545          In this specification, the status codes 301 (Moved Permanently),
1546          302 (Found), and 307 (Temporary Redirect) fall under this category.
1547        </t>
1548      <t>
1549          Redirection to a new location that represents an indirect response to
1550          the request, such as the result of a POST operation to be retrieved
1551          with a subsequent GET request. This is status code 303 (See Other).
1552        </t>
1553      <t>
1554          Redirection offering a choice of matching resources for use by
1555          agent-driven content negotiation (Section 5.2 of <xref target="Part3"/>). This
1556          is status code 300 (Multiple Choices).
1557        </t>
1558      <t>
1559          Other kinds of redirection, such as to a cached result (status code 304
1560          (Not Modified)).
1561        </t>
1562   </list>
1563</t>
1564<t><list>
1565  <t>
1566    Note: In HTTP/1.0, only the status codes 301 (Moved Permanently)
1567    and 302 (Found) were defined for the first type of redirect, and the second
1568    type did not exist at all (<xref target="RFC1945"/>, Section 9.3).
1569    However it turned out that web forms using POST expected redirects to change
1570    the operation for the subsequent request to retrieval (GET). To address this
1571    use case, HTTP/1.1 introduced the second type of redirect with the status
1572    code 303 (See Other) (<xref target="RFC2068"/>, Section 10.3.4).
1573    As user agents did not change their behavior to maintain backwards
1574    compatibility, the first revision of HTTP/1.1 added yet another status code,
1575    307 (Temporary Redirect), for which the backwards compatibility problems did
1576    not apply (<xref target="RFC2616"/>, Section 10.3.8).
1577    Over 10 years later, most user agents still do method rewriting for
1578    status codes 301 and 302, therefore this specification makes that behavior
1579    compliant in case the original request was POST.
1580  </t>
1581</list></t>
1582<t>
1583   Clients SHOULD detect and intervene in cyclical redirections (i.e.,
1584   "infinite" redirection loops).
1585</t>
1586<t><list>
1587  <t>
1588    Note: An earlier version of this specification recommended a
1589    maximum of five redirections (<xref target="RFC2068"/>, Section 10.3).
1590    Content developers need to be aware that some clients might
1591    implement such a fixed limitation.
1592  </t>
1593</list></t>
1594
1595<section title="300 Multiple Choices" anchor="status.300">
1596  <iref primary="true" item="300 Multiple Choices (status code)"/>
1597  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices"/>
1598<t>
1599   The target resource has more than one
1600   representation, each with its own specific location, and agent-driven
1601   negotiation information (Section 5 of <xref target="Part3"/>) is being provided so that
1602   the user (or user agent) can select a preferred representation by
1603   redirecting its request to that location.
1604</t>
1605<t>
1606   Unless it was a HEAD request, the response SHOULD include a representation
1607   containing a list of representation metadata and location(s) from
1608   which the user or user agent can choose the one most appropriate. The
1609   data format is specified by the media type given in the Content-Type
1610   header field. Depending upon the format and the capabilities of
1611   the user agent, selection of the most appropriate choice MAY be
1612   performed automatically. However, this specification does not define
1613   any standard for such automatic selection.
1614</t>
1615<t>
1616   If the server has a preferred choice of representation, it SHOULD
1617   include the specific URI for that representation in the Location
1618   field; user agents MAY use the Location field value for automatic
1619   redirection.
1620</t>
1621<t>
1622   Caches MAY use a heuristic (see Section 2.3.1.1 of <xref target="Part6"/>) to determine
1623   freshness for 300 responses.
1624</t>
1625
1626</section>
1627
1628<section title="301 Moved Permanently" anchor="status.301">
1629  <iref primary="true" item="301 Moved Permanently (status code)"/>
1630  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently"/>
1631<t>
1632   The target resource has been assigned a new permanent URI and any
1633   future references to this resource SHOULD use one of the returned
1634   URIs.  Clients with link editing capabilities ought to automatically
1635   re-link references to the effective request URI to one or more of the new
1636   references returned by the server, where possible.
1637</t>
1638<t>
1639   Caches MAY use a heuristic (see Section 2.3.1.1 of <xref target="Part6"/>) to determine
1640   freshness for 301 responses.
1641</t>
1642<t>
1643   The new permanent URI SHOULD be given by the Location field in the
1644   response. Unless the request method was HEAD, the representation of the
1645   response SHOULD contain a short hypertext note with a hyperlink to
1646   the new URI(s).
1647</t>
1648<t>
1649   If the 301 status code is received in response to a request method
1650   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1651   then the request MAY be automatically redirected by the user agent without
1652   confirmation.  Otherwise, the user agent MUST NOT automatically redirect the
1653   request unless it can be confirmed by the user, since this might
1654   change the conditions under which the request was issued.
1655</t>
1656<t><list>
1657  <t>
1658    Note: For historic reasons, user agents MAY change the
1659    request method from POST to GET for the subsequent request. If this
1660    behavior is undesired, status code 307 (Temporary Redirect) can be used
1661    instead.
1662  </t>
1663</list></t>
1664</section>
1665
1666<section title="302 Found" anchor="status.302">
1667  <iref primary="true" item="302 Found (status code)"/>
1668  <iref primary="true" item="Status Codes" subitem="302 Found"/>
1669<t>
1670   The target resource resides temporarily under a different URI.
1671   Since the redirection might be altered on occasion, the client SHOULD
1672   continue to use the effective request URI for future requests.
1673</t>
1674<t>
1675   The temporary URI SHOULD be given by the Location field in the
1676   response. Unless the request method was HEAD, the representation of the
1677   response SHOULD contain a short hypertext note with a hyperlink to
1678   the new URI(s).
1679</t>
1680<t>
1681   If the 302 status code is received in response to a request method
1682   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1683   then the request MAY be automatically redirected by the user agent without
1684   confirmation.  Otherwise, the user agent MUST NOT automatically redirect the
1685   request unless it can be confirmed by the user, since this might
1686   change the conditions under which the request was issued.
1687</t>
1688<t><list>
1689  <t>
1690    Note: For historic reasons, user agents MAY change the
1691    request method from POST to GET for the subsequent request. If this
1692    behavior is undesired, status code 307 (Temporary Redirect) can be used
1693    instead.
1694    <cref anchor="issue312">but see &lt;http://trac.tools.ietf.org/wg/httpbis/trac/ticket/312&gt;</cref>
1695  </t>
1696</list></t>
1697</section>
1698
1699<section title="303 See Other" anchor="status.303">
1700  <iref primary="true" item="303 See Other (status code)"/>
1701  <iref primary="true" item="Status Codes" subitem="303 See Other"/>
1702<t>
1703   The 303 status code indicates that the server is redirecting the
1704   user agent to a different resource, as indicated by a URI in the
1705   Location header field, that is intended to provide an indirect
1706   response to the original request.  In order to satisfy the original
1707   request, a user agent SHOULD perform a retrieval request using the
1708   Location URI (a GET or HEAD request if using HTTP), which
1709   may itself be redirected further, and present the eventual result as an
1710   answer to the original request.
1711   Note that the new URI in the Location header field is not considered
1712   equivalent to the effective request URI.
1713</t>
1714<t>
1715   This status code is generally applicable to any HTTP method.  It is
1716   primarily used to allow the output of a POST action to redirect
1717   the user agent to a selected resource, since doing so provides the
1718   information corresponding to the POST response in a form that
1719   can be separately identified, bookmarked, and cached independent
1720   of the original request.
1721</t>
1722<t>
1723   A 303 response to a GET request indicates that the requested
1724   resource does not have a representation of its own that can be
1725   transferred by the server over HTTP.  The Location URI indicates a
1726   resource that is descriptive of the target resource, such that the
1727   follow-on representation might be useful to recipients without
1728   implying that it adequately represents the target resource.
1729   Note that answers to the questions of what can be represented, what
1730   representations are adequate, and what might be a useful description
1731   are outside the scope of HTTP and thus entirely determined by the
1732   URI owner(s).
1733</t>
1734<t>
1735   Except for responses to a HEAD request, the representation of a 303
1736   response SHOULD contain a short hypertext note with a hyperlink
1737   to the Location URI.
1738</t>
1739</section>
1740
1741<section title="304 Not Modified" anchor="status.304">
1742  <iref primary="true" item="304 Not Modified (status code)"/>
1743  <iref primary="true" item="Status Codes" subitem="304 Not Modified"/>
1744 
1745<t>
1746   The response to the request has not been modified since the conditions
1747   indicated by the client's conditional GET request, as defined in Section 4.1 of <xref target="Part4"/>.
1748</t>
1749</section>
1750
1751<section title="305 Use Proxy" anchor="status.305">
1752  <iref primary="true" item="305 Use Proxy (status code)"/>
1753  <iref primary="true" item="Status Codes" subitem="305 Use Proxy"/>
1754<t>
1755   The 305 status code was defined in a previous version of this specification
1756   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1757</t>
1758</section>
1759
1760<section title="306 (Unused)" anchor="status.306">
1761  <iref primary="true" item="306 (Unused) (status code)"/>
1762  <iref primary="true" item="Status Codes" subitem="306 (Unused)"/>
1763<t>
1764   The 306 status code was used in a previous version of the
1765   specification, is no longer used, and the code is reserved.
1766</t>
1767</section>
1768
1769<section title="307 Temporary Redirect" anchor="status.307">
1770  <iref primary="true" item="307 Temporary Redirect (status code)"/>
1771  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect"/>
1772<t>
1773   The target resource resides temporarily under a different URI.
1774   Since the redirection can change over time, the client SHOULD
1775   continue to use the effective request URI for future requests.
1776</t>
1777<t>
1778   The temporary URI SHOULD be given by the Location field in the
1779   response. Unless the request method was HEAD, the representation of the
1780   response SHOULD contain a short hypertext note with a hyperlink to
1781   the new URI(s), since many pre-HTTP/1.1 user agents do not
1782   understand the 307 status code. Therefore, the note SHOULD contain the
1783   information necessary for a user to repeat the original request on
1784   the new URI.
1785</t>
1786<t>
1787   If the 307 status code is received in response to a request method
1788   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1789   then the request MAY be automatically redirected by the user agent without
1790   confirmation.  Otherwise, the user agent MUST NOT automatically redirect the
1791   request unless it can be confirmed by the user, since this might
1792   change the conditions under which the request was issued.
1793</t>
1794</section>
1795</section>
1796
1797<section title="Client Error 4xx" anchor="status.4xx">
1798<t>
1799   The 4xx class of status code is intended for cases in which the
1800   client seems to have erred. Except when responding to a HEAD request,
1801   the server SHOULD include a representation containing an explanation of the
1802   error situation, and whether it is a temporary or permanent
1803   condition. These status codes are applicable to any request method.
1804   User agents SHOULD display any included representation to the user.
1805</t>
1806<t>
1807   If the client is sending data, a server implementation using TCP
1808   SHOULD be careful to ensure that the client acknowledges receipt of
1809   the packet(s) containing the response, before the server closes the
1810   input connection. If the client continues sending data to the server
1811   after the close, the server's TCP stack will send a reset packet to
1812   the client, which might erase the client's unacknowledged input buffers
1813   before they can be read and interpreted by the HTTP application.
1814</t>
1815
1816<section title="400 Bad Request" anchor="status.400">
1817  <iref primary="true" item="400 Bad Request (status code)"/>
1818  <iref primary="true" item="Status Codes" subitem="400 Bad Request"/>
1819<t>
1820   The server cannot or will not process the request, due to a client error (e.g.,
1821   malformed syntax).</t>
1822</section>
1823
1824<section title="401 Unauthorized" anchor="status.401">
1825  <iref primary="true" item="401 Unauthorized (status code)"/>
1826  <iref primary="true" item="Status Codes" subitem="401 Unauthorized"/>
1827 
1828<t>
1829   The request requires user authentication (see Section 3.1 of <xref target="Part7"/>).
1830</t>
1831</section>
1832
1833<section title="402 Payment Required" anchor="status.402">
1834  <iref primary="true" item="402 Payment Required (status code)"/>
1835  <iref primary="true" item="Status Codes" subitem="402 Payment Required"/>
1836<t>
1837   This code is reserved for future use.
1838</t>
1839</section>
1840
1841<section title="403 Forbidden" anchor="status.403">
1842  <iref primary="true" item="403 Forbidden (status code)"/>
1843  <iref primary="true" item="Status Codes" subitem="403 Forbidden"/>
1844<t>
1845   The server understood the request, but refuses to authorize it. Providing
1846   different user authentication credentials might be successful, but any
1847   credentials that were provided in the request are insufficient. The request
1848   SHOULD NOT be repeated with the same credentials.
1849</t>
1850<t>
1851   If the request method was not HEAD and the server wishes to make
1852   public why the request has not been fulfilled, it SHOULD describe the
1853   reason for the refusal in the representation.  If the server does not wish to
1854   make this information available to the client, the status code 404
1855   (Not Found) MAY be used instead.
1856</t>
1857</section>
1858
1859<section title="404 Not Found" anchor="status.404">
1860  <iref primary="true" item="404 Not Found (status code)"/>
1861  <iref primary="true" item="Status Codes" subitem="404 Not Found"/>
1862<t>
1863   The server has not found anything matching the effective request URI. No
1864   indication is given of whether the condition is temporary or
1865   permanent. The 410 (Gone) status code SHOULD be used if the server
1866   knows, through some internally configurable mechanism, that an old
1867   resource is permanently unavailable and has no forwarding address.
1868   This status code is commonly used when the server does not wish to
1869   reveal exactly why the request has been refused, or when no other
1870   response is applicable.
1871</t>
1872</section>
1873
1874<section title="405 Method Not Allowed" anchor="status.405">
1875  <iref primary="true" item="405 Method Not Allowed (status code)"/>
1876  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed"/>
1877<t>
1878   The method specified in the Request-Line is not allowed for the target
1879   resource. The response MUST include an Allow header field containing a
1880   list of valid methods for the requested resource.
1881</t>
1882</section>
1883
1884<section title="406 Not Acceptable" anchor="status.406">
1885  <iref primary="true" item="406 Not Acceptable (status code)"/>
1886  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable"/>
1887<t>
1888   The resource identified by the request is only capable of generating
1889   response representations which have content characteristics not acceptable
1890   according to the Accept and Accept-* header fields sent in the request
1891   (see Section 6 of <xref target="Part3"/>).
1892</t>
1893<t>
1894   Unless it was a HEAD request, the response SHOULD include a representation
1895   containing a list of available representation characteristics and location(s)
1896   from which the user or user agent can choose the one most
1897   appropriate. The data format is specified by the media type given
1898   in the Content-Type header field. Depending upon the format and the
1899   capabilities of the user agent, selection of the most appropriate
1900   choice MAY be performed automatically. However, this specification
1901   does not define any standard for such automatic selection.
1902</t>
1903<t><list>
1904  <t>
1905    Note: HTTP/1.1 servers are allowed to return responses which are
1906    not acceptable according to the accept header fields sent in the
1907    request. In some cases, this might even be preferable to sending a
1908    406 response. User agents are encouraged to inspect the header fields of
1909    an incoming response to determine if it is acceptable.
1910  </t>
1911</list></t>
1912<t>
1913   If the response could be unacceptable, a user agent SHOULD
1914   temporarily stop receipt of more data and query the user for a
1915   decision on further actions.
1916</t>
1917</section>
1918
1919<section title="407 Proxy Authentication Required" anchor="status.407">
1920  <iref primary="true" item="407 Proxy Authentication Required (status code)"/>
1921  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required"/>
1922<t>
1923   This code is similar to 401 (Unauthorized), but indicates that the
1924   client must first authenticate itself with the proxy (see Section 3.2 of <xref target="Part7"/>).
1925</t>
1926</section>
1927
1928<section title="408 Request Timeout" anchor="status.408">
1929  <iref primary="true" item="408 Request Timeout (status code)"/>
1930  <iref primary="true" item="Status Codes" subitem="408 Request Timeout"/>
1931<t>
1932   The client did not produce a request within the time that the server
1933   was prepared to wait. The client MAY repeat the request without
1934   modifications at any later time.
1935</t>
1936</section>
1937
1938<section title="409 Conflict" anchor="status.409">
1939  <iref primary="true" item="409 Conflict (status code)"/>
1940  <iref primary="true" item="Status Codes" subitem="409 Conflict"/>
1941<t>
1942   The request could not be completed due to a conflict with the current
1943   state of the resource. This code is only allowed in situations where
1944   it is expected that the user might be able to resolve the conflict
1945   and resubmit the request. The response body SHOULD include enough
1946   information for the user to recognize the source of the conflict.
1947   Ideally, the response representation would include enough information for the
1948   user or user agent to fix the problem; however, that might not be
1949   possible and is not required.
1950</t>
1951<t>
1952   Conflicts are most likely to occur in response to a PUT request. For
1953   example, if versioning were being used and the representation being PUT
1954   included changes to a resource which conflict with those made by an
1955   earlier (third-party) request, the server might use the 409 response
1956   to indicate that it can't complete the request. In this case, the
1957   response representation would likely contain a list of the differences
1958   between the two versions in a format defined by the response
1959   Content-Type.
1960</t>
1961</section>
1962
1963<section title="410 Gone" anchor="status.410">
1964  <iref primary="true" item="410 Gone (status code)"/>
1965  <iref primary="true" item="Status Codes" subitem="410 Gone"/>
1966<t>
1967   The target resource is no longer available at the server and no
1968   forwarding address is known. This condition is expected to be
1969   considered permanent. Clients with link editing capabilities SHOULD
1970   delete references to the effective request URI after user approval. If the
1971   server does not know, or has no facility to determine, whether or not
1972   the condition is permanent, the status code 404 (Not Found) SHOULD be
1973   used instead.
1974</t>
1975<t>
1976   The 410 response is primarily intended to assist the task of web
1977   maintenance by notifying the recipient that the resource is
1978   intentionally unavailable and that the server owners desire that
1979   remote links to that resource be removed. Such an event is common for
1980   limited-time, promotional services and for resources belonging to
1981   individuals no longer working at the server's site. It is not
1982   necessary to mark all permanently unavailable resources as "gone" or
1983   to keep the mark for any length of time — that is left to the
1984   discretion of the server owner.
1985</t>
1986<t>
1987   Caches MAY use a heuristic (see Section 2.3.1.1 of <xref target="Part6"/>) to determine freshness
1988   for 410 responses.
1989</t>
1990
1991</section>
1992
1993<section title="411 Length Required" anchor="status.411">
1994  <iref primary="true" item="411 Length Required (status code)"/>
1995  <iref primary="true" item="Status Codes" subitem="411 Length Required"/>
1996<t>
1997   The server refuses to accept the request without a defined Content-Length.
1998   The client MAY repeat the request if it adds a valid
1999   Content-Length header field containing the length of the message-body
2000   in the request message.
2001</t>
2002</section>
2003
2004<section title="412 Precondition Failed" anchor="status.412">
2005  <iref primary="true" item="412 Precondition Failed (status code)"/>
2006  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed"/>
2007 
2008<t>
2009   The precondition given in one or more of the header fields
2010   evaluated to false when it was tested on the server, as defined in
2011   Section 4.2 of <xref target="Part4"/>.
2012</t>
2013</section>
2014
2015<section title="413 Request Representation Too Large" anchor="status.413">
2016  <iref primary="true" item="413 Request Representation Too Large (status code)"/>
2017  <iref primary="true" item="Status Codes" subitem="413 Request Representation Too Large"/>
2018<t>
2019   The server is refusing to process a request because the request
2020   representation is larger than the server is willing or able to process. The
2021   server MAY close the connection to prevent the client from continuing
2022   the request.
2023</t>
2024<t>
2025   If the condition is temporary, the server SHOULD include a Retry-After
2026   header field to indicate that it is temporary and after what
2027   time the client MAY try again.
2028</t>
2029</section>
2030
2031<section title="414 URI Too Long" anchor="status.414">
2032  <iref primary="true" item="414 URI Too Long (status code)"/>
2033  <iref primary="true" item="Status Codes" subitem="414 URI Too Long"/>
2034<t>
2035   The server is refusing to service the request because the effective request URI
2036   is longer than the server is willing to interpret. This rare
2037   condition is only likely to occur when a client has improperly
2038   converted a POST request to a GET request with long query
2039   information, when the client has descended into a URI "black hole" of
2040   redirection (e.g., a redirected URI prefix that points to a suffix of
2041   itself), or when the server is under attack by a client attempting to
2042   exploit security holes present in some servers using fixed-length
2043   buffers for reading or manipulating the effective request URI.
2044</t>
2045</section>
2046
2047<section title="415 Unsupported Media Type" anchor="status.415">
2048  <iref primary="true" item="415 Unsupported Media Type (status code)"/>
2049  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type"/>
2050<t>
2051   The server is refusing to service the request because the request
2052   payload is in a format not supported by this request method on the
2053   target resource.
2054</t>
2055</section>
2056
2057<section title="416 Requested Range Not Satisfiable" anchor="status.416">
2058  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)"/>
2059  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable"/>
2060 
2061<t>
2062   The request included a Range header field (Section 5.4 of <xref target="Part5"/>) and none of
2063   the range-specifier values in this field overlap the current extent
2064   of the selected resource. See Section 3.2 of <xref target="Part5"/>.
2065</t>
2066</section>
2067
2068<section title="417 Expectation Failed" anchor="status.417">
2069  <iref primary="true" item="417 Expectation Failed (status code)"/>
2070  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed"/>
2071<t>
2072   The expectation given in an Expect header field (see <xref target="header.expect"/>)
2073   could not be met by this server, or, if the server is a proxy,
2074   the server has unambiguous evidence that the request could not be met
2075   by the next-hop server.
2076</t>
2077</section>
2078
2079<section title="426 Upgrade Required" anchor="status.426">
2080  <iref primary="true" item="426 Upgrade Required (status code)"/>
2081  <iref primary="true" item="Status Codes" subitem="426 Upgrade Required"/>
2082<t>
2083   The request can not be completed without a prior protocol upgrade. This
2084   response MUST include an Upgrade header field (Section 8.7 of <xref target="Part1"/>)
2085   specifying the required protocols.
2086</t>
2087<figure>
2088<preamble>Example:</preamble>
2089<artwork type="message/http; msgtype=&#34;request&#34;"><![CDATA[
2090  HTTP/1.1 426 Upgrade Required
2091  Upgrade: HTTP/2.0
2092  Connection: Upgrade
2093 
2094  ]]></artwork></figure>
2095<t>
2096   The server SHOULD include a message body in the 426 response which
2097   indicates in human readable form the reason for the error and describes any
2098   alternative courses which may be available to the user.
2099</t>
2100</section>
2101</section>
2102
2103<section title="Server Error 5xx" anchor="status.5xx">
2104<t>
2105   Response status codes beginning with the digit "5" indicate cases in
2106   which the server is aware that it has erred or is incapable of
2107   performing the request. Except when responding to a HEAD request, the
2108   server SHOULD include a representation containing an explanation of the
2109   error situation, and whether it is a temporary or permanent
2110   condition. User agents SHOULD display any included representation to the
2111   user. These response codes are applicable to any request method.
2112</t>
2113
2114<section title="500 Internal Server Error" anchor="status.500">
2115  <iref primary="true" item="500 Internal Server Error (status code)"/>
2116  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error"/>
2117<t>
2118   The server encountered an unexpected condition which prevented it
2119   from fulfilling the request.
2120</t>
2121</section>
2122
2123<section title="501 Not Implemented" anchor="status.501">
2124  <iref primary="true" item="501 Not Implemented (status code)"/>
2125  <iref primary="true" item="Status Codes" subitem="501 Not Implemented"/>
2126<t>
2127   The server does not support the functionality required to fulfill the
2128   request. This is the appropriate response when the server does not
2129   recognize the request method and is not capable of supporting it for
2130   any resource.
2131</t>
2132</section>
2133
2134<section title="502 Bad Gateway" anchor="status.502">
2135  <iref primary="true" item="502 Bad Gateway (status code)"/>
2136  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway"/>
2137<t>
2138   The server, while acting as a gateway or proxy, received an invalid
2139   response from the upstream server it accessed in attempting to
2140   fulfill the request.
2141</t>
2142</section>
2143
2144<section title="503 Service Unavailable" anchor="status.503">
2145  <iref primary="true" item="503 Service Unavailable (status code)"/>
2146  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable"/>
2147<t>
2148   The server is currently unable or unwilling to handle the request due to
2149   reasons such as temporary overloading, maintenance of the server, or rate
2150   limiting of the client.
2151</t>
2152<t>
2153   The implication is that this is a temporary condition which will be
2154   alleviated after some delay. If known, the length of the delay MAY be
2155   indicated in a Retry-After header field (<xref target="header.retry-after"/>).
2156   If no Retry-After is given, the client SHOULD handle the response as it
2157   would for a 500 response.
2158</t>
2159<t><list>
2160  <t>
2161    Note: The existence of the 503 status code does not imply that a
2162    server must use it when becoming overloaded. Some servers might wish
2163    to simply refuse the connection.
2164  </t>
2165</list></t>
2166</section>
2167
2168<section title="504 Gateway Timeout" anchor="status.504">
2169  <iref primary="true" item="504 Gateway Timeout (status code)"/>
2170  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout"/>
2171<t>
2172   The server, while acting as a gateway or proxy, did not receive a
2173   timely response from the upstream server specified by the URI (e.g.,
2174   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
2175   to access in attempting to complete the request.
2176</t>
2177<t><list>
2178  <t>
2179    Note to implementors: some deployed proxies are known to
2180    return 400 or 500 when DNS lookups time out.
2181  </t>
2182</list></t>
2183</section>
2184
2185<section title="505 HTTP Version Not Supported" anchor="status.505">
2186  <iref primary="true" item="505 HTTP Version Not Supported (status code)"/>
2187  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported"/>
2188<t>
2189   The server does not support, or refuses to support, the protocol
2190   version that was used in the request message. The server is
2191   indicating that it is unable or unwilling to complete the request
2192   using the same major version as the client, as described in Section 2.6 of <xref target="Part1"/>,
2193   other than with this error message. The response SHOULD contain
2194   a representation describing why that version is not supported and what other
2195   protocols are supported by that server.
2196</t>
2197
2198</section>
2199</section>
2200</section>
2201
2202
2203<section title="Date/Time Formats" anchor="http.date">
2204 
2205<t>
2206   HTTP applications have historically allowed three different formats
2207   for date/time stamps. However, the preferred format is a fixed-length subset
2208   of that defined by <xref target="RFC1123"/>:
2209</t>
2210<figure><artwork type="example"><![CDATA[
2211  Sun, 06 Nov 1994 08:49:37 GMT  ; RFC 1123
2212  ]]></artwork></figure>
2213<t>
2214   The other formats are described here only for compatibility with obsolete
2215   implementations.
2216</t>
2217<figure><artwork type="example"><![CDATA[
2218  Sunday, 06-Nov-94 08:49:37 GMT ; obsolete RFC 850 format
2219  Sun Nov  6 08:49:37 1994       ; ANSI C's asctime() format
2220  ]]></artwork></figure>
2221<t>
2222   HTTP/1.1 clients and servers that parse a date value MUST accept
2223   all three formats (for compatibility with HTTP/1.0), though they MUST
2224   only generate the RFC 1123 format for representing HTTP-date values
2225   in header fields.
2226</t>
2227<t>
2228   All HTTP date/time stamps MUST be represented in Greenwich Mean Time
2229   (GMT), without exception. For the purposes of HTTP, GMT is exactly
2230   equal to UTC (Coordinated Universal Time). This is indicated in the
2231   first two formats by the inclusion of "GMT" as the three-letter
2232   abbreviation for time zone, and MUST be assumed when reading the
2233   asctime format. HTTP-date is case sensitive and MUST NOT include
2234   additional whitespace beyond that specifically included as SP in the
2235   grammar.
2236</t>
2237<figure><iref primary="true" item="Grammar" subitem="HTTP-date"/><artwork type="abnf2616"><![CDATA[
2238  HTTP-date    = rfc1123-date / obs-date
2239]]></artwork></figure>
2240<t anchor="preferred.date.format">
2241 
2242 
2243 
2244 
2245 
2246 
2247 
2248 
2249 
2250 
2251  Preferred format:
2252</t>
2253<figure><iref primary="true" item="Grammar" subitem="rfc1123-date"/><iref primary="true" item="Grammar" subitem="date1"/><iref primary="true" item="Grammar" subitem="time-of-day"/><iref primary="true" item="Grammar" subitem="hour"/><iref primary="true" item="Grammar" subitem="minute"/><iref primary="true" item="Grammar" subitem="second"/><iref primary="true" item="Grammar" subitem="day-name"/><iref primary="true" item="Grammar" subitem="day-name-l"/><iref primary="true" item="Grammar" subitem="day"/><iref primary="true" item="Grammar" subitem="month"/><iref primary="true" item="Grammar" subitem="year"/><iref primary="true" item="Grammar" subitem="GMT"/><artwork type="abnf2616"><![CDATA[
2254  rfc1123-date = day-name "," SP date1 SP time-of-day SP GMT
2255  ; fixed length subset of the format defined in
2256  ; Section 5.2.14 of [RFC1123]
2257 
2258  day-name     = %x4D.6F.6E ; "Mon", case-sensitive
2259               / %x54.75.65 ; "Tue", case-sensitive
2260               / %x57.65.64 ; "Wed", case-sensitive
2261               / %x54.68.75 ; "Thu", case-sensitive
2262               / %x46.72.69 ; "Fri", case-sensitive
2263               / %x53.61.74 ; "Sat", case-sensitive
2264               / %x53.75.6E ; "Sun", case-sensitive
2265               
2266  date1        = day SP month SP year
2267               ; e.g., 02 Jun 1982
2268
2269  day          = 2DIGIT
2270  month        = %x4A.61.6E ; "Jan", case-sensitive
2271               / %x46.65.62 ; "Feb", case-sensitive
2272               / %x4D.61.72 ; "Mar", case-sensitive
2273               / %x41.70.72 ; "Apr", case-sensitive
2274               / %x4D.61.79 ; "May", case-sensitive
2275               / %x4A.75.6E ; "Jun", case-sensitive
2276               / %x4A.75.6C ; "Jul", case-sensitive
2277               / %x41.75.67 ; "Aug", case-sensitive
2278               / %x53.65.70 ; "Sep", case-sensitive
2279               / %x4F.63.74 ; "Oct", case-sensitive
2280               / %x4E.6F.76 ; "Nov", case-sensitive
2281               / %x44.65.63 ; "Dec", case-sensitive
2282  year         = 4DIGIT
2283
2284  GMT   = %x47.4D.54 ; "GMT", case-sensitive
2285
2286  time-of-day  = hour ":" minute ":" second
2287                 ; 00:00:00 - 23:59:59
2288                 
2289  hour         = 2DIGIT               
2290  minute       = 2DIGIT               
2291  second       = 2DIGIT               
2292]]></artwork></figure>
2293<t>
2294  The semantics of <xref target="preferred.date.format" format="none">day-name</xref>, <xref target="preferred.date.format" format="none">day</xref>,
2295  <xref target="preferred.date.format" format="none">month</xref>, <xref target="preferred.date.format" format="none">year</xref>, and <xref target="preferred.date.format" format="none">time-of-day</xref> are the
2296  same as those defined for the RFC 5322 constructs
2297  with the corresponding name (<xref target="RFC5322"/>, Section 3.3).
2298</t>
2299<t anchor="obsolete.date.formats">
2300 
2301 
2302 
2303 
2304 
2305 
2306 
2307 
2308  Obsolete formats:
2309</t>
2310<figure><iref primary="true" item="Grammar" subitem="obs-date"/><artwork type="abnf2616"><![CDATA[
2311  obs-date     = rfc850-date / asctime-date
2312]]></artwork></figure>
2313<figure><iref primary="true" item="Grammar" subitem="rfc850-date"/><artwork type="abnf2616"><![CDATA[
2314  rfc850-date  = day-name-l "," SP date2 SP time-of-day SP GMT
2315  date2        = day "-" month "-" 2DIGIT
2316                 ; day-month-year (e.g., 02-Jun-82)
2317
2318  day-name-l   = %x4D.6F.6E.64.61.79 ; "Monday", case-sensitive
2319         / %x54.75.65.73.64.61.79 ; "Tuesday", case-sensitive
2320         / %x57.65.64.6E.65.73.64.61.79 ; "Wednesday", case-sensitive
2321         / %x54.68.75.72.73.64.61.79 ; "Thursday", case-sensitive
2322         / %x46.72.69.64.61.79 ; "Friday", case-sensitive
2323         / %x53.61.74.75.72.64.61.79 ; "Saturday", case-sensitive
2324         / %x53.75.6E.64.61.79 ; "Sunday", case-sensitive
2325]]></artwork></figure>
2326<figure><iref primary="true" item="Grammar" subitem="asctime-date"/><artwork type="abnf2616"><![CDATA[
2327  asctime-date = day-name SP date3 SP time-of-day SP year
2328  date3        = month SP ( 2DIGIT / ( SP 1DIGIT ))
2329                 ; month day (e.g., Jun  2)
2330]]></artwork></figure>
2331<t><list>
2332  <t>
2333    Note: Recipients of date values are encouraged to be robust in
2334    accepting date values that might have been sent by non-HTTP
2335    applications, as is sometimes the case when retrieving or posting
2336    messages via proxies/gateways to SMTP or NNTP.
2337  </t>
2338</list></t>
2339<t><list>
2340  <t>
2341    Note: HTTP requirements for the date/time stamp format apply only
2342    to their usage within the protocol stream. Clients and servers are
2343    not required to use these formats for user presentation, request
2344    logging, etc.
2345  </t>
2346</list></t>
2347</section>
2348
2349
2350<section title="Header Field Definitions" anchor="header.field.definitions">
2351<t>
2352   This section defines the syntax and semantics of HTTP/1.1 header fields
2353   related to request and response semantics.
2354</t>
2355
2356<section title="Allow" anchor="header.allow">
2357  <iref primary="true" item="Allow header field"/>
2358  <iref primary="true" item="Header Fields" subitem="Allow"/>
2359 
2360<t>
2361   The "Allow" header field lists the set of methods advertised as
2362   supported by the target resource. The purpose of this field is strictly to
2363   inform the recipient of valid request methods associated with the resource.
2364</t>
2365<figure><iref primary="true" item="Grammar" subitem="Allow"/><artwork type="abnf2616"><![CDATA[
2366  Allow = #Method
2367]]></artwork></figure>
2368<t>
2369   Example of use:
2370</t>
2371<figure><artwork type="example"><![CDATA[
2372  Allow: GET, HEAD, PUT
2373]]></artwork></figure>
2374<t>
2375   The actual set of allowed methods is defined by the origin server at the
2376   time of each request.
2377</t>
2378<t>
2379   A proxy MUST NOT modify the Allow header field — it does not need to
2380   understand all the methods specified in order to handle them according to
2381   the generic message handling rules.
2382</t>
2383</section>
2384
2385<section title="Date" anchor="header.date">
2386  <iref primary="true" item="Date header field"/>
2387  <iref primary="true" item="Header Fields" subitem="Date"/>
2388 
2389<t>
2390   The "Date" header field represents the date and time at which
2391   the message was originated, having the same semantics as the Origination
2392   Date Field (orig-date) defined in Section 3.6.1 of <xref target="RFC5322"/>.
2393   The field value is an HTTP-date, as defined in <xref target="http.date"/>;
2394   it MUST be sent in rfc1123-date format.
2395</t>
2396<figure><iref primary="true" item="Grammar" subitem="Date"/><artwork type="abnf2616"><![CDATA[
2397  Date = HTTP-date
2398]]></artwork></figure>
2399<t>
2400   An example is
2401</t>
2402<figure><artwork type="example"><![CDATA[
2403  Date: Tue, 15 Nov 1994 08:12:31 GMT
2404]]></artwork></figure>
2405<t>
2406   Origin servers MUST include a Date header field in all responses,
2407   except in these cases:
2408  <list style="numbers">
2409      <t>If the response status code is 100 (Continue) or 101 (Switching
2410         Protocols), the response MAY include a Date header field, at
2411         the server's option.</t>
2412
2413      <t>If the response status code conveys a server error, e.g., 500
2414         (Internal Server Error) or 503 (Service Unavailable), and it is
2415         inconvenient or impossible to generate a valid Date.</t>
2416
2417      <t>If the server does not have a clock that can provide a
2418         reasonable approximation of the current time, its responses
2419         MUST NOT include a Date header field.</t>
2420  </list>
2421</t>
2422<t>
2423   A received message that does not have a Date header field MUST be
2424   assigned one by the recipient if the message will be cached by that
2425   recipient.
2426</t>
2427<t>
2428   Clients can use the Date header field as well; in order to keep request
2429   messages small, they are advised not to include it when it doesn't convey
2430   any useful information (as it is usually the case for requests that do not
2431   contain a payload).
2432</t>
2433<t>
2434   The HTTP-date sent in a Date header field SHOULD NOT represent a date and
2435   time subsequent to the generation of the message. It SHOULD represent
2436   the best available approximation of the date and time of message
2437   generation, unless the implementation has no means of generating a
2438   reasonably accurate date and time. In theory, the date ought to
2439   represent the moment just before the payload is generated. In
2440   practice, the date can be generated at any time during the message
2441   origination without affecting its semantic value.
2442</t>
2443</section>
2444
2445<section title="Expect" anchor="header.expect">
2446  <iref primary="true" item="Expect header field"/>
2447  <iref primary="true" item="Header Fields" subitem="Expect"/>
2448 
2449 
2450 
2451 
2452<t>
2453   The "Expect" header field is used to indicate that particular
2454   server behaviors are required by the client.
2455</t>
2456<figure><iref primary="true" item="Grammar" subitem="Expect"/><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[
2457  Expect       = 1#expectation
2458 
2459  expectation  = "100-continue" / expectation-extension
2460  expectation-extension = token [ "=" ( token / quoted-string )
2461                           *expect-params ]
2462  expect-params = ";" token [ "=" ( token / quoted-string ) ]
2463]]></artwork></figure>
2464<t>
2465   A server that does not understand or is unable to comply with any of
2466   the expectation values in the Expect field of a request MUST respond
2467   with appropriate error status code. The server MUST respond with a 417
2468   (Expectation Failed) status code if any of the expectations cannot be met
2469   or, if there are other problems with the request, some other 4xx
2470   status code.
2471</t>
2472<t>
2473   This header field is defined with extensible syntax to allow for
2474   future extensions. If a server receives a request containing an
2475   Expect field that includes an expectation-extension that it does not
2476   support, it MUST respond with a 417 (Expectation Failed) status code.
2477</t>
2478<t>
2479   Comparison of expectation values is case-insensitive for unquoted
2480   tokens (including the 100-continue token), and is case-sensitive for
2481   quoted-string expectation-extensions.
2482</t>
2483<t>
2484   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy MUST
2485   return a 417 (Expectation Failed) status code if it receives a request
2486   with an expectation that it cannot meet. However, the Expect
2487   header field itself is end-to-end; it MUST be forwarded if the
2488   request is forwarded.
2489</t>
2490<t>
2491   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
2492   Expect header field.
2493</t>
2494<t>
2495   See Section 6.2.3 of <xref target="Part1"/> for the use of the 100 (Continue) status code.
2496</t>
2497</section>
2498
2499<section title="From" anchor="header.from">
2500  <iref primary="true" item="From header field"/>
2501  <iref primary="true" item="Header Fields" subitem="From"/>
2502 
2503 
2504<t>
2505   The "From" header field, if given, SHOULD contain an Internet
2506   e-mail address for the human user who controls the requesting user
2507   agent. The address SHOULD be machine-usable, as defined by "mailbox"
2508   in Section 3.4 of <xref target="RFC5322"/>:
2509</t>
2510<figure><iref primary="true" item="Grammar" subitem="From"/><artwork type="abnf2616"><![CDATA[
2511  From    = mailbox
2512 
2513  mailbox = <mailbox, defined in [RFC5322], Section 3.4>
2514]]></artwork></figure>
2515<t>
2516   An example is:
2517</t>
2518<figure><artwork type="example"><![CDATA[
2519  From: webmaster@example.org
2520]]></artwork></figure>
2521<t>
2522   This header field MAY be used for logging purposes and as a means for
2523   identifying the source of invalid or unwanted requests. It SHOULD NOT
2524   be used as an insecure form of access protection. The interpretation
2525   of this field is that the request is being performed on behalf of the
2526   person given, who accepts responsibility for the method performed. In
2527   particular, robot agents SHOULD include this header field so that the
2528   person responsible for running the robot can be contacted if problems
2529   occur on the receiving end.
2530</t>
2531<t>
2532   The Internet e-mail address in this field MAY be separate from the
2533   Internet host which issued the request. For example, when a request
2534   is passed through a proxy the original issuer's address SHOULD be
2535   used.
2536</t>
2537<t>
2538   The client SHOULD NOT  send the From header field without the user's
2539   approval, as it might conflict with the user's privacy interests or
2540   their site's security policy. It is strongly recommended that the
2541   user be able to disable, enable, and modify the value of this field
2542   at any time prior to a request.
2543</t>
2544</section>
2545
2546<section title="Location" anchor="header.location">
2547  <iref primary="true" item="Location header field"/>
2548  <iref primary="true" item="Header Fields" subitem="Location"/>
2549 
2550<t>
2551   The "Location" header field is used to identify a newly created
2552   resource, or to redirect the recipient to a different location for
2553   completion of the request.
2554</t>
2555<t>
2556   For 201 (Created) responses, the Location is the URI of the new resource
2557   which was created by the request. For 3xx responses, the location SHOULD
2558   indicate the server's preferred URI for automatic redirection to the
2559   resource.
2560</t>
2561<t>
2562   The field value consists of a single URI-reference. When it has the form
2563   of a relative reference (<xref target="RFC3986"/>, Section 4.2),
2564   the final value is computed by resolving it against the effective request
2565   URI (<xref target="RFC3986"/>, Section 5).
2566</t>
2567<figure><iref primary="true" item="Grammar" subitem="Location"/><artwork type="abnf2616"><![CDATA[
2568  Location = URI-reference
2569]]></artwork></figure>
2570<figure>
2571<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical spacing below, it's necessary this way for xml2rfc-->
2572<artwork type="example"><![CDATA[
2573  Location: http://www.example.org/pub/WWW/People.html#tim
2574]]></artwork></figure><figure><artwork type="example"><![CDATA[  Location: /index.html
2575]]></artwork></figure>
2576<t>
2577   There are circumstances in which a fragment identifier in a Location URI
2578   would not be appropriate. For instance, when it appears in a 201 Created
2579   response, where the Location header field specifies the URI for the entire
2580   created resource.
2581</t>
2582<t><list>
2583  <t>
2584    Note: This specification does not define precedence rules
2585    for the case where the original URI, as navigated to by the user
2586    agent, and the Location header field value both contain fragment
2587    identifiers. Thus be aware that including fragment identifiers might
2588    inconvenience anyone relying on the semantics of the original URI's
2589    fragment identifier.
2590  </t>
2591</list></t>
2592<t><list>
2593  <t>
2594    Note: The Content-Location header field (Section 6.7 of <xref target="Part3"/>) differs
2595    from Location in that the Content-Location identifies the most specific
2596    resource corresponding to the enclosed representation.
2597    It is therefore possible for a response to contain header fields for
2598    both Location and Content-Location.
2599  </t>
2600</list></t>
2601</section>
2602
2603<section title="Max-Forwards" anchor="header.max-forwards">
2604  <iref primary="true" item="Max-Forwards header field"/>
2605  <iref primary="true" item="Header Fields" subitem="Max-Forwards"/>
2606 
2607<t>
2608   The "Max-Forwards" header field provides a mechanism with the
2609   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2610   methods to limit the number of times that the request is forwarded by
2611   proxies. This can be useful when the client is attempting to
2612   trace a request which appears to be failing or looping in mid-chain.
2613</t>
2614<figure><iref primary="true" item="Grammar" subitem="Max-Forwards"/><artwork type="abnf2616"><![CDATA[
2615  Max-Forwards = 1*DIGIT
2616]]></artwork></figure>
2617<t>
2618   The Max-Forwards value is a decimal integer indicating the remaining
2619   number of times this request message can be forwarded.
2620</t>
2621<t>
2622   Each recipient of a TRACE or OPTIONS request
2623   containing a Max-Forwards header field MUST check and update its
2624   value prior to forwarding the request. If the received value is zero
2625   (0), the recipient MUST NOT forward the request; instead, it MUST
2626   respond as the final recipient. If the received Max-Forwards value is
2627   greater than zero, then the forwarded message MUST contain an updated
2628   Max-Forwards field with a value decremented by one (1).
2629</t>
2630<t>
2631   The Max-Forwards header field MAY be ignored for all other request
2632   methods.
2633</t>
2634</section>
2635
2636<section title="Referer" anchor="header.referer">
2637  <iref primary="true" item="Referer header field"/>
2638  <iref primary="true" item="Header Fields" subitem="Referer"/>
2639 
2640<t>
2641   The "Referer" [sic] header field allows the client to specify the
2642   URI of the resource from which the effective request URI was obtained (the
2643   "referrer", although the header field is misspelled.).
2644</t>
2645<t>
2646   The Referer header field allows servers to generate lists of back-links to
2647   resources for interest, logging, optimized caching, etc. It also allows
2648   obsolete or mistyped links to be traced for maintenance. Some servers use
2649   Referer as a means of controlling where they allow links from (so-called
2650   "deep linking"), but legitimate requests do not always
2651   contain a Referer header field.
2652</t>
2653<t>
2654   If the effective request URI was obtained from a source that does not have its own
2655   URI (e.g., input from the user keyboard), the Referer field MUST either be
2656   sent with the value "about:blank", or not be sent at all. Note that this
2657   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2658</t>
2659<figure><iref primary="true" item="Grammar" subitem="Referer"/><artwork type="abnf2616"><![CDATA[
2660  Referer = absolute-URI / partial-URI
2661]]></artwork></figure>
2662<t>
2663   Example:
2664</t>
2665<figure><artwork type="example"><![CDATA[
2666  Referer: http://www.example.org/hypertext/Overview.html
2667]]></artwork></figure>
2668<t>
2669   If the field value is a relative URI, it SHOULD be interpreted
2670   relative to the effective request URI. The URI MUST NOT include a fragment. See
2671   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2672</t>
2673</section>
2674
2675<section title="Retry-After" anchor="header.retry-after">
2676  <iref primary="true" item="Retry-After header field"/>
2677  <iref primary="true" item="Header Fields" subitem="Retry-After"/>
2678 
2679<t>
2680   The header "Retry-After" field can be used with a 503 (Service
2681   Unavailable) response to indicate how long the service is expected to
2682   be unavailable to the requesting client. This field MAY also be used
2683   with any 3xx (Redirection) response to indicate the minimum time the
2684   user-agent is asked wait before issuing the redirected request.
2685</t>
2686<t>
2687   The value of this field can be either an HTTP-date or an integer number
2688   of seconds (in decimal) after the time of the response.
2689</t>
2690<figure><iref primary="true" item="Grammar" subitem="Retry-After"/><artwork type="abnf2616"><![CDATA[
2691  Retry-After = HTTP-date / delta-seconds
2692]]></artwork></figure>
2693<t anchor="rule.delta-seconds">
2694 
2695   Time spans are non-negative decimal integers, representing time in
2696   seconds.
2697</t>
2698<figure><iref primary="true" item="Grammar" subitem="delta-seconds"/><artwork type="abnf2616"><![CDATA[
2699  delta-seconds  = 1*DIGIT
2700]]></artwork></figure>
2701<t>
2702   Two examples of its use are
2703</t>
2704<figure><artwork type="example"><![CDATA[
2705  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2706  Retry-After: 120
2707]]></artwork></figure>
2708<t>
2709   In the latter example, the delay is 2 minutes.
2710</t>
2711</section>
2712
2713<section title="Server" anchor="header.server">
2714  <iref primary="true" item="Server header field"/>
2715  <iref primary="true" item="Header Fields" subitem="Server"/>
2716 
2717<t>
2718   The "Server" header field contains information about the
2719   software used by the origin server to handle the request.
2720</t>
2721<t>
2722   The field can contain multiple product tokens (Section 5.2 of <xref target="Part1"/>) and
2723   comments (Section 3.2 of <xref target="Part1"/>) identifying the server and any significant
2724   subproducts. The product tokens are listed in order of their significance
2725   for identifying the application.
2726</t>
2727<figure><iref primary="true" item="Grammar" subitem="Server"/><artwork type="abnf2616"><![CDATA[
2728  Server = product *( RWS ( product / comment ) )
2729]]></artwork></figure>
2730<t>
2731   Example:
2732</t>
2733<figure><artwork type="example"><![CDATA[
2734  Server: CERN/3.0 libwww/2.17
2735]]></artwork></figure>
2736<t>
2737   If the response is being forwarded through a proxy, the proxy
2738   application MUST NOT modify the Server header field. Instead, it
2739   MUST include a Via field (as described in Section 8.8 of <xref target="Part1"/>).
2740</t>
2741<t><list>
2742  <t>
2743    Note: Revealing the specific software version of the server might
2744    allow the server machine to become more vulnerable to attacks
2745    against software that is known to contain security holes. Server
2746    implementors are encouraged to make this field a configurable
2747    option.
2748  </t>
2749</list></t>
2750</section>
2751
2752<section title="User-Agent" anchor="header.user-agent">
2753  <iref primary="true" item="User-Agent header field"/>
2754  <iref primary="true" item="Header Fields" subitem="User-Agent"/>
2755 
2756<t>
2757   The "User-Agent" header field contains information about the user
2758   agent originating the request. User agents SHOULD include this field with
2759   requests.
2760</t>
2761<t>
2762   Typically, it is used for statistical purposes, the tracing of protocol
2763   violations, and tailoring responses to avoid particular user agent
2764   limitations.
2765</t>
2766<t>
2767   The field can contain multiple product tokens (Section 5.2 of <xref target="Part1"/>)
2768   and comments (Section 3.2 of <xref target="Part1"/>) identifying the agent and its
2769   significant subproducts. By convention, the product tokens are listed in
2770   order of their significance for identifying the application.
2771</t>
2772<t>
2773   Because this field is usually sent on every request a user agent makes,
2774   implementations are encouraged not to include needlessly fine-grained
2775   detail, and to limit (or even prohibit) the addition of subproducts by third
2776   parties. Overly long and detailed User-Agent field values make requests
2777   larger and can also be used to identify ("fingerprint") the user against
2778   their wishes.
2779</t>
2780<t>
2781   Likewise, implementations are encouraged not to use the product tokens of
2782   other implementations in order to declare compatibility with them, as this
2783   circumvents the purpose of the field. Finally, they are encouraged not to
2784   use comments to identify products; doing so makes the field value more
2785   difficult to parse.
2786</t>
2787<figure><iref primary="true" item="Grammar" subitem="User-Agent"/><artwork type="abnf2616"><![CDATA[
2788  User-Agent = product *( RWS ( product / comment ) )
2789]]></artwork></figure>
2790<t>
2791   Example:
2792</t>
2793<figure><artwork type="example"><![CDATA[
2794  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2795]]></artwork></figure>
2796</section>
2797
2798</section>
2799
2800<section title="IANA Considerations" anchor="IANA.considerations">
2801
2802<section title="Method Registry" anchor="method.registration">
2803<t>
2804  The registration procedure for HTTP request methods is defined by
2805  <xref target="method.registry"/> of this document.
2806</t>
2807<t>
2808   The HTTP Method Registry shall be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2809   and be populated with the registrations below:
2810</t>
2811
2812<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2813<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2814   <ttcol>Method</ttcol>
2815   <ttcol>Safe</ttcol>
2816   <ttcol>Reference</ttcol>
2817   <c>CONNECT</c>
2818   <c>no</c>
2819   <c>
2820      <xref target="CONNECT"/>
2821   </c>
2822   <c>DELETE</c>
2823   <c>no</c>
2824   <c>
2825      <xref target="DELETE"/>
2826   </c>
2827   <c>GET</c>
2828   <c>yes</c>
2829   <c>
2830      <xref target="GET"/>
2831   </c>
2832   <c>HEAD</c>
2833   <c>yes</c>
2834   <c>
2835      <xref target="HEAD"/>
2836   </c>
2837   <c>OPTIONS</c>
2838   <c>yes</c>
2839   <c>
2840      <xref target="OPTIONS"/>
2841   </c>
2842   <c>POST</c>
2843   <c>no</c>
2844   <c>
2845      <xref target="POST"/>
2846   </c>
2847   <c>PUT</c>
2848   <c>no</c>
2849   <c>
2850      <xref target="PUT"/>
2851   </c>
2852   <c>TRACE</c>
2853   <c>yes</c>
2854   <c>
2855      <xref target="TRACE"/>
2856   </c>
2857</texttable>
2858<!--(END)-->
2859
2860</section>
2861
2862<section title="Status Code Registry" anchor="status.code.registration">
2863<t>
2864   The registration procedure for HTTP Status Codes — previously defined
2865   in Section 7.1 of <xref target="RFC2817"/> — is now defined
2866   by <xref target="status.code.registry"/> of this document.
2867</t>
2868<t>
2869   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2870   shall be updated with the registrations below:
2871</t>
2872
2873<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2874<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2875   <ttcol>Value</ttcol>
2876   <ttcol>Description</ttcol>
2877   <ttcol>Reference</ttcol>
2878   <c>100</c>
2879   <c>Continue</c>
2880   <c>
2881      <xref target="status.100"/>
2882   </c>
2883   <c>101</c>
2884   <c>Switching Protocols</c>
2885   <c>
2886      <xref target="status.101"/>
2887   </c>
2888   <c>200</c>
2889   <c>OK</c>
2890   <c>
2891      <xref target="status.200"/>
2892   </c>
2893   <c>201</c>
2894   <c>Created</c>
2895   <c>
2896      <xref target="status.201"/>
2897   </c>
2898   <c>202</c>
2899   <c>Accepted</c>
2900   <c>
2901      <xref target="status.202"/>
2902   </c>
2903   <c>203</c>
2904   <c>Non-Authoritative Information</c>
2905   <c>
2906      <xref target="status.203"/>
2907   </c>
2908   <c>204</c>
2909   <c>No Content</c>
2910   <c>
2911      <xref target="status.204"/>
2912   </c>
2913   <c>205</c>
2914   <c>Reset Content</c>
2915   <c>
2916      <xref target="status.205"/>
2917   </c>
2918   <c>300</c>
2919   <c>Multiple Choices</c>
2920   <c>
2921      <xref target="status.300"/>
2922   </c>
2923   <c>301</c>
2924   <c>Moved Permanently</c>
2925   <c>
2926      <xref target="status.301"/>
2927   </c>
2928   <c>302</c>
2929   <c>Found</c>
2930   <c>
2931      <xref target="status.302"/>
2932   </c>
2933   <c>303</c>
2934   <c>See Other</c>
2935   <c>
2936      <xref target="status.303"/>
2937   </c>
2938   <c>305</c>
2939   <c>Use Proxy</c>
2940   <c>
2941      <xref target="status.305"/>
2942   </c>
2943   <c>306</c>
2944   <c>(Unused)</c>
2945   <c>
2946      <xref target="status.306"/>
2947   </c>
2948   <c>307</c>
2949   <c>Temporary Redirect</c>
2950   <c>
2951      <xref target="status.307"/>
2952   </c>
2953   <c>400</c>
2954   <c>Bad Request</c>
2955   <c>
2956      <xref target="status.400"/>
2957   </c>
2958   <c>402</c>
2959   <c>Payment Required</c>
2960   <c>
2961      <xref target="status.402"/>
2962   </c>
2963   <c>403</c>
2964   <c>Forbidden</c>
2965   <c>
2966      <xref target="status.403"/>
2967   </c>
2968   <c>404</c>
2969   <c>Not Found</c>
2970   <c>
2971      <xref target="status.404"/>
2972   </c>
2973   <c>405</c>
2974   <c>Method Not Allowed</c>
2975   <c>
2976      <xref target="status.405"/>
2977   </c>
2978   <c>406</c>
2979   <c>Not Acceptable</c>
2980   <c>
2981      <xref target="status.406"/>
2982   </c>
2983   <c>407</c>
2984   <c>Proxy Authentication Required</c>
2985   <c>
2986      <xref target="status.407"/>
2987   </c>
2988   <c>408</c>
2989   <c>Request Timeout</c>
2990   <c>
2991      <xref target="status.408"/>
2992   </c>
2993   <c>409</c>
2994   <c>Conflict</c>
2995   <c>
2996      <xref target="status.409"/>
2997   </c>
2998   <c>410</c>
2999   <c>Gone</c>
3000   <c>
3001      <xref target="status.410"/>
3002   </c>
3003   <c>411</c>
3004   <c>Length Required</c>
3005   <c>
3006      <xref target="status.411"/>
3007   </c>
3008   <c>413</c>
3009   <c>Request Representation Too Large</c>
3010   <c>
3011      <xref target="status.413"/>
3012   </c>
3013   <c>414</c>
3014   <c>URI Too Long</c>
3015   <c>
3016      <xref target="status.414"/>
3017   </c>
3018   <c>415</c>
3019   <c>Unsupported Media Type</c>
3020   <c>
3021      <xref target="status.415"/>
3022   </c>
3023   <c>417</c>
3024   <c>Expectation Failed</c>
3025   <c>
3026      <xref target="status.417"/>
3027   </c>
3028   <c>426</c>
3029   <c>Upgrade Required</c>
3030   <c>
3031      <xref target="status.426"/>
3032   </c>
3033   <c>500</c>
3034   <c>Internal Server Error</c>
3035   <c>
3036      <xref target="status.500"/>
3037   </c>
3038   <c>501</c>
3039   <c>Not Implemented</c>
3040   <c>
3041      <xref target="status.501"/>
3042   </c>
3043   <c>502</c>
3044   <c>Bad Gateway</c>
3045   <c>
3046      <xref target="status.502"/>
3047   </c>
3048   <c>503</c>
3049   <c>Service Unavailable</c>
3050   <c>
3051      <xref target="status.503"/>
3052   </c>
3053   <c>504</c>
3054   <c>Gateway Timeout</c>
3055   <c>
3056      <xref target="status.504"/>
3057   </c>
3058   <c>505</c>
3059   <c>HTTP Version Not Supported</c>
3060   <c>
3061      <xref target="status.505"/>
3062   </c>
3063</texttable>
3064<!--(END)-->
3065
3066</section>
3067<section title="Header Field Registration" anchor="header.field.registration">
3068<t>
3069   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
3070   with the permanent registrations below (see <xref target="RFC3864"/>):
3071</t>
3072
3073<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
3074<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
3075   <ttcol>Header Field Name</ttcol>
3076   <ttcol>Protocol</ttcol>
3077   <ttcol>Status</ttcol>
3078   <ttcol>Reference</ttcol>
3079
3080   <c>Allow</c>
3081   <c>http</c>
3082   <c>standard</c>
3083   <c>
3084      <xref target="header.allow"/>
3085   </c>
3086   <c>Date</c>
3087   <c>http</c>
3088   <c>standard</c>
3089   <c>
3090      <xref target="header.date"/>
3091   </c>
3092   <c>Expect</c>
3093   <c>http</c>
3094   <c>standard</c>
3095   <c>
3096      <xref target="header.expect"/>
3097   </c>
3098   <c>From</c>
3099   <c>http</c>
3100   <c>standard</c>
3101   <c>
3102      <xref target="header.from"/>
3103   </c>
3104   <c>Location</c>
3105   <c>http</c>
3106   <c>standard</c>
3107   <c>
3108      <xref target="header.location"/>
3109   </c>
3110   <c>Max-Forwards</c>
3111   <c>http</c>
3112   <c>standard</c>
3113   <c>
3114      <xref target="header.max-forwards"/>
3115   </c>
3116   <c>Referer</c>
3117   <c>http</c>
3118   <c>standard</c>
3119   <c>
3120      <xref target="header.referer"/>
3121   </c>
3122   <c>Retry-After</c>
3123   <c>http</c>
3124   <c>standard</c>
3125   <c>
3126      <xref target="header.retry-after"/>
3127   </c>
3128   <c>Server</c>
3129   <c>http</c>
3130   <c>standard</c>
3131   <c>
3132      <xref target="header.server"/>
3133   </c>
3134   <c>User-Agent</c>
3135   <c>http</c>
3136   <c>standard</c>
3137   <c>
3138      <xref target="header.user-agent"/>
3139   </c>
3140</texttable>
3141<!--(END)-->
3142
3143<t>
3144   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
3145</t>
3146</section>
3147</section>
3148
3149<section title="Security Considerations" anchor="security.considerations">
3150<t>
3151   This section is meant to inform application developers, information
3152   providers, and users of the security limitations in HTTP/1.1 as
3153   described by this document. The discussion does not include
3154   definitive solutions to the problems revealed, though it does make
3155   some suggestions for reducing security risks.
3156</t>
3157
3158<section title="Transfer of Sensitive Information" anchor="security.sensitive">
3159<t>
3160   Like any generic data transfer protocol, HTTP cannot regulate the
3161   content of the data that is transferred, nor is there any a priori
3162   method of determining the sensitivity of any particular piece of
3163   information within the context of any given request. Therefore,
3164   applications SHOULD supply as much control over this information as
3165   possible to the provider of that information. Four header fields are
3166   worth special mention in this context: Server, Via, Referer and From.
3167</t>
3168<t>
3169   Revealing the specific software version of the server might allow the
3170   server machine to become more vulnerable to attacks against software
3171   that is known to contain security holes. Implementors SHOULD make the
3172   Server header field a configurable option.
3173</t>
3174<t>
3175   Proxies which serve as a portal through a network firewall SHOULD
3176   take special precautions regarding the transfer of header information
3177   that identifies the hosts behind the firewall. In particular, they
3178   SHOULD remove, or replace with sanitized versions, any Via fields
3179   generated behind the firewall.
3180</t>
3181<t>
3182   The Referer header field allows reading patterns to be studied and reverse
3183   links drawn. Although it can be very useful, its power can be abused
3184   if user details are not separated from the information contained in
3185   the Referer. Even when the personal information has been removed, the
3186   Referer header field might indicate a private document's URI whose
3187   publication would be inappropriate.
3188</t>
3189<t>
3190   The information sent in the From field might conflict with the user's
3191   privacy interests or their site's security policy, and hence it
3192   SHOULD NOT  be transmitted without the user being able to disable,
3193   enable, and modify the contents of the field. The user MUST be able
3194   to set the contents of this field within a user preference or
3195   application defaults configuration.
3196</t>
3197<t>
3198   We suggest, though do not require, that a convenient toggle interface
3199   be provided for the user to enable or disable the sending of From and
3200   Referer information.
3201</t>
3202<t>
3203   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header fields can sometimes be used to determine
3204   that a specific client or server have a particular security hole which might
3205   be exploited. Unfortunately, this same information is often used for other
3206   valuable purposes for which HTTP currently has no better mechanism.
3207</t>
3208<t>
3209   Furthermore, the User-Agent header field may contain enough entropy to be
3210   used, possibly in conjunction with other material, to uniquely identify the
3211   user.
3212</t>
3213<t>
3214   Some request methods, like TRACE (<xref target="TRACE"/>), expose information
3215   that was sent in request header fields within the body of their response.
3216   Clients SHOULD be careful with sensitive information, like Cookies,
3217   Authorization credentials, and other header fields that might be used to
3218   collect data from the client.
3219</t> 
3220</section>
3221
3222<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
3223<t>
3224   Because the source of a link might be private information or might
3225   reveal an otherwise private information source, it is strongly
3226   recommended that the user be able to select whether or not the
3227   Referer field is sent. For example, a browser client could have a
3228   toggle switch for browsing openly/anonymously, which would
3229   respectively enable/disable the sending of Referer and From
3230   information.
3231</t>
3232<t>
3233   Clients SHOULD NOT include a Referer header field in a (non-secure)
3234   HTTP request if the referring page was transferred with a secure
3235   protocol.
3236</t>
3237<t>
3238   Authors of services SHOULD NOT use GET-based forms for the submission of
3239   sensitive data because that data will be placed in the request-target. Many
3240   existing servers, proxies, and user agents log or display the request-target
3241   in places where it might be visible to third parties. Such services can
3242   use POST-based form submission instead.
3243</t>
3244</section>
3245
3246<section title="Location Headers and Spoofing" anchor="location.spoofing">
3247<t>
3248   If a single server supports multiple organizations that do not trust
3249   one another, then it MUST check the values of Location and Content-Location
3250   header fields in responses that are generated under control of
3251   said organizations to make sure that they do not attempt to
3252   invalidate resources over which they have no authority.
3253</t>
3254</section>
3255
3256<section title="Security Considerations for CONNECT">
3257<t>
3258   Since tunneled data is opaque to the proxy, there are additional
3259   risks to tunneling to other well-known or reserved ports.
3260   A HTTP client CONNECTing to port 25 could relay spam
3261   via SMTP, for example. As such, proxies SHOULD restrict CONNECT
3262   access to a small number of known ports.
3263</t>
3264</section>
3265
3266</section>
3267
3268<section title="Acknowledgments" anchor="acks">
3269<t>
3270  See Section 11 of <xref target="Part1"/>.
3271</t>
3272</section>
3273</middle>
3274<back>
3275
3276<references title="Normative References">
3277
3278<reference anchor="Part1">
3279  <front>
3280    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
3281    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3282      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3283      <address><email>fielding@gbiv.com</email></address>
3284    </author>
3285    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3286      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3287      <address><email>jg@freedesktop.org</email></address>
3288    </author>
3289    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3290      <organization abbrev="HP">Hewlett-Packard Company</organization>
3291      <address><email>JeffMogul@acm.org</email></address>
3292    </author>
3293    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3294      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3295      <address><email>henrikn@microsoft.com</email></address>
3296    </author>
3297    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3298      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3299      <address><email>LMM@acm.org</email></address>
3300    </author>
3301    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3302      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3303      <address><email>paulle@microsoft.com</email></address>
3304    </author>
3305    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3306      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3307      <address><email>timbl@w3.org</email></address>
3308    </author>
3309    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3310      <organization abbrev="W3C">World Wide Web Consortium</organization>
3311      <address><email>ylafon@w3.org</email></address>
3312    </author>
3313    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3314      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3315      <address><email>julian.reschke@greenbytes.de</email></address>
3316    </author>
3317    <date month="October" year="2011"/>
3318  </front>
3319  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-17"/>
3320 
3321</reference>
3322
3323<reference anchor="Part3">
3324  <front>
3325    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
3326    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3327      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3328      <address><email>fielding@gbiv.com</email></address>
3329    </author>
3330    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3331      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3332      <address><email>jg@freedesktop.org</email></address>
3333    </author>
3334    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3335      <organization abbrev="HP">Hewlett-Packard Company</organization>
3336      <address><email>JeffMogul@acm.org</email></address>
3337    </author>
3338    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3339      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3340      <address><email>henrikn@microsoft.com</email></address>
3341    </author>
3342    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3343      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3344      <address><email>LMM@acm.org</email></address>
3345    </author>
3346    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3347      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3348      <address><email>paulle@microsoft.com</email></address>
3349    </author>
3350    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3351      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3352      <address><email>timbl@w3.org</email></address>
3353    </author>
3354    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3355      <organization abbrev="W3C">World Wide Web Consortium</organization>
3356      <address><email>ylafon@w3.org</email></address>
3357    </author>
3358    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3359      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3360      <address><email>julian.reschke@greenbytes.de</email></address>
3361    </author>
3362    <date month="October" year="2011"/>
3363  </front>
3364  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-17"/>
3365 
3366</reference>
3367
3368<reference anchor="Part4">
3369  <front>
3370    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
3371    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3372      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3373      <address><email>fielding@gbiv.com</email></address>
3374    </author>
3375    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3376      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3377      <address><email>jg@freedesktop.org</email></address>
3378    </author>
3379    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3380      <organization abbrev="HP">Hewlett-Packard Company</organization>
3381      <address><email>JeffMogul@acm.org</email></address>
3382    </author>
3383    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3384      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3385      <address><email>henrikn@microsoft.com</email></address>
3386    </author>
3387    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3388      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3389      <address><email>LMM@acm.org</email></address>
3390    </author>
3391    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3392      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3393      <address><email>paulle@microsoft.com</email></address>
3394    </author>
3395    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3396      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3397      <address><email>timbl@w3.org</email></address>
3398    </author>
3399    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3400      <organization abbrev="W3C">World Wide Web Consortium</organization>
3401      <address><email>ylafon@w3.org</email></address>
3402    </author>
3403    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3404      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3405      <address><email>julian.reschke@greenbytes.de</email></address>
3406    </author>
3407    <date month="October" year="2011"/>
3408  </front>
3409  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-17"/>
3410 
3411</reference>
3412
3413<reference anchor="Part5">
3414  <front>
3415    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
3416    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3417      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3418      <address><email>fielding@gbiv.com</email></address>
3419    </author>
3420    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3421      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3422      <address><email>jg@freedesktop.org</email></address>
3423    </author>
3424    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3425      <organization abbrev="HP">Hewlett-Packard Company</organization>
3426      <address><email>JeffMogul@acm.org</email></address>
3427    </author>
3428    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3429      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3430      <address><email>henrikn@microsoft.com</email></address>
3431    </author>
3432    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3433      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3434      <address><email>LMM@acm.org</email></address>
3435    </author>
3436    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3437      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3438      <address><email>paulle@microsoft.com</email></address>
3439    </author>
3440    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3441      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3442      <address><email>timbl@w3.org</email></address>
3443    </author>
3444    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3445      <organization abbrev="W3C">World Wide Web Consortium</organization>
3446      <address><email>ylafon@w3.org</email></address>
3447    </author>
3448    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3449      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3450      <address><email>julian.reschke@greenbytes.de</email></address>
3451    </author>
3452    <date month="October" year="2011"/>
3453  </front>
3454  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-17"/>
3455 
3456</reference>
3457
3458<reference anchor="Part6">
3459  <front>
3460    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
3461    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3462      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3463      <address><email>fielding@gbiv.com</email></address>
3464    </author>
3465    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3466      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3467      <address><email>jg@freedesktop.org</email></address>
3468    </author>
3469    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3470      <organization abbrev="HP">Hewlett-Packard Company</organization>
3471      <address><email>JeffMogul@acm.org</email></address>
3472    </author>
3473    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3474      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3475      <address><email>henrikn@microsoft.com</email></address>
3476    </author>
3477    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3478      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3479      <address><email>LMM@acm.org</email></address>
3480    </author>
3481    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3482      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3483      <address><email>paulle@microsoft.com</email></address>
3484    </author>
3485    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3486      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3487      <address><email>timbl@w3.org</email></address>
3488    </author>
3489    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3490      <organization abbrev="W3C">World Wide Web Consortium</organization>
3491      <address><email>ylafon@w3.org</email></address>
3492    </author>
3493    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
3494      <organization>Rackspace</organization>
3495      <address><email>mnot@mnot.net</email></address>
3496    </author>
3497    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3498      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3499      <address><email>julian.reschke@greenbytes.de</email></address>
3500    </author>
3501    <date month="October" year="2011"/>
3502  </front>
3503  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-17"/>
3504 
3505</reference>
3506
3507<reference anchor="Part7">
3508  <front>
3509    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
3510    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3511      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3512      <address><email>fielding@gbiv.com</email></address>
3513    </author>
3514    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3515      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3516      <address><email>jg@freedesktop.org</email></address>
3517    </author>
3518    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3519      <organization abbrev="HP">Hewlett-Packard Company</organization>
3520      <address><email>JeffMogul@acm.org</email></address>
3521    </author>
3522    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3523      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3524      <address><email>henrikn@microsoft.com</email></address>
3525    </author>
3526    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3527      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3528      <address><email>LMM@acm.org</email></address>
3529    </author>
3530    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3531      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3532      <address><email>paulle@microsoft.com</email></address>
3533    </author>
3534    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3535      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3536      <address><email>timbl@w3.org</email></address>
3537    </author>
3538    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3539      <organization abbrev="W3C">World Wide Web Consortium</organization>
3540      <address><email>ylafon@w3.org</email></address>
3541    </author>
3542    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3543      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3544      <address><email>julian.reschke@greenbytes.de</email></address>
3545    </author>
3546    <date month="October" year="2011"/>
3547  </front>
3548  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-17"/>
3549 
3550</reference>
3551
3552<reference anchor="RFC2119">
3553  <front>
3554    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3555    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3556      <organization>Harvard University</organization>
3557      <address><email>sob@harvard.edu</email></address>
3558    </author>
3559    <date month="March" year="1997"/>
3560  </front>
3561  <seriesInfo name="BCP" value="14"/>
3562  <seriesInfo name="RFC" value="2119"/>
3563</reference>
3564
3565<reference anchor="RFC3986">
3566 <front>
3567  <title abbrev="URI Generic Syntax">Uniform Resource Identifier (URI): Generic Syntax</title>
3568  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3569    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3570    <address>
3571       <email>timbl@w3.org</email>
3572       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3573    </address>
3574  </author>
3575  <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3576    <organization abbrev="Day Software">Day Software</organization>
3577    <address>
3578      <email>fielding@gbiv.com</email>
3579      <uri>http://roy.gbiv.com/</uri>
3580    </address>
3581  </author>
3582  <author initials="L." surname="Masinter" fullname="Larry Masinter">
3583    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3584    <address>
3585      <email>LMM@acm.org</email>
3586      <uri>http://larry.masinter.net/</uri>
3587    </address>
3588  </author>
3589  <date month="January" year="2005"/>
3590 </front>
3591 <seriesInfo name="STD" value="66"/>
3592 <seriesInfo name="RFC" value="3986"/>
3593</reference>
3594
3595<reference anchor="RFC5234">
3596  <front>
3597    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3598    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3599      <organization>Brandenburg InternetWorking</organization>
3600      <address>
3601        <email>dcrocker@bbiw.net</email>
3602      </address> 
3603    </author>
3604    <author initials="P." surname="Overell" fullname="Paul Overell">
3605      <organization>THUS plc.</organization>
3606      <address>
3607        <email>paul.overell@thus.net</email>
3608      </address>
3609    </author>
3610    <date month="January" year="2008"/>
3611  </front>
3612  <seriesInfo name="STD" value="68"/>
3613  <seriesInfo name="RFC" value="5234"/>
3614</reference>
3615
3616</references>
3617
3618<references title="Informative References">
3619
3620<reference anchor="RFC1123">
3621  <front>
3622    <title>Requirements for Internet Hosts - Application and Support</title>
3623    <author initials="R." surname="Braden" fullname="Robert Braden">
3624      <organization>University of Southern California (USC), Information Sciences Institute</organization>
3625      <address><email>Braden@ISI.EDU</email></address>
3626    </author>
3627    <date month="October" year="1989"/>
3628  </front>
3629  <seriesInfo name="STD" value="3"/>
3630  <seriesInfo name="RFC" value="1123"/>
3631</reference>
3632
3633<reference anchor="RFC1945">
3634  <front>
3635    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3636    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3637      <organization>MIT, Laboratory for Computer Science</organization>
3638      <address><email>timbl@w3.org</email></address>
3639    </author>
3640    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3641      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3642      <address><email>fielding@ics.uci.edu</email></address>
3643    </author>
3644    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3645      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3646      <address><email>frystyk@w3.org</email></address>
3647    </author>
3648    <date month="May" year="1996"/>
3649  </front>
3650  <seriesInfo name="RFC" value="1945"/>
3651</reference>
3652
3653<reference anchor="RFC2068">
3654  <front>
3655    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3656    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3657      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3658      <address><email>fielding@ics.uci.edu</email></address>
3659    </author>
3660    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3661      <organization>MIT Laboratory for Computer Science</organization>
3662      <address><email>jg@w3.org</email></address>
3663    </author>
3664    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3665      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3666      <address><email>mogul@wrl.dec.com</email></address>
3667    </author>
3668    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3669      <organization>MIT Laboratory for Computer Science</organization>
3670      <address><email>frystyk@w3.org</email></address>
3671    </author>
3672    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3673      <organization>MIT Laboratory for Computer Science</organization>
3674      <address><email>timbl@w3.org</email></address>
3675    </author>
3676    <date month="January" year="1997"/>
3677  </front>
3678  <seriesInfo name="RFC" value="2068"/>
3679</reference>
3680
3681<reference anchor="RFC2616">
3682  <front>
3683    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3684    <author initials="R." surname="Fielding" fullname="R. Fielding">
3685      <organization>University of California, Irvine</organization>
3686      <address><email>fielding@ics.uci.edu</email></address>
3687    </author>
3688    <author initials="J." surname="Gettys" fullname="J. Gettys">
3689      <organization>W3C</organization>
3690      <address><email>jg@w3.org</email></address>
3691    </author>
3692    <author initials="J." surname="Mogul" fullname="J. Mogul">
3693      <organization>Compaq Computer Corporation</organization>
3694      <address><email>mogul@wrl.dec.com</email></address>
3695    </author>
3696    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3697      <organization>MIT Laboratory for Computer Science</organization>
3698      <address><email>frystyk@w3.org</email></address>
3699    </author>
3700    <author initials="L." surname="Masinter" fullname="L. Masinter">
3701      <organization>Xerox Corporation</organization>
3702      <address><email>masinter@parc.xerox.com</email></address>
3703    </author>
3704    <author initials="P." surname="Leach" fullname="P. Leach">
3705      <organization>Microsoft Corporation</organization>
3706      <address><email>paulle@microsoft.com</email></address>
3707    </author>
3708    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3709      <organization>W3C</organization>
3710      <address><email>timbl@w3.org</email></address>
3711    </author>
3712    <date month="June" year="1999"/>
3713  </front>
3714  <seriesInfo name="RFC" value="2616"/>
3715</reference>
3716
3717<reference anchor="RFC2817">
3718  <front>
3719    <title>Upgrading to TLS Within HTTP/1.1</title>
3720    <author initials="R." surname="Khare" fullname="R. Khare">
3721      <organization>4K Associates / UC Irvine</organization>
3722      <address><email>rohit@4K-associates.com</email></address>
3723    </author>
3724    <author initials="S." surname="Lawrence" fullname="S. Lawrence">
3725      <organization>Agranat Systems, Inc.</organization>
3726      <address><email>lawrence@agranat.com</email></address>
3727    </author>
3728    <date year="2000" month="May"/>
3729  </front>
3730  <seriesInfo name="RFC" value="2817"/>
3731</reference>
3732
3733<reference anchor="RFC3864">
3734  <front>
3735    <title>Registration Procedures for Message Header Fields</title>
3736    <author initials="G." surname="Klyne" fullname="G. Klyne">
3737      <organization>Nine by Nine</organization>
3738      <address><email>GK-IETF@ninebynine.org</email></address>
3739    </author>
3740    <author initials="M." surname="Nottingham" fullname="M. Nottingham">
3741      <organization>BEA Systems</organization>
3742      <address><email>mnot@pobox.com</email></address>
3743    </author>
3744    <author initials="J." surname="Mogul" fullname="J. Mogul">
3745      <organization>HP Labs</organization>
3746      <address><email>JeffMogul@acm.org</email></address>
3747    </author>
3748    <date year="2004" month="September"/>
3749  </front>
3750  <seriesInfo name="BCP" value="90"/>
3751  <seriesInfo name="RFC" value="3864"/>
3752</reference>
3753
3754<reference anchor="RFC5226">
3755  <front>
3756    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3757    <author initials="T." surname="Narten" fullname="T. Narten">
3758      <organization>IBM</organization>
3759      <address><email>narten@us.ibm.com</email></address>
3760    </author>
3761    <author initials="H." surname="Alvestrand" fullname="H. Alvestrand">
3762      <organization>Google</organization>
3763      <address><email>Harald@Alvestrand.no</email></address>
3764    </author>
3765    <date year="2008" month="May"/>
3766  </front>
3767  <seriesInfo name="BCP" value="26"/>
3768  <seriesInfo name="RFC" value="5226"/>
3769</reference>
3770
3771<reference anchor="RFC5322">
3772  <front>
3773    <title>Internet Message Format</title>
3774    <author initials="P." surname="Resnick" fullname="P. Resnick">
3775      <organization>Qualcomm Incorporated</organization>
3776    </author>
3777    <date year="2008" month="October"/>
3778  </front> 
3779  <seriesInfo name="RFC" value="5322"/>
3780</reference>
3781
3782<reference anchor="RFC5789">
3783  <front>
3784    <title>PATCH Method for HTTP</title>
3785    <author initials="L." surname="Dusseault" fullname="L. Dusseault">
3786      <organization>Linden Lab</organization>
3787    </author>
3788    <author initials="J." surname="Snell" fullname="J. Snell"/>
3789    <date year="2010" month="March"/>
3790  </front>
3791  <seriesInfo name="RFC" value="5789"/>
3792</reference>
3793
3794<reference anchor="RFC5987">
3795        <front>
3796    <title>Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters</title>
3797    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke">
3798      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3799      <address>
3800        <postal>
3801          <street>Hafenweg 16</street>
3802          <city>Muenster</city><region>NW</region><code>48155</code>
3803          <country>Germany</country>
3804        </postal>
3805        <email>julian.reschke@greenbytes.de</email>     
3806        <uri>http://greenbytes.de/tech/webdav/</uri>   
3807      </address>
3808    </author>
3809    <date month="August" year="2010"/>
3810  </front>
3811  <seriesInfo name="RFC" value="5987"/>
3812</reference>
3813
3814</references>
3815
3816<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3817<t>
3818  This document takes over the Status Code Registry, previously defined
3819  in Section 7.1 of <xref target="RFC2817"/>.
3820  (<xref target="status.code.registry"/>)
3821</t>
3822<t>
3823  Clarify definition of POST.
3824  (<xref target="POST"/>)
3825</t>
3826<t>
3827  Remove requirement to handle all Content-* header fields; ban use of
3828  Content-Range with PUT.
3829  (<xref target="PUT"/>)
3830</t>
3831<t>
3832  Take over definition of CONNECT method from <xref target="RFC2817"/>.
3833  (<xref target="CONNECT"/>)
3834</t>
3835<t>
3836  Broadened the definition of 203 (Non-Authoritative Information) to include
3837  cases of payload transformations as well.
3838  (<xref target="status.203"/>)
3839</t>
3840<t>
3841  Failed to consider that there are many other request methods that are safe
3842  to automatically redirect, and further that the user agent is able to make
3843  that determination based on the request method semantics.
3844  Furthermore, allow user agents to rewrite the method from POST to GET
3845  for status codes 301 and 302.
3846  (Sections <xref format="counter" target="status.301"/>,
3847  <xref format="counter" target="status.302"/> and
3848  <xref format="counter" target="status.307"/>)
3849</t>
3850<t>
3851  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3852  It used to indicate that the target resource must be accessed through the
3853  proxy given by the Location field. The Location field gave the URI of the
3854  proxy. The recipient was expected to repeat this single request via the proxy.
3855  (<xref target="status.305"/>)
3856</t>
3857<t>
3858  Define status 426 (Upgrade Required) (this was incorporated from
3859  <xref target="RFC2817"/>).
3860  (<xref target="status.426"/>)
3861</t>
3862<t>
3863  Change ABNF productions for header fields to only define the field value.
3864  (<xref target="header.field.definitions"/>)
3865</t>
3866<t>
3867  Reclassify "Allow" as response header field, removing the option to
3868  specify it in a PUT request.
3869  Relax the server requirement on the contents of the Allow header field and
3870  remove requirement on clients to always trust the header field value.
3871  (<xref target="header.allow"/>)
3872</t>
3873<t>
3874  Correct syntax of Location header field to allow URI references (including
3875  relative references and fragments), as referred symbol "absoluteURI" wasn't
3876  what was expected, and add some clarifications as to when use of fragments
3877  would not be appropriate.
3878  (<xref target="header.location"/>)
3879</t>
3880<t>
3881  Restrict Max-Forwards header field to OPTIONS and TRACE (previously,
3882  extension methods could have used it as well).
3883  (<xref target="header.max-forwards"/>)
3884</t>
3885<t>
3886  Allow Referer field value of "about:blank" as alternative to not specifying it.
3887  (<xref target="header.referer"/>)
3888</t>
3889<t>
3890  In the description of the Server header field, the Via field
3891  was described as a SHOULD. The requirement was and is stated
3892  correctly in the description of the Via header field in Section 8.8 of <xref target="Part1"/>.
3893  (<xref target="header.server"/>)
3894</t>
3895</section>
3896
3897
3898<section title="Collected ABNF" anchor="collected.abnf">
3899<figure>
3900<artwork type="abnf" name="p2-semantics.parsed-abnf"><![CDATA[
3901Allow = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3902
3903Date = HTTP-date
3904
3905Expect = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3906
3907From = mailbox
3908
3909GMT = %x47.4D.54 ; GMT
3910
3911HTTP-date = rfc1123-date / obs-date
3912
3913Location = URI-reference
3914
3915Max-Forwards = 1*DIGIT
3916Method = token
3917
3918OWS = <OWS, defined in [Part1], Section 1.2.2>
3919
3920RWS = <RWS, defined in [Part1], Section 1.2.2>
3921Reason-Phrase = *( HTAB / SP / VCHAR / obs-text )
3922Referer = absolute-URI / partial-URI
3923Retry-After = HTTP-date / delta-seconds
3924
3925Server = product *( RWS ( product / comment ) )
3926Status-Code = 3DIGIT
3927
3928URI-reference = <URI-reference, defined in [Part1], Section 2.7>
3929User-Agent = product *( RWS ( product / comment ) )
3930
3931absolute-URI = <absolute-URI, defined in [Part1], Section 2.7>
3932asctime-date = day-name SP date3 SP time-of-day SP year
3933
3934comment = <comment, defined in [Part1], Section 3.2>
3935
3936date1 = day SP month SP year
3937date2 = day "-" month "-" 2DIGIT
3938date3 = month SP ( 2DIGIT / ( SP DIGIT ) )
3939day = 2DIGIT
3940day-name = %x4D.6F.6E ; Mon
3941 / %x54.75.65 ; Tue
3942 / %x57.65.64 ; Wed
3943 / %x54.68.75 ; Thu
3944 / %x46.72.69 ; Fri
3945 / %x53.61.74 ; Sat
3946 / %x53.75.6E ; Sun
3947day-name-l = %x4D.6F.6E.64.61.79 ; Monday
3948 / %x54.75.65.73.64.61.79 ; Tuesday
3949 / %x57.65.64.6E.65.73.64.61.79 ; Wednesday
3950 / %x54.68.75.72.73.64.61.79 ; Thursday
3951 / %x46.72.69.64.61.79 ; Friday
3952 / %x53.61.74.75.72.64.61.79 ; Saturday
3953 / %x53.75.6E.64.61.79 ; Sunday
3954delta-seconds = 1*DIGIT
3955
3956expect-params = ";" token [ "=" ( token / quoted-string ) ]
3957expectation = "100-continue" / expectation-extension
3958expectation-extension = token [ "=" ( token / quoted-string )
3959 *expect-params ]
3960
3961hour = 2DIGIT
3962
3963mailbox = <mailbox, defined in [RFC5322], Section 3.4>
3964minute = 2DIGIT
3965month = %x4A.61.6E ; Jan
3966 / %x46.65.62 ; Feb
3967 / %x4D.61.72 ; Mar
3968 / %x41.70.72 ; Apr
3969 / %x4D.61.79 ; May
3970 / %x4A.75.6E ; Jun
3971 / %x4A.75.6C ; Jul
3972 / %x41.75.67 ; Aug
3973 / %x53.65.70 ; Sep
3974 / %x4F.63.74 ; Oct
3975 / %x4E.6F.76 ; Nov
3976 / %x44.65.63 ; Dec
3977
3978obs-date = rfc850-date / asctime-date
3979obs-text = <obs-text, defined in [Part1], Section 1.2.2>
3980
3981partial-URI = <partial-URI, defined in [Part1], Section 2.7>
3982product = <product, defined in [Part1], Section 5.2>
3983
3984quoted-string = <quoted-string, defined in [Part1], Section 3.2.3>
3985
3986rfc1123-date = day-name "," SP date1 SP time-of-day SP GMT
3987rfc850-date = day-name-l "," SP date2 SP time-of-day SP GMT
3988
3989second = 2DIGIT
3990
3991time-of-day = hour ":" minute ":" second
3992token = <token, defined in [Part1], Section 3.2.3>
3993
3994year = 4DIGIT
3995]]></artwork>
3996</figure>
3997<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline"><![CDATA[
3998; Allow defined but not used
3999; Date defined but not used
4000; Expect defined but not used
4001; From defined but not used
4002; Location defined but not used
4003; Max-Forwards defined but not used
4004; Reason-Phrase defined but not used
4005; Referer defined but not used
4006; Retry-After defined but not used
4007; Server defined but not used
4008; Status-Code defined but not used
4009; User-Agent defined but not used
4010]]></artwork></figure></section>
4011
4012
4013<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
4014
4015<section title="Since RFC 2616">
4016<t>
4017  Extracted relevant partitions from <xref target="RFC2616"/>.
4018</t>
4019</section>
4020
4021<section title="Since draft-ietf-httpbis-p2-semantics-00">
4022<t>
4023  Closed issues:
4024  <list style="symbols"> 
4025    <t>
4026      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
4027      "Via is a MUST"
4028      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
4029    </t>
4030    <t>
4031      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
4032      "Fragments allowed in Location"
4033      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
4034    </t>
4035    <t>
4036      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
4037      "Safe Methods vs Redirection"
4038      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
4039    </t>
4040    <t>
4041      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
4042      "Revise description of the POST method"
4043      (<eref target="http://purl.org/NET/http-errata#post"/>)
4044    </t>
4045    <t>
4046      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
4047      "Normative and Informative references"
4048    </t>
4049    <t>
4050      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
4051      "RFC2606 Compliance"
4052    </t>
4053    <t>
4054      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
4055      "Informative references"
4056    </t>
4057    <t>
4058      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
4059      "Redundant cross-references"
4060    </t>
4061  </list>
4062</t>
4063<t>
4064  Other changes:
4065  <list style="symbols"> 
4066    <t>
4067      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
4068    </t>
4069  </list>
4070</t>
4071</section>
4072
4073<section title="Since draft-ietf-httpbis-p2-semantics-01">
4074<t>
4075  Closed issues:
4076  <list style="symbols"> 
4077    <t>
4078      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
4079      "PUT side effects"
4080    </t>
4081    <t>
4082      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
4083      "Duplicate Host header requirements"
4084    </t>
4085  </list>
4086</t>
4087<t>
4088  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4089  <list style="symbols"> 
4090    <t>
4091      Move "Product Tokens" section (back) into Part 1, as "token" is used
4092      in the definition of the Upgrade header field.
4093    </t>
4094    <t>
4095      Add explicit references to BNF syntax and rules imported from other parts of the specification.
4096    </t>
4097    <t>
4098      Copy definition of delta-seconds from Part6 instead of referencing it.
4099    </t>
4100  </list>
4101</t>
4102</section>
4103
4104<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
4105<t>
4106  Closed issues:
4107  <list style="symbols"> 
4108    <t>
4109      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
4110      "Requiring Allow in 405 responses"
4111    </t>
4112    <t>
4113      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
4114      "Status Code Registry"
4115    </t>
4116    <t>
4117      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
4118      "Redirection vs. Location"
4119    </t>
4120    <t>
4121      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
4122      "Cacheability of 303 response"
4123    </t>
4124    <t>
4125      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
4126      "305 Use Proxy"
4127    </t>
4128    <t>
4129      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
4130      "Classification for Allow header"
4131    </t>
4132    <t>
4133      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
4134      "PUT - 'store under' vs 'store at'"
4135    </t>
4136  </list>
4137</t>
4138<t>
4139  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
4140  <list style="symbols"> 
4141    <t>
4142      Reference RFC 3984, and update header field registrations for headers defined
4143      in this document.
4144    </t>
4145  </list>
4146</t>
4147<t>
4148  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4149  <list style="symbols"> 
4150    <t>
4151      Replace string literals when the string really is case-sensitive (method).
4152    </t>
4153  </list>
4154</t>
4155</section>
4156
4157<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
4158<t>
4159  Closed issues:
4160  <list style="symbols"> 
4161    <t>
4162      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
4163      "OPTIONS request bodies"
4164    </t>
4165    <t>
4166      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
4167      "Description of CONNECT should refer to RFC2817"
4168    </t>
4169    <t>
4170      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
4171      "Location Content-Location reference request/response mixup"
4172    </t>
4173  </list>
4174</t>
4175<t>
4176  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
4177  <list style="symbols"> 
4178    <t>
4179      Added initial proposal for registration process, plus initial
4180      content (non-HTTP/1.1 methods to be added by a separate specification).
4181    </t>
4182  </list>
4183</t>
4184</section>
4185
4186<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
4187<t>
4188  Closed issues:
4189  <list style="symbols"> 
4190    <t>
4191      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
4192      "Content-*"
4193    </t>
4194    <t>
4195      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
4196      "RFC 2822 is updated by RFC 5322"
4197    </t>
4198  </list>
4199</t>
4200<t>
4201  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4202  <list style="symbols"> 
4203    <t>
4204      Use "/" instead of "|" for alternatives.
4205    </t>
4206    <t>
4207      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
4208      whitespace ("OWS") and required whitespace ("RWS").
4209    </t>
4210    <t>
4211      Rewrite ABNFs to spell out whitespace rules, factor out
4212      header field value format definitions.
4213    </t>
4214  </list>
4215</t>
4216</section>
4217
4218<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
4219<t>
4220  Closed issues:
4221  <list style="symbols"> 
4222    <t>
4223      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
4224      "Reason-Phrase BNF"
4225    </t>
4226  </list>
4227</t>
4228<t>
4229  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4230  <list style="symbols"> 
4231    <t>
4232      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
4233    </t>
4234  </list>
4235</t>
4236</section>
4237
4238<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
4239<t>
4240  Closed issues:
4241  <list style="symbols"> 
4242    <t>
4243      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
4244      "Clarify when Referer is sent"
4245    </t>
4246    <t>
4247      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
4248      "status codes vs methods"
4249    </t>
4250    <t>
4251      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
4252      "Do not require "updates" relation for specs that register status codes or method names"
4253    </t>
4254  </list>
4255</t>
4256</section>
4257
4258<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
4259<t>
4260  Closed issues:
4261  <list style="symbols"> 
4262    <t>
4263      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
4264      "Idempotency"
4265    </t>
4266    <t>
4267      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
4268      "TRACE security considerations"
4269    </t>
4270    <t>
4271      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
4272      "Clarify rules for determining what entities a response carries"
4273    </t>
4274    <t>
4275      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
4276      "update note citing RFC 1945 and 2068"
4277    </t>
4278    <t>
4279      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
4280      "update note about redirect limit"
4281    </t>
4282    <t>
4283      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
4284      "Location header ABNF should use 'URI'"
4285    </t>
4286    <t>
4287      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
4288      "fragments in Location vs status 303"
4289    </t>
4290    <t>
4291      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
4292      "move IANA registrations for optional status codes"
4293    </t>
4294  </list>
4295</t>
4296<t>
4297  Partly resolved issues:
4298  <list style="symbols"> 
4299    <t>
4300      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
4301      "Are OPTIONS and TRACE safe?"
4302    </t>
4303  </list>
4304</t>
4305</section>
4306
4307<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
4308<t>
4309  Closed issues:
4310  <list style="symbols"> 
4311    <t>
4312      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
4313      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
4314      status codes when fixing this previously)
4315    </t>
4316  </list>
4317</t>
4318</section>
4319
4320<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
4321<t>
4322  Closed issues:
4323  <list style="symbols"> 
4324    <t>
4325      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4326      "Fragment combination / precedence during redirects"
4327    </t>
4328  </list>
4329</t>
4330<t>
4331  Partly resolved issues:
4332  <list style="symbols"> 
4333    <t>
4334      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
4335      "Location header payload handling"
4336    </t>
4337    <t>
4338      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
4339      "Term for the requested resource's URI"
4340    </t>
4341  </list>
4342</t>
4343</section>
4344
4345<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
4346<t>
4347  Closed issues:
4348  <list style="symbols"> 
4349    <t>
4350      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
4351      "Clarify 'Requested Variant'"
4352    </t>
4353    <t>
4354      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
4355      "Clarify entity / representation / variant terminology"
4356    </t>
4357    <t>
4358      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/139"/>:
4359      "Methods and Caching"
4360    </t>
4361    <t>
4362      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/190"/>:
4363      "OPTIONS vs Max-Forwards"
4364    </t>
4365    <t>
4366      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/199"/>:
4367      "Status codes and caching"
4368    </t>
4369    <t>
4370      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
4371      "consider removing the 'changes from 2068' sections"
4372    </t>
4373  </list>
4374</t>
4375</section>
4376
4377<section title="Since draft-ietf-httpbis-p2-semantics-11" anchor="changes.since.11">
4378<t>
4379  Closed issues:
4380  <list style="symbols"> 
4381    <t>
4382      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/229"/>:
4383      "Considerations for new status codes"
4384    </t>
4385    <t>
4386      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/230"/>:
4387      "Considerations for new methods"
4388    </t>
4389    <t>
4390      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/232"/>:
4391      "User-Agent guidelines" (relating to the 'User-Agent' header field)
4392    </t>
4393  </list>
4394</t>
4395</section>
4396
4397<section title="Since draft-ietf-httpbis-p2-semantics-12" anchor="changes.since.12">
4398<t>
4399  Closed issues:
4400  <list style="symbols"> 
4401    <t>
4402      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4403      "Fragment combination / precedence during redirects" (added warning
4404      about having a fragid on the redirect may cause inconvenience in
4405      some cases)
4406    </t>
4407    <t>
4408      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/79"/>:
4409      "Content-* vs. PUT"
4410    </t>
4411    <t>
4412      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/88"/>:
4413      "205 Bodies"
4414    </t>
4415    <t>
4416      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/102"/>:
4417      "Understanding Content-* on non-PUT requests"
4418    </t>
4419    <t>
4420      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
4421      "Content-*"
4422    </t>
4423    <t>
4424      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/104"/>:
4425      "Header type defaulting"
4426    </t>
4427    <t>
4428      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
4429      "PUT - 'store under' vs 'store at'"
4430    </t>
4431    <t>
4432      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/137"/>:
4433      "duplicate ABNF for Reason-Phrase"
4434    </t>
4435    <t>
4436      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/180"/>:
4437      "Note special status of Content-* prefix in header registration procedures"
4438    </t>
4439    <t>
4440      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/203"/>:
4441      "Max-Forwards vs extension methods"
4442    </t>
4443    <t>
4444      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/213"/>:
4445      "What is the value space of HTTP status codes?" (actually fixed in
4446      draft-ietf-httpbis-p2-semantics-11)
4447    </t>
4448    <t>
4449      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/224"/>:
4450      "Header Classification"
4451    </t>
4452    <t>
4453      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/225"/>:
4454      "PUT side effect: invalidation or just stale?"
4455    </t>
4456    <t>
4457      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/226"/>:
4458      "proxies not supporting certain methods"
4459    </t>
4460    <t>
4461      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/239"/>:
4462      "Migrate CONNECT from RFC2817 to p2"
4463    </t>
4464    <t>
4465      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/240"/>:
4466      "Migrate Upgrade details from RFC2817"
4467    </t>
4468    <t>
4469      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/267"/>:
4470      "clarify PUT semantics'"
4471    </t>
4472    <t>
4473      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/275"/>:
4474      "duplicate ABNF for 'Method'"
4475    </t>
4476    <t>
4477      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4478      "untangle ABNFs for header fields"
4479    </t>
4480  </list>
4481</t>
4482</section>
4483
4484<section title="Since draft-ietf-httpbis-p2-semantics-13" anchor="changes.since.13">
4485<t>
4486  Closed issues:
4487  <list style="symbols"> 
4488    <t>
4489      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4490      "untangle ABNFs for header fields"
4491    </t>
4492    <t>
4493      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/251"/>:
4494      "message-body in CONNECT request"
4495    </t>
4496  </list>
4497</t>
4498</section>
4499
4500<section title="Since draft-ietf-httpbis-p2-semantics-14" anchor="changes.since.14">
4501<t>
4502  Closed issues:
4503  <list style="symbols"> 
4504    <t>
4505      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/255"/>:
4506      "Clarify status code for rate limiting"
4507    </t>
4508    <t>
4509      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/294"/>:
4510      "clarify 403 forbidden"
4511    </t>
4512    <t>
4513      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/296"/>:
4514      "Clarify 203 Non-Authoritative Information"
4515    </t>
4516    <t>
4517      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/298"/>:
4518      "update default reason phrase for 413"
4519    </t>
4520  </list>
4521</t>
4522</section>
4523
4524<section title="Since draft-ietf-httpbis-p2-semantics-15" anchor="changes.since.15">
4525<t>
4526  Closed issues:
4527  <list style="symbols"> 
4528    <t>
4529      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/285"/>:
4530      "Strength of requirements on Accept re: 406"
4531    </t>
4532    <t>
4533      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/303"/>:
4534      "400 response isn't generic"
4535    </t>
4536  </list>
4537</t>
4538</section>
4539
4540<section title="Since draft-ietf-httpbis-p2-semantics-16" anchor="changes.since.16">
4541<t>
4542  Closed issues:
4543  <list style="symbols"> 
4544    <t>
4545      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/160"/>:
4546      "Redirects and non-GET methods"
4547    </t>
4548    <t>
4549      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/186"/>:
4550      "Document HTTP's error-handling philosophy"
4551    </t>
4552    <t>
4553      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/231"/>:
4554      "Considerations for new headers"
4555    </t>
4556    <t>
4557      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/310"/>:
4558      "clarify 303 redirect on HEAD"
4559    </t>
4560  </list>
4561</t>
4562</section>
4563
4564</section>
4565
4566</back>
4567</rfc>
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