source: draft-ietf-httpbis/latest/p2-semantics.xml @ 284

Last change on this file since 284 was 284, checked in by julian.reschke@…, 12 years ago

remove misplaced tag

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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 "July">
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  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='#internet.media.type.message.http' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
64]>
65<?rfc toc="yes" ?>
66<?rfc symrefs="yes" ?>
67<?rfc sortrefs="yes" ?>
68<?rfc compact="yes"?>
69<?rfc subcompact="no" ?>
70<?rfc linkmailto="no" ?>
71<?rfc editing="no" ?>
72<?rfc comments="yes"?>
73<?rfc inline="yes"?>
74<?rfc-ext allow-markup-in-artwork="yes" ?>
75<?rfc-ext include-references-in-index="yes" ?>
76<rfc obsoletes="2616" updates="2817" category="std"
77     ipr="full3978" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
78     xmlns:x='http://purl.org/net/xml2rfc/ext'>
79<front>
80
81  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
82
83  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
84    <organization abbrev="Day Software">Day Software</organization>
85    <address>
86      <postal>
87        <street>23 Corporate Plaza DR, Suite 280</street>
88        <city>Newport Beach</city>
89        <region>CA</region>
90        <code>92660</code>
91        <country>USA</country>
92      </postal>
93      <phone>+1-949-706-5300</phone>
94      <facsimile>+1-949-706-5305</facsimile>
95      <email>fielding@gbiv.com</email>
96      <uri>http://roy.gbiv.com/</uri>
97    </address>
98  </author>
99
100  <author initials="J." surname="Gettys" fullname="Jim Gettys">
101    <organization>One Laptop per Child</organization>
102    <address>
103      <postal>
104        <street>21 Oak Knoll Road</street>
105        <city>Carlisle</city>
106        <region>MA</region>
107        <code>01741</code>
108        <country>USA</country>
109      </postal>
110      <email>jg@laptop.org</email>
111      <uri>http://www.laptop.org/</uri>
112    </address>
113  </author>
114 
115  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
116    <organization abbrev="HP">Hewlett-Packard Company</organization>
117    <address>
118      <postal>
119        <street>HP Labs, Large Scale Systems Group</street>
120        <street>1501 Page Mill Road, MS 1177</street>
121        <city>Palo Alto</city>
122        <region>CA</region>
123        <code>94304</code>
124        <country>USA</country>
125      </postal>
126      <email>JeffMogul@acm.org</email>
127    </address>
128  </author>
129
130  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
131    <organization abbrev="Microsoft">Microsoft Corporation</organization>
132    <address>
133      <postal>
134        <street>1 Microsoft Way</street>
135        <city>Redmond</city>
136        <region>WA</region>
137        <code>98052</code>
138        <country>USA</country>
139      </postal>
140      <email>henrikn@microsoft.com</email>
141    </address>
142  </author>
143
144  <author initials="L." surname="Masinter" fullname="Larry Masinter">
145    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
146    <address>
147      <postal>
148        <street>345 Park Ave</street>
149        <city>San Jose</city>
150        <region>CA</region>
151        <code>95110</code>
152        <country>USA</country>
153      </postal>
154      <email>LMM@acm.org</email>
155      <uri>http://larry.masinter.net/</uri>
156    </address>
157  </author>
158 
159  <author initials="P." surname="Leach" fullname="Paul J. Leach">
160    <organization abbrev="Microsoft">Microsoft Corporation</organization>
161    <address>
162      <postal>
163        <street>1 Microsoft Way</street>
164        <city>Redmond</city>
165        <region>WA</region>
166        <code>98052</code>
167      </postal>
168      <email>paulle@microsoft.com</email>
169    </address>
170  </author>
171   
172  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
173    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
174    <address>
175      <postal>
176        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
177        <street>The Stata Center, Building 32</street>
178        <street>32 Vassar Street</street>
179        <city>Cambridge</city>
180        <region>MA</region>
181        <code>02139</code>
182        <country>USA</country>
183      </postal>
184      <email>timbl@w3.org</email>
185      <uri>http://www.w3.org/People/Berners-Lee/</uri>
186    </address>
187  </author>
188
189  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
190    <organization abbrev="W3C">World Wide Web Consortium</organization>
191    <address>
192      <postal>
193        <street>W3C / ERCIM</street>
194        <street>2004, rte des Lucioles</street>
195        <city>Sophia-Antipolis</city>
196        <region>AM</region>
197        <code>06902</code>
198        <country>France</country>
199      </postal>
200      <email>ylafon@w3.org</email>
201      <uri>http://www.raubacapeu.net/people/yves/</uri>
202    </address>
203  </author>
204
205  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
206    <organization abbrev="greenbytes">greenbytes GmbH</organization>
207    <address>
208      <postal>
209        <street>Hafenweg 16</street>
210        <city>Muenster</city><region>NW</region><code>48155</code>
211        <country>Germany</country>
212      </postal>
213      <phone>+49 251 2807760</phone>   
214      <facsimile>+49 251 2807761</facsimile>   
215      <email>julian.reschke@greenbytes.de</email>       
216      <uri>http://greenbytes.de/tech/webdav/</uri>     
217    </address>
218  </author>
219
220  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
221
222<abstract>
223<t>
224   The Hypertext Transfer Protocol (HTTP) is an application-level
225   protocol for distributed, collaborative, hypermedia information
226   systems. HTTP has been in use by the World Wide Web global information
227   initiative since 1990. This document is Part 2 of the seven-part specification
228   that defines the protocol referred to as "HTTP/1.1" and, taken together,
229   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
230   as expressed by request methods, request-header fields, response status codes,
231   and response-header fields.
232</t>
233</abstract>
234
235<note title="Editorial Note (To be removed by RFC Editor)">
236  <t>
237    Discussion of this draft should take place on the HTTPBIS working group
238    mailing list (ietf-http-wg@w3.org). The current issues list is
239    at <eref target="http://www.tools.ietf.org/wg/httpbis/trac/report/11"/>
240    and related documents (including fancy diffs) can be found at
241    <eref target="http://www.tools.ietf.org/wg/httpbis/"/>.
242  </t>
243  <t>
244    The changes in this draft are summarized in <xref target="changes.since.02"/>.
245  </t>
246</note>
247</front>
248<middle>
249<section title="Introduction" anchor="introduction">
250<t>
251   This document defines HTTP/1.1 request and response semantics.  Each HTTP
252   message, as defined in &messaging;, is in the form of either a request or
253   a response.  An HTTP server listens on a connection for HTTP requests and
254   responds to each request, in the order received on that connection, with
255   one or more HTTP response messages.  This document defines the commonly
256   agreed upon semantics of the HTTP uniform interface, the intentions defined
257   by each request method, and the various response messages that might be
258   expected as a result of applying that method for the requested resource.
259</t>
260<t>
261   This document is currently disorganized in order to minimize the changes
262   between drafts and enable reviewers to see the smaller errata changes.
263   The next draft will reorganize the sections to better reflect the content.
264   In particular, the sections will be ordered according to the typical
265   processing of an HTTP request message (after message parsing): resource
266   mapping, general header fields, methods, request modifiers, response
267   status, and resource metadata.  The current mess reflects how widely
268   dispersed these topics and associated requirements had become in
269   <xref target="RFC2616"/>.
270</t>
271
272<section title="Requirements" anchor="intro.requirements">
273<t>
274   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
275   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
276   document are to be interpreted as described in <xref target="RFC2119"/>.
277</t>
278<t>
279   An implementation is not compliant if it fails to satisfy one or more
280   of the &MUST; or &REQUIRED; level requirements for the protocols it
281   implements. An implementation that satisfies all the &MUST; or &REQUIRED;
282   level and all the &SHOULD; level requirements for its protocols is said
283   to be "unconditionally compliant"; one that satisfies all the &MUST;
284   level requirements but not all the &SHOULD; level requirements for its
285   protocols is said to be "conditionally compliant."
286</t>
287</section>
288</section>
289
290<section title="Notational Conventions and Generic Grammar" anchor="notation">
291  <x:anchor-alias value="comment"/>
292  <x:anchor-alias value="DIGIT"/>
293  <x:anchor-alias value="quoted-string"/>
294  <x:anchor-alias value="token"/>
295<t>
296  This specification uses the ABNF syntax defined in &notation-abnf; and
297  the core rules defined in &basic-rules;:
298  <cref anchor="abnf.dep">ABNF syntax and basic rules will be adopted from RFC 5234, see
299  <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>.</cref>
300</t>
301<figure><artwork type="abnf2616">
302  <x:ref>DIGIT</x:ref>         = &lt;DIGIT, defined in &basic-rules;&gt;
303</artwork></figure>
304<figure><artwork type="abnf2616">
305  <x:ref>comment</x:ref>       = &lt;comment, defined in &basic-rules;&gt;
306  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
307  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
308</artwork></figure>
309<t anchor="abnf.dependencies">
310  <x:anchor-alias value="absoluteURI"/>
311  <x:anchor-alias value="Accept"/>
312  <x:anchor-alias value="Accept-Charset"/>
313  <x:anchor-alias value="Accept-Encoding"/>
314  <x:anchor-alias value="Accept-Language"/>
315  <x:anchor-alias value="Accept-Ranges"/>
316  <x:anchor-alias value="Age"/>
317  <x:anchor-alias value="Authorization"/>
318  <x:anchor-alias value="ETag"/>
319  <x:anchor-alias value="fragment"/>
320  <x:anchor-alias value="Host"/>
321  <x:anchor-alias value="HTTP-date"/>
322  <x:anchor-alias value="If-Match"/>
323  <x:anchor-alias value="If-Modified-Since"/>
324  <x:anchor-alias value="If-None-Match"/>
325  <x:anchor-alias value="If-Range"/>
326  <x:anchor-alias value="If-Unmodified-Since"/>
327  <x:anchor-alias value="product"/>
328  <x:anchor-alias value="Proxy-Authenticate"/>
329  <x:anchor-alias value="Proxy-Authorization"/>
330  <x:anchor-alias value="Range"/>
331  <x:anchor-alias value="relativeURI"/>
332  <x:anchor-alias value="TE"/>
333  <x:anchor-alias value="Vary"/>
334  <x:anchor-alias value="WWW-Authenticate"/>
335  The ABNF rules below are defined in other parts:
336</t>
337<figure><!--Part1--><artwork type="abnf2616">
338  <x:ref>absoluteURI</x:ref>   = &lt;absoluteURI, defined in &general-syntax;&gt;
339  <x:ref>fragment</x:ref>      = &lt;fragment, defined in &general-syntax;&gt;
340  <x:ref>Host</x:ref>          = &lt;Host, defined in &header-host;&gt;
341  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
342  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
343  <x:ref>relativeURI</x:ref>   = &lt;relativeURI, defined in &general-syntax;&gt;
344  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
345</artwork></figure>
346<figure><!--Part3--><artwork type="abnf2616">
347  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
348  <x:ref>Accept-Charset</x:ref> =
349             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
350  <x:ref>Accept-Encoding</x:ref> =
351             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
352  <x:ref>Accept-Language</x:ref> =
353             &lt;Accept-Language, defined in &header-accept-language;&gt;
354</artwork></figure>
355<figure><!--Part4--><artwork type="abnf2616">
356  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
357  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
358  <x:ref>If-Modified-Since</x:ref> =
359             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
360  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
361  <x:ref>If-Unmodified-Since</x:ref> =
362             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
363</artwork></figure>
364<figure><!--Part5--><artwork type="abnf2616">
365  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
366  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
367  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
368</artwork></figure>
369<figure><!--Part6--><artwork type="abnf2616">
370  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
371  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
372</artwork><!--Part7--></figure>
373<figure><artwork type="abnf2616">
374  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
375  <x:ref>Proxy-Authenticate</x:ref> =
376             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
377  <x:ref>Proxy-Authorization</x:ref> =
378             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
379  <x:ref>WWW-Authenticate</x:ref> =
380             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
381</artwork></figure>
382</section>
383
384<section title="Method" anchor="method">
385  <x:anchor-alias value="Method"/>
386  <x:anchor-alias value="extension-method"/>
387<t>
388   The Method  token indicates the method to be performed on the
389   resource identified by the Request-URI. The method is case-sensitive.
390</t>
391<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
392  <x:ref>Method</x:ref>         = <x:abnf-char-sequence>"OPTIONS"</x:abnf-char-sequence>   ; "OPTIONS", <xref target="OPTIONS"/>
393                 | <x:abnf-char-sequence>"GET"</x:abnf-char-sequence>               ; "GET", <xref target="GET"/>
394                 | <x:abnf-char-sequence>"HEAD"</x:abnf-char-sequence>            ; "HEAD", <xref target="HEAD"/>
395                 | <x:abnf-char-sequence>"POST"</x:abnf-char-sequence>            ; "POST", <xref target="POST"/>
396                 | <x:abnf-char-sequence>"PUT"</x:abnf-char-sequence>               ; "PUT", <xref target="PUT"/>
397                 | <x:abnf-char-sequence>"DELETE"</x:abnf-char-sequence>      ; "DELETE", <xref target="DELETE"/>
398                 | <x:abnf-char-sequence>"TRACE"</x:abnf-char-sequence>         ; "TRACE", <xref target="TRACE"/>
399                 | <x:abnf-char-sequence>"CONNECT"</x:abnf-char-sequence>   ; "CONNECT", <xref target="CONNECT"/>
400                 | <x:ref>extension-method</x:ref>
401  <x:ref>extension-method</x:ref> = <x:ref>token</x:ref>
402</artwork></figure>
403<t>
404   The list of methods allowed by a resource can be specified in an
405   Allow header field (<xref target="header.allow"/>). The return code of the response
406   always notifies the client whether a method is currently allowed on a
407   resource, since the set of allowed methods can change dynamically. An
408   origin server &SHOULD; return the status code 405 (Method Not Allowed)
409   if the method is known by the origin server but not allowed for the
410   requested resource, and 501 (Not Implemented) if the method is
411   unrecognized or not implemented by the origin server. The methods GET
412   and HEAD &MUST; be supported by all general-purpose servers. All other
413   methods are &OPTIONAL;; however, if the above methods are implemented,
414   they &MUST; be implemented with the same semantics as those specified
415   in <xref target="method.definitions"/>.
416</t>
417
418<section title="Method Registry" anchor="method.registry">
419<t>
420  The HTTP Method Registry defines the name space for the Method token in the
421  Request line of an HTTP request.
422</t>
423<t>
424  Values to be added to this name space are subject to IETF review
425  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
426  new method names should be traceable through statuses of either 'Obsoletes'
427  or 'Updates' to this document.
428</t>
429<t>
430  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
431</t>
432</section>
433</section>
434
435<section title="Request Header Fields" anchor="request.header.fields">
436  <x:anchor-alias value="extension-code"/>
437  <x:anchor-alias value="request-header"/>
438<t>
439   The request-header fields allow the client to pass additional
440   information about the request, and about the client itself, to the
441   server. These fields act as request modifiers, with semantics
442   equivalent to the parameters on a programming language method
443   invocation.
444</t>
445<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
446  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
447                 | <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
448                 | <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
449                 | <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
450                 | <x:ref>Authorization</x:ref>            ; &header-authorization;
451                 | <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
452                 | <x:ref>From</x:ref>                     ; <xref target="header.from"/>
453                 | <x:ref>Host</x:ref>                     ; &header-host;
454                 | <x:ref>If-Match</x:ref>                 ; &header-if-match;
455                 | <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
456                 | <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
457                 | <x:ref>If-Range</x:ref>                 ; &header-if-range;
458                 | <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
459                 | <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
460                 | <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
461                 | <x:ref>Range</x:ref>                    ; &header-range;
462                 | <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
463                 | <x:ref>TE</x:ref>                       ; &header-te;
464                 | <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
465</artwork></figure>
466<t>
467   Request-header field names can be extended reliably only in
468   combination with a change in the protocol version. However, new or
469   experimental header fields &MAY; be given the semantics of request-header
470   fields if all parties in the communication recognize them to
471   be request-header fields. Unrecognized header fields are treated as
472   entity-header fields.
473</t>
474</section>
475
476<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
477  <x:anchor-alias value="Reason-Phrase"/>
478  <x:anchor-alias value="Status-Code"/>
479<t>
480   The Status-Code element is a 3-digit integer result code of the
481   attempt to understand and satisfy the request. The status codes listed
482   below are defined in <xref target="status.codes"/>.
483   The Reason-Phrase is intended to give a short
484   textual description of the Status-Code. The Status-Code is intended
485   for use by automata and the Reason-Phrase is intended for the human
486   user. The client is not required to examine or display the Reason-Phrase.
487</t>
488<t> 
489   The individual values of the numeric status codes defined for
490   HTTP/1.1, and an example set of corresponding Reason-Phrase's, are
491   presented below. The reason phrases listed here are only
492   recommendations -- they &MAY; be replaced by local equivalents without
493   affecting the protocol.
494</t>
495<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"/>
496  <x:ref>Status-Code</x:ref>    =
497         "100"  ; <xref target="status.100"/>: Continue
498       | "101"  ; <xref target="status.101"/>: Switching Protocols
499       | "200"  ; <xref target="status.200"/>: OK
500       | "201"  ; <xref target="status.201"/>: Created
501       | "202"  ; <xref target="status.202"/>: Accepted
502       | "203"  ; <xref target="status.203"/>: Non-Authoritative Information
503       | "204"  ; <xref target="status.204"/>: No Content
504       | "205"  ; <xref target="status.205"/>: Reset Content
505       | "206"  ; <xref target="status.206"/>: Partial Content
506       | "300"  ; <xref target="status.300"/>: Multiple Choices
507       | "301"  ; <xref target="status.301"/>: Moved Permanently
508       | "302"  ; <xref target="status.302"/>: Found
509       | "303"  ; <xref target="status.303"/>: See Other
510       | "304"  ; <xref target="status.304"/>: Not Modified
511       | "305"  ; <xref target="status.305"/>: Use Proxy
512       | "307"  ; <xref target="status.307"/>: Temporary Redirect
513       | "400"  ; <xref target="status.400"/>: Bad Request
514       | "401"  ; <xref target="status.401"/>: Unauthorized
515       | "402"  ; <xref target="status.402"/>: Payment Required
516       | "403"  ; <xref target="status.403"/>: Forbidden
517       | "404"  ; <xref target="status.404"/>: Not Found
518       | "405"  ; <xref target="status.405"/>: Method Not Allowed
519       | "406"  ; <xref target="status.406"/>: Not Acceptable
520       | "407"  ; <xref target="status.407"/>: Proxy Authentication Required
521       | "408"  ; <xref target="status.408"/>: Request Time-out
522       | "409"  ; <xref target="status.409"/>: Conflict
523       | "410"  ; <xref target="status.410"/>: Gone
524       | "411"  ; <xref target="status.411"/>: Length Required
525       | "412"  ; <xref target="status.412"/>: Precondition Failed
526       | "413"  ; <xref target="status.413"/>: Request Entity Too Large
527       | "414"  ; <xref target="status.414"/>: Request-URI Too Large
528       | "415"  ; <xref target="status.415"/>: Unsupported Media Type
529       | "416"  ; <xref target="status.416"/>: Requested range not satisfiable
530       | "417"  ; <xref target="status.417"/>: Expectation Failed
531       | "500"  ; <xref target="status.500"/>: Internal Server Error
532       | "501"  ; <xref target="status.501"/>: Not Implemented
533       | "502"  ; <xref target="status.502"/>: Bad Gateway
534       | "503"  ; <xref target="status.503"/>: Service Unavailable
535       | "504"  ; <xref target="status.504"/>: Gateway Time-out
536       | "505"  ; <xref target="status.505"/>: HTTP Version not supported
537       | <x:ref>extension-code</x:ref>
538
539  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
540  <x:ref>Reason-Phrase</x:ref>  = *&lt;<x:ref>TEXT</x:ref>, excluding <x:ref>CR</x:ref>, <x:ref>LF</x:ref>&gt;
541</artwork></figure>
542<t>
543   HTTP status codes are extensible. HTTP applications are not required
544   to understand the meaning of all registered status codes, though such
545   understanding is obviously desirable. However, applications &MUST;
546   understand the class of any status code, as indicated by the first
547   digit, and treat any unrecognized response as being equivalent to the
548   x00 status code of that class, with the exception that an
549   unrecognized response &MUST-NOT; be cached. For example, if an
550   unrecognized status code of 431 is received by the client, it can
551   safely assume that there was something wrong with its request and
552   treat the response as if it had received a 400 status code. In such
553   cases, user agents &SHOULD; present to the user the entity returned
554   with the response, since that entity is likely to include human-readable
555   information which will explain the unusual status.
556</t>
557
558<section title="Status Code Registry" anchor="status.code.registry">
559<t>
560  The HTTP Status Code Registry defines the name space for the Status-Code
561  token in the Status line of an HTTP response.
562</t>
563<t>
564  Values to be added to this name space are subject to IETF review
565  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
566  new status codes should be traceable through statuses of either 'Obsoletes'
567  or 'Updates' to this document.
568</t>
569<t>
570  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
571</t>
572</section>
573
574</section>
575
576<section title="Response Header Fields" anchor="response.header.fields">
577  <x:anchor-alias value="response-header"/>
578<t>
579   The response-header fields allow the server to pass additional
580   information about the response which cannot be placed in the Status-Line.
581   These header fields give information about the server and about
582   further access to the resource identified by the Request-URI.
583</t>
584<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
585  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
586                  | <x:ref>Age</x:ref>                     ; &header-age;
587                  | <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
588                  | <x:ref>ETag</x:ref>                    ; &header-etag;
589                  | <x:ref>Location</x:ref>                ; <xref target="header.location"/>
590                  | <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
591                  | <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
592                  | <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
593                  | <x:ref>Vary</x:ref>                    ; &header-vary;
594                  | <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
595</artwork></figure>
596<t>
597   Response-header field names can be extended reliably only in
598   combination with a change in the protocol version. However, new or
599   experimental header fields &MAY; be given the semantics of response-header
600   fields if all parties in the communication recognize them to
601   be response-header fields. Unrecognized header fields are treated as
602   entity-header fields.
603</t>
604</section>
605
606<section title="Entity" anchor="entity">
607<t>
608   Request and Response messages &MAY; transfer an entity if not otherwise
609   restricted by the request method or response status code. An entity
610   consists of entity-header fields and an entity-body, although some
611   responses will only include the entity-headers. HTTP entity-body and
612   entity-header fields are defined in &payload;.
613</t>
614<t>
615   An entity-body is only present in a message when a message-body is
616   present, as described in &message-body;. The entity-body is obtained
617   from the message-body by decoding any Transfer-Encoding that might
618   have been applied to ensure safe and proper transfer of the message.
619</t>
620</section>
621
622
623<section title="Method Definitions" anchor="method.definitions">
624<t>
625   The set of common methods for HTTP/1.1 is defined below. Although
626   this set can be expanded, additional methods cannot be assumed to
627   share the same semantics for separately extended clients and servers.
628</t>
629
630<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
631
632<section title="Safe Methods" anchor="safe.methods">
633<t>
634   Implementors should be aware that the software represents the user in
635   their interactions over the Internet, and should be careful to allow
636   the user to be aware of any actions they might take which may have an
637   unexpected significance to themselves or others.
638</t>
639<t>
640   In particular, the convention has been established that the GET and
641   HEAD methods &SHOULD-NOT;  have the significance of taking an action
642   other than retrieval. These methods ought to be considered "safe".
643   This allows user agents to represent other methods, such as POST, PUT
644   and DELETE, in a special way, so that the user is made aware of the
645   fact that a possibly unsafe action is being requested.
646</t>
647<t>
648   Naturally, it is not possible to ensure that the server does not
649   generate side-effects as a result of performing a GET request; in
650   fact, some dynamic resources consider that a feature. The important
651   distinction here is that the user did not request the side-effects,
652   so therefore cannot be held accountable for them.
653</t>
654</section>
655
656<section title="Idempotent Methods" anchor="idempotent.methods">
657<t>
658   Methods can also have the property of "idempotence" in that (aside
659   from error or expiration issues) the side-effects of N &gt; 0 identical
660   requests is the same as for a single request. The methods GET, HEAD,
661   PUT and DELETE share this property. Also, the methods OPTIONS and
662   TRACE &SHOULD-NOT;  have side effects, and so are inherently idempotent.
663</t>
664<t>
665   However, it is possible that a sequence of several requests is non-idempotent,
666   even if all of the methods executed in that sequence are
667   idempotent. (A sequence is idempotent if a single execution of the
668   entire sequence always yields a result that is not changed by a
669   reexecution of all, or part, of that sequence.) For example, a
670   sequence is non-idempotent if its result depends on a value that is
671   later modified in the same sequence.
672</t>
673<t>
674   A sequence that never has side effects is idempotent, by definition
675   (provided that no concurrent operations are being executed on the
676   same set of resources).
677</t>
678</section>
679</section>
680
681<section title="OPTIONS" anchor="OPTIONS">
682  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
683  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
684<t>
685   The OPTIONS method represents a request for information about the
686   communication options available on the request/response chain
687   identified by the Request-URI. This method allows the client to
688   determine the options and/or requirements associated with a resource,
689   or the capabilities of a server, without implying a resource action
690   or initiating a resource retrieval.
691</t>
692<t>
693   Responses to this method are not cacheable.
694</t>
695<t>
696   If the OPTIONS request includes an entity-body (as indicated by the
697   presence of Content-Length or Transfer-Encoding), then the media type
698   &MUST; be indicated by a Content-Type field. Although this
699   specification does not define any use for such a body, future
700   extensions to HTTP might use the OPTIONS body to make more detailed
701   queries on the server.
702</t>
703<t>
704   If the Request-URI is an asterisk ("*"), the OPTIONS request is
705   intended to apply to the server in general rather than to a specific
706   resource. Since a server's communication options typically depend on
707   the resource, the "*" request is only useful as a "ping" or "no-op"
708   type of method; it does nothing beyond allowing the client to test
709   the capabilities of the server. For example, this can be used to test
710   a proxy for HTTP/1.1 compliance (or lack thereof).
711</t>
712<t>
713   If the Request-URI is not an asterisk, the OPTIONS request applies
714   only to the options that are available when communicating with that
715   resource.
716</t>
717<t>
718   A 200 response &SHOULD; include any header fields that indicate
719   optional features implemented by the server and applicable to that
720   resource (e.g., Allow), possibly including extensions not defined by
721   this specification. The response body, if any, &SHOULD; also include
722   information about the communication options. The format for such a
723   body is not defined by this specification, but might be defined by
724   future extensions to HTTP. Content negotiation &MAY; be used to select
725   the appropriate response format. If no response body is included, the
726   response &MUST; include a Content-Length field with a field-value of
727   "0".
728</t>
729<t>
730   The Max-Forwards request-header field &MAY; be used to target a
731   specific proxy in the request chain. When a proxy receives an OPTIONS
732   request on an absoluteURI for which request forwarding is permitted,
733   the proxy &MUST; check for a Max-Forwards field. If the Max-Forwards
734   field-value is zero ("0"), the proxy &MUST-NOT; forward the message;
735   instead, the proxy &SHOULD; respond with its own communication options.
736   If the Max-Forwards field-value is an integer greater than zero, the
737   proxy &MUST; decrement the field-value when it forwards the request. If
738   no Max-Forwards field is present in the request, then the forwarded
739   request &MUST-NOT; include a Max-Forwards field.
740</t>
741</section>
742
743<section title="GET" anchor="GET">
744  <iref primary="true" item="GET method" x:for-anchor=""/>
745  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
746<t>
747   The GET method means retrieve whatever information (in the form of an
748   entity) is identified by the Request-URI. If the Request-URI refers
749   to a data-producing process, it is the produced data which shall be
750   returned as the entity in the response and not the source text of the
751   process, unless that text happens to be the output of the process.
752</t>
753<t>
754   The semantics of the GET method change to a "conditional GET" if the
755   request message includes an If-Modified-Since, If-Unmodified-Since,
756   If-Match, If-None-Match, or If-Range header field. A conditional GET
757   method requests that the entity be transferred only under the
758   circumstances described by the conditional header field(s). The
759   conditional GET method is intended to reduce unnecessary network
760   usage by allowing cached entities to be refreshed without requiring
761   multiple requests or transferring data already held by the client.
762</t>
763<t>
764   The semantics of the GET method change to a "partial GET" if the
765   request message includes a Range header field. A partial GET requests
766   that only part of the entity be transferred, as described in &header-range;.
767   The partial GET method is intended to reduce unnecessary
768   network usage by allowing partially-retrieved entities to be
769   completed without transferring data already held by the client.
770</t>
771<t>
772   The response to a GET request is cacheable if and only if it meets
773   the requirements for HTTP caching described in &caching;.
774</t>
775<t>
776   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
777</t>
778</section>
779
780<section title="HEAD" anchor="HEAD">
781  <iref primary="true" item="HEAD method" x:for-anchor=""/>
782  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
783<t>
784   The HEAD method is identical to GET except that the server &MUST-NOT;
785   return a message-body in the response. The metainformation contained
786   in the HTTP headers in response to a HEAD request &SHOULD; be identical
787   to the information sent in response to a GET request. This method can
788   be used for obtaining metainformation about the entity implied by the
789   request without transferring the entity-body itself. This method is
790   often used for testing hypertext links for validity, accessibility,
791   and recent modification.
792</t>
793<t>
794   The response to a HEAD request &MAY; be cacheable in the sense that the
795   information contained in the response &MAY; be used to update a
796   previously cached entity from that resource. If the new field values
797   indicate that the cached entity differs from the current entity (as
798   would be indicated by a change in Content-Length, Content-MD5, ETag
799   or Last-Modified), then the cache &MUST; treat the cache entry as
800   stale.
801</t>
802</section>
803
804<section title="POST" anchor="POST">
805  <iref primary="true" item="POST method" x:for-anchor=""/>
806  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
807<t>
808   The POST method is used to request that the origin server accept the
809   entity enclosed in the request as data to be processed by the resource
810   identified by the Request-URI in the Request-Line. POST is designed
811   to allow a uniform method to cover the following functions:
812  <list style="symbols">
813    <t>
814      Annotation of existing resources;
815    </t>
816    <t>
817        Posting a message to a bulletin board, newsgroup, mailing list,
818        or similar group of articles;
819    </t>
820    <t>
821        Providing a block of data, such as the result of submitting a
822        form, to a data-handling process;
823    </t>
824    <t>
825        Extending a database through an append operation.
826    </t>
827  </list>
828</t>
829<t>
830   The actual function performed by the POST method is determined by the
831   server and is usually dependent on the Request-URI.
832</t>
833<t>
834   The action performed by the POST method might not result in a
835   resource that can be identified by a URI. In this case, either 200
836   (OK) or 204 (No Content) is the appropriate response status,
837   depending on whether or not the response includes an entity that
838   describes the result.
839</t>
840<t>
841   If a resource has been created on the origin server, the response
842   &SHOULD; be 201 (Created) and contain an entity which describes the
843   status of the request and refers to the new resource, and a Location
844   header (see <xref target="header.location"/>).
845</t>
846<t>
847   Responses to this method are not cacheable, unless the response
848   includes appropriate Cache-Control or Expires header fields. However,
849   the 303 (See Other) response can be used to direct the user agent to
850   retrieve a cacheable resource.
851</t>
852</section>
853
854<section title="PUT" anchor="PUT">
855  <iref primary="true" item="PUT method" x:for-anchor=""/>
856  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
857<t>
858   The PUT method requests that the enclosed entity be stored at the
859   supplied Request-URI. If the Request-URI refers to an already
860   existing resource, the enclosed entity &SHOULD; be considered as a
861   modified version of the one residing on the origin server. If the
862   Request-URI does not point to an existing resource, and that URI is
863   capable of being defined as a new resource by the requesting user
864   agent, the origin server can create the resource with that URI. If a
865   new resource is created at the Request-URI, the origin server &MUST;
866         inform the user agent
867   via the 201 (Created) response. If an existing resource is modified,
868   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
869   to indicate successful completion of the request. If the resource
870   could not be created or modified with the Request-URI, an appropriate
871   error response &SHOULD; be given that reflects the nature of the
872   problem. The recipient of the entity &MUST-NOT; ignore any Content-*
873   (e.g. Content-Range) headers that it does not understand or implement
874   and &MUST; return a 501 (Not Implemented) response in such cases.
875</t>
876<t>
877   If the request passes through a cache and the Request-URI identifies
878   one or more currently cached entities, those entries &SHOULD; be
879   treated as stale. Responses to this method are not cacheable.
880</t>
881<t>
882   The fundamental difference between the POST and PUT requests is
883   reflected in the different meaning of the Request-URI. The URI in a
884   POST request identifies the resource that will handle the enclosed
885   entity. That resource might be a data-accepting process, a gateway to
886   some other protocol, or a separate entity that accepts annotations.
887   In contrast, the URI in a PUT request identifies the entity enclosed
888   with the request -- the user agent knows what URI is intended and the
889   server &MUST-NOT; attempt to apply the request to some other resource.
890   If the server desires that the request be applied to a different URI,
891   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
892   then make its own decision regarding whether or not to redirect the
893   request.
894</t>
895<t>
896   A single resource &MAY; be identified by many different URIs. For
897   example, an article might have a URI for identifying "the current
898   version" which is separate from the URI identifying each particular
899   version. In this case, a PUT request on a general URI might result in
900   several other URIs being defined by the origin server.
901</t>
902<t>
903   HTTP/1.1 does not define how a PUT method affects the state of an
904   origin server.
905</t>
906<t>
907   Unless otherwise specified for a particular entity-header, the
908   entity-headers in the PUT request &SHOULD; be applied to the resource
909   created or modified by the PUT.
910</t>
911</section>
912
913<section title="DELETE" anchor="DELETE">
914  <iref primary="true" item="DELETE method" x:for-anchor=""/>
915  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
916<t>
917   The DELETE method requests that the origin server delete the resource
918   identified by the Request-URI. This method &MAY; be overridden by human
919   intervention (or other means) on the origin server. The client cannot
920   be guaranteed that the operation has been carried out, even if the
921   status code returned from the origin server indicates that the action
922   has been completed successfully. However, the server &SHOULD-NOT; 
923   indicate success unless, at the time the response is given, it
924   intends to delete the resource or move it to an inaccessible
925   location.
926</t>
927<t>
928   A successful response &SHOULD; be 200 (OK) if the response includes an
929   entity describing the status, 202 (Accepted) if the action has not
930   yet been enacted, or 204 (No Content) if the action has been enacted
931   but the response does not include an entity.
932</t>
933<t>
934   If the request passes through a cache and the Request-URI identifies
935   one or more currently cached entities, those entries &SHOULD; be
936   treated as stale. Responses to this method are not cacheable.
937</t>
938</section>
939
940<section title="TRACE" anchor="TRACE">
941  <iref primary="true" item="TRACE method" x:for-anchor=""/>
942  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
943<t>
944   The TRACE method is used to invoke a remote, application-layer loop-back
945   of the request message. The final recipient of the request
946   &SHOULD; reflect the message received back to the client as the
947   entity-body of a 200 (OK) response. The final recipient is either the
948   origin server or the first proxy or gateway to receive a Max-Forwards
949   value of zero (0) in the request (see <xref target="header.max-forwards"/>). A TRACE request
950   &MUST-NOT; include an entity.
951</t>
952<t>
953   TRACE allows the client to see what is being received at the other
954   end of the request chain and use that data for testing or diagnostic
955   information. The value of the Via header field (&header-via;) is of
956   particular interest, since it acts as a trace of the request chain.
957   Use of the Max-Forwards header field allows the client to limit the
958   length of the request chain, which is useful for testing a chain of
959   proxies forwarding messages in an infinite loop.
960</t>
961<t>
962   If the request is valid, the response &SHOULD; contain the entire
963   request message in the entity-body, with a Content-Type of
964   "message/http" (see &media-type-message-http;). Responses to this method
965   &MUST-NOT; be cached.
966</t>
967</section>
968
969<section title="CONNECT" anchor="CONNECT">
970  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
971  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
972<t>
973   This specification reserves the method name CONNECT for use with a
974   proxy that can dynamically switch to being a tunnel (e.g. SSL
975   tunneling <xref target="RFC2817"/>).
976</t>
977</section>
978</section>
979
980
981<section title="Status Code Definitions" anchor="status.codes">
982<t>
983   Each Status-Code is described below, including a description of which
984   method(s) it can follow and any metainformation required in the
985   response.
986</t>
987
988<section title="Informational 1xx" anchor="status.1xx">
989<t>
990   This class of status code indicates a provisional response,
991   consisting only of the Status-Line and optional headers, and is
992   terminated by an empty line. There are no required headers for this
993   class of status code. Since HTTP/1.0 did not define any 1xx status
994   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
995   except under experimental conditions.
996</t>
997<t>
998   A client &MUST; be prepared to accept one or more 1xx status responses
999   prior to a regular response, even if the client does not expect a 100
1000   (Continue) status message. Unexpected 1xx status responses &MAY; be
1001   ignored by a user agent.
1002</t>
1003<t>
1004   Proxies &MUST; forward 1xx responses, unless the connection between the
1005   proxy and its client has been closed, or unless the proxy itself
1006   requested the generation of the 1xx response. (For example, if a
1007   proxy adds a "Expect: 100-continue" field when it forwards a request,
1008   then it need not forward the corresponding 100 (Continue)
1009   response(s).)
1010</t>
1011
1012<section title="100 Continue" anchor="status.100">
1013  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1014  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1015<t>
1016   The client &SHOULD; continue with its request. This interim response is
1017   used to inform the client that the initial part of the request has
1018   been received and has not yet been rejected by the server. The client
1019   &SHOULD; continue by sending the remainder of the request or, if the
1020   request has already been completed, ignore this response. The server
1021   &MUST; send a final response after the request has been completed. See
1022   &use100; for detailed discussion of the use and handling of this
1023   status code.
1024</t>
1025</section>
1026
1027<section title="101 Switching Protocols" anchor="status.101">
1028  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1029  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1030<t>
1031   The server understands and is willing to comply with the client's
1032   request, via the Upgrade message header field (&header-upgrade;), for a
1033   change in the application protocol being used on this connection. The
1034   server will switch protocols to those defined by the response's
1035   Upgrade header field immediately after the empty line which
1036   terminates the 101 response.
1037</t>
1038<t>
1039   The protocol &SHOULD; be switched only when it is advantageous to do
1040   so. For example, switching to a newer version of HTTP is advantageous
1041   over older versions, and switching to a real-time, synchronous
1042   protocol might be advantageous when delivering resources that use
1043   such features.
1044</t>
1045</section>
1046</section>
1047
1048<section title="Successful 2xx" anchor="status.2xx">
1049<t>
1050   This class of status code indicates that the client's request was
1051   successfully received, understood, and accepted.
1052</t>
1053
1054<section title="200 OK" anchor="status.200">
1055  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1056  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1057<t>
1058   The request has succeeded. The information returned with the response
1059   is dependent on the method used in the request, for example:
1060  <list style="hanging">
1061    <t hangText="GET">
1062          an entity corresponding to the requested resource is sent in
1063          the response;
1064    </t>
1065    <t hangText="HEAD">
1066          the entity-header fields corresponding to the requested
1067          resource are sent in the response without any message-body;
1068    </t>
1069    <t hangText="POST">
1070      an entity describing or containing the result of the action;
1071    </t>
1072    <t hangText="TRACE">
1073      an entity containing the request message as received by the
1074      end server.
1075    </t>
1076  </list>
1077</t>
1078</section>
1079
1080<section title="201 Created" anchor="status.201">
1081  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1082  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1083<t>
1084   The request has been fulfilled and resulted in a new resource being
1085   created. The newly created resource can be referenced by the URI(s)
1086   returned in the entity of the response, with the most specific URI
1087   for the resource given by a Location header field. The response
1088   &SHOULD; include an entity containing a list of resource
1089   characteristics and location(s) from which the user or user agent can
1090   choose the one most appropriate. The entity format is specified by
1091   the media type given in the Content-Type header field. The origin
1092   server &MUST; create the resource before returning the 201 status code.
1093   If the action cannot be carried out immediately, the server &SHOULD;
1094   respond with 202 (Accepted) response instead.
1095</t>
1096<t>
1097   A 201 response &MAY; contain an ETag response header field indicating
1098   the current value of the entity tag for the requested variant just
1099   created, see &header-etag;.
1100</t>
1101</section>
1102
1103<section title="202 Accepted" anchor="status.202">
1104  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1105  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1106<t>
1107   The request has been accepted for processing, but the processing has
1108   not been completed.  The request might or might not eventually be
1109   acted upon, as it might be disallowed when processing actually takes
1110   place. There is no facility for re-sending a status code from an
1111   asynchronous operation such as this.
1112</t>
1113<t>
1114   The 202 response is intentionally non-committal. Its purpose is to
1115   allow a server to accept a request for some other process (perhaps a
1116   batch-oriented process that is only run once per day) without
1117   requiring that the user agent's connection to the server persist
1118   until the process is completed. The entity returned with this
1119   response &SHOULD; include an indication of the request's current status
1120   and either a pointer to a status monitor or some estimate of when the
1121   user can expect the request to be fulfilled.
1122</t>
1123</section>
1124
1125<section title="203 Non-Authoritative Information" anchor="status.203">
1126  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1127  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1128<t>
1129   The returned metainformation in the entity-header is not the
1130   definitive set as available from the origin server, but is gathered
1131   from a local or a third-party copy. The set presented &MAY; be a subset
1132   or superset of the original version. For example, including local
1133   annotation information about the resource might result in a superset
1134   of the metainformation known by the origin server. Use of this
1135   response code is not required and is only appropriate when the
1136   response would otherwise be 200 (OK).
1137</t>
1138</section>
1139
1140<section title="204 No Content" anchor="status.204">
1141  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1142  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1143<t>
1144   The server has fulfilled the request but does not need to return an
1145   entity-body, and might want to return updated metainformation. The
1146   response &MAY; include new or updated metainformation in the form of
1147   entity-headers, which if present &SHOULD; be associated with the
1148   requested variant.
1149</t>
1150<t>
1151   If the client is a user agent, it &SHOULD-NOT;  change its document view
1152   from that which caused the request to be sent. This response is
1153   primarily intended to allow input for actions to take place without
1154   causing a change to the user agent's active document view, although
1155   any new or updated metainformation &SHOULD; be applied to the document
1156   currently in the user agent's active view.
1157</t>
1158<t>
1159   The 204 response &MUST-NOT; include a message-body, and thus is always
1160   terminated by the first empty line after the header fields.
1161</t>
1162</section>
1163
1164<section title="205 Reset Content" anchor="status.205">
1165  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1166  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1167<t>
1168   The server has fulfilled the request and the user agent &SHOULD; reset
1169   the document view which caused the request to be sent. This response
1170   is primarily intended to allow input for actions to take place via
1171   user input, followed by a clearing of the form in which the input is
1172   given so that the user can easily initiate another input action. The
1173   response &MUST-NOT; include an entity.
1174</t>
1175</section>
1176
1177<section title="206 Partial Content" anchor="status.206">
1178  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1179  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1180<t>
1181   The server has fulfilled the partial GET request for the resource
1182   and the enclosed entity is a partial representation as defined in &range;.
1183</t>
1184</section>
1185</section>
1186
1187<section title="Redirection 3xx" anchor="status.3xx">
1188<t>
1189   This class of status code indicates that further action needs to be
1190   taken by the user agent in order to fulfill the request.  The action
1191   required &MAY; be carried out by the user agent without interaction
1192   with the user if and only if the method used in the second request is
1193   GET or HEAD. A client &SHOULD; detect infinite redirection loops, since
1194   such loops generate network traffic for each redirection.
1195  <list><t>
1196      <x:h>Note:</x:h> previous versions of this specification recommended a
1197      maximum of five redirections. Content developers should be aware
1198      that there might be clients that implement such a fixed
1199      limitation.
1200  </t></list>
1201</t>
1202
1203<section title="300 Multiple Choices" anchor="status.300">
1204  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1205  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1206<t>
1207   The requested resource corresponds to any one of a set of
1208   representations, each with its own specific location, and agent-driven
1209   negotiation information (&content-negotiation;) is being provided so that
1210   the user (or user agent) can select a preferred representation and
1211   redirect its request to that location.
1212</t>
1213<t>
1214   Unless it was a HEAD request, the response &SHOULD; include an entity
1215   containing a list of resource characteristics and location(s) from
1216   which the user or user agent can choose the one most appropriate. The
1217   entity format is specified by the media type given in the Content-Type
1218   header field. Depending upon the format and the capabilities of
1219   the user agent, selection of the most appropriate choice &MAY; be
1220   performed automatically. However, this specification does not define
1221   any standard for such automatic selection.
1222</t>
1223<t>
1224   If the server has a preferred choice of representation, it &SHOULD;
1225   include the specific URI for that representation in the Location
1226   field; user agents &MAY; use the Location field value for automatic
1227   redirection. This response is cacheable unless indicated otherwise.
1228</t>
1229</section>
1230
1231<section title="301 Moved Permanently" anchor="status.301">
1232  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1233  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1234<t>
1235   The requested resource has been assigned a new permanent URI and any
1236   future references to this resource &SHOULD; use one of the returned
1237   URIs.  Clients with link editing capabilities ought to automatically
1238   re-link references to the Request-URI to one or more of the new
1239   references returned by the server, where possible. This response is
1240   cacheable unless indicated otherwise.
1241</t>
1242<t>
1243   The new permanent URI &SHOULD; be given by the Location field in the
1244   response. Unless the request method was HEAD, the entity of the
1245   response &SHOULD; contain a short hypertext note with a hyperlink to
1246   the new URI(s).
1247</t>
1248<t>
1249   If the 301 status code is received in response to a request method
1250   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1251   then the request &MAY; be automatically redirected by the user agent without
1252   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1253   request unless it can be confirmed by the user, since this might
1254   change the conditions under which the request was issued.
1255  <list><t>
1256      <x:h>Note:</x:h> When automatically redirecting a POST request after
1257      receiving a 301 status code, some existing HTTP/1.0 user agents
1258      will erroneously change it into a GET request.
1259  </t></list>
1260</t>
1261</section>
1262
1263<section title="302 Found" anchor="status.302">
1264  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1265  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1266<t>
1267   The requested resource resides temporarily under a different URI.
1268   Since the redirection might be altered on occasion, the client &SHOULD;
1269   continue to use the Request-URI for future requests.  This response
1270   is only cacheable if indicated by a Cache-Control or Expires header
1271   field.
1272</t>
1273<t>
1274   The temporary URI &SHOULD; be given by the Location field in the
1275   response. Unless the request method was HEAD, the entity of the
1276   response &SHOULD; contain a short hypertext note with a hyperlink to
1277   the new URI(s).
1278</t>
1279<t>
1280   If the 302 status code is received in response to a request method
1281   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1282   then the request &MAY; be automatically redirected by the user agent without
1283   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1284   request unless it can be confirmed by the user, since this might
1285   change the conditions under which the request was issued.
1286  <list><t>
1287      <x:h>Note:</x:h> <xref target="RFC1945"/> and <xref target="RFC2068"/> specify that the client is not allowed
1288      to change the method on the redirected request.  However, most
1289      existing user agent implementations treat 302 as if it were a 303
1290      response, performing a GET on the Location field-value regardless
1291      of the original request method. The status codes 303 and 307 have
1292      been added for servers that wish to make unambiguously clear which
1293      kind of reaction is expected of the client.
1294  </t></list>
1295</t>
1296</section>
1297
1298<section title="303 See Other" anchor="status.303">
1299  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1300  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1301<t>
1302   The server directs the user agent to a different resource, indicated
1303   by a URI in the Location header field, that provides an indirect
1304   response to the original request.  The user agent &MAY; perform a GET
1305   request on the URI in the Location field in order to obtain a
1306   representation corresponding to the response, be redirected again,
1307   or end with an error status.  The Location URI is not a substitute
1308   reference for the originally requested resource.
1309</t>
1310<t>
1311   The 303 status is generally applicable to any HTTP method.  It is
1312   primarily used to allow the output of a POST action to redirect
1313   the user agent to a selected resource, since doing so provides the
1314   information corresponding to the POST response in a form that
1315   can be separately identified, bookmarked, and cached independent
1316   of the original request.
1317</t>
1318<t>
1319   A 303 response to a GET request indicates that the requested
1320   resource does not have a representation of its own that can be
1321   transferred by the server over HTTP.  The Location URI indicates a
1322   resource that is descriptive of the requested resource such that
1323   the follow-on representation may be useful without implying that
1324   it adequately represents the previously requested resource.
1325   Note that answers to the questions of what can be represented, what
1326   representations are adequate, and what might be a useful description
1327   are outside the scope of HTTP and thus entirely determined by the
1328   resource owner(s).
1329</t>
1330<t>
1331   A 303 response &SHOULD-NOT; be cached unless it is indicated as
1332   cacheable by Cache-Control or Expires header fields.  Except for
1333   responses to a HEAD request, the entity of a 303 response &SHOULD;
1334   contain a short hypertext note with a hyperlink to the Location URI.
1335</t>
1336</section>
1337
1338<section title="304 Not Modified" anchor="status.304">
1339  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1340  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1341<t>
1342   The response to the request has not been modified since the conditions
1343   indicated by the client's conditional GET request, as defined in &conditional;.
1344</t>
1345</section>
1346
1347<section title="305 Use Proxy" anchor="status.305">
1348  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1349  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1350<t>
1351   The 305 status was defined in a previous version of this specification
1352   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1353</t>
1354</section>
1355
1356<section title="306 (Unused)" anchor="status.306">
1357  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1358  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1359<t>
1360   The 306 status code was used in a previous version of the
1361   specification, is no longer used, and the code is reserved.
1362</t>
1363</section>
1364
1365<section title="307 Temporary Redirect" anchor="status.307">
1366  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1367  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1368<t>
1369   The requested resource resides temporarily under a different URI.
1370   Since the redirection &MAY; be altered on occasion, the client &SHOULD;
1371   continue to use the Request-URI for future requests.  This response
1372   is only cacheable if indicated by a Cache-Control or Expires header
1373   field.
1374</t>
1375<t>
1376   The temporary URI &SHOULD; be given by the Location field in the
1377   response. Unless the request method was HEAD, the entity of the
1378   response &SHOULD; contain a short hypertext note with a hyperlink to
1379   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1380   understand the 307 status. Therefore, the note &SHOULD; contain the
1381   information necessary for a user to repeat the original request on
1382   the new URI.
1383</t>
1384<t>
1385   If the 307 status code is received in response to a request method
1386   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1387   then the request &MAY; be automatically redirected by the user agent without
1388   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1389   request unless it can be confirmed by the user, since this might
1390   change the conditions under which the request was issued.
1391</t>
1392</section>
1393</section>
1394
1395<section title="Client Error 4xx" anchor="status.4xx">
1396<t>
1397   The 4xx class of status code is intended for cases in which the
1398   client seems to have erred. Except when responding to a HEAD request,
1399   the server &SHOULD; include an entity containing an explanation of the
1400   error situation, and whether it is a temporary or permanent
1401   condition. These status codes are applicable to any request method.
1402   User agents &SHOULD; display any included entity to the user.
1403</t>
1404<t>
1405   If the client is sending data, a server implementation using TCP
1406   &SHOULD; be careful to ensure that the client acknowledges receipt of
1407   the packet(s) containing the response, before the server closes the
1408   input connection. If the client continues sending data to the server
1409   after the close, the server's TCP stack will send a reset packet to
1410   the client, which may erase the client's unacknowledged input buffers
1411   before they can be read and interpreted by the HTTP application.
1412</t>
1413
1414<section title="400 Bad Request" anchor="status.400">
1415  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1416  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1417<t>
1418   The request could not be understood by the server due to malformed
1419   syntax. The client &SHOULD-NOT;  repeat the request without
1420   modifications.
1421</t>
1422</section>
1423
1424<section title="401 Unauthorized" anchor="status.401">
1425  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1426  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1427<t>
1428   The request requires user authentication (see &auth;).
1429</t>
1430</section>
1431
1432<section title="402 Payment Required" anchor="status.402">
1433  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1434  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1435<t>
1436   This code is reserved for future use.
1437</t>
1438</section>
1439
1440<section title="403 Forbidden" anchor="status.403">
1441  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1442  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1443<t>
1444   The server understood the request, but is refusing to fulfill it.
1445   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1446   If the request method was not HEAD and the server wishes to make
1447   public why the request has not been fulfilled, it &SHOULD; describe the
1448   reason for the refusal in the entity.  If the server does not wish to
1449   make this information available to the client, the status code 404
1450   (Not Found) can be used instead.
1451</t>
1452</section>
1453
1454<section title="404 Not Found" anchor="status.404">
1455  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1456  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1457<t>
1458   The server has not found anything matching the Request-URI. No
1459   indication is given of whether the condition is temporary or
1460   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1461   knows, through some internally configurable mechanism, that an old
1462   resource is permanently unavailable and has no forwarding address.
1463   This status code is commonly used when the server does not wish to
1464   reveal exactly why the request has been refused, or when no other
1465   response is applicable.
1466</t>
1467</section>
1468
1469<section title="405 Method Not Allowed" anchor="status.405">
1470  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1471  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1472<t>
1473   The method specified in the Request-Line is not allowed for the
1474   resource identified by the Request-URI. The response &MUST; include an
1475   Allow header containing a list of valid methods for the requested
1476   resource.
1477</t>
1478</section>
1479
1480<section title="406 Not Acceptable" anchor="status.406">
1481  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1482  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1483<t>
1484   The resource identified by the request is only capable of generating
1485   response entities which have content characteristics not acceptable
1486   according to the accept headers sent in the request.
1487</t>
1488<t>
1489   Unless it was a HEAD request, the response &SHOULD; include an entity
1490   containing a list of available entity characteristics and location(s)
1491   from which the user or user agent can choose the one most
1492   appropriate. The entity format is specified by the media type given
1493   in the Content-Type header field. Depending upon the format and the
1494   capabilities of the user agent, selection of the most appropriate
1495   choice &MAY; be performed automatically. However, this specification
1496   does not define any standard for such automatic selection.
1497  <list><t>
1498      <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1499      not acceptable according to the accept headers sent in the
1500      request. In some cases, this may even be preferable to sending a
1501      406 response. User agents are encouraged to inspect the headers of
1502      an incoming response to determine if it is acceptable.
1503  </t></list>
1504</t>
1505<t>
1506   If the response could be unacceptable, a user agent &SHOULD;
1507   temporarily stop receipt of more data and query the user for a
1508   decision on further actions.
1509</t>
1510</section>
1511
1512<section title="407 Proxy Authentication Required" anchor="status.407">
1513  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1514  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1515<t>
1516   This code is similar to 401 (Unauthorized), but indicates that the
1517   client must first authenticate itself with the proxy (see &auth;).
1518</t>
1519</section>
1520
1521<section title="408 Request Timeout" anchor="status.408">
1522  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1523  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1524<t>
1525   The client did not produce a request within the time that the server
1526   was prepared to wait. The client &MAY; repeat the request without
1527   modifications at any later time.
1528</t>
1529</section>
1530
1531<section title="409 Conflict" anchor="status.409">
1532  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1533  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1534<t>
1535   The request could not be completed due to a conflict with the current
1536   state of the resource. This code is only allowed in situations where
1537   it is expected that the user might be able to resolve the conflict
1538   and resubmit the request. The response body &SHOULD; include enough
1539   information for the user to recognize the source of the conflict.
1540   Ideally, the response entity would include enough information for the
1541   user or user agent to fix the problem; however, that might not be
1542   possible and is not required.
1543</t>
1544<t>
1545   Conflicts are most likely to occur in response to a PUT request. For
1546   example, if versioning were being used and the entity being PUT
1547   included changes to a resource which conflict with those made by an
1548   earlier (third-party) request, the server might use the 409 response
1549   to indicate that it can't complete the request. In this case, the
1550   response entity would likely contain a list of the differences
1551   between the two versions in a format defined by the response
1552   Content-Type.
1553</t>
1554</section>
1555
1556<section title="410 Gone" anchor="status.410">
1557  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1558  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1559<t>
1560   The requested resource is no longer available at the server and no
1561   forwarding address is known. This condition is expected to be
1562   considered permanent. Clients with link editing capabilities &SHOULD;
1563   delete references to the Request-URI after user approval. If the
1564   server does not know, or has no facility to determine, whether or not
1565   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1566   used instead. This response is cacheable unless indicated otherwise.
1567</t>
1568<t>
1569   The 410 response is primarily intended to assist the task of web
1570   maintenance by notifying the recipient that the resource is
1571   intentionally unavailable and that the server owners desire that
1572   remote links to that resource be removed. Such an event is common for
1573   limited-time, promotional services and for resources belonging to
1574   individuals no longer working at the server's site. It is not
1575   necessary to mark all permanently unavailable resources as "gone" or
1576   to keep the mark for any length of time -- that is left to the
1577   discretion of the server owner.
1578</t>
1579</section>
1580
1581<section title="411 Length Required" anchor="status.411">
1582  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1583  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1584<t>
1585   The server refuses to accept the request without a defined Content-Length.
1586   The client &MAY; repeat the request if it adds a valid
1587   Content-Length header field containing the length of the message-body
1588   in the request message.
1589</t>
1590</section>
1591
1592<section title="412 Precondition Failed" anchor="status.412">
1593  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1594  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1595<t>
1596   The precondition given in one or more of the request-header fields
1597   evaluated to false when it was tested on the server, as defined in
1598   &conditional;.
1599</t>
1600</section>
1601
1602<section title="413 Request Entity Too Large" anchor="status.413">
1603  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1604  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1605<t>
1606   The server is refusing to process a request because the request
1607   entity is larger than the server is willing or able to process. The
1608   server &MAY; close the connection to prevent the client from continuing
1609   the request.
1610</t>
1611<t>
1612   If the condition is temporary, the server &SHOULD; include a Retry-After
1613   header field to indicate that it is temporary and after what
1614   time the client &MAY; try again.
1615</t>
1616</section>
1617
1618<section title="414 Request-URI Too Long" anchor="status.414">
1619  <iref primary="true" item="414 Request-URI Too Long (status code)" x:for-anchor=""/>
1620  <iref primary="true" item="Status Codes" subitem="414 Request-URI Too Long" x:for-anchor=""/>
1621<t>
1622   The server is refusing to service the request because the Request-URI
1623   is longer than the server is willing to interpret. This rare
1624   condition is only likely to occur when a client has improperly
1625   converted a POST request to a GET request with long query
1626   information, when the client has descended into a URI "black hole" of
1627   redirection (e.g., a redirected URI prefix that points to a suffix of
1628   itself), or when the server is under attack by a client attempting to
1629   exploit security holes present in some servers using fixed-length
1630   buffers for reading or manipulating the Request-URI.
1631</t>
1632</section>
1633
1634<section title="415 Unsupported Media Type" anchor="status.415">
1635  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1636  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1637<t>
1638   The server is refusing to service the request because the entity of
1639   the request is in a format not supported by the requested resource
1640   for the requested method.
1641</t>
1642</section>
1643
1644<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1645  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1646  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1647<t>
1648   The request included a Range request-header field (&header-range;) and none of
1649   the range-specifier values in this field overlap the current extent
1650   of the selected resource.
1651</t>
1652</section>
1653
1654<section title="417 Expectation Failed" anchor="status.417">
1655  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1656  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1657<t>
1658   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1659   could not be met by this server, or, if the server is a proxy,
1660   the server has unambiguous evidence that the request could not be met
1661   by the next-hop server.
1662</t>
1663</section>
1664</section>
1665
1666<section title="Server Error 5xx" anchor="status.5xx">
1667<t>
1668   Response status codes beginning with the digit "5" indicate cases in
1669   which the server is aware that it has erred or is incapable of
1670   performing the request. Except when responding to a HEAD request, the
1671   server &SHOULD; include an entity containing an explanation of the
1672   error situation, and whether it is a temporary or permanent
1673   condition. User agents &SHOULD; display any included entity to the
1674   user. These response codes are applicable to any request method.
1675</t>
1676
1677<section title="500 Internal Server Error" anchor="status.500">
1678  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1679  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1680<t>
1681   The server encountered an unexpected condition which prevented it
1682   from fulfilling the request.
1683</t>
1684</section>
1685
1686<section title="501 Not Implemented" anchor="status.501">
1687  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1688  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1689<t>
1690   The server does not support the functionality required to fulfill the
1691   request. This is the appropriate response when the server does not
1692   recognize the request method and is not capable of supporting it for
1693   any resource.
1694</t>
1695</section>
1696
1697<section title="502 Bad Gateway" anchor="status.502">
1698  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1699  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1700<t>
1701   The server, while acting as a gateway or proxy, received an invalid
1702   response from the upstream server it accessed in attempting to
1703   fulfill the request.
1704</t>
1705</section>
1706
1707<section title="503 Service Unavailable" anchor="status.503">
1708  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1709  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1710<t>
1711   The server is currently unable to handle the request due to a
1712   temporary overloading or maintenance of the server. The implication
1713   is that this is a temporary condition which will be alleviated after
1714   some delay. If known, the length of the delay &MAY; be indicated in a
1715   Retry-After header. If no Retry-After is given, the client &SHOULD;
1716   handle the response as it would for a 500 response.
1717  <list><t>
1718      <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1719      server must use it when becoming overloaded. Some servers may wish
1720      to simply refuse the connection.
1721  </t></list>
1722</t>
1723</section>
1724
1725<section title="504 Gateway Timeout" anchor="status.504">
1726  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1727  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1728<t>
1729   The server, while acting as a gateway or proxy, did not receive a
1730   timely response from the upstream server specified by the URI (e.g.
1731   HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed
1732   to access in attempting to complete the request.
1733  <list><t>
1734      <x:h>Note:</x:h> Note to implementors: some deployed proxies are known to
1735      return 400 or 500 when DNS lookups time out.
1736  </t></list>
1737</t>
1738</section>
1739
1740<section title="505 HTTP Version Not Supported" anchor="status.505">
1741  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1742  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
1743<t>
1744   The server does not support, or refuses to support, the protocol
1745   version that was used in the request message. The server is
1746   indicating that it is unable or unwilling to complete the request
1747   using the same major version as the client, as described in &http-version;,
1748   other than with this error message. The response &SHOULD; contain
1749   an entity describing why that version is not supported and what other
1750   protocols are supported by that server.
1751</t>
1752
1753</section>
1754</section>
1755</section>
1756
1757
1758<section title="Header Field Definitions" anchor="header.fields">
1759<t>
1760   This section defines the syntax and semantics of HTTP/1.1 header fields
1761   related to request and response semantics.
1762</t>
1763<t>
1764   For entity-header fields, both sender and recipient refer to either the
1765   client or the server, depending on who sends and who receives the entity.
1766</t>
1767
1768<section title="Allow" anchor="header.allow">
1769  <iref primary="true" item="Allow header" x:for-anchor=""/>
1770  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
1771  <x:anchor-alias value="Allow"/>
1772<t>
1773      The Allow response-header field lists the set of methods advertised as
1774      supported by the resource identified by the Request-URI. The purpose of
1775      this field is strictly to inform the recipient of valid methods
1776      associated with the resource. An Allow header field &MUST; be
1777      present in a 405 (Method Not Allowed) response.
1778</t>
1779<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/>
1780  <x:ref>Allow</x:ref>   = "Allow" ":" #<x:ref>Method</x:ref>
1781</artwork></figure>
1782<t>
1783      Example of use:
1784</t>
1785<figure><artwork type="example">
1786       Allow: GET, HEAD, PUT
1787</artwork></figure>
1788<t>
1789      The actual set of allowed methods is defined
1790      by the origin server at the time of each request.
1791</t>
1792<t>
1793      A proxy &MUST-NOT; modify the Allow header field even if it does not
1794      understand all the methods specified, since the user agent might
1795      have other means of communicating with the origin server.
1796</t>
1797</section>
1798
1799<section title="Expect" anchor="header.expect">
1800  <iref primary="true" item="Expect header" x:for-anchor=""/>
1801  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
1802  <x:anchor-alias value="Expect"/>
1803  <x:anchor-alias value="expectation"/>
1804  <x:anchor-alias value="expectation-extension"/>
1805  <x:anchor-alias value="expect-params"/>
1806<t>
1807   The Expect request-header field is used to indicate that particular
1808   server behaviors are required by the client.
1809</t>
1810<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"/>
1811  <x:ref>Expect</x:ref>       =  "Expect" ":" 1#<x:ref>expectation</x:ref>
1812 
1813  <x:ref>expectation</x:ref>  =  "100-continue" | <x:ref>expectation-extension</x:ref>
1814  <x:ref>expectation-extension</x:ref> =  <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> | <x:ref>quoted-string</x:ref> )
1815                           *<x:ref>expect-params</x:ref> ]
1816  <x:ref>expect-params</x:ref> =  ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> | <x:ref>quoted-string</x:ref> ) ]
1817</artwork></figure>
1818<t>
1819   A server that does not understand or is unable to comply with any of
1820   the expectation values in the Expect field of a request &MUST; respond
1821   with appropriate error status. The server &MUST; respond with a 417
1822   (Expectation Failed) status if any of the expectations cannot be met
1823   or, if there are other problems with the request, some other 4xx
1824   status.
1825</t>
1826<t>
1827   This header field is defined with extensible syntax to allow for
1828   future extensions. If a server receives a request containing an
1829   Expect field that includes an expectation-extension that it does not
1830   support, it &MUST; respond with a 417 (Expectation Failed) status.
1831</t>
1832<t>
1833   Comparison of expectation values is case-insensitive for unquoted
1834   tokens (including the 100-continue token), and is case-sensitive for
1835   quoted-string expectation-extensions.
1836</t>
1837<t>
1838   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
1839   return a 417 (Expectation Failed) status if it receives a request
1840   with an expectation that it cannot meet. However, the Expect
1841   request-header itself is end-to-end; it &MUST; be forwarded if the
1842   request is forwarded.
1843</t>
1844<t>
1845   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1846   Expect header.
1847</t>
1848<t>
1849   See &use100; for the use of the 100 (Continue) status.
1850</t>
1851</section>
1852
1853<section title="From" anchor="header.from">
1854  <iref primary="true" item="From header" x:for-anchor=""/>
1855  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
1856  <x:anchor-alias value="From"/>
1857  <x:anchor-alias value="mailbox"/>
1858<t>
1859   The From request-header field, if given, &SHOULD; contain an Internet
1860   e-mail address for the human user who controls the requesting user
1861   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
1862   in <xref x:sec="3.4" x:fmt="of" target="RFC2822"/>:
1863</t>
1864<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/>
1865  <x:ref>From</x:ref>    = "From" ":" <x:ref>mailbox</x:ref>
1866 
1867  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC2822"/>&gt;
1868</artwork></figure>
1869<t>
1870   An example is:
1871</t>
1872<figure><artwork type="example">
1873    From: webmaster@example.org
1874</artwork></figure>
1875<t>
1876   This header field &MAY; be used for logging purposes and as a means for
1877   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
1878   be used as an insecure form of access protection. The interpretation
1879   of this field is that the request is being performed on behalf of the
1880   person given, who accepts responsibility for the method performed. In
1881   particular, robot agents &SHOULD; include this header so that the
1882   person responsible for running the robot can be contacted if problems
1883   occur on the receiving end.
1884</t>
1885<t>
1886   The Internet e-mail address in this field &MAY; be separate from the
1887   Internet host which issued the request. For example, when a request
1888   is passed through a proxy the original issuer's address &SHOULD; be
1889   used.
1890</t>
1891<t>
1892   The client &SHOULD-NOT;  send the From header field without the user's
1893   approval, as it might conflict with the user's privacy interests or
1894   their site's security policy. It is strongly recommended that the
1895   user be able to disable, enable, and modify the value of this field
1896   at any time prior to a request.
1897</t>
1898</section>
1899
1900<section title="Location" anchor="header.location">
1901  <iref primary="true" item="Location header" x:for-anchor=""/>
1902  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
1903  <x:anchor-alias value="Location"/>
1904<t>
1905   The Location response-header field is used for the identification of a
1906   new resource or to redirect the recipient to a location other than the
1907   Request-URI for completion of the request.  For 201 (Created)
1908   responses, the Location is that of the new resource which was created
1909   by the request. For 3xx responses, the location &SHOULD; indicate the
1910   server's preferred URI for automatic redirection to the resource. The
1911   field value consists of a single absolute URI.
1912</t>
1913<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/>
1914  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>absoluteURI</x:ref> [ "#" <x:ref>fragment</x:ref> ]
1915</artwork></figure>
1916<t>
1917   An example is:
1918</t>
1919<figure><artwork type="example">
1920    Location: http://www.example.org/pub/WWW/People.html
1921</artwork></figure>
1922<t>
1923  <list><t>
1924      <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
1925      from Location in that the Content-Location identifies the original
1926      location of the entity enclosed in the request. It is therefore
1927      possible for a response to contain header fields for both Location
1928      and Content-Location.
1929  </t></list>
1930</t>
1931<t>
1932   There are circumstances in which a fragment identifier in a Location URL would not be appropriate:
1933   <list style="symbols">
1934      <t>With a 201 Created response, because in this usage the Location header specifies the URL for the entire created resource.</t>
1935      <t>With a 300 Multiple Choices, since the choice decision is intended to be made on resource characteristics and not fragment characteristics.</t>
1936      <t>With 305 Use Proxy.</t>
1937   </list>
1938</t>
1939</section>
1940
1941<section title="Max-Forwards" anchor="header.max-forwards">
1942  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
1943  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
1944  <x:anchor-alias value="Max-Forwards"/>
1945<t>
1946   The Max-Forwards request-header field provides a mechanism with the
1947   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>) methods to limit the
1948   number of proxies or gateways that can forward the request to the
1949   next inbound server. This can be useful when the client is attempting
1950   to trace a request chain which appears to be failing or looping in
1951   mid-chain.
1952</t>
1953<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/>
1954  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" 1*<x:ref>DIGIT</x:ref>
1955</artwork></figure>
1956<t>
1957   The Max-Forwards value is a decimal integer indicating the remaining
1958   number of times this request message may be forwarded.
1959</t>
1960<t>
1961   Each proxy or gateway recipient of a TRACE or OPTIONS request
1962   containing a Max-Forwards header field &MUST; check and update its
1963   value prior to forwarding the request. If the received value is zero
1964   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
1965   respond as the final recipient. If the received Max-Forwards value is
1966   greater than zero, then the forwarded message &MUST; contain an updated
1967   Max-Forwards field with a value decremented by one (1).
1968</t>
1969<t>
1970   The Max-Forwards header field &MAY; be ignored for all other methods
1971   defined by this specification and for any extension methods for which
1972   it is not explicitly referred to as part of that method definition.
1973</t>
1974</section>
1975
1976<section title="Referer" anchor="header.referer">
1977  <iref primary="true" item="Referer header" x:for-anchor=""/>
1978  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
1979  <x:anchor-alias value="Referer"/>
1980<t>
1981   The Referer[sic] request-header field allows the client to specify,
1982   for the server's benefit, the address (URI) of the resource from
1983   which the Request-URI was obtained (the "referrer", although the
1984   header field is misspelled.) The Referer request-header allows a
1985   server to generate lists of back-links to resources for interest,
1986   logging, optimized caching, etc. It also allows obsolete or mistyped
1987   links to be traced for maintenance. The Referer field &MUST-NOT; be
1988   sent if the Request-URI was obtained from a source that does not have
1989   its own URI, such as input from the user keyboard.
1990</t>
1991<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/>
1992  <x:ref>Referer</x:ref>        = "Referer" ":" ( <x:ref>absoluteURI</x:ref> | <x:ref>relativeURI</x:ref> )
1993</artwork></figure>
1994<t>
1995   Example:
1996</t>
1997<figure><artwork type="example">
1998    Referer: http://www.example.org/hypertext/Overview.html
1999</artwork></figure>
2000<t>
2001   If the field value is a relative URI, it &SHOULD; be interpreted
2002   relative to the Request-URI. The URI &MUST-NOT; include a fragment. See
2003   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2004</t>
2005</section>
2006
2007<section title="Retry-After" anchor="header.retry-after">
2008  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2009  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
2010  <x:anchor-alias value="Retry-After"/>
2011<t>
2012   The Retry-After response-header field can be used with a 503 (Service
2013   Unavailable) response to indicate how long the service is expected to
2014   be unavailable to the requesting client. This field &MAY; also be used
2015   with any 3xx (Redirection) response to indicate the minimum time the
2016   user-agent is asked wait before issuing the redirected request. The
2017   value of this field can be either an HTTP-date or an integer number
2018   of seconds (in decimal) after the time of the response.
2019</t>
2020<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/>
2021  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" ( <x:ref>HTTP-date</x:ref> | <x:ref>delta-seconds</x:ref> )
2022</artwork></figure>
2023<t anchor="rule.delta-seconds">
2024  <x:anchor-alias value="delta-seconds"/>
2025   Time spans are non-negative decimal integers, representing time in
2026   seconds.
2027</t>
2028<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2029  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2030</artwork></figure>
2031<t>
2032   Two examples of its use are
2033</t>
2034<figure><artwork type="example">
2035    Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2036    Retry-After: 120
2037</artwork></figure>
2038<t>
2039   In the latter example, the delay is 2 minutes.
2040</t>
2041</section>
2042
2043<section title="Server" anchor="header.server">
2044  <iref primary="true" item="Server header" x:for-anchor=""/>
2045  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
2046  <x:anchor-alias value="Server"/>
2047<t>
2048   The Server response-header field contains information about the
2049   software used by the origin server to handle the request. The field
2050   can contain multiple product tokens (&product-tokens;) and comments
2051   identifying the server and any significant subproducts. The product
2052   tokens are listed in order of their significance for identifying the
2053   application.
2054</t>
2055<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/>
2056  <x:ref>Server</x:ref>         = "Server" ":" 1*( <x:ref>product</x:ref> | <x:ref>comment</x:ref> )
2057</artwork></figure>
2058<t>
2059   Example:
2060</t>
2061<figure><artwork type="example">
2062    Server: CERN/3.0 libwww/2.17
2063</artwork></figure>
2064<t>
2065   If the response is being forwarded through a proxy, the proxy
2066   application &MUST-NOT; modify the Server response-header. Instead, it
2067   &MUST; include a Via field (as described in &header-via;).
2068  <list><t>
2069      <x:h>Note:</x:h> Revealing the specific software version of the server might
2070      allow the server machine to become more vulnerable to attacks
2071      against software that is known to contain security holes. Server
2072      implementors are encouraged to make this field a configurable
2073      option.
2074  </t></list>
2075</t>
2076</section>
2077
2078<section title="User-Agent" anchor="header.user-agent">
2079  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2080  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
2081  <x:anchor-alias value="User-Agent"/>
2082<t>
2083   The User-Agent request-header field contains information about the
2084   user agent originating the request. This is for statistical purposes,
2085   the tracing of protocol violations, and automated recognition of user
2086   agents for the sake of tailoring responses to avoid particular user
2087   agent limitations. User agents &SHOULD; include this field with
2088   requests. The field can contain multiple product tokens (&product-tokens;)
2089   and comments identifying the agent and any subproducts which form a
2090   significant part of the user agent. By convention, the product tokens
2091   are listed in order of their significance for identifying the
2092   application.
2093</t>
2094<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/>
2095  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" 1*( <x:ref>product</x:ref> | <x:ref>comment</x:ref> )
2096</artwork></figure>
2097<t>
2098   Example:
2099</t>
2100<figure><artwork type="example">
2101    User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2102</artwork></figure>
2103</section>
2104
2105</section>
2106
2107<section title="IANA Considerations" anchor="IANA.considerations">
2108
2109<section title="Method Registry" anchor="method.registration">
2110<t>
2111  The registration procedure for HTTP Methods is defined by
2112  <xref target="method.registry"/> of this document.
2113</t>
2114<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2115<!--(START)-->
2116<t xmlns:x="http://purl.org/net/xml2rfc/ext">
2117    The HTTP Method Registry located at <eref target="http://www.iana.org/assignments/http-methods"/>
2118    should be populated with the registrations below:
2119  </t>
2120<texttable xmlns:x="http://purl.org/net/xml2rfc/ext" align="left">
2121   <ttcol>Method</ttcol>
2122   <ttcol>Reference</ttcol>
2123
2124   <c>CONNECT</c>
2125   <c>
2126      <xref target="CONNECT"/>
2127   </c>
2128
2129   <c>DELETE</c>
2130   <c>
2131      <xref target="DELETE"/>
2132   </c>
2133
2134   <c>GET</c>
2135   <c>
2136      <xref target="GET"/>
2137   </c>
2138
2139   <c>HEAD</c>
2140   <c>
2141      <xref target="HEAD"/>
2142   </c>
2143
2144   <c>OPTIONS</c>
2145   <c>
2146      <xref target="OPTIONS"/>
2147   </c>
2148
2149   <c>POST</c>
2150   <c>
2151      <xref target="POST"/>
2152   </c>
2153
2154   <c>PUT</c>
2155   <c>
2156      <xref target="PUT"/>
2157   </c>
2158
2159   <c>TRACE</c>
2160   <c>
2161      <xref target="TRACE"/>
2162   </c>
2163</texttable>
2164<!--(END)-->
2165</section>
2166
2167<section title="Status Code Registry" anchor="status.code.registration">
2168<t>
2169  The registration procedure for HTTP Status Codes -- previously defined
2170  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> -- is now defined
2171  by <xref target="status.code.registry"/> of this document.
2172</t>
2173<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2174<!--(START)-->
2175<t xmlns:x="http://purl.org/net/xml2rfc/ext">
2176    The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2177    should be updated with the registrations below:
2178  </t>
2179<texttable xmlns:x="http://purl.org/net/xml2rfc/ext">
2180   <ttcol>Value</ttcol>
2181   <ttcol>Description</ttcol>
2182   <ttcol>Reference</ttcol>
2183
2184   <c>100</c>
2185   <c>Continue</c>
2186   <c>
2187      <xref target="status.100"/>
2188   </c>
2189
2190   <c>101</c>
2191   <c>Switching Protocols</c>
2192   <c>
2193      <xref target="status.101"/>
2194   </c>
2195
2196   <c>200</c>
2197   <c>OK</c>
2198   <c>
2199      <xref target="status.200"/>
2200   </c>
2201
2202   <c>201</c>
2203   <c>Created</c>
2204   <c>
2205      <xref target="status.201"/>
2206   </c>
2207
2208   <c>202</c>
2209   <c>Accepted</c>
2210   <c>
2211      <xref target="status.202"/>
2212   </c>
2213
2214   <c>203</c>
2215   <c>Non-Authoritative Information</c>
2216   <c>
2217      <xref target="status.203"/>
2218   </c>
2219
2220   <c>204</c>
2221   <c>No Content</c>
2222   <c>
2223      <xref target="status.204"/>
2224   </c>
2225
2226   <c>205</c>
2227   <c>Reset Content</c>
2228   <c>
2229      <xref target="status.205"/>
2230   </c>
2231
2232   <c>206</c>
2233   <c>Partial Content</c>
2234   <c>
2235      <xref target="status.206"/>
2236   </c>
2237
2238   <c>300</c>
2239   <c>Multiple Choices</c>
2240   <c>
2241      <xref target="status.300"/>
2242   </c>
2243
2244   <c>301</c>
2245   <c>Moved Permanently</c>
2246   <c>
2247      <xref target="status.301"/>
2248   </c>
2249
2250   <c>302</c>
2251   <c>Found</c>
2252   <c>
2253      <xref target="status.302"/>
2254   </c>
2255
2256   <c>303</c>
2257   <c>See Other</c>
2258   <c>
2259      <xref target="status.303"/>
2260   </c>
2261
2262   <c>304</c>
2263   <c>Not Modified</c>
2264   <c>
2265      <xref target="status.304"/>
2266   </c>
2267
2268   <c>305</c>
2269   <c>Use Proxy</c>
2270   <c>
2271      <xref target="status.305"/>
2272   </c>
2273
2274   <c>306</c>
2275   <c>(Unused)</c>
2276   <c>
2277      <xref target="status.306"/>
2278   </c>
2279
2280   <c>307</c>
2281   <c>Temporary Redirect</c>
2282   <c>
2283      <xref target="status.307"/>
2284   </c>
2285
2286   <c>400</c>
2287   <c>Bad Request</c>
2288   <c>
2289      <xref target="status.400"/>
2290   </c>
2291
2292   <c>401</c>
2293   <c>Unauthorized</c>
2294   <c>
2295      <xref target="status.401"/>
2296   </c>
2297
2298   <c>402</c>
2299   <c>Payment Required</c>
2300   <c>
2301      <xref target="status.402"/>
2302   </c>
2303
2304   <c>403</c>
2305   <c>Forbidden</c>
2306   <c>
2307      <xref target="status.403"/>
2308   </c>
2309
2310   <c>404</c>
2311   <c>Not Found</c>
2312   <c>
2313      <xref target="status.404"/>
2314   </c>
2315
2316   <c>405</c>
2317   <c>Method Not Allowed</c>
2318   <c>
2319      <xref target="status.405"/>
2320   </c>
2321
2322   <c>406</c>
2323   <c>Not Acceptable</c>
2324   <c>
2325      <xref target="status.406"/>
2326   </c>
2327
2328   <c>407</c>
2329   <c>Proxy Authentication Required</c>
2330   <c>
2331      <xref target="status.407"/>
2332   </c>
2333
2334   <c>408</c>
2335   <c>Request Timeout</c>
2336   <c>
2337      <xref target="status.408"/>
2338   </c>
2339
2340   <c>409</c>
2341   <c>Conflict</c>
2342   <c>
2343      <xref target="status.409"/>
2344   </c>
2345
2346   <c>410</c>
2347   <c>Gone</c>
2348   <c>
2349      <xref target="status.410"/>
2350   </c>
2351
2352   <c>411</c>
2353   <c>Length Required</c>
2354   <c>
2355      <xref target="status.411"/>
2356   </c>
2357
2358   <c>412</c>
2359   <c>Precondition Failed</c>
2360   <c>
2361      <xref target="status.412"/>
2362   </c>
2363
2364   <c>413</c>
2365   <c>Request Entity Too Large</c>
2366   <c>
2367      <xref target="status.413"/>
2368   </c>
2369
2370   <c>414</c>
2371   <c>Request-URI Too Long</c>
2372   <c>
2373      <xref target="status.414"/>
2374   </c>
2375
2376   <c>415</c>
2377   <c>Unsupported Media Type</c>
2378   <c>
2379      <xref target="status.415"/>
2380   </c>
2381
2382   <c>416</c>
2383   <c>Requested Range Not Satisfiable</c>
2384   <c>
2385      <xref target="status.416"/>
2386   </c>
2387
2388   <c>417</c>
2389   <c>Expectation Failed</c>
2390   <c>
2391      <xref target="status.417"/>
2392   </c>
2393
2394   <c>500</c>
2395   <c>Internal Server Error</c>
2396   <c>
2397      <xref target="status.500"/>
2398   </c>
2399
2400   <c>501</c>
2401   <c>Not Implemented</c>
2402   <c>
2403      <xref target="status.501"/>
2404   </c>
2405
2406   <c>502</c>
2407   <c>Bad Gateway</c>
2408   <c>
2409      <xref target="status.502"/>
2410   </c>
2411
2412   <c>503</c>
2413   <c>Service Unavailable</c>
2414   <c>
2415      <xref target="status.503"/>
2416   </c>
2417
2418   <c>504</c>
2419   <c>Gateway Timeout</c>
2420   <c>
2421      <xref target="status.504"/>
2422   </c>
2423
2424   <c>505</c>
2425   <c>HTTP Version Not Supported</c>
2426   <c>
2427      <xref target="status.505"/>
2428   </c>
2429</texttable>
2430<!--(END)-->
2431</section>
2432<section title="Message Header Registration" anchor="message.header.registration">
2433<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2434<!--(START)-->
2435<t>
2436    The Message Header Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> should be updated
2437    with the permanent registrations below (see <xref target="RFC3864"/>):
2438  </t>
2439<texttable>
2440   <ttcol>Header Field Name</ttcol>
2441   <ttcol>Protocol</ttcol>
2442   <ttcol>Status</ttcol>
2443   <ttcol>Reference</ttcol>
2444
2445   <c>Allow</c>
2446   <c>http</c>
2447   <c>standard</c>
2448   <c>
2449      <xref target="header.allow"/>
2450   </c>
2451
2452   <c>Expect</c>
2453   <c>http</c>
2454   <c>standard</c>
2455   <c>
2456      <xref target="header.expect"/>
2457   </c>
2458
2459   <c>From</c>
2460   <c>http</c>
2461   <c>standard</c>
2462   <c>
2463      <xref target="header.from"/>
2464   </c>
2465
2466   <c>Location</c>
2467   <c>http</c>
2468   <c>standard</c>
2469   <c>
2470      <xref target="header.location"/>
2471   </c>
2472
2473   <c>Max-Forwards</c>
2474   <c>http</c>
2475   <c>standard</c>
2476   <c>
2477      <xref target="header.max-forwards"/>
2478   </c>
2479
2480   <c>Referer</c>
2481   <c>http</c>
2482   <c>standard</c>
2483   <c>
2484      <xref target="header.referer"/>
2485   </c>
2486
2487   <c>Retry-After</c>
2488   <c>http</c>
2489   <c>standard</c>
2490   <c>
2491      <xref target="header.retry-after"/>
2492   </c>
2493
2494   <c>Server</c>
2495   <c>http</c>
2496   <c>standard</c>
2497   <c>
2498      <xref target="header.server"/>
2499   </c>
2500
2501   <c>User-Agent</c>
2502   <c>http</c>
2503   <c>standard</c>
2504   <c>
2505      <xref target="header.user-agent"/>
2506   </c>
2507</texttable>
2508<t>
2509    The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2510</t>
2511<!--(END)-->
2512</section>
2513</section>
2514
2515<section title="Security Considerations" anchor="security.considerations">
2516<t>
2517   This section is meant to inform application developers, information
2518   providers, and users of the security limitations in HTTP/1.1 as
2519   described by this document. The discussion does not include
2520   definitive solutions to the problems revealed, though it does make
2521   some suggestions for reducing security risks.
2522</t>
2523
2524<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2525<t>
2526   Like any generic data transfer protocol, HTTP cannot regulate the
2527   content of the data that is transferred, nor is there any a priori
2528   method of determining the sensitivity of any particular piece of
2529   information within the context of any given request. Therefore,
2530   applications &SHOULD; supply as much control over this information as
2531   possible to the provider of that information. Four header fields are
2532   worth special mention in this context: Server, Via, Referer and From.
2533</t>
2534<t>
2535   Revealing the specific software version of the server might allow the
2536   server machine to become more vulnerable to attacks against software
2537   that is known to contain security holes. Implementors &SHOULD; make the
2538   Server header field a configurable option.
2539</t>
2540<t>
2541   Proxies which serve as a portal through a network firewall &SHOULD;
2542   take special precautions regarding the transfer of header information
2543   that identifies the hosts behind the firewall. In particular, they
2544   &SHOULD; remove, or replace with sanitized versions, any Via fields
2545   generated behind the firewall.
2546</t>
2547<t>
2548   The Referer header allows reading patterns to be studied and reverse
2549   links drawn. Although it can be very useful, its power can be abused
2550   if user details are not separated from the information contained in
2551   the Referer. Even when the personal information has been removed, the
2552   Referer header might indicate a private document's URI whose
2553   publication would be inappropriate.
2554</t>
2555<t>
2556   The information sent in the From field might conflict with the user's
2557   privacy interests or their site's security policy, and hence it
2558   &SHOULD-NOT;  be transmitted without the user being able to disable,
2559   enable, and modify the contents of the field. The user &MUST; be able
2560   to set the contents of this field within a user preference or
2561   application defaults configuration.
2562</t>
2563<t>
2564   We suggest, though do not require, that a convenient toggle interface
2565   be provided for the user to enable or disable the sending of From and
2566   Referer information.
2567</t>
2568<t>
2569   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2570   fields can sometimes be used to determine that a specific client or
2571   server have a particular security hole which might be exploited.
2572   Unfortunately, this same information is often used for other valuable
2573   purposes for which HTTP currently has no better mechanism.
2574</t>
2575</section>
2576
2577<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2578<t>
2579   Because the source of a link might be private information or might
2580   reveal an otherwise private information source, it is strongly
2581   recommended that the user be able to select whether or not the
2582   Referer field is sent. For example, a browser client could have a
2583   toggle switch for browsing openly/anonymously, which would
2584   respectively enable/disable the sending of Referer and From
2585   information.
2586</t>
2587<t>
2588   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2589   HTTP request if the referring page was transferred with a secure
2590   protocol.
2591</t>
2592<t>
2593   Authors of services should not use
2594   GET-based forms for the submission of sensitive data because that
2595   data will be encoded in the Request-URI. Many existing
2596   servers, proxies, and user agents log or display the Request-URI in
2597   places where it might be visible to third parties. Such services can
2598   use POST-based form submission instead.
2599</t>
2600</section>
2601
2602<section title="Location Headers and Spoofing" anchor="location.spoofing">
2603<t>
2604   If a single server supports multiple organizations that do not trust
2605   one another, then it &MUST; check the values of Location and Content-Location
2606   headers in responses that are generated under control of
2607   said organizations to make sure that they do not attempt to
2608   invalidate resources over which they have no authority.
2609</t>
2610</section>
2611
2612</section>
2613
2614<section title="Acknowledgments" anchor="ack">
2615</section>
2616</middle>
2617<back>
2618
2619<references title="Normative References">
2620
2621<reference anchor="Part1">
2622  <front>
2623    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2624    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2625      <organization abbrev="Day Software">Day Software</organization>
2626      <address><email>fielding@gbiv.com</email></address>
2627    </author>
2628    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2629      <organization>One Laptop per Child</organization>
2630      <address><email>jg@laptop.org</email></address>
2631    </author>
2632    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2633      <organization abbrev="HP">Hewlett-Packard Company</organization>
2634      <address><email>JeffMogul@acm.org</email></address>
2635    </author>
2636    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2637      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2638      <address><email>henrikn@microsoft.com</email></address>
2639    </author>
2640    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2641      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2642      <address><email>LMM@acm.org</email></address>
2643    </author>
2644    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2645      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2646      <address><email>paulle@microsoft.com</email></address>
2647    </author>
2648    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2649      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2650      <address><email>timbl@w3.org</email></address>
2651    </author>
2652    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2653      <organization abbrev="W3C">World Wide Web Consortium</organization>
2654      <address><email>ylafon@w3.org</email></address>
2655    </author>
2656    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2657      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2658      <address><email>julian.reschke@greenbytes.de</email></address>
2659    </author>
2660    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2661  </front>
2662  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2663  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2664</reference>
2665
2666<reference anchor="Part3">
2667  <front>
2668    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2669    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2670      <organization abbrev="Day Software">Day Software</organization>
2671      <address><email>fielding@gbiv.com</email></address>
2672    </author>
2673    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2674      <organization>One Laptop per Child</organization>
2675      <address><email>jg@laptop.org</email></address>
2676    </author>
2677    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2678      <organization abbrev="HP">Hewlett-Packard Company</organization>
2679      <address><email>JeffMogul@acm.org</email></address>
2680    </author>
2681    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2682      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2683      <address><email>henrikn@microsoft.com</email></address>
2684    </author>
2685    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2686      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2687      <address><email>LMM@acm.org</email></address>
2688    </author>
2689    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2690      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2691      <address><email>paulle@microsoft.com</email></address>
2692    </author>
2693    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2694      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2695      <address><email>timbl@w3.org</email></address>
2696    </author>
2697    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2698      <organization abbrev="W3C">World Wide Web Consortium</organization>
2699      <address><email>ylafon@w3.org</email></address>
2700    </author>
2701    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2702      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2703      <address><email>julian.reschke@greenbytes.de</email></address>
2704    </author>
2705    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2706  </front>
2707  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2708  <x:source href="p3-payload.xml" basename="p3-payload"/>
2709</reference>
2710
2711<reference anchor="Part4">
2712  <front>
2713    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2714    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2715      <organization abbrev="Day Software">Day Software</organization>
2716      <address><email>fielding@gbiv.com</email></address>
2717    </author>
2718    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2719      <organization>One Laptop per Child</organization>
2720      <address><email>jg@laptop.org</email></address>
2721    </author>
2722    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2723      <organization abbrev="HP">Hewlett-Packard Company</organization>
2724      <address><email>JeffMogul@acm.org</email></address>
2725    </author>
2726    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2727      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2728      <address><email>henrikn@microsoft.com</email></address>
2729    </author>
2730    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2731      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2732      <address><email>LMM@acm.org</email></address>
2733    </author>
2734    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2735      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2736      <address><email>paulle@microsoft.com</email></address>
2737    </author>
2738    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2739      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2740      <address><email>timbl@w3.org</email></address>
2741    </author>
2742    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2743      <organization abbrev="W3C">World Wide Web Consortium</organization>
2744      <address><email>ylafon@w3.org</email></address>
2745    </author>
2746    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2747      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2748      <address><email>julian.reschke@greenbytes.de</email></address>
2749    </author>
2750    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2751  </front>
2752  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2753  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2754</reference>
2755
2756<reference anchor="Part5">
2757  <front>
2758    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2759    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2760      <organization abbrev="Day Software">Day Software</organization>
2761      <address><email>fielding@gbiv.com</email></address>
2762    </author>
2763    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2764      <organization>One Laptop per Child</organization>
2765      <address><email>jg@laptop.org</email></address>
2766    </author>
2767    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2768      <organization abbrev="HP">Hewlett-Packard Company</organization>
2769      <address><email>JeffMogul@acm.org</email></address>
2770    </author>
2771    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2772      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2773      <address><email>henrikn@microsoft.com</email></address>
2774    </author>
2775    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2776      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2777      <address><email>LMM@acm.org</email></address>
2778    </author>
2779    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2780      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2781      <address><email>paulle@microsoft.com</email></address>
2782    </author>
2783    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2784      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2785      <address><email>timbl@w3.org</email></address>
2786    </author>
2787    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2788      <organization abbrev="W3C">World Wide Web Consortium</organization>
2789      <address><email>ylafon@w3.org</email></address>
2790    </author>
2791    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2792      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2793      <address><email>julian.reschke@greenbytes.de</email></address>
2794    </author>
2795    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2796  </front>
2797  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
2798  <x:source href="p5-range.xml" basename="p5-range"/>
2799</reference>
2800
2801<reference anchor="Part6">
2802  <front>
2803    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2804    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2805      <organization abbrev="Day Software">Day Software</organization>
2806      <address><email>fielding@gbiv.com</email></address>
2807    </author>
2808    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2809      <organization>One Laptop per Child</organization>
2810      <address><email>jg@laptop.org</email></address>
2811    </author>
2812    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2813      <organization abbrev="HP">Hewlett-Packard Company</organization>
2814      <address><email>JeffMogul@acm.org</email></address>
2815    </author>
2816    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2817      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2818      <address><email>henrikn@microsoft.com</email></address>
2819    </author>
2820    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2821      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2822      <address><email>LMM@acm.org</email></address>
2823    </author>
2824    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2825      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2826      <address><email>paulle@microsoft.com</email></address>
2827    </author>
2828    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2829      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2830      <address><email>timbl@w3.org</email></address>
2831    </author>
2832    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2833      <organization abbrev="W3C">World Wide Web Consortium</organization>
2834      <address><email>ylafon@w3.org</email></address>
2835    </author>
2836    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2837      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2838      <address><email>julian.reschke@greenbytes.de</email></address>
2839    </author>
2840    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2841  </front>
2842  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2843  <x:source href="p6-cache.xml" basename="p6-cache"/>
2844</reference>
2845
2846<reference anchor="Part7">
2847  <front>
2848    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2849    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2850      <organization abbrev="Day Software">Day Software</organization>
2851      <address><email>fielding@gbiv.com</email></address>
2852    </author>
2853    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2854      <organization>One Laptop per Child</organization>
2855      <address><email>jg@laptop.org</email></address>
2856    </author>
2857    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2858      <organization abbrev="HP">Hewlett-Packard Company</organization>
2859      <address><email>JeffMogul@acm.org</email></address>
2860    </author>
2861    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2862      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2863      <address><email>henrikn@microsoft.com</email></address>
2864    </author>
2865    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2866      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2867      <address><email>LMM@acm.org</email></address>
2868    </author>
2869    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2870      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2871      <address><email>paulle@microsoft.com</email></address>
2872    </author>
2873    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2874      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2875      <address><email>timbl@w3.org</email></address>
2876    </author>
2877    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2878      <organization abbrev="W3C">World Wide Web Consortium</organization>
2879      <address><email>ylafon@w3.org</email></address>
2880    </author>
2881    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2882      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2883      <address><email>julian.reschke@greenbytes.de</email></address>
2884    </author>
2885    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2886  </front>
2887  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
2888  <x:source href="p7-auth.xml" basename="p7-auth"/>
2889</reference>
2890
2891<reference anchor="RFC2119">
2892  <front>
2893    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2894    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2895      <organization>Harvard University</organization>
2896      <address><email>sob@harvard.edu</email></address>
2897    </author>
2898    <date month="March" year="1997"/>
2899  </front>
2900  <seriesInfo name="BCP" value="14"/>
2901  <seriesInfo name="RFC" value="2119"/>
2902</reference>
2903
2904</references>
2905
2906<references title="Informative References">
2907
2908<reference anchor="RFC1945">
2909  <front>
2910    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2911    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2912      <organization>MIT, Laboratory for Computer Science</organization>
2913      <address><email>timbl@w3.org</email></address>
2914    </author>
2915    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2916      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2917      <address><email>fielding@ics.uci.edu</email></address>
2918    </author>
2919    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2920      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2921      <address><email>frystyk@w3.org</email></address>
2922    </author>
2923    <date month="May" year="1996"/>
2924  </front>
2925  <seriesInfo name="RFC" value="1945"/>
2926</reference>
2927
2928<reference anchor="RFC2068">
2929  <front>
2930    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2931    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2932      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2933      <address><email>fielding@ics.uci.edu</email></address>
2934    </author>
2935    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2936      <organization>MIT Laboratory for Computer Science</organization>
2937      <address><email>jg@w3.org</email></address>
2938    </author>
2939    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2940      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2941      <address><email>mogul@wrl.dec.com</email></address>
2942    </author>
2943    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2944      <organization>MIT Laboratory for Computer Science</organization>
2945      <address><email>frystyk@w3.org</email></address>
2946    </author>
2947    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2948      <organization>MIT Laboratory for Computer Science</organization>
2949      <address><email>timbl@w3.org</email></address>
2950    </author>
2951    <date month="January" year="1997"/>
2952  </front>
2953  <seriesInfo name="RFC" value="2068"/>
2954</reference>
2955
2956<reference anchor="RFC2616">
2957  <front>
2958    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2959    <author initials="R." surname="Fielding" fullname="R. Fielding">
2960      <organization>University of California, Irvine</organization>
2961      <address><email>fielding@ics.uci.edu</email></address>
2962    </author>
2963    <author initials="J." surname="Gettys" fullname="J. Gettys">
2964      <organization>W3C</organization>
2965      <address><email>jg@w3.org</email></address>
2966    </author>
2967    <author initials="J." surname="Mogul" fullname="J. Mogul">
2968      <organization>Compaq Computer Corporation</organization>
2969      <address><email>mogul@wrl.dec.com</email></address>
2970    </author>
2971    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2972      <organization>MIT Laboratory for Computer Science</organization>
2973      <address><email>frystyk@w3.org</email></address>
2974    </author>
2975    <author initials="L." surname="Masinter" fullname="L. Masinter">
2976      <organization>Xerox Corporation</organization>
2977      <address><email>masinter@parc.xerox.com</email></address>
2978    </author>
2979    <author initials="P." surname="Leach" fullname="P. Leach">
2980      <organization>Microsoft Corporation</organization>
2981      <address><email>paulle@microsoft.com</email></address>
2982    </author>
2983    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2984      <organization>W3C</organization>
2985      <address><email>timbl@w3.org</email></address>
2986    </author>
2987    <date month="June" year="1999"/>
2988  </front>
2989  <seriesInfo name="RFC" value="2616"/>
2990</reference>
2991
2992<reference anchor='RFC2817'>
2993  <front>
2994    <title>Upgrading to TLS Within HTTP/1.1</title>
2995    <author initials='R.' surname='Khare' fullname='R. Khare'>
2996      <organization>4K Associates / UC Irvine</organization>
2997      <address><email>rohit@4K-associates.com</email></address>
2998    </author>
2999    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3000      <organization>Agranat Systems, Inc.</organization>
3001      <address><email>lawrence@agranat.com</email></address>
3002    </author>
3003    <date year='2000' month='May' />
3004  </front>
3005  <seriesInfo name='RFC' value='2817' />
3006</reference>
3007
3008<reference anchor="RFC2822">
3009  <front>
3010    <title>Internet Message Format</title>
3011    <author initials="P." surname="Resnick" fullname="P. Resnick">
3012      <organization>QUALCOMM Incorporated</organization>
3013    </author>
3014    <date year="2001" month="April"/>
3015  </front> 
3016  <seriesInfo name="RFC" value="2822"/>
3017</reference>
3018
3019<reference anchor='RFC3864'>
3020  <front>
3021    <title>Registration Procedures for Message Header Fields</title>
3022    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3023      <organization>Nine by Nine</organization>
3024      <address><email>GK-IETF@ninebynine.org</email></address>
3025    </author>
3026    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3027      <organization>BEA Systems</organization>
3028      <address><email>mnot@pobox.com</email></address>
3029    </author>
3030    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3031      <organization>HP Labs</organization>
3032      <address><email>JeffMogul@acm.org</email></address>
3033    </author>
3034    <date year='2004' month='September' />
3035  </front>
3036  <seriesInfo name='BCP' value='90' />
3037  <seriesInfo name='RFC' value='3864' />
3038</reference>
3039
3040<reference anchor='RFC5226'>
3041  <front>
3042    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3043    <author initials='T.' surname='Narten' fullname='T. Narten'>
3044      <organization>IBM</organization>
3045      <address><email>narten@us.ibm.com</email></address>
3046    </author>
3047    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3048      <organization>Google</organization>
3049      <address><email>Harald@Alvestrand.no</email></address>
3050    </author>
3051    <date year='2008' month='May' />
3052  </front>
3053  <seriesInfo name='BCP' value='26' />
3054  <seriesInfo name='RFC' value='5226' />
3055</reference>
3056
3057</references>
3058
3059<section title="Compatibility with Previous Versions" anchor="compatibility">
3060<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
3061<t>
3062   Clarified which error code should be used for inbound server failures
3063   (e.g. DNS failures). (<xref target="status.504"/>).
3064</t>
3065<t>
3066   201 (Created) had a race that required an Etag be sent when a resource is
3067   first created. (<xref target="status.201"/>).
3068</t>
3069<t>
3070   Rewrite of message transmission requirements to make it much harder
3071   for implementors to get it wrong, as the consequences of errors here
3072   can have significant impact on the Internet, and to deal with the
3073   following problems:
3074  <list style="numbers">
3075      <t>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
3076         this was incorrectly placing a requirement on the behavior of
3077         an implementation of a future version of HTTP/1.x</t>
3078
3079      <t>Made it clear that user-agents should retry requests, not
3080         "clients" in general.</t>
3081
3082      <t>Converted requirements for clients to ignore unexpected 100
3083         (Continue) responses, and for proxies to forward 100 responses,
3084         into a general requirement for 1xx responses.</t>
3085
3086      <t>Modified some TCP-specific language, to make it clearer that
3087         non-TCP transports are possible for HTTP.</t>
3088
3089      <t>Require that the origin server &MUST-NOT; wait for the request
3090         body before it sends a required 100 (Continue) response.</t>
3091
3092      <t>Allow, rather than require, a server to omit 100 (Continue) if
3093         it has already seen some of the request body.</t>
3094
3095      <t>Allow servers to defend against denial-of-service attacks and
3096         broken clients.</t>
3097  </list>
3098</t>
3099<t>
3100   This change adds the Expect header and 417 status code.
3101</t>
3102<t>
3103   Clean up confusion between 403 and 404 responses. (Section <xref target="status.403" format="counter"/>,
3104   <xref target="status.404" format="counter"/>, and <xref target="status.410" format="counter"/>)
3105</t>
3106<t>
3107   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
3108   implemented in previous versions of this specification. See <xref target="RFC2068" x:fmt="of" x:sec="19.6.1"/>.
3109</t>
3110</section>
3111
3112<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3113<t>
3114  This document takes over the Status Code Registry, previously defined
3115  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3116  (<xref target="status.code.registry"/>)
3117</t>
3118<t>
3119  Clarify definition of POST.
3120  (<xref target="POST"/>)
3121</t>
3122<t>
3123  Failed to consider that there are
3124  many other request methods that are safe to automatically redirect,
3125  and further that the user agent is able to make that determination
3126  based on the request method semantics.
3127  (Sections <xref format="counter" target="status.301"/>,
3128  <xref format="counter" target="status.302"/> and
3129  <xref format="counter" target="status.307"/>)
3130</t>
3131<t>
3132  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3133  It used to indicate that the requested resource must be accessed through the
3134  proxy given by the Location field. The Location field gave the URI of the
3135  proxy. The recipient was expected to repeat this single request via the proxy.
3136  (<xref target="status.305"/>)
3137</t>
3138<t>
3139  Reclassify Allow header as response header, removing the option to
3140  specify it in a PUT request.
3141  Relax the server requirement on the contents of the Allow header and
3142  remove requirement on clients to always trust the header value.
3143  (<xref target="header.allow"/>)
3144</t>
3145<t>
3146  Correct syntax of Location header to allow fragment,
3147  as referred symbol wasn't what was expected, and add some
3148  clarifications as to when it would not be appropriate.
3149  (<xref target="header.location"/>)
3150</t>
3151<t>
3152  In the description of the Server header, the Via field
3153  was described as a SHOULD. The requirement was and is stated
3154  correctly in the description of the Via header in &header-via;.
3155  (<xref target="header.server"/>)
3156</t>
3157</section>
3158
3159</section>
3160
3161<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3162
3163<section title="Since RFC2616">
3164<t>
3165  Extracted relevant partitions from <xref target="RFC2616"/>.
3166</t>
3167</section>
3168
3169<section title="Since draft-ietf-httpbis-p2-semantics-00">
3170<t>
3171  Closed issues:
3172  <list style="symbols"> 
3173    <t>
3174      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3175      "Via is a MUST"
3176      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3177    </t>
3178    <t>
3179      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3180      "Fragments allowed in Location"
3181      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3182    </t>
3183    <t>
3184      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3185      "Safe Methods vs Redirection"
3186      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3187    </t>
3188    <t>
3189      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3190      "Revise description of the POST method"
3191      (<eref target="http://purl.org/NET/http-errata#post"/>)
3192    </t>
3193    <t>
3194      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3195      "Normative and Informative references"
3196    </t>
3197    <t>
3198      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3199      "RFC2606 Compliance"
3200    </t>
3201    <t>
3202      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3203      "Informative references"
3204    </t>
3205    <t>
3206      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3207      "Redundant cross-references"
3208    </t>
3209  </list>
3210</t>
3211<t>
3212  Other changes:
3213  <list style="symbols"> 
3214    <t>
3215      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3216    </t>
3217  </list>
3218</t>
3219</section>
3220
3221<section title="Since draft-ietf-httpbis-p2-semantics-01">
3222<t>
3223  Closed issues:
3224  <list style="symbols"> 
3225    <t>
3226      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3227      "PUT side effects"
3228    </t>
3229    <t>
3230      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3231      "Duplicate Host header requirements"
3232    </t>
3233  </list>
3234</t>
3235<t>
3236  Ongoing work on ABNF conversion (<eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3237  <list style="symbols"> 
3238    <t>
3239      Move "Product Tokens" section (back) into Part 1, as "token" is used
3240      in the definition of the Upgrade header.
3241    </t>
3242    <t>
3243      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3244    </t>
3245    <t>
3246      Copy definition of delta-seconds from Part6 instead of referencing it.
3247    </t>
3248  </list>
3249</t>
3250</section>
3251
3252<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3253<t>
3254  Closed issues:
3255  <list style="symbols"> 
3256    <t>
3257      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3258      "Requiring Allow in 405 responses"
3259    </t>
3260    <t>
3261      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3262      "Status Code Registry"
3263    </t>
3264    <t>
3265      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3266      "Redirection vs. Location"
3267    </t>
3268    <t>
3269      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3270      "Cacheability of 303 response"
3271    </t>
3272    <t>
3273      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3274      "305 Use Proxy"
3275    </t>
3276    <t>
3277      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3278      "Classification for Allow header"
3279    </t>
3280    <t>
3281      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3282      "PUT - 'store under' vs 'store at'"
3283    </t>
3284  </list>
3285</t>
3286<t>
3287  Ongoing work on IANA Message Header Registration (<eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3288  <list style="symbols"> 
3289    <t>
3290      Reference RFC 3984, and update header registrations for headers defined
3291      in this document.
3292    </t>
3293  </list>
3294</t>
3295<t>
3296  Ongoing work on ABNF conversion (<eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3297  <list style="symbols"> 
3298    <t>
3299      Replace string literals when the string really is case-sensitive (method).
3300    </t>
3301  </list>
3302</t>
3303</section>
3304
3305<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3306<t>
3307  Closed issues:
3308  <list style="symbols"> 
3309    <t>
3310      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
3311      "OPTIONS request bodies"
3312    </t>
3313    <t>
3314      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
3315      "Description of CONNECT should refer to RFC2817"
3316    </t>
3317  </list>
3318</t>
3319<t>
3320  Ongoing work on Method Registry (<eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
3321  <list style="symbols"> 
3322    <t>
3323      Added initial proposal for registration process, plus initial
3324      content (non-HTTP/1.1 methods to be added by a separate specification).
3325    </t>
3326  </list>
3327</t>
3328</section>
3329
3330</section>
3331
3332</back>
3333</rfc>
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