source: draft-ietf-httpbis/latest/p2-semantics.xml @ 210

Last change on this file since 210 was 210, checked in by julian.reschke@…, 14 years ago

Move definition of "delta-seconds" into Part1; relates to #36.

  • Property svn:eol-style set to native
File size: 123.7 KB
1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns=''>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns=''>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns=''>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns=''>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns=''>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns=''>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns=''>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns=''>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns=''>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns=''>SHOULD NOT</bcp14>">
14  <!ENTITY ID-VERSION "latest">
15  <!ENTITY ID-MONTH "February">
16  <!ENTITY ID-YEAR "2008">
17  <!ENTITY messaging                  "<xref target='Part1' xmlns:x=''/>">
18  <!ENTITY payload                    "<xref target='Part3' xmlns:x=''/>">
19  <!ENTITY conditional                "<xref target='Part4' xmlns:x=''/>">
20  <!ENTITY range                      "<xref target='Part5' xmlns:x=''/>">
21  <!ENTITY caching                    "<xref target='Part6' xmlns:x=''/>">
22  <!ENTITY auth                       "<xref target='Part7' xmlns:x=''/>">
23  <!ENTITY content-negotiation        "<xref target='Part3' x:rel='#content.negotiation' xmlns:x=''/>">
24  <!ENTITY notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x=''/>">
25  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' xmlns:x=''/>">
26  <!ENTITY general-syntax             "<xref target='Part1' x:rel='#general.syntax' xmlns:x=''/>">
27  <!ENTITY uri                        "<xref target='Part1' x:rel='#uri' xmlns:x=''/>">
28  <!ENTITY full-date                  "<xref target='Part1' x:rel='' xmlns:x=''/>">
29  <!ENTITY time-spans                 "<xref target='Part1' x:rel='#time.spans' xmlns:x=''/>">
30  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x=''/>">
31  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x=''/>">
32  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x=''/>">
33  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x=''/>">
34  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x=''/>">
35  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x=''/>">
36  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x=''/>">
37  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x=''/>">
38  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x=''/>">
39  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x=''/>">
40  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x=''/>">
41  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x=''/>">
42  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x=''/>">
43  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x=''/>">
44  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x=''/>">
45  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x=''/>">
46  <!ENTITY header-host                "<xref target='Part1' x:rel='' xmlns:x=''/>">
47  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x=''/>">
48  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x=''/>">
49  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x=''/>">
50  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x=''/>">
51  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x=''/>">
52  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x=''/>">
53  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x=''/>">
54  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x=''/>">
55  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x=''/>">
56  <!ENTITY header-upgrade             "<xref target='Part5' x:rel='#header.range' xmlns:x=''/>">
57  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.upgrade' xmlns:x=''/>">
58  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x=''/>">
59  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x=''/>">
60  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x=''/>">
61  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x=''/>">
62  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x=''/>">
63  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x=''/>">
65<?rfc toc="yes" ?>
66<?rfc symrefs="yes" ?>
67<?rfc sortrefs="yes" ?>
68<?rfc compact="yes"?>
69<?rfc subcompact="no" ?>
70<?rfc linkmailto="no" ?>
71<?rfc editing="no" ?>
72<?rfc comments="yes"?>
73<?rfc inline="yes"?>
74<?rfc-ext allow-markup-in-artwork="yes" ?>
75<?rfc-ext include-references-in-index="yes" ?>
76<rfc obsoletes="2616" category="std"
77     ipr="full3978" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
78     xmlns:x=''>
81  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
83  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
84    <organization abbrev="Day Software">Day Software</organization>
85    <address>
86      <postal>
87        <street>23 Corporate Plaza DR, Suite 280</street>
88        <city>Newport Beach</city>
89        <region>CA</region>
90        <code>92660</code>
91        <country>USA</country>
92      </postal>
93      <phone>+1-949-706-5300</phone>
94      <facsimile>+1-949-706-5305</facsimile>
95      <email></email>
96      <uri></uri>
97    </address>
98  </author>
100  <author initials="J." surname="Gettys" fullname="Jim Gettys">
101    <organization>One Laptop per Child</organization>
102    <address>
103      <postal>
104        <street>21 Oak Knoll Road</street>
105        <city>Carlisle</city>
106        <region>MA</region>
107        <code>01741</code>
108        <country>USA</country>
109      </postal>
110      <email></email>
111      <uri></uri>
112    </address>
113  </author>
115  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
116    <organization abbrev="HP">Hewlett-Packard Company</organization>
117    <address>
118      <postal>
119        <street>HP Labs, Large Scale Systems Group</street>
120        <street>1501 Page Mill Road, MS 1177</street>
121        <city>Palo Alto</city>
122        <region>CA</region>
123        <code>94304</code>
124        <country>USA</country>
125      </postal>
126      <email></email>
127    </address>
128  </author>
130  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
131    <organization abbrev="Microsoft">Microsoft Corporation</organization>
132    <address>
133      <postal>
134        <street>1 Microsoft Way</street>
135        <city>Redmond</city>
136        <region>WA</region>
137        <code>98052</code>
138        <country>USA</country>
139      </postal>
140      <email></email>
141    </address>
142  </author>
144  <author initials="L." surname="Masinter" fullname="Larry Masinter">
145    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
146    <address>
147      <postal>
148        <street>345 Park Ave</street>
149        <city>San Jose</city>
150        <region>CA</region>
151        <code>95110</code>
152        <country>USA</country>
153      </postal>
154      <email></email>
155      <uri></uri>
156    </address>
157  </author>
159  <author initials="P." surname="Leach" fullname="Paul J. Leach">
160    <organization abbrev="Microsoft">Microsoft Corporation</organization>
161    <address>
162      <postal>
163        <street>1 Microsoft Way</street>
164        <city>Redmond</city>
165        <region>WA</region>
166        <code>98052</code>
167      </postal>
168      <email></email>
169    </address>
170  </author>
172  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
173    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
174    <address>
175      <postal>
176        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
177        <street>The Stata Center, Building 32</street>
178        <street>32 Vassar Street</street>
179        <city>Cambridge</city>
180        <region>MA</region>
181        <code>02139</code>
182        <country>USA</country>
183      </postal>
184      <email></email>
185      <uri></uri>
186    </address>
187  </author>
189  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
190    <organization abbrev="W3C">World Wide Web Consortium</organization>
191    <address>
192      <postal>
193        <street>W3C / ERCIM</street>
194        <street>2004, rte des Lucioles</street>
195        <city>Sophia-Antipolis</city>
196        <region>AM</region>
197        <code>06902</code>
198        <country>France</country>
199      </postal>
200      <email></email>
201      <uri></uri>
202    </address>
203  </author>
205  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
206    <organization abbrev="greenbytes">greenbytes GmbH</organization>
207    <address>
208      <postal>
209        <street>Hafenweg 16</street>
210        <city>Muenster</city><region>NW</region><code>48155</code>
211        <country>Germany</country>
212      </postal>
213      <phone>+49 251 2807760</phone>   
214      <facsimile>+49 251 2807761</facsimile>   
215      <email></email>       
216      <uri></uri>     
217    </address>
218  </author>
220  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
224   The Hypertext Transfer Protocol (HTTP) is an application-level
225   protocol for distributed, collaborative, hypermedia information
226   systems. HTTP has been in use by the World Wide Web global information
227   initiative since 1990. This document is Part 2 of the seven-part specification
228   that defines the protocol referred to as "HTTP/1.1" and, taken together,
229   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
230   as expressed by request methods, request-header fields, response status codes,
231   and response-header fields.
235<note title="Editorial Note (To be removed by RFC Editor)">
236  <t>
237    Discussion of this draft should take place on the HTTPBIS working group
238    mailing list ( The current issues list is
239    at <eref target=""/>
240    and related documents (including fancy diffs) can be found at
241    <eref target=""/>.
242  </t>
243  <t>
244    This draft incorporates those issue resolutions that were either
245    collected in the original RFC2616 errata list (<eref target=""/>),
246    or which were agreed upon on the mailing list between October 2006 and
247    November 2007 (as published in "draft-lafon-rfc2616bis-03").
248  </t>
252<section title="Introduction" anchor="introduction">
254   This document defines HTTP/1.1 request and response semantics.  Each HTTP
255   message, as defined in &messaging;, is in the form of either a request or
256   a response.  An HTTP server listens on a connection for HTTP requests and
257   responds to each request, in the order received on that connection, with
258   one or more HTTP response messages.  This document defines the commonly
259   agreed upon semantics of the HTTP uniform interface, the intentions defined
260   by each request method, and the various response messages that might be
261   expected as a result of applying that method for the requested resource.
264   This document is currently disorganized in order to minimize the changes
265   between drafts and enable reviewers to see the smaller errata changes.
266   The next draft will reorganize the sections to better reflect the content.
267   In particular, the sections will be ordered according to the typical
268   processing of an HTTP request message (after message parsing): resource
269   mapping, general header fields, methods, request modifiers, response
270   status, and resource metadata.  The current mess reflects how widely
271   dispersed these topics and associated requirements had become in
272   <xref target="RFC2616"/>.
275<section title="Requirements" anchor="intro.requirements">
277   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
278   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
279   document are to be interpreted as described in <xref target="RFC2119"/>.
282   An implementation is not compliant if it fails to satisfy one or more
283   of the &MUST; or &REQUIRED; level requirements for the protocols it
284   implements. An implementation that satisfies all the &MUST; or &REQUIRED;
285   level and all the &SHOULD; level requirements for its protocols is said
286   to be "unconditionally compliant"; one that satisfies all the &MUST;
287   level requirements but not all the &SHOULD; level requirements for its
288   protocols is said to be "conditionally compliant."
293<section title="Notational Conventions and Generic Grammar" anchor="notation">
295  This specification uses the ABNF syntax defined in &notation-abnf; and
296  the core rules defined in &basic-rules;:
297  <cref anchor="abnf.dep">ABNF syntax and basic rules will be adopted from RFC 5234, see
298  <eref target=""/>.</cref>
300<figure><artwork type="abnf2616">
301  DIGIT         = &lt;DIGIT, defined in &basic-rules;&gt;
303<figure><artwork type="abnf2616">
304  comment       = &lt;comment, defined in &basic-rules;&gt;
305  quoted-string = &lt;quoted-string, defined in &basic-rules;&gt;
306  token         = &lt;token, defined in &basic-rules;&gt;
308<t anchor="abnf.dependencies">
309  The ABNF rules below are defined in other parts:
311<figure><!--Part1--><artwork type="abnf2616">
312  absoluteURI   = &lt;absoluteURI, defined in &general-syntax;&gt;
313  delta-seconds = &lt;delta-seconds, defined in &time-spans;&gt;
314  fragment      = &lt;fragment, defined in &general-syntax;&gt;
315  Host          = &lt;Host, defined in &header-host;&gt;
316  HTTP-date     = &lt;HTTP-date, defined in &full-date;&gt;
317  product       = &lt;product, defined in &product-tokens;&gt;
318  relativeURI   = &lt;relativeURI, defined in &general-syntax;&gt;
319  TE            = &lt;TE, defined in &header-te;&gt;
321<figure><!--Part3--><artwork type="abnf2616">
322  Accept        = &lt;Accept, defined in &header-accept;&gt;
323  Accept-Charset =
324             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
325  Accept-Encoding =
326             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
327  Accept-Language =
328             &lt;Accept-Language, defined in &header-accept-language;&gt;
330<figure><!--Part4--><artwork type="abnf2616">
331  ETag          = &lt;ETag, defined in &header-etag;&gt;
332  If-Match      = &lt;If-Match, defined in &header-if-match;&gt;
333  If-Modified-Since =
334             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
335  If-None-Match = &lt;If-None-Match, defined in &header-if-none-match;&gt;
336  If-Unmodified-Since =
337             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
339<figure><!--Part5--><artwork type="abnf2616">
340  Accept-Ranges = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
341  If-Range      = &lt;If-Range, defined in &header-if-range;&gt;
342  Range         = &lt;Range, defined in &header-range;&gt;
344<figure><!--Part6--><artwork type="abnf2616">
345  Age           = &lt;Age, defined in &header-age;&gt;
346  Vary          = &lt;Vary, defined in &header-vary;&gt;
348<figure><artwork type="abnf2616">
349  Authorization = &lt;Authorization, defined in &header-authorization;&gt;
350  Proxy-Authenticate =
351             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
352  Proxy-Authorization =
353             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
354  WWW-Authenticate =
355             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
359<section title="Method" anchor="method">
361   The Method  token indicates the method to be performed on the
362   resource identified by the Request-URI. The method is case-sensitive.
364<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
365  Method         = "OPTIONS"                ; <xref target="OPTIONS"/>
366                 | "GET"                    ; <xref target="GET"/>
367                 | "HEAD"                   ; <xref target="HEAD"/>
368                 | "POST"                   ; <xref target="POST"/>
369                 | "PUT"                    ; <xref target="PUT"/>
370                 | "DELETE"                 ; <xref target="DELETE"/>
371                 | "TRACE"                  ; <xref target="TRACE"/>
372                 | "CONNECT"                ; <xref target="CONNECT"/>
373                 | extension-method
374  extension-method = token
377   The list of methods allowed by a resource can be specified in an
378   Allow header field (<xref target="header.allow"/>). The return code of the response
379   always notifies the client whether a method is currently allowed on a
380   resource, since the set of allowed methods can change dynamically. An
381   origin server &SHOULD; return the status code 405 (Method Not Allowed)
382   if the method is known by the origin server but not allowed for the
383   requested resource, and 501 (Not Implemented) if the method is
384   unrecognized or not implemented by the origin server. The methods GET
385   and HEAD &MUST; be supported by all general-purpose servers. All other
386   methods are &OPTIONAL;; however, if the above methods are implemented,
387   they &MUST; be implemented with the same semantics as those specified
388   in <xref target="method.definitions"/>.
392<section title="Request Header Fields" anchor="request.header.fields">
394   The request-header fields allow the client to pass additional
395   information about the request, and about the client itself, to the
396   server. These fields act as request modifiers, with semantics
397   equivalent to the parameters on a programming language method
398   invocation.
400<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
401  request-header = Accept                   ; &header-accept;
402                 | Accept-Charset           ; &header-accept-charset;
403                 | Accept-Encoding          ; &header-accept-encoding;
404                 | Accept-Language          ; &header-accept-language;
405                 | Authorization            ; &header-authorization;
406                 | Expect                   ; <xref target="header.expect"/>
407                 | From                     ; <xref target="header.from"/>
408                 | Host                     ; &header-host;
409                 | If-Match                 ; &header-if-match;
410                 | If-Modified-Since        ; &header-if-modified-since;
411                 | If-None-Match            ; &header-if-none-match;
412                 | If-Range                 ; &header-if-range;
413                 | If-Unmodified-Since      ; &header-if-unmodified-since;
414                 | Max-Forwards             ; <xref target="header.max-forwards"/>
415                 | Proxy-Authorization      ; &header-proxy-authorization;
416                 | Range                    ; &header-range;
417                 | Referer                  ; <xref target="header.referer"/>
418                 | TE                       ; &header-te;
419                 | User-Agent               ; <xref target="header.user-agent"/>
422   Request-header field names can be extended reliably only in
423   combination with a change in the protocol version. However, new or
424   experimental header fields &MAY; be given the semantics of request-header
425   fields if all parties in the communication recognize them to
426   be request-header fields. Unrecognized header fields are treated as
427   entity-header fields.
431<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
433   The Status-Code element is a 3-digit integer result code of the
434   attempt to understand and satisfy the request. The status codes listed
435   below are defined in <xref target=""/>.
436   The Reason-Phrase is intended to give a short
437   textual description of the Status-Code. The Status-Code is intended
438   for use by automata and the Reason-Phrase is intended for the human
439   user. The client is not required to examine or display the Reason-Phrase.
442   The individual values of the numeric status codes defined for
443   HTTP/1.1, and an example set of corresponding Reason-Phrase's, are
444   presented below. The reason phrases listed here are only
445   recommendations -- they &MAY; be replaced by local equivalents without
446   affecting the protocol.
448<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Status-Code"/><iref primary="true" item="Grammar" subitem="extension-code"/><iref primary="true" item="Grammar" subitem="Reason-Phrase"/>
449  Status-Code    =
450         "100"  ; <xref target="status.100"/>: Continue
451       | "101"  ; <xref target="status.101"/>: Switching Protocols
452       | "200"  ; <xref target="status.200"/>: OK
453       | "201"  ; <xref target="status.201"/>: Created
454       | "202"  ; <xref target="status.202"/>: Accepted
455       | "203"  ; <xref target="status.203"/>: Non-Authoritative Information
456       | "204"  ; <xref target="status.204"/>: No Content
457       | "205"  ; <xref target="status.205"/>: Reset Content
458       | "206"  ; <xref target="status.206"/>: Partial Content
459       | "300"  ; <xref target="status.300"/>: Multiple Choices
460       | "301"  ; <xref target="status.301"/>: Moved Permanently
461       | "302"  ; <xref target="status.302"/>: Found
462       | "303"  ; <xref target="status.303"/>: See Other
463       | "304"  ; <xref target="status.304"/>: Not Modified
464       | "305"  ; <xref target="status.305"/>: Use Proxy
465       | "307"  ; <xref target="status.307"/>: Temporary Redirect
466       | "400"  ; <xref target="status.400"/>: Bad Request
467       | "401"  ; <xref target="status.401"/>: Unauthorized
468       | "402"  ; <xref target="status.402"/>: Payment Required
469       | "403"  ; <xref target="status.403"/>: Forbidden
470       | "404"  ; <xref target="status.404"/>: Not Found
471       | "405"  ; <xref target="status.405"/>: Method Not Allowed
472       | "406"  ; <xref target="status.406"/>: Not Acceptable
473       | "407"  ; <xref target="status.407"/>: Proxy Authentication Required
474       | "408"  ; <xref target="status.408"/>: Request Time-out
475       | "409"  ; <xref target="status.409"/>: Conflict
476       | "410"  ; <xref target="status.410"/>: Gone
477       | "411"  ; <xref target="status.411"/>: Length Required
478       | "412"  ; <xref target="status.412"/>: Precondition Failed
479       | "413"  ; <xref target="status.413"/>: Request Entity Too Large
480       | "414"  ; <xref target="status.414"/>: Request-URI Too Large
481       | "415"  ; <xref target="status.415"/>: Unsupported Media Type
482       | "416"  ; <xref target="status.416"/>: Requested range not satisfiable
483       | "417"  ; <xref target="status.417"/>: Expectation Failed
484       | "500"  ; <xref target="status.500"/>: Internal Server Error
485       | "501"  ; <xref target="status.501"/>: Not Implemented
486       | "502"  ; <xref target="status.502"/>: Bad Gateway
487       | "503"  ; <xref target="status.503"/>: Service Unavailable
488       | "504"  ; <xref target="status.504"/>: Gateway Time-out
489       | "505"  ; <xref target="status.505"/>: HTTP Version not supported
490       | extension-code
492  extension-code = 3DIGIT
493  Reason-Phrase  = *&lt;TEXT, excluding CR, LF&gt;
496   HTTP status codes are extensible. HTTP applications are not required
497   to understand the meaning of all registered status codes, though such
498   understanding is obviously desirable. However, applications &MUST;
499   understand the class of any status code, as indicated by the first
500   digit, and treat any unrecognized response as being equivalent to the
501   x00 status code of that class, with the exception that an
502   unrecognized response &MUST-NOT; be cached. For example, if an
503   unrecognized status code of 431 is received by the client, it can
504   safely assume that there was something wrong with its request and
505   treat the response as if it had received a 400 status code. In such
506   cases, user agents &SHOULD; present to the user the entity returned
507   with the response, since that entity is likely to include human-readable
508   information which will explain the unusual status.
512<section title="Response Header Fields" anchor="response.header.fields">
514   The response-header fields allow the server to pass additional
515   information about the response which cannot be placed in the Status-Line.
516   These header fields give information about the server and about
517   further access to the resource identified by the Request-URI.
519<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
520  response-header = Accept-Ranges           ; &header-accept-ranges;
521                  | Age                     ; &header-age;
522                  | ETag                    ; &header-etag;
523                  | Location                ; <xref target="header.location"/>
524                  | Proxy-Authenticate      ; &header-proxy-authenticate;
525                  | Retry-After             ; <xref target="header.retry-after"/>
526                  | Server                  ; <xref target="header.server"/>
527                  | Vary                    ; &header-vary;
528                  | WWW-Authenticate        ; &header-www-authenticate;
531   Response-header field names can be extended reliably only in
532   combination with a change in the protocol version. However, new or
533   experimental header fields &MAY; be given the semantics of response-header
534   fields if all parties in the communication recognize them to
535   be response-header fields. Unrecognized header fields are treated as
536   entity-header fields.
540<section title="Entity" anchor="entity">
542   Request and Response messages &MAY; transfer an entity if not otherwise
543   restricted by the request method or response status code. An entity
544   consists of entity-header fields and an entity-body, although some
545   responses will only include the entity-headers. HTTP entity-body and
546   entity-header fields are defined in &payload;.
549   An entity-body is only present in a message when a message-body is
550   present, as described in &message-body;. The entity-body is obtained
551   from the message-body by decoding any Transfer-Encoding that might
552   have been applied to ensure safe and proper transfer of the message.
557<section title="Method Definitions" anchor="method.definitions">
559   The set of common methods for HTTP/1.1 is defined below. Although
560   this set can be expanded, additional methods cannot be assumed to
561   share the same semantics for separately extended clients and servers.
564<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
566<section title="Safe Methods" anchor="safe.methods">
568   Implementors should be aware that the software represents the user in
569   their interactions over the Internet, and should be careful to allow
570   the user to be aware of any actions they might take which may have an
571   unexpected significance to themselves or others.
574   In particular, the convention has been established that the GET and
575   HEAD methods &SHOULD-NOT;  have the significance of taking an action
576   other than retrieval. These methods ought to be considered "safe".
577   This allows user agents to represent other methods, such as POST, PUT
578   and DELETE, in a special way, so that the user is made aware of the
579   fact that a possibly unsafe action is being requested.
582   Naturally, it is not possible to ensure that the server does not
583   generate side-effects as a result of performing a GET request; in
584   fact, some dynamic resources consider that a feature. The important
585   distinction here is that the user did not request the side-effects,
586   so therefore cannot be held accountable for them.
590<section title="Idempotent Methods" anchor="idempotent.methods">
592   Methods can also have the property of "idempotence" in that (aside
593   from error or expiration issues) the side-effects of N &gt; 0 identical
594   requests is the same as for a single request. The methods GET, HEAD,
595   PUT and DELETE share this property. Also, the methods OPTIONS and
596   TRACE &SHOULD-NOT;  have side effects, and so are inherently idempotent.
599   However, it is possible that a sequence of several requests is non-idempotent,
600   even if all of the methods executed in that sequence are
601   idempotent. (A sequence is idempotent if a single execution of the
602   entire sequence always yields a result that is not changed by a
603   reexecution of all, or part, of that sequence.) For example, a
604   sequence is non-idempotent if its result depends on a value that is
605   later modified in the same sequence.
608   A sequence that never has side effects is idempotent, by definition
609   (provided that no concurrent operations are being executed on the
610   same set of resources).
615<section title="OPTIONS" anchor="OPTIONS">
616  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
617  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
619   The OPTIONS method represents a request for information about the
620   communication options available on the request/response chain
621   identified by the Request-URI. This method allows the client to
622   determine the options and/or requirements associated with a resource,
623   or the capabilities of a server, without implying a resource action
624   or initiating a resource retrieval.
627   Responses to this method are not cacheable.
630   If the OPTIONS request includes an entity-body (as indicated by the
631   presence of Content-Length or Transfer-Encoding), then the media type
632   &MUST; be indicated by a Content-Type field. Although this
633   specification does not define any use for such a body, future
634   extensions to HTTP might use the OPTIONS body to make more detailed
635   queries on the server. A server that does not support such an
636   extension &MAY; discard the request body.
639   If the Request-URI is an asterisk ("*"), the OPTIONS request is
640   intended to apply to the server in general rather than to a specific
641   resource. Since a server's communication options typically depend on
642   the resource, the "*" request is only useful as a "ping" or "no-op"
643   type of method; it does nothing beyond allowing the client to test
644   the capabilities of the server. For example, this can be used to test
645   a proxy for HTTP/1.1 compliance (or lack thereof).
648   If the Request-URI is not an asterisk, the OPTIONS request applies
649   only to the options that are available when communicating with that
650   resource.
653   A 200 response &SHOULD; include any header fields that indicate
654   optional features implemented by the server and applicable to that
655   resource (e.g., Allow), possibly including extensions not defined by
656   this specification. The response body, if any, &SHOULD; also include
657   information about the communication options. The format for such a
658   body is not defined by this specification, but might be defined by
659   future extensions to HTTP. Content negotiation &MAY; be used to select
660   the appropriate response format. If no response body is included, the
661   response &MUST; include a Content-Length field with a field-value of
662   "0".
665   The Max-Forwards request-header field &MAY; be used to target a
666   specific proxy in the request chain. When a proxy receives an OPTIONS
667   request on an absoluteURI for which request forwarding is permitted,
668   the proxy &MUST; check for a Max-Forwards field. If the Max-Forwards
669   field-value is zero ("0"), the proxy &MUST-NOT; forward the message;
670   instead, the proxy &SHOULD; respond with its own communication options.
671   If the Max-Forwards field-value is an integer greater than zero, the
672   proxy &MUST; decrement the field-value when it forwards the request. If
673   no Max-Forwards field is present in the request, then the forwarded
674   request &MUST-NOT; include a Max-Forwards field.
678<section title="GET" anchor="GET">
679  <iref primary="true" item="GET method" x:for-anchor=""/>
680  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
682   The GET method means retrieve whatever information (in the form of an
683   entity) is identified by the Request-URI. If the Request-URI refers
684   to a data-producing process, it is the produced data which shall be
685   returned as the entity in the response and not the source text of the
686   process, unless that text happens to be the output of the process.
689   The semantics of the GET method change to a "conditional GET" if the
690   request message includes an If-Modified-Since, If-Unmodified-Since,
691   If-Match, If-None-Match, or If-Range header field. A conditional GET
692   method requests that the entity be transferred only under the
693   circumstances described by the conditional header field(s). The
694   conditional GET method is intended to reduce unnecessary network
695   usage by allowing cached entities to be refreshed without requiring
696   multiple requests or transferring data already held by the client.
699   The semantics of the GET method change to a "partial GET" if the
700   request message includes a Range header field. A partial GET requests
701   that only part of the entity be transferred, as described in &header-range;.
702   The partial GET method is intended to reduce unnecessary
703   network usage by allowing partially-retrieved entities to be
704   completed without transferring data already held by the client.
707   The response to a GET request is cacheable if and only if it meets
708   the requirements for HTTP caching described in &caching;.
711   See <xref target=""/> for security considerations when used for forms.
715<section title="HEAD" anchor="HEAD">
716  <iref primary="true" item="HEAD method" x:for-anchor=""/>
717  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
719   The HEAD method is identical to GET except that the server &MUST-NOT;
720   return a message-body in the response. The metainformation contained
721   in the HTTP headers in response to a HEAD request &SHOULD; be identical
722   to the information sent in response to a GET request. This method can
723   be used for obtaining metainformation about the entity implied by the
724   request without transferring the entity-body itself. This method is
725   often used for testing hypertext links for validity, accessibility,
726   and recent modification.
729   The response to a HEAD request &MAY; be cacheable in the sense that the
730   information contained in the response &MAY; be used to update a
731   previously cached entity from that resource. If the new field values
732   indicate that the cached entity differs from the current entity (as
733   would be indicated by a change in Content-Length, Content-MD5, ETag
734   or Last-Modified), then the cache &MUST; treat the cache entry as
735   stale.
739<section title="POST" anchor="POST">
740  <iref primary="true" item="POST method" x:for-anchor=""/>
741  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
743   The POST method is used to request that the origin server accept the
744   entity enclosed in the request as data to be processed by the resource
745   identified by the Request-URI in the Request-Line. POST is designed
746   to allow a uniform method to cover the following functions:
747  <list style="symbols">
748    <t>
749      Annotation of existing resources;
750    </t>
751    <t>
752        Posting a message to a bulletin board, newsgroup, mailing list,
753        or similar group of articles;
754    </t>
755    <t>
756        Providing a block of data, such as the result of submitting a
757        form, to a data-handling process;
758    </t>
759    <t>
760        Extending a database through an append operation.
761    </t>
762  </list>
765   The actual function performed by the POST method is determined by the
766   server and is usually dependent on the Request-URI.
769   The action performed by the POST method might not result in a
770   resource that can be identified by a URI. In this case, either 200
771   (OK) or 204 (No Content) is the appropriate response status,
772   depending on whether or not the response includes an entity that
773   describes the result.
776   If a resource has been created on the origin server, the response
777   &SHOULD; be 201 (Created) and contain an entity which describes the
778   status of the request and refers to the new resource, and a Location
779   header (see <xref target="header.location"/>).
782   Responses to this method are not cacheable, unless the response
783   includes appropriate Cache-Control or Expires header fields. However,
784   the 303 (See Other) response can be used to direct the user agent to
785   retrieve a cacheable resource.
789<section title="PUT" anchor="PUT">
790  <iref primary="true" item="PUT method" x:for-anchor=""/>
791  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
793   The PUT method requests that the enclosed entity be stored under the
794   supplied Request-URI. If the Request-URI refers to an already
795   existing resource, the enclosed entity &SHOULD; be considered as a
796   modified version of the one residing on the origin server. If the
797   Request-URI does not point to an existing resource, and that URI is
798   capable of being defined as a new resource by the requesting user
799   agent, the origin server can create the resource with that URI. If a
800   new resource is created at the Request-URI, the origin server &MUST;
801         inform the user agent
802   via the 201 (Created) response. If an existing resource is modified,
803   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
804   to indicate successful completion of the request. If the resource
805   could not be created or modified with the Request-URI, an appropriate
806   error response &SHOULD; be given that reflects the nature of the
807   problem. The recipient of the entity &MUST-NOT; ignore any Content-*
808   (e.g. Content-Range) headers that it does not understand or implement
809   and &MUST; return a 501 (Not Implemented) response in such cases.
812   If the request passes through a cache and the Request-URI identifies
813   one or more currently cached entities, those entries &SHOULD; be
814   treated as stale. Responses to this method are not cacheable.
817   The fundamental difference between the POST and PUT requests is
818   reflected in the different meaning of the Request-URI. The URI in a
819   POST request identifies the resource that will handle the enclosed
820   entity. That resource might be a data-accepting process, a gateway to
821   some other protocol, or a separate entity that accepts annotations.
822   In contrast, the URI in a PUT request identifies the entity enclosed
823   with the request -- the user agent knows what URI is intended and the
824   server &MUST-NOT; attempt to apply the request to some other resource.
825   If the server desires that the request be applied to a different URI,
826   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
827   then make its own decision regarding whether or not to redirect the
828   request.
831   A single resource &MAY; be identified by many different URIs. For
832   example, an article might have a URI for identifying "the current
833   version" which is separate from the URI identifying each particular
834   version. In this case, a PUT request on a general URI might result in
835   several other URIs being defined by the origin server.
838   HTTP/1.1 does not define how a PUT method affects the state of an
839   origin server.
842   Unless otherwise specified for a particular entity-header, the
843   entity-headers in the PUT request &SHOULD; be applied to the resource
844   created or modified by the PUT.
848<section title="DELETE" anchor="DELETE">
849  <iref primary="true" item="DELETE method" x:for-anchor=""/>
850  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
852   The DELETE method requests that the origin server delete the resource
853   identified by the Request-URI. This method &MAY; be overridden by human
854   intervention (or other means) on the origin server. The client cannot
855   be guaranteed that the operation has been carried out, even if the
856   status code returned from the origin server indicates that the action
857   has been completed successfully. However, the server &SHOULD-NOT;
858   indicate success unless, at the time the response is given, it
859   intends to delete the resource or move it to an inaccessible
860   location.
863   A successful response &SHOULD; be 200 (OK) if the response includes an
864   entity describing the status, 202 (Accepted) if the action has not
865   yet been enacted, or 204 (No Content) if the action has been enacted
866   but the response does not include an entity.
869   If the request passes through a cache and the Request-URI identifies
870   one or more currently cached entities, those entries &SHOULD; be
871   treated as stale. Responses to this method are not cacheable.
875<section title="TRACE" anchor="TRACE">
876  <iref primary="true" item="TRACE method" x:for-anchor=""/>
877  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
879   The TRACE method is used to invoke a remote, application-layer loop-back
880   of the request message. The final recipient of the request
881   &SHOULD; reflect the message received back to the client as the
882   entity-body of a 200 (OK) response. The final recipient is either the
883   origin server or the first proxy or gateway to receive a Max-Forwards
884   value of zero (0) in the request (see <xref target="header.max-forwards"/>). A TRACE request
885   &MUST-NOT; include an entity.
888   TRACE allows the client to see what is being received at the other
889   end of the request chain and use that data for testing or diagnostic
890   information. The value of the Via header field (&header-via;) is of
891   particular interest, since it acts as a trace of the request chain.
892   Use of the Max-Forwards header field allows the client to limit the
893   length of the request chain, which is useful for testing a chain of
894   proxies forwarding messages in an infinite loop.
897   If the request is valid, the response &SHOULD; contain the entire
898   request message in the entity-body, with a Content-Type of
899   "message/http". Responses to this method &MUST-NOT; be cached.
903<section title="CONNECT" anchor="CONNECT">
904  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
905  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
907   This specification reserves the method name CONNECT for use with a
908   proxy that can dynamically switch to being a tunnel (e.g. SSL
909   tunneling <xref target="Luo1998"/>).
915<section title="Status Code Definitions" anchor="">
917   Each Status-Code is described below, including a description of which
918   method(s) it can follow and any metainformation required in the
919   response.
922<section title="Informational 1xx" anchor="status.1xx">
924   This class of status code indicates a provisional response,
925   consisting only of the Status-Line and optional headers, and is
926   terminated by an empty line. There are no required headers for this
927   class of status code. Since HTTP/1.0 did not define any 1xx status
928   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
929   except under experimental conditions.
932   A client &MUST; be prepared to accept one or more 1xx status responses
933   prior to a regular response, even if the client does not expect a 100
934   (Continue) status message. Unexpected 1xx status responses &MAY; be
935   ignored by a user agent.
938   Proxies &MUST; forward 1xx responses, unless the connection between the
939   proxy and its client has been closed, or unless the proxy itself
940   requested the generation of the 1xx response. (For example, if a
941   proxy adds a "Expect: 100-continue" field when it forwards a request,
942   then it need not forward the corresponding 100 (Continue)
943   response(s).)
946<section title="100 Continue" anchor="status.100">
947  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
948  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
950   The client &SHOULD; continue with its request. This interim response is
951   used to inform the client that the initial part of the request has
952   been received and has not yet been rejected by the server. The client
953   &SHOULD; continue by sending the remainder of the request or, if the
954   request has already been completed, ignore this response. The server
955   &MUST; send a final response after the request has been completed. See
956   &use100; for detailed discussion of the use and handling of this
957   status code.
961<section title="101 Switching Protocols" anchor="status.101">
962  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
963  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
965   The server understands and is willing to comply with the client's
966   request, via the Upgrade message header field (&header-upgrade;), for a
967   change in the application protocol being used on this connection. The
968   server will switch protocols to those defined by the response's
969   Upgrade header field immediately after the empty line which
970   terminates the 101 response.
973   The protocol &SHOULD; be switched only when it is advantageous to do
974   so. For example, switching to a newer version of HTTP is advantageous
975   over older versions, and switching to a real-time, synchronous
976   protocol might be advantageous when delivering resources that use
977   such features.
982<section title="Successful 2xx" anchor="status.2xx">
984   This class of status code indicates that the client's request was
985   successfully received, understood, and accepted.
988<section title="200 OK" anchor="status.200">
989  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
990  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
992   The request has succeeded. The information returned with the response
993   is dependent on the method used in the request, for example:
994  <list style="hanging">
995    <t hangText="GET">
996          an entity corresponding to the requested resource is sent in
997          the response;
998    </t>
999    <t hangText="HEAD">
1000          the entity-header fields corresponding to the requested
1001          resource are sent in the response without any message-body;
1002    </t>
1003    <t hangText="POST">
1004      an entity describing or containing the result of the action;
1005    </t>
1006    <t hangText="TRACE">
1007      an entity containing the request message as received by the
1008      end server.
1009    </t>
1010  </list>
1014<section title="201 Created" anchor="status.201">
1015  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1016  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1018   The request has been fulfilled and resulted in a new resource being
1019   created. The newly created resource can be referenced by the URI(s)
1020   returned in the entity of the response, with the most specific URI
1021   for the resource given by a Location header field. The response
1022   &SHOULD; include an entity containing a list of resource
1023   characteristics and location(s) from which the user or user agent can
1024   choose the one most appropriate. The entity format is specified by
1025   the media type given in the Content-Type header field. The origin
1026   server &MUST; create the resource before returning the 201 status code.
1027   If the action cannot be carried out immediately, the server &SHOULD;
1028   respond with 202 (Accepted) response instead.
1031   A 201 response &MAY; contain an ETag response header field indicating
1032   the current value of the entity tag for the requested variant just
1033   created, see &header-etag;.
1037<section title="202 Accepted" anchor="status.202">
1038  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1039  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1041   The request has been accepted for processing, but the processing has
1042   not been completed.  The request might or might not eventually be
1043   acted upon, as it might be disallowed when processing actually takes
1044   place. There is no facility for re-sending a status code from an
1045   asynchronous operation such as this.
1048   The 202 response is intentionally non-committal. Its purpose is to
1049   allow a server to accept a request for some other process (perhaps a
1050   batch-oriented process that is only run once per day) without
1051   requiring that the user agent's connection to the server persist
1052   until the process is completed. The entity returned with this
1053   response &SHOULD; include an indication of the request's current status
1054   and either a pointer to a status monitor or some estimate of when the
1055   user can expect the request to be fulfilled.
1059<section title="203 Non-Authoritative Information" anchor="status.203">
1060  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1061  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1063   The returned metainformation in the entity-header is not the
1064   definitive set as available from the origin server, but is gathered
1065   from a local or a third-party copy. The set presented &MAY; be a subset
1066   or superset of the original version. For example, including local
1067   annotation information about the resource might result in a superset
1068   of the metainformation known by the origin server. Use of this
1069   response code is not required and is only appropriate when the
1070   response would otherwise be 200 (OK).
1074<section title="204 No Content" anchor="status.204">
1075  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1076  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1078   The server has fulfilled the request but does not need to return an
1079   entity-body, and might want to return updated metainformation. The
1080   response &MAY; include new or updated metainformation in the form of
1081   entity-headers, which if present &SHOULD; be associated with the
1082   requested variant.
1085   If the client is a user agent, it &SHOULD-NOT;  change its document view
1086   from that which caused the request to be sent. This response is
1087   primarily intended to allow input for actions to take place without
1088   causing a change to the user agent's active document view, although
1089   any new or updated metainformation &SHOULD; be applied to the document
1090   currently in the user agent's active view.
1093   The 204 response &MUST-NOT; include a message-body, and thus is always
1094   terminated by the first empty line after the header fields.
1098<section title="205 Reset Content" anchor="status.205">
1099  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1100  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1102   The server has fulfilled the request and the user agent &SHOULD; reset
1103   the document view which caused the request to be sent. This response
1104   is primarily intended to allow input for actions to take place via
1105   user input, followed by a clearing of the form in which the input is
1106   given so that the user can easily initiate another input action. The
1107   response &MUST-NOT; include an entity.
1111<section title="206 Partial Content" anchor="status.206">
1112  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1113  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1115   The server has fulfilled the partial GET request for the resource
1116   and the enclosed entity is a partial representation as defined in &range;.
1121<section title="Redirection 3xx" anchor="status.3xx">
1123   This class of status code indicates that further action needs to be
1124   taken by the user agent in order to fulfill the request.  The action
1125   required &MAY; be carried out by the user agent without interaction
1126   with the user if and only if the method used in the second request is
1127   GET or HEAD. A client &SHOULD; detect infinite redirection loops, since
1128   such loops generate network traffic for each redirection.
1129  <list><t>
1130      <x:h>Note:</x:h> previous versions of this specification recommended a
1131      maximum of five redirections. Content developers should be aware
1132      that there might be clients that implement such a fixed
1133      limitation.
1134  </t></list>
1137<section title="300 Multiple Choices" anchor="status.300">
1138  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1139  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1141   The requested resource corresponds to any one of a set of
1142   representations, each with its own specific location, and agent-driven
1143   negotiation information (&content-negotiation;) is being provided so that
1144   the user (or user agent) can select a preferred representation and
1145   redirect its request to that location.
1148   Unless it was a HEAD request, the response &SHOULD; include an entity
1149   containing a list of resource characteristics and location(s) from
1150   which the user or user agent can choose the one most appropriate. The
1151   entity format is specified by the media type given in the Content-Type
1152   header field. Depending upon the format and the capabilities of
1153   the user agent, selection of the most appropriate choice &MAY; be
1154   performed automatically. However, this specification does not define
1155   any standard for such automatic selection.
1158   If the server has a preferred choice of representation, it &SHOULD;
1159   include the specific URI for that representation in the Location
1160   field; user agents &MAY; use the Location field value for automatic
1161   redirection. This response is cacheable unless indicated otherwise.
1165<section title="301 Moved Permanently" anchor="status.301">
1166  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1167  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1169   The requested resource has been assigned a new permanent URI and any
1170   future references to this resource &SHOULD; use one of the returned
1171   URIs.  Clients with link editing capabilities ought to automatically
1172   re-link references to the Request-URI to one or more of the new
1173   references returned by the server, where possible. This response is
1174   cacheable unless indicated otherwise.
1177   The new permanent URI &SHOULD; be given by the Location field in the
1178   response. Unless the request method was HEAD, the entity of the
1179   response &SHOULD; contain a short hypertext note with a hyperlink to
1180   the new URI(s).
1183   If the 301 status code is received in response to a request method
1184   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1185   then the request &MAY; be automatically redirected by the user agent without
1186   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1187   request unless it can be confirmed by the user, since this might
1188   change the conditions under which the request was issued.
1189  <list><t>
1190      <x:h>Note:</x:h> When automatically redirecting a POST request after
1191      receiving a 301 status code, some existing HTTP/1.0 user agents
1192      will erroneously change it into a GET request.
1193  </t></list>
1197<section title="302 Found" anchor="status.302">
1198  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1199  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1201   The requested resource resides temporarily under a different URI.
1202   Since the redirection might be altered on occasion, the client &SHOULD;
1203   continue to use the Request-URI for future requests.  This response
1204   is only cacheable if indicated by a Cache-Control or Expires header
1205   field.
1208   The temporary URI &SHOULD; be given by the Location field in the
1209   response. Unless the request method was HEAD, the entity of the
1210   response &SHOULD; contain a short hypertext note with a hyperlink to
1211   the new URI(s).
1214   If the 302 status code is received in response to a request method
1215   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1216   then the request &MAY; be automatically redirected by the user agent without
1217   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1218   request unless it can be confirmed by the user, since this might
1219   change the conditions under which the request was issued.
1220  <list><t>
1221      <x:h>Note:</x:h> <xref target="RFC1945"/> and <xref target="RFC2068"/> specify that the client is not allowed
1222      to change the method on the redirected request.  However, most
1223      existing user agent implementations treat 302 as if it were a 303
1224      response, performing a GET on the Location field-value regardless
1225      of the original request method. The status codes 303 and 307 have
1226      been added for servers that wish to make unambiguously clear which
1227      kind of reaction is expected of the client.
1228  </t></list>
1232<section title="303 See Other" anchor="status.303">
1233  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1234  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1236   The response to the request can be found under a different URI and
1237   &SHOULD; be retrieved using a GET method on that resource. This method
1238   exists primarily to allow the output of a POST-activated script to
1239   redirect the user agent to a selected resource. The new URI is not a
1240   substitute reference for the originally requested resource. The 303
1241   response &MUST-NOT; be cached, but the response to the second
1242   (redirected) request might be cacheable.
1245   The different URI &SHOULD; be given by the Location field in the
1246   response. Unless the request method was HEAD, the entity of the
1247   response &SHOULD; contain a short hypertext note with a hyperlink to
1248   the new URI(s).
1249  <list><t>
1250      <x:h>Note:</x:h> Many pre-HTTP/1.1 user agents do not understand the 303
1251      status. When interoperability with such clients is a concern, the
1252      302 status code may be used instead, since most user agents react
1253      to a 302 response as described here for 303.
1254  </t></list>
1258<section title="304 Not Modified" anchor="status.304">
1259  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1260  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1262   The response to the request has not been modified since the conditions
1263   indicated by the client's conditional GET request, as defined in &conditional;.
1267<section title="305 Use Proxy" anchor="status.305">
1268  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1269  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1271   The requested resource &MUST; be accessed through the proxy given by
1272   the Location field. The Location field gives the URI of the proxy.
1273   The recipient is expected to repeat this single request via the
1274   proxy. 305 responses &MUST; only be generated by origin servers.
1275  <list><t>
1276      <x:h>Note:</x:h> <xref target="RFC2068"/> was not clear that 305 was intended to redirect a
1277      single request, and to be generated by origin servers only.  Not
1278      observing these limitations has significant security consequences.
1279  </t></list>
1283<section title="306 (Unused)" anchor="status.306">
1284  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1285  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1287   The 306 status code was used in a previous version of the
1288   specification, is no longer used, and the code is reserved.
1292<section title="307 Temporary Redirect" anchor="status.307">
1293  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1294  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1296   The requested resource resides temporarily under a different URI.
1297   Since the redirection &MAY; be altered on occasion, the client &SHOULD;
1298   continue to use the Request-URI for future requests.  This response
1299   is only cacheable if indicated by a Cache-Control or Expires header
1300   field.
1303   The temporary URI &SHOULD; be given by the Location field in the
1304   response. Unless the request method was HEAD, the entity of the
1305   response &SHOULD; contain a short hypertext note with a hyperlink to
1306   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1307   understand the 307 status. Therefore, the note &SHOULD; contain the
1308   information necessary for a user to repeat the original request on
1309   the new URI.
1312   If the 307 status code is received in response to a request method
1313   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1314   then the request &MAY; be automatically redirected by the user agent without
1315   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1316   request unless it can be confirmed by the user, since this might
1317   change the conditions under which the request was issued.
1322<section title="Client Error 4xx" anchor="status.4xx">
1324   The 4xx class of status code is intended for cases in which the
1325   client seems to have erred. Except when responding to a HEAD request,
1326   the server &SHOULD; include an entity containing an explanation of the
1327   error situation, and whether it is a temporary or permanent
1328   condition. These status codes are applicable to any request method.
1329   User agents &SHOULD; display any included entity to the user.
1332   If the client is sending data, a server implementation using TCP
1333   &SHOULD; be careful to ensure that the client acknowledges receipt of
1334   the packet(s) containing the response, before the server closes the
1335   input connection. If the client continues sending data to the server
1336   after the close, the server's TCP stack will send a reset packet to
1337   the client, which may erase the client's unacknowledged input buffers
1338   before they can be read and interpreted by the HTTP application.
1341<section title="400 Bad Request" anchor="status.400">
1342  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1343  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1345   The request could not be understood by the server due to malformed
1346   syntax. The client &SHOULD-NOT;  repeat the request without
1347   modifications.
1351<section title="401 Unauthorized" anchor="status.401">
1352  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1353  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1355   The request requires user authentication (see &auth;).
1359<section title="402 Payment Required" anchor="status.402">
1360  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1361  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1363   This code is reserved for future use.
1367<section title="403 Forbidden" anchor="status.403">
1368  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1369  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1371   The server understood the request, but is refusing to fulfill it.
1372   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1373   If the request method was not HEAD and the server wishes to make
1374   public why the request has not been fulfilled, it &SHOULD; describe the
1375   reason for the refusal in the entity.  If the server does not wish to
1376   make this information available to the client, the status code 404
1377   (Not Found) can be used instead.
1381<section title="404 Not Found" anchor="status.404">
1382  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1383  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1385   The server has not found anything matching the Request-URI. No
1386   indication is given of whether the condition is temporary or
1387   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1388   knows, through some internally configurable mechanism, that an old
1389   resource is permanently unavailable and has no forwarding address.
1390   This status code is commonly used when the server does not wish to
1391   reveal exactly why the request has been refused, or when no other
1392   response is applicable.
1396<section title="405 Method Not Allowed" anchor="status.405">
1397  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1398  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1400   The method specified in the Request-Line is not allowed for the
1401   resource identified by the Request-URI. The response &MUST; include an
1402   Allow header containing a list of valid methods for the requested
1403   resource.
1407<section title="406 Not Acceptable" anchor="status.406">
1408  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1409  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1411   The resource identified by the request is only capable of generating
1412   response entities which have content characteristics not acceptable
1413   according to the accept headers sent in the request.
1416   Unless it was a HEAD request, the response &SHOULD; include an entity
1417   containing a list of available entity characteristics and location(s)
1418   from which the user or user agent can choose the one most
1419   appropriate. The entity format is specified by the media type given
1420   in the Content-Type header field. Depending upon the format and the
1421   capabilities of the user agent, selection of the most appropriate
1422   choice &MAY; be performed automatically. However, this specification
1423   does not define any standard for such automatic selection.
1424  <list><t>
1425      <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1426      not acceptable according to the accept headers sent in the
1427      request. In some cases, this may even be preferable to sending a
1428      406 response. User agents are encouraged to inspect the headers of
1429      an incoming response to determine if it is acceptable.
1430  </t></list>
1433   If the response could be unacceptable, a user agent &SHOULD;
1434   temporarily stop receipt of more data and query the user for a
1435   decision on further actions.
1439<section title="407 Proxy Authentication Required" anchor="status.407">
1440  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1441  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1443   This code is similar to 401 (Unauthorized), but indicates that the
1444   client must first authenticate itself with the proxy (see &auth;).
1448<section title="408 Request Timeout" anchor="status.408">
1449  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1450  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1452   The client did not produce a request within the time that the server
1453   was prepared to wait. The client &MAY; repeat the request without
1454   modifications at any later time.
1458<section title="409 Conflict" anchor="status.409">
1459  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1460  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1462   The request could not be completed due to a conflict with the current
1463   state of the resource. This code is only allowed in situations where
1464   it is expected that the user might be able to resolve the conflict
1465   and resubmit the request. The response body &SHOULD; include enough
1466   information for the user to recognize the source of the conflict.
1467   Ideally, the response entity would include enough information for the
1468   user or user agent to fix the problem; however, that might not be
1469   possible and is not required.
1472   Conflicts are most likely to occur in response to a PUT request. For
1473   example, if versioning were being used and the entity being PUT
1474   included changes to a resource which conflict with those made by an
1475   earlier (third-party) request, the server might use the 409 response
1476   to indicate that it can't complete the request. In this case, the
1477   response entity would likely contain a list of the differences
1478   between the two versions in a format defined by the response
1479   Content-Type.
1483<section title="410 Gone" anchor="status.410">
1484  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1485  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1487   The requested resource is no longer available at the server and no
1488   forwarding address is known. This condition is expected to be
1489   considered permanent. Clients with link editing capabilities &SHOULD;
1490   delete references to the Request-URI after user approval. If the
1491   server does not know, or has no facility to determine, whether or not
1492   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1493   used instead. This response is cacheable unless indicated otherwise.
1496   The 410 response is primarily intended to assist the task of web
1497   maintenance by notifying the recipient that the resource is
1498   intentionally unavailable and that the server owners desire that
1499   remote links to that resource be removed. Such an event is common for
1500   limited-time, promotional services and for resources belonging to
1501   individuals no longer working at the server's site. It is not
1502   necessary to mark all permanently unavailable resources as "gone" or
1503   to keep the mark for any length of time -- that is left to the
1504   discretion of the server owner.
1508<section title="411 Length Required" anchor="status.411">
1509  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1510  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1512   The server refuses to accept the request without a defined Content-Length.
1513   The client &MAY; repeat the request if it adds a valid
1514   Content-Length header field containing the length of the message-body
1515   in the request message.
1519<section title="412 Precondition Failed" anchor="status.412">
1520  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1521  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1523   The precondition given in one or more of the request-header fields
1524   evaluated to false when it was tested on the server, as defined in
1525   &conditional;.
1529<section title="413 Request Entity Too Large" anchor="status.413">
1530  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1531  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1533   The server is refusing to process a request because the request
1534   entity is larger than the server is willing or able to process. The
1535   server &MAY; close the connection to prevent the client from continuing
1536   the request.
1539   If the condition is temporary, the server &SHOULD; include a Retry-After
1540   header field to indicate that it is temporary and after what
1541   time the client &MAY; try again.
1545<section title="414 Request-URI Too Long" anchor="status.414">
1546  <iref primary="true" item="414 Request-URI Too Long (status code)" x:for-anchor=""/>
1547  <iref primary="true" item="Status Codes" subitem="414 Request-URI Too Long" x:for-anchor=""/>
1549   The server is refusing to service the request because the Request-URI
1550   is longer than the server is willing to interpret. This rare
1551   condition is only likely to occur when a client has improperly
1552   converted a POST request to a GET request with long query
1553   information, when the client has descended into a URI "black hole" of
1554   redirection (e.g., a redirected URI prefix that points to a suffix of
1555   itself), or when the server is under attack by a client attempting to
1556   exploit security holes present in some servers using fixed-length
1557   buffers for reading or manipulating the Request-URI.
1561<section title="415 Unsupported Media Type" anchor="status.415">
1562  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1563  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1565   The server is refusing to service the request because the entity of
1566   the request is in a format not supported by the requested resource
1567   for the requested method.
1571<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1572  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1573  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1575   The request included a Range request-header field (&header-range;) and none of
1576   the range-specifier values in this field overlap the current extent
1577   of the selected resource.
1581<section title="417 Expectation Failed" anchor="status.417">
1582  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1583  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1585   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1586   could not be met by this server, or, if the server is a proxy,
1587   the server has unambiguous evidence that the request could not be met
1588   by the next-hop server.
1593<section title="Server Error 5xx" anchor="status.5xx">
1595   Response status codes beginning with the digit "5" indicate cases in
1596   which the server is aware that it has erred or is incapable of
1597   performing the request. Except when responding to a HEAD request, the
1598   server &SHOULD; include an entity containing an explanation of the
1599   error situation, and whether it is a temporary or permanent
1600   condition. User agents &SHOULD; display any included entity to the
1601   user. These response codes are applicable to any request method.
1604<section title="500 Internal Server Error" anchor="status.500">
1605  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1606  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1608   The server encountered an unexpected condition which prevented it
1609   from fulfilling the request.
1613<section title="501 Not Implemented" anchor="status.501">
1614  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1615  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1617   The server does not support the functionality required to fulfill the
1618   request. This is the appropriate response when the server does not
1619   recognize the request method and is not capable of supporting it for
1620   any resource.
1624<section title="502 Bad Gateway" anchor="status.502">
1625  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1626  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1628   The server, while acting as a gateway or proxy, received an invalid
1629   response from the upstream server it accessed in attempting to
1630   fulfill the request.
1634<section title="503 Service Unavailable" anchor="status.503">
1635  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1636  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1638   The server is currently unable to handle the request due to a
1639   temporary overloading or maintenance of the server. The implication
1640   is that this is a temporary condition which will be alleviated after
1641   some delay. If known, the length of the delay &MAY; be indicated in a
1642   Retry-After header. If no Retry-After is given, the client &SHOULD;
1643   handle the response as it would for a 500 response.
1644  <list><t>
1645      <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1646      server must use it when becoming overloaded. Some servers may wish
1647      to simply refuse the connection.
1648  </t></list>
1652<section title="504 Gateway Timeout" anchor="status.504">
1653  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1654  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1656   The server, while acting as a gateway or proxy, did not receive a
1657   timely response from the upstream server specified by the URI (e.g.
1658   HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed
1659   to access in attempting to complete the request.
1660  <list><t>
1661      <x:h>Note:</x:h> Note to implementors: some deployed proxies are known to
1662      return 400 or 500 when DNS lookups time out.
1663  </t></list>
1667<section title="505 HTTP Version Not Supported" anchor="status.505">
1668  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1669  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
1671   The server does not support, or refuses to support, the protocol
1672   version that was used in the request message. The server is
1673   indicating that it is unable or unwilling to complete the request
1674   using the same major version as the client, as described in &http-version;,
1675   other than with this error message. The response &SHOULD; contain
1676   an entity describing why that version is not supported and what other
1677   protocols are supported by that server.
1685<section title="Header Field Definitions" anchor="header.fields">
1687   This section defines the syntax and semantics of HTTP/1.1 header fields
1688   related to request and response semantics.
1691   For entity-header fields, both sender and recipient refer to either the
1692   client or the server, depending on who sends and who receives the entity.
1695<section title="Allow" anchor="header.allow">
1696  <iref primary="true" item="Allow header" x:for-anchor=""/>
1697  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
1699      The Allow entity-header field lists the set of methods supported
1700      by the resource identified by the Request-URI. The purpose of this
1701      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.
1705<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/>
1706  Allow   = "Allow" ":" #Method
1709      Example of use:
1711<figure><artwork type="example">
1712       Allow: GET, HEAD, PUT
1715      This field cannot prevent a client from trying other methods.
1716      However, the indications given by the Allow header field value
1717      &SHOULD; be followed. The actual set of allowed methods is defined
1718      by the origin server at the time of each request.
1721      The Allow header field &MAY; be provided with a PUT request to
1722      recommend the methods to be supported by the new or modified
1723      resource. The server is not required to support these methods and
1724      &SHOULD; include an Allow header in the response giving the actual
1725      supported methods.
1728      A proxy &MUST-NOT; modify the Allow header field even if it does not
1729      understand all the methods specified, since the user agent might
1730      have other means of communicating with the origin server.
1734<section title="Expect" anchor="header.expect">
1735  <iref primary="true" item="Expect header" x:for-anchor=""/>
1736  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
1738   The Expect request-header field is used to indicate that particular
1739   server behaviors are required by the client.
1741<figure><artwork type="abnf2616"><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"/>
1742  Expect       =  "Expect" ":" 1#expectation
1744  expectation  =  "100-continue" | expectation-extension
1745  expectation-extension =  token [ "=" ( token | quoted-string )
1746                           *expect-params ]
1747  expect-params =  ";" token [ "=" ( token | quoted-string ) ]
1750   A server that does not understand or is unable to comply with any of
1751   the expectation values in the Expect field of a request &MUST; respond
1752   with appropriate error status. The server &MUST; respond with a 417
1753   (Expectation Failed) status if any of the expectations cannot be met
1754   or, if there are other problems with the request, some other 4xx
1755   status.
1758   This header field is defined with extensible syntax to allow for
1759   future extensions. If a server receives a request containing an
1760   Expect field that includes an expectation-extension that it does not
1761   support, it &MUST; respond with a 417 (Expectation Failed) status.
1764   Comparison of expectation values is case-insensitive for unquoted
1765   tokens (including the 100-continue token), and is case-sensitive for
1766   quoted-string expectation-extensions.
1769   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
1770   return a 417 (Expectation Failed) status if it receives a request
1771   with an expectation that it cannot meet. However, the Expect
1772   request-header itself is end-to-end; it &MUST; be forwarded if the
1773   request is forwarded.
1776   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1777   Expect header.
1780   See &use100; for the use of the 100 (Continue) status.
1784<section title="From" anchor="header.from">
1785  <iref primary="true" item="From header" x:for-anchor=""/>
1786  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
1788   The From request-header field, if given, &SHOULD; contain an Internet
1789   e-mail address for the human user who controls the requesting user
1790   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
1791   in <xref x:sec="3.4" x:fmt="of" target="RFC2822"/>:
1793<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/>
1794  From    = "From" ":" mailbox
1796  mailbox = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC2822"/>&gt;
1799   An example is:
1801<figure><artwork type="example">
1802    From:
1805   This header field &MAY; be used for logging purposes and as a means for
1806   identifying the source of invalid or unwanted requests. It &SHOULD-NOT;
1807   be used as an insecure form of access protection. The interpretation
1808   of this field is that the request is being performed on behalf of the
1809   person given, who accepts responsibility for the method performed. In
1810   particular, robot agents &SHOULD; include this header so that the
1811   person responsible for running the robot can be contacted if problems
1812   occur on the receiving end.
1815   The Internet e-mail address in this field &MAY; be separate from the
1816   Internet host which issued the request. For example, when a request
1817   is passed through a proxy the original issuer's address &SHOULD; be
1818   used.
1821   The client &SHOULD-NOT;  send the From header field without the user's
1822   approval, as it might conflict with the user's privacy interests or
1823   their site's security policy. It is strongly recommended that the
1824   user be able to disable, enable, and modify the value of this field
1825   at any time prior to a request.
1829<section title="Location" anchor="header.location">
1830  <iref primary="true" item="Location header" x:for-anchor=""/>
1831  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
1833   The Location response-header field is used to redirect the recipient
1834   to a location other than the Request-URI for completion of the
1835   request or identification of a new resource. For 201 (Created)
1836   responses, the Location is that of the new resource which was created
1837   by the request. For 3xx responses, the location &SHOULD; indicate the
1838   server's preferred URI for automatic redirection to the resource. The
1839   field value consists of a single absolute URI.
1841<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/>
1842  Location       = "Location" ":" absoluteURI [ "#" fragment ]
1845   An example is:
1847<figure><artwork type="example">
1848    Location:
1851  <list><t>
1852      <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
1853      from Location in that the Content-Location identifies the original
1854      location of the entity enclosed in the request. It is therefore
1855      possible for a response to contain header fields for both Location
1856      and Content-Location.
1857  </t></list>
1860   There are circumstances in which a fragment identifier in a Location URL would not be appropriate:
1861   <list style="symbols">
1862      <t>With a 201 Created response, because in this usage the Location header specifies the URL for the entire created resource.</t>
1863      <t>With a 300 Multiple Choices, since the choice decision is intended to be made on resource characteristics and not fragment characteristics.</t>
1864      <t>With 305 Use Proxy.</t>
1865   </list>
1869<section title="Max-Forwards" anchor="header.max-forwards">
1870  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
1871  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
1873   The Max-Forwards request-header field provides a mechanism with the
1874   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>) methods to limit the
1875   number of proxies or gateways that can forward the request to the
1876   next inbound server. This can be useful when the client is attempting
1877   to trace a request chain which appears to be failing or looping in
1878   mid-chain.
1880<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/>
1881  Max-Forwards   = "Max-Forwards" ":" 1*DIGIT
1884   The Max-Forwards value is a decimal integer indicating the remaining
1885   number of times this request message may be forwarded.
1888   Each proxy or gateway recipient of a TRACE or OPTIONS request
1889   containing a Max-Forwards header field &MUST; check and update its
1890   value prior to forwarding the request. If the received value is zero
1891   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
1892   respond as the final recipient. If the received Max-Forwards value is
1893   greater than zero, then the forwarded message &MUST; contain an updated
1894   Max-Forwards field with a value decremented by one (1).
1897   The Max-Forwards header field &MAY; be ignored for all other methods
1898   defined by this specification and for any extension methods for which
1899   it is not explicitly referred to as part of that method definition.
1903<section title="Referer" anchor="header.referer">
1904  <iref primary="true" item="Referer header" x:for-anchor=""/>
1905  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
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.
1917<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/>
1918  Referer        = "Referer" ":" ( absoluteURI | relativeURI )
1921   Example:
1923<figure><artwork type="example">
1924    Referer:
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=""/> for security considerations.
1933<section title="Retry-After" anchor="header.retry-after">
1934  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
1935  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
1937   The Retry-After response-header field can be used with a 503 (Service
1938   Unavailable) response to indicate how long the service is expected to
1939   be unavailable to the requesting client. This field &MAY; also be used
1940   with any 3xx (Redirection) response to indicate the minimum time the
1941   user-agent is asked wait before issuing the redirected request. The
1942   value of this field can be either an HTTP-date or an integer number
1943   of seconds (in decimal) after the time of the response.
1945<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/>
1946  Retry-After  = "Retry-After" ":" ( HTTP-date | delta-seconds )
1949   Two examples of its use are
1951<figure><artwork type="example">
1952    Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
1953    Retry-After: 120
1956   In the latter example, the delay is 2 minutes.
1960<section title="Server" anchor="header.server">
1961  <iref primary="true" item="Server header" x:for-anchor=""/>
1962  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
1964   The Server response-header field contains information about the
1965   software used by the origin server to handle the request. The field
1966   can contain multiple product tokens (&product-tokens;) and comments
1967   identifying the server and any significant subproducts. The product
1968   tokens are listed in order of their significance for identifying the
1969   application.
1971<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/>
1972  Server         = "Server" ":" 1*( product | comment )
1975   Example:
1977<figure><artwork type="example">
1978    Server: CERN/3.0 libwww/2.17
1981   If the response is being forwarded through a proxy, the proxy
1982   application &MUST-NOT; modify the Server response-header. Instead, it
1983   &MUST; include a Via field (as described in &header-via;).
1984  <list><t>
1985      <x:h>Note:</x:h> Revealing the specific software version of the server might
1986      allow the server machine to become more vulnerable to attacks
1987      against software that is known to contain security holes. Server
1988      implementors are encouraged to make this field a configurable
1989      option.
1990  </t></list>
1994<section title="User-Agent" anchor="header.user-agent">
1995  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
1996  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
1998   The User-Agent request-header field contains information about the
1999   user agent originating the request. This is for statistical purposes,
2000   the tracing of protocol violations, and automated recognition of user
2001   agents for the sake of tailoring responses to avoid particular user
2002   agent limitations. User agents &SHOULD; include this field with
2003   requests. The field can contain multiple product tokens (&product-tokens;)
2004   and comments identifying the agent and any subproducts which form a
2005   significant part of the user agent. By convention, the product tokens
2006   are listed in order of their significance for identifying the
2007   application.
2009<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/>
2010  User-Agent     = "User-Agent" ":" 1*( product | comment )
2013   Example:
2015<figure><artwork type="example">
2016    User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2022<section title="IANA Considerations" anchor="IANA.considerations">
2024   <cref>TBD.</cref>
2028<section title="Security Considerations" anchor="security.considerations">
2030   This section is meant to inform application developers, information
2031   providers, and users of the security limitations in HTTP/1.1 as
2032   described by this document. The discussion does not include
2033   definitive solutions to the problems revealed, though it does make
2034   some suggestions for reducing security risks.
2037<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2039   Like any generic data transfer protocol, HTTP cannot regulate the
2040   content of the data that is transferred, nor is there any a priori
2041   method of determining the sensitivity of any particular piece of
2042   information within the context of any given request. Therefore,
2043   applications &SHOULD; supply as much control over this information as
2044   possible to the provider of that information. Four header fields are
2045   worth special mention in this context: Server, Via, Referer and From.
2048   Revealing the specific software version of the server might allow the
2049   server machine to become more vulnerable to attacks against software
2050   that is known to contain security holes. Implementors &SHOULD; make the
2051   Server header field a configurable option.
2054   Proxies which serve as a portal through a network firewall &SHOULD;
2055   take special precautions regarding the transfer of header information
2056   that identifies the hosts behind the firewall. In particular, they
2057   &SHOULD; remove, or replace with sanitized versions, any Via fields
2058   generated behind the firewall.
2061   The Referer header allows reading patterns to be studied and reverse
2062   links drawn. Although it can be very useful, its power can be abused
2063   if user details are not separated from the information contained in
2064   the Referer. Even when the personal information has been removed, the
2065   Referer header might indicate a private document's URI whose
2066   publication would be inappropriate.
2069   The information sent in the From field might conflict with the user's
2070   privacy interests or their site's security policy, and hence it
2071   &SHOULD-NOT;  be transmitted without the user being able to disable,
2072   enable, and modify the contents of the field. The user &MUST; be able
2073   to set the contents of this field within a user preference or
2074   application defaults configuration.
2077   We suggest, though do not require, that a convenient toggle interface
2078   be provided for the user to enable or disable the sending of From and
2079   Referer information.
2082   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2083   fields can sometimes be used to determine that a specific client or
2084   server have a particular security hole which might be exploited.
2085   Unfortunately, this same information is often used for other valuable
2086   purposes for which HTTP currently has no better mechanism.
2090<section title="Encoding Sensitive Information in URIs" anchor="">
2092   Because the source of a link might be private information or might
2093   reveal an otherwise private information source, it is strongly
2094   recommended that the user be able to select whether or not the
2095   Referer field is sent. For example, a browser client could have a
2096   toggle switch for browsing openly/anonymously, which would
2097   respectively enable/disable the sending of Referer and From
2098   information.
2101   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2102   HTTP request if the referring page was transferred with a secure
2103   protocol.
2106   Authors of services should not use
2107   GET-based forms for the submission of sensitive data because that
2108   data will be encoded in the Request-URI. Many existing
2109   servers, proxies, and user agents log or display the Request-URI in
2110   places where it might be visible to third parties. Such services can
2111   use POST-based form submission instead.
2115<section title="Location Headers and Spoofing" anchor="location.spoofing">
2117   If a single server supports multiple organizations that do not trust
2118   one another, then it &MUST; check the values of Location and Content-Location
2119   headers in responses that are generated under control of
2120   said organizations to make sure that they do not attempt to
2121   invalidate resources over which they have no authority.
2127<section title="Acknowledgments" anchor="ack">
2132<references title="Normative References">
2134<reference anchor="Part1">
2135  <front>
2136    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2137    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2138      <organization abbrev="Day Software">Day Software</organization>
2139      <address><email></email></address>
2140    </author>
2141    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2142      <organization>One Laptop per Child</organization>
2143      <address><email></email></address>
2144    </author>
2145    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2146      <organization abbrev="HP">Hewlett-Packard Company</organization>
2147      <address><email></email></address>
2148    </author>
2149    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2150      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2151      <address><email></email></address>
2152    </author>
2153    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2154      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2155      <address><email></email></address>
2156    </author>
2157    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2158      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2159      <address><email></email></address>
2160    </author>
2161    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2162      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2163      <address><email></email></address>
2164    </author>
2165    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2166      <organization abbrev="W3C">World Wide Web Consortium</organization>
2167      <address><email></email></address>
2168    </author>
2169    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2170      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2171      <address><email></email></address>
2172    </author>
2173    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2174  </front>
2175  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2176  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2179<reference anchor="Part3">
2180  <front>
2181    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2182    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2183      <organization abbrev="Day Software">Day Software</organization>
2184      <address><email></email></address>
2185    </author>
2186    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2187      <organization>One Laptop per Child</organization>
2188      <address><email></email></address>
2189    </author>
2190    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2191      <organization abbrev="HP">Hewlett-Packard Company</organization>
2192      <address><email></email></address>
2193    </author>
2194    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2195      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2196      <address><email></email></address>
2197    </author>
2198    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2199      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2200      <address><email></email></address>
2201    </author>
2202    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2203      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2204      <address><email></email></address>
2205    </author>
2206    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2207      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2208      <address><email></email></address>
2209    </author>
2210    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2211      <organization abbrev="W3C">World Wide Web Consortium</organization>
2212      <address><email></email></address>
2213    </author>
2214    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2215      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2216      <address><email></email></address>
2217    </author>
2218    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2219  </front>
2220  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2221  <x:source href="p3-payload.xml" basename="p3-payload"/>
2224<reference anchor="Part4">
2225  <front>
2226    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2227    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2228      <organization abbrev="Day Software">Day Software</organization>
2229      <address><email></email></address>
2230    </author>
2231    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2232      <organization>One Laptop per Child</organization>
2233      <address><email></email></address>
2234    </author>
2235    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2236      <organization abbrev="HP">Hewlett-Packard Company</organization>
2237      <address><email></email></address>
2238    </author>
2239    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2240      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2241      <address><email></email></address>
2242    </author>
2243    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2244      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2245      <address><email></email></address>
2246    </author>
2247    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2248      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2249      <address><email></email></address>
2250    </author>
2251    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2252      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2253      <address><email></email></address>
2254    </author>
2255    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2256      <organization abbrev="W3C">World Wide Web Consortium</organization>
2257      <address><email></email></address>
2258    </author>
2259    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2260      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2261      <address><email></email></address>
2262    </author>
2263    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2264  </front>
2265  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2266  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2269<reference anchor="Part5">
2270  <front>
2271    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2272    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2273      <organization abbrev="Day Software">Day Software</organization>
2274      <address><email></email></address>
2275    </author>
2276    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2277      <organization>One Laptop per Child</organization>
2278      <address><email></email></address>
2279    </author>
2280    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2281      <organization abbrev="HP">Hewlett-Packard Company</organization>
2282      <address><email></email></address>
2283    </author>
2284    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2285      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2286      <address><email></email></address>
2287    </author>
2288    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2289      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2290      <address><email></email></address>
2291    </author>
2292    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2293      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2294      <address><email></email></address>
2295    </author>
2296    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2297      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2298      <address><email></email></address>
2299    </author>
2300    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2301      <organization abbrev="W3C">World Wide Web Consortium</organization>
2302      <address><email></email></address>
2303    </author>
2304    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2305      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2306      <address><email></email></address>
2307    </author>
2308    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2309  </front>
2310  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
2311  <x:source href="p5-range.xml" basename="p5-range"/>
2314<reference anchor="Part6">
2315  <front>
2316    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2317    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2318      <organization abbrev="Day Software">Day Software</organization>
2319      <address><email></email></address>
2320    </author>
2321    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2322      <organization>One Laptop per Child</organization>
2323      <address><email></email></address>
2324    </author>
2325    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2326      <organization abbrev="HP">Hewlett-Packard Company</organization>
2327      <address><email></email></address>
2328    </author>
2329    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2330      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2331      <address><email></email></address>
2332    </author>
2333    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2334      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2335      <address><email></email></address>
2336    </author>
2337    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2338      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2339      <address><email></email></address>
2340    </author>
2341    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2342      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2343      <address><email></email></address>
2344    </author>
2345    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2346      <organization abbrev="W3C">World Wide Web Consortium</organization>
2347      <address><email></email></address>
2348    </author>
2349    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2350      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2351      <address><email></email></address>
2352    </author>
2353    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2354  </front>
2355  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2356  <x:source href="p6-cache.xml" basename="p6-cache"/>
2359<reference anchor="Part7">
2360  <front>
2361    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2362    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2363      <organization abbrev="Day Software">Day Software</organization>
2364      <address><email></email></address>
2365    </author>
2366    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2367      <organization>One Laptop per Child</organization>
2368      <address><email></email></address>
2369    </author>
2370    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2371      <organization abbrev="HP">Hewlett-Packard Company</organization>
2372      <address><email></email></address>
2373    </author>
2374    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2375      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2376      <address><email></email></address>
2377    </author>
2378    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2379      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2380      <address><email></email></address>
2381    </author>
2382    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2383      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2384      <address><email></email></address>
2385    </author>
2386    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2387      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2388      <address><email></email></address>
2389    </author>
2390    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2391      <organization abbrev="W3C">World Wide Web Consortium</organization>
2392      <address><email></email></address>
2393    </author>
2394    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2395      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2396      <address><email></email></address>
2397    </author>
2398    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2399  </front>
2400  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
2401  <x:source href="p7-auth.xml" basename="p7-auth"/>
2404<reference anchor="RFC2119">
2405  <front>
2406    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2407    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2408      <organization>Harvard University</organization>
2409      <address><email></email></address>
2410    </author>
2411    <date month="March" year="1997"/>
2412  </front>
2413  <seriesInfo name="BCP" value="14"/>
2414  <seriesInfo name="RFC" value="2119"/>
2419<references title="Informative References">
2421<reference anchor="Luo1998">
2422  <front>
2423    <title>Tunneling TCP based protocols through Web proxy servers</title>
2424    <author initials="A." surname="Luotonen" fullname="A. Luotonen">
2425      <organization/>
2426    </author>
2427    <date year="1998" month="August"/>
2428  </front>
2429  <seriesInfo name="Internet-Draft" value="draft-luotonen-web-proxy-tunneling-01"/>
2432<reference anchor="RFC1945">
2433  <front>
2434    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2435    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2436      <organization>MIT, Laboratory for Computer Science</organization>
2437      <address><email></email></address>
2438    </author>
2439    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2440      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2441      <address><email></email></address>
2442    </author>
2443    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2444      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2445      <address><email></email></address>
2446    </author>
2447    <date month="May" year="1996"/>
2448  </front>
2449  <seriesInfo name="RFC" value="1945"/>
2452<reference anchor="RFC2068">
2453  <front>
2454    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2455    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2456      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2457      <address><email></email></address>
2458    </author>
2459    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2460      <organization>MIT Laboratory for Computer Science</organization>
2461      <address><email></email></address>
2462    </author>
2463    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2464      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2465      <address><email></email></address>
2466    </author>
2467    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2468      <organization>MIT Laboratory for Computer Science</organization>
2469      <address><email></email></address>
2470    </author>
2471    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2472      <organization>MIT Laboratory for Computer Science</organization>
2473      <address><email></email></address>
2474    </author>
2475    <date month="January" year="1997"/>
2476  </front>
2477  <seriesInfo name="RFC" value="2068"/>
2480<reference anchor="RFC2616">
2481  <front>
2482    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2483    <author initials="R." surname="Fielding" fullname="R. Fielding">
2484      <organization>University of California, Irvine</organization>
2485      <address><email></email></address>
2486    </author>
2487    <author initials="J." surname="Gettys" fullname="J. Gettys">
2488      <organization>W3C</organization>
2489      <address><email></email></address>
2490    </author>
2491    <author initials="J." surname="Mogul" fullname="J. Mogul">
2492      <organization>Compaq Computer Corporation</organization>
2493      <address><email></email></address>
2494    </author>
2495    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2496      <organization>MIT Laboratory for Computer Science</organization>
2497      <address><email></email></address>
2498    </author>
2499    <author initials="L." surname="Masinter" fullname="L. Masinter">
2500      <organization>Xerox Corporation</organization>
2501      <address><email></email></address>
2502    </author>
2503    <author initials="P." surname="Leach" fullname="P. Leach">
2504      <organization>Microsoft Corporation</organization>
2505      <address><email></email></address>
2506    </author>
2507    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2508      <organization>W3C</organization>
2509      <address><email></email></address>
2510    </author>
2511    <date month="June" year="1999"/>
2512  </front>
2513  <seriesInfo name="RFC" value="2616"/>
2516<reference anchor="RFC2822">
2517  <front>
2518    <title>Internet Message Format</title>
2519    <author initials="P." surname="Resnick" fullname="P. Resnick">
2520      <organization>QUALCOMM Incorporated</organization>
2521    </author>
2522    <date year="2001" month="April"/>
2523  </front>
2524  <seriesInfo name="RFC" value="2822"/>
2529<section title="Compatibility with Previous Versions" anchor="compatibility">
2530<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
2532   Clarified which error code should be used for inbound server failures
2533   (e.g. DNS failures). (<xref target="status.504"/>).
2536   201 (Created) had a race that required an Etag be sent when a resource is
2537   first created. (<xref target="status.201"/>).
2540   Rewrite of message transmission requirements to make it much harder
2541   for implementors to get it wrong, as the consequences of errors here
2542   can have significant impact on the Internet, and to deal with the
2543   following problems:
2544  <list style="numbers">
2545      <t>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
2546         this was incorrectly placing a requirement on the behavior of
2547         an implementation of a future version of HTTP/1.x</t>
2549      <t>Made it clear that user-agents should retry requests, not
2550         "clients" in general.</t>
2552      <t>Converted requirements for clients to ignore unexpected 100
2553         (Continue) responses, and for proxies to forward 100 responses,
2554         into a general requirement for 1xx responses.</t>
2556      <t>Modified some TCP-specific language, to make it clearer that
2557         non-TCP transports are possible for HTTP.</t>
2559      <t>Require that the origin server &MUST-NOT; wait for the request
2560         body before it sends a required 100 (Continue) response.</t>
2562      <t>Allow, rather than require, a server to omit 100 (Continue) if
2563         it has already seen some of the request body.</t>
2565      <t>Allow servers to defend against denial-of-service attacks and
2566         broken clients.</t>
2567  </list>
2570   This change adds the Expect header and 417 status code.
2573   Clean up confusion between 403 and 404 responses. (Section <xref target="status.403" format="counter"/>,
2574   <xref target="status.404" format="counter"/>, and <xref target="status.410" format="counter"/>)
2577   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
2578   implemented in previous versions of this specification. See <xref target="RFC2068"/>.
2582<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
2584  Clarify definition of POST.
2585  (<xref target="POST"/>)
2588  Failed to consider that there are
2589  many other request methods that are safe to automatically redirect,
2590  and further that the user agent is able to make that determination
2591  based on the request method semantics.
2592  (Sections <xref format="counter" target="status.301"/>,
2593  <xref format="counter" target="status.302"/> and
2594  <xref format="counter" target="status.307"/> )
2597  Correct syntax of Location header to allow fragment,
2598  as referred symbol wasn't what was expected, and add some
2599  clarifications as to when it would not be appropriate.
2600  (<xref target="header.location"/>)
2603  In the description of the Server header, the Via field
2604  was described as a SHOULD. The requirement was and is stated
2605  correctly in the description of the Via header in &header-via;.
2606  (<xref target="header.server"/>)
2612<section title="Change Log (to be removed by RFC Editor before publication)">
2614<section title="Since RFC2616">
2616  Extracted relevant partitions from <xref target="RFC2616"/>.
2620<section title="Since draft-ietf-httpbis-p2-semantics-00">
2622  Closed issues:
2623  <list style="symbols">
2624    <t>
2625      <eref target=""/>:
2626      "Via is a MUST"
2627      (<eref target=""/>)
2628    </t>
2629    <t>
2630      <eref target=""/>:
2631      "Fragments allowed in Location"
2632      (<eref target=""/>)
2633    </t>
2634    <t>
2635      <eref target=""/>:
2636      "Safe Methods vs Redirection"
2637      (<eref target=""/>)
2638    </t>
2639    <t>
2640      <eref target=""/>:
2641      "Revise description of the POST method"
2642      (<eref target=""/>)
2643    </t>
2644    <t>
2645      <eref target=""/>:
2646      "Normative and Informative references"
2647    </t>
2648    <t>
2649      <eref target=""/>:
2650      "RFC2606 Compliance"
2651    </t>
2652    <t>
2653      <eref target=""/>:
2654      "Informative references"
2655    </t>
2656    <t>
2657      <eref target=""/>:
2658      "Redundant cross-references"
2659    </t>
2660  </list>
2663  Other changes:
2664  <list style="symbols">
2665    <t>
2666      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
2667    </t>
2668  </list>
2672<section title="Since draft-ietf-httpbis-p2-semantics-01">
2674  Closed issues:
2675  <list style="symbols">
2676    <t>
2677      <eref target=""/>:
2678      "PUT side effects"
2679    </t>
2680    <t>
2681      <eref target=""/>:
2682      "Duplicate Host header requirements"
2683    </t>
2684  </list>
2687  Ongoing work on ABNF conversion (<eref target=""/>):
2688  <list style="symbols">
2689    <t>
2690      Move "Product Tokens" section (back) into Part 1, as "token" is used
2691      in the definition of the Upgrade header.
2692    </t>
2693    <t>
2694      Add explicit references to BNF syntax and rules imported from other parts of the specification.
2695    </t>
2696    <t>
2697      Move definition of "delta-seconds" into Part1 as a common BNF element.
2698    </t>
2699  </list>
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