source: draft-ietf-httpbis/12/draft-ietf-httpbis-p2-semantics-12.xml @ 1515

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fix mime types

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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-12">
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="Day Software">Day Software</organization>
26    <address>
27      <postal>
28        <street>23 Corporate Plaza DR, Suite 280</street>
29        <city>Newport Beach</city>
30        <region>CA</region>
31        <code>92660</code>
32        <country>USA</country>
33      </postal>
34      <phone>+1-949-706-5300</phone>
35      <facsimile>+1-949-706-5305</facsimile>
36      <email>fielding@gbiv.com</email>
37      <uri>http://roy.gbiv.com/</uri>
38    </address>
39  </author>
40
41  <author initials="J." surname="Gettys" fullname="Jim Gettys">
42    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
43    <address>
44      <postal>
45        <street>21 Oak Knoll Road</street>
46        <city>Carlisle</city>
47        <region>MA</region>
48        <code>01741</code>
49        <country>USA</country>
50      </postal>
51      <email>jg@freedesktop.org</email>
52      <uri>http://gettys.wordpress.com/</uri>
53    </address>
54  </author>
55 
56  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
57    <organization abbrev="HP">Hewlett-Packard Company</organization>
58    <address>
59      <postal>
60        <street>HP Labs, Large Scale Systems Group</street>
61        <street>1501 Page Mill Road, MS 1177</street>
62        <city>Palo Alto</city>
63        <region>CA</region>
64        <code>94304</code>
65        <country>USA</country>
66      </postal>
67      <email>JeffMogul@acm.org</email>
68    </address>
69  </author>
70
71  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
72    <organization abbrev="Microsoft">Microsoft Corporation</organization>
73    <address>
74      <postal>
75        <street>1 Microsoft Way</street>
76        <city>Redmond</city>
77        <region>WA</region>
78        <code>98052</code>
79        <country>USA</country>
80      </postal>
81      <email>henrikn@microsoft.com</email>
82    </address>
83  </author>
84
85  <author initials="L." surname="Masinter" fullname="Larry Masinter">
86    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
87    <address>
88      <postal>
89        <street>345 Park Ave</street>
90        <city>San Jose</city>
91        <region>CA</region>
92        <code>95110</code>
93        <country>USA</country>
94      </postal>
95      <email>LMM@acm.org</email>
96      <uri>http://larry.masinter.net/</uri>
97    </address>
98  </author>
99 
100  <author initials="P." surname="Leach" fullname="Paul J. Leach">
101    <organization abbrev="Microsoft">Microsoft Corporation</organization>
102    <address>
103      <postal>
104        <street>1 Microsoft Way</street>
105        <city>Redmond</city>
106        <region>WA</region>
107        <code>98052</code>
108      </postal>
109      <email>paulle@microsoft.com</email>
110    </address>
111  </author>
112   
113  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
114    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
115    <address>
116      <postal>
117        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
118        <street>The Stata Center, Building 32</street>
119        <street>32 Vassar Street</street>
120        <city>Cambridge</city>
121        <region>MA</region>
122        <code>02139</code>
123        <country>USA</country>
124      </postal>
125      <email>timbl@w3.org</email>
126      <uri>http://www.w3.org/People/Berners-Lee/</uri>
127    </address>
128  </author>
129
130  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
131    <organization abbrev="W3C">World Wide Web Consortium</organization>
132    <address>
133      <postal>
134        <street>W3C / ERCIM</street>
135        <street>2004, rte des Lucioles</street>
136        <city>Sophia-Antipolis</city>
137        <region>AM</region>
138        <code>06902</code>
139        <country>France</country>
140      </postal>
141      <email>ylafon@w3.org</email>
142      <uri>http://www.raubacapeu.net/people/yves/</uri>
143    </address>
144  </author>
145
146  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
147    <organization abbrev="greenbytes">greenbytes GmbH</organization>
148    <address>
149      <postal>
150        <street>Hafenweg 16</street>
151        <city>Muenster</city><region>NW</region><code>48155</code>
152        <country>Germany</country>
153      </postal>
154      <phone>+49 251 2807760</phone>
155      <facsimile>+49 251 2807761</facsimile>
156      <email>julian.reschke@greenbytes.de</email>
157      <uri>http://greenbytes.de/tech/webdav/</uri>
158    </address>
159  </author>
160
161  <date month="October" year="2010" day="25"/>
162  <workgroup>HTTPbis Working Group</workgroup>
163
164<abstract>
165<t>
166   The Hypertext Transfer Protocol (HTTP) is an application-level
167   protocol for distributed, collaborative, hypermedia information
168   systems. HTTP has been in use by the World Wide Web global information
169   initiative since 1990. This document is Part 2 of the seven-part specification
170   that defines the protocol referred to as "HTTP/1.1" and, taken together,
171   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
172   as expressed by request methods, request-header fields, response status codes,
173   and response-header 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). The current issues list is
181    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/>
182    and related documents (including fancy diffs) can be found at
183    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
184  </t>
185  <t>
186    The changes in this draft are summarized in <xref target="changes.since.11"/>.
187  </t>
188</note>
189</front>
190<middle>
191<section title="Introduction" anchor="introduction">
192<t>
193   This document defines HTTP/1.1 request and response semantics.  Each HTTP
194   message, as defined in <xref target="Part1"/>, is in the form of either a request or
195   a response.  An HTTP server listens on a connection for HTTP requests and
196   responds to each request, in the order received on that connection, with
197   one or more HTTP response messages.  This document defines the commonly
198   agreed upon semantics of the HTTP uniform interface, the intentions defined
199   by each request method, and the various response messages that might be
200   expected as a result of applying that method to the target resource.
201</t>
202<t>
203   This document is currently disorganized in order to minimize the changes
204   between drafts and enable reviewers to see the smaller errata changes.
205   A future draft will reorganize the sections to better reflect the content.
206   In particular, the sections will be ordered according to the typical
207   processing of an HTTP request message (after message parsing): resource
208   mapping, general header fields, methods, request modifiers, response
209   status, and resource metadata.  The current mess reflects how widely
210   dispersed these topics and associated requirements had become in
211   <xref target="RFC2616"/>.
212</t>
213
214<section title="Requirements" anchor="intro.requirements">
215<t>
216   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
217   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
218   document are to be interpreted as described in <xref target="RFC2119"/>.
219</t>
220<t>
221   An implementation is not compliant if it fails to satisfy one or more
222   of the "MUST" or "REQUIRED" level requirements for the protocols it
223   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
224   level and all the "SHOULD" level requirements for its protocols is said
225   to be "unconditionally compliant"; one that satisfies all the "MUST"
226   level requirements but not all the "SHOULD" level requirements for its
227   protocols is said to be "conditionally compliant".
228</t>
229</section>
230
231<section title="Syntax Notation" anchor="notation">
232 
233 
234 
235 
236 
237<t>
238  This specification uses the ABNF syntax defined in Section 1.2 of <xref target="Part1"/> (which
239  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
240  <xref target="collected.abnf"/> shows the collected ABNF, with the list
241  rule expanded.
242</t>
243<t>
244  The following core rules are included by
245  reference, as defined in <xref target="RFC5234"/>, Appendix B.1:
246  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
247  DIGIT (decimal 0-9), DQUOTE (double quote),
248  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
249  OCTET (any 8-bit sequence of data), SP (space),
250  VCHAR (any visible USASCII character),
251  and WSP (whitespace).
252</t>
253
254<section title="Core Rules" anchor="core.rules">
255 
256 
257 
258 
259 
260<t>
261  The core rules below are defined in Section 1.2.2 of <xref target="Part1"/>:
262</t>
263<figure><artwork type="abnf2616"><![CDATA[
264  quoted-string = <quoted-string, defined in [Part1], Section 1.2.2>
265  token         = <token, defined in [Part1], Section 1.2.2>
266  OWS           = <OWS, defined in [Part1], Section 1.2.2>
267  RWS           = <RWS, defined in [Part1], Section 1.2.2>
268  obs-text      = <obs-text, defined in [Part1], Section 1.2.2>
269]]></artwork></figure>
270</section>
271
272<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
273 
274 
275 
276 
277 
278 
279 
280 
281 
282 
283 
284 
285 
286 
287 
288 
289 
290 
291 
292 
293 
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 2.6>
304  comment       = <comment, defined in [Part1], Section 3.2>
305  Host          = <Host, defined in [Part1], Section 2.6>
306  HTTP-date     = <HTTP-date, defined in [Part1], Section 6.1>
307  partial-URI   = <partial-URI, defined in [Part1], Section 2.6>
308  product       = <product, defined in [Part1], Section 6.3>
309  TE            = <TE, defined in [Part1], Section 9.5>
310  URI-reference = <URI-reference, defined in [Part1], Section 2.6>
311]]></artwork></figure>
312<figure><artwork type="abnf2616"><![CDATA[
313  Accept        = <Accept, defined in [Part3], Section 6.1>
314  Accept-Charset =
315             <Accept-Charset, defined in [Part3], Section 6.2>
316  Accept-Encoding =
317             <Accept-Encoding, defined in [Part3], Section 6.3>
318  Accept-Language =
319             <Accept-Language, defined in [Part3], Section 6.4>
320]]></artwork></figure>
321<figure><artwork type="abnf2616"><![CDATA[
322  ETag          = <ETag, defined in [Part4], Section 6.1>
323  If-Match      = <If-Match, defined in [Part4], Section 6.2>
324  If-Modified-Since =
325             <If-Modified-Since, defined in [Part4], Section 6.3>
326  If-None-Match = <If-None-Match, defined in [Part4], Section 6.4>
327  If-Unmodified-Since =
328             <If-Unmodified-Since, defined in [Part4], Section 6.5>
329]]></artwork></figure>
330<figure><artwork type="abnf2616"><![CDATA[
331  Accept-Ranges = <Accept-Ranges, defined in [Part5], Section 5.1>
332  If-Range      = <If-Range, defined in [Part5], Section 5.3>
333  Range         = <Range, defined in [Part5], Section 5.4>
334]]></artwork></figure>
335<figure><artwork type="abnf2616"><![CDATA[
336  Age           = <Age, defined in [Part6], Section 3.1>
337  Vary          = <Vary, defined in [Part6], Section 3.5>
338]]></artwork></figure>
339<figure><artwork type="abnf2616"><![CDATA[
340  Authorization = <Authorization, defined in [Part7], Section 4.1>
341  Proxy-Authenticate =
342             <Proxy-Authenticate, defined in [Part7], Section 4.2>
343  Proxy-Authorization =
344             <Proxy-Authorization, defined in [Part7], Section 4.3>
345  WWW-Authenticate =
346             <WWW-Authenticate, defined in [Part7], Section 4.4>
347]]></artwork></figure>
348</section>
349</section>
350</section>
351
352<section title="Method" anchor="method">
353 
354 
355<t>
356   The Method token indicates the method to be performed on the target
357   resource (Section 4.3 of <xref target="Part1"/>). The method is case-sensitive.
358</t>
359<figure><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/><artwork type="abnf2616"><![CDATA[
360  Method         = %x4F.50.54.49.4F.4E.53   ; "OPTIONS", Section 7.2
361                 / %x47.45.54               ; "GET", Section 7.3
362                 / %x48.45.41.44            ; "HEAD", Section 7.4
363                 / %x50.4F.53.54            ; "POST", Section 7.5
364                 / %x50.55.54               ; "PUT", Section 7.6
365                 / %x44.45.4C.45.54.45      ; "DELETE", Section 7.7
366                 / %x54.52.41.43.45         ; "TRACE", Section 7.8
367                 / %x43.4F.4E.4E.45.43.54   ; "CONNECT", Section 7.9
368                 / extension-method
369  extension-method = token
370]]></artwork></figure>
371<t>
372   The list of methods allowed by a resource can be specified in an
373   Allow header field (<xref target="header.allow"/>). The status code of the response
374   always notifies the client whether a method is currently allowed on a
375   resource, since the set of allowed methods can change dynamically. An
376   origin server SHOULD respond with the status code 405 (Method Not Allowed)
377   if the method is known by the origin server but not allowed for the
378   resource, and 501 (Not Implemented) if the method is
379   unrecognized or not implemented by the origin server. The methods GET
380   and HEAD MUST be supported by all general-purpose servers. All other
381   methods are OPTIONAL; however, if the above methods are implemented,
382   they MUST be implemented with the same semantics as those specified
383   in <xref target="method.definitions"/>.
384</t>
385
386<section title="Method Registry" anchor="method.registry">
387<t>
388  The HTTP Method Registry defines the name space for the Method token in the
389  Request line of an HTTP request.
390</t>
391<t>
392  Registrations MUST include the following fields:
393  <list style="symbols">
394    <t>Method Name (see <xref target="method"/>)</t>
395    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
396    <t>Pointer to specification text</t>
397  </list>
398</t>
399<t>
400  Values to be added to this name space are subject to IETF review
401  (<xref target="RFC5226"/>, Section 4.1).
402</t>
403<t>
404  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
405</t>
406
407<section title="Considerations for New Methods" anchor="considerations.for.new.methods">
408<t>
409   When it is necessary to express new semantics for a HTTP request that
410   aren't specific to a single application or media type, and currently defined
411   methods are inadequate, it may be appropriate to register a new method.
412</t>
413<t>
414   HTTP methods are generic; that is, they are potentially applicable to any
415   resource, not just one particular media type, "type" of resource, or
416   application. As such, it is preferred that new HTTP methods be registered
417   in a document that isn't specific to a single application, so that this is
418   clear.
419</t>
420<t>
421   Due to the parsing rules defined in Section 3.3 of <xref target="Part1"/>, definitions of HTTP
422   methods cannot prohibit the presence of a message-body on either the request
423   or the response message (with responses to HEAD requests being the single
424   exception). Definitions of new methods cannot change this rule, but they can
425   specify that only zero-length bodies (as opposed to absent bodies) are allowed.
426</t>
427<t>
428   New method definitions need to indicate whether they are safe (<xref target="safe.methods"/>) and whether they are idempotent (<xref target="idempotent.methods"/>). They also need to state whether they can be
429   cached (<xref target="Part6"/>); in particular what conditions a cache may store the
430   response, and under what conditions such a stored response may be used to
431   satisfy a subsequent request.
432</t>
433</section>
434
435</section>
436</section>
437
438<section title="Request Header Fields" anchor="request.header.fields">
439 
440<t>
441   The request-header fields allow the client to pass additional
442   information about the request, and about the client itself, to the
443   server. These fields act as request modifiers, with semantics
444   equivalent to the parameters on a programming language method
445   invocation.
446</t>
447<figure><iref primary="true" item="Grammar" subitem="request-header"/><artwork type="abnf2616"><![CDATA[
448  request-header = Accept                   ; [Part3], Section 6.1
449                 / Accept-Charset           ; [Part3], Section 6.2
450                 / Accept-Encoding          ; [Part3], Section 6.3
451                 / Accept-Language          ; [Part3], Section 6.4
452                 / Authorization            ; [Part7], Section 4.1
453                 / Expect                   ; Section 9.2
454                 / From                     ; Section 9.3
455                 / Host                     ; [Part1], Section 9.4
456                 / If-Match                 ; [Part4], Section 6.2
457                 / If-Modified-Since        ; [Part4], Section 6.3
458                 / If-None-Match            ; [Part4], Section 6.4
459                 / If-Range                 ; [Part5], Section 5.3
460                 / If-Unmodified-Since      ; [Part4], Section 6.5
461                 / Max-Forwards             ; Section 9.5
462                 / Proxy-Authorization      ; [Part7], Section 4.3
463                 / Range                    ; [Part5], Section 5.4
464                 / Referer                  ; Section 9.6
465                 / TE                       ; [Part1], Section 9.5
466                 / User-Agent               ; Section 9.9
467]]></artwork></figure>
468<t>
469   Request-header field names can be extended reliably only in
470   combination with a change in the protocol version. However, new or
471   experimental header fields MAY be given the semantics of request-header
472   fields if all parties in the communication recognize them to
473   be request-header fields.
474</t>
475</section>
476
477<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
478 
479 
480 
481<t>
482   The Status-Code element is a 3-digit integer result code of the
483   attempt to understand and satisfy the request. The status codes listed
484   below are defined in <xref target="status.codes"/>, Section 3 of <xref target="Part4"/>,
485   Section 3 of <xref target="Part5"/>, and Section 3 of <xref target="Part7"/>.
486</t>
487<t>
488   The Reason-Phrase is intended to give a short
489   textual description of the Status-Code. The Status-Code is intended
490   for use by automata and the Reason-Phrase is intended for the human
491   user. The client is not required to examine or display the Reason-Phrase.
492</t>
493<t> 
494   The individual values of the numeric status codes defined for
495   HTTP/1.1, and an example set of corresponding Reason-Phrase values, are
496   presented below. The reason phrases listed here are only
497   recommendations -- they MAY be replaced by local equivalents without
498   affecting the protocol.
499</t>
500<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[
501  Status-Code =
502       "100"  ; Section 8.1.1: Continue
503     / "101"  ; Section 8.1.2: Switching Protocols
504     / "200"  ; Section 8.2.1: OK
505     / "201"  ; Section 8.2.2: Created
506     / "202"  ; Section 8.2.3: Accepted
507     / "203"  ; Section 8.2.4: Non-Authoritative Information
508     / "204"  ; Section 8.2.5: No Content
509     / "205"  ; Section 8.2.6: Reset Content
510     / "206"  ; [Part5], Section 3.1: Partial Content
511     / "300"  ; Section 8.3.1: Multiple Choices
512     / "301"  ; Section 8.3.2: Moved Permanently
513     / "302"  ; Section 8.3.3: Found
514     / "303"  ; Section 8.3.4: See Other
515     / "304"  ; [Part4], Section 3.1: Not Modified
516     / "305"  ; Section 8.3.6: Use Proxy
517     / "307"  ; Section 8.3.8: Temporary Redirect
518     / "400"  ; Section 8.4.1: Bad Request
519     / "401"  ; [Part7], Section 3.1: Unauthorized
520     / "402"  ; Section 8.4.3: Payment Required
521     / "403"  ; Section 8.4.4: Forbidden
522     / "404"  ; Section 8.4.5: Not Found
523     / "405"  ; Section 8.4.6: Method Not Allowed
524     / "406"  ; Section 8.4.7: Not Acceptable
525     / "407"  ; [Part7], Section 3.2: Proxy Authentication Required
526     / "408"  ; Section 8.4.9: Request Time-out
527     / "409"  ; Section 8.4.10: Conflict
528     / "410"  ; Section 8.4.11: Gone
529     / "411"  ; Section 8.4.12: Length Required
530     / "412"  ; [Part4], Section 3.2: Precondition Failed
531     / "413"  ; Section 8.4.14: Request Entity Too Large
532     / "414"  ; Section 8.4.15: URI Too Long
533     / "415"  ; Section 8.4.16: Unsupported Media Type
534     / "416"  ; [Part5], Section 3.2: Requested range not satisfiable
535     / "417"  ; Section 8.4.18: Expectation Failed
536     / "500"  ; Section 8.5.1: Internal Server Error
537     / "501"  ; Section 8.5.2: Not Implemented
538     / "502"  ; Section 8.5.3: Bad Gateway
539     / "503"  ; Section 8.5.4: Service Unavailable
540     / "504"  ; Section 8.5.5: Gateway Time-out
541     / "505"  ; Section 8.5.6: HTTP Version not supported
542     / extension-code
543
544  extension-code = 3DIGIT
545  Reason-Phrase  = *( WSP / VCHAR / obs-text )
546]]></artwork></figure>
547<t>
548   HTTP status codes are extensible. HTTP applications are not required
549   to understand the meaning of all registered status codes, though such
550   understanding is obviously desirable. However, applications MUST
551   understand the class of any status code, as indicated by the first
552   digit, and treat any unrecognized response as being equivalent to the
553   x00 status code of that class, with the exception that an
554   unrecognized response MUST NOT be cached. For example, if an
555   unrecognized status code of 431 is received by the client, it can
556   safely assume that there was something wrong with its request and
557   treat the response as if it had received a 400 status code. In such
558   cases, user agents SHOULD present to the user the representation enclosed
559   with the response, since that representation is likely to include human-readable
560   information which will explain the unusual status.
561</t>
562
563<section title="Status Code Registry" anchor="status.code.registry">
564<t>
565  The HTTP Status Code Registry defines the name space for the Status-Code
566  token in the Status-Line of an HTTP response.
567</t>
568<t>
569  Values to be added to this name space are subject to IETF review
570  (<xref target="RFC5226"/>, Section 4.1).
571</t>
572<t>
573  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
574</t>
575
576<section title="Considerations for New Status Codes" anchor="considerations.for.new.status.codes">
577<t>
578   When it is necessary to express new semantics for a HTTP response that
579   aren't specific to a single application or media type, and currently defined
580   status codes are inadequate, a new status code can be registered.
581</t>
582<t>
583   HTTP status codes are generic; that is, they are potentially applicable to
584   any resource, not just one particular media type, "type" of resource, or
585   application. As such, it is preferred that new HTTP status codes be
586   registered in a document that isn't specific to a single application, so
587   that this is clear.
588</t>
589<t>
590   Definitions of new HTTP status codes typically explain the request
591   conditions that produce a response containing the status code (e.g.,
592   combinations of request headers and/or method(s)), along with any
593   interactions with response headers (e.g., those that are required, those
594   that modify the semantics of the response).
595</t>
596<t>
597   New HTTP status codes are required to fall under one of the categories
598   defined in <xref target="status.codes"/>. To allow existing parsers to
599   properly handle them, new status codes cannot disallow a response body,
600   although they can mandate a zero-length response body. They can require the
601   presence of one or more particular HTTP response header(s).
602</t>
603<t>
604   Likewise, their definitions can specify that caches are allowed to use
605   heuristics to determine their freshness (see <xref target="Part6"/>; by default, it is
606   not allowed), and can define how to determine the resource which they
607   carry a representation for (see <xref target="identifying.response.associated.with.representation"/>; by default,
608   it is anonymous).
609</t>
610</section>
611
612</section>
613
614</section>
615
616<section title="Response Header Fields" anchor="response.header.fields">
617 
618<t>
619   The response-header fields allow the server to pass additional
620   information about the response which cannot be placed in the Status-Line.
621   These header fields give information about the server and about
622   further access to the target resource (Section 4.3 of <xref target="Part1"/>).
623</t>
624<figure><iref primary="true" item="Grammar" subitem="response-header"/><artwork type="abnf2616"><![CDATA[
625  response-header = Accept-Ranges           ; [Part5], Section 5.1
626                  / Age                     ; [Part6], Section 3.1
627                  / Allow                   ; Section 9.1
628                  / ETag                    ; [Part4], Section 6.1
629                  / Location                ; Section 9.4
630                  / Proxy-Authenticate      ; [Part7], Section 4.2
631                  / Retry-After             ; Section 9.7
632                  / Server                  ; Section 9.8
633                  / Vary                    ; [Part6], Section 3.5
634                  / WWW-Authenticate        ; [Part7], Section 4.4
635]]></artwork></figure>
636<t>
637   Response-header field names can be extended reliably only in
638   combination with a change in the protocol version. However, new or
639   experimental header fields MAY be given the semantics of response-header
640   fields if all parties in the communication recognize them to
641   be response-header fields.
642</t>
643</section>
644
645<section title="Representation" anchor="representation">
646<t>
647   Request and Response messages MAY transfer a representation if not otherwise
648   restricted by the request method or response status code. A representation
649   consists of metadata (representation header fields) and data (representation
650   body).  When a complete or partial representation is enclosed in an HTTP message,
651   it is referred to as the payload of the message. HTTP representations
652   are defined in <xref target="Part3"/>.
653</t>
654<t>
655   A representation body is only present in a message when a message-body is
656   present, as described in Section 3.3 of <xref target="Part1"/>. The representation body is obtained
657   from the message-body by decoding any Transfer-Encoding that might
658   have been applied to ensure safe and proper transfer of the message.
659</t>
660
661<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
662<t>
663   It is sometimes necessary to determine an identifier for the resource
664   associated with a representation.
665</t>
666<t>
667   An HTTP request representation, when present, is always associated with an
668   anonymous (i.e., unidentified) resource.
669</t>
670<t>
671   In the common case, an HTTP response is a representation of the target
672   resource (see Section 4.3 of <xref target="Part1"/>). However, this is not always the
673   case. To determine the URI of the resource a response is associated with,
674   the following rules are used (with the first applicable one being selected):
675</t>
676<t><list style="numbers">
677   <t>If the response status code is 200 or 203 and the request method was GET,
678   the response payload is a representation of the target resource.</t>
679   <t>If the response status code is 204, 206, or 304 and the request method was GET
680   or HEAD, the response payload is a partial representation of the target
681   (see Section 2.8 of <xref target="Part6"/>).</t>
682   <t>If the response has a Content-Location header field, and that URI is the same
683   as the effective request URI, the response payload is a representation of the
684   target resource.</t>
685   <t>If the response has a Content-Location header field, and that URI is not the
686   same as the effective request URI, then the response asserts that its
687   payload is a representation of the resource identified by the
688   Content-Location URI. However, such an assertion cannot be trusted unless
689   it can be verified by other means (not defined by HTTP).</t>
690   <t>Otherwise, the response is a representation of an anonymous (i.e.,
691   unidentified) resource.</t>
692</list></t>
693<t>
694  <cref anchor="TODO-req-uri">
695   The comparison function is going to have to be defined somewhere,
696   because we already need to compare URIs for things like cache invalidation.</cref>
697</t>
698</section>
699
700</section>
701
702
703<section title="Method Definitions" anchor="method.definitions">
704<t>
705   The set of common methods for HTTP/1.1 is defined below. Although
706   this set can be expanded, additional methods cannot be assumed to
707   share the same semantics for separately extended clients and servers.
708</t>
709
710<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
711
712<section title="Safe Methods" anchor="safe.methods">
713<iref item="Safe Methods" primary="true"/>
714<t>
715   Implementors need to be aware that the software represents the user in
716   their interactions over the Internet, and need to allow
717   the user to be aware of any actions they take which might have an
718   unexpected significance to themselves or others.
719</t>
720<t>
721   In particular, the convention has been established that the GET, HEAD,
722   OPTIONS, and TRACE methods SHOULD NOT have the significance of taking an action
723   other than retrieval. These methods ought to be considered "safe".
724   This allows user agents to represent other methods, such as POST, PUT
725   and DELETE, in a special way, so that the user is made aware of the
726   fact that a possibly unsafe action is being requested.
727</t>
728<t>
729   Naturally, it is not possible to ensure that the server does not
730   generate side-effects as a result of performing a GET request; in
731   fact, some dynamic resources consider that a feature. The important
732   distinction here is that the user did not request the side-effects,
733   so therefore cannot be held accountable for them.
734</t>
735</section>
736
737<section title="Idempotent Methods" anchor="idempotent.methods">
738<iref item="Idempotent Methods" primary="true"/>
739<t>
740   Methods can also have the property of "idempotence" in that, aside
741   from error or expiration issues, the intended effect of multiple
742   identical requests is the same as for a single request.
743   The methods PUT, DELETE, and all safe methods are idempotent.
744   It is important to note that idempotence refers only to changes
745   requested by the client: a server is free to change its state due
746   to multiple requests for the purpose of tracking those requests,
747   versioning of results, etc.
748</t>
749</section>
750</section>
751
752<section title="OPTIONS" anchor="OPTIONS">
753 
754  <iref primary="true" item="OPTIONS method"/>
755  <iref primary="true" item="Methods" subitem="OPTIONS"/>
756<t>
757   The OPTIONS method represents a request for information about the
758   communication options available on the request/response chain
759   identified by the effective request URI. This method allows the client to
760   determine the options and/or requirements associated with a resource,
761   or the capabilities of a server, without implying a resource action
762   or initiating a resource retrieval.
763</t>
764<t>
765   Responses to this method are not cacheable.
766</t>
767<t>
768   If the OPTIONS request includes a message-body (as indicated by the
769   presence of Content-Length or Transfer-Encoding), then the media type
770   MUST be indicated by a Content-Type field. Although this
771   specification does not define any use for such a body, future
772   extensions to HTTP might use the OPTIONS body to make more detailed
773   queries on the server.
774</t>
775<t>
776   If the request-target is an asterisk ("*"), the OPTIONS request is
777   intended to apply to the server in general rather than to a specific
778   resource. Since a server's communication options typically depend on
779   the resource, the "*" request is only useful as a "ping" or "no-op"
780   type of method; it does nothing beyond allowing the client to test
781   the capabilities of the server. For example, this can be used to test
782   a proxy for HTTP/1.1 compliance (or lack thereof).
783</t>
784<t>
785   If the request-target is not an asterisk, the OPTIONS request applies
786   only to the options that are available when communicating with that
787   resource.
788</t>
789<t>
790   A 200 response SHOULD include any header fields that indicate
791   optional features implemented by the server and applicable to that
792   resource (e.g., Allow), possibly including extensions not defined by
793   this specification. The response body, if any, SHOULD also include
794   information about the communication options. The format for such a
795   body is not defined by this specification, but might be defined by
796   future extensions to HTTP. Content negotiation MAY be used to select
797   the appropriate response format. If no response body is included, the
798   response MUST include a Content-Length field with a field-value of
799   "0".
800</t>
801<t>
802   The Max-Forwards request-header field MAY be used to target a
803   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
804   If no Max-Forwards field is present in the request, then the forwarded
805   request MUST NOT include a Max-Forwards field.
806</t>
807</section>
808
809<section title="GET" anchor="GET">
810 
811  <iref primary="true" item="GET method"/>
812  <iref primary="true" item="Methods" subitem="GET"/>
813<t>
814   The GET method means retrieve whatever information (in the form of a
815   representation) currently corresponds to the target resource.
816</t>
817<t>   
818   If the target resource is a data-producing process, it is the
819   produced data which shall be returned as the representation in the response and not
820   the source text of the process, unless that text happens to be the output of
821   the process.
822</t>
823<t>
824   The semantics of the GET method change to a "conditional GET" if the
825   request message includes an If-Modified-Since, If-Unmodified-Since,
826   If-Match, If-None-Match, or If-Range header field. A conditional GET
827   method requests that the representation be transferred only under the
828   circumstances described by the conditional header field(s). The
829   conditional GET method is intended to reduce unnecessary network
830   usage by allowing cached representations to be refreshed without requiring
831   multiple requests or transferring data already held by the client.
832</t>
833<t>
834   The semantics of the GET method change to a "partial GET" if the
835   request message includes a Range header field. A partial GET requests
836   that only part of the representation be transferred, as described in Section 5.4 of <xref target="Part5"/>.
837   The partial GET method is intended to reduce unnecessary
838   network usage by allowing partially-retrieved representations to be
839   completed without transferring data already held by the client.
840</t>
841<t>
842   The response to a GET request is cacheable and MAY be used to satisfy
843   subsequent GET and HEAD requests (see <xref target="Part6"/>).
844</t>
845<t>
846   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
847</t>
848</section>
849
850<section title="HEAD" anchor="HEAD">
851 
852  <iref primary="true" item="HEAD method"/>
853  <iref primary="true" item="Methods" subitem="HEAD"/>
854<t>
855   The HEAD method is identical to GET except that the server MUST NOT
856   return a message-body in the response. The metadata contained
857   in the HTTP header fields in response to a HEAD request SHOULD be identical
858   to the information sent in response to a GET request. This method can
859   be used for obtaining metadata about the representation implied by the
860   request without transferring the representation body. This method is
861   often used for testing hypertext links for validity, accessibility,
862   and recent modification.
863</t>
864<t>
865   The response to a HEAD request is cacheable and MAY be used to satisfy
866   a subsequent HEAD request; see <xref target="Part6"/>. It also MAY be used to update a previously cached
867   representation from that resource; if the new field values
868   indicate that the cached representation differs from the current representation (as
869   would be indicated by a change in Content-Length, Content-MD5, ETag
870   or Last-Modified), then the cache MUST treat the cache entry as
871   stale.
872</t>
873</section>
874
875<section title="POST" anchor="POST">
876  <iref primary="true" item="POST method"/>
877  <iref primary="true" item="Methods" subitem="POST"/>
878<t>
879   The POST method is used to request that the origin server accept the
880   representation enclosed in the request as data to be processed by the
881   target resource. POST is designed to allow a uniform method to cover the
882   following functions:
883  <list style="symbols">
884    <t>
885      Annotation of existing resources;
886    </t>
887    <t>
888        Posting a message to a bulletin board, newsgroup, mailing list,
889        or similar group of articles;
890    </t>
891    <t>
892        Providing a block of data, such as the result of submitting a
893        form, to a data-handling process;
894    </t>
895    <t>
896        Extending a database through an append operation.
897    </t>
898  </list>
899</t>
900<t>
901   The actual function performed by the POST method is determined by the
902   server and is usually dependent on the effective request URI.
903</t>
904<t>
905   The action performed by the POST method might not result in a
906   resource that can be identified by a URI. In this case, either 200
907   (OK) or 204 (No Content) is the appropriate response status code,
908   depending on whether or not the response includes a representation that
909   describes the result.
910</t>
911<t>
912   If a resource has been created on the origin server, the response
913   SHOULD be 201 (Created) and contain a representation which describes the
914   status of the request and refers to the new resource, and a Location
915   header field (see <xref target="header.location"/>).
916</t>
917<t>
918   Responses to POST requests are only cacheable when they
919   include explicit freshness information (see Section 2.3.1 of <xref target="Part6"/>). A
920   cached POST response with a Content-Location header field
921   (see Section 6.7 of <xref target="Part3"/>) whose value is the effective
922   Request URI MAY be used to satisfy subsequent GET and HEAD requests.
923</t>
924<t>
925   Note that POST caching is not widely implemented.
926   However, the 303 (See Other) response can be used to direct the
927   user agent to retrieve a cacheable resource.
928</t>
929</section>
930
931<section title="PUT" anchor="PUT">
932  <iref primary="true" item="PUT method"/>
933  <iref primary="true" item="Methods" subitem="PUT"/>
934<t>
935   The PUT method requests that the enclosed representation be stored at the
936   effective request URI. If the effective request URI refers to an already
937   existing resource, the enclosed representation SHOULD be considered a
938   modified version of the one residing on the origin server. Otherwise, if the
939   effective request URI does not point to an existing resource, and that URI is
940   capable of being defined as a new resource by the requesting user
941   agent, the origin server can create the resource with that URI.
942</t>
943<t>   
944   If a new resource is created at the effective request URI, the origin
945   server MUST inform the user agent
946   via the 201 (Created) response. If an existing resource is modified,
947   either the 200 (OK) or 204 (No Content) response codes SHOULD be sent
948   to indicate successful completion of the request.
949</t>
950<t>   
951   If the target resource could not be created or modified, an appropriate
952   error response SHOULD be given that reflects the nature of the problem.
953   The recipient of the representation MUST NOT ignore any Content-*
954   header fields (headers starting with the prefix "Content-") that it does
955   not understand or implement
956   and MUST return a 501 (Not Implemented) response in such cases.
957</t>
958<t>
959   If the request passes through a cache that has one or more stored
960   responses for the effective request URI, those stored responses
961   SHOULD be marked as stale if the response to the PUT request
962   has a success status code. Responses to the PUT method are
963   not cacheable.
964</t>
965<t>
966   The fundamental difference between the POST and PUT requests is
967   reflected in the different meaning of the effective request URI. The URI in a
968   POST request identifies the resource that will handle the enclosed
969   representation. That resource might be a data-accepting process, a gateway to
970   some other protocol, or a document that accepts annotations.
971   In contrast, the URI in a PUT request identifies the resource for
972   which enclosed representation is a new or replacement value; the
973   user agent knows what URI is intended and the server MUST NOT attempt
974   to apply the request to some other resource.
975   If the server desires that the request be applied to a different URI,
976   it MUST send a 301 (Moved Permanently) response; the user agent MAY
977   then make its own decision regarding whether or not to redirect the
978   request.
979</t>
980<t>
981   A single resource MAY be identified by many different URIs. For
982   example, an article might have a URI for identifying "the current
983   version" which is separate from the URI identifying each particular
984   version. In this case, a PUT request on a general URI might result in
985   several other URIs being defined by the origin server.
986</t>
987<t>
988   HTTP/1.1 does not define how a PUT method affects the state of an
989   origin server.
990</t>
991<t>
992   Header fields in a PUT request that are recognized as representation
993   metadata SHOULD be applied to the resource created or modified by
994   the PUT.  Unrecognized header fields SHOULD be ignored.
995</t>
996</section>
997
998<section title="DELETE" anchor="DELETE">
999  <iref primary="true" item="DELETE method"/>
1000  <iref primary="true" item="Methods" subitem="DELETE"/>
1001<t>
1002   The DELETE method requests that the origin server delete the target
1003   resource. This method MAY be overridden by
1004   human intervention (or other means) on the origin server. The client cannot
1005   be guaranteed that the operation has been carried out, even if the
1006   status code returned from the origin server indicates that the action
1007   has been completed successfully. However, the server SHOULD NOT
1008   indicate success unless, at the time the response is given, it
1009   intends to delete the resource or move it to an inaccessible
1010   location.
1011</t>
1012<t>
1013   A successful response SHOULD be 200 (OK) if the response includes an
1014   representation describing the status, 202 (Accepted) if the action has not
1015   yet been enacted, or 204 (No Content) if the action has been enacted
1016   but the response does not include a representation.
1017</t>
1018<t>
1019   If the request passes through a cache and the effective request URI
1020   identifies one or more currently cached representations, those entries SHOULD be
1021   treated as stale. Responses to the DELETE method are not cacheable.
1022</t>
1023</section>
1024
1025<section title="TRACE" anchor="TRACE">
1026 
1027  <iref primary="true" item="TRACE method"/>
1028  <iref primary="true" item="Methods" subitem="TRACE"/>
1029<t>
1030   The TRACE method is used to invoke a remote, application-layer loop-back
1031   of the request message. The final recipient of the request
1032   SHOULD reflect the message received back to the client as the
1033   message-body of a 200 (OK) response. The final recipient is either the
1034   origin server or the first proxy or gateway to receive a Max-Forwards
1035   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1036   A TRACE request MUST NOT include a message-body.
1037</t>
1038<t>
1039   TRACE allows the client to see what is being received at the other
1040   end of the request chain and use that data for testing or diagnostic
1041   information. The value of the Via header field (Section 9.9 of <xref target="Part1"/>) is of
1042   particular interest, since it acts as a trace of the request chain.
1043   Use of the Max-Forwards header field allows the client to limit the
1044   length of the request chain, which is useful for testing a chain of
1045   proxies forwarding messages in an infinite loop.
1046</t>
1047<t>
1048   If the request is valid, the response SHOULD have a Content-Type of
1049   "message/http" (see Section 10.3.1 of <xref target="Part1"/>) and contain a message-body
1050   that encloses a copy of the entire request message.
1051   Responses to the TRACE method are not cacheable.
1052</t>
1053</section>
1054
1055<section title="CONNECT" anchor="CONNECT">
1056  <iref primary="true" item="CONNECT method"/>
1057  <iref primary="true" item="Methods" subitem="CONNECT"/>
1058<t>
1059   This specification reserves the method name CONNECT for use with a
1060   proxy that can dynamically switch to being a tunnel (e.g., SSL
1061   tunneling <xref target="RFC2817"/>).
1062</t>
1063</section>
1064</section>
1065
1066
1067<section title="Status Code Definitions" anchor="status.codes">
1068<t>
1069   Each Status-Code is described below, including any metadata required
1070   in the response.
1071</t>
1072
1073<section title="Informational 1xx" anchor="status.1xx">
1074<t>
1075   This class of status code indicates a provisional response,
1076   consisting only of the Status-Line and optional header fields, and is
1077   terminated by an empty line. There are no required header fields for this
1078   class of status code. Since HTTP/1.0 did not define any 1xx status
1079   codes, servers MUST NOT send a 1xx response to an HTTP/1.0 client
1080   except under experimental conditions.
1081</t>
1082<t>
1083   A client MUST be prepared to accept one or more 1xx status responses
1084   prior to a regular response, even if the client does not expect a 100
1085   (Continue) status message. Unexpected 1xx status responses MAY be
1086   ignored by a user agent.
1087</t>
1088<t>
1089   Proxies MUST forward 1xx responses, unless the connection between the
1090   proxy and its client has been closed, or unless the proxy itself
1091   requested the generation of the 1xx response. (For example, if a
1092   proxy adds a "Expect: 100-continue" field when it forwards a request,
1093   then it need not forward the corresponding 100 (Continue)
1094   response(s).)
1095</t>
1096
1097<section title="100 Continue" anchor="status.100">
1098  <iref primary="true" item="100 Continue (status code)"/>
1099  <iref primary="true" item="Status Codes" subitem="100 Continue"/>
1100<t>
1101   The client SHOULD continue with its request. This interim response is
1102   used to inform the client that the initial part of the request has
1103   been received and has not yet been rejected by the server. The client
1104   SHOULD continue by sending the remainder of the request or, if the
1105   request has already been completed, ignore this response. The server
1106   MUST send a final response after the request has been completed. See
1107   Section 7.2.3 of <xref target="Part1"/> for detailed discussion of the use and handling of this
1108   status code.
1109</t>
1110</section>
1111
1112<section title="101 Switching Protocols" anchor="status.101">
1113  <iref primary="true" item="101 Switching Protocols (status code)"/>
1114  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols"/>
1115<t>
1116   The server understands and is willing to comply with the client's
1117   request, via the Upgrade message header field (Section 9.8 of <xref target="Part1"/>), for a
1118   change in the application protocol being used on this connection. The
1119   server will switch protocols to those defined by the response's
1120   Upgrade header field immediately after the empty line which
1121   terminates the 101 response.
1122</t>
1123<t>
1124   The protocol SHOULD be switched only when it is advantageous to do
1125   so. For example, switching to a newer version of HTTP is advantageous
1126   over older versions, and switching to a real-time, synchronous
1127   protocol might be advantageous when delivering resources that use
1128   such features.
1129</t>
1130</section>
1131</section>
1132
1133<section title="Successful 2xx" anchor="status.2xx">
1134<t>
1135   This class of status code indicates that the client's request was
1136   successfully received, understood, and accepted.
1137</t>
1138
1139<section title="200 OK" anchor="status.200">
1140  <iref primary="true" item="200 OK (status code)"/>
1141  <iref primary="true" item="Status Codes" subitem="200 OK"/>
1142<t>
1143   The request has succeeded. The payload returned with the response
1144   is dependent on the method used in the request, for example:
1145  <list style="hanging">
1146    <t hangText="GET">
1147          a representation of the target resource is sent in the response;
1148    </t>
1149    <t hangText="HEAD">
1150          the same representation as GET, except without the message-body;
1151    </t>
1152    <t hangText="POST">
1153      a representation describing or containing the result of the action;
1154    </t>
1155    <t hangText="TRACE">
1156      a representation containing the request message as received by the
1157      end server.
1158    </t>
1159  </list>
1160</t>
1161<t>
1162   Caches MAY use a heuristic (see Section 2.3.1.1 of <xref target="Part6"/>) to determine
1163   freshness for 200 responses.
1164</t>
1165</section>
1166
1167<section title="201 Created" anchor="status.201">
1168  <iref primary="true" item="201 Created (status code)"/>
1169  <iref primary="true" item="Status Codes" subitem="201 Created"/>
1170<t>
1171   The request has been fulfilled and has resulted in a new resource being
1172   created. The newly created resource can be referenced by the URI(s)
1173   returned in the payload of the response, with the most specific URI
1174   for the resource given by a Location header field. The response
1175   SHOULD include a payload containing a list of resource
1176   characteristics and location(s) from which the user or user agent can
1177   choose the one most appropriate. The payload format is specified by
1178   the media type given in the Content-Type header field. The origin
1179   server MUST create the resource before returning the 201 status code.
1180   If the action cannot be carried out immediately, the server SHOULD
1181   respond with 202 (Accepted) response instead.
1182</t>
1183<t>
1184   A 201 response MAY contain an ETag response header field indicating
1185   the current value of the entity-tag for the representation of the resource
1186   just created (see Section 6.1 of <xref target="Part4"/>).
1187</t>
1188</section>
1189
1190<section title="202 Accepted" anchor="status.202">
1191  <iref primary="true" item="202 Accepted (status code)"/>
1192  <iref primary="true" item="Status Codes" subitem="202 Accepted"/>
1193<t>
1194   The request has been accepted for processing, but the processing has
1195   not been completed.  The request might or might not eventually be
1196   acted upon, as it might be disallowed when processing actually takes
1197   place. There is no facility for re-sending a status code from an
1198   asynchronous operation such as this.
1199</t>
1200<t>
1201   The 202 response is intentionally non-committal. Its purpose is to
1202   allow a server to accept a request for some other process (perhaps a
1203   batch-oriented process that is only run once per day) without
1204   requiring that the user agent's connection to the server persist
1205   until the process is completed. The representation returned with this
1206   response SHOULD include an indication of the request's current status
1207   and either a pointer to a status monitor or some estimate of when the
1208   user can expect the request to be fulfilled.
1209</t>
1210</section>
1211
1212<section title="203 Non-Authoritative Information" anchor="status.203">
1213  <iref primary="true" item="203 Non-Authoritative Information (status code)"/>
1214  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information"/>
1215<t>
1216   The returned metadata in the header fields is not the
1217   definitive set as available from the origin server, but is gathered
1218   from a local or a third-party copy. The set presented MAY be a subset
1219   or superset of the original version. For example, including local
1220   annotation information about the resource might result in a superset
1221   of the metadata known by the origin server. Use of this
1222   response code is not required and is only appropriate when the
1223   response would otherwise be 200 (OK).
1224</t>
1225<t>
1226   Caches MAY use a heuristic (see Section 2.3.1.1 of <xref target="Part6"/>) to determine
1227   freshness for 203 responses.
1228</t>
1229
1230</section>
1231
1232<section title="204 No Content" anchor="status.204">
1233  <iref primary="true" item="204 No Content (status code)"/>
1234  <iref primary="true" item="Status Codes" subitem="204 No Content"/>
1235<t>
1236   The server has successfully fulfilled the request, but there is no
1237   additional content to return in the response payload body.  The
1238   resource metadata and representation metadata in the response message's
1239   header fields refer to the target resource
1240   and its current representation, respectively, after the requested action.
1241   For example, if a 204 status code is received in response to a PUT
1242   and the response contains an ETag header field, then the value of
1243   that field is the current entity-tag for the representation that
1244   was successfully PUT.
1245</t>
1246<t>
1247   If the client is a user agent, it SHOULD NOT change its document view
1248   from that which caused the request to be sent. This response is
1249   primarily intended to allow input for actions to take place without
1250   causing a change to the user agent's active document view, although
1251   any new or updated metadata SHOULD be applied to the document
1252   currently in the user agent's active view.
1253</t>
1254<t>
1255   The 204 response MUST NOT include a message-body, and thus is always
1256   terminated by the first empty line after the header fields.
1257</t>
1258</section>
1259
1260<section title="205 Reset Content" anchor="status.205">
1261  <iref primary="true" item="205 Reset Content (status code)"/>
1262  <iref primary="true" item="Status Codes" subitem="205 Reset Content"/>
1263<t>
1264   The server has fulfilled the request and the user agent SHOULD reset
1265   the document view which caused the request to be sent. This response
1266   is primarily intended to allow input for actions to take place via
1267   user input, followed by a clearing of the form in which the input is
1268   given so that the user can easily initiate another input action. The
1269   response MUST NOT include a message-body.
1270</t>
1271</section>
1272
1273<section title="206 Partial Content" anchor="status.206">
1274  <iref primary="true" item="206 Partial Content (status code)"/>
1275  <iref primary="true" item="Status Codes" subitem="206 Partial Content"/>
1276 
1277<t>
1278   The server has fulfilled the partial GET request for the resource
1279   and the enclosed payload is a partial representation as defined in Section 3.1 of <xref target="Part5"/>.
1280</t>
1281<t>
1282   Caches MAY use a heuristic (see Section 2.3.1.1 of <xref target="Part6"/>) to determine
1283   freshness for 206 responses.
1284</t>
1285</section>
1286</section>
1287
1288<section title="Redirection 3xx" anchor="status.3xx">
1289<t>
1290   This class of status code indicates that further action needs to be
1291   taken by the user agent in order to fulfill the request.  The action
1292   required MAY be carried out by the user agent without interaction
1293   with the user if and only if the method used in the second request is
1294   known to be "safe", as defined in <xref target="safe.methods"/>.
1295   A client SHOULD detect infinite redirection loops, since such loops
1296   generate network traffic for each redirection.
1297</t>
1298<t><list>
1299  <t>
1300    Note: An earlier version of this specification recommended a
1301    maximum of five redirections (<xref target="RFC2068"/>, Section 10.3).
1302    Content developers need to be aware that some clients might
1303    implement such a fixed limitation.
1304  </t>
1305</list></t>
1306
1307<section title="300 Multiple Choices" anchor="status.300">
1308  <iref primary="true" item="300 Multiple Choices (status code)"/>
1309  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices"/>
1310<t>
1311   The target resource has more than one
1312   representation, each with its own specific location, and agent-driven
1313   negotiation information (Section 5 of <xref target="Part3"/>) is being provided so that
1314   the user (or user agent) can select a preferred representation by
1315   redirecting its request to that location.
1316</t>
1317<t>
1318   Unless it was a HEAD request, the response SHOULD include a representation
1319   containing a list of representation metadata and location(s) from
1320   which the user or user agent can choose the one most appropriate. The
1321   data format is specified by the media type given in the Content-Type
1322   header field. Depending upon the format and the capabilities of
1323   the user agent, selection of the most appropriate choice MAY be
1324   performed automatically. However, this specification does not define
1325   any standard for such automatic selection.
1326</t>
1327<t>
1328   If the server has a preferred choice of representation, it SHOULD
1329   include the specific URI for that representation in the Location
1330   field; user agents MAY use the Location field value for automatic
1331   redirection.
1332</t>
1333<t>
1334   Caches MAY use a heuristic (see Section 2.3.1.1 of <xref target="Part6"/>) to determine
1335   freshness for 300 responses.
1336</t>
1337
1338</section>
1339
1340<section title="301 Moved Permanently" anchor="status.301">
1341  <iref primary="true" item="301 Moved Permanently (status code)"/>
1342  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently"/>
1343<t>
1344   The target resource has been assigned a new permanent URI and any
1345   future references to this resource SHOULD use one of the returned
1346   URIs.  Clients with link editing capabilities ought to automatically
1347   re-link references to the effective request URI to one or more of the new
1348   references returned by the server, where possible.
1349</t>
1350<t>
1351   Caches MAY use a heuristic (see Section 2.3.1.1 of <xref target="Part6"/>) to determine
1352   freshness for 301 responses.
1353</t>
1354<t>
1355   The new permanent URI SHOULD be given by the Location field in the
1356   response. Unless the request method was HEAD, the representation of the
1357   response SHOULD contain a short hypertext note with a hyperlink to
1358   the new URI(s).
1359</t>
1360<t>
1361   If the 301 status code is received in response to a request method
1362   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1363   then the request MAY be automatically redirected by the user agent without
1364   confirmation.  Otherwise, the user agent MUST NOT automatically redirect the
1365   request unless it can be confirmed by the user, since this might
1366   change the conditions under which the request was issued.
1367</t>
1368<t><list>
1369  <t>
1370    Note: When automatically redirecting a POST request after
1371    receiving a 301 status code, some existing HTTP/1.0 user agents
1372    will erroneously change it into a GET request.
1373  </t>
1374</list></t>
1375</section>
1376
1377<section title="302 Found" anchor="status.302">
1378  <iref primary="true" item="302 Found (status code)"/>
1379  <iref primary="true" item="Status Codes" subitem="302 Found"/>
1380<t>
1381   The target resource resides temporarily under a different URI.
1382   Since the redirection might be altered on occasion, the client SHOULD
1383   continue to use the effective request URI for future requests.
1384</t>
1385<t>
1386   The temporary URI SHOULD be given by the Location field in the
1387   response. Unless the request method was HEAD, the representation of the
1388   response SHOULD contain a short hypertext note with a hyperlink to
1389   the new URI(s).
1390</t>
1391<t>
1392   If the 302 status code is received in response to a request method
1393   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1394   then the request MAY be automatically redirected by the user agent without
1395   confirmation.  Otherwise, the user agent MUST NOT automatically redirect the
1396   request unless it can be confirmed by the user, since this might
1397   change the conditions under which the request was issued.
1398</t>
1399<t><list>
1400  <t>
1401    Note: HTTP/1.0 (<xref target="RFC1945"/>, Section 9.3)
1402    and the first version of HTTP/1.1 (<xref target="RFC2068"/>, Section 10.3.3)
1403    specify that the client is not allowed to change the method on the
1404    redirected request.  However, most existing user agent implementations
1405    treat 302 as if it were a 303 response, performing a GET on the Location
1406    field-value regardless of the original request method. Therefore, a
1407    previous version of this specification
1408    (<xref target="RFC2616"/>, Section 10.3.3) has added the
1409    status codes
1410    <xref target="status.303" format="none">303</xref> and
1411    <xref target="status.307" format="none">307</xref> for servers that wish
1412    to make unambiguously clear which kind of reaction is expected of the
1413    client.
1414  </t>
1415</list></t>
1416</section>
1417
1418<section title="303 See Other" anchor="status.303">
1419  <iref primary="true" item="303 See Other (status code)"/>
1420  <iref primary="true" item="Status Codes" subitem="303 See Other"/>
1421<t>
1422   The server directs the user agent to a different resource, indicated
1423   by a URI in the Location header field, that provides an indirect
1424   response to the original request.  The user agent MAY perform a GET
1425   request on the URI in the Location field in order to obtain a
1426   representation corresponding to the response, be redirected again,
1427   or end with an error status.  The Location URI is not a substitute
1428   reference for the effective request URI.
1429</t>
1430<t>
1431   The 303 status code is generally applicable to any HTTP method.  It is
1432   primarily used to allow the output of a POST action to redirect
1433   the user agent to a selected resource, since doing so provides the
1434   information corresponding to the POST response in a form that
1435   can be separately identified, bookmarked, and cached independent
1436   of the original request.
1437</t>
1438<t>
1439   A 303 response to a GET request indicates that the requested
1440   resource does not have a representation of its own that can be
1441   transferred by the server over HTTP.  The Location URI indicates a
1442   resource that is descriptive of the target resource, such that the
1443   follow-on representation might be useful to recipients without
1444   implying that it adequately represents the target resource.
1445   Note that answers to the questions of what can be represented, what
1446   representations are adequate, and what might be a useful description
1447   are outside the scope of HTTP and thus entirely determined by the
1448   URI owner(s).
1449</t>
1450<t>
1451   Except for responses to a HEAD request, the representation of a 303
1452   response SHOULD contain a short hypertext note with a hyperlink
1453   to the Location URI.
1454</t>
1455</section>
1456
1457<section title="304 Not Modified" anchor="status.304">
1458  <iref primary="true" item="304 Not Modified (status code)"/>
1459  <iref primary="true" item="Status Codes" subitem="304 Not Modified"/>
1460 
1461<t>
1462   The response to the request has not been modified since the conditions
1463   indicated by the client's conditional GET request, as defined in Section 3.1 of <xref target="Part4"/>.
1464</t>
1465</section>
1466
1467<section title="305 Use Proxy" anchor="status.305">
1468  <iref primary="true" item="305 Use Proxy (status code)"/>
1469  <iref primary="true" item="Status Codes" subitem="305 Use Proxy"/>
1470<t>
1471   The 305 status code was defined in a previous version of this specification
1472   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1473</t>
1474</section>
1475
1476<section title="306 (Unused)" anchor="status.306">
1477  <iref primary="true" item="306 (Unused) (status code)"/>
1478  <iref primary="true" item="Status Codes" subitem="306 (Unused)"/>
1479<t>
1480   The 306 status code was used in a previous version of the
1481   specification, is no longer used, and the code is reserved.
1482</t>
1483</section>
1484
1485<section title="307 Temporary Redirect" anchor="status.307">
1486  <iref primary="true" item="307 Temporary Redirect (status code)"/>
1487  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect"/>
1488<t>
1489   The target resource resides temporarily under a different URI.
1490   Since the redirection can change over time, the client SHOULD
1491   continue to use the effective request URI for future requests.
1492</t>
1493<t>
1494   The temporary URI SHOULD be given by the Location field in the
1495   response. Unless the request method was HEAD, the representation of the
1496   response SHOULD contain a short hypertext note with a hyperlink to
1497   the new URI(s), since many pre-HTTP/1.1 user agents do not
1498   understand the 307 status code. Therefore, the note SHOULD contain the
1499   information necessary for a user to repeat the original request on
1500   the new URI.
1501</t>
1502<t>
1503   If the 307 status code is received in response to a request method
1504   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1505   then the request MAY be automatically redirected by the user agent without
1506   confirmation.  Otherwise, the user agent MUST NOT automatically redirect the
1507   request unless it can be confirmed by the user, since this might
1508   change the conditions under which the request was issued.
1509</t>
1510</section>
1511</section>
1512
1513<section title="Client Error 4xx" anchor="status.4xx">
1514<t>
1515   The 4xx class of status code is intended for cases in which the
1516   client seems to have erred. Except when responding to a HEAD request,
1517   the server SHOULD include a representation containing an explanation of the
1518   error situation, and whether it is a temporary or permanent
1519   condition. These status codes are applicable to any request method.
1520   User agents SHOULD display any included representation to the user.
1521</t>
1522<t>
1523   If the client is sending data, a server implementation using TCP
1524   SHOULD be careful to ensure that the client acknowledges receipt of
1525   the packet(s) containing the response, before the server closes the
1526   input connection. If the client continues sending data to the server
1527   after the close, the server's TCP stack will send a reset packet to
1528   the client, which might erase the client's unacknowledged input buffers
1529   before they can be read and interpreted by the HTTP application.
1530</t>
1531
1532<section title="400 Bad Request" anchor="status.400">
1533  <iref primary="true" item="400 Bad Request (status code)"/>
1534  <iref primary="true" item="Status Codes" subitem="400 Bad Request"/>
1535<t>
1536   The request could not be understood by the server due to malformed
1537   syntax. The client SHOULD NOT repeat the request without
1538   modifications.
1539</t>
1540</section>
1541
1542<section title="401 Unauthorized" anchor="status.401">
1543  <iref primary="true" item="401 Unauthorized (status code)"/>
1544  <iref primary="true" item="Status Codes" subitem="401 Unauthorized"/>
1545 
1546<t>
1547   The request requires user authentication (see Section 3.1 of <xref target="Part7"/>).
1548</t>
1549</section>
1550
1551<section title="402 Payment Required" anchor="status.402">
1552  <iref primary="true" item="402 Payment Required (status code)"/>
1553  <iref primary="true" item="Status Codes" subitem="402 Payment Required"/>
1554<t>
1555   This code is reserved for future use.
1556</t>
1557</section>
1558
1559<section title="403 Forbidden" anchor="status.403">
1560  <iref primary="true" item="403 Forbidden (status code)"/>
1561  <iref primary="true" item="Status Codes" subitem="403 Forbidden"/>
1562<t>
1563   The server understood the request, but is refusing to fulfill it.
1564   Authorization will not help and the request SHOULD NOT  be repeated.
1565   If the request method was not HEAD and the server wishes to make
1566   public why the request has not been fulfilled, it SHOULD describe the
1567   reason for the refusal in the representation.  If the server does not wish to
1568   make this information available to the client, the status code 404
1569   (Not Found) can be used instead.
1570</t>
1571</section>
1572
1573<section title="404 Not Found" anchor="status.404">
1574  <iref primary="true" item="404 Not Found (status code)"/>
1575  <iref primary="true" item="Status Codes" subitem="404 Not Found"/>
1576<t>
1577   The server has not found anything matching the effective request URI. No
1578   indication is given of whether the condition is temporary or
1579   permanent. The 410 (Gone) status code SHOULD be used if the server
1580   knows, through some internally configurable mechanism, that an old
1581   resource is permanently unavailable and has no forwarding address.
1582   This status code is commonly used when the server does not wish to
1583   reveal exactly why the request has been refused, or when no other
1584   response is applicable.
1585</t>
1586</section>
1587
1588<section title="405 Method Not Allowed" anchor="status.405">
1589  <iref primary="true" item="405 Method Not Allowed (status code)"/>
1590  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed"/>
1591<t>
1592   The method specified in the Request-Line is not allowed for the target
1593   resource. The response MUST include an
1594   Allow header field containing a list of valid methods for the requested
1595   resource.
1596</t>
1597</section>
1598
1599<section title="406 Not Acceptable" anchor="status.406">
1600  <iref primary="true" item="406 Not Acceptable (status code)"/>
1601  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable"/>
1602<t>
1603   The resource identified by the request is only capable of generating
1604   response representations which have content characteristics not acceptable
1605   according to the accept header fields sent in the request.
1606</t>
1607<t>
1608   Unless it was a HEAD request, the response SHOULD include a representation
1609   containing a list of available representation characteristics and location(s)
1610   from which the user or user agent can choose the one most
1611   appropriate. The data format is specified by the media type given
1612   in the Content-Type header field. Depending upon the format and the
1613   capabilities of the user agent, selection of the most appropriate
1614   choice MAY be performed automatically. However, this specification
1615   does not define any standard for such automatic selection.
1616</t>
1617<t><list>
1618  <t>
1619    Note: HTTP/1.1 servers are allowed to return responses which are
1620    not acceptable according to the accept header fields sent in the
1621    request. In some cases, this might even be preferable to sending a
1622    406 response. User agents are encouraged to inspect the header fields of
1623    an incoming response to determine if it is acceptable.
1624  </t>
1625</list></t>
1626<t>
1627   If the response could be unacceptable, a user agent SHOULD
1628   temporarily stop receipt of more data and query the user for a
1629   decision on further actions.
1630</t>
1631</section>
1632
1633<section title="407 Proxy Authentication Required" anchor="status.407">
1634  <iref primary="true" item="407 Proxy Authentication Required (status code)"/>
1635  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required"/>
1636<t>
1637   This code is similar to 401 (Unauthorized), but indicates that the
1638   client must first authenticate itself with the proxy (see Section 3.2 of <xref target="Part7"/>).
1639</t>
1640</section>
1641
1642<section title="408 Request Timeout" anchor="status.408">
1643  <iref primary="true" item="408 Request Timeout (status code)"/>
1644  <iref primary="true" item="Status Codes" subitem="408 Request Timeout"/>
1645<t>
1646   The client did not produce a request within the time that the server
1647   was prepared to wait. The client MAY repeat the request without
1648   modifications at any later time.
1649</t>
1650</section>
1651
1652<section title="409 Conflict" anchor="status.409">
1653  <iref primary="true" item="409 Conflict (status code)"/>
1654  <iref primary="true" item="Status Codes" subitem="409 Conflict"/>
1655<t>
1656   The request could not be completed due to a conflict with the current
1657   state of the resource. This code is only allowed in situations where
1658   it is expected that the user might be able to resolve the conflict
1659   and resubmit the request. The response body SHOULD include enough
1660   information for the user to recognize the source of the conflict.
1661   Ideally, the response representation would include enough information for the
1662   user or user agent to fix the problem; however, that might not be
1663   possible and is not required.
1664</t>
1665<t>
1666   Conflicts are most likely to occur in response to a PUT request. For
1667   example, if versioning were being used and the representation being PUT
1668   included changes to a resource which conflict with those made by an
1669   earlier (third-party) request, the server might use the 409 response
1670   to indicate that it can't complete the request. In this case, the
1671   response representation would likely contain a list of the differences
1672   between the two versions in a format defined by the response
1673   Content-Type.
1674</t>
1675</section>
1676
1677<section title="410 Gone" anchor="status.410">
1678  <iref primary="true" item="410 Gone (status code)"/>
1679  <iref primary="true" item="Status Codes" subitem="410 Gone"/>
1680<t>
1681   The target resource is no longer available at the server and no
1682   forwarding address is known. This condition is expected to be
1683   considered permanent. Clients with link editing capabilities SHOULD
1684   delete references to the effective request URI after user approval. If the
1685   server does not know, or has no facility to determine, whether or not
1686   the condition is permanent, the status code 404 (Not Found) SHOULD be
1687   used instead.
1688</t>
1689<t>
1690   The 410 response is primarily intended to assist the task of web
1691   maintenance by notifying the recipient that the resource is
1692   intentionally unavailable and that the server owners desire that
1693   remote links to that resource be removed. Such an event is common for
1694   limited-time, promotional services and for resources belonging to
1695   individuals no longer working at the server's site. It is not
1696   necessary to mark all permanently unavailable resources as "gone" or
1697   to keep the mark for any length of time -- that is left to the
1698   discretion of the server owner.
1699</t>
1700<t>
1701   Caches MAY use a heuristic (see Section 2.3.1.1 of <xref target="Part6"/>) to determine freshness
1702   for 410 responses.
1703</t>
1704
1705</section>
1706
1707<section title="411 Length Required" anchor="status.411">
1708  <iref primary="true" item="411 Length Required (status code)"/>
1709  <iref primary="true" item="Status Codes" subitem="411 Length Required"/>
1710<t>
1711   The server refuses to accept the request without a defined Content-Length.
1712   The client MAY repeat the request if it adds a valid
1713   Content-Length header field containing the length of the message-body
1714   in the request message.
1715</t>
1716</section>
1717
1718<section title="412 Precondition Failed" anchor="status.412">
1719  <iref primary="true" item="412 Precondition Failed (status code)"/>
1720  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed"/>
1721 
1722<t>
1723   The precondition given in one or more of the request-header fields
1724   evaluated to false when it was tested on the server, as defined in
1725   Section 3.2 of <xref target="Part4"/>.
1726</t>
1727</section>
1728
1729<section title="413 Request Entity Too Large" anchor="status.413">
1730  <iref primary="true" item="413 Request Entity Too Large (status code)"/>
1731  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large"/>
1732<t>
1733   The server is refusing to process a request because the request
1734   representation is larger than the server is willing or able to process. The
1735   server MAY close the connection to prevent the client from continuing
1736   the request.
1737</t>
1738<t>
1739   If the condition is temporary, the server SHOULD include a Retry-After
1740   header field to indicate that it is temporary and after what
1741   time the client MAY try again.
1742</t>
1743</section>
1744
1745<section title="414 URI Too Long" anchor="status.414">
1746  <iref primary="true" item="414 URI Too Long (status code)"/>
1747  <iref primary="true" item="Status Codes" subitem="414 URI Too Long"/>
1748<t>
1749   The server is refusing to service the request because the effective request URI
1750   is longer than the server is willing to interpret. This rare
1751   condition is only likely to occur when a client has improperly
1752   converted a POST request to a GET request with long query
1753   information, when the client has descended into a URI "black hole" of
1754   redirection (e.g., a redirected URI prefix that points to a suffix of
1755   itself), or when the server is under attack by a client attempting to
1756   exploit security holes present in some servers using fixed-length
1757   buffers for reading or manipulating the effective request URI.
1758</t>
1759</section>
1760
1761<section title="415 Unsupported Media Type" anchor="status.415">
1762  <iref primary="true" item="415 Unsupported Media Type (status code)"/>
1763  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type"/>
1764<t>
1765   The server is refusing to service the request because the representation of
1766   the request is in a format not supported by the target resource
1767   for the requested method.
1768</t>
1769</section>
1770
1771<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1772  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)"/>
1773  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable"/>
1774 
1775<t>
1776   The request included a Range request-header field (Section 5.4 of <xref target="Part5"/>) and none of
1777   the range-specifier values in this field overlap the current extent
1778   of the selected resource. See Section 3.2 of <xref target="Part5"/>.
1779</t>
1780</section>
1781
1782<section title="417 Expectation Failed" anchor="status.417">
1783  <iref primary="true" item="417 Expectation Failed (status code)"/>
1784  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed"/>
1785<t>
1786   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1787   could not be met by this server, or, if the server is a proxy,
1788   the server has unambiguous evidence that the request could not be met
1789   by the next-hop server.
1790</t>
1791</section>
1792</section>
1793
1794<section title="Server Error 5xx" anchor="status.5xx">
1795<t>
1796   Response status codes beginning with the digit "5" indicate cases in
1797   which the server is aware that it has erred or is incapable of
1798   performing the request. Except when responding to a HEAD request, the
1799   server SHOULD include a representation containing an explanation of the
1800   error situation, and whether it is a temporary or permanent
1801   condition. User agents SHOULD display any included representation to the
1802   user. These response codes are applicable to any request method.
1803</t>
1804
1805<section title="500 Internal Server Error" anchor="status.500">
1806  <iref primary="true" item="500 Internal Server Error (status code)"/>
1807  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error"/>
1808<t>
1809   The server encountered an unexpected condition which prevented it
1810   from fulfilling the request.
1811</t>
1812</section>
1813
1814<section title="501 Not Implemented" anchor="status.501">
1815  <iref primary="true" item="501 Not Implemented (status code)"/>
1816  <iref primary="true" item="Status Codes" subitem="501 Not Implemented"/>
1817<t>
1818   The server does not support the functionality required to fulfill the
1819   request. This is the appropriate response when the server does not
1820   recognize the request method and is not capable of supporting it for
1821   any resource.
1822</t>
1823</section>
1824
1825<section title="502 Bad Gateway" anchor="status.502">
1826  <iref primary="true" item="502 Bad Gateway (status code)"/>
1827  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway"/>
1828<t>
1829   The server, while acting as a gateway or proxy, received an invalid
1830   response from the upstream server it accessed in attempting to
1831   fulfill the request.
1832</t>
1833</section>
1834
1835<section title="503 Service Unavailable" anchor="status.503">
1836  <iref primary="true" item="503 Service Unavailable (status code)"/>
1837  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable"/>
1838<t>
1839   The server is currently unable to handle the request due to a
1840   temporary overloading or maintenance of the server. The implication
1841   is that this is a temporary condition which will be alleviated after
1842   some delay. If known, the length of the delay MAY be indicated in a
1843   Retry-After header field. If no Retry-After is given, the client SHOULD
1844   handle the response as it would for a 500 response.
1845</t>
1846<t><list>
1847  <t>
1848    Note: The existence of the 503 status code does not imply that a
1849    server must use it when becoming overloaded. Some servers might wish
1850    to simply refuse the connection.
1851  </t>
1852</list></t>
1853</section>
1854
1855<section title="504 Gateway Timeout" anchor="status.504">
1856  <iref primary="true" item="504 Gateway Timeout (status code)"/>
1857  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout"/>
1858<t>
1859   The server, while acting as a gateway or proxy, did not receive a
1860   timely response from the upstream server specified by the URI (e.g.,
1861   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
1862   to access in attempting to complete the request.
1863</t>
1864<t><list>
1865  <t>
1866    Note to implementors: some deployed proxies are known to
1867    return 400 or 500 when DNS lookups time out.
1868  </t>
1869</list></t>
1870</section>
1871
1872<section title="505 HTTP Version Not Supported" anchor="status.505">
1873  <iref primary="true" item="505 HTTP Version Not Supported (status code)"/>
1874  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported"/>
1875<t>
1876   The server does not support, or refuses to support, the protocol
1877   version that was used in the request message. The server is
1878   indicating that it is unable or unwilling to complete the request
1879   using the same major version as the client, as described in Section 2.5 of <xref target="Part1"/>,
1880   other than with this error message. The response SHOULD contain
1881   a representation describing why that version is not supported and what other
1882   protocols are supported by that server.
1883</t>
1884
1885</section>
1886</section>
1887</section>
1888
1889
1890<section title="Header Field Definitions" anchor="header.fields">
1891<t>
1892   This section defines the syntax and semantics of HTTP/1.1 header fields
1893   related to request and response semantics.
1894</t>
1895
1896<section title="Allow" anchor="header.allow">
1897  <iref primary="true" item="Allow header"/>
1898  <iref primary="true" item="Headers" subitem="Allow"/>
1899 
1900 
1901<t>
1902   The "Allow" response-header field lists the set of methods advertised as
1903   supported by the target resource. The purpose of
1904   this field is strictly to inform the recipient of valid methods
1905   associated with the resource.
1906</t>
1907<figure><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/><artwork type="abnf2616"><![CDATA[
1908  Allow   = "Allow" ":" OWS Allow-v
1909  Allow-v = #Method
1910]]></artwork></figure>
1911<t>
1912      Example of use:
1913</t>
1914<figure><artwork type="example"><![CDATA[
1915  Allow: GET, HEAD, PUT
1916]]></artwork></figure>
1917<t>
1918      The actual set of allowed methods is defined
1919      by the origin server at the time of each request.
1920</t>
1921<t>
1922      A proxy MUST NOT modify the Allow header field even if it does not
1923      understand all the methods specified, since the user agent might
1924      have other means of communicating with the origin server.
1925</t>
1926</section>
1927
1928<section title="Expect" anchor="header.expect">
1929  <iref primary="true" item="Expect header"/>
1930  <iref primary="true" item="Headers" subitem="Expect"/>
1931 
1932 
1933 
1934 
1935 
1936<t>
1937   The "Expect" request-header field is used to indicate that particular
1938   server behaviors are required by the client.
1939</t>
1940<figure><iref primary="true" item="Grammar" subitem="Expect"/><iref primary="true" item="Grammar" subitem="Expect-v"/><iref primary="true" item="Grammar" subitem="expectation"/><iref primary="true" item="Grammar" subitem="expectation-extension"/><iref primary="true" item="Grammar" subitem="expect-params"/><artwork type="abnf2616"><![CDATA[
1941  Expect       = "Expect" ":" OWS Expect-v
1942  Expect-v     = 1#expectation
1943 
1944  expectation  = "100-continue" / expectation-extension
1945  expectation-extension = token [ "=" ( token / quoted-string )
1946                           *expect-params ]
1947  expect-params = ";" token [ "=" ( token / quoted-string ) ]
1948]]></artwork></figure>
1949<t>
1950   A server that does not understand or is unable to comply with any of
1951   the expectation values in the Expect field of a request MUST respond
1952   with appropriate error status code. The server MUST respond with a 417
1953   (Expectation Failed) status code if any of the expectations cannot be met
1954   or, if there are other problems with the request, some other 4xx
1955   status code.
1956</t>
1957<t>
1958   This header field is defined with extensible syntax to allow for
1959   future extensions. If a server receives a request containing an
1960   Expect field that includes an expectation-extension that it does not
1961   support, it MUST respond with a 417 (Expectation Failed) status code.
1962</t>
1963<t>
1964   Comparison of expectation values is case-insensitive for unquoted
1965   tokens (including the 100-continue token), and is case-sensitive for
1966   quoted-string expectation-extensions.
1967</t>
1968<t>
1969   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy MUST
1970   return a 417 (Expectation Failed) status code if it receives a request
1971   with an expectation that it cannot meet. However, the Expect
1972   request-header field itself is end-to-end; it MUST be forwarded if the
1973   request is forwarded.
1974</t>
1975<t>
1976   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1977   Expect header field.
1978</t>
1979<t>
1980   See Section 7.2.3 of <xref target="Part1"/> for the use of the 100 (Continue) status code.
1981</t>
1982</section>
1983
1984<section title="From" anchor="header.from">
1985  <iref primary="true" item="From header"/>
1986  <iref primary="true" item="Headers" subitem="From"/>
1987 
1988 
1989 
1990<t>
1991   The "From" request-header field, if given, SHOULD contain an Internet
1992   e-mail address for the human user who controls the requesting user
1993   agent. The address SHOULD be machine-usable, as defined by "mailbox"
1994   in Section 3.4 of <xref target="RFC5322"/>:
1995</t>
1996<figure><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/><artwork type="abnf2616"><![CDATA[
1997  From    = "From" ":" OWS From-v
1998  From-v  = mailbox
1999 
2000  mailbox = <mailbox, defined in [RFC5322], Section 3.4>
2001]]></artwork></figure>
2002<t>
2003   An example is:
2004</t>
2005<figure><artwork type="example"><![CDATA[
2006  From: webmaster@example.org
2007]]></artwork></figure>
2008<t>
2009   This header field MAY be used for logging purposes and as a means for
2010   identifying the source of invalid or unwanted requests. It SHOULD NOT
2011   be used as an insecure form of access protection. The interpretation
2012   of this field is that the request is being performed on behalf of the
2013   person given, who accepts responsibility for the method performed. In
2014   particular, robot agents SHOULD include this header field so that the
2015   person responsible for running the robot can be contacted if problems
2016   occur on the receiving end.
2017</t>
2018<t>
2019   The Internet e-mail address in this field MAY be separate from the
2020   Internet host which issued the request. For example, when a request
2021   is passed through a proxy the original issuer's address SHOULD be
2022   used.
2023</t>
2024<t>
2025   The client SHOULD NOT  send the From header field without the user's
2026   approval, as it might conflict with the user's privacy interests or
2027   their site's security policy. It is strongly recommended that the
2028   user be able to disable, enable, and modify the value of this field
2029   at any time prior to a request.
2030</t>
2031</section>
2032
2033<section title="Location" anchor="header.location">
2034  <iref primary="true" item="Location header"/>
2035  <iref primary="true" item="Headers" subitem="Location"/>
2036 
2037 
2038<t>
2039   The "Location" response-header field is used to identify a newly created
2040   resource, or to redirect the recipient to a different location for
2041   completion of the request.
2042</t>
2043<t>
2044   For 201 (Created) responses, the Location is the URI of the new resource
2045   which was created by the request. For 3xx responses, the location SHOULD
2046   indicate the server's preferred URI for automatic redirection to the
2047   resource.
2048</t>
2049<t>
2050   The field value consists of a single URI-reference. When it has the form
2051   of a relative reference (<xref target="RFC3986"/>, Section 4.2),
2052   the final value is computed by resolving it against the effective request
2053   URI (<xref target="RFC3986"/>, Section 5).
2054</t>
2055<figure><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/><artwork type="abnf2616"><![CDATA[
2056  Location       = "Location" ":" OWS Location-v
2057  Location-v     = URI-reference
2058]]></artwork></figure>
2059<figure>
2060<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical WSP below, it's necessary this way for xml2rfc-->
2061<artwork type="example"><![CDATA[
2062  Location: http://www.example.org/pub/WWW/People.html#tim
2063]]></artwork></figure><figure><artwork type="example"><![CDATA[  Location: /index.html
2064]]></artwork></figure>
2065<t>
2066   There are circumstances in which a fragment identifier in a Location URI
2067   would not be appropriate:
2068   <list style="symbols">
2069      <t>With a 201 Created response, because in this usage the Location header
2070      field specifies the URI for the entire created resource.</t>
2071      <t>With 305 Use Proxy.</t>
2072   </list>
2073</t>
2074<t><list>
2075  <t>
2076    Note: This specification does not define precedence rules
2077    for the case where the original URI, as navigated to by the user
2078    agent, and the Location header field value both contain fragment
2079    identifiers.
2080  </t>
2081</list></t>
2082<t><list>
2083  <t>
2084    Note: The Content-Location header field (Section 6.7 of <xref target="Part3"/>) differs
2085    from Location in that the Content-Location identifies the most specific
2086    resource corresponding to the enclosed representation.
2087    It is therefore possible for a response to contain header fields for
2088    both Location and Content-Location.
2089  </t>
2090</list></t>
2091</section>
2092
2093<section title="Max-Forwards" anchor="header.max-forwards">
2094  <iref primary="true" item="Max-Forwards header"/>
2095  <iref primary="true" item="Headers" subitem="Max-Forwards"/>
2096 
2097 
2098<t>
2099   The "Max-Forwards" request-header field provides a mechanism with the
2100   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2101   methods to limit the number of times that the request is forwarded by
2102   proxies or gateways. This can be useful when the client is attempting to
2103   trace a request which appears to be failing or looping in mid-chain.
2104</t>
2105<figure><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/><artwork type="abnf2616"><![CDATA[
2106  Max-Forwards   = "Max-Forwards" ":" OWS Max-Forwards-v
2107  Max-Forwards-v = 1*DIGIT
2108]]></artwork></figure>
2109<t>
2110   The Max-Forwards value is a decimal integer indicating the remaining
2111   number of times this request message can be forwarded.
2112</t>
2113<t>
2114   Each proxy or gateway recipient of a TRACE or OPTIONS request
2115   containing a Max-Forwards header field MUST check and update its
2116   value prior to forwarding the request. If the received value is zero
2117   (0), the recipient MUST NOT forward the request; instead, it MUST
2118   respond as the final recipient. If the received Max-Forwards value is
2119   greater than zero, then the forwarded message MUST contain an updated
2120   Max-Forwards field with a value decremented by one (1).
2121</t>
2122<t>
2123   The Max-Forwards header field MAY be ignored for all other methods
2124   defined by this specification and for any extension methods for which
2125   it is not explicitly referred to as part of that method definition.
2126</t>
2127</section>
2128
2129<section title="Referer" anchor="header.referer">
2130  <iref primary="true" item="Referer header"/>
2131  <iref primary="true" item="Headers" subitem="Referer"/>
2132 
2133 
2134<t>
2135   The "Referer" [sic] request-header field allows the client to specify the
2136   URI of the resource from which the effective request URI was obtained (the
2137   "referrer", although the header field is misspelled.).
2138</t>
2139<t>
2140   The Referer header field allows servers to generate lists of back-links to
2141   resources for interest, logging, optimized caching, etc. It also allows
2142   obsolete or mistyped links to be traced for maintenance. Some servers use
2143   Referer as a means of controlling where they allow links from (so-called
2144   "deep linking"), but legitimate requests do not always
2145   contain a Referer header field.
2146</t>
2147<t>
2148   If the effective request URI was obtained from a source that does not have its own
2149   URI (e.g., input from the user keyboard), the Referer field MUST either be
2150   sent with the value "about:blank", or not be sent at all. Note that this
2151   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2152</t>
2153<figure><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/><artwork type="abnf2616"><![CDATA[
2154  Referer        = "Referer" ":" OWS Referer-v
2155  Referer-v      = absolute-URI / partial-URI
2156]]></artwork></figure>
2157<t>
2158   Example:
2159</t>
2160<figure><artwork type="example"><![CDATA[
2161  Referer: http://www.example.org/hypertext/Overview.html
2162]]></artwork></figure>
2163<t>
2164   If the field value is a relative URI, it SHOULD be interpreted
2165   relative to the effective request URI. The URI MUST NOT include a fragment. See
2166   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2167</t>
2168</section>
2169
2170<section title="Retry-After" anchor="header.retry-after">
2171  <iref primary="true" item="Retry-After header"/>
2172  <iref primary="true" item="Headers" subitem="Retry-After"/>
2173 
2174 
2175<t>
2176   The response-header "Retry-After" field can be used with a 503 (Service
2177   Unavailable) response to indicate how long the service is expected to
2178   be unavailable to the requesting client. This field MAY also be used
2179   with any 3xx (Redirection) response to indicate the minimum time the
2180   user-agent is asked wait before issuing the redirected request.
2181</t>
2182<t>
2183   The value of this field can be either an HTTP-date or an integer number
2184   of seconds (in decimal) after the time of the response.
2185</t>
2186<figure><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/><artwork type="abnf2616"><![CDATA[
2187  Retry-After   = "Retry-After" ":" OWS Retry-After-v
2188  Retry-After-v = HTTP-date / delta-seconds
2189]]></artwork></figure>
2190<t anchor="rule.delta-seconds">
2191 
2192   Time spans are non-negative decimal integers, representing time in
2193   seconds.
2194</t>
2195<figure><iref primary="true" item="Grammar" subitem="delta-seconds"/><artwork type="abnf2616"><![CDATA[
2196  delta-seconds  = 1*DIGIT
2197]]></artwork></figure>
2198<t>
2199   Two examples of its use are
2200</t>
2201<figure><artwork type="example"><![CDATA[
2202  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2203  Retry-After: 120
2204]]></artwork></figure>
2205<t>
2206   In the latter example, the delay is 2 minutes.
2207</t>
2208</section>
2209
2210<section title="Server" anchor="header.server">
2211  <iref primary="true" item="Server header"/>
2212  <iref primary="true" item="Headers" subitem="Server"/>
2213 
2214 
2215<t>
2216   The "Server" response-header field contains information about the
2217   software used by the origin server to handle the request.
2218</t>
2219<t>
2220   The field can contain multiple product tokens (Section 6.3 of <xref target="Part1"/>) and
2221   comments (Section 3.2 of <xref target="Part1"/>) identifying the server and any significant
2222   subproducts. The product tokens are listed in order of their significance
2223   for identifying the application.
2224</t>
2225<figure><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/><artwork type="abnf2616"><![CDATA[
2226  Server         = "Server" ":" OWS Server-v
2227  Server-v       = product
2228                   *( RWS ( product / comment ) )
2229]]></artwork></figure>
2230<t>
2231   Example:
2232</t>
2233<figure><artwork type="example"><![CDATA[
2234  Server: CERN/3.0 libwww/2.17
2235]]></artwork></figure>
2236<t>
2237   If the response is being forwarded through a proxy, the proxy
2238   application MUST NOT modify the Server response-header field. Instead, it
2239   MUST include a Via field (as described in Section 9.9 of <xref target="Part1"/>).
2240</t>
2241<t><list>
2242  <t>
2243    Note: Revealing the specific software version of the server might
2244    allow the server machine to become more vulnerable to attacks
2245    against software that is known to contain security holes. Server
2246    implementors are encouraged to make this field a configurable
2247    option.
2248  </t>
2249</list></t>
2250</section>
2251
2252<section title="User-Agent" anchor="header.user-agent">
2253  <iref primary="true" item="User-Agent header"/>
2254  <iref primary="true" item="Headers" subitem="User-Agent"/>
2255 
2256 
2257<t>
2258   The "User-Agent" request-header field contains information about the user
2259   agent originating the request. User agents SHOULD include this field with
2260   requests.
2261</t>
2262<t>
2263   Typically, it is used for statistical purposes, the tracing of protocol
2264   violations, and tailoring responses to avoid particular user agent
2265   limitations.
2266</t>
2267<t>
2268   The field can contain multiple product tokens (Section 6.3 of <xref target="Part1"/>)
2269   and comments (Section 3.2 of <xref target="Part1"/>) identifying the agent and its
2270   significant subproducts. By convention, the product tokens are listed in
2271   order of their significance for identifying the application.
2272</t>
2273<t>
2274   Because this field is usually sent on every request a user agent makes,
2275   implementations are encouraged not to include needlessly fine-grained
2276   detail, and to limit (or even prohibit) the addition of subproducts by third
2277   parties. Overly long and detailed User-Agent field values make requests
2278   larger and can also be used to identify ("fingerprint") the user against
2279   their wishes.
2280</t>
2281<t>
2282   Likewise, implementations are encouraged not to use the product tokens of
2283   other implementations in order to declare compatibility with them, as this
2284   circumvents the purpose of the field. Finally, they are encouraged not to
2285   use comments to identify products; doing so makes the field value more
2286   difficult to parse.
2287</t>
2288<figure><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/><artwork type="abnf2616"><![CDATA[
2289  User-Agent     = "User-Agent" ":" OWS User-Agent-v
2290  User-Agent-v   = product
2291                   *( RWS ( product / comment ) )
2292]]></artwork></figure>
2293<t>
2294   Example:
2295</t>
2296<figure><artwork type="example"><![CDATA[
2297  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2298]]></artwork></figure>
2299</section>
2300
2301</section>
2302
2303<section title="IANA Considerations" anchor="IANA.considerations">
2304
2305<section title="Method Registry" anchor="method.registration">
2306<t>
2307  The registration procedure for HTTP Methods is defined by
2308  <xref target="method.registry"/> of this document.
2309</t>
2310<t>
2311   The HTTP Method Registry shall be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2312   and be populated with the registrations below:
2313</t>
2314
2315<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2316<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2317   <ttcol>Method</ttcol>
2318   <ttcol>Safe</ttcol>
2319   <ttcol>Reference</ttcol>
2320   <c>CONNECT</c>
2321   <c>no</c>
2322   <c>
2323      <xref target="CONNECT"/>
2324   </c>
2325   <c>DELETE</c>
2326   <c>no</c>
2327   <c>
2328      <xref target="DELETE"/>
2329   </c>
2330   <c>GET</c>
2331   <c>yes</c>
2332   <c>
2333      <xref target="GET"/>
2334   </c>
2335   <c>HEAD</c>
2336   <c>yes</c>
2337   <c>
2338      <xref target="HEAD"/>
2339   </c>
2340   <c>OPTIONS</c>
2341   <c>yes</c>
2342   <c>
2343      <xref target="OPTIONS"/>
2344   </c>
2345   <c>POST</c>
2346   <c>no</c>
2347   <c>
2348      <xref target="POST"/>
2349   </c>
2350   <c>PUT</c>
2351   <c>no</c>
2352   <c>
2353      <xref target="PUT"/>
2354   </c>
2355   <c>TRACE</c>
2356   <c>yes</c>
2357   <c>
2358      <xref target="TRACE"/>
2359   </c>
2360</texttable>
2361<!--(END)-->
2362
2363</section>
2364
2365<section title="Status Code Registry" anchor="status.code.registration">
2366<t>
2367   The registration procedure for HTTP Status Codes -- previously defined
2368   in Section 7.1 of <xref target="RFC2817"/> -- is now defined
2369   by <xref target="status.code.registry"/> of this document.
2370</t>
2371<t>
2372   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2373   shall be updated with the registrations below:
2374</t>
2375
2376<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2377<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2378   <ttcol>Value</ttcol>
2379   <ttcol>Description</ttcol>
2380   <ttcol>Reference</ttcol>
2381   <c>100</c>
2382   <c>Continue</c>
2383   <c>
2384      <xref target="status.100"/>
2385   </c>
2386   <c>101</c>
2387   <c>Switching Protocols</c>
2388   <c>
2389      <xref target="status.101"/>
2390   </c>
2391   <c>200</c>
2392   <c>OK</c>
2393   <c>
2394      <xref target="status.200"/>
2395   </c>
2396   <c>201</c>
2397   <c>Created</c>
2398   <c>
2399      <xref target="status.201"/>
2400   </c>
2401   <c>202</c>
2402   <c>Accepted</c>
2403   <c>
2404      <xref target="status.202"/>
2405   </c>
2406   <c>203</c>
2407   <c>Non-Authoritative Information</c>
2408   <c>
2409      <xref target="status.203"/>
2410   </c>
2411   <c>204</c>
2412   <c>No Content</c>
2413   <c>
2414      <xref target="status.204"/>
2415   </c>
2416   <c>205</c>
2417   <c>Reset Content</c>
2418   <c>
2419      <xref target="status.205"/>
2420   </c>
2421   <c>300</c>
2422   <c>Multiple Choices</c>
2423   <c>
2424      <xref target="status.300"/>
2425   </c>
2426   <c>301</c>
2427   <c>Moved Permanently</c>
2428   <c>
2429      <xref target="status.301"/>
2430   </c>
2431   <c>302</c>
2432   <c>Found</c>
2433   <c>
2434      <xref target="status.302"/>
2435   </c>
2436   <c>303</c>
2437   <c>See Other</c>
2438   <c>
2439      <xref target="status.303"/>
2440   </c>
2441   <c>305</c>
2442   <c>Use Proxy</c>
2443   <c>
2444      <xref target="status.305"/>
2445   </c>
2446   <c>306</c>
2447   <c>(Unused)</c>
2448   <c>
2449      <xref target="status.306"/>
2450   </c>
2451   <c>307</c>
2452   <c>Temporary Redirect</c>
2453   <c>
2454      <xref target="status.307"/>
2455   </c>
2456   <c>400</c>
2457   <c>Bad Request</c>
2458   <c>
2459      <xref target="status.400"/>
2460   </c>
2461   <c>402</c>
2462   <c>Payment Required</c>
2463   <c>
2464      <xref target="status.402"/>
2465   </c>
2466   <c>403</c>
2467   <c>Forbidden</c>
2468   <c>
2469      <xref target="status.403"/>
2470   </c>
2471   <c>404</c>
2472   <c>Not Found</c>
2473   <c>
2474      <xref target="status.404"/>
2475   </c>
2476   <c>405</c>
2477   <c>Method Not Allowed</c>
2478   <c>
2479      <xref target="status.405"/>
2480   </c>
2481   <c>406</c>
2482   <c>Not Acceptable</c>
2483   <c>
2484      <xref target="status.406"/>
2485   </c>
2486   <c>407</c>
2487   <c>Proxy Authentication Required</c>
2488   <c>
2489      <xref target="status.407"/>
2490   </c>
2491   <c>408</c>
2492   <c>Request Timeout</c>
2493   <c>
2494      <xref target="status.408"/>
2495   </c>
2496   <c>409</c>
2497   <c>Conflict</c>
2498   <c>
2499      <xref target="status.409"/>
2500   </c>
2501   <c>410</c>
2502   <c>Gone</c>
2503   <c>
2504      <xref target="status.410"/>
2505   </c>
2506   <c>411</c>
2507   <c>Length Required</c>
2508   <c>
2509      <xref target="status.411"/>
2510   </c>
2511   <c>413</c>
2512   <c>Request Entity Too Large</c>
2513   <c>
2514      <xref target="status.413"/>
2515   </c>
2516   <c>414</c>
2517   <c>URI Too Long</c>
2518   <c>
2519      <xref target="status.414"/>
2520   </c>
2521   <c>415</c>
2522   <c>Unsupported Media Type</c>
2523   <c>
2524      <xref target="status.415"/>
2525   </c>
2526   <c>417</c>
2527   <c>Expectation Failed</c>
2528   <c>
2529      <xref target="status.417"/>
2530   </c>
2531   <c>500</c>
2532   <c>Internal Server Error</c>
2533   <c>
2534      <xref target="status.500"/>
2535   </c>
2536   <c>501</c>
2537   <c>Not Implemented</c>
2538   <c>
2539      <xref target="status.501"/>
2540   </c>
2541   <c>502</c>
2542   <c>Bad Gateway</c>
2543   <c>
2544      <xref target="status.502"/>
2545   </c>
2546   <c>503</c>
2547   <c>Service Unavailable</c>
2548   <c>
2549      <xref target="status.503"/>
2550   </c>
2551   <c>504</c>
2552   <c>Gateway Timeout</c>
2553   <c>
2554      <xref target="status.504"/>
2555   </c>
2556   <c>505</c>
2557   <c>HTTP Version Not Supported</c>
2558   <c>
2559      <xref target="status.505"/>
2560   </c>
2561</texttable>
2562<!--(END)-->
2563
2564</section>
2565<section title="Header Field Registration" anchor="header.field.registration">
2566<t>
2567   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
2568   with the permanent registrations below (see <xref target="RFC3864"/>):
2569</t>
2570
2571<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2572<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2573   <ttcol>Header Field Name</ttcol>
2574   <ttcol>Protocol</ttcol>
2575   <ttcol>Status</ttcol>
2576   <ttcol>Reference</ttcol>
2577
2578   <c>Allow</c>
2579   <c>http</c>
2580   <c>standard</c>
2581   <c>
2582      <xref target="header.allow"/>
2583   </c>
2584   <c>Expect</c>
2585   <c>http</c>
2586   <c>standard</c>
2587   <c>
2588      <xref target="header.expect"/>
2589   </c>
2590   <c>From</c>
2591   <c>http</c>
2592   <c>standard</c>
2593   <c>
2594      <xref target="header.from"/>
2595   </c>
2596   <c>Location</c>
2597   <c>http</c>
2598   <c>standard</c>
2599   <c>
2600      <xref target="header.location"/>
2601   </c>
2602   <c>Max-Forwards</c>
2603   <c>http</c>
2604   <c>standard</c>
2605   <c>
2606      <xref target="header.max-forwards"/>
2607   </c>
2608   <c>Referer</c>
2609   <c>http</c>
2610   <c>standard</c>
2611   <c>
2612      <xref target="header.referer"/>
2613   </c>
2614   <c>Retry-After</c>
2615   <c>http</c>
2616   <c>standard</c>
2617   <c>
2618      <xref target="header.retry-after"/>
2619   </c>
2620   <c>Server</c>
2621   <c>http</c>
2622   <c>standard</c>
2623   <c>
2624      <xref target="header.server"/>
2625   </c>
2626   <c>User-Agent</c>
2627   <c>http</c>
2628   <c>standard</c>
2629   <c>
2630      <xref target="header.user-agent"/>
2631   </c>
2632</texttable>
2633<!--(END)-->
2634
2635<t>
2636   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2637</t>
2638</section>
2639</section>
2640
2641<section title="Security Considerations" anchor="security.considerations">
2642<t>
2643   This section is meant to inform application developers, information
2644   providers, and users of the security limitations in HTTP/1.1 as
2645   described by this document. The discussion does not include
2646   definitive solutions to the problems revealed, though it does make
2647   some suggestions for reducing security risks.
2648</t>
2649
2650<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2651<t>
2652   Like any generic data transfer protocol, HTTP cannot regulate the
2653   content of the data that is transferred, nor is there any a priori
2654   method of determining the sensitivity of any particular piece of
2655   information within the context of any given request. Therefore,
2656   applications SHOULD supply as much control over this information as
2657   possible to the provider of that information. Four header fields are
2658   worth special mention in this context: Server, Via, Referer and From.
2659</t>
2660<t>
2661   Revealing the specific software version of the server might allow the
2662   server machine to become more vulnerable to attacks against software
2663   that is known to contain security holes. Implementors SHOULD make the
2664   Server header field a configurable option.
2665</t>
2666<t>
2667   Proxies which serve as a portal through a network firewall SHOULD
2668   take special precautions regarding the transfer of header information
2669   that identifies the hosts behind the firewall. In particular, they
2670   SHOULD remove, or replace with sanitized versions, any Via fields
2671   generated behind the firewall.
2672</t>
2673<t>
2674   The Referer header field allows reading patterns to be studied and reverse
2675   links drawn. Although it can be very useful, its power can be abused
2676   if user details are not separated from the information contained in
2677   the Referer. Even when the personal information has been removed, the
2678   Referer header field might indicate a private document's URI whose
2679   publication would be inappropriate.
2680</t>
2681<t>
2682   The information sent in the From field might conflict with the user's
2683   privacy interests or their site's security policy, and hence it
2684   SHOULD NOT  be transmitted without the user being able to disable,
2685   enable, and modify the contents of the field. The user MUST be able
2686   to set the contents of this field within a user preference or
2687   application defaults configuration.
2688</t>
2689<t>
2690   We suggest, though do not require, that a convenient toggle interface
2691   be provided for the user to enable or disable the sending of From and
2692   Referer information.
2693</t>
2694<t>
2695   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header fields can sometimes be used to determine
2696   that a specific client or server have a particular security hole which might
2697   be exploited. Unfortunately, this same information is often used for other
2698   valuable purposes for which HTTP currently has no better mechanism.
2699</t>
2700<t>
2701   Furthermore, the User-Agent header field may contain enough entropy to be
2702   used, possibly in conjunction with other material, to uniquely identify the
2703   user.
2704</t>
2705<t>
2706   Some methods, like TRACE (<xref target="TRACE"/>), expose information
2707   that was sent in request header fields within the body of their response.
2708   Clients SHOULD be careful with sensitive information, like Cookies,
2709   Authorization credentials and other header fields that might be used to
2710   collect data from the client.
2711</t> 
2712</section>
2713
2714<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2715<t>
2716   Because the source of a link might be private information or might
2717   reveal an otherwise private information source, it is strongly
2718   recommended that the user be able to select whether or not the
2719   Referer field is sent. For example, a browser client could have a
2720   toggle switch for browsing openly/anonymously, which would
2721   respectively enable/disable the sending of Referer and From
2722   information.
2723</t>
2724<t>
2725   Clients SHOULD NOT include a Referer header field in a (non-secure)
2726   HTTP request if the referring page was transferred with a secure
2727   protocol.
2728</t>
2729<t>
2730   Authors of services SHOULD NOT use GET-based forms for the submission of
2731   sensitive data because that data will be placed in the request-target. Many
2732   existing servers, proxies, and user agents log or display the request-target
2733   in places where it might be visible to third parties. Such services can
2734   use POST-based form submission instead.
2735</t>
2736</section>
2737
2738<section title="Location Headers and Spoofing" anchor="location.spoofing">
2739<t>
2740   If a single server supports multiple organizations that do not trust
2741   one another, then it MUST check the values of Location and Content-Location
2742   header fields in responses that are generated under control of
2743   said organizations to make sure that they do not attempt to
2744   invalidate resources over which they have no authority.
2745</t>
2746</section>
2747
2748</section>
2749
2750<section title="Acknowledgments" anchor="ack">
2751</section>
2752</middle>
2753<back>
2754
2755<references title="Normative References">
2756
2757<reference anchor="Part1">
2758  <front>
2759    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2760    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2761      <organization abbrev="Day Software">Day Software</organization>
2762      <address><email>fielding@gbiv.com</email></address>
2763    </author>
2764    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2765      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2766      <address><email>jg@freedesktop.org</email></address>
2767    </author>
2768    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2769      <organization abbrev="HP">Hewlett-Packard Company</organization>
2770      <address><email>JeffMogul@acm.org</email></address>
2771    </author>
2772    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2773      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2774      <address><email>henrikn@microsoft.com</email></address>
2775    </author>
2776    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2777      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2778      <address><email>LMM@acm.org</email></address>
2779    </author>
2780    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2781      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2782      <address><email>paulle@microsoft.com</email></address>
2783    </author>
2784    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2785      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2786      <address><email>timbl@w3.org</email></address>
2787    </author>
2788    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2789      <organization abbrev="W3C">World Wide Web Consortium</organization>
2790      <address><email>ylafon@w3.org</email></address>
2791    </author>
2792    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2793      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2794      <address><email>julian.reschke@greenbytes.de</email></address>
2795    </author>
2796    <date month="October" year="2010"/>
2797  </front>
2798  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-12"/>
2799 
2800</reference>
2801
2802<reference anchor="Part3">
2803  <front>
2804    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2805    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2806      <organization abbrev="Day Software">Day Software</organization>
2807      <address><email>fielding@gbiv.com</email></address>
2808    </author>
2809    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2810      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2811      <address><email>jg@freedesktop.org</email></address>
2812    </author>
2813    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2814      <organization abbrev="HP">Hewlett-Packard Company</organization>
2815      <address><email>JeffMogul@acm.org</email></address>
2816    </author>
2817    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2818      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2819      <address><email>henrikn@microsoft.com</email></address>
2820    </author>
2821    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2822      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2823      <address><email>LMM@acm.org</email></address>
2824    </author>
2825    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2826      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2827      <address><email>paulle@microsoft.com</email></address>
2828    </author>
2829    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2830      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2831      <address><email>timbl@w3.org</email></address>
2832    </author>
2833    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2834      <organization abbrev="W3C">World Wide Web Consortium</organization>
2835      <address><email>ylafon@w3.org</email></address>
2836    </author>
2837    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2838      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2839      <address><email>julian.reschke@greenbytes.de</email></address>
2840    </author>
2841    <date month="October" year="2010"/>
2842  </front>
2843  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-12"/>
2844 
2845</reference>
2846
2847<reference anchor="Part4">
2848  <front>
2849    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2850    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2851      <organization abbrev="Day Software">Day Software</organization>
2852      <address><email>fielding@gbiv.com</email></address>
2853    </author>
2854    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2855      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2856      <address><email>jg@freedesktop.org</email></address>
2857    </author>
2858    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2859      <organization abbrev="HP">Hewlett-Packard Company</organization>
2860      <address><email>JeffMogul@acm.org</email></address>
2861    </author>
2862    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2863      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2864      <address><email>henrikn@microsoft.com</email></address>
2865    </author>
2866    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2867      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2868      <address><email>LMM@acm.org</email></address>
2869    </author>
2870    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2871      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2872      <address><email>paulle@microsoft.com</email></address>
2873    </author>
2874    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2875      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2876      <address><email>timbl@w3.org</email></address>
2877    </author>
2878    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2879      <organization abbrev="W3C">World Wide Web Consortium</organization>
2880      <address><email>ylafon@w3.org</email></address>
2881    </author>
2882    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2883      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2884      <address><email>julian.reschke@greenbytes.de</email></address>
2885    </author>
2886    <date month="October" year="2010"/>
2887  </front>
2888  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-12"/>
2889 
2890</reference>
2891
2892<reference anchor="Part5">
2893  <front>
2894    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2895    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2896      <organization abbrev="Day Software">Day Software</organization>
2897      <address><email>fielding@gbiv.com</email></address>
2898    </author>
2899    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2900      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2901      <address><email>jg@freedesktop.org</email></address>
2902    </author>
2903    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2904      <organization abbrev="HP">Hewlett-Packard Company</organization>
2905      <address><email>JeffMogul@acm.org</email></address>
2906    </author>
2907    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2908      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2909      <address><email>henrikn@microsoft.com</email></address>
2910    </author>
2911    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2912      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2913      <address><email>LMM@acm.org</email></address>
2914    </author>
2915    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2916      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2917      <address><email>paulle@microsoft.com</email></address>
2918    </author>
2919    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2920      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2921      <address><email>timbl@w3.org</email></address>
2922    </author>
2923    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2924      <organization abbrev="W3C">World Wide Web Consortium</organization>
2925      <address><email>ylafon@w3.org</email></address>
2926    </author>
2927    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2928      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2929      <address><email>julian.reschke@greenbytes.de</email></address>
2930    </author>
2931    <date month="October" year="2010"/>
2932  </front>
2933  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-12"/>
2934 
2935</reference>
2936
2937<reference anchor="Part6">
2938  <front>
2939    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2940    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2941      <organization abbrev="Day Software">Day Software</organization>
2942      <address><email>fielding@gbiv.com</email></address>
2943    </author>
2944    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2945      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2946      <address><email>jg@freedesktop.org</email></address>
2947    </author>
2948    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2949      <organization abbrev="HP">Hewlett-Packard Company</organization>
2950      <address><email>JeffMogul@acm.org</email></address>
2951    </author>
2952    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2953      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2954      <address><email>henrikn@microsoft.com</email></address>
2955    </author>
2956    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2957      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2958      <address><email>LMM@acm.org</email></address>
2959    </author>
2960    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2961      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2962      <address><email>paulle@microsoft.com</email></address>
2963    </author>
2964    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2965      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2966      <address><email>timbl@w3.org</email></address>
2967    </author>
2968    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2969      <organization abbrev="W3C">World Wide Web Consortium</organization>
2970      <address><email>ylafon@w3.org</email></address>
2971    </author>
2972    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
2973      <address><email>mnot@mnot.net</email></address>
2974    </author>
2975    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2976      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2977      <address><email>julian.reschke@greenbytes.de</email></address>
2978    </author>
2979    <date month="October" year="2010"/>
2980  </front>
2981  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-12"/>
2982 
2983</reference>
2984
2985<reference anchor="Part7">
2986  <front>
2987    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2988    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2989      <organization abbrev="Day Software">Day Software</organization>
2990      <address><email>fielding@gbiv.com</email></address>
2991    </author>
2992    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2993      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2994      <address><email>jg@freedesktop.org</email></address>
2995    </author>
2996    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2997      <organization abbrev="HP">Hewlett-Packard Company</organization>
2998      <address><email>JeffMogul@acm.org</email></address>
2999    </author>
3000    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3001      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3002      <address><email>henrikn@microsoft.com</email></address>
3003    </author>
3004    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3005      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
3006      <address><email>LMM@acm.org</email></address>
3007    </author>
3008    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3009      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3010      <address><email>paulle@microsoft.com</email></address>
3011    </author>
3012    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3013      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3014      <address><email>timbl@w3.org</email></address>
3015    </author>
3016    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3017      <organization abbrev="W3C">World Wide Web Consortium</organization>
3018      <address><email>ylafon@w3.org</email></address>
3019    </author>
3020    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3021      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3022      <address><email>julian.reschke@greenbytes.de</email></address>
3023    </author>
3024    <date month="October" year="2010"/>
3025  </front>
3026  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-12"/>
3027 
3028</reference>
3029
3030<reference anchor="RFC2119">
3031  <front>
3032    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3033    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3034      <organization>Harvard University</organization>
3035      <address><email>sob@harvard.edu</email></address>
3036    </author>
3037    <date month="March" year="1997"/>
3038  </front>
3039  <seriesInfo name="BCP" value="14"/>
3040  <seriesInfo name="RFC" value="2119"/>
3041</reference>
3042
3043<reference anchor="RFC3986">
3044 <front>
3045  <title abbrev="URI Generic Syntax">Uniform Resource Identifier (URI): Generic Syntax</title>
3046  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3047    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3048    <address>
3049       <email>timbl@w3.org</email>
3050       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3051    </address>
3052  </author>
3053  <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3054    <organization abbrev="Day Software">Day Software</organization>
3055    <address>
3056      <email>fielding@gbiv.com</email>
3057      <uri>http://roy.gbiv.com/</uri>
3058    </address>
3059  </author>
3060  <author initials="L." surname="Masinter" fullname="Larry Masinter">
3061    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3062    <address>
3063      <email>LMM@acm.org</email>
3064      <uri>http://larry.masinter.net/</uri>
3065    </address>
3066  </author>
3067  <date month="January" year="2005"/>
3068 </front>
3069 <seriesInfo name="STD" value="66"/>
3070 <seriesInfo name="RFC" value="3986"/>
3071</reference>
3072
3073<reference anchor="RFC5234">
3074  <front>
3075    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3076    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3077      <organization>Brandenburg InternetWorking</organization>
3078      <address>
3079        <email>dcrocker@bbiw.net</email>
3080      </address> 
3081    </author>
3082    <author initials="P." surname="Overell" fullname="Paul Overell">
3083      <organization>THUS plc.</organization>
3084      <address>
3085        <email>paul.overell@thus.net</email>
3086      </address>
3087    </author>
3088    <date month="January" year="2008"/>
3089  </front>
3090  <seriesInfo name="STD" value="68"/>
3091  <seriesInfo name="RFC" value="5234"/>
3092</reference>
3093
3094</references>
3095
3096<references title="Informative References">
3097
3098<reference anchor="RFC1945">
3099  <front>
3100    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3101    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3102      <organization>MIT, Laboratory for Computer Science</organization>
3103      <address><email>timbl@w3.org</email></address>
3104    </author>
3105    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3106      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3107      <address><email>fielding@ics.uci.edu</email></address>
3108    </author>
3109    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3110      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3111      <address><email>frystyk@w3.org</email></address>
3112    </author>
3113    <date month="May" year="1996"/>
3114  </front>
3115  <seriesInfo name="RFC" value="1945"/>
3116</reference>
3117
3118<reference anchor="RFC2068">
3119  <front>
3120    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3121    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3122      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3123      <address><email>fielding@ics.uci.edu</email></address>
3124    </author>
3125    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3126      <organization>MIT Laboratory for Computer Science</organization>
3127      <address><email>jg@w3.org</email></address>
3128    </author>
3129    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3130      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3131      <address><email>mogul@wrl.dec.com</email></address>
3132    </author>
3133    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3134      <organization>MIT Laboratory for Computer Science</organization>
3135      <address><email>frystyk@w3.org</email></address>
3136    </author>
3137    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3138      <organization>MIT Laboratory for Computer Science</organization>
3139      <address><email>timbl@w3.org</email></address>
3140    </author>
3141    <date month="January" year="1997"/>
3142  </front>
3143  <seriesInfo name="RFC" value="2068"/>
3144</reference>
3145
3146<reference anchor="RFC2616">
3147  <front>
3148    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3149    <author initials="R." surname="Fielding" fullname="R. Fielding">
3150      <organization>University of California, Irvine</organization>
3151      <address><email>fielding@ics.uci.edu</email></address>
3152    </author>
3153    <author initials="J." surname="Gettys" fullname="J. Gettys">
3154      <organization>W3C</organization>
3155      <address><email>jg@w3.org</email></address>
3156    </author>
3157    <author initials="J." surname="Mogul" fullname="J. Mogul">
3158      <organization>Compaq Computer Corporation</organization>
3159      <address><email>mogul@wrl.dec.com</email></address>
3160    </author>
3161    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3162      <organization>MIT Laboratory for Computer Science</organization>
3163      <address><email>frystyk@w3.org</email></address>
3164    </author>
3165    <author initials="L." surname="Masinter" fullname="L. Masinter">
3166      <organization>Xerox Corporation</organization>
3167      <address><email>masinter@parc.xerox.com</email></address>
3168    </author>
3169    <author initials="P." surname="Leach" fullname="P. Leach">
3170      <organization>Microsoft Corporation</organization>
3171      <address><email>paulle@microsoft.com</email></address>
3172    </author>
3173    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3174      <organization>W3C</organization>
3175      <address><email>timbl@w3.org</email></address>
3176    </author>
3177    <date month="June" year="1999"/>
3178  </front>
3179  <seriesInfo name="RFC" value="2616"/>
3180</reference>
3181
3182<reference anchor="RFC2817">
3183  <front>
3184    <title>Upgrading to TLS Within HTTP/1.1</title>
3185    <author initials="R." surname="Khare" fullname="R. Khare">
3186      <organization>4K Associates / UC Irvine</organization>
3187      <address><email>rohit@4K-associates.com</email></address>
3188    </author>
3189    <author initials="S." surname="Lawrence" fullname="S. Lawrence">
3190      <organization>Agranat Systems, Inc.</organization>
3191      <address><email>lawrence@agranat.com</email></address>
3192    </author>
3193    <date year="2000" month="May"/>
3194  </front>
3195  <seriesInfo name="RFC" value="2817"/>
3196</reference>
3197
3198<reference anchor="RFC3864">
3199  <front>
3200    <title>Registration Procedures for Message Header Fields</title>
3201    <author initials="G." surname="Klyne" fullname="G. Klyne">
3202      <organization>Nine by Nine</organization>
3203      <address><email>GK-IETF@ninebynine.org</email></address>
3204    </author>
3205    <author initials="M." surname="Nottingham" fullname="M. Nottingham">
3206      <organization>BEA Systems</organization>
3207      <address><email>mnot@pobox.com</email></address>
3208    </author>
3209    <author initials="J." surname="Mogul" fullname="J. Mogul">
3210      <organization>HP Labs</organization>
3211      <address><email>JeffMogul@acm.org</email></address>
3212    </author>
3213    <date year="2004" month="September"/>
3214  </front>
3215  <seriesInfo name="BCP" value="90"/>
3216  <seriesInfo name="RFC" value="3864"/>
3217</reference>
3218
3219<reference anchor="RFC5226">
3220  <front>
3221    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3222    <author initials="T." surname="Narten" fullname="T. Narten">
3223      <organization>IBM</organization>
3224      <address><email>narten@us.ibm.com</email></address>
3225    </author>
3226    <author initials="H." surname="Alvestrand" fullname="H. Alvestrand">
3227      <organization>Google</organization>
3228      <address><email>Harald@Alvestrand.no</email></address>
3229    </author>
3230    <date year="2008" month="May"/>
3231  </front>
3232  <seriesInfo name="BCP" value="26"/>
3233  <seriesInfo name="RFC" value="5226"/>
3234</reference>
3235
3236<reference anchor="RFC5322">
3237  <front>
3238    <title>Internet Message Format</title>
3239    <author initials="P." surname="Resnick" fullname="P. Resnick">
3240      <organization>Qualcomm Incorporated</organization>
3241    </author>
3242    <date year="2008" month="October"/>
3243  </front> 
3244  <seriesInfo name="RFC" value="5322"/>
3245</reference>
3246
3247</references>
3248
3249<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3250<t>
3251  This document takes over the Status Code Registry, previously defined
3252  in Section 7.1 of <xref target="RFC2817"/>.
3253  (<xref target="status.code.registry"/>)
3254</t>
3255<t>
3256  Clarify definition of POST.
3257  (<xref target="POST"/>)
3258</t>
3259<t>
3260  Failed to consider that there are
3261  many other request methods that are safe to automatically redirect,
3262  and further that the user agent is able to make that determination
3263  based on the request method semantics.
3264  (Sections <xref format="counter" target="status.301"/>,
3265  <xref format="counter" target="status.302"/> and
3266  <xref format="counter" target="status.307"/>)
3267</t>
3268<t>
3269  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3270  It used to indicate that the target resource must be accessed through the
3271  proxy given by the Location field. The Location field gave the URI of the
3272  proxy. The recipient was expected to repeat this single request via the proxy.
3273  (<xref target="status.305"/>)
3274</t>
3275<t>
3276  Reclassify "Allow" as response header field, removing the option to
3277  specify it in a PUT request.
3278  Relax the server requirement on the contents of the Allow header field and
3279  remove requirement on clients to always trust the header field value.
3280  (<xref target="header.allow"/>)
3281</t>
3282<t>
3283  Correct syntax of Location header field to allow URI references (including
3284  relative references and fragments), as referred symbol "absoluteURI" wasn't
3285  what was expected, and add some clarifications as to when use of fragments
3286  would not be appropriate.
3287  (<xref target="header.location"/>)
3288</t>
3289<t>
3290  Allow Referer field value of "about:blank" as alternative to not specifying it.
3291  (<xref target="header.referer"/>)
3292</t>
3293<t>
3294  In the description of the Server header field, the Via field
3295  was described as a SHOULD. The requirement was and is stated
3296  correctly in the description of the Via header field in Section 9.9 of <xref target="Part1"/>.
3297  (<xref target="header.server"/>)
3298</t>
3299</section>
3300
3301
3302<section title="Collected ABNF" anchor="collected.abnf">
3303<figure>
3304<artwork type="abnf" name="p2-semantics.parsed-abnf"><![CDATA[
3305Accept = <Accept, defined in [Part3], Section 6.1>
3306Accept-Charset = <Accept-Charset, defined in [Part3], Section 6.2>
3307Accept-Encoding = <Accept-Encoding, defined in [Part3], Section 6.3>
3308Accept-Language = <Accept-Language, defined in [Part3], Section 6.4>
3309Accept-Ranges = <Accept-Ranges, defined in [Part5], Section 5.1>
3310Age = <Age, defined in [Part6], Section 3.1>
3311Allow = "Allow:" OWS Allow-v
3312Allow-v = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3313Authorization = <Authorization, defined in [Part7], Section 4.1>
3314
3315ETag = <ETag, defined in [Part4], Section 6.1>
3316Expect = "Expect:" OWS Expect-v
3317Expect-v = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3318
3319From = "From:" OWS From-v
3320From-v = mailbox
3321
3322HTTP-date = <HTTP-date, defined in [Part1], Section 6.1>
3323Host = <Host, defined in [Part1], Section 2.6>
3324
3325If-Match = <If-Match, defined in [Part4], Section 6.2>
3326If-Modified-Since =
3327 <If-Modified-Since, defined in [Part4], Section 6.3>
3328If-None-Match = <If-None-Match, defined in [Part4], Section 6.4>
3329If-Range = <If-Range, defined in [Part5], Section 5.3>
3330If-Unmodified-Since =
3331 <If-Unmodified-Since, defined in [Part4], Section 6.5>
3332
3333Location = "Location:" OWS Location-v
3334Location-v = URI-reference
3335
3336Max-Forwards = "Max-Forwards:" OWS Max-Forwards-v
3337Max-Forwards-v = 1*DIGIT
3338Method = %x4F.50.54.49.4F.4E.53 ; OPTIONS
3339 / %x47.45.54 ; GET
3340 / %x48.45.41.44 ; HEAD
3341 / %x50.4F.53.54 ; POST
3342 / %x50.55.54 ; PUT
3343 / %x44.45.4C.45.54.45 ; DELETE
3344 / %x54.52.41.43.45 ; TRACE
3345 / %x43.4F.4E.4E.45.43.54 ; CONNECT
3346 / extension-method
3347
3348OWS = <OWS, defined in [Part1], Section 1.2.2>
3349
3350Proxy-Authenticate =
3351 <Proxy-Authenticate, defined in [Part7], Section 4.2>
3352Proxy-Authorization =
3353 <Proxy-Authorization, defined in [Part7], Section 4.3>
3354
3355RWS = <RWS, defined in [Part1], Section 1.2.2>
3356Range = <Range, defined in [Part5], Section 5.4>
3357Reason-Phrase = *( WSP / VCHAR / obs-text )
3358Referer = "Referer:" OWS Referer-v
3359Referer-v = absolute-URI / partial-URI
3360Retry-After = "Retry-After:" OWS Retry-After-v
3361Retry-After-v = HTTP-date / delta-seconds
3362
3363Server = "Server:" OWS Server-v
3364Server-v = product *( RWS ( product / comment ) )
3365Status-Code = "100" / "101" / "200" / "201" / "202" / "203" / "204" /
3366 "205" / "206" / "300" / "301" / "302" / "303" / "304" / "305" /
3367 "307" / "400" / "401" / "402" / "403" / "404" / "405" / "406" /
3368 "407" / "408" / "409" / "410" / "411" / "412" / "413" / "414" /
3369 "415" / "416" / "417" / "500" / "501" / "502" / "503" / "504" /
3370 "505" / extension-code
3371
3372TE = <TE, defined in [Part1], Section 9.5>
3373
3374URI-reference = <URI-reference, defined in [Part1], Section 2.6>
3375User-Agent = "User-Agent:" OWS User-Agent-v
3376User-Agent-v = product *( RWS ( product / comment ) )
3377
3378Vary = <Vary, defined in [Part6], Section 3.5>
3379
3380WWW-Authenticate =
3381 <WWW-Authenticate, defined in [Part7], Section 4.4>
3382
3383absolute-URI = <absolute-URI, defined in [Part1], Section 2.6>
3384
3385comment = <comment, defined in [Part1], Section 3.2>
3386
3387delta-seconds = 1*DIGIT
3388
3389expect-params = ";" token [ "=" ( token / quoted-string ) ]
3390expectation = "100-continue" / expectation-extension
3391expectation-extension = token [ "=" ( token / quoted-string )
3392 *expect-params ]
3393extension-code = 3DIGIT
3394extension-method = token
3395
3396mailbox = <mailbox, defined in [RFC5322], Section 3.4>
3397
3398obs-text = <obs-text, defined in [Part1], Section 1.2.2>
3399
3400partial-URI = <partial-URI, defined in [Part1], Section 2.6>
3401product = <product, defined in [Part1], Section 6.3>
3402
3403quoted-string = <quoted-string, defined in [Part1], Section 1.2.2>
3404
3405request-header = Accept / Accept-Charset / Accept-Encoding /
3406 Accept-Language / Authorization / Expect / From / Host / If-Match /
3407 If-Modified-Since / If-None-Match / If-Range / If-Unmodified-Since /
3408 Max-Forwards / Proxy-Authorization / Range / Referer / TE /
3409 User-Agent
3410response-header = Accept-Ranges / Age / Allow / ETag / Location /
3411 Proxy-Authenticate / Retry-After / Server / Vary / WWW-Authenticate
3412
3413token = <token, defined in [Part1], Section 1.2.2>
3414]]></artwork>
3415</figure>
3416<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline"><![CDATA[
3417; Reason-Phrase defined but not used
3418; Status-Code defined but not used
3419; request-header defined but not used
3420; response-header defined but not used
3421]]></artwork></figure></section>
3422
3423
3424<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3425
3426<section title="Since RFC 2616">
3427<t>
3428  Extracted relevant partitions from <xref target="RFC2616"/>.
3429</t>
3430</section>
3431
3432<section title="Since draft-ietf-httpbis-p2-semantics-00">
3433<t>
3434  Closed issues:
3435  <list style="symbols"> 
3436    <t>
3437      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3438      "Via is a MUST"
3439      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3440    </t>
3441    <t>
3442      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3443      "Fragments allowed in Location"
3444      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3445    </t>
3446    <t>
3447      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3448      "Safe Methods vs Redirection"
3449      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3450    </t>
3451    <t>
3452      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3453      "Revise description of the POST method"
3454      (<eref target="http://purl.org/NET/http-errata#post"/>)
3455    </t>
3456    <t>
3457      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3458      "Normative and Informative references"
3459    </t>
3460    <t>
3461      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3462      "RFC2606 Compliance"
3463    </t>
3464    <t>
3465      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3466      "Informative references"
3467    </t>
3468    <t>
3469      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3470      "Redundant cross-references"
3471    </t>
3472  </list>
3473</t>
3474<t>
3475  Other changes:
3476  <list style="symbols"> 
3477    <t>
3478      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3479    </t>
3480  </list>
3481</t>
3482</section>
3483
3484<section title="Since draft-ietf-httpbis-p2-semantics-01">
3485<t>
3486  Closed issues:
3487  <list style="symbols"> 
3488    <t>
3489      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3490      "PUT side effects"
3491    </t>
3492    <t>
3493      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3494      "Duplicate Host header requirements"
3495    </t>
3496  </list>
3497</t>
3498<t>
3499  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3500  <list style="symbols"> 
3501    <t>
3502      Move "Product Tokens" section (back) into Part 1, as "token" is used
3503      in the definition of the Upgrade header field.
3504    </t>
3505    <t>
3506      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3507    </t>
3508    <t>
3509      Copy definition of delta-seconds from Part6 instead of referencing it.
3510    </t>
3511  </list>
3512</t>
3513</section>
3514
3515<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3516<t>
3517  Closed issues:
3518  <list style="symbols"> 
3519    <t>
3520      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3521      "Requiring Allow in 405 responses"
3522    </t>
3523    <t>
3524      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3525      "Status Code Registry"
3526    </t>
3527    <t>
3528      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3529      "Redirection vs. Location"
3530    </t>
3531    <t>
3532      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3533      "Cacheability of 303 response"
3534    </t>
3535    <t>
3536      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3537      "305 Use Proxy"
3538    </t>
3539    <t>
3540      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3541      "Classification for Allow header"
3542    </t>
3543    <t>
3544      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3545      "PUT - 'store under' vs 'store at'"
3546    </t>
3547  </list>
3548</t>
3549<t>
3550  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3551  <list style="symbols"> 
3552    <t>
3553      Reference RFC 3984, and update header field registrations for headers defined
3554      in this document.
3555    </t>
3556  </list>
3557</t>
3558<t>
3559  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3560  <list style="symbols"> 
3561    <t>
3562      Replace string literals when the string really is case-sensitive (method).
3563    </t>
3564  </list>
3565</t>
3566</section>
3567
3568<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3569<t>
3570  Closed issues:
3571  <list style="symbols"> 
3572    <t>
3573      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
3574      "OPTIONS request bodies"
3575    </t>
3576    <t>
3577      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
3578      "Description of CONNECT should refer to RFC2817"
3579    </t>
3580    <t>
3581      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
3582      "Location Content-Location reference request/response mixup"
3583    </t>
3584  </list>
3585</t>
3586<t>
3587  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
3588  <list style="symbols"> 
3589    <t>
3590      Added initial proposal for registration process, plus initial
3591      content (non-HTTP/1.1 methods to be added by a separate specification).
3592    </t>
3593  </list>
3594</t>
3595</section>
3596
3597<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3598<t>
3599  Closed issues:
3600  <list style="symbols"> 
3601    <t>
3602      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3603      "Content-*"
3604    </t>
3605    <t>
3606      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3607      "RFC 2822 is updated by RFC 5322"
3608    </t>
3609  </list>
3610</t>
3611<t>
3612  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3613  <list style="symbols"> 
3614    <t>
3615      Use "/" instead of "|" for alternatives.
3616    </t>
3617    <t>
3618      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3619      whitespace ("OWS") and required whitespace ("RWS").
3620    </t>
3621    <t>
3622      Rewrite ABNFs to spell out whitespace rules, factor out
3623      header field value format definitions.
3624    </t>
3625  </list>
3626</t>
3627</section>
3628
3629<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3630<t>
3631  Closed issues:
3632  <list style="symbols"> 
3633    <t>
3634      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
3635      "Reason-Phrase BNF"
3636    </t>
3637  </list>
3638</t>
3639<t>
3640  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3641  <list style="symbols"> 
3642    <t>
3643      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3644    </t>
3645  </list>
3646</t>
3647</section>
3648
3649<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
3650<t>
3651  Closed issues:
3652  <list style="symbols"> 
3653    <t>
3654      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
3655      "Clarify when Referer is sent"
3656    </t>
3657    <t>
3658      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
3659      "status codes vs methods"
3660    </t>
3661    <t>
3662      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
3663      "Do not require "updates" relation for specs that register status codes or method names"
3664    </t>
3665  </list>
3666</t>
3667</section>
3668
3669<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
3670<t>
3671  Closed issues:
3672  <list style="symbols"> 
3673    <t>
3674      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
3675      "Idempotency"
3676    </t>
3677    <t>
3678      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
3679      "TRACE security considerations"
3680    </t>
3681    <t>
3682      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
3683      "Clarify rules for determining what entities a response carries"
3684    </t>
3685    <t>
3686      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
3687      "update note citing RFC 1945 and 2068"
3688    </t>
3689    <t>
3690      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
3691      "update note about redirect limit"
3692    </t>
3693    <t>
3694      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
3695      "Location header ABNF should use 'URI'"
3696    </t>
3697    <t>
3698      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
3699      "fragments in Location vs status 303"
3700    </t>
3701    <t>
3702      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
3703      "move IANA registrations for optional status codes"
3704    </t>
3705  </list>
3706</t>
3707<t>
3708  Partly resolved issues:
3709  <list style="symbols"> 
3710    <t>
3711      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
3712      "Are OPTIONS and TRACE safe?"
3713    </t>
3714  </list>
3715</t>
3716</section>
3717
3718<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
3719<t>
3720  Closed issues:
3721  <list style="symbols"> 
3722    <t>
3723      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3724      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
3725      status codes when fixing this previously)
3726    </t>
3727  </list>
3728</t>
3729</section>
3730
3731<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
3732<t>
3733  Closed issues:
3734  <list style="symbols"> 
3735    <t>
3736      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
3737      "Fragment combination / precedence during redirects"
3738    </t>
3739  </list>
3740</t>
3741<t>
3742  Partly resolved issues:
3743  <list style="symbols"> 
3744    <t>
3745      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
3746      "Location header payload handling"
3747    </t>
3748    <t>
3749      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
3750      "Term for the requested resource's URI"
3751    </t>
3752  </list>
3753</t>
3754</section>
3755
3756<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
3757<t>
3758  Closed issues:
3759  <list style="symbols"> 
3760    <t>
3761      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
3762      "Clarify 'Requested Variant'"
3763    </t>
3764    <t>
3765      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
3766      "Clarify entity / representation / variant terminology"
3767    </t>
3768    <t>
3769      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/139"/>:
3770      "Methods and Caching"
3771    </t>
3772    <t>
3773      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/190"/>:
3774      "OPTIONS vs Max-Forwards"
3775    </t>
3776    <t>
3777      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/199"/>:
3778      "Status codes and caching"
3779    </t>
3780    <t>
3781      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
3782      "consider removing the 'changes from 2068' sections"
3783    </t>
3784  </list>
3785</t>
3786</section>
3787
3788<section title="Since draft-ietf-httpbis-p2-semantics-11" anchor="changes.since.11">
3789<t>
3790  Closed issues:
3791  <list style="symbols"> 
3792    <t>
3793      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/229"/>:
3794      "Considerations for new status codes"
3795    </t>
3796    <t>
3797      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/230"/>:
3798      "Considerations for new methods"
3799    </t>
3800    <t>
3801      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/232"/>:
3802      "User-Agent guidelines" (relating to the 'User-Agent' header field)
3803    </t>
3804  </list>
3805</t>
3806</section>
3807
3808</section>
3809
3810</back>
3811</rfc>
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