source: draft-ietf-httpbis/latest/p2-semantics.xml @ 271

Last change on this file since 271 was 271, checked in by julian.reschke@…, 11 years ago

Bump up document dates.

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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:anchor-alias value="Accept"/>
306  <x:ref>comment</x:ref>       = &lt;comment, defined in &basic-rules;&gt;
307  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
308  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
309</artwork></figure>
310<t anchor="abnf.dependencies">
311  <x:anchor-alias value="absoluteURI"/>
312  <x:anchor-alias value="Accept"/>
313  <x:anchor-alias value="Accept-Charset"/>
314  <x:anchor-alias value="Accept-Encoding"/>
315  <x:anchor-alias value="Accept-Language"/>
316  <x:anchor-alias value="Accept-Ranges"/>
317  <x:anchor-alias value="Age"/>
318  <x:anchor-alias value="Authorization"/>
319  <x:anchor-alias value="ETag"/>
320  <x:anchor-alias value="fragment"/>
321  <x:anchor-alias value="Host"/>
322  <x:anchor-alias value="HTTP-date"/>
323  <x:anchor-alias value="If-Match"/>
324  <x:anchor-alias value="If-Modified-Since"/>
325  <x:anchor-alias value="If-None-Match"/>
326  <x:anchor-alias value="If-Range"/>
327  <x:anchor-alias value="If-Unmodified-Since"/>
328  <x:anchor-alias value="product"/>
329  <x:anchor-alias value="Proxy-Authenticate"/>
330  <x:anchor-alias value="Proxy-Authorization"/>
331  <x:anchor-alias value="Range"/>
332  <x:anchor-alias value="relativeURI"/>
333  <x:anchor-alias value="TE"/>
334  <x:anchor-alias value="Vary"/>
335  <x:anchor-alias value="WWW-Authenticate"/>
336  The ABNF rules below are defined in other parts:
337</t>
338<figure><!--Part1--><artwork type="abnf2616">
339  <x:ref>absoluteURI</x:ref>   = &lt;absoluteURI, defined in &general-syntax;&gt;
340  <x:ref>fragment</x:ref>      = &lt;fragment, defined in &general-syntax;&gt;
341  <x:ref>Host</x:ref>          = &lt;Host, defined in &header-host;&gt;
342  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
343  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
344  <x:ref>relativeURI</x:ref>   = &lt;relativeURI, defined in &general-syntax;&gt;
345  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
346</artwork></figure>
347<figure><!--Part3--><artwork type="abnf2616">
348  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
349  <x:ref>Accept-Charset</x:ref> =
350             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
351  <x:ref>Accept-Encoding</x:ref> =
352             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
353  <x:ref>Accept-Language</x:ref> =
354             &lt;Accept-Language, defined in &header-accept-language;&gt;
355</artwork></figure>
356<figure><!--Part4--><artwork type="abnf2616">
357  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
358  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
359  <x:ref>If-Modified-Since</x:ref> =
360             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
361  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
362  <x:ref>If-Unmodified-Since</x:ref> =
363             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
364</artwork></figure>
365<figure><!--Part5--><artwork type="abnf2616">
366  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
367  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
368  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
369</artwork></figure>
370<figure><!--Part6--><artwork type="abnf2616">
371  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
372  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
373</artwork><!--Part7--></figure>
374<figure><artwork type="abnf2616">
375  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
376  <x:ref>Proxy-Authenticate</x:ref> =
377             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
378  <x:ref>Proxy-Authorization</x:ref> =
379             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
380  <x:ref>WWW-Authenticate</x:ref> =
381             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
382</artwork></figure>
383</section>
384
385<section title="Method" anchor="method">
386  <x:anchor-alias value="Method"/>
387  <x:anchor-alias value="extension-method"/>
388<t>
389   The Method  token indicates the method to be performed on the
390   resource identified by the Request-URI. The method is case-sensitive.
391</t>
392<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
393  <x:ref>Method</x:ref>         = %x4F.50.54.49.4F.4E.53   ; "OPTIONS", <xref target="OPTIONS"/>
394                 | %x47.45.54               ; "GET", <xref target="GET"/>
395                 | %x48.45.41.44            ; "HEAD", <xref target="HEAD"/>
396                 | %x50.4F.53.54            ; "POST", <xref target="POST"/>
397                 | %x50.55.54               ; "PUT", <xref target="PUT"/>
398                 | %x44.45.4C.45.54.45      ; "DELETE", <xref target="DELETE"/>
399                 | %x54.52.41.43.45         ; "TRACE", <xref target="TRACE"/>
400                 | %x43.4F.4E.4E.45.43.54   ; "CONNECT", <xref target="CONNECT"/>
401                 | <x:ref>extension-method</x:ref>
402  <x:ref>extension-method</x:ref> = <x:ref>token</x:ref>
403</artwork></figure>
404<t>
405   The list of methods allowed by a resource can be specified in an
406   Allow header field (<xref target="header.allow"/>). The return code of the response
407   always notifies the client whether a method is currently allowed on a
408   resource, since the set of allowed methods can change dynamically. An
409   origin server &SHOULD; return the status code 405 (Method Not Allowed)
410   if the method is known by the origin server but not allowed for the
411   requested resource, and 501 (Not Implemented) if the method is
412   unrecognized or not implemented by the origin server. The methods GET
413   and HEAD &MUST; be supported by all general-purpose servers. All other
414   methods are &OPTIONAL;; however, if the above methods are implemented,
415   they &MUST; be implemented with the same semantics as those specified
416   in <xref target="method.definitions"/>.
417</t>
418
419<section title="Method Registry" anchor="method.registry">
420<t>
421  The HTTP Method Registry defines the name space for the Method token in the
422  Request line of an HTTP request.
423</t>
424<t>
425  Values to be added to this name space are subject to IETF review
426  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
427  new method names should be traceable through statuses of either 'Obsoletes'
428  or 'Updates' to this document.
429</t>
430<t>
431  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
432</t>
433</section>
434</section>
435
436<section title="Request Header Fields" anchor="request.header.fields">
437  <x:anchor-alias value="extension-code"/>
438  <x:anchor-alias value="request-header"/>
439<t>
440   The request-header fields allow the client to pass additional
441   information about the request, and about the client itself, to the
442   server. These fields act as request modifiers, with semantics
443   equivalent to the parameters on a programming language method
444   invocation.
445</t>
446<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
447  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
448                 | <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
449                 | <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
450                 | <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
451                 | <x:ref>Authorization</x:ref>            ; &header-authorization;
452                 | <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
453                 | <x:ref>From</x:ref>                     ; <xref target="header.from"/>
454                 | <x:ref>Host</x:ref>                     ; &header-host;
455                 | <x:ref>If-Match</x:ref>                 ; &header-if-match;
456                 | <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
457                 | <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
458                 | <x:ref>If-Range</x:ref>                 ; &header-if-range;
459                 | <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
460                 | <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
461                 | <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
462                 | <x:ref>Range</x:ref>                    ; &header-range;
463                 | <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
464                 | <x:ref>TE</x:ref>                       ; &header-te;
465                 | <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
466</artwork></figure>
467<t>
468   Request-header field names can be extended reliably only in
469   combination with a change in the protocol version. However, new or
470   experimental header fields &MAY; be given the semantics of request-header
471   fields if all parties in the communication recognize them to
472   be request-header fields. Unrecognized header fields are treated as
473   entity-header fields.
474</t>
475</section>
476
477<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
478  <x:anchor-alias value="Reason-Phrase"/>
479  <x:anchor-alias value="Status-Code"/>
480<t>
481   The Status-Code element is a 3-digit integer result code of the
482   attempt to understand and satisfy the request. The status codes listed
483   below are defined in <xref target="status.codes"/>.
484   The Reason-Phrase is intended to give a short
485   textual description of the Status-Code. The Status-Code is intended
486   for use by automata and the Reason-Phrase is intended for the human
487   user. The client is not required to examine or display the Reason-Phrase.
488</t>
489<t> 
490   The individual values of the numeric status codes defined for
491   HTTP/1.1, and an example set of corresponding Reason-Phrase's, are
492   presented below. The reason phrases listed here are only
493   recommendations -- they &MAY; be replaced by local equivalents without
494   affecting the protocol.
495</t>
496<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"/>
497  <x:ref>Status-Code</x:ref>    =
498         "100"  ; <xref target="status.100"/>: Continue
499       | "101"  ; <xref target="status.101"/>: Switching Protocols
500       | "200"  ; <xref target="status.200"/>: OK
501       | "201"  ; <xref target="status.201"/>: Created
502       | "202"  ; <xref target="status.202"/>: Accepted
503       | "203"  ; <xref target="status.203"/>: Non-Authoritative Information
504       | "204"  ; <xref target="status.204"/>: No Content
505       | "205"  ; <xref target="status.205"/>: Reset Content
506       | "206"  ; <xref target="status.206"/>: Partial Content
507       | "300"  ; <xref target="status.300"/>: Multiple Choices
508       | "301"  ; <xref target="status.301"/>: Moved Permanently
509       | "302"  ; <xref target="status.302"/>: Found
510       | "303"  ; <xref target="status.303"/>: See Other
511       | "304"  ; <xref target="status.304"/>: Not Modified
512       | "305"  ; <xref target="status.305"/>: Use Proxy
513       | "307"  ; <xref target="status.307"/>: Temporary Redirect
514       | "400"  ; <xref target="status.400"/>: Bad Request
515       | "401"  ; <xref target="status.401"/>: Unauthorized
516       | "402"  ; <xref target="status.402"/>: Payment Required
517       | "403"  ; <xref target="status.403"/>: Forbidden
518       | "404"  ; <xref target="status.404"/>: Not Found
519       | "405"  ; <xref target="status.405"/>: Method Not Allowed
520       | "406"  ; <xref target="status.406"/>: Not Acceptable
521       | "407"  ; <xref target="status.407"/>: Proxy Authentication Required
522       | "408"  ; <xref target="status.408"/>: Request Time-out
523       | "409"  ; <xref target="status.409"/>: Conflict
524       | "410"  ; <xref target="status.410"/>: Gone
525       | "411"  ; <xref target="status.411"/>: Length Required
526       | "412"  ; <xref target="status.412"/>: Precondition Failed
527       | "413"  ; <xref target="status.413"/>: Request Entity Too Large
528       | "414"  ; <xref target="status.414"/>: Request-URI Too Large
529       | "415"  ; <xref target="status.415"/>: Unsupported Media Type
530       | "416"  ; <xref target="status.416"/>: Requested range not satisfiable
531       | "417"  ; <xref target="status.417"/>: Expectation Failed
532       | "500"  ; <xref target="status.500"/>: Internal Server Error
533       | "501"  ; <xref target="status.501"/>: Not Implemented
534       | "502"  ; <xref target="status.502"/>: Bad Gateway
535       | "503"  ; <xref target="status.503"/>: Service Unavailable
536       | "504"  ; <xref target="status.504"/>: Gateway Time-out
537       | "505"  ; <xref target="status.505"/>: HTTP Version not supported
538       | <x:ref>extension-code</x:ref>
539
540  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
541  <x:ref>Reason-Phrase</x:ref>  = *&lt;<x:ref>TEXT</x:ref>, excluding <x:ref>CR</x:ref>, <x:ref>LF</x:ref>&gt;
542</artwork></figure>
543<t>
544   HTTP status codes are extensible. HTTP applications are not required
545   to understand the meaning of all registered status codes, though such
546   understanding is obviously desirable. However, applications &MUST;
547   understand the class of any status code, as indicated by the first
548   digit, and treat any unrecognized response as being equivalent to the
549   x00 status code of that class, with the exception that an
550   unrecognized response &MUST-NOT; be cached. For example, if an
551   unrecognized status code of 431 is received by the client, it can
552   safely assume that there was something wrong with its request and
553   treat the response as if it had received a 400 status code. In such
554   cases, user agents &SHOULD; present to the user the entity returned
555   with the response, since that entity is likely to include human-readable
556   information which will explain the unusual status.
557</t>
558
559<section title="Status Code Registry" anchor="status.code.registry">
560<t>
561  The HTTP Status Code Registry defines the name space for the Status-Code
562  token in the Status line of an HTTP response.
563</t>
564<t>
565  Values to be added to this name space are subject to IETF review
566  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
567  new status codes should be traceable through statuses of either 'Obsoletes'
568  or 'Updates' to this document.
569</t>
570<t>
571  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
572</t>
573</section>
574
575</section>
576
577<section title="Response Header Fields" anchor="response.header.fields">
578  <x:anchor-alias value="response-header"/>
579<t>
580   The response-header fields allow the server to pass additional
581   information about the response which cannot be placed in the Status-Line.
582   These header fields give information about the server and about
583   further access to the resource identified by the Request-URI.
584</t>
585<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
586  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
587                  | <x:ref>Age</x:ref>                     ; &header-age;
588                  | <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
589                  | <x:ref>ETag</x:ref>                    ; &header-etag;
590                  | <x:ref>Location</x:ref>                ; <xref target="header.location"/>
591                  | <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
592                  | <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
593                  | <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
594                  | <x:ref>Vary</x:ref>                    ; &header-vary;
595                  | <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
596</artwork></figure>
597<t>
598   Response-header field names can be extended reliably only in
599   combination with a change in the protocol version. However, new or
600   experimental header fields &MAY; be given the semantics of response-header
601   fields if all parties in the communication recognize them to
602   be response-header fields. Unrecognized header fields are treated as
603   entity-header fields.
604</t>
605</section>
606
607<section title="Entity" anchor="entity">
608<t>
609   Request and Response messages &MAY; transfer an entity if not otherwise
610   restricted by the request method or response status code. An entity
611   consists of entity-header fields and an entity-body, although some
612   responses will only include the entity-headers. HTTP entity-body and
613   entity-header fields are defined in &payload;.
614</t>
615<t>
616   An entity-body is only present in a message when a message-body is
617   present, as described in &message-body;. The entity-body is obtained
618   from the message-body by decoding any Transfer-Encoding that might
619   have been applied to ensure safe and proper transfer of the message.
620</t>
621</section>
622
623
624<section title="Method Definitions" anchor="method.definitions">
625<t>
626   The set of common methods for HTTP/1.1 is defined below. Although
627   this set can be expanded, additional methods cannot be assumed to
628   share the same semantics for separately extended clients and servers.
629</t>
630
631<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
632
633<section title="Safe Methods" anchor="safe.methods">
634<t>
635   Implementors should be aware that the software represents the user in
636   their interactions over the Internet, and should be careful to allow
637   the user to be aware of any actions they might take which may have an
638   unexpected significance to themselves or others.
639</t>
640<t>
641   In particular, the convention has been established that the GET and
642   HEAD methods &SHOULD-NOT;  have the significance of taking an action
643   other than retrieval. These methods ought to be considered "safe".
644   This allows user agents to represent other methods, such as POST, PUT
645   and DELETE, in a special way, so that the user is made aware of the
646   fact that a possibly unsafe action is being requested.
647</t>
648<t>
649   Naturally, it is not possible to ensure that the server does not
650   generate side-effects as a result of performing a GET request; in
651   fact, some dynamic resources consider that a feature. The important
652   distinction here is that the user did not request the side-effects,
653   so therefore cannot be held accountable for them.
654</t>
655</section>
656
657<section title="Idempotent Methods" anchor="idempotent.methods">
658<t>
659   Methods can also have the property of "idempotence" in that (aside
660   from error or expiration issues) the side-effects of N &gt; 0 identical
661   requests is the same as for a single request. The methods GET, HEAD,
662   PUT and DELETE share this property. Also, the methods OPTIONS and
663   TRACE &SHOULD-NOT;  have side effects, and so are inherently idempotent.
664</t>
665<t>
666   However, it is possible that a sequence of several requests is non-idempotent,
667   even if all of the methods executed in that sequence are
668   idempotent. (A sequence is idempotent if a single execution of the
669   entire sequence always yields a result that is not changed by a
670   reexecution of all, or part, of that sequence.) For example, a
671   sequence is non-idempotent if its result depends on a value that is
672   later modified in the same sequence.
673</t>
674<t>
675   A sequence that never has side effects is idempotent, by definition
676   (provided that no concurrent operations are being executed on the
677   same set of resources).
678</t>
679</section>
680</section>
681
682<section title="OPTIONS" anchor="OPTIONS">
683  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
684  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
685<t>
686   The OPTIONS method represents a request for information about the
687   communication options available on the request/response chain
688   identified by the Request-URI. This method allows the client to
689   determine the options and/or requirements associated with a resource,
690   or the capabilities of a server, without implying a resource action
691   or initiating a resource retrieval.
692</t>
693<t>
694   Responses to this method are not cacheable.
695</t>
696<t>
697   If the OPTIONS request includes an entity-body (as indicated by the
698   presence of Content-Length or Transfer-Encoding), then the media type
699   &MUST; be indicated by a Content-Type field. Although this
700   specification does not define any use for such a body, future
701   extensions to HTTP might use the OPTIONS body to make more detailed
702   queries on the server. A server that does not support such an
703   extension &MAY; discard the request body.
704</t>
705<t>
706   If the Request-URI is an asterisk ("*"), the OPTIONS request is
707   intended to apply to the server in general rather than to a specific
708   resource. Since a server's communication options typically depend on
709   the resource, the "*" request is only useful as a "ping" or "no-op"
710   type of method; it does nothing beyond allowing the client to test
711   the capabilities of the server. For example, this can be used to test
712   a proxy for HTTP/1.1 compliance (or lack thereof).
713</t>
714<t>
715   If the Request-URI is not an asterisk, the OPTIONS request applies
716   only to the options that are available when communicating with that
717   resource.
718</t>
719<t>
720   A 200 response &SHOULD; include any header fields that indicate
721   optional features implemented by the server and applicable to that
722   resource (e.g., Allow), possibly including extensions not defined by
723   this specification. The response body, if any, &SHOULD; also include
724   information about the communication options. The format for such a
725   body is not defined by this specification, but might be defined by
726   future extensions to HTTP. Content negotiation &MAY; be used to select
727   the appropriate response format. If no response body is included, the
728   response &MUST; include a Content-Length field with a field-value of
729   "0".
730</t>
731<t>
732   The Max-Forwards request-header field &MAY; be used to target a
733   specific proxy in the request chain. When a proxy receives an OPTIONS
734   request on an absoluteURI for which request forwarding is permitted,
735   the proxy &MUST; check for a Max-Forwards field. If the Max-Forwards
736   field-value is zero ("0"), the proxy &MUST-NOT; forward the message;
737   instead, the proxy &SHOULD; respond with its own communication options.
738   If the Max-Forwards field-value is an integer greater than zero, the
739   proxy &MUST; decrement the field-value when it forwards the request. If
740   no Max-Forwards field is present in the request, then the forwarded
741   request &MUST-NOT; include a Max-Forwards field.
742</t>
743</section>
744
745<section title="GET" anchor="GET">
746  <iref primary="true" item="GET method" x:for-anchor=""/>
747  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
748<t>
749   The GET method means retrieve whatever information (in the form of an
750   entity) is identified by the Request-URI. If the Request-URI refers
751   to a data-producing process, it is the produced data which shall be
752   returned as the entity in the response and not the source text of the
753   process, unless that text happens to be the output of the process.
754</t>
755<t>
756   The semantics of the GET method change to a "conditional GET" if the
757   request message includes an If-Modified-Since, If-Unmodified-Since,
758   If-Match, If-None-Match, or If-Range header field. A conditional GET
759   method requests that the entity be transferred only under the
760   circumstances described by the conditional header field(s). The
761   conditional GET method is intended to reduce unnecessary network
762   usage by allowing cached entities to be refreshed without requiring
763   multiple requests or transferring data already held by the client.
764</t>
765<t>
766   The semantics of the GET method change to a "partial GET" if the
767   request message includes a Range header field. A partial GET requests
768   that only part of the entity be transferred, as described in &header-range;.
769   The partial GET method is intended to reduce unnecessary
770   network usage by allowing partially-retrieved entities to be
771   completed without transferring data already held by the client.
772</t>
773<t>
774   The response to a GET request is cacheable if and only if it meets
775   the requirements for HTTP caching described in &caching;.
776</t>
777<t>
778   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
779</t>
780</section>
781
782<section title="HEAD" anchor="HEAD">
783  <iref primary="true" item="HEAD method" x:for-anchor=""/>
784  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
785<t>
786   The HEAD method is identical to GET except that the server &MUST-NOT;
787   return a message-body in the response. The metainformation contained
788   in the HTTP headers in response to a HEAD request &SHOULD; be identical
789   to the information sent in response to a GET request. This method can
790   be used for obtaining metainformation about the entity implied by the
791   request without transferring the entity-body itself. This method is
792   often used for testing hypertext links for validity, accessibility,
793   and recent modification.
794</t>
795<t>
796   The response to a HEAD request &MAY; be cacheable in the sense that the
797   information contained in the response &MAY; be used to update a
798   previously cached entity from that resource. If the new field values
799   indicate that the cached entity differs from the current entity (as
800   would be indicated by a change in Content-Length, Content-MD5, ETag
801   or Last-Modified), then the cache &MUST; treat the cache entry as
802   stale.
803</t>
804</section>
805
806<section title="POST" anchor="POST">
807  <iref primary="true" item="POST method" x:for-anchor=""/>
808  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
809<t>
810   The POST method is used to request that the origin server accept the
811   entity enclosed in the request as data to be processed by the resource
812   identified by the Request-URI in the Request-Line. POST is designed
813   to allow a uniform method to cover the following functions:
814  <list style="symbols">
815    <t>
816      Annotation of existing resources;
817    </t>
818    <t>
819        Posting a message to a bulletin board, newsgroup, mailing list,
820        or similar group of articles;
821    </t>
822    <t>
823        Providing a block of data, such as the result of submitting a
824        form, to a data-handling process;
825    </t>
826    <t>
827        Extending a database through an append operation.
828    </t>
829  </list>
830</t>
831<t>
832   The actual function performed by the POST method is determined by the
833   server and is usually dependent on the Request-URI.
834</t>
835<t>
836   The action performed by the POST method might not result in a
837   resource that can be identified by a URI. In this case, either 200
838   (OK) or 204 (No Content) is the appropriate response status,
839   depending on whether or not the response includes an entity that
840   describes the result.
841</t>
842<t>
843   If a resource has been created on the origin server, the response
844   &SHOULD; be 201 (Created) and contain an entity which describes the
845   status of the request and refers to the new resource, and a Location
846   header (see <xref target="header.location"/>).
847</t>
848<t>
849   Responses to this method are not cacheable, unless the response
850   includes appropriate Cache-Control or Expires header fields. However,
851   the 303 (See Other) response can be used to direct the user agent to
852   retrieve a cacheable resource.
853</t>
854</section>
855
856<section title="PUT" anchor="PUT">
857  <iref primary="true" item="PUT method" x:for-anchor=""/>
858  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
859<t>
860   The PUT method requests that the enclosed entity be stored at the
861   supplied Request-URI. If the Request-URI refers to an already
862   existing resource, the enclosed entity &SHOULD; be considered as a
863   modified version of the one residing on the origin server. If the
864   Request-URI does not point to an existing resource, and that URI is
865   capable of being defined as a new resource by the requesting user
866   agent, the origin server can create the resource with that URI. If a
867   new resource is created at the Request-URI, the origin server &MUST;
868         inform the user agent
869   via the 201 (Created) response. If an existing resource is modified,
870   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
871   to indicate successful completion of the request. If the resource
872   could not be created or modified with the Request-URI, an appropriate
873   error response &SHOULD; be given that reflects the nature of the
874   problem. The recipient of the entity &MUST-NOT; ignore any Content-*
875   (e.g. Content-Range) headers that it does not understand or implement
876   and &MUST; return a 501 (Not Implemented) response in such cases.
877</t>
878<t>
879   If the request passes through a cache and the Request-URI identifies
880   one or more currently cached entities, those entries &SHOULD; be
881   treated as stale. Responses to this method are not cacheable.
882</t>
883<t>
884   The fundamental difference between the POST and PUT requests is
885   reflected in the different meaning of the Request-URI. The URI in a
886   POST request identifies the resource that will handle the enclosed
887   entity. That resource might be a data-accepting process, a gateway to
888   some other protocol, or a separate entity that accepts annotations.
889   In contrast, the URI in a PUT request identifies the entity enclosed
890   with the request -- the user agent knows what URI is intended and the
891   server &MUST-NOT; attempt to apply the request to some other resource.
892   If the server desires that the request be applied to a different URI,
893   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
894   then make its own decision regarding whether or not to redirect the
895   request.
896</t>
897<t>
898   A single resource &MAY; be identified by many different URIs. For
899   example, an article might have a URI for identifying "the current
900   version" which is separate from the URI identifying each particular
901   version. In this case, a PUT request on a general URI might result in
902   several other URIs being defined by the origin server.
903</t>
904<t>
905   HTTP/1.1 does not define how a PUT method affects the state of an
906   origin server.
907</t>
908<t>
909   Unless otherwise specified for a particular entity-header, the
910   entity-headers in the PUT request &SHOULD; be applied to the resource
911   created or modified by the PUT.
912</t>
913</section>
914
915<section title="DELETE" anchor="DELETE">
916  <iref primary="true" item="DELETE method" x:for-anchor=""/>
917  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
918<t>
919   The DELETE method requests that the origin server delete the resource
920   identified by the Request-URI. This method &MAY; be overridden by human
921   intervention (or other means) on the origin server. The client cannot
922   be guaranteed that the operation has been carried out, even if the
923   status code returned from the origin server indicates that the action
924   has been completed successfully. However, the server &SHOULD-NOT; 
925   indicate success unless, at the time the response is given, it
926   intends to delete the resource or move it to an inaccessible
927   location.
928</t>
929<t>
930   A successful response &SHOULD; be 200 (OK) if the response includes an
931   entity describing the status, 202 (Accepted) if the action has not
932   yet been enacted, or 204 (No Content) if the action has been enacted
933   but the response does not include an entity.
934</t>
935<t>
936   If the request passes through a cache and the Request-URI identifies
937   one or more currently cached entities, those entries &SHOULD; be
938   treated as stale. Responses to this method are not cacheable.
939</t>
940</section>
941
942<section title="TRACE" anchor="TRACE">
943  <iref primary="true" item="TRACE method" x:for-anchor=""/>
944  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
945<t>
946   The TRACE method is used to invoke a remote, application-layer loop-back
947   of the request message. The final recipient of the request
948   &SHOULD; reflect the message received back to the client as the
949   entity-body of a 200 (OK) response. The final recipient is either the
950   origin server or the first proxy or gateway to receive a Max-Forwards
951   value of zero (0) in the request (see <xref target="header.max-forwards"/>). A TRACE request
952   &MUST-NOT; include an entity.
953</t>
954<t>
955   TRACE allows the client to see what is being received at the other
956   end of the request chain and use that data for testing or diagnostic
957   information. The value of the Via header field (&header-via;) is of
958   particular interest, since it acts as a trace of the request chain.
959   Use of the Max-Forwards header field allows the client to limit the
960   length of the request chain, which is useful for testing a chain of
961   proxies forwarding messages in an infinite loop.
962</t>
963<t>
964   If the request is valid, the response &SHOULD; contain the entire
965   request message in the entity-body, with a Content-Type of
966   "message/http" (see &media-type-message-http;). Responses to this method
967   &MUST-NOT; be cached.
968</t>
969</section>
970
971<section title="CONNECT" anchor="CONNECT">
972  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
973  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
974<t>
975   This specification reserves the method name CONNECT for use with a
976   proxy that can dynamically switch to being a tunnel (e.g. SSL
977   tunneling <xref target="Luo1998"/>).
978</t>
979</section>
980</section>
981
982
983<section title="Status Code Definitions" anchor="status.codes">
984<t>
985   Each Status-Code is described below, including a description of which
986   method(s) it can follow and any metainformation required in the
987   response.
988</t>
989
990<section title="Informational 1xx" anchor="status.1xx">
991<t>
992   This class of status code indicates a provisional response,
993   consisting only of the Status-Line and optional headers, and is
994   terminated by an empty line. There are no required headers for this
995   class of status code. Since HTTP/1.0 did not define any 1xx status
996   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
997   except under experimental conditions.
998</t>
999<t>
1000   A client &MUST; be prepared to accept one or more 1xx status responses
1001   prior to a regular response, even if the client does not expect a 100
1002   (Continue) status message. Unexpected 1xx status responses &MAY; be
1003   ignored by a user agent.
1004</t>
1005<t>
1006   Proxies &MUST; forward 1xx responses, unless the connection between the
1007   proxy and its client has been closed, or unless the proxy itself
1008   requested the generation of the 1xx response. (For example, if a
1009   proxy adds a "Expect: 100-continue" field when it forwards a request,
1010   then it need not forward the corresponding 100 (Continue)
1011   response(s).)
1012</t>
1013
1014<section title="100 Continue" anchor="status.100">
1015  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1016  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1017<t>
1018   The client &SHOULD; continue with its request. This interim response is
1019   used to inform the client that the initial part of the request has
1020   been received and has not yet been rejected by the server. The client
1021   &SHOULD; continue by sending the remainder of the request or, if the
1022   request has already been completed, ignore this response. The server
1023   &MUST; send a final response after the request has been completed. See
1024   &use100; for detailed discussion of the use and handling of this
1025   status code.
1026</t>
1027</section>
1028
1029<section title="101 Switching Protocols" anchor="status.101">
1030  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1031  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1032<t>
1033   The server understands and is willing to comply with the client's
1034   request, via the Upgrade message header field (&header-upgrade;), for a
1035   change in the application protocol being used on this connection. The
1036   server will switch protocols to those defined by the response's
1037   Upgrade header field immediately after the empty line which
1038   terminates the 101 response.
1039</t>
1040<t>
1041   The protocol &SHOULD; be switched only when it is advantageous to do
1042   so. For example, switching to a newer version of HTTP is advantageous
1043   over older versions, and switching to a real-time, synchronous
1044   protocol might be advantageous when delivering resources that use
1045   such features.
1046</t>
1047</section>
1048</section>
1049
1050<section title="Successful 2xx" anchor="status.2xx">
1051<t>
1052   This class of status code indicates that the client's request was
1053   successfully received, understood, and accepted.
1054</t>
1055
1056<section title="200 OK" anchor="status.200">
1057  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1058  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1059<t>
1060   The request has succeeded. The information returned with the response
1061   is dependent on the method used in the request, for example:
1062  <list style="hanging">
1063    <t hangText="GET">
1064          an entity corresponding to the requested resource is sent in
1065          the response;
1066    </t>
1067    <t hangText="HEAD">
1068          the entity-header fields corresponding to the requested
1069          resource are sent in the response without any message-body;
1070    </t>
1071    <t hangText="POST">
1072      an entity describing or containing the result of the action;
1073    </t>
1074    <t hangText="TRACE">
1075      an entity containing the request message as received by the
1076      end server.
1077    </t>
1078  </list>
1079</t>
1080</section>
1081
1082<section title="201 Created" anchor="status.201">
1083  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1084  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1085<t>
1086   The request has been fulfilled and resulted in a new resource being
1087   created. The newly created resource can be referenced by the URI(s)
1088   returned in the entity of the response, with the most specific URI
1089   for the resource given by a Location header field. The response
1090   &SHOULD; include an entity containing a list of resource
1091   characteristics and location(s) from which the user or user agent can
1092   choose the one most appropriate. The entity format is specified by
1093   the media type given in the Content-Type header field. The origin
1094   server &MUST; create the resource before returning the 201 status code.
1095   If the action cannot be carried out immediately, the server &SHOULD;
1096   respond with 202 (Accepted) response instead.
1097</t>
1098<t>
1099   A 201 response &MAY; contain an ETag response header field indicating
1100   the current value of the entity tag for the requested variant just
1101   created, see &header-etag;.
1102</t>
1103</section>
1104
1105<section title="202 Accepted" anchor="status.202">
1106  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1107  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1108<t>
1109   The request has been accepted for processing, but the processing has
1110   not been completed.  The request might or might not eventually be
1111   acted upon, as it might be disallowed when processing actually takes
1112   place. There is no facility for re-sending a status code from an
1113   asynchronous operation such as this.
1114</t>
1115<t>
1116   The 202 response is intentionally non-committal. Its purpose is to
1117   allow a server to accept a request for some other process (perhaps a
1118   batch-oriented process that is only run once per day) without
1119   requiring that the user agent's connection to the server persist
1120   until the process is completed. The entity returned with this
1121   response &SHOULD; include an indication of the request's current status
1122   and either a pointer to a status monitor or some estimate of when the
1123   user can expect the request to be fulfilled.
1124</t>
1125</section>
1126
1127<section title="203 Non-Authoritative Information" anchor="status.203">
1128  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1129  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1130<t>
1131   The returned metainformation in the entity-header is not the
1132   definitive set as available from the origin server, but is gathered
1133   from a local or a third-party copy. The set presented &MAY; be a subset
1134   or superset of the original version. For example, including local
1135   annotation information about the resource might result in a superset
1136   of the metainformation known by the origin server. Use of this
1137   response code is not required and is only appropriate when the
1138   response would otherwise be 200 (OK).
1139</t>
1140</section>
1141
1142<section title="204 No Content" anchor="status.204">
1143  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1144  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1145<t>
1146   The server has fulfilled the request but does not need to return an
1147   entity-body, and might want to return updated metainformation. The
1148   response &MAY; include new or updated metainformation in the form of
1149   entity-headers, which if present &SHOULD; be associated with the
1150   requested variant.
1151</t>
1152<t>
1153   If the client is a user agent, it &SHOULD-NOT;  change its document view
1154   from that which caused the request to be sent. This response is
1155   primarily intended to allow input for actions to take place without
1156   causing a change to the user agent's active document view, although
1157   any new or updated metainformation &SHOULD; be applied to the document
1158   currently in the user agent's active view.
1159</t>
1160<t>
1161   The 204 response &MUST-NOT; include a message-body, and thus is always
1162   terminated by the first empty line after the header fields.
1163</t>
1164</section>
1165
1166<section title="205 Reset Content" anchor="status.205">
1167  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1168  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1169<t>
1170   The server has fulfilled the request and the user agent &SHOULD; reset
1171   the document view which caused the request to be sent. This response
1172   is primarily intended to allow input for actions to take place via
1173   user input, followed by a clearing of the form in which the input is
1174   given so that the user can easily initiate another input action. The
1175   response &MUST-NOT; include an entity.
1176</t>
1177</section>
1178
1179<section title="206 Partial Content" anchor="status.206">
1180  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1181  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1182<t>
1183   The server has fulfilled the partial GET request for the resource
1184   and the enclosed entity is a partial representation as defined in &range;.
1185</t>
1186</section>
1187</section>
1188
1189<section title="Redirection 3xx" anchor="status.3xx">
1190<t>
1191   This class of status code indicates that further action needs to be
1192   taken by the user agent in order to fulfill the request.  The action
1193   required &MAY; be carried out by the user agent without interaction
1194   with the user if and only if the method used in the second request is
1195   GET or HEAD. A client &SHOULD; detect infinite redirection loops, since
1196   such loops generate network traffic for each redirection.
1197  <list><t>
1198      <x:h>Note:</x:h> previous versions of this specification recommended a
1199      maximum of five redirections. Content developers should be aware
1200      that there might be clients that implement such a fixed
1201      limitation.
1202  </t></list>
1203</t>
1204
1205<section title="300 Multiple Choices" anchor="status.300">
1206  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1207  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1208<t>
1209   The requested resource corresponds to any one of a set of
1210   representations, each with its own specific location, and agent-driven
1211   negotiation information (&content-negotiation;) is being provided so that
1212   the user (or user agent) can select a preferred representation and
1213   redirect its request to that location.
1214</t>
1215<t>
1216   Unless it was a HEAD request, the response &SHOULD; include an entity
1217   containing a list of resource characteristics and location(s) from
1218   which the user or user agent can choose the one most appropriate. The
1219   entity format is specified by the media type given in the Content-Type
1220   header field. Depending upon the format and the capabilities of
1221   the user agent, selection of the most appropriate choice &MAY; be
1222   performed automatically. However, this specification does not define
1223   any standard for such automatic selection.
1224</t>
1225<t>
1226   If the server has a preferred choice of representation, it &SHOULD;
1227   include the specific URI for that representation in the Location
1228   field; user agents &MAY; use the Location field value for automatic
1229   redirection. This response is cacheable unless indicated otherwise.
1230</t>
1231</section>
1232
1233<section title="301 Moved Permanently" anchor="status.301">
1234  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1235  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1236<t>
1237   The requested resource has been assigned a new permanent URI and any
1238   future references to this resource &SHOULD; use one of the returned
1239   URIs.  Clients with link editing capabilities ought to automatically
1240   re-link references to the Request-URI to one or more of the new
1241   references returned by the server, where possible. This response is
1242   cacheable unless indicated otherwise.
1243</t>
1244<t>
1245   The new permanent URI &SHOULD; be given by the Location field in the
1246   response. Unless the request method was HEAD, the entity of the
1247   response &SHOULD; contain a short hypertext note with a hyperlink to
1248   the new URI(s).
1249</t>
1250<t>
1251   If the 301 status code is received in response to a request method
1252   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1253   then the request &MAY; be automatically redirected by the user agent without
1254   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1255   request unless it can be confirmed by the user, since this might
1256   change the conditions under which the request was issued.
1257  <list><t>
1258      <x:h>Note:</x:h> When automatically redirecting a POST request after
1259      receiving a 301 status code, some existing HTTP/1.0 user agents
1260      will erroneously change it into a GET request.
1261  </t></list>
1262</t>
1263</section>
1264
1265<section title="302 Found" anchor="status.302">
1266  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1267  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1268<t>
1269   The requested resource resides temporarily under a different URI.
1270   Since the redirection might be altered on occasion, the client &SHOULD;
1271   continue to use the Request-URI for future requests.  This response
1272   is only cacheable if indicated by a Cache-Control or Expires header
1273   field.
1274</t>
1275<t>
1276   The temporary URI &SHOULD; be given by the Location field in the
1277   response. Unless the request method was HEAD, the entity of the
1278   response &SHOULD; contain a short hypertext note with a hyperlink to
1279   the new URI(s).
1280</t>
1281<t>
1282   If the 302 status code is received in response to a request method
1283   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1284   then the request &MAY; be automatically redirected by the user agent without
1285   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1286   request unless it can be confirmed by the user, since this might
1287   change the conditions under which the request was issued.
1288  <list><t>
1289      <x:h>Note:</x:h> <xref target="RFC1945"/> and <xref target="RFC2068"/> specify that the client is not allowed
1290      to change the method on the redirected request.  However, most
1291      existing user agent implementations treat 302 as if it were a 303
1292      response, performing a GET on the Location field-value regardless
1293      of the original request method. The status codes 303 and 307 have
1294      been added for servers that wish to make unambiguously clear which
1295      kind of reaction is expected of the client.
1296  </t></list>
1297</t>
1298</section>
1299
1300<section title="303 See Other" anchor="status.303">
1301  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1302  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1303<t>
1304   The server directs the user agent to a different resource, indicated
1305   by a URI in the Location header field, that provides an indirect
1306   response to the original request.  The user agent &MAY; perform a GET
1307   request on the URI in the Location field in order to obtain a
1308   representation corresponding to the response, be redirected again,
1309   or end with an error status.  The Location URI is not a substitute
1310   reference for the originally requested resource.
1311</t>
1312<t>
1313   The 303 status is generally applicable to any HTTP method.  It is
1314   primarily used to allow the output of a POST action to redirect
1315   the user agent to a selected resource, since doing so provides the
1316   information corresponding to the POST response in a form that
1317   can be separately identified, bookmarked, and cached independent
1318   of the original request.
1319</t>
1320<t>
1321   A 303 response to a GET request indicates that the requested
1322   resource does not have a representation of its own that can be
1323   transferred by the server over HTTP.  The Location URI indicates a
1324   resource that is descriptive of the requested resource such that
1325   the follow-on representation may be useful without implying that
1326   it adequately represents the previously requested resource.
1327   Note that answers to the questions of what can be represented, what
1328   representations are adequate, and what might be a useful description
1329   are outside the scope of HTTP and thus entirely determined by the
1330   resource owner(s).
1331</t>
1332<t>
1333   A 303 response &SHOULD-NOT; be cached unless it is indicated as
1334   cacheable by Cache-Control or Expires header fields.  Except for
1335   responses to a HEAD request, the entity of a 303 response &SHOULD;
1336   contain a short hypertext note with a hyperlink to the Location URI.
1337</t>
1338</section>
1339
1340<section title="304 Not Modified" anchor="status.304">
1341  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1342  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1343<t>
1344   The response to the request has not been modified since the conditions
1345   indicated by the client's conditional GET request, as defined in &conditional;.
1346</t>
1347</section>
1348
1349<section title="305 Use Proxy" anchor="status.305">
1350  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1351  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1352<t>
1353   The 305 status was defined in a previous version of this specification
1354   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1355</t>
1356</section>
1357
1358<section title="306 (Unused)" anchor="status.306">
1359  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1360  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1361<t>
1362   The 306 status code was used in a previous version of the
1363   specification, is no longer used, and the code is reserved.
1364</t>
1365</section>
1366
1367<section title="307 Temporary Redirect" anchor="status.307">
1368  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1369  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1370<t>
1371   The requested resource resides temporarily under a different URI.
1372   Since the redirection &MAY; be altered on occasion, the client &SHOULD;
1373   continue to use the Request-URI for future requests.  This response
1374   is only cacheable if indicated by a Cache-Control or Expires header
1375   field.
1376</t>
1377<t>
1378   The temporary URI &SHOULD; be given by the Location field in the
1379   response. Unless the request method was HEAD, the entity of the
1380   response &SHOULD; contain a short hypertext note with a hyperlink to
1381   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1382   understand the 307 status. Therefore, the note &SHOULD; contain the
1383   information necessary for a user to repeat the original request on
1384   the new URI.
1385</t>
1386<t>
1387   If the 307 status code is received in response to a request method
1388   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1389   then the request &MAY; be automatically redirected by the user agent without
1390   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1391   request unless it can be confirmed by the user, since this might
1392   change the conditions under which the request was issued.
1393</t>
1394</section>
1395</section>
1396
1397<section title="Client Error 4xx" anchor="status.4xx">
1398<t>
1399   The 4xx class of status code is intended for cases in which the
1400   client seems to have erred. Except when responding to a HEAD request,
1401   the server &SHOULD; include an entity containing an explanation of the
1402   error situation, and whether it is a temporary or permanent
1403   condition. These status codes are applicable to any request method.
1404   User agents &SHOULD; display any included entity to the user.
1405</t>
1406<t>
1407   If the client is sending data, a server implementation using TCP
1408   &SHOULD; be careful to ensure that the client acknowledges receipt of
1409   the packet(s) containing the response, before the server closes the
1410   input connection. If the client continues sending data to the server
1411   after the close, the server's TCP stack will send a reset packet to
1412   the client, which may erase the client's unacknowledged input buffers
1413   before they can be read and interpreted by the HTTP application.
1414</t>
1415
1416<section title="400 Bad Request" anchor="status.400">
1417  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1418  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1419<t>
1420   The request could not be understood by the server due to malformed
1421   syntax. The client &SHOULD-NOT;  repeat the request without
1422   modifications.
1423</t>
1424</section>
1425
1426<section title="401 Unauthorized" anchor="status.401">
1427  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1428  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1429<t>
1430   The request requires user authentication (see &auth;).
1431</t>
1432</section>
1433
1434<section title="402 Payment Required" anchor="status.402">
1435  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1436  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1437<t>
1438   This code is reserved for future use.
1439</t>
1440</section>
1441
1442<section title="403 Forbidden" anchor="status.403">
1443  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1444  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1445<t>
1446   The server understood the request, but is refusing to fulfill it.
1447   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1448   If the request method was not HEAD and the server wishes to make
1449   public why the request has not been fulfilled, it &SHOULD; describe the
1450   reason for the refusal in the entity.  If the server does not wish to
1451   make this information available to the client, the status code 404
1452   (Not Found) can be used instead.
1453</t>
1454</section>
1455
1456<section title="404 Not Found" anchor="status.404">
1457  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1458  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1459<t>
1460   The server has not found anything matching the Request-URI. No
1461   indication is given of whether the condition is temporary or
1462   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1463   knows, through some internally configurable mechanism, that an old
1464   resource is permanently unavailable and has no forwarding address.
1465   This status code is commonly used when the server does not wish to
1466   reveal exactly why the request has been refused, or when no other
1467   response is applicable.
1468</t>
1469</section>
1470
1471<section title="405 Method Not Allowed" anchor="status.405">
1472  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1473  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1474<t>
1475   The method specified in the Request-Line is not allowed for the
1476   resource identified by the Request-URI. The response &MUST; include an
1477   Allow header containing a list of valid methods for the requested
1478   resource.
1479</t>
1480</section>
1481
1482<section title="406 Not Acceptable" anchor="status.406">
1483  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1484  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1485<t>
1486   The resource identified by the request is only capable of generating
1487   response entities which have content characteristics not acceptable
1488   according to the accept headers sent in the request.
1489</t>
1490<t>
1491   Unless it was a HEAD request, the response &SHOULD; include an entity
1492   containing a list of available entity characteristics and location(s)
1493   from which the user or user agent can choose the one most
1494   appropriate. The entity format is specified by the media type given
1495   in the Content-Type header field. Depending upon the format and the
1496   capabilities of the user agent, selection of the most appropriate
1497   choice &MAY; be performed automatically. However, this specification
1498   does not define any standard for such automatic selection.
1499  <list><t>
1500      <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1501      not acceptable according to the accept headers sent in the
1502      request. In some cases, this may even be preferable to sending a
1503      406 response. User agents are encouraged to inspect the headers of
1504      an incoming response to determine if it is acceptable.
1505  </t></list>
1506</t>
1507<t>
1508   If the response could be unacceptable, a user agent &SHOULD;
1509   temporarily stop receipt of more data and query the user for a
1510   decision on further actions.
1511</t>
1512</section>
1513
1514<section title="407 Proxy Authentication Required" anchor="status.407">
1515  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1516  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1517<t>
1518   This code is similar to 401 (Unauthorized), but indicates that the
1519   client must first authenticate itself with the proxy (see &auth;).
1520</t>
1521</section>
1522
1523<section title="408 Request Timeout" anchor="status.408">
1524  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1525  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1526<t>
1527   The client did not produce a request within the time that the server
1528   was prepared to wait. The client &MAY; repeat the request without
1529   modifications at any later time.
1530</t>
1531</section>
1532
1533<section title="409 Conflict" anchor="status.409">
1534  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1535  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1536<t>
1537   The request could not be completed due to a conflict with the current
1538   state of the resource. This code is only allowed in situations where
1539   it is expected that the user might be able to resolve the conflict
1540   and resubmit the request. The response body &SHOULD; include enough
1541   information for the user to recognize the source of the conflict.
1542   Ideally, the response entity would include enough information for the
1543   user or user agent to fix the problem; however, that might not be
1544   possible and is not required.
1545</t>
1546<t>
1547   Conflicts are most likely to occur in response to a PUT request. For
1548   example, if versioning were being used and the entity being PUT
1549   included changes to a resource which conflict with those made by an
1550   earlier (third-party) request, the server might use the 409 response
1551   to indicate that it can't complete the request. In this case, the
1552   response entity would likely contain a list of the differences
1553   between the two versions in a format defined by the response
1554   Content-Type.
1555</t>
1556</section>
1557
1558<section title="410 Gone" anchor="status.410">
1559  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1560  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1561<t>
1562   The requested resource is no longer available at the server and no
1563   forwarding address is known. This condition is expected to be
1564   considered permanent. Clients with link editing capabilities &SHOULD;
1565   delete references to the Request-URI after user approval. If the
1566   server does not know, or has no facility to determine, whether or not
1567   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1568   used instead. This response is cacheable unless indicated otherwise.
1569</t>
1570<t>
1571   The 410 response is primarily intended to assist the task of web
1572   maintenance by notifying the recipient that the resource is
1573   intentionally unavailable and that the server owners desire that
1574   remote links to that resource be removed. Such an event is common for
1575   limited-time, promotional services and for resources belonging to
1576   individuals no longer working at the server's site. It is not
1577   necessary to mark all permanently unavailable resources as "gone" or
1578   to keep the mark for any length of time -- that is left to the
1579   discretion of the server owner.
1580</t>
1581</section>
1582
1583<section title="411 Length Required" anchor="status.411">
1584  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1585  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1586<t>
1587   The server refuses to accept the request without a defined Content-Length.
1588   The client &MAY; repeat the request if it adds a valid
1589   Content-Length header field containing the length of the message-body
1590   in the request message.
1591</t>
1592</section>
1593
1594<section title="412 Precondition Failed" anchor="status.412">
1595  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1596  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1597<t>
1598   The precondition given in one or more of the request-header fields
1599   evaluated to false when it was tested on the server, as defined in
1600   &conditional;.
1601</t>
1602</section>
1603
1604<section title="413 Request Entity Too Large" anchor="status.413">
1605  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1606  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1607<t>
1608   The server is refusing to process a request because the request
1609   entity is larger than the server is willing or able to process. The
1610   server &MAY; close the connection to prevent the client from continuing
1611   the request.
1612</t>
1613<t>
1614   If the condition is temporary, the server &SHOULD; include a Retry-After
1615   header field to indicate that it is temporary and after what
1616   time the client &MAY; try again.
1617</t>
1618</section>
1619
1620<section title="414 Request-URI Too Long" anchor="status.414">
1621  <iref primary="true" item="414 Request-URI Too Long (status code)" x:for-anchor=""/>
1622  <iref primary="true" item="Status Codes" subitem="414 Request-URI Too Long" x:for-anchor=""/>
1623<t>
1624   The server is refusing to service the request because the Request-URI
1625   is longer than the server is willing to interpret. This rare
1626   condition is only likely to occur when a client has improperly
1627   converted a POST request to a GET request with long query
1628   information, when the client has descended into a URI "black hole" of
1629   redirection (e.g., a redirected URI prefix that points to a suffix of
1630   itself), or when the server is under attack by a client attempting to
1631   exploit security holes present in some servers using fixed-length
1632   buffers for reading or manipulating the Request-URI.
1633</t>
1634</section>
1635
1636<section title="415 Unsupported Media Type" anchor="status.415">
1637  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1638  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1639<t>
1640   The server is refusing to service the request because the entity of
1641   the request is in a format not supported by the requested resource
1642   for the requested method.
1643</t>
1644</section>
1645
1646<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1647  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1648  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1649<t>
1650   The request included a Range request-header field (&header-range;) and none of
1651   the range-specifier values in this field overlap the current extent
1652   of the selected resource.
1653</t>
1654</section>
1655
1656<section title="417 Expectation Failed" anchor="status.417">
1657  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1658  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1659<t>
1660   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1661   could not be met by this server, or, if the server is a proxy,
1662   the server has unambiguous evidence that the request could not be met
1663   by the next-hop server.
1664</t>
1665</section>
1666</section>
1667
1668<section title="Server Error 5xx" anchor="status.5xx">
1669<t>
1670   Response status codes beginning with the digit "5" indicate cases in
1671   which the server is aware that it has erred or is incapable of
1672   performing the request. Except when responding to a HEAD request, the
1673   server &SHOULD; include an entity containing an explanation of the
1674   error situation, and whether it is a temporary or permanent
1675   condition. User agents &SHOULD; display any included entity to the
1676   user. These response codes are applicable to any request method.
1677</t>
1678
1679<section title="500 Internal Server Error" anchor="status.500">
1680  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1681  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1682<t>
1683   The server encountered an unexpected condition which prevented it
1684   from fulfilling the request.
1685</t>
1686</section>
1687
1688<section title="501 Not Implemented" anchor="status.501">
1689  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1690  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1691<t>
1692   The server does not support the functionality required to fulfill the
1693   request. This is the appropriate response when the server does not
1694   recognize the request method and is not capable of supporting it for
1695   any resource.
1696</t>
1697</section>
1698
1699<section title="502 Bad Gateway" anchor="status.502">
1700  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1701  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1702<t>
1703   The server, while acting as a gateway or proxy, received an invalid
1704   response from the upstream server it accessed in attempting to
1705   fulfill the request.
1706</t>
1707</section>
1708
1709<section title="503 Service Unavailable" anchor="status.503">
1710  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1711  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1712<t>
1713   The server is currently unable to handle the request due to a
1714   temporary overloading or maintenance of the server. The implication
1715   is that this is a temporary condition which will be alleviated after
1716   some delay. If known, the length of the delay &MAY; be indicated in a
1717   Retry-After header. If no Retry-After is given, the client &SHOULD;
1718   handle the response as it would for a 500 response.
1719  <list><t>
1720      <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1721      server must use it when becoming overloaded. Some servers may wish
1722      to simply refuse the connection.
1723  </t></list>
1724</t>
1725</section>
1726
1727<section title="504 Gateway Timeout" anchor="status.504">
1728  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1729  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1730<t>
1731   The server, while acting as a gateway or proxy, did not receive a
1732   timely response from the upstream server specified by the URI (e.g.
1733   HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed
1734   to access in attempting to complete the request.
1735  <list><t>
1736      <x:h>Note:</x:h> Note to implementors: some deployed proxies are known to
1737      return 400 or 500 when DNS lookups time out.
1738  </t></list>
1739</t>
1740</section>
1741
1742<section title="505 HTTP Version Not Supported" anchor="status.505">
1743  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1744  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
1745<t>
1746   The server does not support, or refuses to support, the protocol
1747   version that was used in the request message. The server is
1748   indicating that it is unable or unwilling to complete the request
1749   using the same major version as the client, as described in &http-version;,
1750   other than with this error message. The response &SHOULD; contain
1751   an entity describing why that version is not supported and what other
1752   protocols are supported by that server.
1753</t>
1754
1755</section>
1756</section>
1757</section>
1758
1759
1760<section title="Header Field Definitions" anchor="header.fields">
1761<t>
1762   This section defines the syntax and semantics of HTTP/1.1 header fields
1763   related to request and response semantics.
1764</t>
1765<t>
1766   For entity-header fields, both sender and recipient refer to either the
1767   client or the server, depending on who sends and who receives the entity.
1768</t>
1769
1770<section title="Allow" anchor="header.allow">
1771  <iref primary="true" item="Allow header" x:for-anchor=""/>
1772  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
1773  <x:anchor-alias value="Allow"/>
1774<t>
1775      The Allow response-header field lists the set of methods advertised as
1776      supported by the resource identified by the Request-URI. The purpose of
1777      this field is strictly to inform the recipient of valid methods
1778      associated with the resource. An Allow header field &MUST; be
1779      present in a 405 (Method Not Allowed) response.
1780</t>
1781<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/>
1782  <x:ref>Allow</x:ref>   = "Allow" ":" #<x:ref>Method</x:ref>
1783</artwork></figure>
1784<t>
1785      Example of use:
1786</t>
1787<figure><artwork type="example">
1788       Allow: GET, HEAD, PUT
1789</artwork></figure>
1790<t>
1791      The actual set of allowed methods is defined
1792      by the origin server at the time of each request.
1793</t>
1794<t>
1795      A proxy &MUST-NOT; modify the Allow header field even if it does not
1796      understand all the methods specified, since the user agent might
1797      have other means of communicating with the origin server.
1798</t>
1799</section>
1800
1801<section title="Expect" anchor="header.expect">
1802  <iref primary="true" item="Expect header" x:for-anchor=""/>
1803  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
1804  <x:anchor-alias value="Expect"/>
1805  <x:anchor-alias value="expectation"/>
1806  <x:anchor-alias value="expectation-extension"/>
1807  <x:anchor-alias value="expect-params"/>
1808<t>
1809   The Expect request-header field is used to indicate that particular
1810   server behaviors are required by the client.
1811</t>
1812<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"/>
1813  <x:ref>Expect</x:ref>       =  "Expect" ":" 1#<x:ref>expectation</x:ref>
1814 
1815  <x:ref>expectation</x:ref>  =  "100-continue" | <x:ref>expectation-extension</x:ref>
1816  <x:ref>expectation-extension</x:ref> =  <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> | <x:ref>quoted-string</x:ref> )
1817                           *<x:ref>expect-params</x:ref> ]
1818  <x:ref>expect-params</x:ref> =  ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> | <x:ref>quoted-string</x:ref> ) ]
1819</artwork></figure>
1820<t>
1821   A server that does not understand or is unable to comply with any of
1822   the expectation values in the Expect field of a request &MUST; respond
1823   with appropriate error status. The server &MUST; respond with a 417
1824   (Expectation Failed) status if any of the expectations cannot be met
1825   or, if there are other problems with the request, some other 4xx
1826   status.
1827</t>
1828<t>
1829   This header field is defined with extensible syntax to allow for
1830   future extensions. If a server receives a request containing an
1831   Expect field that includes an expectation-extension that it does not
1832   support, it &MUST; respond with a 417 (Expectation Failed) status.
1833</t>
1834<t>
1835   Comparison of expectation values is case-insensitive for unquoted
1836   tokens (including the 100-continue token), and is case-sensitive for
1837   quoted-string expectation-extensions.
1838</t>
1839<t>
1840   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
1841   return a 417 (Expectation Failed) status if it receives a request
1842   with an expectation that it cannot meet. However, the Expect
1843   request-header itself is end-to-end; it &MUST; be forwarded if the
1844   request is forwarded.
1845</t>
1846<t>
1847   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1848   Expect header.
1849</t>
1850<t>
1851   See &use100; for the use of the 100 (Continue) status.
1852</t>
1853</section>
1854
1855<section title="From" anchor="header.from">
1856  <iref primary="true" item="From header" x:for-anchor=""/>
1857  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
1858  <x:anchor-alias value="From"/>
1859  <x:anchor-alias value="mailbox"/>
1860<t>
1861   The From request-header field, if given, &SHOULD; contain an Internet
1862   e-mail address for the human user who controls the requesting user
1863   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
1864   in <xref x:sec="3.4" x:fmt="of" target="RFC2822"/>:
1865</t>
1866<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/>
1867  <x:ref>From</x:ref>    = "From" ":" <x:ref>mailbox</x:ref>
1868 
1869  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC2822"/>&gt;
1870</artwork></figure>
1871<t>
1872   An example is:
1873</t>
1874<figure><artwork type="example">
1875    From: webmaster@example.org
1876</artwork></figure>
1877<t>
1878   This header field &MAY; be used for logging purposes and as a means for
1879   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
1880   be used as an insecure form of access protection. The interpretation
1881   of this field is that the request is being performed on behalf of the
1882   person given, who accepts responsibility for the method performed. In
1883   particular, robot agents &SHOULD; include this header so that the
1884   person responsible for running the robot can be contacted if problems
1885   occur on the receiving end.
1886</t>
1887<t>
1888   The Internet e-mail address in this field &MAY; be separate from the
1889   Internet host which issued the request. For example, when a request
1890   is passed through a proxy the original issuer's address &SHOULD; be
1891   used.
1892</t>
1893<t>
1894   The client &SHOULD-NOT;  send the From header field without the user's
1895   approval, as it might conflict with the user's privacy interests or
1896   their site's security policy. It is strongly recommended that the
1897   user be able to disable, enable, and modify the value of this field
1898   at any time prior to a request.
1899</t>
1900</section>
1901
1902<section title="Location" anchor="header.location">
1903  <iref primary="true" item="Location header" x:for-anchor=""/>
1904  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
1905  <x:anchor-alias value="Location"/>
1906<t>
1907   The Location response-header field is used for the identification of a
1908   new resource or to redirect the recipient to a location other than the
1909   Request-URI for completion of the request.  For 201 (Created)
1910   responses, the Location is that of the new resource which was created
1911   by the request. For 3xx responses, the location &SHOULD; indicate the
1912   server's preferred URI for automatic redirection to the resource. The
1913   field value consists of a single absolute URI.
1914</t>
1915<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/>
1916  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>absoluteURI</x:ref> [ "#" <x:ref>fragment</x:ref> ]
1917</artwork></figure>
1918<t>
1919   An example is:
1920</t>
1921<figure><artwork type="example">
1922    Location: http://www.example.org/pub/WWW/People.html
1923</artwork></figure>
1924<t>
1925  <list><t>
1926      <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
1927      from Location in that the Content-Location identifies the original
1928      location of the entity enclosed in the request. It is therefore
1929      possible for a response to contain header fields for both Location
1930      and Content-Location.
1931  </t></list>
1932</t>
1933<t>
1934   There are circumstances in which a fragment identifier in a Location URL would not be appropriate:
1935   <list style="symbols">
1936      <t>With a 201 Created response, because in this usage the Location header specifies the URL for the entire created resource.</t>
1937      <t>With a 300 Multiple Choices, since the choice decision is intended to be made on resource characteristics and not fragment characteristics.</t>
1938      <t>With 305 Use Proxy.</t>
1939   </list>
1940</t>
1941</section>
1942
1943<section title="Max-Forwards" anchor="header.max-forwards">
1944  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
1945  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
1946  <x:anchor-alias value="Max-Forwards"/>
1947<t>
1948   The Max-Forwards request-header field provides a mechanism with the
1949   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>) methods to limit the
1950   number of proxies or gateways that can forward the request to the
1951   next inbound server. This can be useful when the client is attempting
1952   to trace a request chain which appears to be failing or looping in
1953   mid-chain.
1954</t>
1955<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/>
1956  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" 1*<x:ref>DIGIT</x:ref>
1957</artwork></figure>
1958<t>
1959   The Max-Forwards value is a decimal integer indicating the remaining
1960   number of times this request message may be forwarded.
1961</t>
1962<t>
1963   Each proxy or gateway recipient of a TRACE or OPTIONS request
1964   containing a Max-Forwards header field &MUST; check and update its
1965   value prior to forwarding the request. If the received value is zero
1966   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
1967   respond as the final recipient. If the received Max-Forwards value is
1968   greater than zero, then the forwarded message &MUST; contain an updated
1969   Max-Forwards field with a value decremented by one (1).
1970</t>
1971<t>
1972   The Max-Forwards header field &MAY; be ignored for all other methods
1973   defined by this specification and for any extension methods for which
1974   it is not explicitly referred to as part of that method definition.
1975</t>
1976</section>
1977
1978<section title="Referer" anchor="header.referer">
1979  <iref primary="true" item="Referer header" x:for-anchor=""/>
1980  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
1981  <x:anchor-alias value="Referer"/>
1982<t>
1983   The Referer[sic] request-header field allows the client to specify,
1984   for the server's benefit, the address (URI) of the resource from
1985   which the Request-URI was obtained (the "referrer", although the
1986   header field is misspelled.) The Referer request-header allows a
1987   server to generate lists of back-links to resources for interest,
1988   logging, optimized caching, etc. It also allows obsolete or mistyped
1989   links to be traced for maintenance. The Referer field &MUST-NOT; be
1990   sent if the Request-URI was obtained from a source that does not have
1991   its own URI, such as input from the user keyboard.
1992</t>
1993<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/>
1994  <x:ref>Referer</x:ref>        = "Referer" ":" ( <x:ref>absoluteURI</x:ref> | <x:ref>relativeURI</x:ref> )
1995</artwork></figure>
1996<t>
1997   Example:
1998</t>
1999<figure><artwork type="example">
2000    Referer: http://www.example.org/hypertext/Overview.html
2001</artwork></figure>
2002<t>
2003   If the field value is a relative URI, it &SHOULD; be interpreted
2004   relative to the Request-URI. The URI &MUST-NOT; include a fragment. See
2005   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2006</t>
2007</section>
2008
2009<section title="Retry-After" anchor="header.retry-after">
2010  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2011  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
2012  <x:anchor-alias value="Retry-After"/>
2013<t>
2014   The Retry-After response-header field can be used with a 503 (Service
2015   Unavailable) response to indicate how long the service is expected to
2016   be unavailable to the requesting client. This field &MAY; also be used
2017   with any 3xx (Redirection) response to indicate the minimum time the
2018   user-agent is asked wait before issuing the redirected request. The
2019   value of this field can be either an HTTP-date or an integer number
2020   of seconds (in decimal) after the time of the response.
2021</t>
2022<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/>
2023  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" ( <x:ref>HTTP-date</x:ref> | <x:ref>delta-seconds</x:ref> )
2024</artwork></figure>
2025<t anchor="rule.delta-seconds">
2026  <x:anchor-alias value="delta-seconds"/>
2027   Time spans are non-negative decimal integers, representing time in
2028   seconds.
2029</t>
2030<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2031  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2032</artwork></figure>
2033<t>
2034   Two examples of its use are
2035</t>
2036<figure><artwork type="example">
2037    Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2038    Retry-After: 120
2039</artwork></figure>
2040<t>
2041   In the latter example, the delay is 2 minutes.
2042</t>
2043</section>
2044
2045<section title="Server" anchor="header.server">
2046  <iref primary="true" item="Server header" x:for-anchor=""/>
2047  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
2048  <x:anchor-alias value="Server"/>
2049<t>
2050   The Server response-header field contains information about the
2051   software used by the origin server to handle the request. The field
2052   can contain multiple product tokens (&product-tokens;) and comments
2053   identifying the server and any significant subproducts. The product
2054   tokens are listed in order of their significance for identifying the
2055   application.
2056</t>
2057<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/>
2058  <x:ref>Server</x:ref>         = "Server" ":" 1*( <x:ref>product</x:ref> | <x:ref>comment</x:ref> )
2059</artwork></figure>
2060<t>
2061   Example:
2062</t>
2063<figure><artwork type="example">
2064    Server: CERN/3.0 libwww/2.17
2065</artwork></figure>
2066<t>
2067   If the response is being forwarded through a proxy, the proxy
2068   application &MUST-NOT; modify the Server response-header. Instead, it
2069   &MUST; include a Via field (as described in &header-via;).
2070  <list><t>
2071      <x:h>Note:</x:h> Revealing the specific software version of the server might
2072      allow the server machine to become more vulnerable to attacks
2073      against software that is known to contain security holes. Server
2074      implementors are encouraged to make this field a configurable
2075      option.
2076  </t></list>
2077</t>
2078</section>
2079
2080<section title="User-Agent" anchor="header.user-agent">
2081  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2082  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
2083  <x:anchor-alias value="User-Agent"/>
2084<t>
2085   The User-Agent request-header field contains information about the
2086   user agent originating the request. This is for statistical purposes,
2087   the tracing of protocol violations, and automated recognition of user
2088   agents for the sake of tailoring responses to avoid particular user
2089   agent limitations. User agents &SHOULD; include this field with
2090   requests. The field can contain multiple product tokens (&product-tokens;)
2091   and comments identifying the agent and any subproducts which form a
2092   significant part of the user agent. By convention, the product tokens
2093   are listed in order of their significance for identifying the
2094   application.
2095</t>
2096<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/>
2097  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" 1*( <x:ref>product</x:ref> | <x:ref>comment</x:ref> )
2098</artwork></figure>
2099<t>
2100   Example:
2101</t>
2102<figure><artwork type="example">
2103    User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2104</artwork></figure>
2105</section>
2106
2107</section>
2108
2109<section title="IANA Considerations" anchor="IANA.considerations">
2110
2111<section title="Method Registry" anchor="method.registration">
2112<t>
2113  The registration procedure for HTTP Methods is defined by
2114  <xref target="method.registry"/> of this document.
2115</t>
2116<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2117<!--(START)-->
2118<t xmlns:x="http://purl.org/net/xml2rfc/ext">
2119    The HTTP Method Registry located at <eref target="http://www.iana.org/assignments/http-methods"/>
2120    should be populated with the registrations below:
2121  </t>
2122<texttable xmlns:x="http://purl.org/net/xml2rfc/ext" align="left">
2123   <ttcol>Method</ttcol>
2124   <ttcol>Reference</ttcol>
2125
2126   <c>CONNECT</c>
2127   <c>
2128      <xref target="CONNECT"/>
2129   </c>
2130
2131   <c>DELETE</c>
2132   <c>
2133      <xref target="DELETE"/>
2134   </c>
2135
2136   <c>GET</c>
2137   <c>
2138      <xref target="GET"/>
2139   </c>
2140
2141   <c>HEAD</c>
2142   <c>
2143      <xref target="HEAD"/>
2144   </c>
2145
2146   <c>OPTIONS</c>
2147   <c>
2148      <xref target="OPTIONS"/>
2149   </c>
2150
2151   <c>POST</c>
2152   <c>
2153      <xref target="POST"/>
2154   </c>
2155
2156   <c>PUT</c>
2157   <c>
2158      <xref target="PUT"/>
2159   </c>
2160
2161   <c>TRACE</c>
2162   <c>
2163      <xref target="TRACE"/>
2164   </c>
2165</texttable>
2166<!--(END)-->
2167</section>
2168
2169<section title="Status Code Registry" anchor="status.code.registration">
2170<t>
2171  The registration procedure for HTTP Status Codes -- previously defined
2172  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> -- is now defined
2173  by <xref target="status.code.registry"/> of this document.
2174</t>
2175<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2176<!--(START)-->
2177<t xmlns:x="http://purl.org/net/xml2rfc/ext">
2178    The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2179    should be updated with the registrations below:
2180  </t>
2181<texttable xmlns:x="http://purl.org/net/xml2rfc/ext">
2182   <ttcol>Value</ttcol>
2183   <ttcol>Description</ttcol>
2184   <ttcol>Reference</ttcol>
2185
2186   <c>100</c>
2187   <c>Continue</c>
2188   <c>
2189      <xref target="status.100"/>
2190   </c>
2191
2192   <c>101</c>
2193   <c>Switching Protocols</c>
2194   <c>
2195      <xref target="status.101"/>
2196   </c>
2197
2198   <c>200</c>
2199   <c>OK</c>
2200   <c>
2201      <xref target="status.200"/>
2202   </c>
2203
2204   <c>201</c>
2205   <c>Created</c>
2206   <c>
2207      <xref target="status.201"/>
2208   </c>
2209
2210   <c>202</c>
2211   <c>Accepted</c>
2212   <c>
2213      <xref target="status.202"/>
2214   </c>
2215
2216   <c>203</c>
2217   <c>Non-Authoritative Information</c>
2218   <c>
2219      <xref target="status.203"/>
2220   </c>
2221
2222   <c>204</c>
2223   <c>No Content</c>
2224   <c>
2225      <xref target="status.204"/>
2226   </c>
2227
2228   <c>205</c>
2229   <c>Reset Content</c>
2230   <c>
2231      <xref target="status.205"/>
2232   </c>
2233
2234   <c>206</c>
2235   <c>Partial Content</c>
2236   <c>
2237      <xref target="status.206"/>
2238   </c>
2239
2240   <c>300</c>
2241   <c>Multiple Choices</c>
2242   <c>
2243      <xref target="status.300"/>
2244   </c>
2245
2246   <c>301</c>
2247   <c>Moved Permanently</c>
2248   <c>
2249      <xref target="status.301"/>
2250   </c>
2251
2252   <c>302</c>
2253   <c>Found</c>
2254   <c>
2255      <xref target="status.302"/>
2256   </c>
2257
2258   <c>303</c>
2259   <c>See Other</c>
2260   <c>
2261      <xref target="status.303"/>
2262   </c>
2263
2264   <c>304</c>
2265   <c>Not Modified</c>
2266   <c>
2267      <xref target="status.304"/>
2268   </c>
2269
2270   <c>305</c>
2271   <c>Use Proxy</c>
2272   <c>
2273      <xref target="status.305"/>
2274   </c>
2275
2276   <c>306</c>
2277   <c>(Unused)</c>
2278   <c>
2279      <xref target="status.306"/>
2280   </c>
2281
2282   <c>307</c>
2283   <c>Temporary Redirect</c>
2284   <c>
2285      <xref target="status.307"/>
2286   </c>
2287
2288   <c>400</c>
2289   <c>Bad Request</c>
2290   <c>
2291      <xref target="status.400"/>
2292   </c>
2293
2294   <c>401</c>
2295   <c>Unauthorized</c>
2296   <c>
2297      <xref target="status.401"/>
2298   </c>
2299
2300   <c>402</c>
2301   <c>Payment Required</c>
2302   <c>
2303      <xref target="status.402"/>
2304   </c>
2305
2306   <c>403</c>
2307   <c>Forbidden</c>
2308   <c>
2309      <xref target="status.403"/>
2310   </c>
2311
2312   <c>404</c>
2313   <c>Not Found</c>
2314   <c>
2315      <xref target="status.404"/>
2316   </c>
2317
2318   <c>405</c>
2319   <c>Method Not Allowed</c>
2320   <c>
2321      <xref target="status.405"/>
2322   </c>
2323
2324   <c>406</c>
2325   <c>Not Acceptable</c>
2326   <c>
2327      <xref target="status.406"/>
2328   </c>
2329
2330   <c>407</c>
2331   <c>Proxy Authentication Required</c>
2332   <c>
2333      <xref target="status.407"/>
2334   </c>
2335
2336   <c>408</c>
2337   <c>Request Timeout</c>
2338   <c>
2339      <xref target="status.408"/>
2340   </c>
2341
2342   <c>409</c>
2343   <c>Conflict</c>
2344   <c>
2345      <xref target="status.409"/>
2346   </c>
2347
2348   <c>410</c>
2349   <c>Gone</c>
2350   <c>
2351      <xref target="status.410"/>
2352   </c>
2353
2354   <c>411</c>
2355   <c>Length Required</c>
2356   <c>
2357      <xref target="status.411"/>
2358   </c>
2359
2360   <c>412</c>
2361   <c>Precondition Failed</c>
2362   <c>
2363      <xref target="status.412"/>
2364   </c>
2365
2366   <c>413</c>
2367   <c>Request Entity Too Large</c>
2368   <c>
2369      <xref target="status.413"/>
2370   </c>
2371
2372   <c>414</c>
2373   <c>Request-URI Too Long</c>
2374   <c>
2375      <xref target="status.414"/>
2376   </c>
2377
2378   <c>415</c>
2379   <c>Unsupported Media Type</c>
2380   <c>
2381      <xref target="status.415"/>
2382   </c>
2383
2384   <c>416</c>
2385   <c>Requested Range Not Satisfiable</c>
2386   <c>
2387      <xref target="status.416"/>
2388   </c>
2389
2390   <c>417</c>
2391   <c>Expectation Failed</c>
2392   <c>
2393      <xref target="status.417"/>
2394   </c>
2395
2396   <c>500</c>
2397   <c>Internal Server Error</c>
2398   <c>
2399      <xref target="status.500"/>
2400   </c>
2401
2402   <c>501</c>
2403   <c>Not Implemented</c>
2404   <c>
2405      <xref target="status.501"/>
2406   </c>
2407
2408   <c>502</c>
2409   <c>Bad Gateway</c>
2410   <c>
2411      <xref target="status.502"/>
2412   </c>
2413
2414   <c>503</c>
2415   <c>Service Unavailable</c>
2416   <c>
2417      <xref target="status.503"/>
2418   </c>
2419
2420   <c>504</c>
2421   <c>Gateway Timeout</c>
2422   <c>
2423      <xref target="status.504"/>
2424   </c>
2425
2426   <c>505</c>
2427   <c>HTTP Version Not Supported</c>
2428   <c>
2429      <xref target="status.505"/>
2430   </c>
2431</texttable>
2432<!--(END)-->
2433</section>
2434<section title="Message Header Registration" anchor="message.header.registration">
2435<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2436<!--(START)-->
2437<t>
2438    The Message Header Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> should be updated
2439    with the permanent registrations below (see <xref target="RFC3864"/>):
2440  </t>
2441<texttable>
2442   <ttcol>Header Field Name</ttcol>
2443   <ttcol>Protocol</ttcol>
2444   <ttcol>Status</ttcol>
2445   <ttcol>Reference</ttcol>
2446
2447   <c>Allow</c>
2448   <c>http</c>
2449   <c>standard</c>
2450   <c>
2451      <xref target="header.allow"/>
2452   </c>
2453
2454   <c>Expect</c>
2455   <c>http</c>
2456   <c>standard</c>
2457   <c>
2458      <xref target="header.expect"/>
2459   </c>
2460
2461   <c>From</c>
2462   <c>http</c>
2463   <c>standard</c>
2464   <c>
2465      <xref target="header.from"/>
2466   </c>
2467
2468   <c>Location</c>
2469   <c>http</c>
2470   <c>standard</c>
2471   <c>
2472      <xref target="header.location"/>
2473   </c>
2474
2475   <c>Max-Forwards</c>
2476   <c>http</c>
2477   <c>standard</c>
2478   <c>
2479      <xref target="header.max-forwards"/>
2480   </c>
2481
2482   <c>Referer</c>
2483   <c>http</c>
2484   <c>standard</c>
2485   <c>
2486      <xref target="header.referer"/>
2487   </c>
2488
2489   <c>Retry-After</c>
2490   <c>http</c>
2491   <c>standard</c>
2492   <c>
2493      <xref target="header.retry-after"/>
2494   </c>
2495
2496   <c>Server</c>
2497   <c>http</c>
2498   <c>standard</c>
2499   <c>
2500      <xref target="header.server"/>
2501   </c>
2502
2503   <c>User-Agent</c>
2504   <c>http</c>
2505   <c>standard</c>
2506   <c>
2507      <xref target="header.user-agent"/>
2508   </c>
2509</texttable>
2510<t>
2511    The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2512</t>
2513<!--(END)-->
2514</section>
2515</section>
2516
2517<section title="Security Considerations" anchor="security.considerations">
2518<t>
2519   This section is meant to inform application developers, information
2520   providers, and users of the security limitations in HTTP/1.1 as
2521   described by this document. The discussion does not include
2522   definitive solutions to the problems revealed, though it does make
2523   some suggestions for reducing security risks.
2524</t>
2525
2526<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2527<t>
2528   Like any generic data transfer protocol, HTTP cannot regulate the
2529   content of the data that is transferred, nor is there any a priori
2530   method of determining the sensitivity of any particular piece of
2531   information within the context of any given request. Therefore,
2532   applications &SHOULD; supply as much control over this information as
2533   possible to the provider of that information. Four header fields are
2534   worth special mention in this context: Server, Via, Referer and From.
2535</t>
2536<t>
2537   Revealing the specific software version of the server might allow the
2538   server machine to become more vulnerable to attacks against software
2539   that is known to contain security holes. Implementors &SHOULD; make the
2540   Server header field a configurable option.
2541</t>
2542<t>
2543   Proxies which serve as a portal through a network firewall &SHOULD;
2544   take special precautions regarding the transfer of header information
2545   that identifies the hosts behind the firewall. In particular, they
2546   &SHOULD; remove, or replace with sanitized versions, any Via fields
2547   generated behind the firewall.
2548</t>
2549<t>
2550   The Referer header allows reading patterns to be studied and reverse
2551   links drawn. Although it can be very useful, its power can be abused
2552   if user details are not separated from the information contained in
2553   the Referer. Even when the personal information has been removed, the
2554   Referer header might indicate a private document's URI whose
2555   publication would be inappropriate.
2556</t>
2557<t>
2558   The information sent in the From field might conflict with the user's
2559   privacy interests or their site's security policy, and hence it
2560   &SHOULD-NOT;  be transmitted without the user being able to disable,
2561   enable, and modify the contents of the field. The user &MUST; be able
2562   to set the contents of this field within a user preference or
2563   application defaults configuration.
2564</t>
2565<t>
2566   We suggest, though do not require, that a convenient toggle interface
2567   be provided for the user to enable or disable the sending of From and
2568   Referer information.
2569</t>
2570<t>
2571   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2572   fields can sometimes be used to determine that a specific client or
2573   server have a particular security hole which might be exploited.
2574   Unfortunately, this same information is often used for other valuable
2575   purposes for which HTTP currently has no better mechanism.
2576</t>
2577</section>
2578
2579<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2580<t>
2581   Because the source of a link might be private information or might
2582   reveal an otherwise private information source, it is strongly
2583   recommended that the user be able to select whether or not the
2584   Referer field is sent. For example, a browser client could have a
2585   toggle switch for browsing openly/anonymously, which would
2586   respectively enable/disable the sending of Referer and From
2587   information.
2588</t>
2589<t>
2590   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2591   HTTP request if the referring page was transferred with a secure
2592   protocol.
2593</t>
2594<t>
2595   Authors of services should not use
2596   GET-based forms for the submission of sensitive data because that
2597   data will be encoded in the Request-URI. Many existing
2598   servers, proxies, and user agents log or display the Request-URI in
2599   places where it might be visible to third parties. Such services can
2600   use POST-based form submission instead.
2601</t>
2602</section>
2603
2604<section title="Location Headers and Spoofing" anchor="location.spoofing">
2605<t>
2606   If a single server supports multiple organizations that do not trust
2607   one another, then it &MUST; check the values of Location and Content-Location
2608   headers in responses that are generated under control of
2609   said organizations to make sure that they do not attempt to
2610   invalidate resources over which they have no authority.
2611</t>
2612</section>
2613
2614</section>
2615
2616<section title="Acknowledgments" anchor="ack">
2617</section>
2618</middle>
2619<back>
2620
2621<references title="Normative References">
2622
2623<reference anchor="Part1">
2624  <front>
2625    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2626    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2627      <organization abbrev="Day Software">Day Software</organization>
2628      <address><email>fielding@gbiv.com</email></address>
2629    </author>
2630    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2631      <organization>One Laptop per Child</organization>
2632      <address><email>jg@laptop.org</email></address>
2633    </author>
2634    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2635      <organization abbrev="HP">Hewlett-Packard Company</organization>
2636      <address><email>JeffMogul@acm.org</email></address>
2637    </author>
2638    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2639      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2640      <address><email>henrikn@microsoft.com</email></address>
2641    </author>
2642    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2643      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2644      <address><email>LMM@acm.org</email></address>
2645    </author>
2646    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2647      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2648      <address><email>paulle@microsoft.com</email></address>
2649    </author>
2650    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2651      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2652      <address><email>timbl@w3.org</email></address>
2653    </author>
2654    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2655      <organization abbrev="W3C">World Wide Web Consortium</organization>
2656      <address><email>ylafon@w3.org</email></address>
2657    </author>
2658    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2659      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2660      <address><email>julian.reschke@greenbytes.de</email></address>
2661    </author>
2662    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2663  </front>
2664  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2665  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2666</reference>
2667
2668<reference anchor="Part3">
2669  <front>
2670    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2671    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2672      <organization abbrev="Day Software">Day Software</organization>
2673      <address><email>fielding@gbiv.com</email></address>
2674    </author>
2675    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2676      <organization>One Laptop per Child</organization>
2677      <address><email>jg@laptop.org</email></address>
2678    </author>
2679    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2680      <organization abbrev="HP">Hewlett-Packard Company</organization>
2681      <address><email>JeffMogul@acm.org</email></address>
2682    </author>
2683    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2684      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2685      <address><email>henrikn@microsoft.com</email></address>
2686    </author>
2687    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2688      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2689      <address><email>LMM@acm.org</email></address>
2690    </author>
2691    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2692      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2693      <address><email>paulle@microsoft.com</email></address>
2694    </author>
2695    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2696      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2697      <address><email>timbl@w3.org</email></address>
2698    </author>
2699    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2700      <organization abbrev="W3C">World Wide Web Consortium</organization>
2701      <address><email>ylafon@w3.org</email></address>
2702    </author>
2703    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2704      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2705      <address><email>julian.reschke@greenbytes.de</email></address>
2706    </author>
2707    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2708  </front>
2709  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2710  <x:source href="p3-payload.xml" basename="p3-payload"/>
2711</reference>
2712
2713<reference anchor="Part4">
2714  <front>
2715    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2716    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2717      <organization abbrev="Day Software">Day Software</organization>
2718      <address><email>fielding@gbiv.com</email></address>
2719    </author>
2720    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2721      <organization>One Laptop per Child</organization>
2722      <address><email>jg@laptop.org</email></address>
2723    </author>
2724    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2725      <organization abbrev="HP">Hewlett-Packard Company</organization>
2726      <address><email>JeffMogul@acm.org</email></address>
2727    </author>
2728    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2729      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2730      <address><email>henrikn@microsoft.com</email></address>
2731    </author>
2732    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2733      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2734      <address><email>LMM@acm.org</email></address>
2735    </author>
2736    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2737      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2738      <address><email>paulle@microsoft.com</email></address>
2739    </author>
2740    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2741      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2742      <address><email>timbl@w3.org</email></address>
2743    </author>
2744    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2745      <organization abbrev="W3C">World Wide Web Consortium</organization>
2746      <address><email>ylafon@w3.org</email></address>
2747    </author>
2748    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2749      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2750      <address><email>julian.reschke@greenbytes.de</email></address>
2751    </author>
2752    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2753  </front>
2754  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2755  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2756</reference>
2757
2758<reference anchor="Part5">
2759  <front>
2760    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2761    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2762      <organization abbrev="Day Software">Day Software</organization>
2763      <address><email>fielding@gbiv.com</email></address>
2764    </author>
2765    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2766      <organization>One Laptop per Child</organization>
2767      <address><email>jg@laptop.org</email></address>
2768    </author>
2769    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2770      <organization abbrev="HP">Hewlett-Packard Company</organization>
2771      <address><email>JeffMogul@acm.org</email></address>
2772    </author>
2773    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2774      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2775      <address><email>henrikn@microsoft.com</email></address>
2776    </author>
2777    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2778      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2779      <address><email>LMM@acm.org</email></address>
2780    </author>
2781    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2782      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2783      <address><email>paulle@microsoft.com</email></address>
2784    </author>
2785    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2786      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2787      <address><email>timbl@w3.org</email></address>
2788    </author>
2789    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2790      <organization abbrev="W3C">World Wide Web Consortium</organization>
2791      <address><email>ylafon@w3.org</email></address>
2792    </author>
2793    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2794      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2795      <address><email>julian.reschke@greenbytes.de</email></address>
2796    </author>
2797    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2798  </front>
2799  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
2800  <x:source href="p5-range.xml" basename="p5-range"/>
2801</reference>
2802
2803<reference anchor="Part6">
2804  <front>
2805    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2806    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2807      <organization abbrev="Day Software">Day Software</organization>
2808      <address><email>fielding@gbiv.com</email></address>
2809    </author>
2810    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2811      <organization>One Laptop per Child</organization>
2812      <address><email>jg@laptop.org</email></address>
2813    </author>
2814    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2815      <organization abbrev="HP">Hewlett-Packard Company</organization>
2816      <address><email>JeffMogul@acm.org</email></address>
2817    </author>
2818    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2819      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2820      <address><email>henrikn@microsoft.com</email></address>
2821    </author>
2822    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2823      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2824      <address><email>LMM@acm.org</email></address>
2825    </author>
2826    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2827      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2828      <address><email>paulle@microsoft.com</email></address>
2829    </author>
2830    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2831      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2832      <address><email>timbl@w3.org</email></address>
2833    </author>
2834    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2835      <organization abbrev="W3C">World Wide Web Consortium</organization>
2836      <address><email>ylafon@w3.org</email></address>
2837    </author>
2838    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2839      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2840      <address><email>julian.reschke@greenbytes.de</email></address>
2841    </author>
2842    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2843  </front>
2844  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2845  <x:source href="p6-cache.xml" basename="p6-cache"/>
2846</reference>
2847
2848<reference anchor="Part7">
2849  <front>
2850    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2851    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2852      <organization abbrev="Day Software">Day Software</organization>
2853      <address><email>fielding@gbiv.com</email></address>
2854    </author>
2855    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2856      <organization>One Laptop per Child</organization>
2857      <address><email>jg@laptop.org</email></address>
2858    </author>
2859    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2860      <organization abbrev="HP">Hewlett-Packard Company</organization>
2861      <address><email>JeffMogul@acm.org</email></address>
2862    </author>
2863    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2864      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2865      <address><email>henrikn@microsoft.com</email></address>
2866    </author>
2867    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2868      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2869      <address><email>LMM@acm.org</email></address>
2870    </author>
2871    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2872      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2873      <address><email>paulle@microsoft.com</email></address>
2874    </author>
2875    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2876      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2877      <address><email>timbl@w3.org</email></address>
2878    </author>
2879    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2880      <organization abbrev="W3C">World Wide Web Consortium</organization>
2881      <address><email>ylafon@w3.org</email></address>
2882    </author>
2883    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2884      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2885      <address><email>julian.reschke@greenbytes.de</email></address>
2886    </author>
2887    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2888  </front>
2889  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
2890  <x:source href="p7-auth.xml" basename="p7-auth"/>
2891</reference>
2892
2893<reference anchor="RFC2119">
2894  <front>
2895    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2896    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2897      <organization>Harvard University</organization>
2898      <address><email>sob@harvard.edu</email></address>
2899    </author>
2900    <date month="March" year="1997"/>
2901  </front>
2902  <seriesInfo name="BCP" value="14"/>
2903  <seriesInfo name="RFC" value="2119"/>
2904</reference>
2905
2906</references>
2907
2908<references title="Informative References">
2909
2910<reference anchor="Luo1998">
2911  <front>
2912    <title>Tunneling TCP based protocols through Web proxy servers</title>
2913    <author initials="A." surname="Luotonen" fullname="A. Luotonen">
2914      <organization/>
2915    </author>
2916    <date year="1998" month="August"/>
2917  </front>
2918  <seriesInfo name="Internet-Draft" value="draft-luotonen-web-proxy-tunneling-01"/>
2919</reference>
2920
2921<reference anchor="RFC1945">
2922  <front>
2923    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2924    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2925      <organization>MIT, Laboratory for Computer Science</organization>
2926      <address><email>timbl@w3.org</email></address>
2927    </author>
2928    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2929      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2930      <address><email>fielding@ics.uci.edu</email></address>
2931    </author>
2932    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2933      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2934      <address><email>frystyk@w3.org</email></address>
2935    </author>
2936    <date month="May" year="1996"/>
2937  </front>
2938  <seriesInfo name="RFC" value="1945"/>
2939</reference>
2940
2941<reference anchor="RFC2068">
2942  <front>
2943    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2944    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2945      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2946      <address><email>fielding@ics.uci.edu</email></address>
2947    </author>
2948    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2949      <organization>MIT Laboratory for Computer Science</organization>
2950      <address><email>jg@w3.org</email></address>
2951    </author>
2952    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2953      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2954      <address><email>mogul@wrl.dec.com</email></address>
2955    </author>
2956    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2957      <organization>MIT Laboratory for Computer Science</organization>
2958      <address><email>frystyk@w3.org</email></address>
2959    </author>
2960    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2961      <organization>MIT Laboratory for Computer Science</organization>
2962      <address><email>timbl@w3.org</email></address>
2963    </author>
2964    <date month="January" year="1997"/>
2965  </front>
2966  <seriesInfo name="RFC" value="2068"/>
2967</reference>
2968
2969<reference anchor="RFC2616">
2970  <front>
2971    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2972    <author initials="R." surname="Fielding" fullname="R. Fielding">
2973      <organization>University of California, Irvine</organization>
2974      <address><email>fielding@ics.uci.edu</email></address>
2975    </author>
2976    <author initials="J." surname="Gettys" fullname="J. Gettys">
2977      <organization>W3C</organization>
2978      <address><email>jg@w3.org</email></address>
2979    </author>
2980    <author initials="J." surname="Mogul" fullname="J. Mogul">
2981      <organization>Compaq Computer Corporation</organization>
2982      <address><email>mogul@wrl.dec.com</email></address>
2983    </author>
2984    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2985      <organization>MIT Laboratory for Computer Science</organization>
2986      <address><email>frystyk@w3.org</email></address>
2987    </author>
2988    <author initials="L." surname="Masinter" fullname="L. Masinter">
2989      <organization>Xerox Corporation</organization>
2990      <address><email>masinter@parc.xerox.com</email></address>
2991    </author>
2992    <author initials="P." surname="Leach" fullname="P. Leach">
2993      <organization>Microsoft Corporation</organization>
2994      <address><email>paulle@microsoft.com</email></address>
2995    </author>
2996    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2997      <organization>W3C</organization>
2998      <address><email>timbl@w3.org</email></address>
2999    </author>
3000    <date month="June" year="1999"/>
3001  </front>
3002  <seriesInfo name="RFC" value="2616"/>
3003</reference>
3004
3005<reference anchor='RFC2817'>
3006  <front>
3007    <title>Upgrading to TLS Within HTTP/1.1</title>
3008    <author initials='R.' surname='Khare' fullname='R. Khare'>
3009      <organization>4K Associates / UC Irvine</organization>
3010      <address><email>rohit@4K-associates.com</email></address>
3011    </author>
3012    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3013      <organization>Agranat Systems, Inc.</organization>
3014      <address><email>lawrence@agranat.com</email></address>
3015    </author>
3016    <date year='2000' month='May' />
3017  </front>
3018  <seriesInfo name='RFC' value='2817' />
3019</reference>
3020
3021<reference anchor="RFC2822">
3022  <front>
3023    <title>Internet Message Format</title>
3024    <author initials="P." surname="Resnick" fullname="P. Resnick">
3025      <organization>QUALCOMM Incorporated</organization>
3026    </author>
3027    <date year="2001" month="April"/>
3028  </front> 
3029  <seriesInfo name="RFC" value="2822"/>
3030</reference>
3031
3032<reference anchor='RFC3864'>
3033  <front>
3034    <title>Registration Procedures for Message Header Fields</title>
3035    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3036      <organization>Nine by Nine</organization>
3037      <address><email>GK-IETF@ninebynine.org</email></address>
3038    </author>
3039    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3040      <organization>BEA Systems</organization>
3041      <address><email>mnot@pobox.com</email></address>
3042    </author>
3043    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3044      <organization>HP Labs</organization>
3045      <address><email>JeffMogul@acm.org</email></address>
3046    </author>
3047    <date year='2004' month='September' />
3048  </front>
3049  <seriesInfo name='BCP' value='90' />
3050  <seriesInfo name='RFC' value='3864' />
3051</reference>
3052
3053<reference anchor='RFC5226'>
3054  <front>
3055    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3056    <author initials='T.' surname='Narten' fullname='T. Narten'>
3057      <organization>IBM</organization>
3058      <address><email>narten@us.ibm.com</email></address>
3059    </author>
3060    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3061      <organization>Google</organization>
3062      <address><email>Harald@Alvestrand.no</email></address>
3063    </author>
3064    <date year='2008' month='May' />
3065  </front>
3066  <seriesInfo name='BCP' value='26' />
3067  <seriesInfo name='RFC' value='5226' />
3068</reference>
3069
3070</references>
3071
3072<section title="Compatibility with Previous Versions" anchor="compatibility">
3073<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
3074<t>
3075   Clarified which error code should be used for inbound server failures
3076   (e.g. DNS failures). (<xref target="status.504"/>).
3077</t>
3078<t>
3079   201 (Created) had a race that required an Etag be sent when a resource is
3080   first created. (<xref target="status.201"/>).
3081</t>
3082<t>
3083   Rewrite of message transmission requirements to make it much harder
3084   for implementors to get it wrong, as the consequences of errors here
3085   can have significant impact on the Internet, and to deal with the
3086   following problems:
3087  <list style="numbers">
3088      <t>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
3089         this was incorrectly placing a requirement on the behavior of
3090         an implementation of a future version of HTTP/1.x</t>
3091
3092      <t>Made it clear that user-agents should retry requests, not
3093         "clients" in general.</t>
3094
3095      <t>Converted requirements for clients to ignore unexpected 100
3096         (Continue) responses, and for proxies to forward 100 responses,
3097         into a general requirement for 1xx responses.</t>
3098
3099      <t>Modified some TCP-specific language, to make it clearer that
3100         non-TCP transports are possible for HTTP.</t>
3101
3102      <t>Require that the origin server &MUST-NOT; wait for the request
3103         body before it sends a required 100 (Continue) response.</t>
3104
3105      <t>Allow, rather than require, a server to omit 100 (Continue) if
3106         it has already seen some of the request body.</t>
3107
3108      <t>Allow servers to defend against denial-of-service attacks and
3109         broken clients.</t>
3110  </list>
3111</t>
3112<t>
3113   This change adds the Expect header and 417 status code.
3114</t>
3115<t>
3116   Clean up confusion between 403 and 404 responses. (Section <xref target="status.403" format="counter"/>,
3117   <xref target="status.404" format="counter"/>, and <xref target="status.410" format="counter"/>)
3118</t>
3119<t>
3120   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
3121   implemented in previous versions of this specification. See <xref target="RFC2068" x:fmt="of" x:sec="19.6.1"/>.
3122</t>
3123</section>
3124
3125<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3126<t>
3127  This document takes over the Status Code Registry, previously defined
3128  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3129  (<xref target="status.code.registry"/>)
3130</t>
3131<t>
3132  Clarify definition of POST.
3133  (<xref target="POST"/>)
3134</t>
3135<t>
3136  Failed to consider that there are
3137  many other request methods that are safe to automatically redirect,
3138  and further that the user agent is able to make that determination
3139  based on the request method semantics.
3140  (Sections <xref format="counter" target="status.301"/>,
3141  <xref format="counter" target="status.302"/> and
3142  <xref format="counter" target="status.307"/>)
3143</t>
3144<t>
3145  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3146  It used to indicate that the requested resource must be accessed through the
3147  proxy given by the Location field. The Location field gave the URI of the
3148  proxy. The recipient was expected to repeat this single request via the proxy.
3149  (<xref target="status.305"/>)
3150</t>
3151<t>
3152  Reclassify Allow header as response header, removing the option to
3153  specify it in a PUT request.
3154  Relax the server requirement on the contents of the Allow header and
3155  remove requirement on clients to always trust the header value.
3156  (<xref target="header.allow"/>)
3157</t>
3158<t>
3159  Correct syntax of Location header to allow fragment,
3160  as referred symbol wasn't what was expected, and add some
3161  clarifications as to when it would not be appropriate.
3162  (<xref target="header.location"/>)
3163</t>
3164<t>
3165  In the description of the Server header, the Via field
3166  was described as a SHOULD. The requirement was and is stated
3167  correctly in the description of the Via header in &header-via;.
3168  (<xref target="header.server"/>)
3169</t>
3170</section>
3171
3172</section>
3173
3174<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3175
3176<section title="Since RFC2616">
3177<t>
3178  Extracted relevant partitions from <xref target="RFC2616"/>.
3179</t>
3180</section>
3181
3182<section title="Since draft-ietf-httpbis-p2-semantics-00">
3183<t>
3184  Closed issues:
3185  <list style="symbols"> 
3186    <t>
3187      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3188      "Via is a MUST"
3189      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3190    </t>
3191    <t>
3192      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3193      "Fragments allowed in Location"
3194      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3195    </t>
3196    <t>
3197      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3198      "Safe Methods vs Redirection"
3199      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3200    </t>
3201    <t>
3202      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3203      "Revise description of the POST method"
3204      (<eref target="http://purl.org/NET/http-errata#post"/>)
3205    </t>
3206    <t>
3207      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3208      "Normative and Informative references"
3209    </t>
3210    <t>
3211      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3212      "RFC2606 Compliance"
3213    </t>
3214    <t>
3215      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3216      "Informative references"
3217    </t>
3218    <t>
3219      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3220      "Redundant cross-references"
3221    </t>
3222  </list>
3223</t>
3224<t>
3225  Other changes:
3226  <list style="symbols"> 
3227    <t>
3228      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3229    </t>
3230  </list>
3231</t>
3232</section>
3233
3234<section title="Since draft-ietf-httpbis-p2-semantics-01">
3235<t>
3236  Closed issues:
3237  <list style="symbols"> 
3238    <t>
3239      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3240      "PUT side effects"
3241    </t>
3242    <t>
3243      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3244      "Duplicate Host header requirements"
3245    </t>
3246  </list>
3247</t>
3248<t>
3249  Ongoing work on ABNF conversion (<eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3250  <list style="symbols"> 
3251    <t>
3252      Move "Product Tokens" section (back) into Part 1, as "token" is used
3253      in the definition of the Upgrade header.
3254    </t>
3255    <t>
3256      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3257    </t>
3258    <t>
3259      Copy definition of delta-seconds from Part6 instead of referencing it.
3260    </t>
3261  </list>
3262</t>
3263</section>
3264
3265<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3266<t>
3267  Closed issues:
3268  <list style="symbols"> 
3269    <t>
3270      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3271      "Requiring Allow in 405 responses"
3272    </t>
3273    <t>
3274      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3275      "Status Code Registry"
3276    </t>
3277    <t>
3278      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3279      "Redirection vs. Location"
3280    </t>
3281    <t>
3282      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3283      "Cacheability of 303 response"
3284    </t>
3285    <t>
3286      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3287      "305 Use Proxy"
3288    </t>
3289    <t>
3290      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3291      "Classification for Allow header"
3292    </t>
3293    <t>
3294      <eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3295      "PUT - 'store under' vs 'store at'"
3296    </t>
3297  </list>
3298</t>
3299<t>
3300  Ongoing work on IANA Message Header Registration (<eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3301  <list style="symbols"> 
3302    <t>
3303      Reference RFC 3984, and update header registrations for headers defined
3304      in this document.
3305    </t>
3306  </list>
3307</t>
3308<t>
3309  Ongoing work on ABNF conversion (<eref target="http://www3.tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3310  <list style="symbols"> 
3311    <t>
3312      Replace string literals when the string really is case-sensitive (method).
3313    </t>
3314  </list>
3315</t>
3316</section>
3317
3318<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
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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