source: draft-ietf-httpbis/latest/p2-semantics.xml @ 206

Last change on this file since 206 was 206, checked in by julian.reschke@…, 14 years ago

Work on referencing ABNF rules adopted from other parts (done for P2 and P3); relates to #36.

  • Property svn:eol-style set to native
File size: 123.1 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 http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x=''/>">
30  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x=''/>">
31  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x=''/>">
32  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x=''/>">
33  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x=''/>">
34  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x=''/>">
35  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x=''/>">
36  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x=''/>">
37  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x=''/>">
38  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x=''/>">
39  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x=''/>">
40  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x=''/>">
41  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x=''/>">
42  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x=''/>">
43  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x=''/>">
44  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x=''/>">
45  <!ENTITY header-host                "<xref target='Part1' x:rel='' xmlns:x=''/>">
46  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x=''/>">
47  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x=''/>">
48  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x=''/>">
49  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x=''/>">
50  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x=''/>">
51  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x=''/>">
52  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x=''/>">
53  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x=''/>">
54  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x=''/>">
55  <!ENTITY header-upgrade             "<xref target='Part5' x:rel='#header.range' xmlns:x=''/>">
56  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.upgrade' xmlns:x=''/>">
57  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x=''/>">
58  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x=''/>">
59  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x=''/>">
60  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x=''/>">
61  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x=''/>">
62  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x=''/>">
64<?rfc toc="yes" ?>
65<?rfc symrefs="yes" ?>
66<?rfc sortrefs="yes" ?>
67<?rfc compact="yes"?>
68<?rfc subcompact="no" ?>
69<?rfc linkmailto="no" ?>
70<?rfc editing="no" ?>
71<?rfc comments="yes"?>
72<?rfc inline="yes"?>
73<?rfc-ext allow-markup-in-artwork="yes" ?>
74<?rfc-ext include-references-in-index="yes" ?>
75<rfc obsoletes="2616" category="std"
76     ipr="full3978" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
77     xmlns:x=''>
80  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
82  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
83    <organization abbrev="Day Software">Day Software</organization>
84    <address>
85      <postal>
86        <street>23 Corporate Plaza DR, Suite 280</street>
87        <city>Newport Beach</city>
88        <region>CA</region>
89        <code>92660</code>
90        <country>USA</country>
91      </postal>
92      <phone>+1-949-706-5300</phone>
93      <facsimile>+1-949-706-5305</facsimile>
94      <email></email>
95      <uri></uri>
96    </address>
97  </author>
99  <author initials="J." surname="Gettys" fullname="Jim Gettys">
100    <organization>One Laptop per Child</organization>
101    <address>
102      <postal>
103        <street>21 Oak Knoll Road</street>
104        <city>Carlisle</city>
105        <region>MA</region>
106        <code>01741</code>
107        <country>USA</country>
108      </postal>
109      <email></email>
110      <uri></uri>
111    </address>
112  </author>
114  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
115    <organization abbrev="HP">Hewlett-Packard Company</organization>
116    <address>
117      <postal>
118        <street>HP Labs, Large Scale Systems Group</street>
119        <street>1501 Page Mill Road, MS 1177</street>
120        <city>Palo Alto</city>
121        <region>CA</region>
122        <code>94304</code>
123        <country>USA</country>
124      </postal>
125      <email></email>
126    </address>
127  </author>
129  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
130    <organization abbrev="Microsoft">Microsoft Corporation</organization>
131    <address>
132      <postal>
133        <street>1 Microsoft Way</street>
134        <city>Redmond</city>
135        <region>WA</region>
136        <code>98052</code>
137        <country>USA</country>
138      </postal>
139      <email></email>
140    </address>
141  </author>
143  <author initials="L." surname="Masinter" fullname="Larry Masinter">
144    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
145    <address>
146      <postal>
147        <street>345 Park Ave</street>
148        <city>San Jose</city>
149        <region>CA</region>
150        <code>95110</code>
151        <country>USA</country>
152      </postal>
153      <email></email>
154      <uri></uri>
155    </address>
156  </author>
158  <author initials="P." surname="Leach" fullname="Paul J. Leach">
159    <organization abbrev="Microsoft">Microsoft Corporation</organization>
160    <address>
161      <postal>
162        <street>1 Microsoft Way</street>
163        <city>Redmond</city>
164        <region>WA</region>
165        <code>98052</code>
166      </postal>
167      <email></email>
168    </address>
169  </author>
171  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
172    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
173    <address>
174      <postal>
175        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
176        <street>The Stata Center, Building 32</street>
177        <street>32 Vassar Street</street>
178        <city>Cambridge</city>
179        <region>MA</region>
180        <code>02139</code>
181        <country>USA</country>
182      </postal>
183      <email></email>
184      <uri></uri>
185    </address>
186  </author>
188  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
189    <organization abbrev="W3C">World Wide Web Consortium</organization>
190    <address>
191      <postal>
192        <street>W3C / ERCIM</street>
193        <street>2004, rte des Lucioles</street>
194        <city>Sophia-Antipolis</city>
195        <region>AM</region>
196        <code>06902</code>
197        <country>France</country>
198      </postal>
199      <email></email>
200      <uri></uri>
201    </address>
202  </author>
204  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
205    <organization abbrev="greenbytes">greenbytes GmbH</organization>
206    <address>
207      <postal>
208        <street>Hafenweg 16</street>
209        <city>Muenster</city><region>NW</region><code>48155</code>
210        <country>Germany</country>
211      </postal>
212      <phone>+49 251 2807760</phone>   
213      <facsimile>+49 251 2807761</facsimile>   
214      <email></email>       
215      <uri></uri>     
216    </address>
217  </author>
219  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
223   The Hypertext Transfer Protocol (HTTP) is an application-level
224   protocol for distributed, collaborative, hypermedia information
225   systems. HTTP has been in use by the World Wide Web global information
226   initiative since 1990. This document is Part 2 of the seven-part specification
227   that defines the protocol referred to as "HTTP/1.1" and, taken together,
228   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
229   as expressed by request methods, request-header fields, response status codes,
230   and response-header fields.
234<note title="Editorial Note (To be removed by RFC Editor)">
235  <t>
236    Discussion of this draft should take place on the HTTPBIS working group
237    mailing list ( The current issues list is
238    at <eref target=""/>
239    and related documents (including fancy diffs) can be found at
240    <eref target=""/>.
241  </t>
242  <t>
243    This draft incorporates those issue resolutions that were either
244    collected in the original RFC2616 errata list (<eref target=""/>),
245    or which were agreed upon on the mailing list between October 2006 and
246    November 2007 (as published in "draft-lafon-rfc2616bis-03").
247  </t>
251<section title="Introduction" anchor="introduction">
253   This document defines HTTP/1.1 request and response semantics.  Each HTTP
254   message, as defined in &messaging;, is in the form of either a request or
255   a response.  An HTTP server listens on a connection for HTTP requests and
256   responds to each request, in the order received on that connection, with
257   one or more HTTP response messages.  This document defines the commonly
258   agreed upon semantics of the HTTP uniform interface, the intentions defined
259   by each request method, and the various response messages that might be
260   expected as a result of applying that method for the requested resource.
263   This document is currently disorganized in order to minimize the changes
264   between drafts and enable reviewers to see the smaller errata changes.
265   The next draft will reorganize the sections to better reflect the content.
266   In particular, the sections will be ordered according to the typical
267   processing of an HTTP request message (after message parsing): resource
268   mapping, general header fields, methods, request modifiers, response
269   status, and resource metadata.  The current mess reflects how widely
270   dispersed these topics and associated requirements had become in
271   <xref target="RFC2616"/>.
274<section title="Requirements" anchor="intro.requirements">
276   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
277   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
278   document are to be interpreted as described in <xref target="RFC2119"/>.
281   An implementation is not compliant if it fails to satisfy one or more
282   of the &MUST; or &REQUIRED; level requirements for the protocols it
283   implements. An implementation that satisfies all the &MUST; or &REQUIRED;
284   level and all the &SHOULD; level requirements for its protocols is said
285   to be "unconditionally compliant"; one that satisfies all the &MUST;
286   level requirements but not all the &SHOULD; level requirements for its
287   protocols is said to be "conditionally compliant."
292<section title="Notational Conventions and Generic Grammar" anchor="notation">
294  This specification uses the ABNF syntax defined in &notation-abnf; and
295  the core rules defined in &basic-rules;:
296  <cref anchor="abnf.dep">ABNF syntax and basic rules will be adopted from RFC 5234, see
297  <eref target=""/>.</cref>
299<figure><artwork type="abnf2616">
300  DIGIT         = &lt;DIGIT, defined in &basic-rules;&gt;
302<figure><artwork type="abnf2616">
303  comment       = &lt;comment, defined in &basic-rules;&gt;
304  quoted-string = &lt;quoted-string, defined in &basic-rules;&gt;
305  token         = &lt;token, defined in &basic-rules;&gt;
308  The ABNF rules below are defined in other parts:
310<figure><artwork type="abnf2616">
311  absoluteURI   = &lt;absoluteURI, defined in &general-syntax;&gt;
312  Accept        = &lt;Accept, defined in &header-accept;&gt;
313  Accept-Charset =
314             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
315  Accept-Encoding =
316             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
317  Accept-Language =
318             &lt;Accept-Language, defined in &header-accept-language;&gt;
319  Accept-Ranges = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
320  Age           = &lt;Age, defined in &header-age;&gt;
321  Authorization = &lt;Authorization, defined in &header-authorization;&gt;
322  delta-seconds = &lt;delta-seconds, defined in &header-age;&gt;
323  ETag          = &lt;ETag, defined in &header-etag;&gt;
324  fragment      = &lt;fragment, defined in &general-syntax;&gt;
325  HTTP-date     = &lt;HTTP-date, defined in &full-date;&gt;
326  Host          = &lt;Host, defined in &header-host;&gt;
327  If-Match      = &lt;If-Match, defined in &header-if-match;&gt;
328  If-Modified-Since =
329             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
330  If-None-Match = &lt;If-None-Match, defined in &header-if-none-match;&gt;
331  If-Range      = &lt;If-Range, defined in &header-if-range;&gt;
332  If-Unmodified-Since =
333             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
334  product       = &lt;product, defined in &product-tokens;&gt;
335  Proxy-Authenticate =
336             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
337  Proxy-Authorization =
338             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
339  Range         = &lt;Range, defined in &header-range;&gt;
340  relativeURI   = &lt;relativeURI, defined in &general-syntax;&gt;
341  TE            = &lt;TE, defined in &header-te;&gt;
342  Vary          = &lt;Vary, defined in &header-vary;&gt;
343  WWW-Authenticate =
344             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
348<section title="Method" anchor="method">
350   The Method  token indicates the method to be performed on the
351   resource identified by the Request-URI. The method is case-sensitive.
353<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
354  Method         = "OPTIONS"                ; <xref target="OPTIONS"/>
355                 | "GET"                    ; <xref target="GET"/>
356                 | "HEAD"                   ; <xref target="HEAD"/>
357                 | "POST"                   ; <xref target="POST"/>
358                 | "PUT"                    ; <xref target="PUT"/>
359                 | "DELETE"                 ; <xref target="DELETE"/>
360                 | "TRACE"                  ; <xref target="TRACE"/>
361                 | "CONNECT"                ; <xref target="CONNECT"/>
362                 | extension-method
363  extension-method = token
366   The list of methods allowed by a resource can be specified in an
367   Allow header field (<xref target="header.allow"/>). The return code of the response
368   always notifies the client whether a method is currently allowed on a
369   resource, since the set of allowed methods can change dynamically. An
370   origin server &SHOULD; return the status code 405 (Method Not Allowed)
371   if the method is known by the origin server but not allowed for the
372   requested resource, and 501 (Not Implemented) if the method is
373   unrecognized or not implemented by the origin server. The methods GET
374   and HEAD &MUST; be supported by all general-purpose servers. All other
375   methods are &OPTIONAL;; however, if the above methods are implemented,
376   they &MUST; be implemented with the same semantics as those specified
377   in <xref target="method.definitions"/>.
381<section title="Request Header Fields" anchor="request.header.fields">
383   The request-header fields allow the client to pass additional
384   information about the request, and about the client itself, to the
385   server. These fields act as request modifiers, with semantics
386   equivalent to the parameters on a programming language method
387   invocation.
389<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
390  request-header = Accept                   ; &header-accept;
391                 | Accept-Charset           ; &header-accept-charset;
392                 | Accept-Encoding          ; &header-accept-encoding;
393                 | Accept-Language          ; &header-accept-language;
394                 | Authorization            ; &header-authorization;
395                 | Expect                   ; <xref target="header.expect"/>
396                 | From                     ; <xref target="header.from"/>
397                 | Host                     ; &header-host;
398                 | If-Match                 ; &header-if-match;
399                 | If-Modified-Since        ; &header-if-modified-since;
400                 | If-None-Match            ; &header-if-none-match;
401                 | If-Range                 ; &header-if-range;
402                 | If-Unmodified-Since      ; &header-if-unmodified-since;
403                 | Max-Forwards             ; <xref target="header.max-forwards"/>
404                 | Proxy-Authorization      ; &header-proxy-authorization;
405                 | Range                    ; &header-range;
406                 | Referer                  ; <xref target="header.referer"/>
407                 | TE                       ; &header-te;
408                 | User-Agent               ; <xref target="header.user-agent"/>
411   Request-header field names can be extended reliably only in
412   combination with a change in the protocol version. However, new or
413   experimental header fields &MAY; be given the semantics of request-header
414   fields if all parties in the communication recognize them to
415   be request-header fields. Unrecognized header fields are treated as
416   entity-header fields.
420<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
422   The Status-Code element is a 3-digit integer result code of the
423   attempt to understand and satisfy the request. The status codes listed
424   below are defined in <xref target=""/>.
425   The Reason-Phrase is intended to give a short
426   textual description of the Status-Code. The Status-Code is intended
427   for use by automata and the Reason-Phrase is intended for the human
428   user. The client is not required to examine or display the Reason-Phrase.
431   The individual values of the numeric status codes defined for
432   HTTP/1.1, and an example set of corresponding Reason-Phrase's, are
433   presented below. The reason phrases listed here are only
434   recommendations -- they &MAY; be replaced by local equivalents without
435   affecting the protocol.
437<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"/>
438  Status-Code    =
439         "100"  ; <xref target="status.100"/>: Continue
440       | "101"  ; <xref target="status.101"/>: Switching Protocols
441       | "200"  ; <xref target="status.200"/>: OK
442       | "201"  ; <xref target="status.201"/>: Created
443       | "202"  ; <xref target="status.202"/>: Accepted
444       | "203"  ; <xref target="status.203"/>: Non-Authoritative Information
445       | "204"  ; <xref target="status.204"/>: No Content
446       | "205"  ; <xref target="status.205"/>: Reset Content
447       | "206"  ; <xref target="status.206"/>: Partial Content
448       | "300"  ; <xref target="status.300"/>: Multiple Choices
449       | "301"  ; <xref target="status.301"/>: Moved Permanently
450       | "302"  ; <xref target="status.302"/>: Found
451       | "303"  ; <xref target="status.303"/>: See Other
452       | "304"  ; <xref target="status.304"/>: Not Modified
453       | "305"  ; <xref target="status.305"/>: Use Proxy
454       | "307"  ; <xref target="status.307"/>: Temporary Redirect
455       | "400"  ; <xref target="status.400"/>: Bad Request
456       | "401"  ; <xref target="status.401"/>: Unauthorized
457       | "402"  ; <xref target="status.402"/>: Payment Required
458       | "403"  ; <xref target="status.403"/>: Forbidden
459       | "404"  ; <xref target="status.404"/>: Not Found
460       | "405"  ; <xref target="status.405"/>: Method Not Allowed
461       | "406"  ; <xref target="status.406"/>: Not Acceptable
462       | "407"  ; <xref target="status.407"/>: Proxy Authentication Required
463       | "408"  ; <xref target="status.408"/>: Request Time-out
464       | "409"  ; <xref target="status.409"/>: Conflict
465       | "410"  ; <xref target="status.410"/>: Gone
466       | "411"  ; <xref target="status.411"/>: Length Required
467       | "412"  ; <xref target="status.412"/>: Precondition Failed
468       | "413"  ; <xref target="status.413"/>: Request Entity Too Large
469       | "414"  ; <xref target="status.414"/>: Request-URI Too Large
470       | "415"  ; <xref target="status.415"/>: Unsupported Media Type
471       | "416"  ; <xref target="status.416"/>: Requested range not satisfiable
472       | "417"  ; <xref target="status.417"/>: Expectation Failed
473       | "500"  ; <xref target="status.500"/>: Internal Server Error
474       | "501"  ; <xref target="status.501"/>: Not Implemented
475       | "502"  ; <xref target="status.502"/>: Bad Gateway
476       | "503"  ; <xref target="status.503"/>: Service Unavailable
477       | "504"  ; <xref target="status.504"/>: Gateway Time-out
478       | "505"  ; <xref target="status.505"/>: HTTP Version not supported
479       | extension-code
481  extension-code = 3DIGIT
482  Reason-Phrase  = *&lt;TEXT, excluding CR, LF&gt;
485   HTTP status codes are extensible. HTTP applications are not required
486   to understand the meaning of all registered status codes, though such
487   understanding is obviously desirable. However, applications &MUST;
488   understand the class of any status code, as indicated by the first
489   digit, and treat any unrecognized response as being equivalent to the
490   x00 status code of that class, with the exception that an
491   unrecognized response &MUST-NOT; be cached. For example, if an
492   unrecognized status code of 431 is received by the client, it can
493   safely assume that there was something wrong with its request and
494   treat the response as if it had received a 400 status code. In such
495   cases, user agents &SHOULD; present to the user the entity returned
496   with the response, since that entity is likely to include human-readable
497   information which will explain the unusual status.
501<section title="Response Header Fields" anchor="response.header.fields">
503   The response-header fields allow the server to pass additional
504   information about the response which cannot be placed in the Status-Line.
505   These header fields give information about the server and about
506   further access to the resource identified by the Request-URI.
508<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
509  response-header = Accept-Ranges           ; &header-accept-ranges;
510                  | Age                     ; &header-age;
511                  | ETag                    ; &header-etag;
512                  | Location                ; <xref target="header.location"/>
513                  | Proxy-Authenticate      ; &header-proxy-authenticate;
514                  | Retry-After             ; <xref target="header.retry-after"/>
515                  | Server                  ; <xref target="header.server"/>
516                  | Vary                    ; &header-vary;
517                  | WWW-Authenticate        ; &header-www-authenticate;
520   Response-header field names can be extended reliably only in
521   combination with a change in the protocol version. However, new or
522   experimental header fields &MAY; be given the semantics of response-header
523   fields if all parties in the communication recognize them to
524   be response-header fields. Unrecognized header fields are treated as
525   entity-header fields.
529<section title="Entity" anchor="entity">
531   Request and Response messages &MAY; transfer an entity if not otherwise
532   restricted by the request method or response status code. An entity
533   consists of entity-header fields and an entity-body, although some
534   responses will only include the entity-headers. HTTP entity-body and
535   entity-header fields are defined in &payload;.
538   An entity-body is only present in a message when a message-body is
539   present, as described in &message-body;. The entity-body is obtained
540   from the message-body by decoding any Transfer-Encoding that might
541   have been applied to ensure safe and proper transfer of the message.
546<section title="Method Definitions" anchor="method.definitions">
548   The set of common methods for HTTP/1.1 is defined below. Although
549   this set can be expanded, additional methods cannot be assumed to
550   share the same semantics for separately extended clients and servers.
553<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
555<section title="Safe Methods" anchor="safe.methods">
557   Implementors should be aware that the software represents the user in
558   their interactions over the Internet, and should be careful to allow
559   the user to be aware of any actions they might take which may have an
560   unexpected significance to themselves or others.
563   In particular, the convention has been established that the GET and
564   HEAD methods &SHOULD-NOT;  have the significance of taking an action
565   other than retrieval. These methods ought to be considered "safe".
566   This allows user agents to represent other methods, such as POST, PUT
567   and DELETE, in a special way, so that the user is made aware of the
568   fact that a possibly unsafe action is being requested.
571   Naturally, it is not possible to ensure that the server does not
572   generate side-effects as a result of performing a GET request; in
573   fact, some dynamic resources consider that a feature. The important
574   distinction here is that the user did not request the side-effects,
575   so therefore cannot be held accountable for them.
579<section title="Idempotent Methods" anchor="idempotent.methods">
581   Methods can also have the property of "idempotence" in that (aside
582   from error or expiration issues) the side-effects of N &gt; 0 identical
583   requests is the same as for a single request. The methods GET, HEAD,
584   PUT and DELETE share this property. Also, the methods OPTIONS and
585   TRACE &SHOULD-NOT;  have side effects, and so are inherently idempotent.
588   However, it is possible that a sequence of several requests is non-idempotent,
589   even if all of the methods executed in that sequence are
590   idempotent. (A sequence is idempotent if a single execution of the
591   entire sequence always yields a result that is not changed by a
592   reexecution of all, or part, of that sequence.) For example, a
593   sequence is non-idempotent if its result depends on a value that is
594   later modified in the same sequence.
597   A sequence that never has side effects is idempotent, by definition
598   (provided that no concurrent operations are being executed on the
599   same set of resources).
604<section title="OPTIONS" anchor="OPTIONS">
605  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
606  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
608   The OPTIONS method represents a request for information about the
609   communication options available on the request/response chain
610   identified by the Request-URI. This method allows the client to
611   determine the options and/or requirements associated with a resource,
612   or the capabilities of a server, without implying a resource action
613   or initiating a resource retrieval.
616   Responses to this method are not cacheable.
619   If the OPTIONS request includes an entity-body (as indicated by the
620   presence of Content-Length or Transfer-Encoding), then the media type
621   &MUST; be indicated by a Content-Type field. Although this
622   specification does not define any use for such a body, future
623   extensions to HTTP might use the OPTIONS body to make more detailed
624   queries on the server. A server that does not support such an
625   extension &MAY; discard the request body.
628   If the Request-URI is an asterisk ("*"), the OPTIONS request is
629   intended to apply to the server in general rather than to a specific
630   resource. Since a server's communication options typically depend on
631   the resource, the "*" request is only useful as a "ping" or "no-op"
632   type of method; it does nothing beyond allowing the client to test
633   the capabilities of the server. For example, this can be used to test
634   a proxy for HTTP/1.1 compliance (or lack thereof).
637   If the Request-URI is not an asterisk, the OPTIONS request applies
638   only to the options that are available when communicating with that
639   resource.
642   A 200 response &SHOULD; include any header fields that indicate
643   optional features implemented by the server and applicable to that
644   resource (e.g., Allow), possibly including extensions not defined by
645   this specification. The response body, if any, &SHOULD; also include
646   information about the communication options. The format for such a
647   body is not defined by this specification, but might be defined by
648   future extensions to HTTP. Content negotiation &MAY; be used to select
649   the appropriate response format. If no response body is included, the
650   response &MUST; include a Content-Length field with a field-value of
651   "0".
654   The Max-Forwards request-header field &MAY; be used to target a
655   specific proxy in the request chain. When a proxy receives an OPTIONS
656   request on an absoluteURI for which request forwarding is permitted,
657   the proxy &MUST; check for a Max-Forwards field. If the Max-Forwards
658   field-value is zero ("0"), the proxy &MUST-NOT; forward the message;
659   instead, the proxy &SHOULD; respond with its own communication options.
660   If the Max-Forwards field-value is an integer greater than zero, the
661   proxy &MUST; decrement the field-value when it forwards the request. If
662   no Max-Forwards field is present in the request, then the forwarded
663   request &MUST-NOT; include a Max-Forwards field.
667<section title="GET" anchor="GET">
668  <iref primary="true" item="GET method" x:for-anchor=""/>
669  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
671   The GET method means retrieve whatever information (in the form of an
672   entity) is identified by the Request-URI. If the Request-URI refers
673   to a data-producing process, it is the produced data which shall be
674   returned as the entity in the response and not the source text of the
675   process, unless that text happens to be the output of the process.
678   The semantics of the GET method change to a "conditional GET" if the
679   request message includes an If-Modified-Since, If-Unmodified-Since,
680   If-Match, If-None-Match, or If-Range header field. A conditional GET
681   method requests that the entity be transferred only under the
682   circumstances described by the conditional header field(s). The
683   conditional GET method is intended to reduce unnecessary network
684   usage by allowing cached entities to be refreshed without requiring
685   multiple requests or transferring data already held by the client.
688   The semantics of the GET method change to a "partial GET" if the
689   request message includes a Range header field. A partial GET requests
690   that only part of the entity be transferred, as described in &header-range;.
691   The partial GET method is intended to reduce unnecessary
692   network usage by allowing partially-retrieved entities to be
693   completed without transferring data already held by the client.
696   The response to a GET request is cacheable if and only if it meets
697   the requirements for HTTP caching described in &caching;.
700   See <xref target=""/> for security considerations when used for forms.
704<section title="HEAD" anchor="HEAD">
705  <iref primary="true" item="HEAD method" x:for-anchor=""/>
706  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
708   The HEAD method is identical to GET except that the server &MUST-NOT;
709   return a message-body in the response. The metainformation contained
710   in the HTTP headers in response to a HEAD request &SHOULD; be identical
711   to the information sent in response to a GET request. This method can
712   be used for obtaining metainformation about the entity implied by the
713   request without transferring the entity-body itself. This method is
714   often used for testing hypertext links for validity, accessibility,
715   and recent modification.
718   The response to a HEAD request &MAY; be cacheable in the sense that the
719   information contained in the response &MAY; be used to update a
720   previously cached entity from that resource. If the new field values
721   indicate that the cached entity differs from the current entity (as
722   would be indicated by a change in Content-Length, Content-MD5, ETag
723   or Last-Modified), then the cache &MUST; treat the cache entry as
724   stale.
728<section title="POST" anchor="POST">
729  <iref primary="true" item="POST method" x:for-anchor=""/>
730  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
732   The POST method is used to request that the origin server accept the
733   entity enclosed in the request as data to be processed by the resource
734   identified by the Request-URI in the Request-Line. POST is designed
735   to allow a uniform method to cover the following functions:
736  <list style="symbols">
737    <t>
738      Annotation of existing resources;
739    </t>
740    <t>
741        Posting a message to a bulletin board, newsgroup, mailing list,
742        or similar group of articles;
743    </t>
744    <t>
745        Providing a block of data, such as the result of submitting a
746        form, to a data-handling process;
747    </t>
748    <t>
749        Extending a database through an append operation.
750    </t>
751  </list>
754   The actual function performed by the POST method is determined by the
755   server and is usually dependent on the Request-URI.
758   The action performed by the POST method might not result in a
759   resource that can be identified by a URI. In this case, either 200
760   (OK) or 204 (No Content) is the appropriate response status,
761   depending on whether or not the response includes an entity that
762   describes the result.
765   If a resource has been created on the origin server, the response
766   &SHOULD; be 201 (Created) and contain an entity which describes the
767   status of the request and refers to the new resource, and a Location
768   header (see <xref target="header.location"/>).
771   Responses to this method are not cacheable, unless the response
772   includes appropriate Cache-Control or Expires header fields. However,
773   the 303 (See Other) response can be used to direct the user agent to
774   retrieve a cacheable resource.
778<section title="PUT" anchor="PUT">
779  <iref primary="true" item="PUT method" x:for-anchor=""/>
780  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
782   The PUT method requests that the enclosed entity be stored under the
783   supplied Request-URI. If the Request-URI refers to an already
784   existing resource, the enclosed entity &SHOULD; be considered as a
785   modified version of the one residing on the origin server. If the
786   Request-URI does not point to an existing resource, and that URI is
787   capable of being defined as a new resource by the requesting user
788   agent, the origin server can create the resource with that URI. If a
789   new resource is created at the Request-URI, the origin server &MUST;
790         inform the user agent
791   via the 201 (Created) response. If an existing resource is modified,
792   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
793   to indicate successful completion of the request. If the resource
794   could not be created or modified with the Request-URI, an appropriate
795   error response &SHOULD; be given that reflects the nature of the
796   problem. The recipient of the entity &MUST-NOT; ignore any Content-*
797   (e.g. Content-Range) headers that it does not understand or implement
798   and &MUST; return a 501 (Not Implemented) response in such cases.
801   If the request passes through a cache and the Request-URI identifies
802   one or more currently cached entities, those entries &SHOULD; be
803   treated as stale. Responses to this method are not cacheable.
806   The fundamental difference between the POST and PUT requests is
807   reflected in the different meaning of the Request-URI. The URI in a
808   POST request identifies the resource that will handle the enclosed
809   entity. That resource might be a data-accepting process, a gateway to
810   some other protocol, or a separate entity that accepts annotations.
811   In contrast, the URI in a PUT request identifies the entity enclosed
812   with the request -- the user agent knows what URI is intended and the
813   server &MUST-NOT; attempt to apply the request to some other resource.
814   If the server desires that the request be applied to a different URI,
815   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
816   then make its own decision regarding whether or not to redirect the
817   request.
820   A single resource &MAY; be identified by many different URIs. For
821   example, an article might have a URI for identifying "the current
822   version" which is separate from the URI identifying each particular
823   version. In this case, a PUT request on a general URI might result in
824   several other URIs being defined by the origin server.
827   HTTP/1.1 does not define how a PUT method affects the state of an
828   origin server.
831   Unless otherwise specified for a particular entity-header, the
832   entity-headers in the PUT request &SHOULD; be applied to the resource
833   created or modified by the PUT.
837<section title="DELETE" anchor="DELETE">
838  <iref primary="true" item="DELETE method" x:for-anchor=""/>
839  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
841   The DELETE method requests that the origin server delete the resource
842   identified by the Request-URI. This method &MAY; be overridden by human
843   intervention (or other means) on the origin server. The client cannot
844   be guaranteed that the operation has been carried out, even if the
845   status code returned from the origin server indicates that the action
846   has been completed successfully. However, the server &SHOULD-NOT;
847   indicate success unless, at the time the response is given, it
848   intends to delete the resource or move it to an inaccessible
849   location.
852   A successful response &SHOULD; be 200 (OK) if the response includes an
853   entity describing the status, 202 (Accepted) if the action has not
854   yet been enacted, or 204 (No Content) if the action has been enacted
855   but the response does not include an entity.
858   If the request passes through a cache and the Request-URI identifies
859   one or more currently cached entities, those entries &SHOULD; be
860   treated as stale. Responses to this method are not cacheable.
864<section title="TRACE" anchor="TRACE">
865  <iref primary="true" item="TRACE method" x:for-anchor=""/>
866  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
868   The TRACE method is used to invoke a remote, application-layer loop-back
869   of the request message. The final recipient of the request
870   &SHOULD; reflect the message received back to the client as the
871   entity-body of a 200 (OK) response. The final recipient is either the
872   origin server or the first proxy or gateway to receive a Max-Forwards
873   value of zero (0) in the request (see <xref target="header.max-forwards"/>). A TRACE request
874   &MUST-NOT; include an entity.
877   TRACE allows the client to see what is being received at the other
878   end of the request chain and use that data for testing or diagnostic
879   information. The value of the Via header field (&header-via;) is of
880   particular interest, since it acts as a trace of the request chain.
881   Use of the Max-Forwards header field allows the client to limit the
882   length of the request chain, which is useful for testing a chain of
883   proxies forwarding messages in an infinite loop.
886   If the request is valid, the response &SHOULD; contain the entire
887   request message in the entity-body, with a Content-Type of
888   "message/http". Responses to this method &MUST-NOT; be cached.
892<section title="CONNECT" anchor="CONNECT">
893  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
894  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
896   This specification reserves the method name CONNECT for use with a
897   proxy that can dynamically switch to being a tunnel (e.g. SSL
898   tunneling <xref target="Luo1998"/>).
904<section title="Status Code Definitions" anchor="">
906   Each Status-Code is described below, including a description of which
907   method(s) it can follow and any metainformation required in the
908   response.
911<section title="Informational 1xx" anchor="status.1xx">
913   This class of status code indicates a provisional response,
914   consisting only of the Status-Line and optional headers, and is
915   terminated by an empty line. There are no required headers for this
916   class of status code. Since HTTP/1.0 did not define any 1xx status
917   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
918   except under experimental conditions.
921   A client &MUST; be prepared to accept one or more 1xx status responses
922   prior to a regular response, even if the client does not expect a 100
923   (Continue) status message. Unexpected 1xx status responses &MAY; be
924   ignored by a user agent.
927   Proxies &MUST; forward 1xx responses, unless the connection between the
928   proxy and its client has been closed, or unless the proxy itself
929   requested the generation of the 1xx response. (For example, if a
930   proxy adds a "Expect: 100-continue" field when it forwards a request,
931   then it need not forward the corresponding 100 (Continue)
932   response(s).)
935<section title="100 Continue" anchor="status.100">
936  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
937  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
939   The client &SHOULD; continue with its request. This interim response is
940   used to inform the client that the initial part of the request has
941   been received and has not yet been rejected by the server. The client
942   &SHOULD; continue by sending the remainder of the request or, if the
943   request has already been completed, ignore this response. The server
944   &MUST; send a final response after the request has been completed. See
945   &use100; for detailed discussion of the use and handling of this
946   status code.
950<section title="101 Switching Protocols" anchor="status.101">
951  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
952  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
954   The server understands and is willing to comply with the client's
955   request, via the Upgrade message header field (&header-upgrade;), for a
956   change in the application protocol being used on this connection. The
957   server will switch protocols to those defined by the response's
958   Upgrade header field immediately after the empty line which
959   terminates the 101 response.
962   The protocol &SHOULD; be switched only when it is advantageous to do
963   so. For example, switching to a newer version of HTTP is advantageous
964   over older versions, and switching to a real-time, synchronous
965   protocol might be advantageous when delivering resources that use
966   such features.
971<section title="Successful 2xx" anchor="status.2xx">
973   This class of status code indicates that the client's request was
974   successfully received, understood, and accepted.
977<section title="200 OK" anchor="status.200">
978  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
979  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
981   The request has succeeded. The information returned with the response
982   is dependent on the method used in the request, for example:
983  <list style="hanging">
984    <t hangText="GET">
985          an entity corresponding to the requested resource is sent in
986          the response;
987    </t>
988    <t hangText="HEAD">
989          the entity-header fields corresponding to the requested
990          resource are sent in the response without any message-body;
991    </t>
992    <t hangText="POST">
993      an entity describing or containing the result of the action;
994    </t>
995    <t hangText="TRACE">
996      an entity containing the request message as received by the
997      end server.
998    </t>
999  </list>
1003<section title="201 Created" anchor="status.201">
1004  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1005  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1007   The request has been fulfilled and resulted in a new resource being
1008   created. The newly created resource can be referenced by the URI(s)
1009   returned in the entity of the response, with the most specific URI
1010   for the resource given by a Location header field. The response
1011   &SHOULD; include an entity containing a list of resource
1012   characteristics and location(s) from which the user or user agent can
1013   choose the one most appropriate. The entity format is specified by
1014   the media type given in the Content-Type header field. The origin
1015   server &MUST; create the resource before returning the 201 status code.
1016   If the action cannot be carried out immediately, the server &SHOULD;
1017   respond with 202 (Accepted) response instead.
1020   A 201 response &MAY; contain an ETag response header field indicating
1021   the current value of the entity tag for the requested variant just
1022   created, see &header-etag;.
1026<section title="202 Accepted" anchor="status.202">
1027  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1028  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1030   The request has been accepted for processing, but the processing has
1031   not been completed.  The request might or might not eventually be
1032   acted upon, as it might be disallowed when processing actually takes
1033   place. There is no facility for re-sending a status code from an
1034   asynchronous operation such as this.
1037   The 202 response is intentionally non-committal. Its purpose is to
1038   allow a server to accept a request for some other process (perhaps a
1039   batch-oriented process that is only run once per day) without
1040   requiring that the user agent's connection to the server persist
1041   until the process is completed. The entity returned with this
1042   response &SHOULD; include an indication of the request's current status
1043   and either a pointer to a status monitor or some estimate of when the
1044   user can expect the request to be fulfilled.
1048<section title="203 Non-Authoritative Information" anchor="status.203">
1049  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1050  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1052   The returned metainformation in the entity-header is not the
1053   definitive set as available from the origin server, but is gathered
1054   from a local or a third-party copy. The set presented &MAY; be a subset
1055   or superset of the original version. For example, including local
1056   annotation information about the resource might result in a superset
1057   of the metainformation known by the origin server. Use of this
1058   response code is not required and is only appropriate when the
1059   response would otherwise be 200 (OK).
1063<section title="204 No Content" anchor="status.204">
1064  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1065  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1067   The server has fulfilled the request but does not need to return an
1068   entity-body, and might want to return updated metainformation. The
1069   response &MAY; include new or updated metainformation in the form of
1070   entity-headers, which if present &SHOULD; be associated with the
1071   requested variant.
1074   If the client is a user agent, it &SHOULD-NOT;  change its document view
1075   from that which caused the request to be sent. This response is
1076   primarily intended to allow input for actions to take place without
1077   causing a change to the user agent's active document view, although
1078   any new or updated metainformation &SHOULD; be applied to the document
1079   currently in the user agent's active view.
1082   The 204 response &MUST-NOT; include a message-body, and thus is always
1083   terminated by the first empty line after the header fields.
1087<section title="205 Reset Content" anchor="status.205">
1088  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1089  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1091   The server has fulfilled the request and the user agent &SHOULD; reset
1092   the document view which caused the request to be sent. This response
1093   is primarily intended to allow input for actions to take place via
1094   user input, followed by a clearing of the form in which the input is
1095   given so that the user can easily initiate another input action. The
1096   response &MUST-NOT; include an entity.
1100<section title="206 Partial Content" anchor="status.206">
1101  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1102  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1104   The server has fulfilled the partial GET request for the resource
1105   and the enclosed entity is a partial representation as defined in &range;.
1110<section title="Redirection 3xx" anchor="status.3xx">
1112   This class of status code indicates that further action needs to be
1113   taken by the user agent in order to fulfill the request.  The action
1114   required &MAY; be carried out by the user agent without interaction
1115   with the user if and only if the method used in the second request is
1116   GET or HEAD. A client &SHOULD; detect infinite redirection loops, since
1117   such loops generate network traffic for each redirection.
1118  <list><t>
1119      <x:h>Note:</x:h> previous versions of this specification recommended a
1120      maximum of five redirections. Content developers should be aware
1121      that there might be clients that implement such a fixed
1122      limitation.
1123  </t></list>
1126<section title="300 Multiple Choices" anchor="status.300">
1127  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1128  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1130   The requested resource corresponds to any one of a set of
1131   representations, each with its own specific location, and agent-driven
1132   negotiation information (&content-negotiation;) is being provided so that
1133   the user (or user agent) can select a preferred representation and
1134   redirect its request to that location.
1137   Unless it was a HEAD request, the response &SHOULD; include an entity
1138   containing a list of resource characteristics and location(s) from
1139   which the user or user agent can choose the one most appropriate. The
1140   entity format is specified by the media type given in the Content-Type
1141   header field. Depending upon the format and the capabilities of
1142   the user agent, selection of the most appropriate choice &MAY; be
1143   performed automatically. However, this specification does not define
1144   any standard for such automatic selection.
1147   If the server has a preferred choice of representation, it &SHOULD;
1148   include the specific URI for that representation in the Location
1149   field; user agents &MAY; use the Location field value for automatic
1150   redirection. This response is cacheable unless indicated otherwise.
1154<section title="301 Moved Permanently" anchor="status.301">
1155  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1156  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1158   The requested resource has been assigned a new permanent URI and any
1159   future references to this resource &SHOULD; use one of the returned
1160   URIs.  Clients with link editing capabilities ought to automatically
1161   re-link references to the Request-URI to one or more of the new
1162   references returned by the server, where possible. This response is
1163   cacheable unless indicated otherwise.
1166   The new permanent URI &SHOULD; be given by the Location field in the
1167   response. Unless the request method was HEAD, the entity of the
1168   response &SHOULD; contain a short hypertext note with a hyperlink to
1169   the new URI(s).
1172   If the 301 status code is received in response to a request method
1173   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1174   then the request &MAY; be automatically redirected by the user agent without
1175   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1176   request unless it can be confirmed by the user, since this might
1177   change the conditions under which the request was issued.
1178  <list><t>
1179      <x:h>Note:</x:h> When automatically redirecting a POST request after
1180      receiving a 301 status code, some existing HTTP/1.0 user agents
1181      will erroneously change it into a GET request.
1182  </t></list>
1186<section title="302 Found" anchor="status.302">
1187  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1188  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1190   The requested resource resides temporarily under a different URI.
1191   Since the redirection might be altered on occasion, the client &SHOULD;
1192   continue to use the Request-URI for future requests.  This response
1193   is only cacheable if indicated by a Cache-Control or Expires header
1194   field.
1197   The temporary URI &SHOULD; be given by the Location field in the
1198   response. Unless the request method was HEAD, the entity of the
1199   response &SHOULD; contain a short hypertext note with a hyperlink to
1200   the new URI(s).
1203   If the 302 status code is received in response to a request method
1204   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1205   then the request &MAY; be automatically redirected by the user agent without
1206   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1207   request unless it can be confirmed by the user, since this might
1208   change the conditions under which the request was issued.
1209  <list><t>
1210      <x:h>Note:</x:h> <xref target="RFC1945"/> and <xref target="RFC2068"/> specify that the client is not allowed
1211      to change the method on the redirected request.  However, most
1212      existing user agent implementations treat 302 as if it were a 303
1213      response, performing a GET on the Location field-value regardless
1214      of the original request method. The status codes 303 and 307 have
1215      been added for servers that wish to make unambiguously clear which
1216      kind of reaction is expected of the client.
1217  </t></list>
1221<section title="303 See Other" anchor="status.303">
1222  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1223  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1225   The response to the request can be found under a different URI and
1226   &SHOULD; be retrieved using a GET method on that resource. This method
1227   exists primarily to allow the output of a POST-activated script to
1228   redirect the user agent to a selected resource. The new URI is not a
1229   substitute reference for the originally requested resource. The 303
1230   response &MUST-NOT; be cached, but the response to the second
1231   (redirected) request might be cacheable.
1234   The different URI &SHOULD; be given by the Location field in the
1235   response. Unless the request method was HEAD, the entity of the
1236   response &SHOULD; contain a short hypertext note with a hyperlink to
1237   the new URI(s).
1238  <list><t>
1239      <x:h>Note:</x:h> Many pre-HTTP/1.1 user agents do not understand the 303
1240      status. When interoperability with such clients is a concern, the
1241      302 status code may be used instead, since most user agents react
1242      to a 302 response as described here for 303.
1243  </t></list>
1247<section title="304 Not Modified" anchor="status.304">
1248  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1249  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1251   The response to the request has not been modified since the conditions
1252   indicated by the client's conditional GET request, as defined in &conditional;.
1256<section title="305 Use Proxy" anchor="status.305">
1257  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1258  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1260   The requested resource &MUST; be accessed through the proxy given by
1261   the Location field. The Location field gives the URI of the proxy.
1262   The recipient is expected to repeat this single request via the
1263   proxy. 305 responses &MUST; only be generated by origin servers.
1264  <list><t>
1265      <x:h>Note:</x:h> <xref target="RFC2068"/> was not clear that 305 was intended to redirect a
1266      single request, and to be generated by origin servers only.  Not
1267      observing these limitations has significant security consequences.
1268  </t></list>
1272<section title="306 (Unused)" anchor="status.306">
1273  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1274  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1276   The 306 status code was used in a previous version of the
1277   specification, is no longer used, and the code is reserved.
1281<section title="307 Temporary Redirect" anchor="status.307">
1282  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1283  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1285   The requested resource resides temporarily under a different URI.
1286   Since the redirection &MAY; be altered on occasion, the client &SHOULD;
1287   continue to use the Request-URI for future requests.  This response
1288   is only cacheable if indicated by a Cache-Control or Expires header
1289   field.
1292   The temporary URI &SHOULD; be given by the Location field in the
1293   response. Unless the request method was HEAD, the entity of the
1294   response &SHOULD; contain a short hypertext note with a hyperlink to
1295   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1296   understand the 307 status. Therefore, the note &SHOULD; contain the
1297   information necessary for a user to repeat the original request on
1298   the new URI.
1301   If the 307 status code is received in response to a request method
1302   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1303   then the request &MAY; be automatically redirected by the user agent without
1304   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1305   request unless it can be confirmed by the user, since this might
1306   change the conditions under which the request was issued.
1311<section title="Client Error 4xx" anchor="status.4xx">
1313   The 4xx class of status code is intended for cases in which the
1314   client seems to have erred. Except when responding to a HEAD request,
1315   the server &SHOULD; include an entity containing an explanation of the
1316   error situation, and whether it is a temporary or permanent
1317   condition. These status codes are applicable to any request method.
1318   User agents &SHOULD; display any included entity to the user.
1321   If the client is sending data, a server implementation using TCP
1322   &SHOULD; be careful to ensure that the client acknowledges receipt of
1323   the packet(s) containing the response, before the server closes the
1324   input connection. If the client continues sending data to the server
1325   after the close, the server's TCP stack will send a reset packet to
1326   the client, which may erase the client's unacknowledged input buffers
1327   before they can be read and interpreted by the HTTP application.
1330<section title="400 Bad Request" anchor="status.400">
1331  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1332  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1334   The request could not be understood by the server due to malformed
1335   syntax. The client &SHOULD-NOT;  repeat the request without
1336   modifications.
1340<section title="401 Unauthorized" anchor="status.401">
1341  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1342  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1344   The request requires user authentication (see &auth;).
1348<section title="402 Payment Required" anchor="status.402">
1349  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1350  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1352   This code is reserved for future use.
1356<section title="403 Forbidden" anchor="status.403">
1357  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1358  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1360   The server understood the request, but is refusing to fulfill it.
1361   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1362   If the request method was not HEAD and the server wishes to make
1363   public why the request has not been fulfilled, it &SHOULD; describe the
1364   reason for the refusal in the entity.  If the server does not wish to
1365   make this information available to the client, the status code 404
1366   (Not Found) can be used instead.
1370<section title="404 Not Found" anchor="status.404">
1371  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1372  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1374   The server has not found anything matching the Request-URI. No
1375   indication is given of whether the condition is temporary or
1376   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1377   knows, through some internally configurable mechanism, that an old
1378   resource is permanently unavailable and has no forwarding address.
1379   This status code is commonly used when the server does not wish to
1380   reveal exactly why the request has been refused, or when no other
1381   response is applicable.
1385<section title="405 Method Not Allowed" anchor="status.405">
1386  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1387  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1389   The method specified in the Request-Line is not allowed for the
1390   resource identified by the Request-URI. The response &MUST; include an
1391   Allow header containing a list of valid methods for the requested
1392   resource.
1396<section title="406 Not Acceptable" anchor="status.406">
1397  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1398  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1400   The resource identified by the request is only capable of generating
1401   response entities which have content characteristics not acceptable
1402   according to the accept headers sent in the request.
1405   Unless it was a HEAD request, the response &SHOULD; include an entity
1406   containing a list of available entity characteristics and location(s)
1407   from which the user or user agent can choose the one most
1408   appropriate. The entity format is specified by the media type given
1409   in the Content-Type header field. Depending upon the format and the
1410   capabilities of the user agent, selection of the most appropriate
1411   choice &MAY; be performed automatically. However, this specification
1412   does not define any standard for such automatic selection.
1413  <list><t>
1414      <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1415      not acceptable according to the accept headers sent in the
1416      request. In some cases, this may even be preferable to sending a
1417      406 response. User agents are encouraged to inspect the headers of
1418      an incoming response to determine if it is acceptable.
1419  </t></list>
1422   If the response could be unacceptable, a user agent &SHOULD;
1423   temporarily stop receipt of more data and query the user for a
1424   decision on further actions.
1428<section title="407 Proxy Authentication Required" anchor="status.407">
1429  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1430  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1432   This code is similar to 401 (Unauthorized), but indicates that the
1433   client must first authenticate itself with the proxy (see &auth;).
1437<section title="408 Request Timeout" anchor="status.408">
1438  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1439  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1441   The client did not produce a request within the time that the server
1442   was prepared to wait. The client &MAY; repeat the request without
1443   modifications at any later time.
1447<section title="409 Conflict" anchor="status.409">
1448  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1449  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1451   The request could not be completed due to a conflict with the current
1452   state of the resource. This code is only allowed in situations where
1453   it is expected that the user might be able to resolve the conflict
1454   and resubmit the request. The response body &SHOULD; include enough
1455   information for the user to recognize the source of the conflict.
1456   Ideally, the response entity would include enough information for the
1457   user or user agent to fix the problem; however, that might not be
1458   possible and is not required.
1461   Conflicts are most likely to occur in response to a PUT request. For
1462   example, if versioning were being used and the entity being PUT
1463   included changes to a resource which conflict with those made by an
1464   earlier (third-party) request, the server might use the 409 response
1465   to indicate that it can't complete the request. In this case, the
1466   response entity would likely contain a list of the differences
1467   between the two versions in a format defined by the response
1468   Content-Type.
1472<section title="410 Gone" anchor="status.410">
1473  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1474  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1476   The requested resource is no longer available at the server and no
1477   forwarding address is known. This condition is expected to be
1478   considered permanent. Clients with link editing capabilities &SHOULD;
1479   delete references to the Request-URI after user approval. If the
1480   server does not know, or has no facility to determine, whether or not
1481   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1482   used instead. This response is cacheable unless indicated otherwise.
1485   The 410 response is primarily intended to assist the task of web
1486   maintenance by notifying the recipient that the resource is
1487   intentionally unavailable and that the server owners desire that
1488   remote links to that resource be removed. Such an event is common for
1489   limited-time, promotional services and for resources belonging to
1490   individuals no longer working at the server's site. It is not
1491   necessary to mark all permanently unavailable resources as "gone" or
1492   to keep the mark for any length of time -- that is left to the
1493   discretion of the server owner.
1497<section title="411 Length Required" anchor="status.411">
1498  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1499  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1501   The server refuses to accept the request without a defined Content-Length.
1502   The client &MAY; repeat the request if it adds a valid
1503   Content-Length header field containing the length of the message-body
1504   in the request message.
1508<section title="412 Precondition Failed" anchor="status.412">
1509  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1510  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1512   The precondition given in one or more of the request-header fields
1513   evaluated to false when it was tested on the server, as defined in
1514   &conditional;.
1518<section title="413 Request Entity Too Large" anchor="status.413">
1519  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1520  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1522   The server is refusing to process a request because the request
1523   entity is larger than the server is willing or able to process. The
1524   server &MAY; close the connection to prevent the client from continuing
1525   the request.
1528   If the condition is temporary, the server &SHOULD; include a Retry-After
1529   header field to indicate that it is temporary and after what
1530   time the client &MAY; try again.
1534<section title="414 Request-URI Too Long" anchor="status.414">
1535  <iref primary="true" item="414 Request-URI Too Long (status code)" x:for-anchor=""/>
1536  <iref primary="true" item="Status Codes" subitem="414 Request-URI Too Long" x:for-anchor=""/>
1538   The server is refusing to service the request because the Request-URI
1539   is longer than the server is willing to interpret. This rare
1540   condition is only likely to occur when a client has improperly
1541   converted a POST request to a GET request with long query
1542   information, when the client has descended into a URI "black hole" of
1543   redirection (e.g., a redirected URI prefix that points to a suffix of
1544   itself), or when the server is under attack by a client attempting to
1545   exploit security holes present in some servers using fixed-length
1546   buffers for reading or manipulating the Request-URI.
1550<section title="415 Unsupported Media Type" anchor="status.415">
1551  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1552  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1554   The server is refusing to service the request because the entity of
1555   the request is in a format not supported by the requested resource
1556   for the requested method.
1560<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1561  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1562  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1564   The request included a Range request-header field (&header-range;) and none of
1565   the range-specifier values in this field overlap the current extent
1566   of the selected resource.
1570<section title="417 Expectation Failed" anchor="status.417">
1571  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1572  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1574   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1575   could not be met by this server, or, if the server is a proxy,
1576   the server has unambiguous evidence that the request could not be met
1577   by the next-hop server.
1582<section title="Server Error 5xx" anchor="status.5xx">
1584   Response status codes beginning with the digit "5" indicate cases in
1585   which the server is aware that it has erred or is incapable of
1586   performing the request. Except when responding to a HEAD request, the
1587   server &SHOULD; include an entity containing an explanation of the
1588   error situation, and whether it is a temporary or permanent
1589   condition. User agents &SHOULD; display any included entity to the
1590   user. These response codes are applicable to any request method.
1593<section title="500 Internal Server Error" anchor="status.500">
1594  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1595  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1597   The server encountered an unexpected condition which prevented it
1598   from fulfilling the request.
1602<section title="501 Not Implemented" anchor="status.501">
1603  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1604  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1606   The server does not support the functionality required to fulfill the
1607   request. This is the appropriate response when the server does not
1608   recognize the request method and is not capable of supporting it for
1609   any resource.
1613<section title="502 Bad Gateway" anchor="status.502">
1614  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1615  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1617   The server, while acting as a gateway or proxy, received an invalid
1618   response from the upstream server it accessed in attempting to
1619   fulfill the request.
1623<section title="503 Service Unavailable" anchor="status.503">
1624  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1625  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1627   The server is currently unable to handle the request due to a
1628   temporary overloading or maintenance of the server. The implication
1629   is that this is a temporary condition which will be alleviated after
1630   some delay. If known, the length of the delay &MAY; be indicated in a
1631   Retry-After header. If no Retry-After is given, the client &SHOULD;
1632   handle the response as it would for a 500 response.
1633  <list><t>
1634      <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1635      server must use it when becoming overloaded. Some servers may wish
1636      to simply refuse the connection.
1637  </t></list>
1641<section title="504 Gateway Timeout" anchor="status.504">
1642  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1643  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1645   The server, while acting as a gateway or proxy, did not receive a
1646   timely response from the upstream server specified by the URI (e.g.
1647   HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed
1648   to access in attempting to complete the request.
1649  <list><t>
1650      <x:h>Note:</x:h> Note to implementors: some deployed proxies are known to
1651      return 400 or 500 when DNS lookups time out.
1652  </t></list>
1656<section title="505 HTTP Version Not Supported" anchor="status.505">
1657  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1658  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
1660   The server does not support, or refuses to support, the protocol
1661   version that was used in the request message. The server is
1662   indicating that it is unable or unwilling to complete the request
1663   using the same major version as the client, as described in &http-version;,
1664   other than with this error message. The response &SHOULD; contain
1665   an entity describing why that version is not supported and what other
1666   protocols are supported by that server.
1674<section title="Header Field Definitions" anchor="header.fields">
1676   This section defines the syntax and semantics of HTTP/1.1 header fields
1677   related to request and response semantics.
1680   For entity-header fields, both sender and recipient refer to either the
1681   client or the server, depending on who sends and who receives the entity.
1684<section title="Allow" anchor="header.allow">
1685  <iref primary="true" item="Allow header" x:for-anchor=""/>
1686  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
1688      The Allow entity-header field lists the set of methods supported
1689      by the resource identified by the Request-URI. The purpose of this
1690      field is strictly to inform the recipient of valid methods
1691      associated with the resource. An Allow header field &MUST; be
1692      present in a 405 (Method Not Allowed) response.
1694<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/>
1695  Allow   = "Allow" ":" #Method
1698      Example of use:
1700<figure><artwork type="example">
1701       Allow: GET, HEAD, PUT
1704      This field cannot prevent a client from trying other methods.
1705      However, the indications given by the Allow header field value
1706      &SHOULD; be followed. The actual set of allowed methods is defined
1707      by the origin server at the time of each request.
1710      The Allow header field &MAY; be provided with a PUT request to
1711      recommend the methods to be supported by the new or modified
1712      resource. The server is not required to support these methods and
1713      &SHOULD; include an Allow header in the response giving the actual
1714      supported methods.
1717      A proxy &MUST-NOT; modify the Allow header field even if it does not
1718      understand all the methods specified, since the user agent might
1719      have other means of communicating with the origin server.
1723<section title="Expect" anchor="header.expect">
1724  <iref primary="true" item="Expect header" x:for-anchor=""/>
1725  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
1727   The Expect request-header field is used to indicate that particular
1728   server behaviors are required by the client.
1730<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"/>
1731  Expect       =  "Expect" ":" 1#expectation
1733  expectation  =  "100-continue" | expectation-extension
1734  expectation-extension =  token [ "=" ( token | quoted-string )
1735                           *expect-params ]
1736  expect-params =  ";" token [ "=" ( token | quoted-string ) ]
1739   A server that does not understand or is unable to comply with any of
1740   the expectation values in the Expect field of a request &MUST; respond
1741   with appropriate error status. The server &MUST; respond with a 417
1742   (Expectation Failed) status if any of the expectations cannot be met
1743   or, if there are other problems with the request, some other 4xx
1744   status.
1747   This header field is defined with extensible syntax to allow for
1748   future extensions. If a server receives a request containing an
1749   Expect field that includes an expectation-extension that it does not
1750   support, it &MUST; respond with a 417 (Expectation Failed) status.
1753   Comparison of expectation values is case-insensitive for unquoted
1754   tokens (including the 100-continue token), and is case-sensitive for
1755   quoted-string expectation-extensions.
1758   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
1759   return a 417 (Expectation Failed) status if it receives a request
1760   with an expectation that it cannot meet. However, the Expect
1761   request-header itself is end-to-end; it &MUST; be forwarded if the
1762   request is forwarded.
1765   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1766   Expect header.
1769   See &use100; for the use of the 100 (Continue) status.
1773<section title="From" anchor="header.from">
1774  <iref primary="true" item="From header" x:for-anchor=""/>
1775  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
1777   The From request-header field, if given, &SHOULD; contain an Internet
1778   e-mail address for the human user who controls the requesting user
1779   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
1780   in <xref x:sec="3.4" x:fmt="of" target="RFC2822"/>:
1782<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/>
1783  From    = "From" ":" mailbox
1785  mailbox = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC2822"/>&gt;
1788   An example is:
1790<figure><artwork type="example">
1791    From:
1794   This header field &MAY; be used for logging purposes and as a means for
1795   identifying the source of invalid or unwanted requests. It &SHOULD-NOT;
1796   be used as an insecure form of access protection. The interpretation
1797   of this field is that the request is being performed on behalf of the
1798   person given, who accepts responsibility for the method performed. In
1799   particular, robot agents &SHOULD; include this header so that the
1800   person responsible for running the robot can be contacted if problems
1801   occur on the receiving end.
1804   The Internet e-mail address in this field &MAY; be separate from the
1805   Internet host which issued the request. For example, when a request
1806   is passed through a proxy the original issuer's address &SHOULD; be
1807   used.
1810   The client &SHOULD-NOT;  send the From header field without the user's
1811   approval, as it might conflict with the user's privacy interests or
1812   their site's security policy. It is strongly recommended that the
1813   user be able to disable, enable, and modify the value of this field
1814   at any time prior to a request.
1818<section title="Location" anchor="header.location">
1819  <iref primary="true" item="Location header" x:for-anchor=""/>
1820  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
1822   The Location response-header field is used to redirect the recipient
1823   to a location other than the Request-URI for completion of the
1824   request or identification of a new resource. For 201 (Created)
1825   responses, the Location is that of the new resource which was created
1826   by the request. For 3xx responses, the location &SHOULD; indicate the
1827   server's preferred URI for automatic redirection to the resource. The
1828   field value consists of a single absolute URI.
1830<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/>
1831  Location       = "Location" ":" absoluteURI [ "#" fragment ]
1834   An example is:
1836<figure><artwork type="example">
1837    Location:
1840  <list><t>
1841      <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
1842      from Location in that the Content-Location identifies the original
1843      location of the entity enclosed in the request. It is therefore
1844      possible for a response to contain header fields for both Location
1845      and Content-Location.
1846  </t></list>
1849   There are circumstances in which a fragment identifier in a Location URL would not be appropriate:
1850   <list style="symbols">
1851      <t>With a 201 Created response, because in this usage the Location header specifies the URL for the entire created resource.</t>
1852      <t>With a 300 Multiple Choices, since the choice decision is intended to be made on resource characteristics and not fragment characteristics.</t>
1853      <t>With 305 Use Proxy.</t>
1854   </list>
1858<section title="Max-Forwards" anchor="header.max-forwards">
1859  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
1860  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
1862   The Max-Forwards request-header field provides a mechanism with the
1863   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>) methods to limit the
1864   number of proxies or gateways that can forward the request to the
1865   next inbound server. This can be useful when the client is attempting
1866   to trace a request chain which appears to be failing or looping in
1867   mid-chain.
1869<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/>
1870  Max-Forwards   = "Max-Forwards" ":" 1*DIGIT
1873   The Max-Forwards value is a decimal integer indicating the remaining
1874   number of times this request message may be forwarded.
1877   Each proxy or gateway recipient of a TRACE or OPTIONS request
1878   containing a Max-Forwards header field &MUST; check and update its
1879   value prior to forwarding the request. If the received value is zero
1880   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
1881   respond as the final recipient. If the received Max-Forwards value is
1882   greater than zero, then the forwarded message &MUST; contain an updated
1883   Max-Forwards field with a value decremented by one (1).
1886   The Max-Forwards header field &MAY; be ignored for all other methods
1887   defined by this specification and for any extension methods for which
1888   it is not explicitly referred to as part of that method definition.
1892<section title="Referer" anchor="header.referer">
1893  <iref primary="true" item="Referer header" x:for-anchor=""/>
1894  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
1896   The Referer[sic] request-header field allows the client to specify,
1897   for the server's benefit, the address (URI) of the resource from
1898   which the Request-URI was obtained (the "referrer", although the
1899   header field is misspelled.) The Referer request-header allows a
1900   server to generate lists of back-links to resources for interest,
1901   logging, optimized caching, etc. It also allows obsolete or mistyped
1902   links to be traced for maintenance. The Referer field &MUST-NOT; be
1903   sent if the Request-URI was obtained from a source that does not have
1904   its own URI, such as input from the user keyboard.
1906<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/>
1907  Referer        = "Referer" ":" ( absoluteURI | relativeURI )
1910   Example:
1912<figure><artwork type="example">
1913    Referer:
1916   If the field value is a relative URI, it &SHOULD; be interpreted
1917   relative to the Request-URI. The URI &MUST-NOT; include a fragment. See
1918   <xref target=""/> for security considerations.
1922<section title="Retry-After" anchor="header.retry-after">
1923  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
1924  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
1926   The Retry-After response-header field can be used with a 503 (Service
1927   Unavailable) response to indicate how long the service is expected to
1928   be unavailable to the requesting client. This field &MAY; also be used
1929   with any 3xx (Redirection) response to indicate the minimum time the
1930   user-agent is asked wait before issuing the redirected request. The
1931   value of this field can be either an HTTP-date or an integer number
1932   of seconds (in decimal) after the time of the response.
1934<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/>
1935  Retry-After  = "Retry-After" ":" ( HTTP-date | delta-seconds )
1938   Two examples of its use are
1940<figure><artwork type="example">
1941    Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
1942    Retry-After: 120
1945   In the latter example, the delay is 2 minutes.
1949<section title="Server" anchor="header.server">
1950  <iref primary="true" item="Server header" x:for-anchor=""/>
1951  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
1953   The Server response-header field contains information about the
1954   software used by the origin server to handle the request. The field
1955   can contain multiple product tokens (&product-tokens;) and comments
1956   identifying the server and any significant subproducts. The product
1957   tokens are listed in order of their significance for identifying the
1958   application.
1960<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/>
1961  Server         = "Server" ":" 1*( product | comment )
1964   Example:
1966<figure><artwork type="example">
1967    Server: CERN/3.0 libwww/2.17
1970   If the response is being forwarded through a proxy, the proxy
1971   application &MUST-NOT; modify the Server response-header. Instead, it
1972   &MUST; include a Via field (as described in &header-via;).
1973  <list><t>
1974      <x:h>Note:</x:h> Revealing the specific software version of the server might
1975      allow the server machine to become more vulnerable to attacks
1976      against software that is known to contain security holes. Server
1977      implementors are encouraged to make this field a configurable
1978      option.
1979  </t></list>
1983<section title="User-Agent" anchor="header.user-agent">
1984  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
1985  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
1987   The User-Agent request-header field contains information about the
1988   user agent originating the request. This is for statistical purposes,
1989   the tracing of protocol violations, and automated recognition of user
1990   agents for the sake of tailoring responses to avoid particular user
1991   agent limitations. User agents &SHOULD; include this field with
1992   requests. The field can contain multiple product tokens (&product-tokens;)
1993   and comments identifying the agent and any subproducts which form a
1994   significant part of the user agent. By convention, the product tokens
1995   are listed in order of their significance for identifying the
1996   application.
1998<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/>
1999  User-Agent     = "User-Agent" ":" 1*( product | comment )
2002   Example:
2004<figure><artwork type="example">
2005    User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2011<section title="IANA Considerations" anchor="IANA.considerations">
2013   <cref>TBD.</cref>
2017<section title="Security Considerations" anchor="security.considerations">
2019   This section is meant to inform application developers, information
2020   providers, and users of the security limitations in HTTP/1.1 as
2021   described by this document. The discussion does not include
2022   definitive solutions to the problems revealed, though it does make
2023   some suggestions for reducing security risks.
2026<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2028   Like any generic data transfer protocol, HTTP cannot regulate the
2029   content of the data that is transferred, nor is there any a priori
2030   method of determining the sensitivity of any particular piece of
2031   information within the context of any given request. Therefore,
2032   applications &SHOULD; supply as much control over this information as
2033   possible to the provider of that information. Four header fields are
2034   worth special mention in this context: Server, Via, Referer and From.
2037   Revealing the specific software version of the server might allow the
2038   server machine to become more vulnerable to attacks against software
2039   that is known to contain security holes. Implementors &SHOULD; make the
2040   Server header field a configurable option.
2043   Proxies which serve as a portal through a network firewall &SHOULD;
2044   take special precautions regarding the transfer of header information
2045   that identifies the hosts behind the firewall. In particular, they
2046   &SHOULD; remove, or replace with sanitized versions, any Via fields
2047   generated behind the firewall.
2050   The Referer header allows reading patterns to be studied and reverse
2051   links drawn. Although it can be very useful, its power can be abused
2052   if user details are not separated from the information contained in
2053   the Referer. Even when the personal information has been removed, the
2054   Referer header might indicate a private document's URI whose
2055   publication would be inappropriate.
2058   The information sent in the From field might conflict with the user's
2059   privacy interests or their site's security policy, and hence it
2060   &SHOULD-NOT;  be transmitted without the user being able to disable,
2061   enable, and modify the contents of the field. The user &MUST; be able
2062   to set the contents of this field within a user preference or
2063   application defaults configuration.
2066   We suggest, though do not require, that a convenient toggle interface
2067   be provided for the user to enable or disable the sending of From and
2068   Referer information.
2071   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2072   fields can sometimes be used to determine that a specific client or
2073   server have a particular security hole which might be exploited.
2074   Unfortunately, this same information is often used for other valuable
2075   purposes for which HTTP currently has no better mechanism.
2079<section title="Encoding Sensitive Information in URIs" anchor="">
2081   Because the source of a link might be private information or might
2082   reveal an otherwise private information source, it is strongly
2083   recommended that the user be able to select whether or not the
2084   Referer field is sent. For example, a browser client could have a
2085   toggle switch for browsing openly/anonymously, which would
2086   respectively enable/disable the sending of Referer and From
2087   information.
2090   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2091   HTTP request if the referring page was transferred with a secure
2092   protocol.
2095   Authors of services should not use
2096   GET-based forms for the submission of sensitive data because that
2097   data will be encoded in the Request-URI. Many existing
2098   servers, proxies, and user agents log or display the Request-URI in
2099   places where it might be visible to third parties. Such services can
2100   use POST-based form submission instead.
2104<section title="Location Headers and Spoofing" anchor="location.spoofing">
2106   If a single server supports multiple organizations that do not trust
2107   one another, then it &MUST; check the values of Location and Content-Location
2108   headers in responses that are generated under control of
2109   said organizations to make sure that they do not attempt to
2110   invalidate resources over which they have no authority.
2116<section title="Acknowledgments" anchor="ack">
2121<references title="Normative References">
2123<reference anchor="Part1">
2124  <front>
2125    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2126    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2127      <organization abbrev="Day Software">Day Software</organization>
2128      <address><email></email></address>
2129    </author>
2130    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2131      <organization>One Laptop per Child</organization>
2132      <address><email></email></address>
2133    </author>
2134    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2135      <organization abbrev="HP">Hewlett-Packard Company</organization>
2136      <address><email></email></address>
2137    </author>
2138    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2139      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2140      <address><email></email></address>
2141    </author>
2142    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2143      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2144      <address><email></email></address>
2145    </author>
2146    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2147      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2148      <address><email></email></address>
2149    </author>
2150    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2151      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2152      <address><email></email></address>
2153    </author>
2154    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2155      <organization abbrev="W3C">World Wide Web Consortium</organization>
2156      <address><email></email></address>
2157    </author>
2158    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2159      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2160      <address><email></email></address>
2161    </author>
2162    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2163  </front>
2164  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2165  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2168<reference anchor="Part3">
2169  <front>
2170    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2171    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2172      <organization abbrev="Day Software">Day Software</organization>
2173      <address><email></email></address>
2174    </author>
2175    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2176      <organization>One Laptop per Child</organization>
2177      <address><email></email></address>
2178    </author>
2179    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2180      <organization abbrev="HP">Hewlett-Packard Company</organization>
2181      <address><email></email></address>
2182    </author>
2183    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2184      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2185      <address><email></email></address>
2186    </author>
2187    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2188      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2189      <address><email></email></address>
2190    </author>
2191    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2192      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2193      <address><email></email></address>
2194    </author>
2195    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2196      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2197      <address><email></email></address>
2198    </author>
2199    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2200      <organization abbrev="W3C">World Wide Web Consortium</organization>
2201      <address><email></email></address>
2202    </author>
2203    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2204      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2205      <address><email></email></address>
2206    </author>
2207    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2208  </front>
2209  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2210  <x:source href="p3-payload.xml" basename="p3-payload"/>
2213<reference anchor="Part4">
2214  <front>
2215    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2216    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2217      <organization abbrev="Day Software">Day Software</organization>
2218      <address><email></email></address>
2219    </author>
2220    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2221      <organization>One Laptop per Child</organization>
2222      <address><email></email></address>
2223    </author>
2224    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2225      <organization abbrev="HP">Hewlett-Packard Company</organization>
2226      <address><email></email></address>
2227    </author>
2228    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2229      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2230      <address><email></email></address>
2231    </author>
2232    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2233      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2234      <address><email></email></address>
2235    </author>
2236    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2237      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2238      <address><email></email></address>
2239    </author>
2240    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2241      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2242      <address><email></email></address>
2243    </author>
2244    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2245      <organization abbrev="W3C">World Wide Web Consortium</organization>
2246      <address><email></email></address>
2247    </author>
2248    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2249      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2250      <address><email></email></address>
2251    </author>
2252    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2253  </front>
2254  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2255  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2258<reference anchor="Part5">
2259  <front>
2260    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2261    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2262      <organization abbrev="Day Software">Day Software</organization>
2263      <address><email></email></address>
2264    </author>
2265    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2266      <organization>One Laptop per Child</organization>
2267      <address><email></email></address>
2268    </author>
2269    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2270      <organization abbrev="HP">Hewlett-Packard Company</organization>
2271      <address><email></email></address>
2272    </author>
2273    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2274      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2275      <address><email></email></address>
2276    </author>
2277    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2278      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2279      <address><email></email></address>
2280    </author>
2281    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2282      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2283      <address><email></email></address>
2284    </author>
2285    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2286      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2287      <address><email></email></address>
2288    </author>
2289    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2290      <organization abbrev="W3C">World Wide Web Consortium</organization>
2291      <address><email></email></address>
2292    </author>
2293    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2294      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2295      <address><email></email></address>
2296    </author>
2297    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2298  </front>
2299  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
2300  <x:source href="p5-range.xml" basename="p5-range"/>
2303<reference anchor="Part6">
2304  <front>
2305    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2306    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2307      <organization abbrev="Day Software">Day Software</organization>
2308      <address><email></email></address>
2309    </author>
2310    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2311      <organization>One Laptop per Child</organization>
2312      <address><email></email></address>
2313    </author>
2314    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2315      <organization abbrev="HP">Hewlett-Packard Company</organization>
2316      <address><email></email></address>
2317    </author>
2318    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2319      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2320      <address><email></email></address>
2321    </author>
2322    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2323      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2324      <address><email></email></address>
2325    </author>
2326    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2327      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2328      <address><email></email></address>
2329    </author>
2330    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2331      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2332      <address><email></email></address>
2333    </author>
2334    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2335      <organization abbrev="W3C">World Wide Web Consortium</organization>
2336      <address><email></email></address>
2337    </author>
2338    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2339      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2340      <address><email></email></address>
2341    </author>
2342    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2343  </front>
2344  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2345  <x:source href="p6-cache.xml" basename="p6-cache"/>
2348<reference anchor="Part7">
2349  <front>
2350    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2351    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2352      <organization abbrev="Day Software">Day Software</organization>
2353      <address><email></email></address>
2354    </author>
2355    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2356      <organization>One Laptop per Child</organization>
2357      <address><email></email></address>
2358    </author>
2359    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2360      <organization abbrev="HP">Hewlett-Packard Company</organization>
2361      <address><email></email></address>
2362    </author>
2363    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2364      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2365      <address><email></email></address>
2366    </author>
2367    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2368      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2369      <address><email></email></address>
2370    </author>
2371    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2372      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2373      <address><email></email></address>
2374    </author>
2375    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2376      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2377      <address><email></email></address>
2378    </author>
2379    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2380      <organization abbrev="W3C">World Wide Web Consortium</organization>
2381      <address><email></email></address>
2382    </author>
2383    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2384      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2385      <address><email></email></address>
2386    </author>
2387    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2388  </front>
2389  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
2390  <x:source href="p7-auth.xml" basename="p7-auth"/>
2393<reference anchor="RFC2119">
2394  <front>
2395    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2396    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2397      <organization>Harvard University</organization>
2398      <address><email></email></address>
2399    </author>
2400    <date month="March" year="1997"/>
2401  </front>
2402  <seriesInfo name="BCP" value="14"/>
2403  <seriesInfo name="RFC" value="2119"/>
2408<references title="Informative References">
2410<reference anchor="Luo1998">
2411  <front>
2412    <title>Tunneling TCP based protocols through Web proxy servers</title>
2413    <author initials="A." surname="Luotonen" fullname="A. Luotonen">
2414      <organization/>
2415    </author>
2416    <date year="1998" month="August"/>
2417  </front>
2418  <seriesInfo name="Internet-Draft" value="draft-luotonen-web-proxy-tunneling-01"/>
2421<reference anchor="RFC1945">
2422  <front>
2423    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2424    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2425      <organization>MIT, Laboratory for Computer Science</organization>
2426      <address><email></email></address>
2427    </author>
2428    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2429      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2430      <address><email></email></address>
2431    </author>
2432    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2433      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2434      <address><email></email></address>
2435    </author>
2436    <date month="May" year="1996"/>
2437  </front>
2438  <seriesInfo name="RFC" value="1945"/>
2441<reference anchor="RFC2068">
2442  <front>
2443    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2444    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2445      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2446      <address><email></email></address>
2447    </author>
2448    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2449      <organization>MIT Laboratory for Computer Science</organization>
2450      <address><email></email></address>
2451    </author>
2452    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2453      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2454      <address><email></email></address>
2455    </author>
2456    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2457      <organization>MIT Laboratory for Computer Science</organization>
2458      <address><email></email></address>
2459    </author>
2460    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2461      <organization>MIT Laboratory for Computer Science</organization>
2462      <address><email></email></address>
2463    </author>
2464    <date month="January" year="1997"/>
2465  </front>
2466  <seriesInfo name="RFC" value="2068"/>
2469<reference anchor="RFC2616">
2470  <front>
2471    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2472    <author initials="R." surname="Fielding" fullname="R. Fielding">
2473      <organization>University of California, Irvine</organization>
2474      <address><email></email></address>
2475    </author>
2476    <author initials="J." surname="Gettys" fullname="J. Gettys">
2477      <organization>W3C</organization>
2478      <address><email></email></address>
2479    </author>
2480    <author initials="J." surname="Mogul" fullname="J. Mogul">
2481      <organization>Compaq Computer Corporation</organization>
2482      <address><email></email></address>
2483    </author>
2484    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2485      <organization>MIT Laboratory for Computer Science</organization>
2486      <address><email></email></address>
2487    </author>
2488    <author initials="L." surname="Masinter" fullname="L. Masinter">
2489      <organization>Xerox Corporation</organization>
2490      <address><email></email></address>
2491    </author>
2492    <author initials="P." surname="Leach" fullname="P. Leach">
2493      <organization>Microsoft Corporation</organization>
2494      <address><email></email></address>
2495    </author>
2496    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2497      <organization>W3C</organization>
2498      <address><email></email></address>
2499    </author>
2500    <date month="June" year="1999"/>
2501  </front>
2502  <seriesInfo name="RFC" value="2616"/>
2505<reference anchor="RFC2822">
2506  <front>
2507    <title>Internet Message Format</title>
2508    <author initials="P." surname="Resnick" fullname="P. Resnick">
2509      <organization>QUALCOMM Incorporated</organization>
2510    </author>
2511    <date year="2001" month="April"/>
2512  </front>
2513  <seriesInfo name="RFC" value="2822"/>
2518<section title="Compatibility with Previous Versions" anchor="compatibility">
2519<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
2521   Clarified which error code should be used for inbound server failures
2522   (e.g. DNS failures). (<xref target="status.504"/>).
2525   201 (Created) had a race that required an Etag be sent when a resource is
2526   first created. (<xref target="status.201"/>).
2529   Rewrite of message transmission requirements to make it much harder
2530   for implementors to get it wrong, as the consequences of errors here
2531   can have significant impact on the Internet, and to deal with the
2532   following problems:
2533  <list style="numbers">
2534      <t>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
2535         this was incorrectly placing a requirement on the behavior of
2536         an implementation of a future version of HTTP/1.x</t>
2538      <t>Made it clear that user-agents should retry requests, not
2539         "clients" in general.</t>
2541      <t>Converted requirements for clients to ignore unexpected 100
2542         (Continue) responses, and for proxies to forward 100 responses,
2543         into a general requirement for 1xx responses.</t>
2545      <t>Modified some TCP-specific language, to make it clearer that
2546         non-TCP transports are possible for HTTP.</t>
2548      <t>Require that the origin server &MUST-NOT; wait for the request
2549         body before it sends a required 100 (Continue) response.</t>
2551      <t>Allow, rather than require, a server to omit 100 (Continue) if
2552         it has already seen some of the request body.</t>
2554      <t>Allow servers to defend against denial-of-service attacks and
2555         broken clients.</t>
2556  </list>
2559   This change adds the Expect header and 417 status code.
2562   Clean up confusion between 403 and 404 responses. (Section <xref target="status.403" format="counter"/>,
2563   <xref target="status.404" format="counter"/>, and <xref target="status.410" format="counter"/>)
2566   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
2567   implemented in previous versions of this specification. See <xref target="RFC2068"/>.
2571<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
2573  Clarify definition of POST.
2574  (<xref target="POST"/>)
2577  Failed to consider that there are
2578  many other request methods that are safe to automatically redirect,
2579  and further that the user agent is able to make that determination
2580  based on the request method semantics.
2581  (Sections <xref format="counter" target="status.301"/>,
2582  <xref format="counter" target="status.302"/> and
2583  <xref format="counter" target="status.307"/> )
2586  Correct syntax of Location header to allow fragment,
2587  as referred symbol wasn't what was expected, and add some
2588  clarifications as to when it would not be appropriate.
2589  (<xref target="header.location"/>)
2592  In the description of the Server header, the Via field
2593  was described as a SHOULD. The requirement was and is stated
2594  correctly in the description of the Via header in &header-via;.
2595  (<xref target="header.server"/>)
2601<section title="Change Log (to be removed by RFC Editor before publication)">
2603<section title="Since RFC2616">
2605  Extracted relevant partitions from <xref target="RFC2616"/>.
2609<section title="Since draft-ietf-httpbis-p2-semantics-00">
2611  Closed issues:
2612  <list style="symbols">
2613    <t>
2614      <eref target=""/>:
2615      "Via is a MUST"
2616      (<eref target=""/>)
2617    </t>
2618    <t>
2619      <eref target=""/>:
2620      "Fragments allowed in Location"
2621      (<eref target=""/>)
2622    </t>
2623    <t>
2624      <eref target=""/>:
2625      "Safe Methods vs Redirection"
2626      (<eref target=""/>)
2627    </t>
2628    <t>
2629      <eref target=""/>:
2630      "Revise description of the POST method"
2631      (<eref target=""/>)
2632    </t>
2633    <t>
2634      <eref target=""/>:
2635      "Normative and Informative references"
2636    </t>
2637    <t>
2638      <eref target=""/>:
2639      "RFC2606 Compliance"
2640    </t>
2641    <t>
2642      <eref target=""/>:
2643      "Informative references"
2644    </t>
2645    <t>
2646      <eref target=""/>:
2647      "Redundant cross-references"
2648    </t>
2649  </list>
2652  Other changes:
2653  <list style="symbols">
2654    <t>
2655      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
2656    </t>
2657  </list>
2661<section title="Since draft-ietf-httpbis-p2-semantics-01">
2663  Closed issues:
2664  <list style="symbols">
2665    <t>
2666      <eref target=""/>:
2667      "PUT side effects"
2668    </t>
2669    <t>
2670      <eref target=""/>:
2671      "Duplicate Host header requirements"
2672    </t>
2673  </list>
2676  Ongoing work on ABNF conversion (<eref target=""/>):
2677  <list style="symbols">
2678    <t>
2679      Move "Product Tokens" section (back) into Part 1, as "token" is used
2680      in the definition of the Upgrade header.
2681    </t>
2682    <t>
2683      Add explicit references to BNF syntax and rules imported from other parts of the specification.
2684    </t>
2685  </list>
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