source: draft-ietf-httpbis/03/draft-ietf-httpbis-p2-semantics-03.xml @ 653

Last change on this file since 653 was 559, checked in by fielding@…, 11 years ago

remove executable and set eol-style for earlier drafts

  • Property svn:eol-style set to native
File size: 125.1 KB
Line 
1<?xml version="1.0" encoding="UTF-8"?>
2<!--
3    This XML document is the output of clean-for-DTD.xslt; a tool that strips
4    extensions to RFC2629(bis) from documents for processing with xml2rfc.
5-->
6<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
7<?rfc toc="yes" ?>
8<?rfc symrefs="yes" ?>
9<?rfc sortrefs="yes" ?>
10<?rfc compact="yes"?>
11<?rfc subcompact="no" ?>
12<?rfc linkmailto="no" ?>
13<?rfc editing="no" ?>
14<?rfc comments="yes"?>
15<?rfc inline="yes"?>
16<!DOCTYPE rfc
17  PUBLIC "" "rfc2629.dtd">
18<rfc obsoletes="2616" updates="2817" category="std" ipr="full3978" docName="draft-ietf-httpbis-p2-semantics-03">
19<front>
20
21  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
22
23  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
24    <organization abbrev="Day Software">Day Software</organization>
25    <address>
26      <postal>
27        <street>23 Corporate Plaza DR, Suite 280</street>
28        <city>Newport Beach</city>
29        <region>CA</region>
30        <code>92660</code>
31        <country>USA</country>
32      </postal>
33      <phone>+1-949-706-5300</phone>
34      <facsimile>+1-949-706-5305</facsimile>
35      <email>fielding@gbiv.com</email>
36      <uri>http://roy.gbiv.com/</uri>
37    </address>
38  </author>
39
40  <author initials="J." surname="Gettys" fullname="Jim Gettys">
41    <organization>One Laptop per Child</organization>
42    <address>
43      <postal>
44        <street>21 Oak Knoll Road</street>
45        <city>Carlisle</city>
46        <region>MA</region>
47        <code>01741</code>
48        <country>USA</country>
49      </postal>
50      <email>jg@laptop.org</email>
51      <uri>http://www.laptop.org/</uri>
52    </address>
53  </author>
54 
55  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
56    <organization abbrev="HP">Hewlett-Packard Company</organization>
57    <address>
58      <postal>
59        <street>HP Labs, Large Scale Systems Group</street>
60        <street>1501 Page Mill Road, MS 1177</street>
61        <city>Palo Alto</city>
62        <region>CA</region>
63        <code>94304</code>
64        <country>USA</country>
65      </postal>
66      <email>JeffMogul@acm.org</email>
67    </address>
68  </author>
69
70  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
71    <organization abbrev="Microsoft">Microsoft Corporation</organization>
72    <address>
73      <postal>
74        <street>1 Microsoft Way</street>
75        <city>Redmond</city>
76        <region>WA</region>
77        <code>98052</code>
78        <country>USA</country>
79      </postal>
80      <email>henrikn@microsoft.com</email>
81    </address>
82  </author>
83
84  <author initials="L." surname="Masinter" fullname="Larry Masinter">
85    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
86    <address>
87      <postal>
88        <street>345 Park Ave</street>
89        <city>San Jose</city>
90        <region>CA</region>
91        <code>95110</code>
92        <country>USA</country>
93      </postal>
94      <email>LMM@acm.org</email>
95      <uri>http://larry.masinter.net/</uri>
96    </address>
97  </author>
98 
99  <author initials="P." surname="Leach" fullname="Paul J. Leach">
100    <organization abbrev="Microsoft">Microsoft Corporation</organization>
101    <address>
102      <postal>
103        <street>1 Microsoft Way</street>
104        <city>Redmond</city>
105        <region>WA</region>
106        <code>98052</code>
107      </postal>
108      <email>paulle@microsoft.com</email>
109    </address>
110  </author>
111   
112  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
113    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
114    <address>
115      <postal>
116        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
117        <street>The Stata Center, Building 32</street>
118        <street>32 Vassar Street</street>
119        <city>Cambridge</city>
120        <region>MA</region>
121        <code>02139</code>
122        <country>USA</country>
123      </postal>
124      <email>timbl@w3.org</email>
125      <uri>http://www.w3.org/People/Berners-Lee/</uri>
126    </address>
127  </author>
128
129  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
130    <organization abbrev="W3C">World Wide Web Consortium</organization>
131    <address>
132      <postal>
133        <street>W3C / ERCIM</street>
134        <street>2004, rte des Lucioles</street>
135        <city>Sophia-Antipolis</city>
136        <region>AM</region>
137        <code>06902</code>
138        <country>France</country>
139      </postal>
140      <email>ylafon@w3.org</email>
141      <uri>http://www.raubacapeu.net/people/yves/</uri>
142    </address>
143  </author>
144
145  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
146    <organization abbrev="greenbytes">greenbytes GmbH</organization>
147    <address>
148      <postal>
149        <street>Hafenweg 16</street>
150        <city>Muenster</city><region>NW</region><code>48155</code>
151        <country>Germany</country>
152      </postal>
153      <phone>+49 251 2807760</phone>   
154      <facsimile>+49 251 2807761</facsimile>   
155      <email>julian.reschke@greenbytes.de</email>       
156      <uri>http://greenbytes.de/tech/webdav/</uri>     
157    </address>
158  </author>
159
160  <date month="June" year="2008" day="17"/>
161
162<abstract>
163<t>
164   The Hypertext Transfer Protocol (HTTP) is an application-level
165   protocol for distributed, collaborative, hypermedia information
166   systems. HTTP has been in use by the World Wide Web global information
167   initiative since 1990. This document is Part 2 of the seven-part specification
168   that defines the protocol referred to as "HTTP/1.1" and, taken together,
169   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
170   as expressed by request methods, request-header fields, response status codes,
171   and response-header fields.
172</t>
173</abstract>
174
175<note title="Editorial Note (To be removed by RFC Editor)">
176  <t>
177    Discussion of this draft should take place on the HTTPBIS working group
178    mailing list (ietf-http-wg@w3.org). The current issues list is
179    at <eref target="http://www.tools.ietf.org/wg/httpbis/trac/report/11"/>
180    and related documents (including fancy diffs) can be found at
181    <eref target="http://www.tools.ietf.org/wg/httpbis/"/>.
182  </t>
183  <t>
184    The changes in this draft are summarized in <xref target="changes.since.02"/>.
185  </t>
186</note>
187</front>
188<middle>
189<section title="Introduction" anchor="introduction">
190<t>
191   This document defines HTTP/1.1 request and response semantics.  Each HTTP
192   message, as defined in <xref target="Part1"/>, is in the form of either a request or
193   a response.  An HTTP server listens on a connection for HTTP requests and
194   responds to each request, in the order received on that connection, with
195   one or more HTTP response messages.  This document defines the commonly
196   agreed upon semantics of the HTTP uniform interface, the intentions defined
197   by each request method, and the various response messages that might be
198   expected as a result of applying that method for the requested resource.
199</t>
200<t>
201   This document is currently disorganized in order to minimize the changes
202   between drafts and enable reviewers to see the smaller errata changes.
203   The next draft will reorganize the sections to better reflect the content.
204   In particular, the sections will be ordered according to the typical
205   processing of an HTTP request message (after message parsing): resource
206   mapping, general header fields, methods, request modifiers, response
207   status, and resource metadata.  The current mess reflects how widely
208   dispersed these topics and associated requirements had become in
209   <xref target="RFC2616"/>.
210</t>
211
212<section title="Requirements" anchor="intro.requirements">
213<t>
214   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
215   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
216   document are to be interpreted as described in <xref target="RFC2119"/>.
217</t>
218<t>
219   An implementation is not compliant if it fails to satisfy one or more
220   of the MUST or REQUIRED level requirements for the protocols it
221   implements. An implementation that satisfies all the MUST or REQUIRED
222   level and all the SHOULD level requirements for its protocols is said
223   to be "unconditionally compliant"; one that satisfies all the MUST
224   level requirements but not all the SHOULD level requirements for its
225   protocols is said to be "conditionally compliant."
226</t>
227</section>
228</section>
229
230<section title="Notational Conventions and Generic Grammar" anchor="notation">
231 
232 
233 
234 
235<t>
236  This specification uses the ABNF syntax defined in Section 2.1 of <xref target="Part1"/> and
237  the core rules defined in Section 2.2 of <xref target="Part1"/>:
238  <cref anchor="abnf.dep">ABNF syntax and basic rules will be adopted from RFC 5234, see
239  &lt;http://tools.ietf.org/wg/httpbis/trac/ticket/36&gt;.</cref>
240</t>
241<figure><artwork type="abnf2616"><![CDATA[
242  DIGIT         = <DIGIT, defined in [Part1], Section 2.2>
243]]></artwork></figure>
244<figure><artwork type="abnf2616"><![CDATA[
245 
246  comment       = <comment, defined in [Part1], Section 2.2>
247  quoted-string = <quoted-string, defined in [Part1], Section 2.2>
248  token         = <token, defined in [Part1], Section 2.2>
249]]></artwork></figure>
250<t anchor="abnf.dependencies">
251 
252 
253 
254 
255 
256 
257 
258 
259 
260 
261 
262 
263 
264 
265 
266 
267 
268 
269 
270 
271 
272 
273 
274 
275 
276  The ABNF rules below are defined in other parts:
277</t>
278<figure><!--Part1--><artwork type="abnf2616"><![CDATA[
279  absoluteURI   = <absoluteURI, defined in [Part1], Section 3.2.1>
280  fragment      = <fragment, defined in [Part1], Section 3.2.1>
281  Host          = <Host, defined in [Part1], Section 8.4>
282  HTTP-date     = <HTTP-date, defined in [Part1], Section 3.3.1>
283  product       = <product, defined in [Part1], Section 3.5>
284  relativeURI   = <relativeURI, defined in [Part1], Section 3.2.1>
285  TE            = <TE, defined in [Part1], Section 8.8>
286]]></artwork></figure>
287<figure><!--Part3--><artwork type="abnf2616"><![CDATA[
288  Accept        = <Accept, defined in [Part3], Section 6.1>
289  Accept-Charset =
290             <Accept-Charset, defined in [Part3], Section 6.2>
291  Accept-Encoding =
292             <Accept-Encoding, defined in [Part3], Section 6.3>
293  Accept-Language =
294             <Accept-Language, defined in [Part3], Section 6.4>
295]]></artwork></figure>
296<figure><!--Part4--><artwork type="abnf2616"><![CDATA[
297  ETag          = <ETag, defined in [Part4], Section 7.1>
298  If-Match      = <If-Match, defined in [Part4], Section 7.2>
299  If-Modified-Since =
300             <If-Modified-Since, defined in [Part4], Section 7.3>
301  If-None-Match = <If-None-Match, defined in [Part4], Section 7.4>
302  If-Unmodified-Since =
303             <If-Unmodified-Since, defined in [Part4], Section 7.5>
304]]></artwork></figure>
305<figure><!--Part5--><artwork type="abnf2616"><![CDATA[
306  Accept-Ranges = <Accept-Ranges, defined in [Part5], Section 6.1>
307  If-Range      = <If-Range, defined in [Part5], Section 6.3>
308  Range         = <Range, defined in [Part5], Section 6.4>
309]]></artwork></figure>
310<figure><!--Part6--><artwork type="abnf2616"><![CDATA[
311  Age           = <Age, defined in [Part6], Section 16.1>
312  Vary          = <Vary, defined in [Part6], Section 16.5>
313]]></artwork><!--Part7--></figure>
314<figure><artwork type="abnf2616"><![CDATA[
315  Authorization = <Authorization, defined in [Part7], Section 4.1>
316  Proxy-Authenticate =
317             <Proxy-Authenticate, defined in [Part7], Section 4.2>
318  Proxy-Authorization =
319             <Proxy-Authorization, defined in [Part7], Section 4.3>
320  WWW-Authenticate =
321             <WWW-Authenticate, defined in [Part7], Section 4.4>
322]]></artwork></figure>
323</section>
324
325<section title="Method" anchor="method">
326 
327 
328<t>
329   The Method  token indicates the method to be performed on the
330   resource identified by the Request-URI. The method is case-sensitive.
331</t>
332<figure><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/><artwork type="abnf2616"><![CDATA[
333  Method         = %x4F.50.54.49.4F.4E.53   ; "OPTIONS", Section 8.2
334                 | %x47.45.54               ; "GET", Section 8.3
335                 | %x48.45.41.44            ; "HEAD", Section 8.4
336                 | %x50.4F.53.54            ; "POST", Section 8.5
337                 | %x50.55.54               ; "PUT", Section 8.6
338                 | %x44.45.4C.45.54.45      ; "DELETE", Section 8.7
339                 | %x54.52.41.43.45         ; "TRACE", Section 8.8
340                 | %x43.4F.4E.4E.45.43.54   ; "CONNECT", Section 8.9
341                 | extension-method
342  extension-method = token
343]]></artwork></figure>
344<t>
345   The list of methods allowed by a resource can be specified in an
346   Allow header field (<xref target="header.allow"/>). The return code of the response
347   always notifies the client whether a method is currently allowed on a
348   resource, since the set of allowed methods can change dynamically. An
349   origin server SHOULD return the status code 405 (Method Not Allowed)
350   if the method is known by the origin server but not allowed for the
351   requested resource, and 501 (Not Implemented) if the method is
352   unrecognized or not implemented by the origin server. The methods GET
353   and HEAD MUST be supported by all general-purpose servers. All other
354   methods are OPTIONAL; however, if the above methods are implemented,
355   they MUST be implemented with the same semantics as those specified
356   in <xref target="method.definitions"/>.
357</t>
358</section>
359
360<section title="Request Header Fields" anchor="request.header.fields">
361 
362 
363<t>
364   The request-header fields allow the client to pass additional
365   information about the request, and about the client itself, to the
366   server. These fields act as request modifiers, with semantics
367   equivalent to the parameters on a programming language method
368   invocation.
369</t>
370<figure><iref primary="true" item="Grammar" subitem="request-header"/><artwork type="abnf2616"><![CDATA[
371  request-header = Accept                   ; [Part3], Section 6.1
372                 | Accept-Charset           ; [Part3], Section 6.2
373                 | Accept-Encoding          ; [Part3], Section 6.3
374                 | Accept-Language          ; [Part3], Section 6.4
375                 | Authorization            ; [Part7], Section 4.1
376                 | Expect                   ; Section 10.2
377                 | From                     ; Section 10.3
378                 | Host                     ; [Part1], Section 8.4
379                 | If-Match                 ; [Part4], Section 7.2
380                 | If-Modified-Since        ; [Part4], Section 7.3
381                 | If-None-Match            ; [Part4], Section 7.4
382                 | If-Range                 ; [Part5], Section 6.3
383                 | If-Unmodified-Since      ; [Part4], Section 7.5
384                 | Max-Forwards             ; Section 10.5
385                 | Proxy-Authorization      ; [Part7], Section 4.3
386                 | Range                    ; [Part5], Section 6.4
387                 | Referer                  ; Section 10.6
388                 | TE                       ; [Part1], Section 8.8
389                 | User-Agent               ; Section 10.9
390]]></artwork></figure>
391<t>
392   Request-header field names can be extended reliably only in
393   combination with a change in the protocol version. However, new or
394   experimental header fields MAY be given the semantics of request-header
395   fields if all parties in the communication recognize them to
396   be request-header fields. Unrecognized header fields are treated as
397   entity-header fields.
398</t>
399</section>
400
401<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
402 
403 
404<t>
405   The Status-Code element is a 3-digit integer result code of the
406   attempt to understand and satisfy the request. The status codes listed
407   below are defined in <xref target="status.codes"/>.
408   The Reason-Phrase is intended to give a short
409   textual description of the Status-Code. The Status-Code is intended
410   for use by automata and the Reason-Phrase is intended for the human
411   user. The client is not required to examine or display the Reason-Phrase.
412</t>
413<t> 
414   The individual values of the numeric status codes defined for
415   HTTP/1.1, and an example set of corresponding Reason-Phrase's, are
416   presented below. The reason phrases listed here are only
417   recommendations -- they MAY be replaced by local equivalents without
418   affecting the protocol.
419</t>
420<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[
421  Status-Code    =
422         "100"  ; Section 9.1.1: Continue
423       | "101"  ; Section 9.1.2: Switching Protocols
424       | "200"  ; Section 9.2.1: OK
425       | "201"  ; Section 9.2.2: Created
426       | "202"  ; Section 9.2.3: Accepted
427       | "203"  ; Section 9.2.4: Non-Authoritative Information
428       | "204"  ; Section 9.2.5: No Content
429       | "205"  ; Section 9.2.6: Reset Content
430       | "206"  ; Section 9.2.7: Partial Content
431       | "300"  ; Section 9.3.1: Multiple Choices
432       | "301"  ; Section 9.3.2: Moved Permanently
433       | "302"  ; Section 9.3.3: Found
434       | "303"  ; Section 9.3.4: See Other
435       | "304"  ; Section 9.3.5: Not Modified
436       | "305"  ; Section 9.3.6: Use Proxy
437       | "307"  ; Section 9.3.8: Temporary Redirect
438       | "400"  ; Section 9.4.1: Bad Request
439       | "401"  ; Section 9.4.2: Unauthorized
440       | "402"  ; Section 9.4.3: Payment Required
441       | "403"  ; Section 9.4.4: Forbidden
442       | "404"  ; Section 9.4.5: Not Found
443       | "405"  ; Section 9.4.6: Method Not Allowed
444       | "406"  ; Section 9.4.7: Not Acceptable
445       | "407"  ; Section 9.4.8: Proxy Authentication Required
446       | "408"  ; Section 9.4.9: Request Time-out
447       | "409"  ; Section 9.4.10: Conflict
448       | "410"  ; Section 9.4.11: Gone
449       | "411"  ; Section 9.4.12: Length Required
450       | "412"  ; Section 9.4.13: Precondition Failed
451       | "413"  ; Section 9.4.14: Request Entity Too Large
452       | "414"  ; Section 9.4.15: Request-URI Too Large
453       | "415"  ; Section 9.4.16: Unsupported Media Type
454       | "416"  ; Section 9.4.17: Requested range not satisfiable
455       | "417"  ; Section 9.4.18: Expectation Failed
456       | "500"  ; Section 9.5.1: Internal Server Error
457       | "501"  ; Section 9.5.2: Not Implemented
458       | "502"  ; Section 9.5.3: Bad Gateway
459       | "503"  ; Section 9.5.4: Service Unavailable
460       | "504"  ; Section 9.5.5: Gateway Time-out
461       | "505"  ; Section 9.5.6: HTTP Version not supported
462       | extension-code
463
464  extension-code = 3DIGIT
465  Reason-Phrase  = *<TEXT, excluding CR, LF>
466]]></artwork></figure>
467<t>
468   HTTP status codes are extensible. HTTP applications are not required
469   to understand the meaning of all registered status codes, though such
470   understanding is obviously desirable. However, applications MUST
471   understand the class of any status code, as indicated by the first
472   digit, and treat any unrecognized response as being equivalent to the
473   x00 status code of that class, with the exception that an
474   unrecognized response MUST NOT be cached. For example, if an
475   unrecognized status code of 431 is received by the client, it can
476   safely assume that there was something wrong with its request and
477   treat the response as if it had received a 400 status code. In such
478   cases, user agents SHOULD present to the user the entity returned
479   with the response, since that entity is likely to include human-readable
480   information which will explain the unusual status.
481</t>
482
483<section title="Status Code Registry" anchor="status.code.registry">
484<t>
485  The HTTP Status Code Registry defines the name space for the Status-Code
486  token in the Status line of an HTTP response.
487</t>
488<t>
489  Values to be added to this name space are subject to IETF review
490  (<xref target="RFC5226"/>, Section 4.1).  Any document registering
491  new status codes should be traceable through statuses of either 'Obsoletes'
492  or 'Updates' to this document.
493</t>
494<t>
495  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
496</t>
497</section>
498
499</section>
500
501<section title="Response Header Fields" anchor="response.header.fields">
502 
503<t>
504   The response-header fields allow the server to pass additional
505   information about the response which cannot be placed in the Status-Line.
506   These header fields give information about the server and about
507   further access to the resource identified by the Request-URI.
508</t>
509<figure><iref primary="true" item="Grammar" subitem="response-header"/><artwork type="abnf2616"><![CDATA[
510  response-header = Accept-Ranges           ; [Part5], Section 6.1
511                  | Age                     ; [Part6], Section 16.1
512                  | Allow                   ; Section 10.1
513                  | ETag                    ; [Part4], Section 7.1
514                  | Location                ; Section 10.4
515                  | Proxy-Authenticate      ; [Part7], Section 4.2
516                  | Retry-After             ; Section 10.7
517                  | Server                  ; Section 10.8
518                  | Vary                    ; [Part6], Section 16.5
519                  | WWW-Authenticate        ; [Part7], Section 4.4
520]]></artwork></figure>
521<t>
522   Response-header field names can be extended reliably only in
523   combination with a change in the protocol version. However, new or
524   experimental header fields MAY be given the semantics of response-header
525   fields if all parties in the communication recognize them to
526   be response-header fields. Unrecognized header fields are treated as
527   entity-header fields.
528</t>
529</section>
530
531<section title="Entity" anchor="entity">
532<t>
533   Request and Response messages MAY transfer an entity if not otherwise
534   restricted by the request method or response status code. An entity
535   consists of entity-header fields and an entity-body, although some
536   responses will only include the entity-headers. HTTP entity-body and
537   entity-header fields are defined in <xref target="Part3"/>.
538</t>
539<t>
540   An entity-body is only present in a message when a message-body is
541   present, as described in Section 4.3 of <xref target="Part1"/>. The entity-body is obtained
542   from the message-body by decoding any Transfer-Encoding that might
543   have been applied to ensure safe and proper transfer of the message.
544</t>
545</section>
546
547
548<section title="Method Definitions" anchor="method.definitions">
549<t>
550   The set of common methods for HTTP/1.1 is defined below. Although
551   this set can be expanded, additional methods cannot be assumed to
552   share the same semantics for separately extended clients and servers.
553</t>
554
555<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
556
557<section title="Safe Methods" anchor="safe.methods">
558<t>
559   Implementors should be aware that the software represents the user in
560   their interactions over the Internet, and should be careful to allow
561   the user to be aware of any actions they might take which may have an
562   unexpected significance to themselves or others.
563</t>
564<t>
565   In particular, the convention has been established that the GET and
566   HEAD methods SHOULD NOT  have the significance of taking an action
567   other than retrieval. These methods ought to be considered "safe".
568   This allows user agents to represent other methods, such as POST, PUT
569   and DELETE, in a special way, so that the user is made aware of the
570   fact that a possibly unsafe action is being requested.
571</t>
572<t>
573   Naturally, it is not possible to ensure that the server does not
574   generate side-effects as a result of performing a GET request; in
575   fact, some dynamic resources consider that a feature. The important
576   distinction here is that the user did not request the side-effects,
577   so therefore cannot be held accountable for them.
578</t>
579</section>
580
581<section title="Idempotent Methods" anchor="idempotent.methods">
582<t>
583   Methods can also have the property of "idempotence" in that (aside
584   from error or expiration issues) the side-effects of N &gt; 0 identical
585   requests is the same as for a single request. The methods GET, HEAD,
586   PUT and DELETE share this property. Also, the methods OPTIONS and
587   TRACE SHOULD NOT  have side effects, and so are inherently idempotent.
588</t>
589<t>
590   However, it is possible that a sequence of several requests is non-idempotent,
591   even if all of the methods executed in that sequence are
592   idempotent. (A sequence is idempotent if a single execution of the
593   entire sequence always yields a result that is not changed by a
594   reexecution of all, or part, of that sequence.) For example, a
595   sequence is non-idempotent if its result depends on a value that is
596   later modified in the same sequence.
597</t>
598<t>
599   A sequence that never has side effects is idempotent, by definition
600   (provided that no concurrent operations are being executed on the
601   same set of resources).
602</t>
603</section>
604</section>
605
606<section title="OPTIONS" anchor="OPTIONS">
607  <iref primary="true" item="OPTIONS method"/>
608  <iref primary="true" item="Methods" subitem="OPTIONS"/>
609<t>
610   The OPTIONS method represents a request for information about the
611   communication options available on the request/response chain
612   identified by the Request-URI. This method allows the client to
613   determine the options and/or requirements associated with a resource,
614   or the capabilities of a server, without implying a resource action
615   or initiating a resource retrieval.
616</t>
617<t>
618   Responses to this method are not cacheable.
619</t>
620<t>
621   If the OPTIONS request includes an entity-body (as indicated by the
622   presence of Content-Length or Transfer-Encoding), then the media type
623   MUST be indicated by a Content-Type field. Although this
624   specification does not define any use for such a body, future
625   extensions to HTTP might use the OPTIONS body to make more detailed
626   queries on the server. A server that does not support such an
627   extension MAY discard the request body.
628</t>
629<t>
630   If the Request-URI is an asterisk ("*"), the OPTIONS request is
631   intended to apply to the server in general rather than to a specific
632   resource. Since a server's communication options typically depend on
633   the resource, the "*" request is only useful as a "ping" or "no-op"
634   type of method; it does nothing beyond allowing the client to test
635   the capabilities of the server. For example, this can be used to test
636   a proxy for HTTP/1.1 compliance (or lack thereof).
637</t>
638<t>
639   If the Request-URI is not an asterisk, the OPTIONS request applies
640   only to the options that are available when communicating with that
641   resource.
642</t>
643<t>
644   A 200 response SHOULD include any header fields that indicate
645   optional features implemented by the server and applicable to that
646   resource (e.g., Allow), possibly including extensions not defined by
647   this specification. The response body, if any, SHOULD also include
648   information about the communication options. The format for such a
649   body is not defined by this specification, but might be defined by
650   future extensions to HTTP. Content negotiation MAY be used to select
651   the appropriate response format. If no response body is included, the
652   response MUST include a Content-Length field with a field-value of
653   "0".
654</t>
655<t>
656   The Max-Forwards request-header field MAY be used to target a
657   specific proxy in the request chain. When a proxy receives an OPTIONS
658   request on an absoluteURI for which request forwarding is permitted,
659   the proxy MUST check for a Max-Forwards field. If the Max-Forwards
660   field-value is zero ("0"), the proxy MUST NOT forward the message;
661   instead, the proxy SHOULD respond with its own communication options.
662   If the Max-Forwards field-value is an integer greater than zero, the
663   proxy MUST decrement the field-value when it forwards the request. If
664   no Max-Forwards field is present in the request, then the forwarded
665   request MUST NOT include a Max-Forwards field.
666</t>
667</section>
668
669<section title="GET" anchor="GET">
670  <iref primary="true" item="GET method"/>
671  <iref primary="true" item="Methods" subitem="GET"/>
672<t>
673   The GET method means retrieve whatever information (in the form of an
674   entity) is identified by the Request-URI. If the Request-URI refers
675   to a data-producing process, it is the produced data which shall be
676   returned as the entity in the response and not the source text of the
677   process, unless that text happens to be the output of the process.
678</t>
679<t>
680   The semantics of the GET method change to a "conditional GET" if the
681   request message includes an If-Modified-Since, If-Unmodified-Since,
682   If-Match, If-None-Match, or If-Range header field. A conditional GET
683   method requests that the entity be transferred only under the
684   circumstances described by the conditional header field(s). The
685   conditional GET method is intended to reduce unnecessary network
686   usage by allowing cached entities to be refreshed without requiring
687   multiple requests or transferring data already held by the client.
688</t>
689<t>
690   The semantics of the GET method change to a "partial GET" if the
691   request message includes a Range header field. A partial GET requests
692   that only part of the entity be transferred, as described in Section 6.4 of <xref target="Part5"/>.
693   The partial GET method is intended to reduce unnecessary
694   network usage by allowing partially-retrieved entities to be
695   completed without transferring data already held by the client.
696</t>
697<t>
698   The response to a GET request is cacheable if and only if it meets
699   the requirements for HTTP caching described in <xref target="Part6"/>.
700</t>
701<t>
702   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
703</t>
704</section>
705
706<section title="HEAD" anchor="HEAD">
707  <iref primary="true" item="HEAD method"/>
708  <iref primary="true" item="Methods" subitem="HEAD"/>
709<t>
710   The HEAD method is identical to GET except that the server MUST NOT
711   return a message-body in the response. The metainformation contained
712   in the HTTP headers in response to a HEAD request SHOULD be identical
713   to the information sent in response to a GET request. This method can
714   be used for obtaining metainformation about the entity implied by the
715   request without transferring the entity-body itself. This method is
716   often used for testing hypertext links for validity, accessibility,
717   and recent modification.
718</t>
719<t>
720   The response to a HEAD request MAY be cacheable in the sense that the
721   information contained in the response MAY be used to update a
722   previously cached entity from that resource. If the new field values
723   indicate that the cached entity differs from the current entity (as
724   would be indicated by a change in Content-Length, Content-MD5, ETag
725   or Last-Modified), then the cache MUST treat the cache entry as
726   stale.
727</t>
728</section>
729
730<section title="POST" anchor="POST">
731  <iref primary="true" item="POST method"/>
732  <iref primary="true" item="Methods" subitem="POST"/>
733<t>
734   The POST method is used to request that the origin server accept the
735   entity enclosed in the request as data to be processed by the resource
736   identified by the Request-URI in the Request-Line. POST is designed
737   to allow a uniform method to cover the following functions:
738  <list style="symbols">
739    <t>
740      Annotation of existing resources;
741    </t>
742    <t>
743        Posting a message to a bulletin board, newsgroup, mailing list,
744        or similar group of articles;
745    </t>
746    <t>
747        Providing a block of data, such as the result of submitting a
748        form, to a data-handling process;
749    </t>
750    <t>
751        Extending a database through an append operation.
752    </t>
753  </list>
754</t>
755<t>
756   The actual function performed by the POST method is determined by the
757   server and is usually dependent on the Request-URI.
758</t>
759<t>
760   The action performed by the POST method might not result in a
761   resource that can be identified by a URI. In this case, either 200
762   (OK) or 204 (No Content) is the appropriate response status,
763   depending on whether or not the response includes an entity that
764   describes the result.
765</t>
766<t>
767   If a resource has been created on the origin server, the response
768   SHOULD be 201 (Created) and contain an entity which describes the
769   status of the request and refers to the new resource, and a Location
770   header (see <xref target="header.location"/>).
771</t>
772<t>
773   Responses to this method are not cacheable, unless the response
774   includes appropriate Cache-Control or Expires header fields. However,
775   the 303 (See Other) response can be used to direct the user agent to
776   retrieve a cacheable resource.
777</t>
778</section>
779
780<section title="PUT" anchor="PUT">
781  <iref primary="true" item="PUT method"/>
782  <iref primary="true" item="Methods" subitem="PUT"/>
783<t>
784   The PUT method requests that the enclosed entity be stored at the
785   supplied Request-URI. If the Request-URI refers to an already
786   existing resource, the enclosed entity SHOULD be considered as a
787   modified version of the one residing on the origin server. If the
788   Request-URI does not point to an existing resource, and that URI is
789   capable of being defined as a new resource by the requesting user
790   agent, the origin server can create the resource with that URI. If a
791   new resource is created at the Request-URI, the origin server MUST
792         inform the user agent
793   via the 201 (Created) response. If an existing resource is modified,
794   either the 200 (OK) or 204 (No Content) response codes SHOULD be sent
795   to indicate successful completion of the request. If the resource
796   could not be created or modified with the Request-URI, an appropriate
797   error response SHOULD be given that reflects the nature of the
798   problem. The recipient of the entity MUST NOT ignore any Content-*
799   (e.g. Content-Range) headers that it does not understand or implement
800   and MUST return a 501 (Not Implemented) response in such cases.
801</t>
802<t>
803   If the request passes through a cache and the Request-URI identifies
804   one or more currently cached entities, those entries SHOULD be
805   treated as stale. Responses to this method are not cacheable.
806</t>
807<t>
808   The fundamental difference between the POST and PUT requests is
809   reflected in the different meaning of the Request-URI. The URI in a
810   POST request identifies the resource that will handle the enclosed
811   entity. That resource might be a data-accepting process, a gateway to
812   some other protocol, or a separate entity that accepts annotations.
813   In contrast, the URI in a PUT request identifies the entity enclosed
814   with the request -- the user agent knows what URI is intended and the
815   server MUST NOT attempt to apply the request to some other resource.
816   If the server desires that the request be applied to a different URI,
817   it MUST send a 301 (Moved Permanently) response; the user agent MAY
818   then make its own decision regarding whether or not to redirect the
819   request.
820</t>
821<t>
822   A single resource MAY be identified by many different URIs. For
823   example, an article might have a URI for identifying "the current
824   version" which is separate from the URI identifying each particular
825   version. In this case, a PUT request on a general URI might result in
826   several other URIs being defined by the origin server.
827</t>
828<t>
829   HTTP/1.1 does not define how a PUT method affects the state of an
830   origin server.
831</t>
832<t>
833   Unless otherwise specified for a particular entity-header, the
834   entity-headers in the PUT request SHOULD be applied to the resource
835   created or modified by the PUT.
836</t>
837</section>
838
839<section title="DELETE" anchor="DELETE">
840  <iref primary="true" item="DELETE method"/>
841  <iref primary="true" item="Methods" subitem="DELETE"/>
842<t>
843   The DELETE method requests that the origin server delete the resource
844   identified by the Request-URI. This method MAY be overridden by human
845   intervention (or other means) on the origin server. The client cannot
846   be guaranteed that the operation has been carried out, even if the
847   status code returned from the origin server indicates that the action
848   has been completed successfully. However, the server SHOULD NOT
849   indicate success unless, at the time the response is given, it
850   intends to delete the resource or move it to an inaccessible
851   location.
852</t>
853<t>
854   A successful response SHOULD be 200 (OK) if the response includes an
855   entity describing the status, 202 (Accepted) if the action has not
856   yet been enacted, or 204 (No Content) if the action has been enacted
857   but the response does not include an entity.
858</t>
859<t>
860   If the request passes through a cache and the Request-URI identifies
861   one or more currently cached entities, those entries SHOULD be
862   treated as stale. Responses to this method are not cacheable.
863</t>
864</section>
865
866<section title="TRACE" anchor="TRACE">
867  <iref primary="true" item="TRACE method"/>
868  <iref primary="true" item="Methods" subitem="TRACE"/>
869<t>
870   The TRACE method is used to invoke a remote, application-layer loop-back
871   of the request message. The final recipient of the request
872   SHOULD reflect the message received back to the client as the
873   entity-body of a 200 (OK) response. The final recipient is either the
874   origin server or the first proxy or gateway to receive a Max-Forwards
875   value of zero (0) in the request (see <xref target="header.max-forwards"/>). A TRACE request
876   MUST NOT include an entity.
877</t>
878<t>
879   TRACE allows the client to see what is being received at the other
880   end of the request chain and use that data for testing or diagnostic
881   information. The value of the Via header field (Section 8.9 of <xref target="Part1"/>) is of
882   particular interest, since it acts as a trace of the request chain.
883   Use of the Max-Forwards header field allows the client to limit the
884   length of the request chain, which is useful for testing a chain of
885   proxies forwarding messages in an infinite loop.
886</t>
887<t>
888   If the request is valid, the response SHOULD contain the entire
889   request message in the entity-body, with a Content-Type of
890   "message/http" (see Appendix A.1 of <xref target="Part1"/>). Responses to this method
891   MUST NOT be cached.
892</t>
893</section>
894
895<section title="CONNECT" anchor="CONNECT">
896  <iref primary="true" item="CONNECT method"/>
897  <iref primary="true" item="Methods" subitem="CONNECT"/>
898<t>
899   This specification reserves the method name CONNECT for use with a
900   proxy that can dynamically switch to being a tunnel (e.g. SSL
901   tunneling <xref target="Luo1998"/>).
902</t>
903</section>
904</section>
905
906
907<section title="Status Code Definitions" anchor="status.codes">
908<t>
909   Each Status-Code is described below, including a description of which
910   method(s) it can follow and any metainformation required in the
911   response.
912</t>
913
914<section title="Informational 1xx" anchor="status.1xx">
915<t>
916   This class of status code indicates a provisional response,
917   consisting only of the Status-Line and optional headers, and is
918   terminated by an empty line. There are no required headers for this
919   class of status code. Since HTTP/1.0 did not define any 1xx status
920   codes, servers MUST NOT send a 1xx response to an HTTP/1.0 client
921   except under experimental conditions.
922</t>
923<t>
924   A client MUST be prepared to accept one or more 1xx status responses
925   prior to a regular response, even if the client does not expect a 100
926   (Continue) status message. Unexpected 1xx status responses MAY be
927   ignored by a user agent.
928</t>
929<t>
930   Proxies MUST forward 1xx responses, unless the connection between the
931   proxy and its client has been closed, or unless the proxy itself
932   requested the generation of the 1xx response. (For example, if a
933   proxy adds a "Expect: 100-continue" field when it forwards a request,
934   then it need not forward the corresponding 100 (Continue)
935   response(s).)
936</t>
937
938<section title="100 Continue" anchor="status.100">
939  <iref primary="true" item="100 Continue (status code)"/>
940  <iref primary="true" item="Status Codes" subitem="100 Continue"/>
941<t>
942   The client SHOULD continue with its request. This interim response is
943   used to inform the client that the initial part of the request has
944   been received and has not yet been rejected by the server. The client
945   SHOULD continue by sending the remainder of the request or, if the
946   request has already been completed, ignore this response. The server
947   MUST send a final response after the request has been completed. See
948   Section 7.2.3 of <xref target="Part1"/> for detailed discussion of the use and handling of this
949   status code.
950</t>
951</section>
952
953<section title="101 Switching Protocols" anchor="status.101">
954  <iref primary="true" item="101 Switching Protocols (status code)"/>
955  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols"/>
956<t>
957   The server understands and is willing to comply with the client's
958   request, via the Upgrade message header field (Section 6.4 of <xref target="Part5"/>), for a
959   change in the application protocol being used on this connection. The
960   server will switch protocols to those defined by the response's
961   Upgrade header field immediately after the empty line which
962   terminates the 101 response.
963</t>
964<t>
965   The protocol SHOULD be switched only when it is advantageous to do
966   so. For example, switching to a newer version of HTTP is advantageous
967   over older versions, and switching to a real-time, synchronous
968   protocol might be advantageous when delivering resources that use
969   such features.
970</t>
971</section>
972</section>
973
974<section title="Successful 2xx" anchor="status.2xx">
975<t>
976   This class of status code indicates that the client's request was
977   successfully received, understood, and accepted.
978</t>
979
980<section title="200 OK" anchor="status.200">
981  <iref primary="true" item="200 OK (status code)"/>
982  <iref primary="true" item="Status Codes" subitem="200 OK"/>
983<t>
984   The request has succeeded. The information returned with the response
985   is dependent on the method used in the request, for example:
986  <list style="hanging">
987    <t hangText="GET">
988          an entity corresponding to the requested resource is sent in
989          the response;
990    </t>
991    <t hangText="HEAD">
992          the entity-header fields corresponding to the requested
993          resource are sent in the response without any message-body;
994    </t>
995    <t hangText="POST">
996      an entity describing or containing the result of the action;
997    </t>
998    <t hangText="TRACE">
999      an entity containing the request message as received by the
1000      end server.
1001    </t>
1002  </list>
1003</t>
1004</section>
1005
1006<section title="201 Created" anchor="status.201">
1007  <iref primary="true" item="201 Created (status code)"/>
1008  <iref primary="true" item="Status Codes" subitem="201 Created"/>
1009<t>
1010   The request has been fulfilled and resulted in a new resource being
1011   created. The newly created resource can be referenced by the URI(s)
1012   returned in the entity of the response, with the most specific URI
1013   for the resource given by a Location header field. The response
1014   SHOULD include an entity containing a list of resource
1015   characteristics and location(s) from which the user or user agent can
1016   choose the one most appropriate. The entity format is specified by
1017   the media type given in the Content-Type header field. The origin
1018   server MUST create the resource before returning the 201 status code.
1019   If the action cannot be carried out immediately, the server SHOULD
1020   respond with 202 (Accepted) response instead.
1021</t>
1022<t>
1023   A 201 response MAY contain an ETag response header field indicating
1024   the current value of the entity tag for the requested variant just
1025   created, see Section 7.1 of <xref target="Part4"/>.
1026</t>
1027</section>
1028
1029<section title="202 Accepted" anchor="status.202">
1030  <iref primary="true" item="202 Accepted (status code)"/>
1031  <iref primary="true" item="Status Codes" subitem="202 Accepted"/>
1032<t>
1033   The request has been accepted for processing, but the processing has
1034   not been completed.  The request might or might not eventually be
1035   acted upon, as it might be disallowed when processing actually takes
1036   place. There is no facility for re-sending a status code from an
1037   asynchronous operation such as this.
1038</t>
1039<t>
1040   The 202 response is intentionally non-committal. Its purpose is to
1041   allow a server to accept a request for some other process (perhaps a
1042   batch-oriented process that is only run once per day) without
1043   requiring that the user agent's connection to the server persist
1044   until the process is completed. The entity returned with this
1045   response SHOULD include an indication of the request's current status
1046   and either a pointer to a status monitor or some estimate of when the
1047   user can expect the request to be fulfilled.
1048</t>
1049</section>
1050
1051<section title="203 Non-Authoritative Information" anchor="status.203">
1052  <iref primary="true" item="203 Non-Authoritative Information (status code)"/>
1053  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information"/>
1054<t>
1055   The returned metainformation in the entity-header is not the
1056   definitive set as available from the origin server, but is gathered
1057   from a local or a third-party copy. The set presented MAY be a subset
1058   or superset of the original version. For example, including local
1059   annotation information about the resource might result in a superset
1060   of the metainformation known by the origin server. Use of this
1061   response code is not required and is only appropriate when the
1062   response would otherwise be 200 (OK).
1063</t>
1064</section>
1065
1066<section title="204 No Content" anchor="status.204">
1067  <iref primary="true" item="204 No Content (status code)"/>
1068  <iref primary="true" item="Status Codes" subitem="204 No Content"/>
1069<t>
1070   The server has fulfilled the request but does not need to return an
1071   entity-body, and might want to return updated metainformation. The
1072   response MAY include new or updated metainformation in the form of
1073   entity-headers, which if present SHOULD be associated with the
1074   requested variant.
1075</t>
1076<t>
1077   If the client is a user agent, it SHOULD NOT  change its document view
1078   from that which caused the request to be sent. This response is
1079   primarily intended to allow input for actions to take place without
1080   causing a change to the user agent's active document view, although
1081   any new or updated metainformation SHOULD be applied to the document
1082   currently in the user agent's active view.
1083</t>
1084<t>
1085   The 204 response MUST NOT include a message-body, and thus is always
1086   terminated by the first empty line after the header fields.
1087</t>
1088</section>
1089
1090<section title="205 Reset Content" anchor="status.205">
1091  <iref primary="true" item="205 Reset Content (status code)"/>
1092  <iref primary="true" item="Status Codes" subitem="205 Reset Content"/>
1093<t>
1094   The server has fulfilled the request and the user agent SHOULD reset
1095   the document view which caused the request to be sent. This response
1096   is primarily intended to allow input for actions to take place via
1097   user input, followed by a clearing of the form in which the input is
1098   given so that the user can easily initiate another input action. The
1099   response MUST NOT include an entity.
1100</t>
1101</section>
1102
1103<section title="206 Partial Content" anchor="status.206">
1104  <iref primary="true" item="206 Partial Content (status code)"/>
1105  <iref primary="true" item="Status Codes" subitem="206 Partial Content"/>
1106<t>
1107   The server has fulfilled the partial GET request for the resource
1108   and the enclosed entity is a partial representation as defined in <xref target="Part5"/>.
1109</t>
1110</section>
1111</section>
1112
1113<section title="Redirection 3xx" anchor="status.3xx">
1114<t>
1115   This class of status code indicates that further action needs to be
1116   taken by the user agent in order to fulfill the request.  The action
1117   required MAY be carried out by the user agent without interaction
1118   with the user if and only if the method used in the second request is
1119   GET or HEAD. A client SHOULD detect infinite redirection loops, since
1120   such loops generate network traffic for each redirection.
1121  <list><t>
1122      Note: previous versions of this specification recommended a
1123      maximum of five redirections. Content developers should be aware
1124      that there might be clients that implement such a fixed
1125      limitation.
1126  </t></list>
1127</t>
1128
1129<section title="300 Multiple Choices" anchor="status.300">
1130  <iref primary="true" item="300 Multiple Choices (status code)"/>
1131  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices"/>
1132<t>
1133   The requested resource corresponds to any one of a set of
1134   representations, each with its own specific location, and agent-driven
1135   negotiation information (Section 5 of <xref target="Part3"/>) is being provided so that
1136   the user (or user agent) can select a preferred representation and
1137   redirect its request to that location.
1138</t>
1139<t>
1140   Unless it was a HEAD request, the response SHOULD include an entity
1141   containing a list of resource characteristics and location(s) from
1142   which the user or user agent can choose the one most appropriate. The
1143   entity format is specified by the media type given in the Content-Type
1144   header field. Depending upon the format and the capabilities of
1145   the user agent, selection of the most appropriate choice MAY be
1146   performed automatically. However, this specification does not define
1147   any standard for such automatic selection.
1148</t>
1149<t>
1150   If the server has a preferred choice of representation, it SHOULD
1151   include the specific URI for that representation in the Location
1152   field; user agents MAY use the Location field value for automatic
1153   redirection. This response is cacheable unless indicated otherwise.
1154</t>
1155</section>
1156
1157<section title="301 Moved Permanently" anchor="status.301">
1158  <iref primary="true" item="301 Moved Permanently (status code)"/>
1159  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently"/>
1160<t>
1161   The requested resource has been assigned a new permanent URI and any
1162   future references to this resource SHOULD use one of the returned
1163   URIs.  Clients with link editing capabilities ought to automatically
1164   re-link references to the Request-URI to one or more of the new
1165   references returned by the server, where possible. This response is
1166   cacheable unless indicated otherwise.
1167</t>
1168<t>
1169   The new permanent URI SHOULD be given by the Location field in the
1170   response. Unless the request method was HEAD, the entity of the
1171   response SHOULD contain a short hypertext note with a hyperlink to
1172   the new URI(s).
1173</t>
1174<t>
1175   If the 301 status code is received in response to a request method
1176   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1177   then the request MAY be automatically redirected by the user agent without
1178   confirmation.  Otherwise, the user agent MUST NOT automatically redirect the
1179   request unless it can be confirmed by the user, since this might
1180   change the conditions under which the request was issued.
1181  <list><t>
1182      Note: When automatically redirecting a POST request after
1183      receiving a 301 status code, some existing HTTP/1.0 user agents
1184      will erroneously change it into a GET request.
1185  </t></list>
1186</t>
1187</section>
1188
1189<section title="302 Found" anchor="status.302">
1190  <iref primary="true" item="302 Found (status code)"/>
1191  <iref primary="true" item="Status Codes" subitem="302 Found"/>
1192<t>
1193   The requested resource resides temporarily under a different URI.
1194   Since the redirection might be altered on occasion, the client SHOULD
1195   continue to use the Request-URI for future requests.  This response
1196   is only cacheable if indicated by a Cache-Control or Expires header
1197   field.
1198</t>
1199<t>
1200   The temporary URI SHOULD be given by the Location field in the
1201   response. Unless the request method was HEAD, the entity of the
1202   response SHOULD contain a short hypertext note with a hyperlink to
1203   the new URI(s).
1204</t>
1205<t>
1206   If the 302 status code is received in response to a request method
1207   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1208   then the request MAY be automatically redirected by the user agent without
1209   confirmation.  Otherwise, the user agent MUST NOT automatically redirect the
1210   request unless it can be confirmed by the user, since this might
1211   change the conditions under which the request was issued.
1212  <list><t>
1213      Note: <xref target="RFC1945"/> and <xref target="RFC2068"/> specify that the client is not allowed
1214      to change the method on the redirected request.  However, most
1215      existing user agent implementations treat 302 as if it were a 303
1216      response, performing a GET on the Location field-value regardless
1217      of the original request method. The status codes 303 and 307 have
1218      been added for servers that wish to make unambiguously clear which
1219      kind of reaction is expected of the client.
1220  </t></list>
1221</t>
1222</section>
1223
1224<section title="303 See Other" anchor="status.303">
1225  <iref primary="true" item="303 See Other (status code)"/>
1226  <iref primary="true" item="Status Codes" subitem="303 See Other"/>
1227<t>
1228   The server directs the user agent to a different resource, indicated
1229   by a URI in the Location header field, that provides an indirect
1230   response to the original request.  The user agent MAY perform a GET
1231   request on the URI in the Location field in order to obtain a
1232   representation corresponding to the response, be redirected again,
1233   or end with an error status.  The Location URI is not a substitute
1234   reference for the originally requested resource.
1235</t>
1236<t>
1237   The 303 status is generally applicable to any HTTP method.  It is
1238   primarily used to allow the output of a POST action to redirect
1239   the user agent to a selected resource, since doing so provides the
1240   information corresponding to the POST response in a form that
1241   can be separately identified, bookmarked, and cached independent
1242   of the original request.
1243</t>
1244<t>
1245   A 303 response to a GET request indicates that the requested
1246   resource does not have a representation of its own that can be
1247   transferred by the server over HTTP.  The Location URI indicates a
1248   resource that is descriptive of the requested resource such that
1249   the follow-on representation may be useful without implying that
1250   it adequately represents the previously requested resource.
1251   Note that answers to the questions of what can be represented, what
1252   representations are adequate, and what might be a useful description
1253   are outside the scope of HTTP and thus entirely determined by the
1254   resource owner(s).
1255</t>
1256<t>
1257   A 303 response SHOULD NOT be cached unless it is indicated as
1258   cacheable by Cache-Control or Expires header fields.  Except for
1259   responses to a HEAD request, the entity of a 303 response SHOULD
1260   contain a short hypertext note with a hyperlink to the Location URI.
1261</t>
1262</section>
1263
1264<section title="304 Not Modified" anchor="status.304">
1265  <iref primary="true" item="304 Not Modified (status code)"/>
1266  <iref primary="true" item="Status Codes" subitem="304 Not Modified"/>
1267<t>
1268   The response to the request has not been modified since the conditions
1269   indicated by the client's conditional GET request, as defined in <xref target="Part4"/>.
1270</t>
1271</section>
1272
1273<section title="305 Use Proxy" anchor="status.305">
1274  <iref primary="true" item="305 Use Proxy (status code)"/>
1275  <iref primary="true" item="Status Codes" subitem="305 Use Proxy"/>
1276<t>
1277   The 305 status was defined in a previous version of this specification
1278   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1279</t>
1280</section>
1281
1282<section title="306 (Unused)" anchor="status.306">
1283  <iref primary="true" item="306 (Unused) (status code)"/>
1284  <iref primary="true" item="Status Codes" subitem="306 (Unused)"/>
1285<t>
1286   The 306 status code was used in a previous version of the
1287   specification, is no longer used, and the code is reserved.
1288</t>
1289</section>
1290
1291<section title="307 Temporary Redirect" anchor="status.307">
1292  <iref primary="true" item="307 Temporary Redirect (status code)"/>
1293  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect"/>
1294<t>
1295   The requested resource resides temporarily under a different URI.
1296   Since the redirection MAY be altered on occasion, the client SHOULD
1297   continue to use the Request-URI for future requests.  This response
1298   is only cacheable if indicated by a Cache-Control or Expires header
1299   field.
1300</t>
1301<t>
1302   The temporary URI SHOULD be given by the Location field in the
1303   response. Unless the request method was HEAD, the entity of the
1304   response SHOULD contain a short hypertext note with a hyperlink to
1305   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1306   understand the 307 status. Therefore, the note SHOULD contain the
1307   information necessary for a user to repeat the original request on
1308   the new URI.
1309</t>
1310<t>
1311   If the 307 status code is received in response to a request method
1312   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1313   then the request MAY be automatically redirected by the user agent without
1314   confirmation.  Otherwise, the user agent MUST NOT automatically redirect the
1315   request unless it can be confirmed by the user, since this might
1316   change the conditions under which the request was issued.
1317</t>
1318</section>
1319</section>
1320
1321<section title="Client Error 4xx" anchor="status.4xx">
1322<t>
1323   The 4xx class of status code is intended for cases in which the
1324   client seems to have erred. Except when responding to a HEAD request,
1325   the server SHOULD include an entity containing an explanation of the
1326   error situation, and whether it is a temporary or permanent
1327   condition. These status codes are applicable to any request method.
1328   User agents SHOULD display any included entity to the user.
1329</t>
1330<t>
1331   If the client is sending data, a server implementation using TCP
1332   SHOULD be careful to ensure that the client acknowledges receipt of
1333   the packet(s) containing the response, before the server closes the
1334   input connection. If the client continues sending data to the server
1335   after the close, the server's TCP stack will send a reset packet to
1336   the client, which may erase the client's unacknowledged input buffers
1337   before they can be read and interpreted by the HTTP application.
1338</t>
1339
1340<section title="400 Bad Request" anchor="status.400">
1341  <iref primary="true" item="400 Bad Request (status code)"/>
1342  <iref primary="true" item="Status Codes" subitem="400 Bad Request"/>
1343<t>
1344   The request could not be understood by the server due to malformed
1345   syntax. The client SHOULD NOT  repeat the request without
1346   modifications.
1347</t>
1348</section>
1349
1350<section title="401 Unauthorized" anchor="status.401">
1351  <iref primary="true" item="401 Unauthorized (status code)"/>
1352  <iref primary="true" item="Status Codes" subitem="401 Unauthorized"/>
1353<t>
1354   The request requires user authentication (see <xref target="Part7"/>).
1355</t>
1356</section>
1357
1358<section title="402 Payment Required" anchor="status.402">
1359  <iref primary="true" item="402 Payment Required (status code)"/>
1360  <iref primary="true" item="Status Codes" subitem="402 Payment Required"/>
1361<t>
1362   This code is reserved for future use.
1363</t>
1364</section>
1365
1366<section title="403 Forbidden" anchor="status.403">
1367  <iref primary="true" item="403 Forbidden (status code)"/>
1368  <iref primary="true" item="Status Codes" subitem="403 Forbidden"/>
1369<t>
1370   The server understood the request, but is refusing to fulfill it.
1371   Authorization will not help and the request SHOULD NOT  be repeated.
1372   If the request method was not HEAD and the server wishes to make
1373   public why the request has not been fulfilled, it SHOULD describe the
1374   reason for the refusal in the entity.  If the server does not wish to
1375   make this information available to the client, the status code 404
1376   (Not Found) can be used instead.
1377</t>
1378</section>
1379
1380<section title="404 Not Found" anchor="status.404">
1381  <iref primary="true" item="404 Not Found (status code)"/>
1382  <iref primary="true" item="Status Codes" subitem="404 Not Found"/>
1383<t>
1384   The server has not found anything matching the Request-URI. No
1385   indication is given of whether the condition is temporary or
1386   permanent. The 410 (Gone) status code SHOULD be used if the server
1387   knows, through some internally configurable mechanism, that an old
1388   resource is permanently unavailable and has no forwarding address.
1389   This status code is commonly used when the server does not wish to
1390   reveal exactly why the request has been refused, or when no other
1391   response is applicable.
1392</t>
1393</section>
1394
1395<section title="405 Method Not Allowed" anchor="status.405">
1396  <iref primary="true" item="405 Method Not Allowed (status code)"/>
1397  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed"/>
1398<t>
1399   The method specified in the Request-Line is not allowed for the
1400   resource identified by the Request-URI. The response MUST include an
1401   Allow header containing a list of valid methods for the requested
1402   resource.
1403</t>
1404</section>
1405
1406<section title="406 Not Acceptable" anchor="status.406">
1407  <iref primary="true" item="406 Not Acceptable (status code)"/>
1408  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable"/>
1409<t>
1410   The resource identified by the request is only capable of generating
1411   response entities which have content characteristics not acceptable
1412   according to the accept headers sent in the request.
1413</t>
1414<t>
1415   Unless it was a HEAD request, the response SHOULD include an entity
1416   containing a list of available entity characteristics and location(s)
1417   from which the user or user agent can choose the one most
1418   appropriate. The entity format is specified by the media type given
1419   in the Content-Type header field. Depending upon the format and the
1420   capabilities of the user agent, selection of the most appropriate
1421   choice MAY be performed automatically. However, this specification
1422   does not define any standard for such automatic selection.
1423  <list><t>
1424      Note: HTTP/1.1 servers are allowed to return responses which are
1425      not acceptable according to the accept headers sent in the
1426      request. In some cases, this may even be preferable to sending a
1427      406 response. User agents are encouraged to inspect the headers of
1428      an incoming response to determine if it is acceptable.
1429  </t></list>
1430</t>
1431<t>
1432   If the response could be unacceptable, a user agent SHOULD
1433   temporarily stop receipt of more data and query the user for a
1434   decision on further actions.
1435</t>
1436</section>
1437
1438<section title="407 Proxy Authentication Required" anchor="status.407">
1439  <iref primary="true" item="407 Proxy Authentication Required (status code)"/>
1440  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required"/>
1441<t>
1442   This code is similar to 401 (Unauthorized), but indicates that the
1443   client must first authenticate itself with the proxy (see <xref target="Part7"/>).
1444</t>
1445</section>
1446
1447<section title="408 Request Timeout" anchor="status.408">
1448  <iref primary="true" item="408 Request Timeout (status code)"/>
1449  <iref primary="true" item="Status Codes" subitem="408 Request Timeout"/>
1450<t>
1451   The client did not produce a request within the time that the server
1452   was prepared to wait. The client MAY repeat the request without
1453   modifications at any later time.
1454</t>
1455</section>
1456
1457<section title="409 Conflict" anchor="status.409">
1458  <iref primary="true" item="409 Conflict (status code)"/>
1459  <iref primary="true" item="Status Codes" subitem="409 Conflict"/>
1460<t>
1461   The request could not be completed due to a conflict with the current
1462   state of the resource. This code is only allowed in situations where
1463   it is expected that the user might be able to resolve the conflict
1464   and resubmit the request. The response body SHOULD include enough
1465   information for the user to recognize the source of the conflict.
1466   Ideally, the response entity would include enough information for the
1467   user or user agent to fix the problem; however, that might not be
1468   possible and is not required.
1469</t>
1470<t>
1471   Conflicts are most likely to occur in response to a PUT request. For
1472   example, if versioning were being used and the entity being PUT
1473   included changes to a resource which conflict with those made by an
1474   earlier (third-party) request, the server might use the 409 response
1475   to indicate that it can't complete the request. In this case, the
1476   response entity would likely contain a list of the differences
1477   between the two versions in a format defined by the response
1478   Content-Type.
1479</t>
1480</section>
1481
1482<section title="410 Gone" anchor="status.410">
1483  <iref primary="true" item="410 Gone (status code)"/>
1484  <iref primary="true" item="Status Codes" subitem="410 Gone"/>
1485<t>
1486   The requested resource is no longer available at the server and no
1487   forwarding address is known. This condition is expected to be
1488   considered permanent. Clients with link editing capabilities SHOULD
1489   delete references to the Request-URI after user approval. If the
1490   server does not know, or has no facility to determine, whether or not
1491   the condition is permanent, the status code 404 (Not Found) SHOULD be
1492   used instead. This response is cacheable unless indicated otherwise.
1493</t>
1494<t>
1495   The 410 response is primarily intended to assist the task of web
1496   maintenance by notifying the recipient that the resource is
1497   intentionally unavailable and that the server owners desire that
1498   remote links to that resource be removed. Such an event is common for
1499   limited-time, promotional services and for resources belonging to
1500   individuals no longer working at the server's site. It is not
1501   necessary to mark all permanently unavailable resources as "gone" or
1502   to keep the mark for any length of time -- that is left to the
1503   discretion of the server owner.
1504</t>
1505</section>
1506
1507<section title="411 Length Required" anchor="status.411">
1508  <iref primary="true" item="411 Length Required (status code)"/>
1509  <iref primary="true" item="Status Codes" subitem="411 Length Required"/>
1510<t>
1511   The server refuses to accept the request without a defined Content-Length.
1512   The client MAY repeat the request if it adds a valid
1513   Content-Length header field containing the length of the message-body
1514   in the request message.
1515</t>
1516</section>
1517
1518<section title="412 Precondition Failed" anchor="status.412">
1519  <iref primary="true" item="412 Precondition Failed (status code)"/>
1520  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed"/>
1521<t>
1522   The precondition given in one or more of the request-header fields
1523   evaluated to false when it was tested on the server, as defined in
1524   <xref target="Part4"/>.
1525</t>
1526</section>
1527
1528<section title="413 Request Entity Too Large" anchor="status.413">
1529  <iref primary="true" item="413 Request Entity Too Large (status code)"/>
1530  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large"/>
1531<t>
1532   The server is refusing to process a request because the request
1533   entity is larger than the server is willing or able to process. The
1534   server MAY close the connection to prevent the client from continuing
1535   the request.
1536</t>
1537<t>
1538   If the condition is temporary, the server SHOULD include a Retry-After
1539   header field to indicate that it is temporary and after what
1540   time the client MAY try again.
1541</t>
1542</section>
1543
1544<section title="414 Request-URI Too Long" anchor="status.414">
1545  <iref primary="true" item="414 Request-URI Too Long (status code)"/>
1546  <iref primary="true" item="Status Codes" subitem="414 Request-URI Too Long"/>
1547<t>
1548   The server is refusing to service the request because the Request-URI
1549   is longer than the server is willing to interpret. This rare
1550   condition is only likely to occur when a client has improperly
1551   converted a POST request to a GET request with long query
1552   information, when the client has descended into a URI "black hole" of
1553   redirection (e.g., a redirected URI prefix that points to a suffix of
1554   itself), or when the server is under attack by a client attempting to
1555   exploit security holes present in some servers using fixed-length
1556   buffers for reading or manipulating the Request-URI.
1557</t>
1558</section>
1559
1560<section title="415 Unsupported Media Type" anchor="status.415">
1561  <iref primary="true" item="415 Unsupported Media Type (status code)"/>
1562  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type"/>
1563<t>
1564   The server is refusing to service the request because the entity of
1565   the request is in a format not supported by the requested resource
1566   for the requested method.
1567</t>
1568</section>
1569
1570<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1571  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)"/>
1572  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable"/>
1573<t>
1574   The request included a Range request-header field (Section 6.4 of <xref target="Part5"/>) and none of
1575   the range-specifier values in this field overlap the current extent
1576   of the selected resource.
1577</t>
1578</section>
1579
1580<section title="417 Expectation Failed" anchor="status.417">
1581  <iref primary="true" item="417 Expectation Failed (status code)"/>
1582  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed"/>
1583<t>
1584   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1585   could not be met by this server, or, if the server is a proxy,
1586   the server has unambiguous evidence that the request could not be met
1587   by the next-hop server.
1588</t>
1589</section>
1590</section>
1591
1592<section title="Server Error 5xx" anchor="status.5xx">
1593<t>
1594   Response status codes beginning with the digit "5" indicate cases in
1595   which the server is aware that it has erred or is incapable of
1596   performing the request. Except when responding to a HEAD request, the
1597   server SHOULD include an entity containing an explanation of the
1598   error situation, and whether it is a temporary or permanent
1599   condition. User agents SHOULD display any included entity to the
1600   user. These response codes are applicable to any request method.
1601</t>
1602
1603<section title="500 Internal Server Error" anchor="status.500">
1604  <iref primary="true" item="500 Internal Server Error (status code)"/>
1605  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error"/>
1606<t>
1607   The server encountered an unexpected condition which prevented it
1608   from fulfilling the request.
1609</t>
1610</section>
1611
1612<section title="501 Not Implemented" anchor="status.501">
1613  <iref primary="true" item="501 Not Implemented (status code)"/>
1614  <iref primary="true" item="Status Codes" subitem="501 Not Implemented"/>
1615<t>
1616   The server does not support the functionality required to fulfill the
1617   request. This is the appropriate response when the server does not
1618   recognize the request method and is not capable of supporting it for
1619   any resource.
1620</t>
1621</section>
1622
1623<section title="502 Bad Gateway" anchor="status.502">
1624  <iref primary="true" item="502 Bad Gateway (status code)"/>
1625  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway"/>
1626<t>
1627   The server, while acting as a gateway or proxy, received an invalid
1628   response from the upstream server it accessed in attempting to
1629   fulfill the request.
1630</t>
1631</section>
1632
1633<section title="503 Service Unavailable" anchor="status.503">
1634  <iref primary="true" item="503 Service Unavailable (status code)"/>
1635  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable"/>
1636<t>
1637   The server is currently unable to handle the request due to a
1638   temporary overloading or maintenance of the server. The implication
1639   is that this is a temporary condition which will be alleviated after
1640   some delay. If known, the length of the delay MAY be indicated in a
1641   Retry-After header. If no Retry-After is given, the client SHOULD
1642   handle the response as it would for a 500 response.
1643  <list><t>
1644      Note: The existence of the 503 status code does not imply that a
1645      server must use it when becoming overloaded. Some servers may wish
1646      to simply refuse the connection.
1647  </t></list>
1648</t>
1649</section>
1650
1651<section title="504 Gateway Timeout" anchor="status.504">
1652  <iref primary="true" item="504 Gateway Timeout (status code)"/>
1653  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout"/>
1654<t>
1655   The server, while acting as a gateway or proxy, did not receive a
1656   timely response from the upstream server specified by the URI (e.g.
1657   HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed
1658   to access in attempting to complete the request.
1659  <list><t>
1660      Note: Note to implementors: some deployed proxies are known to
1661      return 400 or 500 when DNS lookups time out.
1662  </t></list>
1663</t>
1664</section>
1665
1666<section title="505 HTTP Version Not Supported" anchor="status.505">
1667  <iref primary="true" item="505 HTTP Version Not Supported (status code)"/>
1668  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported"/>
1669<t>
1670   The server does not support, or refuses to support, the protocol
1671   version that was used in the request message. The server is
1672   indicating that it is unable or unwilling to complete the request
1673   using the same major version as the client, as described in Section 3.1 of <xref target="Part1"/>,
1674   other than with this error message. The response SHOULD contain
1675   an entity describing why that version is not supported and what other
1676   protocols are supported by that server.
1677</t>
1678
1679</section>
1680</section>
1681</section>
1682
1683
1684<section title="Header Field Definitions" anchor="header.fields">
1685<t>
1686   This section defines the syntax and semantics of HTTP/1.1 header fields
1687   related to request and response semantics.
1688</t>
1689<t>
1690   For entity-header fields, both sender and recipient refer to either the
1691   client or the server, depending on who sends and who receives the entity.
1692</t>
1693
1694<section title="Allow" anchor="header.allow">
1695  <iref primary="true" item="Allow header"/>
1696  <iref primary="true" item="Headers" subitem="Allow"/>
1697 
1698<t>
1699      The Allow response-header field lists the set of methods advertised as
1700      supported by the resource identified by the Request-URI. The purpose of
1701      this field is strictly to inform the recipient of valid methods
1702      associated with the resource. An Allow header field MUST be
1703      present in a 405 (Method Not Allowed) response.
1704</t>
1705<figure><iref primary="true" item="Grammar" subitem="Allow"/><artwork type="abnf2616"><![CDATA[
1706  Allow   = "Allow" ":" #Method
1707]]></artwork></figure>
1708<t>
1709      Example of use:
1710</t>
1711<figure><artwork type="example"><![CDATA[
1712       Allow: GET, HEAD, PUT
1713]]></artwork></figure>
1714<t>
1715      The actual set of allowed methods is defined
1716      by the origin server at the time of each request.
1717</t>
1718<t>
1719      A proxy MUST NOT modify the Allow header field even if it does not
1720      understand all the methods specified, since the user agent might
1721      have other means of communicating with the origin server.
1722</t>
1723</section>
1724
1725<section title="Expect" anchor="header.expect">
1726  <iref primary="true" item="Expect header"/>
1727  <iref primary="true" item="Headers" subitem="Expect"/>
1728 
1729 
1730 
1731 
1732<t>
1733   The Expect request-header field is used to indicate that particular
1734   server behaviors are required by the client.
1735</t>
1736<figure><iref primary="true" item="Grammar" subitem="Expect"/><iref primary="true" item="Grammar" subitem="expectation"/><iref primary="true" item="Grammar" subitem="expectation-extension"/><iref primary="true" item="Grammar" subitem="expect-params"/><artwork type="abnf2616"><![CDATA[
1737  Expect       =  "Expect" ":" 1#expectation
1738 
1739  expectation  =  "100-continue" | expectation-extension
1740  expectation-extension =  token [ "=" ( token | quoted-string )
1741                           *expect-params ]
1742  expect-params =  ";" token [ "=" ( token | quoted-string ) ]
1743]]></artwork></figure>
1744<t>
1745   A server that does not understand or is unable to comply with any of
1746   the expectation values in the Expect field of a request MUST respond
1747   with appropriate error status. The server MUST respond with a 417
1748   (Expectation Failed) status if any of the expectations cannot be met
1749   or, if there are other problems with the request, some other 4xx
1750   status.
1751</t>
1752<t>
1753   This header field is defined with extensible syntax to allow for
1754   future extensions. If a server receives a request containing an
1755   Expect field that includes an expectation-extension that it does not
1756   support, it MUST respond with a 417 (Expectation Failed) status.
1757</t>
1758<t>
1759   Comparison of expectation values is case-insensitive for unquoted
1760   tokens (including the 100-continue token), and is case-sensitive for
1761   quoted-string expectation-extensions.
1762</t>
1763<t>
1764   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy MUST
1765   return a 417 (Expectation Failed) status if it receives a request
1766   with an expectation that it cannot meet. However, the Expect
1767   request-header itself is end-to-end; it MUST be forwarded if the
1768   request is forwarded.
1769</t>
1770<t>
1771   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1772   Expect header.
1773</t>
1774<t>
1775   See Section 7.2.3 of <xref target="Part1"/> for the use of the 100 (Continue) status.
1776</t>
1777</section>
1778
1779<section title="From" anchor="header.from">
1780  <iref primary="true" item="From header"/>
1781  <iref primary="true" item="Headers" subitem="From"/>
1782 
1783 
1784<t>
1785   The From request-header field, if given, SHOULD contain an Internet
1786   e-mail address for the human user who controls the requesting user
1787   agent. The address SHOULD be machine-usable, as defined by "mailbox"
1788   in Section 3.4 of <xref target="RFC2822"/>:
1789</t>
1790<figure><iref primary="true" item="Grammar" subitem="From"/><artwork type="abnf2616"><![CDATA[
1791  From    = "From" ":" mailbox
1792 
1793  mailbox = <mailbox, defined in [RFC2822], Section 3.4>
1794]]></artwork></figure>
1795<t>
1796   An example is:
1797</t>
1798<figure><artwork type="example"><![CDATA[
1799    From: webmaster@example.org
1800]]></artwork></figure>
1801<t>
1802   This header field MAY be used for logging purposes and as a means for
1803   identifying the source of invalid or unwanted requests. It SHOULD NOT
1804   be used as an insecure form of access protection. The interpretation
1805   of this field is that the request is being performed on behalf of the
1806   person given, who accepts responsibility for the method performed. In
1807   particular, robot agents SHOULD include this header so that the
1808   person responsible for running the robot can be contacted if problems
1809   occur on the receiving end.
1810</t>
1811<t>
1812   The Internet e-mail address in this field MAY be separate from the
1813   Internet host which issued the request. For example, when a request
1814   is passed through a proxy the original issuer's address SHOULD be
1815   used.
1816</t>
1817<t>
1818   The client SHOULD NOT  send the From header field without the user's
1819   approval, as it might conflict with the user's privacy interests or
1820   their site's security policy. It is strongly recommended that the
1821   user be able to disable, enable, and modify the value of this field
1822   at any time prior to a request.
1823</t>
1824</section>
1825
1826<section title="Location" anchor="header.location">
1827  <iref primary="true" item="Location header"/>
1828  <iref primary="true" item="Headers" subitem="Location"/>
1829 
1830<t>
1831   The Location response-header field is used for the identification of a
1832   new resource or to redirect the recipient to a location other than the
1833   Request-URI for completion of the request.  For 201 (Created)
1834   responses, the Location is that of the new resource which was created
1835   by the request. For 3xx responses, the location SHOULD indicate the
1836   server's preferred URI for automatic redirection to the resource. The
1837   field value consists of a single absolute URI.
1838</t>
1839<figure><iref primary="true" item="Grammar" subitem="Location"/><artwork type="abnf2616"><![CDATA[
1840  Location       = "Location" ":" absoluteURI [ "#" fragment ]
1841]]></artwork></figure>
1842<t>
1843   An example is:
1844</t>
1845<figure><artwork type="example"><![CDATA[
1846    Location: http://www.example.org/pub/WWW/People.html
1847]]></artwork></figure>
1848<t>
1849  <list><t>
1850      Note: The Content-Location header field (Section 6.7 of <xref target="Part3"/>) differs
1851      from Location in that the Content-Location identifies the original
1852      location of the entity enclosed in the request. It is therefore
1853      possible for a response to contain header fields for both Location
1854      and Content-Location.
1855  </t></list>
1856</t>
1857<t>
1858   There are circumstances in which a fragment identifier in a Location URL would not be appropriate:
1859   <list style="symbols">
1860      <t>With a 201 Created response, because in this usage the Location header specifies the URL for the entire created resource.</t>
1861      <t>With a 300 Multiple Choices, since the choice decision is intended to be made on resource characteristics and not fragment characteristics.</t>
1862      <t>With 305 Use Proxy.</t>
1863   </list>
1864</t>
1865</section>
1866
1867<section title="Max-Forwards" anchor="header.max-forwards">
1868  <iref primary="true" item="Max-Forwards header"/>
1869  <iref primary="true" item="Headers" subitem="Max-Forwards"/>
1870 
1871<t>
1872   The Max-Forwards request-header field provides a mechanism with the
1873   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>) methods to limit the
1874   number of proxies or gateways that can forward the request to the
1875   next inbound server. This can be useful when the client is attempting
1876   to trace a request chain which appears to be failing or looping in
1877   mid-chain.
1878</t>
1879<figure><iref primary="true" item="Grammar" subitem="Max-Forwards"/><artwork type="abnf2616"><![CDATA[
1880  Max-Forwards   = "Max-Forwards" ":" 1*DIGIT
1881]]></artwork></figure>
1882<t>
1883   The Max-Forwards value is a decimal integer indicating the remaining
1884   number of times this request message may be forwarded.
1885</t>
1886<t>
1887   Each proxy or gateway recipient of a TRACE or OPTIONS request
1888   containing a Max-Forwards header field MUST check and update its
1889   value prior to forwarding the request. If the received value is zero
1890   (0), the recipient MUST NOT forward the request; instead, it MUST
1891   respond as the final recipient. If the received Max-Forwards value is
1892   greater than zero, then the forwarded message MUST contain an updated
1893   Max-Forwards field with a value decremented by one (1).
1894</t>
1895<t>
1896   The Max-Forwards header field MAY be ignored for all other methods
1897   defined by this specification and for any extension methods for which
1898   it is not explicitly referred to as part of that method definition.
1899</t>
1900</section>
1901
1902<section title="Referer" anchor="header.referer">
1903  <iref primary="true" item="Referer header"/>
1904  <iref primary="true" item="Headers" subitem="Referer"/>
1905 
1906<t>
1907   The Referer[sic] request-header field allows the client to specify,
1908   for the server's benefit, the address (URI) of the resource from
1909   which the Request-URI was obtained (the "referrer", although the
1910   header field is misspelled.) The Referer request-header allows a
1911   server to generate lists of back-links to resources for interest,
1912   logging, optimized caching, etc. It also allows obsolete or mistyped
1913   links to be traced for maintenance. The Referer field MUST NOT be
1914   sent if the Request-URI was obtained from a source that does not have
1915   its own URI, such as input from the user keyboard.
1916</t>
1917<figure><iref primary="true" item="Grammar" subitem="Referer"/><artwork type="abnf2616"><![CDATA[
1918  Referer        = "Referer" ":" ( absoluteURI | relativeURI )
1919]]></artwork></figure>
1920<t>
1921   Example:
1922</t>
1923<figure><artwork type="example"><![CDATA[
1924    Referer: http://www.example.org/hypertext/Overview.html
1925]]></artwork></figure>
1926<t>
1927   If the field value is a relative URI, it SHOULD be interpreted
1928   relative to the Request-URI. The URI MUST NOT include a fragment. See
1929   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
1930</t>
1931</section>
1932
1933<section title="Retry-After" anchor="header.retry-after">
1934  <iref primary="true" item="Retry-After header"/>
1935  <iref primary="true" item="Headers" subitem="Retry-After"/>
1936 
1937<t>
1938   The Retry-After response-header field can be used with a 503 (Service
1939   Unavailable) response to indicate how long the service is expected to
1940   be unavailable to the requesting client. This field MAY also be used
1941   with any 3xx (Redirection) response to indicate the minimum time the
1942   user-agent is asked wait before issuing the redirected request. The
1943   value of this field can be either an HTTP-date or an integer number
1944   of seconds (in decimal) after the time of the response.
1945</t>
1946<figure><iref primary="true" item="Grammar" subitem="Retry-After"/><artwork type="abnf2616"><![CDATA[
1947  Retry-After   = "Retry-After" ":" ( HTTP-date | delta-seconds )
1948]]></artwork></figure>
1949<t anchor="rule.delta-seconds">
1950 
1951   Time spans are non-negative decimal integers, representing time in
1952   seconds.
1953</t>
1954<figure><iref primary="true" item="Grammar" subitem="delta-seconds"/><artwork type="abnf2616"><![CDATA[
1955  delta-seconds  = 1*DIGIT
1956]]></artwork></figure>
1957<t>
1958   Two examples of its use are
1959</t>
1960<figure><artwork type="example"><![CDATA[
1961    Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
1962    Retry-After: 120
1963]]></artwork></figure>
1964<t>
1965   In the latter example, the delay is 2 minutes.
1966</t>
1967</section>
1968
1969<section title="Server" anchor="header.server">
1970  <iref primary="true" item="Server header"/>
1971  <iref primary="true" item="Headers" subitem="Server"/>
1972 
1973<t>
1974   The Server response-header field contains information about the
1975   software used by the origin server to handle the request. The field
1976   can contain multiple product tokens (Section 3.5 of <xref target="Part1"/>) and comments
1977   identifying the server and any significant subproducts. The product
1978   tokens are listed in order of their significance for identifying the
1979   application.
1980</t>
1981<figure><iref primary="true" item="Grammar" subitem="Server"/><artwork type="abnf2616"><![CDATA[
1982  Server         = "Server" ":" 1*( product | comment )
1983]]></artwork></figure>
1984<t>
1985   Example:
1986</t>
1987<figure><artwork type="example"><![CDATA[
1988    Server: CERN/3.0 libwww/2.17
1989]]></artwork></figure>
1990<t>
1991   If the response is being forwarded through a proxy, the proxy
1992   application MUST NOT modify the Server response-header. Instead, it
1993   MUST include a Via field (as described in Section 8.9 of <xref target="Part1"/>).
1994  <list><t>
1995      Note: Revealing the specific software version of the server might
1996      allow the server machine to become more vulnerable to attacks
1997      against software that is known to contain security holes. Server
1998      implementors are encouraged to make this field a configurable
1999      option.
2000  </t></list>
2001</t>
2002</section>
2003
2004<section title="User-Agent" anchor="header.user-agent">
2005  <iref primary="true" item="User-Agent header"/>
2006  <iref primary="true" item="Headers" subitem="User-Agent"/>
2007 
2008<t>
2009   The User-Agent request-header field contains information about the
2010   user agent originating the request. This is for statistical purposes,
2011   the tracing of protocol violations, and automated recognition of user
2012   agents for the sake of tailoring responses to avoid particular user
2013   agent limitations. User agents SHOULD include this field with
2014   requests. The field can contain multiple product tokens (Section 3.5 of <xref target="Part1"/>)
2015   and comments identifying the agent and any subproducts which form a
2016   significant part of the user agent. By convention, the product tokens
2017   are listed in order of their significance for identifying the
2018   application.
2019</t>
2020<figure><iref primary="true" item="Grammar" subitem="User-Agent"/><artwork type="abnf2616"><![CDATA[
2021  User-Agent     = "User-Agent" ":" 1*( product | comment )
2022]]></artwork></figure>
2023<t>
2024   Example:
2025</t>
2026<figure><artwork type="example"><![CDATA[
2027    User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2028]]></artwork></figure>
2029</section>
2030
2031</section>
2032
2033<section title="IANA Considerations" anchor="IANA.considerations">
2034<section title="Status Code Registry" anchor="status.code.registration">
2035<t>
2036  The registration procedure for HTTP Status Codes -- previously defined
2037  in Section 7.1 of <xref target="RFC2817"/> -- is now defined
2038  by <xref target="status.code.registry"/> of this document.
2039</t>
2040<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2041<!--(START)-->
2042<t>
2043    The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2044    should be updated with the registrations below:
2045  </t>
2046<texttable>
2047   <ttcol>Value</ttcol>
2048   <ttcol>Description</ttcol>
2049   <ttcol>Reference</ttcol>
2050
2051   <c>100</c>
2052   <c>Continue</c>
2053   <c>
2054      <xref target="status.100"/>
2055   </c>
2056
2057   <c>101</c>
2058   <c>Switching Protocols</c>
2059   <c>
2060      <xref target="status.101"/>
2061   </c>
2062
2063   <c>200</c>
2064   <c>OK</c>
2065   <c>
2066      <xref target="status.200"/>
2067   </c>
2068
2069   <c>201</c>
2070   <c>Created</c>
2071   <c>
2072      <xref target="status.201"/>
2073   </c>
2074
2075   <c>202</c>
2076   <c>Accepted</c>
2077   <c>
2078      <xref target="status.202"/>
2079   </c>
2080
2081   <c>203</c>
2082   <c>Non-Authoritative Information</c>
2083   <c>
2084      <xref target="status.203"/>
2085   </c>
2086
2087   <c>204</c>
2088   <c>No Content</c>
2089   <c>
2090      <xref target="status.204"/>
2091   </c>
2092
2093   <c>205</c>
2094   <c>Reset Content</c>
2095   <c>
2096      <xref target="status.205"/>
2097   </c>
2098
2099   <c>206</c>
2100   <c>Partial Content</c>
2101   <c>
2102      <xref target="status.206"/>
2103   </c>
2104
2105   <c>300</c>
2106   <c>Multiple Choices</c>
2107   <c>
2108      <xref target="status.300"/>
2109   </c>
2110
2111   <c>301</c>
2112   <c>Moved Permanently</c>
2113   <c>
2114      <xref target="status.301"/>
2115   </c>
2116
2117   <c>302</c>
2118   <c>Found</c>
2119   <c>
2120      <xref target="status.302"/>
2121   </c>
2122
2123   <c>303</c>
2124   <c>See Other</c>
2125   <c>
2126      <xref target="status.303"/>
2127   </c>
2128
2129   <c>304</c>
2130   <c>Not Modified</c>
2131   <c>
2132      <xref target="status.304"/>
2133   </c>
2134
2135   <c>305</c>
2136   <c>Use Proxy</c>
2137   <c>
2138      <xref target="status.305"/>
2139   </c>
2140
2141   <c>306</c>
2142   <c>(Unused)</c>
2143   <c>
2144      <xref target="status.306"/>
2145   </c>
2146
2147   <c>307</c>
2148   <c>Temporary Redirect</c>
2149   <c>
2150      <xref target="status.307"/>
2151   </c>
2152
2153   <c>400</c>
2154   <c>Bad Request</c>
2155   <c>
2156      <xref target="status.400"/>
2157   </c>
2158
2159   <c>401</c>
2160   <c>Unauthorized</c>
2161   <c>
2162      <xref target="status.401"/>
2163   </c>
2164
2165   <c>402</c>
2166   <c>Payment Required</c>
2167   <c>
2168      <xref target="status.402"/>
2169   </c>
2170
2171   <c>403</c>
2172   <c>Forbidden</c>
2173   <c>
2174      <xref target="status.403"/>
2175   </c>
2176
2177   <c>404</c>
2178   <c>Not Found</c>
2179   <c>
2180      <xref target="status.404"/>
2181   </c>
2182
2183   <c>405</c>
2184   <c>Method Not Allowed</c>
2185   <c>
2186      <xref target="status.405"/>
2187   </c>
2188
2189   <c>406</c>
2190   <c>Not Acceptable</c>
2191   <c>
2192      <xref target="status.406"/>
2193   </c>
2194
2195   <c>407</c>
2196   <c>Proxy Authentication Required</c>
2197   <c>
2198      <xref target="status.407"/>
2199   </c>
2200
2201   <c>408</c>
2202   <c>Request Timeout</c>
2203   <c>
2204      <xref target="status.408"/>
2205   </c>
2206
2207   <c>409</c>
2208   <c>Conflict</c>
2209   <c>
2210      <xref target="status.409"/>
2211   </c>
2212
2213   <c>410</c>
2214   <c>Gone</c>
2215   <c>
2216      <xref target="status.410"/>
2217   </c>
2218
2219   <c>411</c>
2220   <c>Length Required</c>
2221   <c>
2222      <xref target="status.411"/>
2223   </c>
2224
2225   <c>412</c>
2226   <c>Precondition Failed</c>
2227   <c>
2228      <xref target="status.412"/>
2229   </c>
2230
2231   <c>413</c>
2232   <c>Request Entity Too Large</c>
2233   <c>
2234      <xref target="status.413"/>
2235   </c>
2236
2237   <c>414</c>
2238   <c>Request-URI Too Long</c>
2239   <c>
2240      <xref target="status.414"/>
2241   </c>
2242
2243   <c>415</c>
2244   <c>Unsupported Media Type</c>
2245   <c>
2246      <xref target="status.415"/>
2247   </c>
2248
2249   <c>416</c>
2250   <c>Requested Range Not Satisfiable</c>
2251   <c>
2252      <xref target="status.416"/>
2253   </c>
2254
2255   <c>417</c>
2256   <c>Expectation Failed</c>
2257   <c>
2258      <xref target="status.417"/>
2259   </c>
2260
2261   <c>500</c>
2262   <c>Internal Server Error</c>
2263   <c>
2264      <xref target="status.500"/>
2265   </c>
2266
2267   <c>501</c>
2268   <c>Not Implemented</c>
2269   <c>
2270      <xref target="status.501"/>
2271   </c>
2272
2273   <c>502</c>
2274   <c>Bad Gateway</c>
2275   <c>
2276      <xref target="status.502"/>
2277   </c>
2278
2279   <c>503</c>
2280   <c>Service Unavailable</c>
2281   <c>
2282      <xref target="status.503"/>
2283   </c>
2284
2285   <c>504</c>
2286   <c>Gateway Timeout</c>
2287   <c>
2288      <xref target="status.504"/>
2289   </c>
2290
2291   <c>505</c>
2292   <c>HTTP Version Not Supported</c>
2293   <c>
2294      <xref target="status.505"/>
2295   </c>
2296</texttable>
2297<!--(END)-->
2298</section>
2299<section title="Message Header Registration" anchor="message.header.registration">
2300<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2301<!--(START)-->
2302<t>
2303    The Message Header Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> should be updated
2304    with the permanent registrations below (see <xref target="RFC3864"/>):
2305  </t>
2306<texttable>
2307   <ttcol>Header Field Name</ttcol>
2308   <ttcol>Protocol</ttcol>
2309   <ttcol>Status</ttcol>
2310   <ttcol>Reference</ttcol>
2311
2312   <c>Allow</c>
2313   <c>http</c>
2314   <c>standard</c>
2315   <c>
2316      <xref target="header.allow"/>
2317   </c>
2318
2319   <c>Expect</c>
2320   <c>http</c>
2321   <c>standard</c>
2322   <c>
2323      <xref target="header.expect"/>
2324   </c>
2325
2326   <c>From</c>
2327   <c>http</c>
2328   <c>standard</c>
2329   <c>
2330      <xref target="header.from"/>
2331   </c>
2332
2333   <c>Location</c>
2334   <c>http</c>
2335   <c>standard</c>
2336   <c>
2337      <xref target="header.location"/>
2338   </c>
2339
2340   <c>Max-Forwards</c>
2341   <c>http</c>
2342   <c>standard</c>
2343   <c>
2344      <xref target="header.max-forwards"/>
2345   </c>
2346
2347   <c>Referer</c>
2348   <c>http</c>
2349   <c>standard</c>
2350   <c>
2351      <xref target="header.referer"/>
2352   </c>
2353
2354   <c>Retry-After</c>
2355   <c>http</c>
2356   <c>standard</c>
2357   <c>
2358      <xref target="header.retry-after"/>
2359   </c>
2360
2361   <c>Server</c>
2362   <c>http</c>
2363   <c>standard</c>
2364   <c>
2365      <xref target="header.server"/>
2366   </c>
2367
2368   <c>User-Agent</c>
2369   <c>http</c>
2370   <c>standard</c>
2371   <c>
2372      <xref target="header.user-agent"/>
2373   </c>
2374</texttable>
2375<t>
2376    The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2377</t>
2378<!--(END)-->
2379</section>
2380</section>
2381
2382<section title="Security Considerations" anchor="security.considerations">
2383<t>
2384   This section is meant to inform application developers, information
2385   providers, and users of the security limitations in HTTP/1.1 as
2386   described by this document. The discussion does not include
2387   definitive solutions to the problems revealed, though it does make
2388   some suggestions for reducing security risks.
2389</t>
2390
2391<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2392<t>
2393   Like any generic data transfer protocol, HTTP cannot regulate the
2394   content of the data that is transferred, nor is there any a priori
2395   method of determining the sensitivity of any particular piece of
2396   information within the context of any given request. Therefore,
2397   applications SHOULD supply as much control over this information as
2398   possible to the provider of that information. Four header fields are
2399   worth special mention in this context: Server, Via, Referer and From.
2400</t>
2401<t>
2402   Revealing the specific software version of the server might allow the
2403   server machine to become more vulnerable to attacks against software
2404   that is known to contain security holes. Implementors SHOULD make the
2405   Server header field a configurable option.
2406</t>
2407<t>
2408   Proxies which serve as a portal through a network firewall SHOULD
2409   take special precautions regarding the transfer of header information
2410   that identifies the hosts behind the firewall. In particular, they
2411   SHOULD remove, or replace with sanitized versions, any Via fields
2412   generated behind the firewall.
2413</t>
2414<t>
2415   The Referer header allows reading patterns to be studied and reverse
2416   links drawn. Although it can be very useful, its power can be abused
2417   if user details are not separated from the information contained in
2418   the Referer. Even when the personal information has been removed, the
2419   Referer header might indicate a private document's URI whose
2420   publication would be inappropriate.
2421</t>
2422<t>
2423   The information sent in the From field might conflict with the user's
2424   privacy interests or their site's security policy, and hence it
2425   SHOULD NOT  be transmitted without the user being able to disable,
2426   enable, and modify the contents of the field. The user MUST be able
2427   to set the contents of this field within a user preference or
2428   application defaults configuration.
2429</t>
2430<t>
2431   We suggest, though do not require, that a convenient toggle interface
2432   be provided for the user to enable or disable the sending of From and
2433   Referer information.
2434</t>
2435<t>
2436   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2437   fields can sometimes be used to determine that a specific client or
2438   server have a particular security hole which might be exploited.
2439   Unfortunately, this same information is often used for other valuable
2440   purposes for which HTTP currently has no better mechanism.
2441</t>
2442</section>
2443
2444<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2445<t>
2446   Because the source of a link might be private information or might
2447   reveal an otherwise private information source, it is strongly
2448   recommended that the user be able to select whether or not the
2449   Referer field is sent. For example, a browser client could have a
2450   toggle switch for browsing openly/anonymously, which would
2451   respectively enable/disable the sending of Referer and From
2452   information.
2453</t>
2454<t>
2455   Clients SHOULD NOT include a Referer header field in a (non-secure)
2456   HTTP request if the referring page was transferred with a secure
2457   protocol.
2458</t>
2459<t>
2460   Authors of services should not use
2461   GET-based forms for the submission of sensitive data because that
2462   data will be encoded in the Request-URI. Many existing
2463   servers, proxies, and user agents log or display the Request-URI in
2464   places where it might be visible to third parties. Such services can
2465   use POST-based form submission instead.
2466</t>
2467</section>
2468
2469<section title="Location Headers and Spoofing" anchor="location.spoofing">
2470<t>
2471   If a single server supports multiple organizations that do not trust
2472   one another, then it MUST check the values of Location and Content-Location
2473   headers in responses that are generated under control of
2474   said organizations to make sure that they do not attempt to
2475   invalidate resources over which they have no authority.
2476</t>
2477</section>
2478
2479</section>
2480
2481<section title="Acknowledgments" anchor="ack">
2482</section>
2483</middle>
2484<back>
2485
2486<references title="Normative References">
2487
2488<reference anchor="Part1">
2489  <front>
2490    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2491    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2492      <organization abbrev="Day Software">Day Software</organization>
2493      <address><email>fielding@gbiv.com</email></address>
2494    </author>
2495    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2496      <organization>One Laptop per Child</organization>
2497      <address><email>jg@laptop.org</email></address>
2498    </author>
2499    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2500      <organization abbrev="HP">Hewlett-Packard Company</organization>
2501      <address><email>JeffMogul@acm.org</email></address>
2502    </author>
2503    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2504      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2505      <address><email>henrikn@microsoft.com</email></address>
2506    </author>
2507    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2508      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2509      <address><email>LMM@acm.org</email></address>
2510    </author>
2511    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2512      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2513      <address><email>paulle@microsoft.com</email></address>
2514    </author>
2515    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2516      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2517      <address><email>timbl@w3.org</email></address>
2518    </author>
2519    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2520      <organization abbrev="W3C">World Wide Web Consortium</organization>
2521      <address><email>ylafon@w3.org</email></address>
2522    </author>
2523    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2524      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2525      <address><email>julian.reschke@greenbytes.de</email></address>
2526    </author>
2527    <date month="June" year="2008"/>
2528  </front>
2529  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-03"/>
2530 
2531</reference>
2532
2533<reference anchor="Part3">
2534  <front>
2535    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2536    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2537      <organization abbrev="Day Software">Day Software</organization>
2538      <address><email>fielding@gbiv.com</email></address>
2539    </author>
2540    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2541      <organization>One Laptop per Child</organization>
2542      <address><email>jg@laptop.org</email></address>
2543    </author>
2544    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2545      <organization abbrev="HP">Hewlett-Packard Company</organization>
2546      <address><email>JeffMogul@acm.org</email></address>
2547    </author>
2548    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2549      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2550      <address><email>henrikn@microsoft.com</email></address>
2551    </author>
2552    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2553      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2554      <address><email>LMM@acm.org</email></address>
2555    </author>
2556    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2557      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2558      <address><email>paulle@microsoft.com</email></address>
2559    </author>
2560    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2561      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2562      <address><email>timbl@w3.org</email></address>
2563    </author>
2564    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2565      <organization abbrev="W3C">World Wide Web Consortium</organization>
2566      <address><email>ylafon@w3.org</email></address>
2567    </author>
2568    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2569      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2570      <address><email>julian.reschke@greenbytes.de</email></address>
2571    </author>
2572    <date month="June" year="2008"/>
2573  </front>
2574  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-03"/>
2575 
2576</reference>
2577
2578<reference anchor="Part4">
2579  <front>
2580    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2581    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2582      <organization abbrev="Day Software">Day Software</organization>
2583      <address><email>fielding@gbiv.com</email></address>
2584    </author>
2585    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2586      <organization>One Laptop per Child</organization>
2587      <address><email>jg@laptop.org</email></address>
2588    </author>
2589    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2590      <organization abbrev="HP">Hewlett-Packard Company</organization>
2591      <address><email>JeffMogul@acm.org</email></address>
2592    </author>
2593    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2594      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2595      <address><email>henrikn@microsoft.com</email></address>
2596    </author>
2597    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2598      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2599      <address><email>LMM@acm.org</email></address>
2600    </author>
2601    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2602      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2603      <address><email>paulle@microsoft.com</email></address>
2604    </author>
2605    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2606      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2607      <address><email>timbl@w3.org</email></address>
2608    </author>
2609    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2610      <organization abbrev="W3C">World Wide Web Consortium</organization>
2611      <address><email>ylafon@w3.org</email></address>
2612    </author>
2613    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2614      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2615      <address><email>julian.reschke@greenbytes.de</email></address>
2616    </author>
2617    <date month="June" year="2008"/>
2618  </front>
2619  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-03"/>
2620 
2621</reference>
2622
2623<reference anchor="Part5">
2624  <front>
2625    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2626    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2627      <organization abbrev="Day Software">Day Software</organization>
2628      <address><email>fielding@gbiv.com</email></address>
2629    </author>
2630    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2631      <organization>One Laptop per Child</organization>
2632      <address><email>jg@laptop.org</email></address>
2633    </author>
2634    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2635      <organization abbrev="HP">Hewlett-Packard Company</organization>
2636      <address><email>JeffMogul@acm.org</email></address>
2637    </author>
2638    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2639      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2640      <address><email>henrikn@microsoft.com</email></address>
2641    </author>
2642    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2643      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2644      <address><email>LMM@acm.org</email></address>
2645    </author>
2646    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2647      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2648      <address><email>paulle@microsoft.com</email></address>
2649    </author>
2650    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2651      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2652      <address><email>timbl@w3.org</email></address>
2653    </author>
2654    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2655      <organization abbrev="W3C">World Wide Web Consortium</organization>
2656      <address><email>ylafon@w3.org</email></address>
2657    </author>
2658    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2659      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2660      <address><email>julian.reschke@greenbytes.de</email></address>
2661    </author>
2662    <date month="June" year="2008"/>
2663  </front>
2664  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-03"/>
2665 
2666</reference>
2667
2668<reference anchor="Part6">
2669  <front>
2670    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2671    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2672      <organization abbrev="Day Software">Day Software</organization>
2673      <address><email>fielding@gbiv.com</email></address>
2674    </author>
2675    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2676      <organization>One Laptop per Child</organization>
2677      <address><email>jg@laptop.org</email></address>
2678    </author>
2679    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2680      <organization abbrev="HP">Hewlett-Packard Company</organization>
2681      <address><email>JeffMogul@acm.org</email></address>
2682    </author>
2683    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2684      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2685      <address><email>henrikn@microsoft.com</email></address>
2686    </author>
2687    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2688      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2689      <address><email>LMM@acm.org</email></address>
2690    </author>
2691    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2692      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2693      <address><email>paulle@microsoft.com</email></address>
2694    </author>
2695    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2696      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2697      <address><email>timbl@w3.org</email></address>
2698    </author>
2699    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2700      <organization abbrev="W3C">World Wide Web Consortium</organization>
2701      <address><email>ylafon@w3.org</email></address>
2702    </author>
2703    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2704      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2705      <address><email>julian.reschke@greenbytes.de</email></address>
2706    </author>
2707    <date month="June" year="2008"/>
2708  </front>
2709  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-03"/>
2710 
2711</reference>
2712
2713<reference anchor="Part7">
2714  <front>
2715    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2716    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2717      <organization abbrev="Day Software">Day Software</organization>
2718      <address><email>fielding@gbiv.com</email></address>
2719    </author>
2720    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2721      <organization>One Laptop per Child</organization>
2722      <address><email>jg@laptop.org</email></address>
2723    </author>
2724    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2725      <organization abbrev="HP">Hewlett-Packard Company</organization>
2726      <address><email>JeffMogul@acm.org</email></address>
2727    </author>
2728    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2729      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2730      <address><email>henrikn@microsoft.com</email></address>
2731    </author>
2732    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2733      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2734      <address><email>LMM@acm.org</email></address>
2735    </author>
2736    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2737      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2738      <address><email>paulle@microsoft.com</email></address>
2739    </author>
2740    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2741      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2742      <address><email>timbl@w3.org</email></address>
2743    </author>
2744    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2745      <organization abbrev="W3C">World Wide Web Consortium</organization>
2746      <address><email>ylafon@w3.org</email></address>
2747    </author>
2748    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2749      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2750      <address><email>julian.reschke@greenbytes.de</email></address>
2751    </author>
2752    <date month="June" year="2008"/>
2753  </front>
2754  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-03"/>
2755 
2756</reference>
2757
2758<reference anchor="RFC2119">
2759  <front>
2760    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2761    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2762      <organization>Harvard University</organization>
2763      <address><email>sob@harvard.edu</email></address>
2764    </author>
2765    <date month="March" year="1997"/>
2766  </front>
2767  <seriesInfo name="BCP" value="14"/>
2768  <seriesInfo name="RFC" value="2119"/>
2769</reference>
2770
2771</references>
2772
2773<references title="Informative References">
2774
2775<reference anchor="Luo1998">
2776  <front>
2777    <title>Tunneling TCP based protocols through Web proxy servers</title>
2778    <author initials="A." surname="Luotonen" fullname="A. Luotonen">
2779      <organization/>
2780    </author>
2781    <date year="1998" month="August"/>
2782  </front>
2783  <seriesInfo name="Internet-Draft" value="draft-luotonen-web-proxy-tunneling-01"/>
2784</reference>
2785
2786<reference anchor="RFC1945">
2787  <front>
2788    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2789    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2790      <organization>MIT, Laboratory for Computer Science</organization>
2791      <address><email>timbl@w3.org</email></address>
2792    </author>
2793    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2794      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2795      <address><email>fielding@ics.uci.edu</email></address>
2796    </author>
2797    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2798      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2799      <address><email>frystyk@w3.org</email></address>
2800    </author>
2801    <date month="May" year="1996"/>
2802  </front>
2803  <seriesInfo name="RFC" value="1945"/>
2804</reference>
2805
2806<reference anchor="RFC2068">
2807  <front>
2808    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2809    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2810      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2811      <address><email>fielding@ics.uci.edu</email></address>
2812    </author>
2813    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2814      <organization>MIT Laboratory for Computer Science</organization>
2815      <address><email>jg@w3.org</email></address>
2816    </author>
2817    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2818      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2819      <address><email>mogul@wrl.dec.com</email></address>
2820    </author>
2821    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2822      <organization>MIT Laboratory for Computer Science</organization>
2823      <address><email>frystyk@w3.org</email></address>
2824    </author>
2825    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2826      <organization>MIT Laboratory for Computer Science</organization>
2827      <address><email>timbl@w3.org</email></address>
2828    </author>
2829    <date month="January" year="1997"/>
2830  </front>
2831  <seriesInfo name="RFC" value="2068"/>
2832</reference>
2833
2834<reference anchor="RFC2616">
2835  <front>
2836    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2837    <author initials="R." surname="Fielding" fullname="R. Fielding">
2838      <organization>University of California, Irvine</organization>
2839      <address><email>fielding@ics.uci.edu</email></address>
2840    </author>
2841    <author initials="J." surname="Gettys" fullname="J. Gettys">
2842      <organization>W3C</organization>
2843      <address><email>jg@w3.org</email></address>
2844    </author>
2845    <author initials="J." surname="Mogul" fullname="J. Mogul">
2846      <organization>Compaq Computer Corporation</organization>
2847      <address><email>mogul@wrl.dec.com</email></address>
2848    </author>
2849    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2850      <organization>MIT Laboratory for Computer Science</organization>
2851      <address><email>frystyk@w3.org</email></address>
2852    </author>
2853    <author initials="L." surname="Masinter" fullname="L. Masinter">
2854      <organization>Xerox Corporation</organization>
2855      <address><email>masinter@parc.xerox.com</email></address>
2856    </author>
2857    <author initials="P." surname="Leach" fullname="P. Leach">
2858      <organization>Microsoft Corporation</organization>
2859      <address><email>paulle@microsoft.com</email></address>
2860    </author>
2861    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2862      <organization>W3C</organization>
2863      <address><email>timbl@w3.org</email></address>
2864    </author>
2865    <date month="June" year="1999"/>
2866  </front>
2867  <seriesInfo name="RFC" value="2616"/>
2868</reference>
2869
2870<reference anchor="RFC2817">
2871  <front>
2872    <title>Upgrading to TLS Within HTTP/1.1</title>
2873    <author initials="R." surname="Khare" fullname="R. Khare">
2874      <organization>4K Associates / UC Irvine</organization>
2875      <address><email>rohit@4K-associates.com</email></address>
2876    </author>
2877    <author initials="S." surname="Lawrence" fullname="S. Lawrence">
2878      <organization>Agranat Systems, Inc.</organization>
2879      <address><email>lawrence@agranat.com</email></address>
2880    </author>
2881    <date year="2000" month="May"/>
2882  </front>
2883  <seriesInfo name="RFC" value="2817"/>
2884</reference>
2885
2886<reference anchor="RFC2822">
2887  <front>
2888    <title>Internet Message Format</title>
2889    <author initials="P." surname="Resnick" fullname="P. Resnick">
2890      <organization>QUALCOMM Incorporated</organization>
2891    </author>
2892    <date year="2001" month="April"/>
2893  </front> 
2894  <seriesInfo name="RFC" value="2822"/>
2895</reference>
2896
2897<reference anchor="RFC3864">
2898  <front>
2899    <title>Registration Procedures for Message Header Fields</title>
2900    <author initials="G." surname="Klyne" fullname="G. Klyne">
2901      <organization>Nine by Nine</organization>
2902      <address><email>GK-IETF@ninebynine.org</email></address>
2903    </author>
2904    <author initials="M." surname="Nottingham" fullname="M. Nottingham">
2905      <organization>BEA Systems</organization>
2906      <address><email>mnot@pobox.com</email></address>
2907    </author>
2908    <author initials="J." surname="Mogul" fullname="J. Mogul">
2909      <organization>HP Labs</organization>
2910      <address><email>JeffMogul@acm.org</email></address>
2911    </author>
2912    <date year="2004" month="September"/>
2913  </front>
2914  <seriesInfo name="BCP" value="90"/>
2915  <seriesInfo name="RFC" value="3864"/>
2916</reference>
2917
2918<reference anchor="RFC5226">
2919  <front>
2920    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
2921    <author initials="T." surname="Narten" fullname="T. Narten">
2922      <organization>IBM</organization>
2923      <address><email>narten@us.ibm.com</email></address>
2924    </author>
2925    <author initials="H." surname="Alvestrand" fullname="H. Alvestrand">
2926      <organization>Google</organization>
2927      <address><email>Harald@Alvestrand.no</email></address>
2928    </author>
2929    <date year="2008" month="May"/>
2930  </front>
2931  <seriesInfo name="BCP" value="26"/>
2932  <seriesInfo name="RFC" value="5226"/>
2933</reference>
2934
2935</references>
2936
2937<section title="Compatibility with Previous Versions" anchor="compatibility">
2938<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
2939<t>
2940   Clarified which error code should be used for inbound server failures
2941   (e.g. DNS failures). (<xref target="status.504"/>).
2942</t>
2943<t>
2944   201 (Created) had a race that required an Etag be sent when a resource is
2945   first created. (<xref target="status.201"/>).
2946</t>
2947<t>
2948   Rewrite of message transmission requirements to make it much harder
2949   for implementors to get it wrong, as the consequences of errors here
2950   can have significant impact on the Internet, and to deal with the
2951   following problems:
2952  <list style="numbers">
2953      <t>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
2954         this was incorrectly placing a requirement on the behavior of
2955         an implementation of a future version of HTTP/1.x</t>
2956
2957      <t>Made it clear that user-agents should retry requests, not
2958         "clients" in general.</t>
2959
2960      <t>Converted requirements for clients to ignore unexpected 100
2961         (Continue) responses, and for proxies to forward 100 responses,
2962         into a general requirement for 1xx responses.</t>
2963
2964      <t>Modified some TCP-specific language, to make it clearer that
2965         non-TCP transports are possible for HTTP.</t>
2966
2967      <t>Require that the origin server MUST NOT wait for the request
2968         body before it sends a required 100 (Continue) response.</t>
2969
2970      <t>Allow, rather than require, a server to omit 100 (Continue) if
2971         it has already seen some of the request body.</t>
2972
2973      <t>Allow servers to defend against denial-of-service attacks and
2974         broken clients.</t>
2975  </list>
2976</t>
2977<t>
2978   This change adds the Expect header and 417 status code.
2979</t>
2980<t>
2981   Clean up confusion between 403 and 404 responses. (Section <xref target="status.403" format="counter"/>,
2982   <xref target="status.404" format="counter"/>, and <xref target="status.410" format="counter"/>)
2983</t>
2984<t>
2985   The PATCH<iref item="PATCH method" primary="true"/><iref item="Methods" subitem="PATCH" primary="true"/>, LINK<iref item="LINK method" primary="true"/><iref item="Methods" subitem="LINK" primary="true"/>, UNLINK<iref item="UNLINK method" primary="true"/><iref item="Methods" subitem="UNLINK" primary="true"/> methods were defined but not commonly
2986   implemented in previous versions of this specification. See Section 19.6.1 of <xref target="RFC2068"/>.
2987</t>
2988</section>
2989
2990<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
2991<t>
2992  This document takes over the Status Code Registry, previously defined
2993  in Section 7.1 of <xref target="RFC2817"/>.
2994  (<xref target="status.code.registry"/>)
2995</t>
2996<t>
2997  Clarify definition of POST.
2998  (<xref target="POST"/>)
2999</t>
3000<t>
3001  Failed to consider that there are
3002  many other request methods that are safe to automatically redirect,
3003  and further that the user agent is able to make that determination
3004  based on the request method semantics.
3005  (Sections <xref format="counter" target="status.301"/>,
3006  <xref format="counter" target="status.302"/> and
3007  <xref format="counter" target="status.307"/>)
3008</t>
3009<t>
3010  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3011  It used to indicate that the requested resource must be accessed through the
3012  proxy given by the Location field. The Location field gave the URI of the
3013  proxy. The recipient was expected to repeat this single request via the proxy.
3014  (<xref target="status.305"/>)
3015</t>
3016<t>
3017  Reclassify Allow header as response header, removing the option to
3018  specify it in a PUT request.
3019  Relax the server requirement on the contents of the Allow header and
3020  remove requirement on clients to always trust the header value.
3021  (<xref target="header.allow"/>)
3022</t>
3023<t>
3024  Correct syntax of Location header to allow fragment,
3025  as referred symbol wasn't what was expected, and add some
3026  clarifications as to when it would not be appropriate.
3027  (<xref target="header.location"/>)
3028</t>
3029<t>
3030  In the description of the Server header, the Via field
3031  was described as a SHOULD. The requirement was and is stated
3032  correctly in the description of the Via header in Section 8.9 of <xref target="Part1"/>.
3033  (<xref target="header.server"/>)
3034</t>
3035</section>
3036
3037</section>
3038
3039<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3040
3041<section title="Since RFC2616">
3042<t>
3043  Extracted relevant partitions from <xref target="RFC2616"/>.
3044</t>
3045</section>
3046
3047<section title="Since draft-ietf-httpbis-p2-semantics-00">
3048<t>
3049  Closed issues:
3050  <list style="symbols"> 
3051    <t>
3052      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3053      "Via is a MUST"
3054      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3055    </t>
3056    <t>
3057      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3058      "Fragments allowed in Location"
3059      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3060    </t>
3061    <t>
3062      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3063      "Safe Methods vs Redirection"
3064      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3065    </t>
3066    <t>
3067      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3068      "Revise description of the POST method"
3069      (<eref target="http://purl.org/NET/http-errata#post"/>)
3070    </t>
3071    <t>
3072      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3073      "Normative and Informative references"
3074    </t>
3075    <t>
3076      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3077      "RFC2606 Compliance"
3078    </t>
3079    <t>
3080      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3081      "Informative references"
3082    </t>
3083    <t>
3084      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3085      "Redundant cross-references"
3086    </t>
3087  </list>
3088</t>
3089<t>
3090  Other changes:
3091  <list style="symbols"> 
3092    <t>
3093      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3094    </t>
3095  </list>
3096</t>
3097</section>
3098
3099<section title="Since draft-ietf-httpbis-p2-semantics-01">
3100<t>
3101  Closed issues:
3102  <list style="symbols"> 
3103    <t>
3104      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3105      "PUT side effects"
3106    </t>
3107    <t>
3108      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3109      "Duplicate Host header requirements"
3110    </t>
3111  </list>
3112</t>
3113<t>
3114  Ongoing work on ABNF conversion (<eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3115  <list style="symbols"> 
3116    <t>
3117      Move "Product Tokens" section (back) into Part 1, as "token" is used
3118      in the definition of the Upgrade header.
3119    </t>
3120    <t>
3121      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3122    </t>
3123    <t>
3124      Copy definition of delta-seconds from Part6 instead of referencing it.
3125    </t>
3126  </list>
3127</t>
3128</section>
3129
3130<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3131<t>
3132  Closed issues:
3133  <list style="symbols"> 
3134    <t>
3135      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3136      "Requiring Allow in 405 responses"
3137    </t>
3138    <t>
3139      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3140      "Status Code Registry"
3141    </t>
3142    <t>
3143      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3144      "Redirection vs. Location"
3145    </t>
3146    <t>
3147      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3148      "Cacheability of 303 response"
3149    </t>
3150    <t>
3151      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3152      "305 Use Proxy"
3153    </t>
3154    <t>
3155      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3156      "Classification for Allow header"
3157    </t>
3158    <t>
3159      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3160      "PUT - 'store under' vs 'store at'"
3161    </t>
3162  </list>
3163</t>
3164<t>
3165  Ongoing work on IANA Message Header Registration (<eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3166  <list style="symbols"> 
3167    <t>
3168      Reference RFC 3984, and update header registrations for headers defined
3169      in this document.
3170    </t>
3171  </list>
3172</t>
3173<t>
3174  Ongoing work on ABNF conversion (<eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3175  <list style="symbols"> 
3176    <t>
3177      Replace string literals when the string really is case-sensitive (method).
3178    </t>
3179  </list>
3180</t>
3181</section>
3182
3183</section>
3184
3185</back>
3186</rfc>
Note: See TracBrowser for help on using the repository browser.