source: draft-ietf-httpbis/latest/p2-semantics.xml @ 207

Last change on this file since 207 was 207, checked in by julian.reschke@…, 12 years ago

Work on referencing ABNF rules adopted from other parts (finished for all parts, also grouped by part); relates to #36.

  • Property svn:eol-style set to native
File size: 123.5 KB
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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='http://purl.org/net/xml2rfc/ext'>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>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='http://purl.org/net/xml2rfc/ext'/>">
18  <!ENTITY payload                    "<xref target='Part3' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
19  <!ENTITY conditional                "<xref target='Part4' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY range                      "<xref target='Part5' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY caching                    "<xref target='Part6' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY auth                       "<xref target='Part7' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23  <!ENTITY content-negotiation        "<xref target='Part3' x:rel='#content.negotiation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
24  <!ENTITY notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
25  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
26  <!ENTITY general-syntax             "<xref target='Part1' x:rel='#general.syntax' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
27  <!ENTITY uri                        "<xref target='Part1' x:rel='#uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
28  <!ENTITY full-date                  "<xref target='Part1' x:rel='#full.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
29  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
42  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
43  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
44  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
45  <!ENTITY header-host                "<xref target='Part1' x:rel='#header.host' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
46  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
47  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
48  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
49  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
50  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
51  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
52  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
53  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
54  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
55  <!ENTITY header-upgrade             "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
56  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.upgrade' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
57  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
58  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
59  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
60  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
61  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
62  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
63]>
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='http://purl.org/net/xml2rfc/ext'>
78<front>
79
80  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
81
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>fielding@gbiv.com</email>
95      <uri>http://roy.gbiv.com/</uri>
96    </address>
97  </author>
98
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>jg@laptop.org</email>
110      <uri>http://www.laptop.org/</uri>
111    </address>
112  </author>
113 
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>JeffMogul@acm.org</email>
126    </address>
127  </author>
128
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>henrikn@microsoft.com</email>
140    </address>
141  </author>
142
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>LMM@acm.org</email>
154      <uri>http://larry.masinter.net/</uri>
155    </address>
156  </author>
157 
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>paulle@microsoft.com</email>
168    </address>
169  </author>
170   
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>timbl@w3.org</email>
184      <uri>http://www.w3.org/People/Berners-Lee/</uri>
185    </address>
186  </author>
187
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>ylafon@w3.org</email>
200      <uri>http://www.raubacapeu.net/people/yves/</uri>
201    </address>
202  </author>
203
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>julian.reschke@greenbytes.de</email>       
215      <uri>http://greenbytes.de/tech/webdav/</uri>     
216    </address>
217  </author>
218
219  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
220
221<abstract>
222<t>
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.
231</t>
232</abstract>
233
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 (ietf-http-wg@w3.org). The current issues list is
238    at <eref target="http://www.tools.ietf.org/wg/httpbis/trac/report/11"/>
239    and related documents (including fancy diffs) can be found at
240    <eref target="http://www.tools.ietf.org/wg/httpbis/"/>.
241  </t>
242  <t>
243    This draft incorporates those issue resolutions that were either
244    collected in the original RFC2616 errata list (<eref target="http://purl.org/NET/http-errata"/>),
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>
248</note>
249</front>
250<middle>
251<section title="Introduction" anchor="introduction">
252<t>
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.
261</t>
262<t>
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"/>.
272</t>
273
274<section title="Requirements" anchor="intro.requirements">
275<t>
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"/>.
279</t>
280<t>
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."
288</t>
289</section>
290</section>
291
292<section title="Notational Conventions and Generic Grammar" anchor="notation">
293<t>
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="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>.</cref>
298</t>
299<figure><artwork type="abnf2616">
300  DIGIT         = &lt;DIGIT, defined in &basic-rules;&gt;
301</artwork></figure>
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;
306</artwork></figure>
307<t anchor="abnf.dependencies">
308  The ABNF rules below are defined in other parts:
309</t>
310<figure><!--Part1--><artwork type="abnf2616">
311  absoluteURI   = &lt;absoluteURI, defined in &general-syntax;&gt;
312  fragment      = &lt;fragment, defined in &general-syntax;&gt;
313  Host          = &lt;Host, defined in &header-host;&gt;
314  HTTP-date     = &lt;HTTP-date, defined in &full-date;&gt;
315  product       = &lt;product, defined in &product-tokens;&gt;
316  relativeURI   = &lt;relativeURI, defined in &general-syntax;&gt;
317  TE            = &lt;TE, defined in &header-te;&gt;
318</artwork></figure>
319<figure><!--Part3--><artwork type="abnf2616">
320  Accept        = &lt;Accept, defined in &header-accept;&gt;
321  Accept-Charset =
322             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
323  Accept-Encoding =
324             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
325  Accept-Language =
326             &lt;Accept-Language, defined in &header-accept-language;&gt;
327</artwork></figure>
328<figure><!--Part4--><artwork type="abnf2616">
329  ETag          = &lt;ETag, defined in &header-etag;&gt;
330  If-Match      = &lt;If-Match, defined in &header-if-match;&gt;
331  If-Modified-Since =
332             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
333  If-None-Match = &lt;If-None-Match, defined in &header-if-none-match;&gt;
334  If-Unmodified-Since =
335             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
336</artwork></figure>
337<figure><!--Part5--><artwork type="abnf2616">
338  Accept-Ranges = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
339  If-Range      = &lt;If-Range, defined in &header-if-range;&gt;
340  Range         = &lt;Range, defined in &header-range;&gt;
341</artwork></figure>
342<figure><!--Part6--><artwork type="abnf2616">
343  Age           = &lt;Age, defined in &header-age;&gt;
344  delta-seconds = &lt;delta-seconds, defined in &header-age;&gt;
345  Vary          = &lt;Vary, defined in &header-vary;&gt;
346</artwork><!--Part7--></figure>
347<figure><artwork type="abnf2616">
348  Authorization = &lt;Authorization, defined in &header-authorization;&gt;
349  Proxy-Authenticate =
350             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
351  Proxy-Authorization =
352             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
353  WWW-Authenticate =
354             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
355</artwork></figure>
356</section>
357
358<section title="Method" anchor="method">
359<t>
360   The Method  token indicates the method to be performed on the
361   resource identified by the Request-URI. The method is case-sensitive.
362</t>
363<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
364  Method         = "OPTIONS"                ; <xref target="OPTIONS"/>
365                 | "GET"                    ; <xref target="GET"/>
366                 | "HEAD"                   ; <xref target="HEAD"/>
367                 | "POST"                   ; <xref target="POST"/>
368                 | "PUT"                    ; <xref target="PUT"/>
369                 | "DELETE"                 ; <xref target="DELETE"/>
370                 | "TRACE"                  ; <xref target="TRACE"/>
371                 | "CONNECT"                ; <xref target="CONNECT"/>
372                 | extension-method
373  extension-method = token
374</artwork></figure>
375<t>
376   The list of methods allowed by a resource can be specified in an
377   Allow header field (<xref target="header.allow"/>). The return code of the response
378   always notifies the client whether a method is currently allowed on a
379   resource, since the set of allowed methods can change dynamically. An
380   origin server &SHOULD; return the status code 405 (Method Not Allowed)
381   if the method is known by the origin server but not allowed for the
382   requested resource, and 501 (Not Implemented) if the method is
383   unrecognized or not implemented by the origin server. The methods GET
384   and HEAD &MUST; be supported by all general-purpose servers. All other
385   methods are &OPTIONAL;; however, if the above methods are implemented,
386   they &MUST; be implemented with the same semantics as those specified
387   in <xref target="method.definitions"/>.
388</t>
389</section>
390
391<section title="Request Header Fields" anchor="request.header.fields">
392<t>
393   The request-header fields allow the client to pass additional
394   information about the request, and about the client itself, to the
395   server. These fields act as request modifiers, with semantics
396   equivalent to the parameters on a programming language method
397   invocation.
398</t>
399<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
400  request-header = Accept                   ; &header-accept;
401                 | Accept-Charset           ; &header-accept-charset;
402                 | Accept-Encoding          ; &header-accept-encoding;
403                 | Accept-Language          ; &header-accept-language;
404                 | Authorization            ; &header-authorization;
405                 | Expect                   ; <xref target="header.expect"/>
406                 | From                     ; <xref target="header.from"/>
407                 | Host                     ; &header-host;
408                 | If-Match                 ; &header-if-match;
409                 | If-Modified-Since        ; &header-if-modified-since;
410                 | If-None-Match            ; &header-if-none-match;
411                 | If-Range                 ; &header-if-range;
412                 | If-Unmodified-Since      ; &header-if-unmodified-since;
413                 | Max-Forwards             ; <xref target="header.max-forwards"/>
414                 | Proxy-Authorization      ; &header-proxy-authorization;
415                 | Range                    ; &header-range;
416                 | Referer                  ; <xref target="header.referer"/>
417                 | TE                       ; &header-te;
418                 | User-Agent               ; <xref target="header.user-agent"/>
419</artwork></figure>
420<t>
421   Request-header field names can be extended reliably only in
422   combination with a change in the protocol version. However, new or
423   experimental header fields &MAY; be given the semantics of request-header
424   fields if all parties in the communication recognize them to
425   be request-header fields. Unrecognized header fields are treated as
426   entity-header fields.
427</t>
428</section>
429
430<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
431<t>
432   The Status-Code element is a 3-digit integer result code of the
433   attempt to understand and satisfy the request. The status codes listed
434   below are defined in <xref target="status.codes"/>.
435   The Reason-Phrase is intended to give a short
436   textual description of the Status-Code. The Status-Code is intended
437   for use by automata and the Reason-Phrase is intended for the human
438   user. The client is not required to examine or display the Reason-Phrase.
439</t>
440<t> 
441   The individual values of the numeric status codes defined for
442   HTTP/1.1, and an example set of corresponding Reason-Phrase's, are
443   presented below. The reason phrases listed here are only
444   recommendations -- they &MAY; be replaced by local equivalents without
445   affecting the protocol.
446</t>
447<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"/>
448  Status-Code    =
449         "100"  ; <xref target="status.100"/>: Continue
450       | "101"  ; <xref target="status.101"/>: Switching Protocols
451       | "200"  ; <xref target="status.200"/>: OK
452       | "201"  ; <xref target="status.201"/>: Created
453       | "202"  ; <xref target="status.202"/>: Accepted
454       | "203"  ; <xref target="status.203"/>: Non-Authoritative Information
455       | "204"  ; <xref target="status.204"/>: No Content
456       | "205"  ; <xref target="status.205"/>: Reset Content
457       | "206"  ; <xref target="status.206"/>: Partial Content
458       | "300"  ; <xref target="status.300"/>: Multiple Choices
459       | "301"  ; <xref target="status.301"/>: Moved Permanently
460       | "302"  ; <xref target="status.302"/>: Found
461       | "303"  ; <xref target="status.303"/>: See Other
462       | "304"  ; <xref target="status.304"/>: Not Modified
463       | "305"  ; <xref target="status.305"/>: Use Proxy
464       | "307"  ; <xref target="status.307"/>: Temporary Redirect
465       | "400"  ; <xref target="status.400"/>: Bad Request
466       | "401"  ; <xref target="status.401"/>: Unauthorized
467       | "402"  ; <xref target="status.402"/>: Payment Required
468       | "403"  ; <xref target="status.403"/>: Forbidden
469       | "404"  ; <xref target="status.404"/>: Not Found
470       | "405"  ; <xref target="status.405"/>: Method Not Allowed
471       | "406"  ; <xref target="status.406"/>: Not Acceptable
472       | "407"  ; <xref target="status.407"/>: Proxy Authentication Required
473       | "408"  ; <xref target="status.408"/>: Request Time-out
474       | "409"  ; <xref target="status.409"/>: Conflict
475       | "410"  ; <xref target="status.410"/>: Gone
476       | "411"  ; <xref target="status.411"/>: Length Required
477       | "412"  ; <xref target="status.412"/>: Precondition Failed
478       | "413"  ; <xref target="status.413"/>: Request Entity Too Large
479       | "414"  ; <xref target="status.414"/>: Request-URI Too Large
480       | "415"  ; <xref target="status.415"/>: Unsupported Media Type
481       | "416"  ; <xref target="status.416"/>: Requested range not satisfiable
482       | "417"  ; <xref target="status.417"/>: Expectation Failed
483       | "500"  ; <xref target="status.500"/>: Internal Server Error
484       | "501"  ; <xref target="status.501"/>: Not Implemented
485       | "502"  ; <xref target="status.502"/>: Bad Gateway
486       | "503"  ; <xref target="status.503"/>: Service Unavailable
487       | "504"  ; <xref target="status.504"/>: Gateway Time-out
488       | "505"  ; <xref target="status.505"/>: HTTP Version not supported
489       | extension-code
490
491  extension-code = 3DIGIT
492  Reason-Phrase  = *&lt;TEXT, excluding CR, LF&gt;
493</artwork></figure>
494<t>
495   HTTP status codes are extensible. HTTP applications are not required
496   to understand the meaning of all registered status codes, though such
497   understanding is obviously desirable. However, applications &MUST;
498   understand the class of any status code, as indicated by the first
499   digit, and treat any unrecognized response as being equivalent to the
500   x00 status code of that class, with the exception that an
501   unrecognized response &MUST-NOT; be cached. For example, if an
502   unrecognized status code of 431 is received by the client, it can
503   safely assume that there was something wrong with its request and
504   treat the response as if it had received a 400 status code. In such
505   cases, user agents &SHOULD; present to the user the entity returned
506   with the response, since that entity is likely to include human-readable
507   information which will explain the unusual status.
508</t>
509</section>
510
511<section title="Response Header Fields" anchor="response.header.fields">
512<t>
513   The response-header fields allow the server to pass additional
514   information about the response which cannot be placed in the Status-Line.
515   These header fields give information about the server and about
516   further access to the resource identified by the Request-URI.
517</t>
518<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
519  response-header = Accept-Ranges           ; &header-accept-ranges;
520                  | Age                     ; &header-age;
521                  | ETag                    ; &header-etag;
522                  | Location                ; <xref target="header.location"/>
523                  | Proxy-Authenticate      ; &header-proxy-authenticate;
524                  | Retry-After             ; <xref target="header.retry-after"/>
525                  | Server                  ; <xref target="header.server"/>
526                  | Vary                    ; &header-vary;
527                  | WWW-Authenticate        ; &header-www-authenticate;
528</artwork></figure>
529<t>
530   Response-header field names can be extended reliably only in
531   combination with a change in the protocol version. However, new or
532   experimental header fields &MAY; be given the semantics of response-header
533   fields if all parties in the communication recognize them to
534   be response-header fields. Unrecognized header fields are treated as
535   entity-header fields.
536</t>
537</section>
538
539<section title="Entity" anchor="entity">
540<t>
541   Request and Response messages &MAY; transfer an entity if not otherwise
542   restricted by the request method or response status code. An entity
543   consists of entity-header fields and an entity-body, although some
544   responses will only include the entity-headers. HTTP entity-body and
545   entity-header fields are defined in &payload;.
546</t>
547<t>
548   An entity-body is only present in a message when a message-body is
549   present, as described in &message-body;. The entity-body is obtained
550   from the message-body by decoding any Transfer-Encoding that might
551   have been applied to ensure safe and proper transfer of the message.
552</t>
553</section>
554
555
556<section title="Method Definitions" anchor="method.definitions">
557<t>
558   The set of common methods for HTTP/1.1 is defined below. Although
559   this set can be expanded, additional methods cannot be assumed to
560   share the same semantics for separately extended clients and servers.
561</t>
562
563<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
564
565<section title="Safe Methods" anchor="safe.methods">
566<t>
567   Implementors should be aware that the software represents the user in
568   their interactions over the Internet, and should be careful to allow
569   the user to be aware of any actions they might take which may have an
570   unexpected significance to themselves or others.
571</t>
572<t>
573   In particular, the convention has been established that the GET and
574   HEAD methods &SHOULD-NOT;  have the significance of taking an action
575   other than retrieval. These methods ought to be considered "safe".
576   This allows user agents to represent other methods, such as POST, PUT
577   and DELETE, in a special way, so that the user is made aware of the
578   fact that a possibly unsafe action is being requested.
579</t>
580<t>
581   Naturally, it is not possible to ensure that the server does not
582   generate side-effects as a result of performing a GET request; in
583   fact, some dynamic resources consider that a feature. The important
584   distinction here is that the user did not request the side-effects,
585   so therefore cannot be held accountable for them.
586</t>
587</section>
588
589<section title="Idempotent Methods" anchor="idempotent.methods">
590<t>
591   Methods can also have the property of "idempotence" in that (aside
592   from error or expiration issues) the side-effects of N &gt; 0 identical
593   requests is the same as for a single request. The methods GET, HEAD,
594   PUT and DELETE share this property. Also, the methods OPTIONS and
595   TRACE &SHOULD-NOT;  have side effects, and so are inherently idempotent.
596</t>
597<t>
598   However, it is possible that a sequence of several requests is non-idempotent,
599   even if all of the methods executed in that sequence are
600   idempotent. (A sequence is idempotent if a single execution of the
601   entire sequence always yields a result that is not changed by a
602   reexecution of all, or part, of that sequence.) For example, a
603   sequence is non-idempotent if its result depends on a value that is
604   later modified in the same sequence.
605</t>
606<t>
607   A sequence that never has side effects is idempotent, by definition
608   (provided that no concurrent operations are being executed on the
609   same set of resources).
610</t>
611</section>
612</section>
613
614<section title="OPTIONS" anchor="OPTIONS">
615  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
616  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
617<t>
618   The OPTIONS method represents a request for information about the
619   communication options available on the request/response chain
620   identified by the Request-URI. This method allows the client to
621   determine the options and/or requirements associated with a resource,
622   or the capabilities of a server, without implying a resource action
623   or initiating a resource retrieval.
624</t>
625<t>
626   Responses to this method are not cacheable.
627</t>
628<t>
629   If the OPTIONS request includes an entity-body (as indicated by the
630   presence of Content-Length or Transfer-Encoding), then the media type
631   &MUST; be indicated by a Content-Type field. Although this
632   specification does not define any use for such a body, future
633   extensions to HTTP might use the OPTIONS body to make more detailed
634   queries on the server. A server that does not support such an
635   extension &MAY; discard the request body.
636</t>
637<t>
638   If the Request-URI is an asterisk ("*"), the OPTIONS request is
639   intended to apply to the server in general rather than to a specific
640   resource. Since a server's communication options typically depend on
641   the resource, the "*" request is only useful as a "ping" or "no-op"
642   type of method; it does nothing beyond allowing the client to test
643   the capabilities of the server. For example, this can be used to test
644   a proxy for HTTP/1.1 compliance (or lack thereof).
645</t>
646<t>
647   If the Request-URI is not an asterisk, the OPTIONS request applies
648   only to the options that are available when communicating with that
649   resource.
650</t>
651<t>
652   A 200 response &SHOULD; include any header fields that indicate
653   optional features implemented by the server and applicable to that
654   resource (e.g., Allow), possibly including extensions not defined by
655   this specification. The response body, if any, &SHOULD; also include
656   information about the communication options. The format for such a
657   body is not defined by this specification, but might be defined by
658   future extensions to HTTP. Content negotiation &MAY; be used to select
659   the appropriate response format. If no response body is included, the
660   response &MUST; include a Content-Length field with a field-value of
661   "0".
662</t>
663<t>
664   The Max-Forwards request-header field &MAY; be used to target a
665   specific proxy in the request chain. When a proxy receives an OPTIONS
666   request on an absoluteURI for which request forwarding is permitted,
667   the proxy &MUST; check for a Max-Forwards field. If the Max-Forwards
668   field-value is zero ("0"), the proxy &MUST-NOT; forward the message;
669   instead, the proxy &SHOULD; respond with its own communication options.
670   If the Max-Forwards field-value is an integer greater than zero, the
671   proxy &MUST; decrement the field-value when it forwards the request. If
672   no Max-Forwards field is present in the request, then the forwarded
673   request &MUST-NOT; include a Max-Forwards field.
674</t>
675</section>
676
677<section title="GET" anchor="GET">
678  <iref primary="true" item="GET method" x:for-anchor=""/>
679  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
680<t>
681   The GET method means retrieve whatever information (in the form of an
682   entity) is identified by the Request-URI. If the Request-URI refers
683   to a data-producing process, it is the produced data which shall be
684   returned as the entity in the response and not the source text of the
685   process, unless that text happens to be the output of the process.
686</t>
687<t>
688   The semantics of the GET method change to a "conditional GET" if the
689   request message includes an If-Modified-Since, If-Unmodified-Since,
690   If-Match, If-None-Match, or If-Range header field. A conditional GET
691   method requests that the entity be transferred only under the
692   circumstances described by the conditional header field(s). The
693   conditional GET method is intended to reduce unnecessary network
694   usage by allowing cached entities to be refreshed without requiring
695   multiple requests or transferring data already held by the client.
696</t>
697<t>
698   The semantics of the GET method change to a "partial GET" if the
699   request message includes a Range header field. A partial GET requests
700   that only part of the entity be transferred, as described in &header-range;.
701   The partial GET method is intended to reduce unnecessary
702   network usage by allowing partially-retrieved entities to be
703   completed without transferring data already held by the client.
704</t>
705<t>
706   The response to a GET request is cacheable if and only if it meets
707   the requirements for HTTP caching described in &caching;.
708</t>
709<t>
710   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
711</t>
712</section>
713
714<section title="HEAD" anchor="HEAD">
715  <iref primary="true" item="HEAD method" x:for-anchor=""/>
716  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
717<t>
718   The HEAD method is identical to GET except that the server &MUST-NOT;
719   return a message-body in the response. The metainformation contained
720   in the HTTP headers in response to a HEAD request &SHOULD; be identical
721   to the information sent in response to a GET request. This method can
722   be used for obtaining metainformation about the entity implied by the
723   request without transferring the entity-body itself. This method is
724   often used for testing hypertext links for validity, accessibility,
725   and recent modification.
726</t>
727<t>
728   The response to a HEAD request &MAY; be cacheable in the sense that the
729   information contained in the response &MAY; be used to update a
730   previously cached entity from that resource. If the new field values
731   indicate that the cached entity differs from the current entity (as
732   would be indicated by a change in Content-Length, Content-MD5, ETag
733   or Last-Modified), then the cache &MUST; treat the cache entry as
734   stale.
735</t>
736</section>
737
738<section title="POST" anchor="POST">
739  <iref primary="true" item="POST method" x:for-anchor=""/>
740  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
741<t>
742   The POST method is used to request that the origin server accept the
743   entity enclosed in the request as data to be processed by the resource
744   identified by the Request-URI in the Request-Line. POST is designed
745   to allow a uniform method to cover the following functions:
746  <list style="symbols">
747    <t>
748      Annotation of existing resources;
749    </t>
750    <t>
751        Posting a message to a bulletin board, newsgroup, mailing list,
752        or similar group of articles;
753    </t>
754    <t>
755        Providing a block of data, such as the result of submitting a
756        form, to a data-handling process;
757    </t>
758    <t>
759        Extending a database through an append operation.
760    </t>
761  </list>
762</t>
763<t>
764   The actual function performed by the POST method is determined by the
765   server and is usually dependent on the Request-URI.
766</t>
767<t>
768   The action performed by the POST method might not result in a
769   resource that can be identified by a URI. In this case, either 200
770   (OK) or 204 (No Content) is the appropriate response status,
771   depending on whether or not the response includes an entity that
772   describes the result.
773</t>
774<t>
775   If a resource has been created on the origin server, the response
776   &SHOULD; be 201 (Created) and contain an entity which describes the
777   status of the request and refers to the new resource, and a Location
778   header (see <xref target="header.location"/>).
779</t>
780<t>
781   Responses to this method are not cacheable, unless the response
782   includes appropriate Cache-Control or Expires header fields. However,
783   the 303 (See Other) response can be used to direct the user agent to
784   retrieve a cacheable resource.
785</t>
786</section>
787
788<section title="PUT" anchor="PUT">
789  <iref primary="true" item="PUT method" x:for-anchor=""/>
790  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
791<t>
792   The PUT method requests that the enclosed entity be stored under the
793   supplied Request-URI. If the Request-URI refers to an already
794   existing resource, the enclosed entity &SHOULD; be considered as a
795   modified version of the one residing on the origin server. If the
796   Request-URI does not point to an existing resource, and that URI is
797   capable of being defined as a new resource by the requesting user
798   agent, the origin server can create the resource with that URI. If a
799   new resource is created at the Request-URI, the origin server &MUST;
800         inform the user agent
801   via the 201 (Created) response. If an existing resource is modified,
802   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
803   to indicate successful completion of the request. If the resource
804   could not be created or modified with the Request-URI, an appropriate
805   error response &SHOULD; be given that reflects the nature of the
806   problem. The recipient of the entity &MUST-NOT; ignore any Content-*
807   (e.g. Content-Range) headers that it does not understand or implement
808   and &MUST; return a 501 (Not Implemented) response in such cases.
809</t>
810<t>
811   If the request passes through a cache and the Request-URI identifies
812   one or more currently cached entities, those entries &SHOULD; be
813   treated as stale. Responses to this method are not cacheable.
814</t>
815<t>
816   The fundamental difference between the POST and PUT requests is
817   reflected in the different meaning of the Request-URI. The URI in a
818   POST request identifies the resource that will handle the enclosed
819   entity. That resource might be a data-accepting process, a gateway to
820   some other protocol, or a separate entity that accepts annotations.
821   In contrast, the URI in a PUT request identifies the entity enclosed
822   with the request -- the user agent knows what URI is intended and the
823   server &MUST-NOT; attempt to apply the request to some other resource.
824   If the server desires that the request be applied to a different URI,
825   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
826   then make its own decision regarding whether or not to redirect the
827   request.
828</t>
829<t>
830   A single resource &MAY; be identified by many different URIs. For
831   example, an article might have a URI for identifying "the current
832   version" which is separate from the URI identifying each particular
833   version. In this case, a PUT request on a general URI might result in
834   several other URIs being defined by the origin server.
835</t>
836<t>
837   HTTP/1.1 does not define how a PUT method affects the state of an
838   origin server.
839</t>
840<t>
841   Unless otherwise specified for a particular entity-header, the
842   entity-headers in the PUT request &SHOULD; be applied to the resource
843   created or modified by the PUT.
844</t>
845</section>
846
847<section title="DELETE" anchor="DELETE">
848  <iref primary="true" item="DELETE method" x:for-anchor=""/>
849  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
850<t>
851   The DELETE method requests that the origin server delete the resource
852   identified by the Request-URI. This method &MAY; be overridden by human
853   intervention (or other means) on the origin server. The client cannot
854   be guaranteed that the operation has been carried out, even if the
855   status code returned from the origin server indicates that the action
856   has been completed successfully. However, the server &SHOULD-NOT; 
857   indicate success unless, at the time the response is given, it
858   intends to delete the resource or move it to an inaccessible
859   location.
860</t>
861<t>
862   A successful response &SHOULD; be 200 (OK) if the response includes an
863   entity describing the status, 202 (Accepted) if the action has not
864   yet been enacted, or 204 (No Content) if the action has been enacted
865   but the response does not include an entity.
866</t>
867<t>
868   If the request passes through a cache and the Request-URI identifies
869   one or more currently cached entities, those entries &SHOULD; be
870   treated as stale. Responses to this method are not cacheable.
871</t>
872</section>
873
874<section title="TRACE" anchor="TRACE">
875  <iref primary="true" item="TRACE method" x:for-anchor=""/>
876  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
877<t>
878   The TRACE method is used to invoke a remote, application-layer loop-back
879   of the request message. The final recipient of the request
880   &SHOULD; reflect the message received back to the client as the
881   entity-body of a 200 (OK) response. The final recipient is either the
882   origin server or the first proxy or gateway to receive a Max-Forwards
883   value of zero (0) in the request (see <xref target="header.max-forwards"/>). A TRACE request
884   &MUST-NOT; include an entity.
885</t>
886<t>
887   TRACE allows the client to see what is being received at the other
888   end of the request chain and use that data for testing or diagnostic
889   information. The value of the Via header field (&header-via;) is of
890   particular interest, since it acts as a trace of the request chain.
891   Use of the Max-Forwards header field allows the client to limit the
892   length of the request chain, which is useful for testing a chain of
893   proxies forwarding messages in an infinite loop.
894</t>
895<t>
896   If the request is valid, the response &SHOULD; contain the entire
897   request message in the entity-body, with a Content-Type of
898   "message/http". Responses to this method &MUST-NOT; be cached.
899</t>
900</section>
901
902<section title="CONNECT" anchor="CONNECT">
903  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
904  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
905<t>
906   This specification reserves the method name CONNECT for use with a
907   proxy that can dynamically switch to being a tunnel (e.g. SSL
908   tunneling <xref target="Luo1998"/>).
909</t>
910</section>
911</section>
912
913
914<section title="Status Code Definitions" anchor="status.codes">
915<t>
916   Each Status-Code is described below, including a description of which
917   method(s) it can follow and any metainformation required in the
918   response.
919</t>
920
921<section title="Informational 1xx" anchor="status.1xx">
922<t>
923   This class of status code indicates a provisional response,
924   consisting only of the Status-Line and optional headers, and is
925   terminated by an empty line. There are no required headers for this
926   class of status code. Since HTTP/1.0 did not define any 1xx status
927   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
928   except under experimental conditions.
929</t>
930<t>
931   A client &MUST; be prepared to accept one or more 1xx status responses
932   prior to a regular response, even if the client does not expect a 100
933   (Continue) status message. Unexpected 1xx status responses &MAY; be
934   ignored by a user agent.
935</t>
936<t>
937   Proxies &MUST; forward 1xx responses, unless the connection between the
938   proxy and its client has been closed, or unless the proxy itself
939   requested the generation of the 1xx response. (For example, if a
940   proxy adds a "Expect: 100-continue" field when it forwards a request,
941   then it need not forward the corresponding 100 (Continue)
942   response(s).)
943</t>
944
945<section title="100 Continue" anchor="status.100">
946  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
947  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
948<t>
949   The client &SHOULD; continue with its request. This interim response is
950   used to inform the client that the initial part of the request has
951   been received and has not yet been rejected by the server. The client
952   &SHOULD; continue by sending the remainder of the request or, if the
953   request has already been completed, ignore this response. The server
954   &MUST; send a final response after the request has been completed. See
955   &use100; for detailed discussion of the use and handling of this
956   status code.
957</t>
958</section>
959
960<section title="101 Switching Protocols" anchor="status.101">
961  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
962  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
963<t>
964   The server understands and is willing to comply with the client's
965   request, via the Upgrade message header field (&header-upgrade;), for a
966   change in the application protocol being used on this connection. The
967   server will switch protocols to those defined by the response's
968   Upgrade header field immediately after the empty line which
969   terminates the 101 response.
970</t>
971<t>
972   The protocol &SHOULD; be switched only when it is advantageous to do
973   so. For example, switching to a newer version of HTTP is advantageous
974   over older versions, and switching to a real-time, synchronous
975   protocol might be advantageous when delivering resources that use
976   such features.
977</t>
978</section>
979</section>
980
981<section title="Successful 2xx" anchor="status.2xx">
982<t>
983   This class of status code indicates that the client's request was
984   successfully received, understood, and accepted.
985</t>
986
987<section title="200 OK" anchor="status.200">
988  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
989  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
990<t>
991   The request has succeeded. The information returned with the response
992   is dependent on the method used in the request, for example:
993  <list style="hanging">
994    <t hangText="GET">
995          an entity corresponding to the requested resource is sent in
996          the response;
997    </t>
998    <t hangText="HEAD">
999          the entity-header fields corresponding to the requested
1000          resource are sent in the response without any message-body;
1001    </t>
1002    <t hangText="POST">
1003      an entity describing or containing the result of the action;
1004    </t>
1005    <t hangText="TRACE">
1006      an entity containing the request message as received by the
1007      end server.
1008    </t>
1009  </list>
1010</t>
1011</section>
1012
1013<section title="201 Created" anchor="status.201">
1014  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1015  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1016<t>
1017   The request has been fulfilled and resulted in a new resource being
1018   created. The newly created resource can be referenced by the URI(s)
1019   returned in the entity of the response, with the most specific URI
1020   for the resource given by a Location header field. The response
1021   &SHOULD; include an entity containing a list of resource
1022   characteristics and location(s) from which the user or user agent can
1023   choose the one most appropriate. The entity format is specified by
1024   the media type given in the Content-Type header field. The origin
1025   server &MUST; create the resource before returning the 201 status code.
1026   If the action cannot be carried out immediately, the server &SHOULD;
1027   respond with 202 (Accepted) response instead.
1028</t>
1029<t>
1030   A 201 response &MAY; contain an ETag response header field indicating
1031   the current value of the entity tag for the requested variant just
1032   created, see &header-etag;.
1033</t>
1034</section>
1035
1036<section title="202 Accepted" anchor="status.202">
1037  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1038  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1039<t>
1040   The request has been accepted for processing, but the processing has
1041   not been completed.  The request might or might not eventually be
1042   acted upon, as it might be disallowed when processing actually takes
1043   place. There is no facility for re-sending a status code from an
1044   asynchronous operation such as this.
1045</t>
1046<t>
1047   The 202 response is intentionally non-committal. Its purpose is to
1048   allow a server to accept a request for some other process (perhaps a
1049   batch-oriented process that is only run once per day) without
1050   requiring that the user agent's connection to the server persist
1051   until the process is completed. The entity returned with this
1052   response &SHOULD; include an indication of the request's current status
1053   and either a pointer to a status monitor or some estimate of when the
1054   user can expect the request to be fulfilled.
1055</t>
1056</section>
1057
1058<section title="203 Non-Authoritative Information" anchor="status.203">
1059  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1060  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1061<t>
1062   The returned metainformation in the entity-header is not the
1063   definitive set as available from the origin server, but is gathered
1064   from a local or a third-party copy. The set presented &MAY; be a subset
1065   or superset of the original version. For example, including local
1066   annotation information about the resource might result in a superset
1067   of the metainformation known by the origin server. Use of this
1068   response code is not required and is only appropriate when the
1069   response would otherwise be 200 (OK).
1070</t>
1071</section>
1072
1073<section title="204 No Content" anchor="status.204">
1074  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1075  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1076<t>
1077   The server has fulfilled the request but does not need to return an
1078   entity-body, and might want to return updated metainformation. The
1079   response &MAY; include new or updated metainformation in the form of
1080   entity-headers, which if present &SHOULD; be associated with the
1081   requested variant.
1082</t>
1083<t>
1084   If the client is a user agent, it &SHOULD-NOT;  change its document view
1085   from that which caused the request to be sent. This response is
1086   primarily intended to allow input for actions to take place without
1087   causing a change to the user agent's active document view, although
1088   any new or updated metainformation &SHOULD; be applied to the document
1089   currently in the user agent's active view.
1090</t>
1091<t>
1092   The 204 response &MUST-NOT; include a message-body, and thus is always
1093   terminated by the first empty line after the header fields.
1094</t>
1095</section>
1096
1097<section title="205 Reset Content" anchor="status.205">
1098  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1099  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1100<t>
1101   The server has fulfilled the request and the user agent &SHOULD; reset
1102   the document view which caused the request to be sent. This response
1103   is primarily intended to allow input for actions to take place via
1104   user input, followed by a clearing of the form in which the input is
1105   given so that the user can easily initiate another input action. The
1106   response &MUST-NOT; include an entity.
1107</t>
1108</section>
1109
1110<section title="206 Partial Content" anchor="status.206">
1111  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1112  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1113<t>
1114   The server has fulfilled the partial GET request for the resource
1115   and the enclosed entity is a partial representation as defined in &range;.
1116</t>
1117</section>
1118</section>
1119
1120<section title="Redirection 3xx" anchor="status.3xx">
1121<t>
1122   This class of status code indicates that further action needs to be
1123   taken by the user agent in order to fulfill the request.  The action
1124   required &MAY; be carried out by the user agent without interaction
1125   with the user if and only if the method used in the second request is
1126   GET or HEAD. A client &SHOULD; detect infinite redirection loops, since
1127   such loops generate network traffic for each redirection.
1128  <list><t>
1129      <x:h>Note:</x:h> previous versions of this specification recommended a
1130      maximum of five redirections. Content developers should be aware
1131      that there might be clients that implement such a fixed
1132      limitation.
1133  </t></list>
1134</t>
1135
1136<section title="300 Multiple Choices" anchor="status.300">
1137  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1138  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1139<t>
1140   The requested resource corresponds to any one of a set of
1141   representations, each with its own specific location, and agent-driven
1142   negotiation information (&content-negotiation;) is being provided so that
1143   the user (or user agent) can select a preferred representation and
1144   redirect its request to that location.
1145</t>
1146<t>
1147   Unless it was a HEAD request, the response &SHOULD; include an entity
1148   containing a list of resource characteristics and location(s) from
1149   which the user or user agent can choose the one most appropriate. The
1150   entity format is specified by the media type given in the Content-Type
1151   header field. Depending upon the format and the capabilities of
1152   the user agent, selection of the most appropriate choice &MAY; be
1153   performed automatically. However, this specification does not define
1154   any standard for such automatic selection.
1155</t>
1156<t>
1157   If the server has a preferred choice of representation, it &SHOULD;
1158   include the specific URI for that representation in the Location
1159   field; user agents &MAY; use the Location field value for automatic
1160   redirection. This response is cacheable unless indicated otherwise.
1161</t>
1162</section>
1163
1164<section title="301 Moved Permanently" anchor="status.301">
1165  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1166  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1167<t>
1168   The requested resource has been assigned a new permanent URI and any
1169   future references to this resource &SHOULD; use one of the returned
1170   URIs.  Clients with link editing capabilities ought to automatically
1171   re-link references to the Request-URI to one or more of the new
1172   references returned by the server, where possible. This response is
1173   cacheable unless indicated otherwise.
1174</t>
1175<t>
1176   The new permanent URI &SHOULD; be given by the Location field in the
1177   response. Unless the request method was HEAD, the entity of the
1178   response &SHOULD; contain a short hypertext note with a hyperlink to
1179   the new URI(s).
1180</t>
1181<t>
1182   If the 301 status code is received in response to a request method
1183   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1184   then the request &MAY; be automatically redirected by the user agent without
1185   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1186   request unless it can be confirmed by the user, since this might
1187   change the conditions under which the request was issued.
1188  <list><t>
1189      <x:h>Note:</x:h> When automatically redirecting a POST request after
1190      receiving a 301 status code, some existing HTTP/1.0 user agents
1191      will erroneously change it into a GET request.
1192  </t></list>
1193</t>
1194</section>
1195
1196<section title="302 Found" anchor="status.302">
1197  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1198  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1199<t>
1200   The requested resource resides temporarily under a different URI.
1201   Since the redirection might be altered on occasion, the client &SHOULD;
1202   continue to use the Request-URI for future requests.  This response
1203   is only cacheable if indicated by a Cache-Control or Expires header
1204   field.
1205</t>
1206<t>
1207   The temporary URI &SHOULD; be given by the Location field in the
1208   response. Unless the request method was HEAD, the entity of the
1209   response &SHOULD; contain a short hypertext note with a hyperlink to
1210   the new URI(s).
1211</t>
1212<t>
1213   If the 302 status code is received in response to a request method
1214   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1215   then the request &MAY; be automatically redirected by the user agent without
1216   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1217   request unless it can be confirmed by the user, since this might
1218   change the conditions under which the request was issued.
1219  <list><t>
1220      <x:h>Note:</x:h> <xref target="RFC1945"/> and <xref target="RFC2068"/> specify that the client is not allowed
1221      to change the method on the redirected request.  However, most
1222      existing user agent implementations treat 302 as if it were a 303
1223      response, performing a GET on the Location field-value regardless
1224      of the original request method. The status codes 303 and 307 have
1225      been added for servers that wish to make unambiguously clear which
1226      kind of reaction is expected of the client.
1227  </t></list>
1228</t>
1229</section>
1230
1231<section title="303 See Other" anchor="status.303">
1232  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1233  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1234<t>
1235   The response to the request can be found under a different URI and
1236   &SHOULD; be retrieved using a GET method on that resource. This method
1237   exists primarily to allow the output of a POST-activated script to
1238   redirect the user agent to a selected resource. The new URI is not a
1239   substitute reference for the originally requested resource. The 303
1240   response &MUST-NOT; be cached, but the response to the second
1241   (redirected) request might be cacheable.
1242</t>
1243<t>
1244   The different URI &SHOULD; be given by the Location field in the
1245   response. Unless the request method was HEAD, the entity of the
1246   response &SHOULD; contain a short hypertext note with a hyperlink to
1247   the new URI(s).
1248  <list><t>
1249      <x:h>Note:</x:h> Many pre-HTTP/1.1 user agents do not understand the 303
1250      status. When interoperability with such clients is a concern, the
1251      302 status code may be used instead, since most user agents react
1252      to a 302 response as described here for 303.
1253  </t></list>
1254</t>
1255</section>
1256
1257<section title="304 Not Modified" anchor="status.304">
1258  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1259  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1260<t>
1261   The response to the request has not been modified since the conditions
1262   indicated by the client's conditional GET request, as defined in &conditional;.
1263</t>
1264</section>
1265
1266<section title="305 Use Proxy" anchor="status.305">
1267  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1268  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1269<t>
1270   The requested resource &MUST; be accessed through the proxy given by
1271   the Location field. The Location field gives the URI of the proxy.
1272   The recipient is expected to repeat this single request via the
1273   proxy. 305 responses &MUST; only be generated by origin servers.
1274  <list><t>
1275      <x:h>Note:</x:h> <xref target="RFC2068"/> was not clear that 305 was intended to redirect a
1276      single request, and to be generated by origin servers only.  Not
1277      observing these limitations has significant security consequences.
1278  </t></list>
1279</t>
1280</section>
1281
1282<section title="306 (Unused)" anchor="status.306">
1283  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1284  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1285<t>
1286   The 306 status code was used in a previous version of the
1287   specification, is no longer used, and the code is reserved.
1288</t>
1289</section>
1290
1291<section title="307 Temporary Redirect" anchor="status.307">
1292  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1293  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1294<t>
1295   The requested resource resides temporarily under a different URI.
1296   Since the redirection &MAY; be altered on occasion, the client &SHOULD;
1297   continue to use the Request-URI for future requests.  This response
1298   is only cacheable if indicated by a Cache-Control or Expires header
1299   field.
1300</t>
1301<t>
1302   The temporary URI &SHOULD; be given by the Location field in the
1303   response. Unless the request method was HEAD, the entity of the
1304   response &SHOULD; contain a short hypertext note with a hyperlink to
1305   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1306   understand the 307 status. Therefore, the note &SHOULD; contain the
1307   information necessary for a user to repeat the original request on
1308   the new URI.
1309</t>
1310<t>
1311   If the 307 status code is received in response to a request method
1312   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1313   then the request &MAY; be automatically redirected by the user agent without
1314   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1315   request unless it can be confirmed by the user, since this might
1316   change the conditions under which the request was issued.
1317</t>
1318</section>
1319</section>
1320
1321<section title="Client Error 4xx" anchor="status.4xx">
1322<t>
1323   The 4xx class of status code is intended for cases in which the
1324   client seems to have erred. Except when responding to a HEAD request,
1325   the server &SHOULD; include an entity containing an explanation of the
1326   error situation, and whether it is a temporary or permanent
1327   condition. These status codes are applicable to any request method.
1328   User agents &SHOULD; display any included entity to the user.
1329</t>
1330<t>
1331   If the client is sending data, a server implementation using TCP
1332   &SHOULD; be careful to ensure that the client acknowledges receipt of
1333   the packet(s) containing the response, before the server closes the
1334   input connection. If the client continues sending data to the server
1335   after the close, the server's TCP stack will send a reset packet to
1336   the client, which may erase the client's unacknowledged input buffers
1337   before they can be read and interpreted by the HTTP application.
1338</t>
1339
1340<section title="400 Bad Request" anchor="status.400">
1341  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1342  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1343<t>
1344   The request could not be understood by the server due to malformed
1345   syntax. The client &SHOULD-NOT;  repeat the request without
1346   modifications.
1347</t>
1348</section>
1349
1350<section title="401 Unauthorized" anchor="status.401">
1351  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1352  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1353<t>
1354   The request requires user authentication (see &auth;).
1355</t>
1356</section>
1357
1358<section title="402 Payment Required" anchor="status.402">
1359  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1360  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1361<t>
1362   This code is reserved for future use.
1363</t>
1364</section>
1365
1366<section title="403 Forbidden" anchor="status.403">
1367  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1368  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1369<t>
1370   The server understood the request, but is refusing to fulfill it.
1371   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1372   If the request method was not HEAD and the server wishes to make
1373   public why the request has not been fulfilled, it &SHOULD; describe the
1374   reason for the refusal in the entity.  If the server does not wish to
1375   make this information available to the client, the status code 404
1376   (Not Found) can be used instead.
1377</t>
1378</section>
1379
1380<section title="404 Not Found" anchor="status.404">
1381  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1382  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1383<t>
1384   The server has not found anything matching the Request-URI. No
1385   indication is given of whether the condition is temporary or
1386   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1387   knows, through some internally configurable mechanism, that an old
1388   resource is permanently unavailable and has no forwarding address.
1389   This status code is commonly used when the server does not wish to
1390   reveal exactly why the request has been refused, or when no other
1391   response is applicable.
1392</t>
1393</section>
1394
1395<section title="405 Method Not Allowed" anchor="status.405">
1396  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1397  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1398<t>
1399   The method specified in the Request-Line is not allowed for the
1400   resource identified by the Request-URI. The response &MUST; include an
1401   Allow header containing a list of valid methods for the requested
1402   resource.
1403</t>
1404</section>
1405
1406<section title="406 Not Acceptable" anchor="status.406">
1407  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1408  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1409<t>
1410   The resource identified by the request is only capable of generating
1411   response entities which have content characteristics not acceptable
1412   according to the accept headers sent in the request.
1413</t>
1414<t>
1415   Unless it was a HEAD request, the response &SHOULD; include an entity
1416   containing a list of available entity characteristics and location(s)
1417   from which the user or user agent can choose the one most
1418   appropriate. The entity format is specified by the media type given
1419   in the Content-Type header field. Depending upon the format and the
1420   capabilities of the user agent, selection of the most appropriate
1421   choice &MAY; be performed automatically. However, this specification
1422   does not define any standard for such automatic selection.
1423  <list><t>
1424      <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1425      not acceptable according to the accept headers sent in the
1426      request. In some cases, this may even be preferable to sending a
1427      406 response. User agents are encouraged to inspect the headers of
1428      an incoming response to determine if it is acceptable.
1429  </t></list>
1430</t>
1431<t>
1432   If the response could be unacceptable, a user agent &SHOULD;
1433   temporarily stop receipt of more data and query the user for a
1434   decision on further actions.
1435</t>
1436</section>
1437
1438<section title="407 Proxy Authentication Required" anchor="status.407">
1439  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1440  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1441<t>
1442   This code is similar to 401 (Unauthorized), but indicates that the
1443   client must first authenticate itself with the proxy (see &auth;).
1444</t>
1445</section>
1446
1447<section title="408 Request Timeout" anchor="status.408">
1448  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1449  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1450<t>
1451   The client did not produce a request within the time that the server
1452   was prepared to wait. The client &MAY; repeat the request without
1453   modifications at any later time.
1454</t>
1455</section>
1456
1457<section title="409 Conflict" anchor="status.409">
1458  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1459  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1460<t>
1461   The request could not be completed due to a conflict with the current
1462   state of the resource. This code is only allowed in situations where
1463   it is expected that the user might be able to resolve the conflict
1464   and resubmit the request. The response body &SHOULD; include enough
1465   information for the user to recognize the source of the conflict.
1466   Ideally, the response entity would include enough information for the
1467   user or user agent to fix the problem; however, that might not be
1468   possible and is not required.
1469</t>
1470<t>
1471   Conflicts are most likely to occur in response to a PUT request. For
1472   example, if versioning were being used and the entity being PUT
1473   included changes to a resource which conflict with those made by an
1474   earlier (third-party) request, the server might use the 409 response
1475   to indicate that it can't complete the request. In this case, the
1476   response entity would likely contain a list of the differences
1477   between the two versions in a format defined by the response
1478   Content-Type.
1479</t>
1480</section>
1481
1482<section title="410 Gone" anchor="status.410">
1483  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1484  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1485<t>
1486   The requested resource is no longer available at the server and no
1487   forwarding address is known. This condition is expected to be
1488   considered permanent. Clients with link editing capabilities &SHOULD;
1489   delete references to the Request-URI after user approval. If the
1490   server does not know, or has no facility to determine, whether or not
1491   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1492   used instead. This response is cacheable unless indicated otherwise.
1493</t>
1494<t>
1495   The 410 response is primarily intended to assist the task of web
1496   maintenance by notifying the recipient that the resource is
1497   intentionally unavailable and that the server owners desire that
1498   remote links to that resource be removed. Such an event is common for
1499   limited-time, promotional services and for resources belonging to
1500   individuals no longer working at the server's site. It is not
1501   necessary to mark all permanently unavailable resources as "gone" or
1502   to keep the mark for any length of time -- that is left to the
1503   discretion of the server owner.
1504</t>
1505</section>
1506
1507<section title="411 Length Required" anchor="status.411">
1508  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1509  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1510<t>
1511   The server refuses to accept the request without a defined Content-Length.
1512   The client &MAY; repeat the request if it adds a valid
1513   Content-Length header field containing the length of the message-body
1514   in the request message.
1515</t>
1516</section>
1517
1518<section title="412 Precondition Failed" anchor="status.412">
1519  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1520  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1521<t>
1522   The precondition given in one or more of the request-header fields
1523   evaluated to false when it was tested on the server, as defined in
1524   &conditional;.
1525</t>
1526</section>
1527
1528<section title="413 Request Entity Too Large" anchor="status.413">
1529  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1530  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1531<t>
1532   The server is refusing to process a request because the request
1533   entity is larger than the server is willing or able to process. The
1534   server &MAY; close the connection to prevent the client from continuing
1535   the request.
1536</t>
1537<t>
1538   If the condition is temporary, the server &SHOULD; include a Retry-After
1539   header field to indicate that it is temporary and after what
1540   time the client &MAY; try again.
1541</t>
1542</section>
1543
1544<section title="414 Request-URI Too Long" anchor="status.414">
1545  <iref primary="true" item="414 Request-URI Too Long (status code)" x:for-anchor=""/>
1546  <iref primary="true" item="Status Codes" subitem="414 Request-URI Too Long" x:for-anchor=""/>
1547<t>
1548   The server is refusing to service the request because the Request-URI
1549   is longer than the server is willing to interpret. This rare
1550   condition is only likely to occur when a client has improperly
1551   converted a POST request to a GET request with long query
1552   information, when the client has descended into a URI "black hole" of
1553   redirection (e.g., a redirected URI prefix that points to a suffix of
1554   itself), or when the server is under attack by a client attempting to
1555   exploit security holes present in some servers using fixed-length
1556   buffers for reading or manipulating the Request-URI.
1557</t>
1558</section>
1559
1560<section title="415 Unsupported Media Type" anchor="status.415">
1561  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1562  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1563<t>
1564   The server is refusing to service the request because the entity of
1565   the request is in a format not supported by the requested resource
1566   for the requested method.
1567</t>
1568</section>
1569
1570<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1571  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1572  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1573<t>
1574   The request included a Range request-header field (&header-range;) and none of
1575   the range-specifier values in this field overlap the current extent
1576   of the selected resource.
1577</t>
1578</section>
1579
1580<section title="417 Expectation Failed" anchor="status.417">
1581  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1582  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1583<t>
1584   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1585   could not be met by this server, or, if the server is a proxy,
1586   the server has unambiguous evidence that the request could not be met
1587   by the next-hop server.
1588</t>
1589</section>
1590</section>
1591
1592<section title="Server Error 5xx" anchor="status.5xx">
1593<t>
1594   Response status codes beginning with the digit "5" indicate cases in
1595   which the server is aware that it has erred or is incapable of
1596   performing the request. Except when responding to a HEAD request, the
1597   server &SHOULD; include an entity containing an explanation of the
1598   error situation, and whether it is a temporary or permanent
1599   condition. User agents &SHOULD; display any included entity to the
1600   user. These response codes are applicable to any request method.
1601</t>
1602
1603<section title="500 Internal Server Error" anchor="status.500">
1604  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1605  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1606<t>
1607   The server encountered an unexpected condition which prevented it
1608   from fulfilling the request.
1609</t>
1610</section>
1611
1612<section title="501 Not Implemented" anchor="status.501">
1613  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1614  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1615<t>
1616   The server does not support the functionality required to fulfill the
1617   request. This is the appropriate response when the server does not
1618   recognize the request method and is not capable of supporting it for
1619   any resource.
1620</t>
1621</section>
1622
1623<section title="502 Bad Gateway" anchor="status.502">
1624  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1625  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1626<t>
1627   The server, while acting as a gateway or proxy, received an invalid
1628   response from the upstream server it accessed in attempting to
1629   fulfill the request.
1630</t>
1631</section>
1632
1633<section title="503 Service Unavailable" anchor="status.503">
1634  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1635  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1636<t>
1637   The server is currently unable to handle the request due to a
1638   temporary overloading or maintenance of the server. The implication
1639   is that this is a temporary condition which will be alleviated after
1640   some delay. If known, the length of the delay &MAY; be indicated in a
1641   Retry-After header. If no Retry-After is given, the client &SHOULD;
1642   handle the response as it would for a 500 response.
1643  <list><t>
1644      <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1645      server must use it when becoming overloaded. Some servers may wish
1646      to simply refuse the connection.
1647  </t></list>
1648</t>
1649</section>
1650
1651<section title="504 Gateway Timeout" anchor="status.504">
1652  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1653  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1654<t>
1655   The server, while acting as a gateway or proxy, did not receive a
1656   timely response from the upstream server specified by the URI (e.g.
1657   HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed
1658   to access in attempting to complete the request.
1659  <list><t>
1660      <x:h>Note:</x:h> Note to implementors: some deployed proxies are known to
1661      return 400 or 500 when DNS lookups time out.
1662  </t></list>
1663</t>
1664</section>
1665
1666<section title="505 HTTP Version Not Supported" anchor="status.505">
1667  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1668  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
1669<t>
1670   The server does not support, or refuses to support, the protocol
1671   version that was used in the request message. The server is
1672   indicating that it is unable or unwilling to complete the request
1673   using the same major version as the client, as described in &http-version;,
1674   other than with this error message. The response &SHOULD; contain
1675   an entity describing why that version is not supported and what other
1676   protocols are supported by that server.
1677</t>
1678
1679</section>
1680</section>
1681</section>
1682
1683
1684<section title="Header Field Definitions" anchor="header.fields">
1685<t>
1686   This section defines the syntax and semantics of HTTP/1.1 header fields
1687   related to request and response semantics.
1688</t>
1689<t>
1690   For entity-header fields, both sender and recipient refer to either the
1691   client or the server, depending on who sends and who receives the entity.
1692</t>
1693
1694<section title="Allow" anchor="header.allow">
1695  <iref primary="true" item="Allow header" x:for-anchor=""/>
1696  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
1697<t>
1698      The Allow entity-header field lists the set of methods supported
1699      by the resource identified by the Request-URI. The purpose of this
1700      field is strictly to inform the recipient of valid methods
1701      associated with the resource. An Allow header field &MUST; be
1702      present in a 405 (Method Not Allowed) response.
1703</t>
1704<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/>
1705  Allow   = "Allow" ":" #Method
1706</artwork></figure>
1707<t>
1708      Example of use:
1709</t>
1710<figure><artwork type="example">
1711       Allow: GET, HEAD, PUT
1712</artwork></figure>
1713<t>
1714      This field cannot prevent a client from trying other methods.
1715      However, the indications given by the Allow header field value
1716      &SHOULD; be followed. The actual set of allowed methods is defined
1717      by the origin server at the time of each request.
1718</t>
1719<t>
1720      The Allow header field &MAY; be provided with a PUT request to
1721      recommend the methods to be supported by the new or modified
1722      resource. The server is not required to support these methods and
1723      &SHOULD; include an Allow header in the response giving the actual
1724      supported methods.
1725</t>
1726<t>
1727      A proxy &MUST-NOT; modify the Allow header field even if it does not
1728      understand all the methods specified, since the user agent might
1729      have other means of communicating with the origin server.
1730</t>
1731</section>
1732
1733<section title="Expect" anchor="header.expect">
1734  <iref primary="true" item="Expect header" x:for-anchor=""/>
1735  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
1736<t>
1737   The Expect request-header field is used to indicate that particular
1738   server behaviors are required by the client.
1739</t>
1740<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"/>
1741  Expect       =  "Expect" ":" 1#expectation
1742 
1743  expectation  =  "100-continue" | expectation-extension
1744  expectation-extension =  token [ "=" ( token | quoted-string )
1745                           *expect-params ]
1746  expect-params =  ";" token [ "=" ( token | quoted-string ) ]
1747</artwork></figure>
1748<t>
1749   A server that does not understand or is unable to comply with any of
1750   the expectation values in the Expect field of a request &MUST; respond
1751   with appropriate error status. The server &MUST; respond with a 417
1752   (Expectation Failed) status if any of the expectations cannot be met
1753   or, if there are other problems with the request, some other 4xx
1754   status.
1755</t>
1756<t>
1757   This header field is defined with extensible syntax to allow for
1758   future extensions. If a server receives a request containing an
1759   Expect field that includes an expectation-extension that it does not
1760   support, it &MUST; respond with a 417 (Expectation Failed) status.
1761</t>
1762<t>
1763   Comparison of expectation values is case-insensitive for unquoted
1764   tokens (including the 100-continue token), and is case-sensitive for
1765   quoted-string expectation-extensions.
1766</t>
1767<t>
1768   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
1769   return a 417 (Expectation Failed) status if it receives a request
1770   with an expectation that it cannot meet. However, the Expect
1771   request-header itself is end-to-end; it &MUST; be forwarded if the
1772   request is forwarded.
1773</t>
1774<t>
1775   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1776   Expect header.
1777</t>
1778<t>
1779   See &use100; for the use of the 100 (Continue) status.
1780</t>
1781</section>
1782
1783<section title="From" anchor="header.from">
1784  <iref primary="true" item="From header" x:for-anchor=""/>
1785  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
1786<t>
1787   The From request-header field, if given, &SHOULD; contain an Internet
1788   e-mail address for the human user who controls the requesting user
1789   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
1790   in <xref x:sec="3.4" x:fmt="of" target="RFC2822"/>:
1791</t>
1792<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/>
1793  From    = "From" ":" mailbox
1794 
1795  mailbox = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC2822"/>&gt;
1796</artwork></figure>
1797<t>
1798   An example is:
1799</t>
1800<figure><artwork type="example">
1801    From: webmaster@example.org
1802</artwork></figure>
1803<t>
1804   This header field &MAY; be used for logging purposes and as a means for
1805   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
1806   be used as an insecure form of access protection. The interpretation
1807   of this field is that the request is being performed on behalf of the
1808   person given, who accepts responsibility for the method performed. In
1809   particular, robot agents &SHOULD; include this header so that the
1810   person responsible for running the robot can be contacted if problems
1811   occur on the receiving end.
1812</t>
1813<t>
1814   The Internet e-mail address in this field &MAY; be separate from the
1815   Internet host which issued the request. For example, when a request
1816   is passed through a proxy the original issuer's address &SHOULD; be
1817   used.
1818</t>
1819<t>
1820   The client &SHOULD-NOT;  send the From header field without the user's
1821   approval, as it might conflict with the user's privacy interests or
1822   their site's security policy. It is strongly recommended that the
1823   user be able to disable, enable, and modify the value of this field
1824   at any time prior to a request.
1825</t>
1826</section>
1827
1828<section title="Location" anchor="header.location">
1829  <iref primary="true" item="Location header" x:for-anchor=""/>
1830  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
1831<t>
1832   The Location response-header field is used to redirect the recipient
1833   to a location other than the Request-URI for completion of the
1834   request or identification of a new resource. For 201 (Created)
1835   responses, the Location is that of the new resource which was created
1836   by the request. For 3xx responses, the location &SHOULD; indicate the
1837   server's preferred URI for automatic redirection to the resource. The
1838   field value consists of a single absolute URI.
1839</t>
1840<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/>
1841  Location       = "Location" ":" absoluteURI [ "#" fragment ]
1842</artwork></figure>
1843<t>
1844   An example is:
1845</t>
1846<figure><artwork type="example">
1847    Location: http://www.example.org/pub/WWW/People.html
1848</artwork></figure>
1849<t>
1850  <list><t>
1851      <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
1852      from Location in that the Content-Location identifies the original
1853      location of the entity enclosed in the request. It is therefore
1854      possible for a response to contain header fields for both Location
1855      and Content-Location.
1856  </t></list>
1857</t>
1858<t>
1859   There are circumstances in which a fragment identifier in a Location URL would not be appropriate:
1860   <list style="symbols">
1861      <t>With a 201 Created response, because in this usage the Location header specifies the URL for the entire created resource.</t>
1862      <t>With a 300 Multiple Choices, since the choice decision is intended to be made on resource characteristics and not fragment characteristics.</t>
1863      <t>With 305 Use Proxy.</t>
1864   </list>
1865</t>
1866</section>
1867
1868<section title="Max-Forwards" anchor="header.max-forwards">
1869  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
1870  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
1871<t>
1872   The Max-Forwards request-header field provides a mechanism with the
1873   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>) methods to limit the
1874   number of proxies or gateways that can forward the request to the
1875   next inbound server. This can be useful when the client is attempting
1876   to trace a request chain which appears to be failing or looping in
1877   mid-chain.
1878</t>
1879<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/>
1880  Max-Forwards   = "Max-Forwards" ":" 1*DIGIT
1881</artwork></figure>
1882<t>
1883   The Max-Forwards value is a decimal integer indicating the remaining
1884   number of times this request message may be forwarded.
1885</t>
1886<t>
1887   Each proxy or gateway recipient of a TRACE or OPTIONS request
1888   containing a Max-Forwards header field &MUST; check and update its
1889   value prior to forwarding the request. If the received value is zero
1890   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
1891   respond as the final recipient. If the received Max-Forwards value is
1892   greater than zero, then the forwarded message &MUST; contain an updated
1893   Max-Forwards field with a value decremented by one (1).
1894</t>
1895<t>
1896   The Max-Forwards header field &MAY; be ignored for all other methods
1897   defined by this specification and for any extension methods for which
1898   it is not explicitly referred to as part of that method definition.
1899</t>
1900</section>
1901
1902<section title="Referer" anchor="header.referer">
1903  <iref primary="true" item="Referer header" x:for-anchor=""/>
1904  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
1905<t>
1906   The Referer[sic] request-header field allows the client to specify,
1907   for the server's benefit, the address (URI) of the resource from
1908   which the Request-URI was obtained (the "referrer", although the
1909   header field is misspelled.) The Referer request-header allows a
1910   server to generate lists of back-links to resources for interest,
1911   logging, optimized caching, etc. It also allows obsolete or mistyped
1912   links to be traced for maintenance. The Referer field &MUST-NOT; be
1913   sent if the Request-URI was obtained from a source that does not have
1914   its own URI, such as input from the user keyboard.
1915</t>
1916<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/>
1917  Referer        = "Referer" ":" ( absoluteURI | relativeURI )
1918</artwork></figure>
1919<t>
1920   Example:
1921</t>
1922<figure><artwork type="example">
1923    Referer: http://www.example.org/hypertext/Overview.html
1924</artwork></figure>
1925<t>
1926   If the field value is a relative URI, it &SHOULD; be interpreted
1927   relative to the Request-URI. The URI &MUST-NOT; include a fragment. See
1928   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
1929</t>
1930</section>
1931
1932<section title="Retry-After" anchor="header.retry-after">
1933  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
1934  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
1935<t>
1936   The Retry-After response-header field can be used with a 503 (Service
1937   Unavailable) response to indicate how long the service is expected to
1938   be unavailable to the requesting client. This field &MAY; also be used
1939   with any 3xx (Redirection) response to indicate the minimum time the
1940   user-agent is asked wait before issuing the redirected request. The
1941   value of this field can be either an HTTP-date or an integer number
1942   of seconds (in decimal) after the time of the response.
1943</t>
1944<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/>
1945  Retry-After  = "Retry-After" ":" ( HTTP-date | delta-seconds )
1946</artwork></figure>
1947<t>
1948   Two examples of its use are
1949</t>
1950<figure><artwork type="example">
1951    Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
1952    Retry-After: 120
1953</artwork></figure>
1954<t>
1955   In the latter example, the delay is 2 minutes.
1956</t>
1957</section>
1958
1959<section title="Server" anchor="header.server">
1960  <iref primary="true" item="Server header" x:for-anchor=""/>
1961  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
1962<t>
1963   The Server response-header field contains information about the
1964   software used by the origin server to handle the request. The field
1965   can contain multiple product tokens (&product-tokens;) and comments
1966   identifying the server and any significant subproducts. The product
1967   tokens are listed in order of their significance for identifying the
1968   application.
1969</t>
1970<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/>
1971  Server         = "Server" ":" 1*( product | comment )
1972</artwork></figure>
1973<t>
1974   Example:
1975</t>
1976<figure><artwork type="example">
1977    Server: CERN/3.0 libwww/2.17
1978</artwork></figure>
1979<t>
1980   If the response is being forwarded through a proxy, the proxy
1981   application &MUST-NOT; modify the Server response-header. Instead, it
1982   &MUST; include a Via field (as described in &header-via;).
1983  <list><t>
1984      <x:h>Note:</x:h> Revealing the specific software version of the server might
1985      allow the server machine to become more vulnerable to attacks
1986      against software that is known to contain security holes. Server
1987      implementors are encouraged to make this field a configurable
1988      option.
1989  </t></list>
1990</t>
1991</section>
1992
1993<section title="User-Agent" anchor="header.user-agent">
1994  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
1995  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
1996<t>
1997   The User-Agent request-header field contains information about the
1998   user agent originating the request. This is for statistical purposes,
1999   the tracing of protocol violations, and automated recognition of user
2000   agents for the sake of tailoring responses to avoid particular user
2001   agent limitations. User agents &SHOULD; include this field with
2002   requests. The field can contain multiple product tokens (&product-tokens;)
2003   and comments identifying the agent and any subproducts which form a
2004   significant part of the user agent. By convention, the product tokens
2005   are listed in order of their significance for identifying the
2006   application.
2007</t>
2008<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/>
2009  User-Agent     = "User-Agent" ":" 1*( product | comment )
2010</artwork></figure>
2011<t>
2012   Example:
2013</t>
2014<figure><artwork type="example">
2015    User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2016</artwork></figure>
2017</section>
2018
2019</section>
2020
2021<section title="IANA Considerations" anchor="IANA.considerations">
2022<t>
2023   <cref>TBD.</cref>
2024</t>
2025</section>
2026
2027<section title="Security Considerations" anchor="security.considerations">
2028<t>
2029   This section is meant to inform application developers, information
2030   providers, and users of the security limitations in HTTP/1.1 as
2031   described by this document. The discussion does not include
2032   definitive solutions to the problems revealed, though it does make
2033   some suggestions for reducing security risks.
2034</t>
2035
2036<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2037<t>
2038   Like any generic data transfer protocol, HTTP cannot regulate the
2039   content of the data that is transferred, nor is there any a priori
2040   method of determining the sensitivity of any particular piece of
2041   information within the context of any given request. Therefore,
2042   applications &SHOULD; supply as much control over this information as
2043   possible to the provider of that information. Four header fields are
2044   worth special mention in this context: Server, Via, Referer and From.
2045</t>
2046<t>
2047   Revealing the specific software version of the server might allow the
2048   server machine to become more vulnerable to attacks against software
2049   that is known to contain security holes. Implementors &SHOULD; make the
2050   Server header field a configurable option.
2051</t>
2052<t>
2053   Proxies which serve as a portal through a network firewall &SHOULD;
2054   take special precautions regarding the transfer of header information
2055   that identifies the hosts behind the firewall. In particular, they
2056   &SHOULD; remove, or replace with sanitized versions, any Via fields
2057   generated behind the firewall.
2058</t>
2059<t>
2060   The Referer header allows reading patterns to be studied and reverse
2061   links drawn. Although it can be very useful, its power can be abused
2062   if user details are not separated from the information contained in
2063   the Referer. Even when the personal information has been removed, the
2064   Referer header might indicate a private document's URI whose
2065   publication would be inappropriate.
2066</t>
2067<t>
2068   The information sent in the From field might conflict with the user's
2069   privacy interests or their site's security policy, and hence it
2070   &SHOULD-NOT;  be transmitted without the user being able to disable,
2071   enable, and modify the contents of the field. The user &MUST; be able
2072   to set the contents of this field within a user preference or
2073   application defaults configuration.
2074</t>
2075<t>
2076   We suggest, though do not require, that a convenient toggle interface
2077   be provided for the user to enable or disable the sending of From and
2078   Referer information.
2079</t>
2080<t>
2081   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2082   fields can sometimes be used to determine that a specific client or
2083   server have a particular security hole which might be exploited.
2084   Unfortunately, this same information is often used for other valuable
2085   purposes for which HTTP currently has no better mechanism.
2086</t>
2087</section>
2088
2089<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2090<t>
2091   Because the source of a link might be private information or might
2092   reveal an otherwise private information source, it is strongly
2093   recommended that the user be able to select whether or not the
2094   Referer field is sent. For example, a browser client could have a
2095   toggle switch for browsing openly/anonymously, which would
2096   respectively enable/disable the sending of Referer and From
2097   information.
2098</t>
2099<t>
2100   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2101   HTTP request if the referring page was transferred with a secure
2102   protocol.
2103</t>
2104<t>
2105   Authors of services should not use
2106   GET-based forms for the submission of sensitive data because that
2107   data will be encoded in the Request-URI. Many existing
2108   servers, proxies, and user agents log or display the Request-URI in
2109   places where it might be visible to third parties. Such services can
2110   use POST-based form submission instead.
2111</t>
2112</section>
2113
2114<section title="Location Headers and Spoofing" anchor="location.spoofing">
2115<t>
2116   If a single server supports multiple organizations that do not trust
2117   one another, then it &MUST; check the values of Location and Content-Location
2118   headers in responses that are generated under control of
2119   said organizations to make sure that they do not attempt to
2120   invalidate resources over which they have no authority.
2121</t>
2122</section>
2123
2124</section>
2125
2126<section title="Acknowledgments" anchor="ack">
2127</section>
2128</middle>
2129<back>
2130
2131<references title="Normative References">
2132
2133<reference anchor="Part1">
2134  <front>
2135    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2136    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2137      <organization abbrev="Day Software">Day Software</organization>
2138      <address><email>fielding@gbiv.com</email></address>
2139    </author>
2140    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2141      <organization>One Laptop per Child</organization>
2142      <address><email>jg@laptop.org</email></address>
2143    </author>
2144    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2145      <organization abbrev="HP">Hewlett-Packard Company</organization>
2146      <address><email>JeffMogul@acm.org</email></address>
2147    </author>
2148    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2149      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2150      <address><email>henrikn@microsoft.com</email></address>
2151    </author>
2152    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2153      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2154      <address><email>LMM@acm.org</email></address>
2155    </author>
2156    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2157      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2158      <address><email>paulle@microsoft.com</email></address>
2159    </author>
2160    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2161      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2162      <address><email>timbl@w3.org</email></address>
2163    </author>
2164    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2165      <organization abbrev="W3C">World Wide Web Consortium</organization>
2166      <address><email>ylafon@w3.org</email></address>
2167    </author>
2168    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2169      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2170      <address><email>julian.reschke@greenbytes.de</email></address>
2171    </author>
2172    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2173  </front>
2174  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2175  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2176</reference>
2177
2178<reference anchor="Part3">
2179  <front>
2180    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2181    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2182      <organization abbrev="Day Software">Day Software</organization>
2183      <address><email>fielding@gbiv.com</email></address>
2184    </author>
2185    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2186      <organization>One Laptop per Child</organization>
2187      <address><email>jg@laptop.org</email></address>
2188    </author>
2189    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2190      <organization abbrev="HP">Hewlett-Packard Company</organization>
2191      <address><email>JeffMogul@acm.org</email></address>
2192    </author>
2193    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2194      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2195      <address><email>henrikn@microsoft.com</email></address>
2196    </author>
2197    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2198      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2199      <address><email>LMM@acm.org</email></address>
2200    </author>
2201    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2202      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2203      <address><email>paulle@microsoft.com</email></address>
2204    </author>
2205    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2206      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2207      <address><email>timbl@w3.org</email></address>
2208    </author>
2209    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2210      <organization abbrev="W3C">World Wide Web Consortium</organization>
2211      <address><email>ylafon@w3.org</email></address>
2212    </author>
2213    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2214      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2215      <address><email>julian.reschke@greenbytes.de</email></address>
2216    </author>
2217    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2218  </front>
2219  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2220  <x:source href="p3-payload.xml" basename="p3-payload"/>
2221</reference>
2222
2223<reference anchor="Part4">
2224  <front>
2225    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2226    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2227      <organization abbrev="Day Software">Day Software</organization>
2228      <address><email>fielding@gbiv.com</email></address>
2229    </author>
2230    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2231      <organization>One Laptop per Child</organization>
2232      <address><email>jg@laptop.org</email></address>
2233    </author>
2234    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2235      <organization abbrev="HP">Hewlett-Packard Company</organization>
2236      <address><email>JeffMogul@acm.org</email></address>
2237    </author>
2238    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2239      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2240      <address><email>henrikn@microsoft.com</email></address>
2241    </author>
2242    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2243      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2244      <address><email>LMM@acm.org</email></address>
2245    </author>
2246    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2247      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2248      <address><email>paulle@microsoft.com</email></address>
2249    </author>
2250    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2251      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2252      <address><email>timbl@w3.org</email></address>
2253    </author>
2254    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2255      <organization abbrev="W3C">World Wide Web Consortium</organization>
2256      <address><email>ylafon@w3.org</email></address>
2257    </author>
2258    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2259      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2260      <address><email>julian.reschke@greenbytes.de</email></address>
2261    </author>
2262    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2263  </front>
2264  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2265  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2266</reference>
2267
2268<reference anchor="Part5">
2269  <front>
2270    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2271    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2272      <organization abbrev="Day Software">Day Software</organization>
2273      <address><email>fielding@gbiv.com</email></address>
2274    </author>
2275    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2276      <organization>One Laptop per Child</organization>
2277      <address><email>jg@laptop.org</email></address>
2278    </author>
2279    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2280      <organization abbrev="HP">Hewlett-Packard Company</organization>
2281      <address><email>JeffMogul@acm.org</email></address>
2282    </author>
2283    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2284      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2285      <address><email>henrikn@microsoft.com</email></address>
2286    </author>
2287    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2288      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2289      <address><email>LMM@acm.org</email></address>
2290    </author>
2291    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2292      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2293      <address><email>paulle@microsoft.com</email></address>
2294    </author>
2295    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2296      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2297      <address><email>timbl@w3.org</email></address>
2298    </author>
2299    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2300      <organization abbrev="W3C">World Wide Web Consortium</organization>
2301      <address><email>ylafon@w3.org</email></address>
2302    </author>
2303    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2304      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2305      <address><email>julian.reschke@greenbytes.de</email></address>
2306    </author>
2307    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2308  </front>
2309  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
2310  <x:source href="p5-range.xml" basename="p5-range"/>
2311</reference>
2312
2313<reference anchor="Part6">
2314  <front>
2315    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2316    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2317      <organization abbrev="Day Software">Day Software</organization>
2318      <address><email>fielding@gbiv.com</email></address>
2319    </author>
2320    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2321      <organization>One Laptop per Child</organization>
2322      <address><email>jg@laptop.org</email></address>
2323    </author>
2324    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2325      <organization abbrev="HP">Hewlett-Packard Company</organization>
2326      <address><email>JeffMogul@acm.org</email></address>
2327    </author>
2328    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2329      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2330      <address><email>henrikn@microsoft.com</email></address>
2331    </author>
2332    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2333      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2334      <address><email>LMM@acm.org</email></address>
2335    </author>
2336    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2337      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2338      <address><email>paulle@microsoft.com</email></address>
2339    </author>
2340    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2341      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2342      <address><email>timbl@w3.org</email></address>
2343    </author>
2344    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2345      <organization abbrev="W3C">World Wide Web Consortium</organization>
2346      <address><email>ylafon@w3.org</email></address>
2347    </author>
2348    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2349      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2350      <address><email>julian.reschke@greenbytes.de</email></address>
2351    </author>
2352    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2353  </front>
2354  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2355  <x:source href="p6-cache.xml" basename="p6-cache"/>
2356</reference>
2357
2358<reference anchor="Part7">
2359  <front>
2360    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2361    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2362      <organization abbrev="Day Software">Day Software</organization>
2363      <address><email>fielding@gbiv.com</email></address>
2364    </author>
2365    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2366      <organization>One Laptop per Child</organization>
2367      <address><email>jg@laptop.org</email></address>
2368    </author>
2369    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2370      <organization abbrev="HP">Hewlett-Packard Company</organization>
2371      <address><email>JeffMogul@acm.org</email></address>
2372    </author>
2373    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2374      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2375      <address><email>henrikn@microsoft.com</email></address>
2376    </author>
2377    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2378      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2379      <address><email>LMM@acm.org</email></address>
2380    </author>
2381    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2382      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2383      <address><email>paulle@microsoft.com</email></address>
2384    </author>
2385    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2386      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2387      <address><email>timbl@w3.org</email></address>
2388    </author>
2389    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2390      <organization abbrev="W3C">World Wide Web Consortium</organization>
2391      <address><email>ylafon@w3.org</email></address>
2392    </author>
2393    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2394      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2395      <address><email>julian.reschke@greenbytes.de</email></address>
2396    </author>
2397    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2398  </front>
2399  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
2400  <x:source href="p7-auth.xml" basename="p7-auth"/>
2401</reference>
2402
2403<reference anchor="RFC2119">
2404  <front>
2405    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2406    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2407      <organization>Harvard University</organization>
2408      <address><email>sob@harvard.edu</email></address>
2409    </author>
2410    <date month="March" year="1997"/>
2411  </front>
2412  <seriesInfo name="BCP" value="14"/>
2413  <seriesInfo name="RFC" value="2119"/>
2414</reference>
2415
2416</references>
2417
2418<references title="Informative References">
2419
2420<reference anchor="Luo1998">
2421  <front>
2422    <title>Tunneling TCP based protocols through Web proxy servers</title>
2423    <author initials="A." surname="Luotonen" fullname="A. Luotonen">
2424      <organization/>
2425    </author>
2426    <date year="1998" month="August"/>
2427  </front>
2428  <seriesInfo name="Internet-Draft" value="draft-luotonen-web-proxy-tunneling-01"/>
2429</reference>
2430
2431<reference anchor="RFC1945">
2432  <front>
2433    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2434    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2435      <organization>MIT, Laboratory for Computer Science</organization>
2436      <address><email>timbl@w3.org</email></address>
2437    </author>
2438    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2439      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2440      <address><email>fielding@ics.uci.edu</email></address>
2441    </author>
2442    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2443      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2444      <address><email>frystyk@w3.org</email></address>
2445    </author>
2446    <date month="May" year="1996"/>
2447  </front>
2448  <seriesInfo name="RFC" value="1945"/>
2449</reference>
2450
2451<reference anchor="RFC2068">
2452  <front>
2453    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2454    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2455      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2456      <address><email>fielding@ics.uci.edu</email></address>
2457    </author>
2458    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2459      <organization>MIT Laboratory for Computer Science</organization>
2460      <address><email>jg@w3.org</email></address>
2461    </author>
2462    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2463      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2464      <address><email>mogul@wrl.dec.com</email></address>
2465    </author>
2466    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2467      <organization>MIT Laboratory for Computer Science</organization>
2468      <address><email>frystyk@w3.org</email></address>
2469    </author>
2470    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2471      <organization>MIT Laboratory for Computer Science</organization>
2472      <address><email>timbl@w3.org</email></address>
2473    </author>
2474    <date month="January" year="1997"/>
2475  </front>
2476  <seriesInfo name="RFC" value="2068"/>
2477</reference>
2478
2479<reference anchor="RFC2616">
2480  <front>
2481    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2482    <author initials="R." surname="Fielding" fullname="R. Fielding">
2483      <organization>University of California, Irvine</organization>
2484      <address><email>fielding@ics.uci.edu</email></address>
2485    </author>
2486    <author initials="J." surname="Gettys" fullname="J. Gettys">
2487      <organization>W3C</organization>
2488      <address><email>jg@w3.org</email></address>
2489    </author>
2490    <author initials="J." surname="Mogul" fullname="J. Mogul">
2491      <organization>Compaq Computer Corporation</organization>
2492      <address><email>mogul@wrl.dec.com</email></address>
2493    </author>
2494    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2495      <organization>MIT Laboratory for Computer Science</organization>
2496      <address><email>frystyk@w3.org</email></address>
2497    </author>
2498    <author initials="L." surname="Masinter" fullname="L. Masinter">
2499      <organization>Xerox Corporation</organization>
2500      <address><email>masinter@parc.xerox.com</email></address>
2501    </author>
2502    <author initials="P." surname="Leach" fullname="P. Leach">
2503      <organization>Microsoft Corporation</organization>
2504      <address><email>paulle@microsoft.com</email></address>
2505    </author>
2506    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2507      <organization>W3C</organization>
2508      <address><email>timbl@w3.org</email></address>
2509    </author>
2510    <date month="June" year="1999"/>
2511  </front>
2512  <seriesInfo name="RFC" value="2616"/>
2513</reference>
2514
2515<reference anchor="RFC2822">
2516  <front>
2517    <title>Internet Message Format</title>
2518    <author initials="P." surname="Resnick" fullname="P. Resnick">
2519      <organization>QUALCOMM Incorporated</organization>
2520    </author>
2521    <date year="2001" month="April"/>
2522  </front> 
2523  <seriesInfo name="RFC" value="2822"/>
2524</reference>
2525
2526</references>
2527
2528<section title="Compatibility with Previous Versions" anchor="compatibility">
2529<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
2530<t>
2531   Clarified which error code should be used for inbound server failures
2532   (e.g. DNS failures). (<xref target="status.504"/>).
2533</t>
2534<t>
2535   201 (Created) had a race that required an Etag be sent when a resource is
2536   first created. (<xref target="status.201"/>).
2537</t>
2538<t>
2539   Rewrite of message transmission requirements to make it much harder
2540   for implementors to get it wrong, as the consequences of errors here
2541   can have significant impact on the Internet, and to deal with the
2542   following problems:
2543  <list style="numbers">
2544      <t>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
2545         this was incorrectly placing a requirement on the behavior of
2546         an implementation of a future version of HTTP/1.x</t>
2547
2548      <t>Made it clear that user-agents should retry requests, not
2549         "clients" in general.</t>
2550
2551      <t>Converted requirements for clients to ignore unexpected 100
2552         (Continue) responses, and for proxies to forward 100 responses,
2553         into a general requirement for 1xx responses.</t>
2554
2555      <t>Modified some TCP-specific language, to make it clearer that
2556         non-TCP transports are possible for HTTP.</t>
2557
2558      <t>Require that the origin server &MUST-NOT; wait for the request
2559         body before it sends a required 100 (Continue) response.</t>
2560
2561      <t>Allow, rather than require, a server to omit 100 (Continue) if
2562         it has already seen some of the request body.</t>
2563
2564      <t>Allow servers to defend against denial-of-service attacks and
2565         broken clients.</t>
2566  </list>
2567</t>
2568<t>
2569   This change adds the Expect header and 417 status code.
2570</t>
2571<t>
2572   Clean up confusion between 403 and 404 responses. (Section <xref target="status.403" format="counter"/>,
2573   <xref target="status.404" format="counter"/>, and <xref target="status.410" format="counter"/>)
2574</t>
2575<t>
2576   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
2577   implemented in previous versions of this specification. See <xref target="RFC2068"/>.
2578</t>
2579</section>
2580
2581<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
2582<t>
2583  Clarify definition of POST.
2584  (<xref target="POST"/>)
2585</t>
2586<t>
2587  Failed to consider that there are
2588  many other request methods that are safe to automatically redirect,
2589  and further that the user agent is able to make that determination
2590  based on the request method semantics.
2591  (Sections <xref format="counter" target="status.301"/>,
2592  <xref format="counter" target="status.302"/> and
2593  <xref format="counter" target="status.307"/> )
2594</t>
2595<t>
2596  Correct syntax of Location header to allow fragment,
2597  as referred symbol wasn't what was expected, and add some
2598  clarifications as to when it would not be appropriate.
2599  (<xref target="header.location"/>)
2600</t>
2601<t>
2602  In the description of the Server header, the Via field
2603  was described as a SHOULD. The requirement was and is stated
2604  correctly in the description of the Via header in &header-via;.
2605  (<xref target="header.server"/>)
2606</t>
2607</section>
2608
2609</section>
2610
2611<section title="Change Log (to be removed by RFC Editor before publication)">
2612
2613<section title="Since RFC2616">
2614<t>
2615  Extracted relevant partitions from <xref target="RFC2616"/>.
2616</t>
2617</section>
2618
2619<section title="Since draft-ietf-httpbis-p2-semantics-00">
2620<t>
2621  Closed issues:
2622  <list style="symbols"> 
2623    <t>
2624      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
2625      "Via is a MUST"
2626      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
2627    </t>
2628    <t>
2629      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
2630      "Fragments allowed in Location"
2631      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
2632    </t>
2633    <t>
2634      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
2635      "Safe Methods vs Redirection"
2636      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
2637    </t>
2638    <t>
2639      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
2640      "Revise description of the POST method"
2641      (<eref target="http://purl.org/NET/http-errata#post"/>)
2642    </t>
2643    <t>
2644      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
2645      "Normative and Informative references"
2646    </t>
2647    <t>
2648      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
2649      "RFC2606 Compliance"
2650    </t>
2651    <t>
2652      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
2653      "Informative references"
2654    </t>
2655    <t>
2656      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
2657      "Redundant cross-references"
2658    </t>
2659  </list>
2660</t>
2661<t>
2662  Other changes:
2663  <list style="symbols"> 
2664    <t>
2665      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
2666    </t>
2667  </list>
2668</t>
2669</section>
2670
2671<section title="Since draft-ietf-httpbis-p2-semantics-01">
2672<t>
2673  Closed issues:
2674  <list style="symbols"> 
2675    <t>
2676      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
2677      "PUT side effects"
2678    </t>
2679    <t>
2680      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
2681      "Duplicate Host header requirements"
2682    </t>
2683  </list>
2684</t>
2685<t>
2686  Ongoing work on ABNF conversion (<eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
2687  <list style="symbols"> 
2688    <t>
2689      Move "Product Tokens" section (back) into Part 1, as "token" is used
2690      in the definition of the Upgrade header.
2691    </t>
2692    <t>
2693      Add explicit references to BNF syntax and rules imported from other parts of the specification.
2694    </t>
2695  </list>
2696</t>
2697</section>
2698
2699</section>
2700
2701</back>
2702</rfc>
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