source: draft-ietf-httpbis/latest/p2-semantics.xml @ 538

Last change on this file since 538 was 538, checked in by julian.reschke@…, 11 years ago

Move P6 from ./latest-roy to ./latest

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Line 
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 "March">
16  <!ENTITY ID-YEAR "2009">
17  <!ENTITY notation                   "<xref target='Part1' x:rel='#notation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
18  <!ENTITY messaging                  "<xref target='Part1' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
19  <!ENTITY payload                    "<xref target='Part3' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY conditional                "<xref target='Part4' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY range                      "<xref target='Part5' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY caching                    "<xref target='Part6' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23  <!ENTITY auth                       "<xref target='Part7' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
24  <!ENTITY content-negotiation        "<xref target='Part3' x:rel='#content.negotiation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
25  <!ENTITY notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
26  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' 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" x:maturity-level="draft"
77     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
78     xmlns:x='http://purl.org/net/xml2rfc/ext'
79     xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
80<front>
81
82  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
83
84  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
85    <organization abbrev="Day Software">Day Software</organization>
86    <address>
87      <postal>
88        <street>23 Corporate Plaza DR, Suite 280</street>
89        <city>Newport Beach</city>
90        <region>CA</region>
91        <code>92660</code>
92        <country>USA</country>
93      </postal>
94      <phone>+1-949-706-5300</phone>
95      <facsimile>+1-949-706-5305</facsimile>
96      <email>fielding@gbiv.com</email>
97      <uri>http://roy.gbiv.com/</uri>
98    </address>
99  </author>
100
101  <author initials="J." surname="Gettys" fullname="Jim Gettys">
102    <organization>One Laptop per Child</organization>
103    <address>
104      <postal>
105        <street>21 Oak Knoll Road</street>
106        <city>Carlisle</city>
107        <region>MA</region>
108        <code>01741</code>
109        <country>USA</country>
110      </postal>
111      <email>jg@laptop.org</email>
112      <uri>http://www.laptop.org/</uri>
113    </address>
114  </author>
115 
116  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
117    <organization abbrev="HP">Hewlett-Packard Company</organization>
118    <address>
119      <postal>
120        <street>HP Labs, Large Scale Systems Group</street>
121        <street>1501 Page Mill Road, MS 1177</street>
122        <city>Palo Alto</city>
123        <region>CA</region>
124        <code>94304</code>
125        <country>USA</country>
126      </postal>
127      <email>JeffMogul@acm.org</email>
128    </address>
129  </author>
130
131  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
132    <organization abbrev="Microsoft">Microsoft Corporation</organization>
133    <address>
134      <postal>
135        <street>1 Microsoft Way</street>
136        <city>Redmond</city>
137        <region>WA</region>
138        <code>98052</code>
139        <country>USA</country>
140      </postal>
141      <email>henrikn@microsoft.com</email>
142    </address>
143  </author>
144
145  <author initials="L." surname="Masinter" fullname="Larry Masinter">
146    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
147    <address>
148      <postal>
149        <street>345 Park Ave</street>
150        <city>San Jose</city>
151        <region>CA</region>
152        <code>95110</code>
153        <country>USA</country>
154      </postal>
155      <email>LMM@acm.org</email>
156      <uri>http://larry.masinter.net/</uri>
157    </address>
158  </author>
159 
160  <author initials="P." surname="Leach" fullname="Paul J. Leach">
161    <organization abbrev="Microsoft">Microsoft Corporation</organization>
162    <address>
163      <postal>
164        <street>1 Microsoft Way</street>
165        <city>Redmond</city>
166        <region>WA</region>
167        <code>98052</code>
168      </postal>
169      <email>paulle@microsoft.com</email>
170    </address>
171  </author>
172   
173  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
174    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
175    <address>
176      <postal>
177        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
178        <street>The Stata Center, Building 32</street>
179        <street>32 Vassar Street</street>
180        <city>Cambridge</city>
181        <region>MA</region>
182        <code>02139</code>
183        <country>USA</country>
184      </postal>
185      <email>timbl@w3.org</email>
186      <uri>http://www.w3.org/People/Berners-Lee/</uri>
187    </address>
188  </author>
189
190  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
191    <organization abbrev="W3C">World Wide Web Consortium</organization>
192    <address>
193      <postal>
194        <street>W3C / ERCIM</street>
195        <street>2004, rte des Lucioles</street>
196        <city>Sophia-Antipolis</city>
197        <region>AM</region>
198        <code>06902</code>
199        <country>France</country>
200      </postal>
201      <email>ylafon@w3.org</email>
202      <uri>http://www.raubacapeu.net/people/yves/</uri>
203    </address>
204  </author>
205
206  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
207    <organization abbrev="greenbytes">greenbytes GmbH</organization>
208    <address>
209      <postal>
210        <street>Hafenweg 16</street>
211        <city>Muenster</city><region>NW</region><code>48155</code>
212        <country>Germany</country>
213      </postal>
214      <phone>+49 251 2807760</phone>   
215      <facsimile>+49 251 2807761</facsimile>   
216      <email>julian.reschke@greenbytes.de</email>       
217      <uri>http://greenbytes.de/tech/webdav/</uri>     
218    </address>
219  </author>
220
221  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
222  <workgroup>HTTPbis Working Group</workgroup>
223
224<abstract>
225<t>
226   The Hypertext Transfer Protocol (HTTP) is an application-level
227   protocol for distributed, collaborative, hypermedia information
228   systems. HTTP has been in use by the World Wide Web global information
229   initiative since 1990. This document is Part 2 of the seven-part specification
230   that defines the protocol referred to as "HTTP/1.1" and, taken together,
231   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
232   as expressed by request methods, request-header fields, response status codes,
233   and response-header fields.
234</t>
235</abstract>
236
237<note title="Editorial Note (To be removed by RFC Editor)">
238  <t>
239    Discussion of this draft should take place on the HTTPBIS working group
240    mailing list (ietf-http-wg@w3.org). The current issues list is
241    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/11"/>
242    and related documents (including fancy diffs) can be found at
243    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
244  </t>
245  <t>
246    The changes in this draft are summarized in <xref target="changes.since.05"/>.
247  </t>
248</note>
249</front>
250<middle>
251<section title="Introduction" anchor="introduction">
252<t>
253   This document defines HTTP/1.1 request and response semantics.  Each HTTP
254   message, as defined in &messaging;, is in the form of either a request or
255   a response.  An HTTP server listens on a connection for HTTP requests and
256   responds to each request, in the order received on that connection, with
257   one or more HTTP response messages.  This document defines the commonly
258   agreed upon semantics of the HTTP uniform interface, the intentions defined
259   by each request method, and the various response messages that might be
260   expected as a result of applying that method for the requested resource.
261</t>
262<t>
263   This document is currently disorganized in order to minimize the changes
264   between drafts and enable reviewers to see the smaller errata changes.
265   The next draft will reorganize the sections to better reflect the content.
266   In particular, the sections will be ordered according to the typical
267   processing of an HTTP request message (after message parsing): resource
268   mapping, general header fields, methods, request modifiers, response
269   status, and resource metadata.  The current mess reflects how widely
270   dispersed these topics and associated requirements had become in
271   <xref target="RFC2616"/>.
272</t>
273
274<section title="Requirements" anchor="intro.requirements">
275<t>
276   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
277   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
278   document are to be interpreted as described in <xref target="RFC2119"/>.
279</t>
280<t>
281   An implementation is not compliant if it fails to satisfy one or more
282   of the &MUST; or &REQUIRED; level requirements for the protocols it
283   implements. An implementation that satisfies all the &MUST; or &REQUIRED;
284   level and all the &SHOULD; level requirements for its protocols is said
285   to be "unconditionally compliant"; one that satisfies all the &MUST;
286   level requirements but not all the &SHOULD; level requirements for its
287   protocols is said to be "conditionally compliant."
288</t>
289</section>
290
291<section title="Syntax Notation" anchor="notation">
292  <x:anchor-alias value="CR"/>
293  <x:anchor-alias value="DIGIT"/>
294  <x:anchor-alias value="LF"/>
295  <x:anchor-alias value="VCHAR"/>
296  <x:anchor-alias value="WSP"/>
297<t>
298  This specification uses the ABNF syntax defined in &notation;.
299  The following core rules are included by
300  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
301  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
302  DIGIT (decimal 0-9), DQUOTE (double quote),
303  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
304  OCTET (any 8-bit sequence of data), SP (space),
305  VCHAR (any visible USASCII character),
306  and WSP (whitespace).
307</t>
308
309<section title="Core Rules" anchor="core.rules">
310  <x:anchor-alias value="comment"/>
311  <x:anchor-alias value="obs-text"/>
312  <x:anchor-alias value="quoted-string"/>
313  <x:anchor-alias value="token"/>
314  <x:anchor-alias value="OWS"/>
315  <x:anchor-alias value="RWS"/>
316<t>
317  The core rules below are defined in &basic-rules;:
318</t>
319<figure><artwork type="abnf2616">
320  <x:ref>comment</x:ref>       = &lt;comment, defined in &basic-rules;&gt;
321  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
322  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
323  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
324  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
325  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
326</artwork></figure>
327</section>
328
329<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
330  <x:anchor-alias value="absolute-URI"/>
331  <x:anchor-alias value="Accept"/>
332  <x:anchor-alias value="Accept-Charset"/>
333  <x:anchor-alias value="Accept-Encoding"/>
334  <x:anchor-alias value="Accept-Language"/>
335  <x:anchor-alias value="Accept-Ranges"/>
336  <x:anchor-alias value="Age"/>
337  <x:anchor-alias value="Authorization"/>
338  <x:anchor-alias value="ETag"/>
339  <x:anchor-alias value="fragment"/>
340  <x:anchor-alias value="Host"/>
341  <x:anchor-alias value="HTTP-date"/>
342  <x:anchor-alias value="If-Match"/>
343  <x:anchor-alias value="If-Modified-Since"/>
344  <x:anchor-alias value="If-None-Match"/>
345  <x:anchor-alias value="If-Range"/>
346  <x:anchor-alias value="If-Unmodified-Since"/>
347  <x:anchor-alias value="partial-URI"/>
348  <x:anchor-alias value="product"/>
349  <x:anchor-alias value="Proxy-Authenticate"/>
350  <x:anchor-alias value="Proxy-Authorization"/>
351  <x:anchor-alias value="Range"/>
352  <x:anchor-alias value="TE"/>
353  <x:anchor-alias value="Vary"/>
354  <x:anchor-alias value="WWW-Authenticate"/>
355<t>
356  The ABNF rules below are defined in other parts:
357</t>
358<figure><!--Part1--><artwork type="abnf2616">
359  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
360  <x:ref>fragment</x:ref>      = &lt;fragment, defined in &uri;&gt;
361  <x:ref>Host</x:ref>          = &lt;Host, defined in &uri;&gt;
362  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
363  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
364  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
365  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
366</artwork></figure>
367<figure><!--Part3--><artwork type="abnf2616">
368  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
369  <x:ref>Accept-Charset</x:ref> =
370             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
371  <x:ref>Accept-Encoding</x:ref> =
372             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
373  <x:ref>Accept-Language</x:ref> =
374             &lt;Accept-Language, defined in &header-accept-language;&gt;
375</artwork></figure>
376<figure><!--Part4--><artwork type="abnf2616">
377  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
378  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
379  <x:ref>If-Modified-Since</x:ref> =
380             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
381  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
382  <x:ref>If-Unmodified-Since</x:ref> =
383             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
384</artwork></figure>
385<figure><!--Part5--><artwork type="abnf2616">
386  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
387  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
388  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
389</artwork></figure>
390<figure><!--Part6--><artwork type="abnf2616">
391  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
392  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
393</artwork><!--Part7--></figure>
394<figure><artwork type="abnf2616">
395  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
396  <x:ref>Proxy-Authenticate</x:ref> =
397             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
398  <x:ref>Proxy-Authorization</x:ref> =
399             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
400  <x:ref>WWW-Authenticate</x:ref> =
401             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
402</artwork></figure>
403</section>
404</section>
405</section>
406
407<section title="Method" anchor="method">
408  <x:anchor-alias value="Method"/>
409  <x:anchor-alias value="extension-method"/>
410<t>
411   The Method  token indicates the method to be performed on the
412   resource identified by the request-target. The method is case-sensitive.
413</t>
414<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
415  <x:ref>Method</x:ref>         = <x:abnf-char-sequence>"OPTIONS"</x:abnf-char-sequence>   ; "OPTIONS", <xref target="OPTIONS"/>
416                 / <x:abnf-char-sequence>"GET"</x:abnf-char-sequence>               ; "GET", <xref target="GET"/>
417                 / <x:abnf-char-sequence>"HEAD"</x:abnf-char-sequence>            ; "HEAD", <xref target="HEAD"/>
418                 / <x:abnf-char-sequence>"POST"</x:abnf-char-sequence>            ; "POST", <xref target="POST"/>
419                 / <x:abnf-char-sequence>"PUT"</x:abnf-char-sequence>               ; "PUT", <xref target="PUT"/>
420                 / <x:abnf-char-sequence>"DELETE"</x:abnf-char-sequence>      ; "DELETE", <xref target="DELETE"/>
421                 / <x:abnf-char-sequence>"TRACE"</x:abnf-char-sequence>         ; "TRACE", <xref target="TRACE"/>
422                 / <x:abnf-char-sequence>"CONNECT"</x:abnf-char-sequence>   ; "CONNECT", <xref target="CONNECT"/>
423                 / <x:ref>extension-method</x:ref>
424  <x:ref>extension-method</x:ref> = <x:ref>token</x:ref>
425</artwork></figure>
426<t>
427   The list of methods allowed by a resource can be specified in an
428   Allow header field (<xref target="header.allow"/>). The return code of the response
429   always notifies the client whether a method is currently allowed on a
430   resource, since the set of allowed methods can change dynamically. An
431   origin server &SHOULD; return the status code 405 (Method Not Allowed)
432   if the method is known by the origin server but not allowed for the
433   requested resource, and 501 (Not Implemented) if the method is
434   unrecognized or not implemented by the origin server. The methods GET
435   and HEAD &MUST; be supported by all general-purpose servers. All other
436   methods are &OPTIONAL;; however, if the above methods are implemented,
437   they &MUST; be implemented with the same semantics as those specified
438   in <xref target="method.definitions"/>.
439</t>
440
441<section title="Method Registry" anchor="method.registry">
442<t>
443  The HTTP Method Registry defines the name space for the Method token in the
444  Request line of an HTTP request.
445</t>
446<t>
447  Registrations &MUST; include the following fields:
448  <list style="symbols">
449    <t>Method Name (see <xref target="method"/>)</t>
450    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
451    <t>Pointer to specification text</t>
452  </list>
453</t>
454<t>
455  Values to be added to this name space are subject to IETF review
456  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
457  new method names should be traceable through statuses of either 'Obsoletes'
458  or 'Updates' to this document.
459</t>
460<t>
461  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
462</t>
463</section>
464</section>
465
466<section title="Request Header Fields" anchor="request.header.fields">
467  <x:anchor-alias value="request-header"/>
468<t>
469   The request-header fields allow the client to pass additional
470   information about the request, and about the client itself, to the
471   server. These fields act as request modifiers, with semantics
472   equivalent to the parameters on a programming language method
473   invocation.
474</t>
475<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
476  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
477                 / <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
478                 / <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
479                 / <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
480                 / <x:ref>Authorization</x:ref>            ; &header-authorization;
481                 / <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
482                 / <x:ref>From</x:ref>                     ; <xref target="header.from"/>
483                 / <x:ref>Host</x:ref>                     ; &header-host;
484                 / <x:ref>If-Match</x:ref>                 ; &header-if-match;
485                 / <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
486                 / <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
487                 / <x:ref>If-Range</x:ref>                 ; &header-if-range;
488                 / <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
489                 / <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
490                 / <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
491                 / <x:ref>Range</x:ref>                    ; &header-range;
492                 / <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
493                 / <x:ref>TE</x:ref>                       ; &header-te;
494                 / <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
495</artwork></figure>
496<t>
497   Request-header field names can be extended reliably only in
498   combination with a change in the protocol version. However, new or
499   experimental header fields &MAY; be given the semantics of request-header
500   fields if all parties in the communication recognize them to
501   be request-header fields. Unrecognized header fields are treated as
502   entity-header fields.
503</t>
504</section>
505
506<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
507  <x:anchor-alias value="Reason-Phrase"/>
508  <x:anchor-alias value="Status-Code"/>
509  <x:anchor-alias value="extension-code"/>
510<t>
511   The Status-Code element is a 3-digit integer result code of the
512   attempt to understand and satisfy the request. The status codes listed
513   below are defined in <xref target="status.codes"/>.
514   The Reason-Phrase is intended to give a short
515   textual description of the Status-Code. The Status-Code is intended
516   for use by automata and the Reason-Phrase is intended for the human
517   user. The client is not required to examine or display the Reason-Phrase.
518</t>
519<t> 
520   The individual values of the numeric status codes defined for
521   HTTP/1.1, and an example set of corresponding Reason-Phrase's, are
522   presented below. The reason phrases listed here are only
523   recommendations -- they &MAY; be replaced by local equivalents without
524   affecting the protocol.
525</t>
526<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"/>
527  <x:ref>Status-Code</x:ref>    =
528         "100"  ; <xref target="status.100"/>: Continue
529       / "101"  ; <xref target="status.101"/>: Switching Protocols
530       / "200"  ; <xref target="status.200"/>: OK
531       / "201"  ; <xref target="status.201"/>: Created
532       / "202"  ; <xref target="status.202"/>: Accepted
533       / "203"  ; <xref target="status.203"/>: Non-Authoritative Information
534       / "204"  ; <xref target="status.204"/>: No Content
535       / "205"  ; <xref target="status.205"/>: Reset Content
536       / "206"  ; <xref target="status.206"/>: Partial Content
537       / "300"  ; <xref target="status.300"/>: Multiple Choices
538       / "301"  ; <xref target="status.301"/>: Moved Permanently
539       / "302"  ; <xref target="status.302"/>: Found
540       / "303"  ; <xref target="status.303"/>: See Other
541       / "304"  ; <xref target="status.304"/>: Not Modified
542       / "305"  ; <xref target="status.305"/>: Use Proxy
543       / "307"  ; <xref target="status.307"/>: Temporary Redirect
544       / "400"  ; <xref target="status.400"/>: Bad Request
545       / "401"  ; <xref target="status.401"/>: Unauthorized
546       / "402"  ; <xref target="status.402"/>: Payment Required
547       / "403"  ; <xref target="status.403"/>: Forbidden
548       / "404"  ; <xref target="status.404"/>: Not Found
549       / "405"  ; <xref target="status.405"/>: Method Not Allowed
550       / "406"  ; <xref target="status.406"/>: Not Acceptable
551       / "407"  ; <xref target="status.407"/>: Proxy Authentication Required
552       / "408"  ; <xref target="status.408"/>: Request Time-out
553       / "409"  ; <xref target="status.409"/>: Conflict
554       / "410"  ; <xref target="status.410"/>: Gone
555       / "411"  ; <xref target="status.411"/>: Length Required
556       / "412"  ; <xref target="status.412"/>: Precondition Failed
557       / "413"  ; <xref target="status.413"/>: Request Entity Too Large
558       / "414"  ; <xref target="status.414"/>: URI Too Long
559       / "415"  ; <xref target="status.415"/>: Unsupported Media Type
560       / "416"  ; <xref target="status.416"/>: Requested range not satisfiable
561       / "417"  ; <xref target="status.417"/>: Expectation Failed
562       / "500"  ; <xref target="status.500"/>: Internal Server Error
563       / "501"  ; <xref target="status.501"/>: Not Implemented
564       / "502"  ; <xref target="status.502"/>: Bad Gateway
565       / "503"  ; <xref target="status.503"/>: Service Unavailable
566       / "504"  ; <xref target="status.504"/>: Gateway Time-out
567       / "505"  ; <xref target="status.505"/>: HTTP Version not supported
568       / <x:ref>extension-code</x:ref>
569
570  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
571  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
572</artwork></figure>
573<t>
574   HTTP status codes are extensible. HTTP applications are not required
575   to understand the meaning of all registered status codes, though such
576   understanding is obviously desirable. However, applications &MUST;
577   understand the class of any status code, as indicated by the first
578   digit, and treat any unrecognized response as being equivalent to the
579   x00 status code of that class, with the exception that an
580   unrecognized response &MUST-NOT; be cached. For example, if an
581   unrecognized status code of 431 is received by the client, it can
582   safely assume that there was something wrong with its request and
583   treat the response as if it had received a 400 status code. In such
584   cases, user agents &SHOULD; present to the user the entity returned
585   with the response, since that entity is likely to include human-readable
586   information which will explain the unusual status.
587</t>
588
589<section title="Status Code Registry" anchor="status.code.registry">
590<t>
591  The HTTP Status Code Registry defines the name space for the Status-Code
592  token in the Status line of an HTTP response.
593</t>
594<t>
595  Values to be added to this name space are subject to IETF review
596  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
597  new status codes should be traceable through statuses of either 'Obsoletes'
598  or 'Updates' to this document.
599</t>
600<t>
601  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
602</t>
603</section>
604
605</section>
606
607<section title="Response Header Fields" anchor="response.header.fields">
608  <x:anchor-alias value="response-header"/>
609<t>
610   The response-header fields allow the server to pass additional
611   information about the response which cannot be placed in the Status-Line.
612   These header fields give information about the server and about
613   further access to the resource identified by the request-target.
614</t>
615<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
616  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
617                  / <x:ref>Age</x:ref>                     ; &header-age;
618                  / <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
619                  / <x:ref>ETag</x:ref>                    ; &header-etag;
620                  / <x:ref>Location</x:ref>                ; <xref target="header.location"/>
621                  / <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
622                  / <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
623                  / <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
624                  / <x:ref>Vary</x:ref>                    ; &header-vary;
625                  / <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
626</artwork></figure>
627<t>
628   Response-header field names can be extended reliably only in
629   combination with a change in the protocol version. However, new or
630   experimental header fields &MAY; be given the semantics of response-header
631   fields if all parties in the communication recognize them to
632   be response-header fields. Unrecognized header fields are treated as
633   entity-header fields.
634</t>
635</section>
636
637<section title="Entity" anchor="entity">
638<t>
639   Request and Response messages &MAY; transfer an entity if not otherwise
640   restricted by the request method or response status code. An entity
641   consists of entity-header fields and an entity-body, although some
642   responses will only include the entity-headers. HTTP entity-body and
643   entity-header fields are defined in &payload;.
644</t>
645<t>
646   An entity-body is only present in a message when a message-body is
647   present, as described in &message-body;. The entity-body is obtained
648   from the message-body by decoding any Transfer-Encoding that might
649   have been applied to ensure safe and proper transfer of the message.
650</t>
651</section>
652
653
654<section title="Method Definitions" anchor="method.definitions">
655<t>
656   The set of common methods for HTTP/1.1 is defined below. Although
657   this set can be expanded, additional methods cannot be assumed to
658   share the same semantics for separately extended clients and servers.
659</t>
660
661<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
662
663<section title="Safe Methods" anchor="safe.methods">
664<iref item="Safe Methods" primary="true"/>
665<t>
666   Implementors should be aware that the software represents the user in
667   their interactions over the Internet, and should be careful to allow
668   the user to be aware of any actions they might take which may have an
669   unexpected significance to themselves or others.
670</t>
671<t>
672   In particular, the convention has been established that the GET and
673   HEAD methods &SHOULD-NOT;  have the significance of taking an action
674   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
675   This allows user agents to represent other methods, such as POST, PUT
676   and DELETE, in a special way, so that the user is made aware of the
677   fact that a possibly unsafe action is being requested.
678</t>
679<t>
680   Naturally, it is not possible to ensure that the server does not
681   generate side-effects as a result of performing a GET request; in
682   fact, some dynamic resources consider that a feature. The important
683   distinction here is that the user did not request the side-effects,
684   so therefore cannot be held accountable for them.
685</t>
686</section>
687
688<section title="Idempotent Methods" anchor="idempotent.methods">
689<iref item="Idempotent Methods" primary="true"/>
690<t>
691   Methods can also have the property of "idempotence" in that (aside
692   from error or expiration issues) the side-effects of N &gt; 0 identical
693   requests is the same as for a single request. The methods GET, HEAD,
694   PUT and DELETE share this property. Also, the methods OPTIONS and
695   TRACE &SHOULD-NOT;  have side effects, and so are inherently idempotent.
696</t>
697<t>
698   However, it is possible that a sequence of several requests is non-idempotent,
699   even if all of the methods executed in that sequence are
700   idempotent. (A sequence is idempotent if a single execution of the
701   entire sequence always yields a result that is not changed by a
702   reexecution of all, or part, of that sequence.) For example, a
703   sequence is non-idempotent if its result depends on a value that is
704   later modified in the same sequence.
705</t>
706<t>
707   A sequence that never has side effects is idempotent, by definition
708   (provided that no concurrent operations are being executed on the
709   same set of resources).
710</t>
711</section>
712</section>
713
714<section title="OPTIONS" anchor="OPTIONS">
715  <rdf:Description>
716    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
717  </rdf:Description>
718  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
719  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
720<t>
721   The OPTIONS method represents a request for information about the
722   communication options available on the request/response chain
723   identified by the request-target. This method allows the client to
724   determine the options and/or requirements associated with a resource,
725   or the capabilities of a server, without implying a resource action
726   or initiating a resource retrieval.
727</t>
728<t>
729   Responses to this method are not cacheable.
730</t>
731<t>
732   If the OPTIONS request includes an entity-body (as indicated by the
733   presence of Content-Length or Transfer-Encoding), then the media type
734   &MUST; be indicated by a Content-Type field. Although this
735   specification does not define any use for such a body, future
736   extensions to HTTP might use the OPTIONS body to make more detailed
737   queries on the server.
738</t>
739<t>
740   If the request-target is an asterisk ("*"), the OPTIONS request is
741   intended to apply to the server in general rather than to a specific
742   resource. Since a server's communication options typically depend on
743   the resource, the "*" request is only useful as a "ping" or "no-op"
744   type of method; it does nothing beyond allowing the client to test
745   the capabilities of the server. For example, this can be used to test
746   a proxy for HTTP/1.1 compliance (or lack thereof).
747</t>
748<t>
749   If the request-target is not an asterisk, the OPTIONS request applies
750   only to the options that are available when communicating with that
751   resource.
752</t>
753<t>
754   A 200 response &SHOULD; include any header fields that indicate
755   optional features implemented by the server and applicable to that
756   resource (e.g., Allow), possibly including extensions not defined by
757   this specification. The response body, if any, &SHOULD; also include
758   information about the communication options. The format for such a
759   body is not defined by this specification, but might be defined by
760   future extensions to HTTP. Content negotiation &MAY; be used to select
761   the appropriate response format. If no response body is included, the
762   response &MUST; include a Content-Length field with a field-value of
763   "0".
764</t>
765<t>
766   The Max-Forwards request-header field &MAY; be used to target a
767   specific proxy in the request chain. When a proxy receives an OPTIONS
768   request on an absolute-URI for which request forwarding is permitted,
769   the proxy &MUST; check for a Max-Forwards field. If the Max-Forwards
770   field-value is zero ("0"), the proxy &MUST-NOT; forward the message;
771   instead, the proxy &SHOULD; respond with its own communication options.
772   If the Max-Forwards field-value is an integer greater than zero, the
773   proxy &MUST; decrement the field-value when it forwards the request. If
774   no Max-Forwards field is present in the request, then the forwarded
775   request &MUST-NOT; include a Max-Forwards field.
776</t>
777</section>
778
779<section title="GET" anchor="GET">
780  <rdf:Description>
781    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
782  </rdf:Description>
783  <iref primary="true" item="GET method" x:for-anchor=""/>
784  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
785<t>
786   The GET method means retrieve whatever information (in the form of an
787   entity) is identified by the request-target. If the request-target refers
788   to a data-producing process, it is the produced data which shall be
789   returned as the entity in the response and not the source text of the
790   process, unless that text happens to be the output of the process.
791</t>
792<t>
793   The semantics of the GET method change to a "conditional GET" if the
794   request message includes an If-Modified-Since, If-Unmodified-Since,
795   If-Match, If-None-Match, or If-Range header field. A conditional GET
796   method requests that the entity be transferred only under the
797   circumstances described by the conditional header field(s). The
798   conditional GET method is intended to reduce unnecessary network
799   usage by allowing cached entities to be refreshed without requiring
800   multiple requests or transferring data already held by the client.
801</t>
802<t>
803   The semantics of the GET method change to a "partial GET" if the
804   request message includes a Range header field. A partial GET requests
805   that only part of the entity be transferred, as described in &header-range;.
806   The partial GET method is intended to reduce unnecessary
807   network usage by allowing partially-retrieved entities to be
808   completed without transferring data already held by the client.
809</t>
810<t>
811   The response to a GET request is cacheable if and only if it meets
812   the requirements for HTTP caching described in &caching;.
813</t>
814<t>
815   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
816</t>
817</section>
818
819<section title="HEAD" anchor="HEAD">
820  <rdf:Description>
821    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
822  </rdf:Description>
823  <iref primary="true" item="HEAD method" x:for-anchor=""/>
824  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
825<t>
826   The HEAD method is identical to GET except that the server &MUST-NOT;
827   return a message-body in the response. The metainformation contained
828   in the HTTP headers in response to a HEAD request &SHOULD; be identical
829   to the information sent in response to a GET request. This method can
830   be used for obtaining metainformation about the entity implied by the
831   request without transferring the entity-body itself. This method is
832   often used for testing hypertext links for validity, accessibility,
833   and recent modification.
834</t>
835<t>
836   The response to a HEAD request &MAY; be cacheable in the sense that the
837   information contained in the response &MAY; be used to update a
838   previously cached entity from that resource. If the new field values
839   indicate that the cached entity differs from the current entity (as
840   would be indicated by a change in Content-Length, Content-MD5, ETag
841   or Last-Modified), then the cache &MUST; treat the cache entry as
842   stale.
843</t>
844</section>
845
846<section title="POST" anchor="POST">
847  <iref primary="true" item="POST method" x:for-anchor=""/>
848  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
849<t>
850   The POST method is used to request that the origin server accept the
851   entity enclosed in the request as data to be processed by the resource
852   identified by the request-target in the Request-Line. POST is designed
853   to allow a uniform method to cover the following functions:
854  <list style="symbols">
855    <t>
856      Annotation of existing resources;
857    </t>
858    <t>
859        Posting a message to a bulletin board, newsgroup, mailing list,
860        or similar group of articles;
861    </t>
862    <t>
863        Providing a block of data, such as the result of submitting a
864        form, to a data-handling process;
865    </t>
866    <t>
867        Extending a database through an append operation.
868    </t>
869  </list>
870</t>
871<t>
872   The actual function performed by the POST method is determined by the
873   server and is usually dependent on the request-target.
874</t>
875<t>
876   The action performed by the POST method might not result in a
877   resource that can be identified by a URI. In this case, either 200
878   (OK) or 204 (No Content) is the appropriate response status,
879   depending on whether or not the response includes an entity that
880   describes the result.
881</t>
882<t>
883   If a resource has been created on the origin server, the response
884   &SHOULD; be 201 (Created) and contain an entity which describes the
885   status of the request and refers to the new resource, and a Location
886   header (see <xref target="header.location"/>).
887</t>
888<t>
889   Responses to this method are not cacheable, unless the response
890   includes appropriate Cache-Control or Expires header fields. However,
891   the 303 (See Other) response can be used to direct the user agent to
892   retrieve a cacheable resource.
893</t>
894</section>
895
896<section title="PUT" anchor="PUT">
897  <iref primary="true" item="PUT method" x:for-anchor=""/>
898  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
899<t>
900   The PUT method requests that the enclosed entity be stored at the
901   supplied request-target. If the request-target refers to an already
902   existing resource, the enclosed entity &SHOULD; be considered as a
903   modified version of the one residing on the origin server. If the
904   request-target does not point to an existing resource, and that URI is
905   capable of being defined as a new resource by the requesting user
906   agent, the origin server can create the resource with that URI. If a
907   new resource is created at the request-target, the origin server &MUST;
908         inform the user agent
909   via the 201 (Created) response. If an existing resource is modified,
910   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
911   to indicate successful completion of the request. If the resource
912   could not be created or modified with the request-target, an appropriate
913   error response &SHOULD; be given that reflects the nature of the
914   problem. The recipient of the entity &MUST-NOT; ignore any Content-*
915   headers (headers starting with the prefix 'Content-') that it does
916   not understand or implement
917   and &MUST; return a 501 (Not Implemented) response in such cases.
918</t>
919<t>
920   If the request passes through a cache and the request-target identifies
921   one or more currently cached entities, those entries &SHOULD; be
922   treated as stale. Responses to this method are not cacheable.
923</t>
924<t>
925   The fundamental difference between the POST and PUT requests is
926   reflected in the different meaning of the request-target. The URI in a
927   POST request identifies the resource that will handle the enclosed
928   entity. That resource might be a data-accepting process, a gateway to
929   some other protocol, or a separate entity that accepts annotations.
930   In contrast, the URI in a PUT request identifies the entity enclosed
931   with the request -- the user agent knows what URI is intended and the
932   server &MUST-NOT; attempt to apply the request to some other resource.
933   If the server desires that the request be applied to a different URI,
934   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
935   then make its own decision regarding whether or not to redirect the
936   request.
937</t>
938<t>
939   A single resource &MAY; be identified by many different URIs. For
940   example, an article might have a URI for identifying "the current
941   version" which is separate from the URI identifying each particular
942   version. In this case, a PUT request on a general URI might result in
943   several other URIs being defined by the origin server.
944</t>
945<t>
946   HTTP/1.1 does not define how a PUT method affects the state of an
947   origin server.
948</t>
949<t>
950   Unless otherwise specified for a particular entity-header, the
951   entity-headers in the PUT request &SHOULD; be applied to the resource
952   created or modified by the PUT.
953</t>
954</section>
955
956<section title="DELETE" anchor="DELETE">
957  <iref primary="true" item="DELETE method" x:for-anchor=""/>
958  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
959<t>
960   The DELETE method requests that the origin server delete the resource
961   identified by the request-target. This method &MAY; be overridden by human
962   intervention (or other means) on the origin server. The client cannot
963   be guaranteed that the operation has been carried out, even if the
964   status code returned from the origin server indicates that the action
965   has been completed successfully. However, the server &SHOULD-NOT; 
966   indicate success unless, at the time the response is given, it
967   intends to delete the resource or move it to an inaccessible
968   location.
969</t>
970<t>
971   A successful response &SHOULD; be 200 (OK) if the response includes an
972   entity describing the status, 202 (Accepted) if the action has not
973   yet been enacted, or 204 (No Content) if the action has been enacted
974   but the response does not include an entity.
975</t>
976<t>
977   If the request passes through a cache and the request-target identifies
978   one or more currently cached entities, those entries &SHOULD; be
979   treated as stale. Responses to this method are not cacheable.
980</t>
981</section>
982
983<section title="TRACE" anchor="TRACE">
984  <rdf:Description>
985    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
986  </rdf:Description>
987  <iref primary="true" item="TRACE method" x:for-anchor=""/>
988  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
989<t>
990   The TRACE method is used to invoke a remote, application-layer loop-back
991   of the request message. The final recipient of the request
992   &SHOULD; reflect the message received back to the client as the
993   entity-body of a 200 (OK) response. The final recipient is either the
994   origin server or the first proxy or gateway to receive a Max-Forwards
995   value of zero (0) in the request (see <xref target="header.max-forwards"/>). A TRACE request
996   &MUST-NOT; include an entity.
997</t>
998<t>
999   TRACE allows the client to see what is being received at the other
1000   end of the request chain and use that data for testing or diagnostic
1001   information. The value of the Via header field (&header-via;) is of
1002   particular interest, since it acts as a trace of the request chain.
1003   Use of the Max-Forwards header field allows the client to limit the
1004   length of the request chain, which is useful for testing a chain of
1005   proxies forwarding messages in an infinite loop.
1006</t>
1007<t>
1008   If the request is valid, the response &SHOULD; contain the entire
1009   request message in the entity-body, with a Content-Type of
1010   "message/http" (see &media-type-message-http;). Responses to this method
1011   &MUST-NOT; be cached.
1012</t>
1013</section>
1014
1015<section title="CONNECT" anchor="CONNECT">
1016  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1017  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1018<t>
1019   This specification reserves the method name CONNECT for use with a
1020   proxy that can dynamically switch to being a tunnel (e.g. SSL
1021   tunneling <xref target="RFC2817"/>).
1022</t>
1023</section>
1024</section>
1025
1026
1027<section title="Status Code Definitions" anchor="status.codes">
1028<t>
1029   Each Status-Code is described below, including a description of which
1030   method(s) it can follow and any metainformation required in the
1031   response.
1032</t>
1033
1034<section title="Informational 1xx" anchor="status.1xx">
1035<t>
1036   This class of status code indicates a provisional response,
1037   consisting only of the Status-Line and optional headers, and is
1038   terminated by an empty line. There are no required headers for this
1039   class of status code. Since HTTP/1.0 did not define any 1xx status
1040   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1041   except under experimental conditions.
1042</t>
1043<t>
1044   A client &MUST; be prepared to accept one or more 1xx status responses
1045   prior to a regular response, even if the client does not expect a 100
1046   (Continue) status message. Unexpected 1xx status responses &MAY; be
1047   ignored by a user agent.
1048</t>
1049<t>
1050   Proxies &MUST; forward 1xx responses, unless the connection between the
1051   proxy and its client has been closed, or unless the proxy itself
1052   requested the generation of the 1xx response. (For example, if a
1053   proxy adds a "Expect: 100-continue" field when it forwards a request,
1054   then it need not forward the corresponding 100 (Continue)
1055   response(s).)
1056</t>
1057
1058<section title="100 Continue" anchor="status.100">
1059  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1060  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1061<t>
1062   The client &SHOULD; continue with its request. This interim response is
1063   used to inform the client that the initial part of the request has
1064   been received and has not yet been rejected by the server. The client
1065   &SHOULD; continue by sending the remainder of the request or, if the
1066   request has already been completed, ignore this response. The server
1067   &MUST; send a final response after the request has been completed. See
1068   &use100; for detailed discussion of the use and handling of this
1069   status code.
1070</t>
1071</section>
1072
1073<section title="101 Switching Protocols" anchor="status.101">
1074  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1075  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1076<t>
1077   The server understands and is willing to comply with the client's
1078   request, via the Upgrade message header field (&header-upgrade;), for a
1079   change in the application protocol being used on this connection. The
1080   server will switch protocols to those defined by the response's
1081   Upgrade header field immediately after the empty line which
1082   terminates the 101 response.
1083</t>
1084<t>
1085   The protocol &SHOULD; be switched only when it is advantageous to do
1086   so. For example, switching to a newer version of HTTP is advantageous
1087   over older versions, and switching to a real-time, synchronous
1088   protocol might be advantageous when delivering resources that use
1089   such features.
1090</t>
1091</section>
1092</section>
1093
1094<section title="Successful 2xx" anchor="status.2xx">
1095<t>
1096   This class of status code indicates that the client's request was
1097   successfully received, understood, and accepted.
1098</t>
1099
1100<section title="200 OK" anchor="status.200">
1101  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1102  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1103<t>
1104   The request has succeeded. The information returned with the response
1105   is dependent on the method used in the request, for example:
1106  <list style="hanging">
1107    <t hangText="GET">
1108          an entity corresponding to the requested resource is sent in
1109          the response;
1110    </t>
1111    <t hangText="HEAD">
1112          the entity-header fields corresponding to the requested
1113          resource are sent in the response without any message-body;
1114    </t>
1115    <t hangText="POST">
1116      an entity describing or containing the result of the action;
1117    </t>
1118    <t hangText="TRACE">
1119      an entity containing the request message as received by the
1120      end server.
1121    </t>
1122  </list>
1123</t>
1124</section>
1125
1126<section title="201 Created" anchor="status.201">
1127  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1128  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1129<t>
1130   The request has been fulfilled and resulted in a new resource being
1131   created. The newly created resource can be referenced by the URI(s)
1132   returned in the entity of the response, with the most specific URI
1133   for the resource given by a Location header field. The response
1134   &SHOULD; include an entity containing a list of resource
1135   characteristics and location(s) from which the user or user agent can
1136   choose the one most appropriate. The entity format is specified by
1137   the media type given in the Content-Type header field. The origin
1138   server &MUST; create the resource before returning the 201 status code.
1139   If the action cannot be carried out immediately, the server &SHOULD;
1140   respond with 202 (Accepted) response instead.
1141</t>
1142<t>
1143   A 201 response &MAY; contain an ETag response header field indicating
1144   the current value of the entity tag for the requested variant just
1145   created, see &header-etag;.
1146</t>
1147</section>
1148
1149<section title="202 Accepted" anchor="status.202">
1150  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1151  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1152<t>
1153   The request has been accepted for processing, but the processing has
1154   not been completed.  The request might or might not eventually be
1155   acted upon, as it might be disallowed when processing actually takes
1156   place. There is no facility for re-sending a status code from an
1157   asynchronous operation such as this.
1158</t>
1159<t>
1160   The 202 response is intentionally non-committal. Its purpose is to
1161   allow a server to accept a request for some other process (perhaps a
1162   batch-oriented process that is only run once per day) without
1163   requiring that the user agent's connection to the server persist
1164   until the process is completed. The entity returned with this
1165   response &SHOULD; include an indication of the request's current status
1166   and either a pointer to a status monitor or some estimate of when the
1167   user can expect the request to be fulfilled.
1168</t>
1169</section>
1170
1171<section title="203 Non-Authoritative Information" anchor="status.203">
1172  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1173  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1174<t>
1175   The returned metainformation in the entity-header is not the
1176   definitive set as available from the origin server, but is gathered
1177   from a local or a third-party copy. The set presented &MAY; be a subset
1178   or superset of the original version. For example, including local
1179   annotation information about the resource might result in a superset
1180   of the metainformation known by the origin server. Use of this
1181   response code is not required and is only appropriate when the
1182   response would otherwise be 200 (OK).
1183</t>
1184</section>
1185
1186<section title="204 No Content" anchor="status.204">
1187  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1188  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1189<t>
1190   The server has fulfilled the request but does not need to return an
1191   entity-body, and might want to return updated metainformation. The
1192   response &MAY; include new or updated metainformation in the form of
1193   entity-headers, which if present &SHOULD; be associated with the
1194   requested variant.
1195</t>
1196<t>
1197   If the client is a user agent, it &SHOULD-NOT;  change its document view
1198   from that which caused the request to be sent. This response is
1199   primarily intended to allow input for actions to take place without
1200   causing a change to the user agent's active document view, although
1201   any new or updated metainformation &SHOULD; be applied to the document
1202   currently in the user agent's active view.
1203</t>
1204<t>
1205   The 204 response &MUST-NOT; include a message-body, and thus is always
1206   terminated by the first empty line after the header fields.
1207</t>
1208</section>
1209
1210<section title="205 Reset Content" anchor="status.205">
1211  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1212  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1213<t>
1214   The server has fulfilled the request and the user agent &SHOULD; reset
1215   the document view which caused the request to be sent. This response
1216   is primarily intended to allow input for actions to take place via
1217   user input, followed by a clearing of the form in which the input is
1218   given so that the user can easily initiate another input action. The
1219   response &MUST-NOT; include an entity.
1220</t>
1221</section>
1222
1223<section title="206 Partial Content" anchor="status.206">
1224  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1225  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1226<t>
1227   The server has fulfilled the partial GET request for the resource
1228   and the enclosed entity is a partial representation as defined in &range;.
1229</t>
1230</section>
1231</section>
1232
1233<section title="Redirection 3xx" anchor="status.3xx">
1234<t>
1235   This class of status code indicates that further action needs to be
1236   taken by the user agent in order to fulfill the request.  The action
1237   required &MAY; be carried out by the user agent without interaction
1238   with the user if and only if the method used in the second request is
1239   GET or HEAD. A client &SHOULD; detect infinite redirection loops, since
1240   such loops generate network traffic for each redirection.
1241  <list><t>
1242      <x:h>Note:</x:h> previous versions of this specification recommended a
1243      maximum of five redirections. Content developers should be aware
1244      that there might be clients that implement such a fixed
1245      limitation.
1246  </t></list>
1247</t>
1248
1249<section title="300 Multiple Choices" anchor="status.300">
1250  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1251  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1252<t>
1253   The requested resource corresponds to any one of a set of
1254   representations, each with its own specific location, and agent-driven
1255   negotiation information (&content-negotiation;) is being provided so that
1256   the user (or user agent) can select a preferred representation and
1257   redirect its request to that location.
1258</t>
1259<t>
1260   Unless it was a HEAD request, the response &SHOULD; include an entity
1261   containing a list of resource characteristics and location(s) from
1262   which the user or user agent can choose the one most appropriate. The
1263   entity format is specified by the media type given in the Content-Type
1264   header field. Depending upon the format and the capabilities of
1265   the user agent, selection of the most appropriate choice &MAY; be
1266   performed automatically. However, this specification does not define
1267   any standard for such automatic selection.
1268</t>
1269<t>
1270   If the server has a preferred choice of representation, it &SHOULD;
1271   include the specific URI for that representation in the Location
1272   field; user agents &MAY; use the Location field value for automatic
1273   redirection. This response is cacheable unless indicated otherwise.
1274</t>
1275</section>
1276
1277<section title="301 Moved Permanently" anchor="status.301">
1278  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1279  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1280<t>
1281   The requested resource has been assigned a new permanent URI and any
1282   future references to this resource &SHOULD; use one of the returned
1283   URIs.  Clients with link editing capabilities ought to automatically
1284   re-link references to the request-target to one or more of the new
1285   references returned by the server, where possible. This response is
1286   cacheable unless indicated otherwise.
1287</t>
1288<t>
1289   The new permanent URI &SHOULD; be given by the Location field in the
1290   response. Unless the request method was HEAD, the entity of the
1291   response &SHOULD; contain a short hypertext note with a hyperlink to
1292   the new URI(s).
1293</t>
1294<t>
1295   If the 301 status code is received in response to a request method
1296   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1297   then the request &MAY; be automatically redirected by the user agent without
1298   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1299   request unless it can be confirmed by the user, since this might
1300   change the conditions under which the request was issued.
1301  <list><t>
1302      <x:h>Note:</x:h> When automatically redirecting a POST request after
1303      receiving a 301 status code, some existing HTTP/1.0 user agents
1304      will erroneously change it into a GET request.
1305  </t></list>
1306</t>
1307</section>
1308
1309<section title="302 Found" anchor="status.302">
1310  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1311  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1312<t>
1313   The requested resource resides temporarily under a different URI.
1314   Since the redirection might be altered on occasion, the client &SHOULD;
1315   continue to use the request-target for future requests.  This response
1316   is only cacheable if indicated by a Cache-Control or Expires header
1317   field.
1318</t>
1319<t>
1320   The temporary URI &SHOULD; be given by the Location field in the
1321   response. Unless the request method was HEAD, the entity of the
1322   response &SHOULD; contain a short hypertext note with a hyperlink to
1323   the new URI(s).
1324</t>
1325<t>
1326   If the 302 status code is received in response to a request method
1327   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1328   then the request &MAY; be automatically redirected by the user agent without
1329   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1330   request unless it can be confirmed by the user, since this might
1331   change the conditions under which the request was issued.
1332  <list><t>
1333      <x:h>Note:</x:h> <xref target="RFC1945"/> and <xref target="RFC2068"/> specify that the client is not allowed
1334      to change the method on the redirected request.  However, most
1335      existing user agent implementations treat 302 as if it were a 303
1336      response, performing a GET on the Location field-value regardless
1337      of the original request method. The status codes 303 and 307 have
1338      been added for servers that wish to make unambiguously clear which
1339      kind of reaction is expected of the client.
1340  </t></list>
1341</t>
1342</section>
1343
1344<section title="303 See Other" anchor="status.303">
1345  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1346  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1347<t>
1348   The server directs the user agent to a different resource, indicated
1349   by a URI in the Location header field, that provides an indirect
1350   response to the original request.  The user agent &MAY; perform a GET
1351   request on the URI in the Location field in order to obtain a
1352   representation corresponding to the response, be redirected again,
1353   or end with an error status.  The Location URI is not a substitute
1354   reference for the originally requested resource.
1355</t>
1356<t>
1357   The 303 status is generally applicable to any HTTP method.  It is
1358   primarily used to allow the output of a POST action to redirect
1359   the user agent to a selected resource, since doing so provides the
1360   information corresponding to the POST response in a form that
1361   can be separately identified, bookmarked, and cached independent
1362   of the original request.
1363</t>
1364<t>
1365   A 303 response to a GET request indicates that the requested
1366   resource does not have a representation of its own that can be
1367   transferred by the server over HTTP.  The Location URI indicates a
1368   resource that is descriptive of the requested resource such that
1369   the follow-on representation may be useful without implying that
1370   it adequately represents the previously requested resource.
1371   Note that answers to the questions of what can be represented, what
1372   representations are adequate, and what might be a useful description
1373   are outside the scope of HTTP and thus entirely determined by the
1374   resource owner(s).
1375</t>
1376<t>
1377   A 303 response &SHOULD-NOT; be cached unless it is indicated as
1378   cacheable by Cache-Control or Expires header fields.  Except for
1379   responses to a HEAD request, the entity of a 303 response &SHOULD;
1380   contain a short hypertext note with a hyperlink to the Location URI.
1381</t>
1382</section>
1383
1384<section title="304 Not Modified" anchor="status.304">
1385  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1386  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1387<t>
1388   The response to the request has not been modified since the conditions
1389   indicated by the client's conditional GET request, as defined in &conditional;.
1390</t>
1391</section>
1392
1393<section title="305 Use Proxy" anchor="status.305">
1394  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1395  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1396<t>
1397   The 305 status was defined in a previous version of this specification
1398   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1399</t>
1400</section>
1401
1402<section title="306 (Unused)" anchor="status.306">
1403  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1404  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1405<t>
1406   The 306 status code was used in a previous version of the
1407   specification, is no longer used, and the code is reserved.
1408</t>
1409</section>
1410
1411<section title="307 Temporary Redirect" anchor="status.307">
1412  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1413  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1414<t>
1415   The requested resource resides temporarily under a different URI.
1416   Since the redirection &MAY; be altered on occasion, the client &SHOULD;
1417   continue to use the request-target for future requests.  This response
1418   is only cacheable if indicated by a Cache-Control or Expires header
1419   field.
1420</t>
1421<t>
1422   The temporary URI &SHOULD; be given by the Location field in the
1423   response. Unless the request method was HEAD, the entity of the
1424   response &SHOULD; contain a short hypertext note with a hyperlink to
1425   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1426   understand the 307 status. Therefore, the note &SHOULD; contain the
1427   information necessary for a user to repeat the original request on
1428   the new URI.
1429</t>
1430<t>
1431   If the 307 status code is received in response to a request method
1432   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1433   then the request &MAY; be automatically redirected by the user agent without
1434   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1435   request unless it can be confirmed by the user, since this might
1436   change the conditions under which the request was issued.
1437</t>
1438</section>
1439</section>
1440
1441<section title="Client Error 4xx" anchor="status.4xx">
1442<t>
1443   The 4xx class of status code is intended for cases in which the
1444   client seems to have erred. Except when responding to a HEAD request,
1445   the server &SHOULD; include an entity containing an explanation of the
1446   error situation, and whether it is a temporary or permanent
1447   condition. These status codes are applicable to any request method.
1448   User agents &SHOULD; display any included entity to the user.
1449</t>
1450<t>
1451   If the client is sending data, a server implementation using TCP
1452   &SHOULD; be careful to ensure that the client acknowledges receipt of
1453   the packet(s) containing the response, before the server closes the
1454   input connection. If the client continues sending data to the server
1455   after the close, the server's TCP stack will send a reset packet to
1456   the client, which may erase the client's unacknowledged input buffers
1457   before they can be read and interpreted by the HTTP application.
1458</t>
1459
1460<section title="400 Bad Request" anchor="status.400">
1461  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1462  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1463<t>
1464   The request could not be understood by the server due to malformed
1465   syntax. The client &SHOULD-NOT;  repeat the request without
1466   modifications.
1467</t>
1468</section>
1469
1470<section title="401 Unauthorized" anchor="status.401">
1471  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1472  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1473<t>
1474   The request requires user authentication (see &auth;).
1475</t>
1476</section>
1477
1478<section title="402 Payment Required" anchor="status.402">
1479  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1480  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1481<t>
1482   This code is reserved for future use.
1483</t>
1484</section>
1485
1486<section title="403 Forbidden" anchor="status.403">
1487  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1488  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1489<t>
1490   The server understood the request, but is refusing to fulfill it.
1491   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1492   If the request method was not HEAD and the server wishes to make
1493   public why the request has not been fulfilled, it &SHOULD; describe the
1494   reason for the refusal in the entity.  If the server does not wish to
1495   make this information available to the client, the status code 404
1496   (Not Found) can be used instead.
1497</t>
1498</section>
1499
1500<section title="404 Not Found" anchor="status.404">
1501  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1502  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1503<t>
1504   The server has not found anything matching the request-target. No
1505   indication is given of whether the condition is temporary or
1506   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1507   knows, through some internally configurable mechanism, that an old
1508   resource is permanently unavailable and has no forwarding address.
1509   This status code is commonly used when the server does not wish to
1510   reveal exactly why the request has been refused, or when no other
1511   response is applicable.
1512</t>
1513</section>
1514
1515<section title="405 Method Not Allowed" anchor="status.405">
1516  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1517  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1518<t>
1519   The method specified in the Request-Line is not allowed for the
1520   resource identified by the request-target. The response &MUST; include an
1521   Allow header containing a list of valid methods for the requested
1522   resource.
1523</t>
1524</section>
1525
1526<section title="406 Not Acceptable" anchor="status.406">
1527  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1528  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1529<t>
1530   The resource identified by the request is only capable of generating
1531   response entities which have content characteristics not acceptable
1532   according to the accept headers sent in the request.
1533</t>
1534<t>
1535   Unless it was a HEAD request, the response &SHOULD; include an entity
1536   containing a list of available entity characteristics and location(s)
1537   from which the user or user agent can choose the one most
1538   appropriate. The entity format is specified by the media type given
1539   in the Content-Type header field. Depending upon the format and the
1540   capabilities of the user agent, selection of the most appropriate
1541   choice &MAY; be performed automatically. However, this specification
1542   does not define any standard for such automatic selection.
1543  <list><t>
1544      <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1545      not acceptable according to the accept headers sent in the
1546      request. In some cases, this may even be preferable to sending a
1547      406 response. User agents are encouraged to inspect the headers of
1548      an incoming response to determine if it is acceptable.
1549  </t></list>
1550</t>
1551<t>
1552   If the response could be unacceptable, a user agent &SHOULD;
1553   temporarily stop receipt of more data and query the user for a
1554   decision on further actions.
1555</t>
1556</section>
1557
1558<section title="407 Proxy Authentication Required" anchor="status.407">
1559  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1560  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1561<t>
1562   This code is similar to 401 (Unauthorized), but indicates that the
1563   client must first authenticate itself with the proxy (see &auth;).
1564</t>
1565</section>
1566
1567<section title="408 Request Timeout" anchor="status.408">
1568  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1569  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1570<t>
1571   The client did not produce a request within the time that the server
1572   was prepared to wait. The client &MAY; repeat the request without
1573   modifications at any later time.
1574</t>
1575</section>
1576
1577<section title="409 Conflict" anchor="status.409">
1578  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1579  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1580<t>
1581   The request could not be completed due to a conflict with the current
1582   state of the resource. This code is only allowed in situations where
1583   it is expected that the user might be able to resolve the conflict
1584   and resubmit the request. The response body &SHOULD; include enough
1585   information for the user to recognize the source of the conflict.
1586   Ideally, the response entity would include enough information for the
1587   user or user agent to fix the problem; however, that might not be
1588   possible and is not required.
1589</t>
1590<t>
1591   Conflicts are most likely to occur in response to a PUT request. For
1592   example, if versioning were being used and the entity being PUT
1593   included changes to a resource which conflict with those made by an
1594   earlier (third-party) request, the server might use the 409 response
1595   to indicate that it can't complete the request. In this case, the
1596   response entity would likely contain a list of the differences
1597   between the two versions in a format defined by the response
1598   Content-Type.
1599</t>
1600</section>
1601
1602<section title="410 Gone" anchor="status.410">
1603  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1604  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1605<t>
1606   The requested resource is no longer available at the server and no
1607   forwarding address is known. This condition is expected to be
1608   considered permanent. Clients with link editing capabilities &SHOULD;
1609   delete references to the request-target after user approval. If the
1610   server does not know, or has no facility to determine, whether or not
1611   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1612   used instead. This response is cacheable unless indicated otherwise.
1613</t>
1614<t>
1615   The 410 response is primarily intended to assist the task of web
1616   maintenance by notifying the recipient that the resource is
1617   intentionally unavailable and that the server owners desire that
1618   remote links to that resource be removed. Such an event is common for
1619   limited-time, promotional services and for resources belonging to
1620   individuals no longer working at the server's site. It is not
1621   necessary to mark all permanently unavailable resources as "gone" or
1622   to keep the mark for any length of time -- that is left to the
1623   discretion of the server owner.
1624</t>
1625</section>
1626
1627<section title="411 Length Required" anchor="status.411">
1628  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1629  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1630<t>
1631   The server refuses to accept the request without a defined Content-Length.
1632   The client &MAY; repeat the request if it adds a valid
1633   Content-Length header field containing the length of the message-body
1634   in the request message.
1635</t>
1636</section>
1637
1638<section title="412 Precondition Failed" anchor="status.412">
1639  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1640  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1641<t>
1642   The precondition given in one or more of the request-header fields
1643   evaluated to false when it was tested on the server, as defined in
1644   &conditional;.
1645</t>
1646</section>
1647
1648<section title="413 Request Entity Too Large" anchor="status.413">
1649  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1650  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1651<t>
1652   The server is refusing to process a request because the request
1653   entity is larger than the server is willing or able to process. The
1654   server &MAY; close the connection to prevent the client from continuing
1655   the request.
1656</t>
1657<t>
1658   If the condition is temporary, the server &SHOULD; include a Retry-After
1659   header field to indicate that it is temporary and after what
1660   time the client &MAY; try again.
1661</t>
1662</section>
1663
1664<section title="414 URI Too Long" anchor="status.414">
1665  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
1666  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
1667<t>
1668   The server is refusing to service the request because the request-target
1669   is longer than the server is willing to interpret. This rare
1670   condition is only likely to occur when a client has improperly
1671   converted a POST request to a GET request with long query
1672   information, when the client has descended into a URI "black hole" of
1673   redirection (e.g., a redirected URI prefix that points to a suffix of
1674   itself), or when the server is under attack by a client attempting to
1675   exploit security holes present in some servers using fixed-length
1676   buffers for reading or manipulating the request-target.
1677</t>
1678</section>
1679
1680<section title="415 Unsupported Media Type" anchor="status.415">
1681  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1682  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1683<t>
1684   The server is refusing to service the request because the entity of
1685   the request is in a format not supported by the requested resource
1686   for the requested method.
1687</t>
1688</section>
1689
1690<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1691  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1692  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1693<t>
1694   The request included a Range request-header field (&header-range;) and none of
1695   the range-specifier values in this field overlap the current extent
1696   of the selected resource.
1697</t>
1698</section>
1699
1700<section title="417 Expectation Failed" anchor="status.417">
1701  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1702  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1703<t>
1704   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1705   could not be met by this server, or, if the server is a proxy,
1706   the server has unambiguous evidence that the request could not be met
1707   by the next-hop server.
1708</t>
1709</section>
1710</section>
1711
1712<section title="Server Error 5xx" anchor="status.5xx">
1713<t>
1714   Response status codes beginning with the digit "5" indicate cases in
1715   which the server is aware that it has erred or is incapable of
1716   performing the request. Except when responding to a HEAD request, the
1717   server &SHOULD; include an entity containing an explanation of the
1718   error situation, and whether it is a temporary or permanent
1719   condition. User agents &SHOULD; display any included entity to the
1720   user. These response codes are applicable to any request method.
1721</t>
1722
1723<section title="500 Internal Server Error" anchor="status.500">
1724  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1725  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1726<t>
1727   The server encountered an unexpected condition which prevented it
1728   from fulfilling the request.
1729</t>
1730</section>
1731
1732<section title="501 Not Implemented" anchor="status.501">
1733  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1734  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1735<t>
1736   The server does not support the functionality required to fulfill the
1737   request. This is the appropriate response when the server does not
1738   recognize the request method and is not capable of supporting it for
1739   any resource.
1740</t>
1741</section>
1742
1743<section title="502 Bad Gateway" anchor="status.502">
1744  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1745  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1746<t>
1747   The server, while acting as a gateway or proxy, received an invalid
1748   response from the upstream server it accessed in attempting to
1749   fulfill the request.
1750</t>
1751</section>
1752
1753<section title="503 Service Unavailable" anchor="status.503">
1754  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1755  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1756<t>
1757   The server is currently unable to handle the request due to a
1758   temporary overloading or maintenance of the server. The implication
1759   is that this is a temporary condition which will be alleviated after
1760   some delay. If known, the length of the delay &MAY; be indicated in a
1761   Retry-After header. If no Retry-After is given, the client &SHOULD;
1762   handle the response as it would for a 500 response.
1763  <list><t>
1764      <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1765      server must use it when becoming overloaded. Some servers may wish
1766      to simply refuse the connection.
1767  </t></list>
1768</t>
1769</section>
1770
1771<section title="504 Gateway Timeout" anchor="status.504">
1772  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1773  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1774<t>
1775   The server, while acting as a gateway or proxy, did not receive a
1776   timely response from the upstream server specified by the URI (e.g.
1777   HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed
1778   to access in attempting to complete the request.
1779  <list><t>
1780      <x:h>Note:</x:h> Note to implementors: some deployed proxies are known to
1781      return 400 or 500 when DNS lookups time out.
1782  </t></list>
1783</t>
1784</section>
1785
1786<section title="505 HTTP Version Not Supported" anchor="status.505">
1787  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1788  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
1789<t>
1790   The server does not support, or refuses to support, the protocol
1791   version that was used in the request message. The server is
1792   indicating that it is unable or unwilling to complete the request
1793   using the same major version as the client, as described in &http-version;,
1794   other than with this error message. The response &SHOULD; contain
1795   an entity describing why that version is not supported and what other
1796   protocols are supported by that server.
1797</t>
1798
1799</section>
1800</section>
1801</section>
1802
1803
1804<section title="Header Field Definitions" anchor="header.fields">
1805<t>
1806   This section defines the syntax and semantics of HTTP/1.1 header fields
1807   related to request and response semantics.
1808</t>
1809<t>
1810   For entity-header fields, both sender and recipient refer to either the
1811   client or the server, depending on who sends and who receives the entity.
1812</t>
1813
1814<section title="Allow" anchor="header.allow">
1815  <iref primary="true" item="Allow header" x:for-anchor=""/>
1816  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
1817  <x:anchor-alias value="Allow"/>
1818  <x:anchor-alias value="Allow-v"/>
1819<t>
1820      The response-header field "Allow" lists the set of methods advertised as
1821      supported by the resource identified by the request-target. The purpose of
1822      this field is strictly to inform the recipient of valid methods
1823      associated with the resource. An Allow header field &MUST; be
1824      present in a 405 (Method Not Allowed) response.
1825</t>
1826<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
1827  <x:ref>Allow</x:ref>   = "Allow" ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
1828  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
1829</artwork></figure>
1830<t>
1831      Example of use:
1832</t>
1833<figure><artwork type="example">
1834  Allow: GET, HEAD, PUT
1835</artwork></figure>
1836<t>
1837      The actual set of allowed methods is defined
1838      by the origin server at the time of each request.
1839</t>
1840<t>
1841      A proxy &MUST-NOT; modify the Allow header field even if it does not
1842      understand all the methods specified, since the user agent might
1843      have other means of communicating with the origin server.
1844</t>
1845</section>
1846
1847<section title="Expect" anchor="header.expect">
1848  <iref primary="true" item="Expect header" x:for-anchor=""/>
1849  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
1850  <x:anchor-alias value="Expect"/>
1851  <x:anchor-alias value="Expect-v"/>
1852  <x:anchor-alias value="expectation"/>
1853  <x:anchor-alias value="expectation-extension"/>
1854  <x:anchor-alias value="expect-params"/>
1855<t>
1856   The request-header field "Expect" is used to indicate that particular
1857   server behaviors are required by the client.
1858</t>
1859<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Expect"/><iref primary="true" item="Grammar" subitem="Expect-v"/><iref primary="true" item="Grammar" subitem="expectation"/><iref primary="true" item="Grammar" subitem="expectation-extension"/><iref primary="true" item="Grammar" subitem="expect-params"/>
1860  <x:ref>Expect</x:ref>       = "Expect" ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
1861  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
1862 
1863  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
1864  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
1865                           *<x:ref>expect-params</x:ref> ]
1866  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
1867</artwork></figure>
1868<t>
1869   A server that does not understand or is unable to comply with any of
1870   the expectation values in the Expect field of a request &MUST; respond
1871   with appropriate error status. The server &MUST; respond with a 417
1872   (Expectation Failed) status if any of the expectations cannot be met
1873   or, if there are other problems with the request, some other 4xx
1874   status.
1875</t>
1876<t>
1877   This header field is defined with extensible syntax to allow for
1878   future extensions. If a server receives a request containing an
1879   Expect field that includes an expectation-extension that it does not
1880   support, it &MUST; respond with a 417 (Expectation Failed) status.
1881</t>
1882<t>
1883   Comparison of expectation values is case-insensitive for unquoted
1884   tokens (including the 100-continue token), and is case-sensitive for
1885   quoted-string expectation-extensions.
1886</t>
1887<t>
1888   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
1889   return a 417 (Expectation Failed) status if it receives a request
1890   with an expectation that it cannot meet. However, the Expect
1891   request-header itself is end-to-end; it &MUST; be forwarded if the
1892   request is forwarded.
1893</t>
1894<t>
1895   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1896   Expect header.
1897</t>
1898<t>
1899   See &use100; for the use of the 100 (Continue) status.
1900</t>
1901</section>
1902
1903<section title="From" anchor="header.from">
1904  <iref primary="true" item="From header" x:for-anchor=""/>
1905  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
1906  <x:anchor-alias value="From"/>
1907  <x:anchor-alias value="From-v"/>
1908  <x:anchor-alias value="mailbox"/>
1909<t>
1910   The request-header field "From", if given, &SHOULD; contain an Internet
1911   e-mail address for the human user who controls the requesting user
1912   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
1913   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
1914</t>
1915<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
1916  <x:ref>From</x:ref>    = "From" ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
1917  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
1918 
1919  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
1920</artwork></figure>
1921<t>
1922   An example is:
1923</t>
1924<figure><artwork type="example">
1925  From: webmaster@example.org
1926</artwork></figure>
1927<t>
1928   This header field &MAY; be used for logging purposes and as a means for
1929   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
1930   be used as an insecure form of access protection. The interpretation
1931   of this field is that the request is being performed on behalf of the
1932   person given, who accepts responsibility for the method performed. In
1933   particular, robot agents &SHOULD; include this header so that the
1934   person responsible for running the robot can be contacted if problems
1935   occur on the receiving end.
1936</t>
1937<t>
1938   The Internet e-mail address in this field &MAY; be separate from the
1939   Internet host which issued the request. For example, when a request
1940   is passed through a proxy the original issuer's address &SHOULD; be
1941   used.
1942</t>
1943<t>
1944   The client &SHOULD-NOT;  send the From header field without the user's
1945   approval, as it might conflict with the user's privacy interests or
1946   their site's security policy. It is strongly recommended that the
1947   user be able to disable, enable, and modify the value of this field
1948   at any time prior to a request.
1949</t>
1950</section>
1951
1952<section title="Location" anchor="header.location">
1953  <iref primary="true" item="Location header" x:for-anchor=""/>
1954  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
1955  <x:anchor-alias value="Location"/>
1956  <x:anchor-alias value="Location-v"/>
1957<t>
1958   The response-header field "Location" is used for the identification of a
1959   new resource or to redirect the recipient to a location other than the
1960   request-target for completion of the request.  For 201 (Created)
1961   responses, the Location is that of the new resource which was created
1962   by the request. For 3xx responses, the location &SHOULD; indicate the
1963   server's preferred URI for automatic redirection to the resource. The
1964   field value consists of a single absolute URI.
1965</t>
1966<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
1967  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
1968  <x:ref>Location-v</x:ref>     = <x:ref>absolute-URI</x:ref> [ "#" <x:ref>fragment</x:ref> ]
1969</artwork></figure>
1970<t>
1971   An example is:
1972</t>
1973<figure><artwork type="example">
1974  Location: http://www.example.org/pub/WWW/People.html
1975</artwork></figure>
1976<t>
1977  <list><t>
1978      <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
1979      from Location in that the Content-Location identifies the original
1980      location of the entity enclosed in the response. It is therefore
1981      possible for a response to contain header fields for both Location
1982      and Content-Location.
1983  </t></list>
1984</t>
1985<t>
1986   There are circumstances in which a fragment identifier in a Location URL would not be appropriate:
1987   <list style="symbols">
1988      <t>With a 201 Created response, because in this usage the Location header specifies the URL for the entire created resource.</t>
1989      <t>With a 300 Multiple Choices, since the choice decision is intended to be made on resource characteristics and not fragment characteristics.</t>
1990      <t>With 305 Use Proxy.</t>
1991   </list>
1992</t>
1993</section>
1994
1995<section title="Max-Forwards" anchor="header.max-forwards">
1996  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
1997  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
1998  <x:anchor-alias value="Max-Forwards"/>
1999  <x:anchor-alias value="Max-Forwards-v"/>
2000<t>
2001   The request-header "Max-Forwards" field provides a mechanism with the
2002   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>) methods to limit the
2003   number of proxies or gateways that can forward the request to the
2004   next inbound server. This can be useful when the client is attempting
2005   to trace a request chain which appears to be failing or looping in
2006   mid-chain.
2007</t>
2008<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
2009  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
2010  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
2011</artwork></figure>
2012<t>
2013   The Max-Forwards value is a decimal integer indicating the remaining
2014   number of times this request message may be forwarded.
2015</t>
2016<t>
2017   Each proxy or gateway recipient of a TRACE or OPTIONS request
2018   containing a Max-Forwards header field &MUST; check and update its
2019   value prior to forwarding the request. If the received value is zero
2020   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2021   respond as the final recipient. If the received Max-Forwards value is
2022   greater than zero, then the forwarded message &MUST; contain an updated
2023   Max-Forwards field with a value decremented by one (1).
2024</t>
2025<t>
2026   The Max-Forwards header field &MAY; be ignored for all other methods
2027   defined by this specification and for any extension methods for which
2028   it is not explicitly referred to as part of that method definition.
2029</t>
2030</section>
2031
2032<section title="Referer" anchor="header.referer">
2033  <iref primary="true" item="Referer header" x:for-anchor=""/>
2034  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
2035  <x:anchor-alias value="Referer"/>
2036  <x:anchor-alias value="Referer-v"/>
2037<t>
2038   The request-header field "Referer" [sic] allows the client to specify,
2039   for the server's benefit, the address (URI) of the resource from
2040   which the request-target was obtained (the "referrer", although the
2041   header field is misspelled.) The Referer request-header allows a
2042   server to generate lists of back-links to resources for interest,
2043   logging, optimized caching, etc. It also allows obsolete or mistyped
2044   links to be traced for maintenance. The Referer field &MUST-NOT; be
2045   sent if the request-target was obtained from a source that does not have
2046   its own URI, such as input from the user keyboard.
2047</t>
2048<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
2049  <x:ref>Referer</x:ref>        = "Referer" ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
2050  <x:ref>Referer-v</x:ref>      = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2051</artwork></figure>
2052<t>
2053   Example:
2054</t>
2055<figure><artwork type="example">
2056  Referer: http://www.example.org/hypertext/Overview.html
2057</artwork></figure>
2058<t>
2059   If the field value is a relative URI, it &SHOULD; be interpreted
2060   relative to the request-target. The URI &MUST-NOT; include a fragment. See
2061   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2062</t>
2063</section>
2064
2065<section title="Retry-After" anchor="header.retry-after">
2066  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2067  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
2068  <x:anchor-alias value="Retry-After"/>
2069  <x:anchor-alias value="Retry-After-v"/>
2070<t>
2071   The response-header "Retry-After" field can be used with a 503 (Service
2072   Unavailable) response to indicate how long the service is expected to
2073   be unavailable to the requesting client. This field &MAY; also be used
2074   with any 3xx (Redirection) response to indicate the minimum time the
2075   user-agent is asked wait before issuing the redirected request. The
2076   value of this field can be either an HTTP-date or an integer number
2077   of seconds (in decimal) after the time of the response.
2078</t>
2079<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
2080  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
2081  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2082</artwork></figure>
2083<t anchor="rule.delta-seconds">
2084  <x:anchor-alias value="delta-seconds"/>
2085   Time spans are non-negative decimal integers, representing time in
2086   seconds.
2087</t>
2088<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2089  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2090</artwork></figure>
2091<t>
2092   Two examples of its use are
2093</t>
2094<figure><artwork type="example">
2095  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2096  Retry-After: 120
2097</artwork></figure>
2098<t>
2099   In the latter example, the delay is 2 minutes.
2100</t>
2101</section>
2102
2103<section title="Server" anchor="header.server">
2104  <iref primary="true" item="Server header" x:for-anchor=""/>
2105  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
2106  <x:anchor-alias value="Server"/>
2107  <x:anchor-alias value="Server-v"/>
2108<t>
2109   The response-header field "Server" contains information about the
2110   software used by the origin server to handle the request. The field
2111   can contain multiple product tokens (&product-tokens;) and comments
2112   identifying the server and any significant subproducts. The product
2113   tokens are listed in order of their significance for identifying the
2114   application.
2115</t>
2116<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
2117  <x:ref>Server</x:ref>         = "Server" ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
2118  <x:ref>Server-v</x:ref>       = <x:ref>product</x:ref>
2119                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2120</artwork></figure>
2121<t>
2122   Example:
2123</t>
2124<figure><artwork type="example">
2125  Server: CERN/3.0 libwww/2.17
2126</artwork></figure>
2127<t>
2128   If the response is being forwarded through a proxy, the proxy
2129   application &MUST-NOT; modify the Server response-header. Instead, it
2130   &MUST; include a Via field (as described in &header-via;).
2131  <list><t>
2132      <x:h>Note:</x:h> Revealing the specific software version of the server might
2133      allow the server machine to become more vulnerable to attacks
2134      against software that is known to contain security holes. Server
2135      implementors are encouraged to make this field a configurable
2136      option.
2137  </t></list>
2138</t>
2139</section>
2140
2141<section title="User-Agent" anchor="header.user-agent">
2142  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2143  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
2144  <x:anchor-alias value="User-Agent"/>
2145  <x:anchor-alias value="User-Agent-v"/>
2146<t>
2147   The request-header field "User-Agent" contains information about the
2148   user agent originating the request. This is for statistical purposes,
2149   the tracing of protocol violations, and automated recognition of user
2150   agents for the sake of tailoring responses to avoid particular user
2151   agent limitations. User agents &SHOULD; include this field with
2152   requests. The field can contain multiple product tokens (&product-tokens;)
2153   and comments identifying the agent and any subproducts which form a
2154   significant part of the user agent. By convention, the product tokens
2155   are listed in order of their significance for identifying the
2156   application.
2157</t>
2158<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
2159  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
2160  <x:ref>User-Agent-v</x:ref>   = <x:ref>product</x:ref>
2161                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2162</artwork></figure>
2163<t>
2164   Example:
2165</t>
2166<figure><artwork type="example">
2167  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2168</artwork></figure>
2169</section>
2170
2171</section>
2172
2173<section title="IANA Considerations" anchor="IANA.considerations">
2174
2175<section title="Method Registry" anchor="method.registration">
2176<t>
2177  The registration procedure for HTTP Methods is defined by
2178  <xref target="method.registry"/> of this document.
2179</t>
2180<t>
2181   The HTTP Method Registry located at <eref target="http://www.iana.org/assignments/http-methods"/>
2182   should be populated with the registrations below:
2183</t>
2184<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2185<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2186   <ttcol>Method</ttcol>
2187   <ttcol>Safe</ttcol>
2188   <ttcol>Reference</ttcol>
2189   <c>CONNECT</c>
2190   <c>no</c>
2191   <c>
2192      <xref target="CONNECT"/>
2193   </c>
2194   <c>DELETE</c>
2195   <c>no</c>
2196   <c>
2197      <xref target="DELETE"/>
2198   </c>
2199   <c>GET</c>
2200   <c>yes</c>
2201   <c>
2202      <xref target="GET"/>
2203   </c>
2204   <c>HEAD</c>
2205   <c>yes</c>
2206   <c>
2207      <xref target="HEAD"/>
2208   </c>
2209   <c>OPTIONS</c>
2210   <c>yes</c>
2211   <c>
2212      <xref target="OPTIONS"/>
2213   </c>
2214   <c>POST</c>
2215   <c>no</c>
2216   <c>
2217      <xref target="POST"/>
2218   </c>
2219   <c>PUT</c>
2220   <c>no</c>
2221   <c>
2222      <xref target="PUT"/>
2223   </c>
2224   <c>TRACE</c>
2225   <c>yes</c>
2226   <c>
2227      <xref target="TRACE"/>
2228   </c>
2229</texttable>
2230<!--(END)-->
2231</section>
2232
2233<section title="Status Code Registry" anchor="status.code.registration">
2234<t>
2235   The registration procedure for HTTP Status Codes -- previously defined
2236   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> -- is now defined
2237   by <xref target="status.code.registry"/> of this document.
2238</t>
2239<t>
2240   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2241   should be updated with the registrations below:
2242</t>
2243<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2244<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2245   <ttcol>Value</ttcol>
2246   <ttcol>Description</ttcol>
2247   <ttcol>Reference</ttcol>
2248   <c>100</c>
2249   <c>Continue</c>
2250   <c>
2251      <xref target="status.100"/>
2252   </c>
2253   <c>101</c>
2254   <c>Switching Protocols</c>
2255   <c>
2256      <xref target="status.101"/>
2257   </c>
2258   <c>200</c>
2259   <c>OK</c>
2260   <c>
2261      <xref target="status.200"/>
2262   </c>
2263   <c>201</c>
2264   <c>Created</c>
2265   <c>
2266      <xref target="status.201"/>
2267   </c>
2268   <c>202</c>
2269   <c>Accepted</c>
2270   <c>
2271      <xref target="status.202"/>
2272   </c>
2273   <c>203</c>
2274   <c>Non-Authoritative Information</c>
2275   <c>
2276      <xref target="status.203"/>
2277   </c>
2278   <c>204</c>
2279   <c>No Content</c>
2280   <c>
2281      <xref target="status.204"/>
2282   </c>
2283   <c>205</c>
2284   <c>Reset Content</c>
2285   <c>
2286      <xref target="status.205"/>
2287   </c>
2288   <c>206</c>
2289   <c>Partial Content</c>
2290   <c>
2291      <xref target="status.206"/>
2292   </c>
2293   <c>300</c>
2294   <c>Multiple Choices</c>
2295   <c>
2296      <xref target="status.300"/>
2297   </c>
2298   <c>301</c>
2299   <c>Moved Permanently</c>
2300   <c>
2301      <xref target="status.301"/>
2302   </c>
2303   <c>302</c>
2304   <c>Found</c>
2305   <c>
2306      <xref target="status.302"/>
2307   </c>
2308   <c>303</c>
2309   <c>See Other</c>
2310   <c>
2311      <xref target="status.303"/>
2312   </c>
2313   <c>304</c>
2314   <c>Not Modified</c>
2315   <c>
2316      <xref target="status.304"/>
2317   </c>
2318   <c>305</c>
2319   <c>Use Proxy</c>
2320   <c>
2321      <xref target="status.305"/>
2322   </c>
2323   <c>306</c>
2324   <c>(Unused)</c>
2325   <c>
2326      <xref target="status.306"/>
2327   </c>
2328   <c>307</c>
2329   <c>Temporary Redirect</c>
2330   <c>
2331      <xref target="status.307"/>
2332   </c>
2333   <c>400</c>
2334   <c>Bad Request</c>
2335   <c>
2336      <xref target="status.400"/>
2337   </c>
2338   <c>401</c>
2339   <c>Unauthorized</c>
2340   <c>
2341      <xref target="status.401"/>
2342   </c>
2343   <c>402</c>
2344   <c>Payment Required</c>
2345   <c>
2346      <xref target="status.402"/>
2347   </c>
2348   <c>403</c>
2349   <c>Forbidden</c>
2350   <c>
2351      <xref target="status.403"/>
2352   </c>
2353   <c>404</c>
2354   <c>Not Found</c>
2355   <c>
2356      <xref target="status.404"/>
2357   </c>
2358   <c>405</c>
2359   <c>Method Not Allowed</c>
2360   <c>
2361      <xref target="status.405"/>
2362   </c>
2363   <c>406</c>
2364   <c>Not Acceptable</c>
2365   <c>
2366      <xref target="status.406"/>
2367   </c>
2368   <c>407</c>
2369   <c>Proxy Authentication Required</c>
2370   <c>
2371      <xref target="status.407"/>
2372   </c>
2373   <c>408</c>
2374   <c>Request Timeout</c>
2375   <c>
2376      <xref target="status.408"/>
2377   </c>
2378   <c>409</c>
2379   <c>Conflict</c>
2380   <c>
2381      <xref target="status.409"/>
2382   </c>
2383   <c>410</c>
2384   <c>Gone</c>
2385   <c>
2386      <xref target="status.410"/>
2387   </c>
2388   <c>411</c>
2389   <c>Length Required</c>
2390   <c>
2391      <xref target="status.411"/>
2392   </c>
2393   <c>412</c>
2394   <c>Precondition Failed</c>
2395   <c>
2396      <xref target="status.412"/>
2397   </c>
2398   <c>413</c>
2399   <c>Request Entity Too Large</c>
2400   <c>
2401      <xref target="status.413"/>
2402   </c>
2403   <c>414</c>
2404   <c>URI Too Long</c>
2405   <c>
2406      <xref target="status.414"/>
2407   </c>
2408   <c>415</c>
2409   <c>Unsupported Media Type</c>
2410   <c>
2411      <xref target="status.415"/>
2412   </c>
2413   <c>416</c>
2414   <c>Requested Range Not Satisfiable</c>
2415   <c>
2416      <xref target="status.416"/>
2417   </c>
2418   <c>417</c>
2419   <c>Expectation Failed</c>
2420   <c>
2421      <xref target="status.417"/>
2422   </c>
2423   <c>500</c>
2424   <c>Internal Server Error</c>
2425   <c>
2426      <xref target="status.500"/>
2427   </c>
2428   <c>501</c>
2429   <c>Not Implemented</c>
2430   <c>
2431      <xref target="status.501"/>
2432   </c>
2433   <c>502</c>
2434   <c>Bad Gateway</c>
2435   <c>
2436      <xref target="status.502"/>
2437   </c>
2438   <c>503</c>
2439   <c>Service Unavailable</c>
2440   <c>
2441      <xref target="status.503"/>
2442   </c>
2443   <c>504</c>
2444   <c>Gateway Timeout</c>
2445   <c>
2446      <xref target="status.504"/>
2447   </c>
2448   <c>505</c>
2449   <c>HTTP Version Not Supported</c>
2450   <c>
2451      <xref target="status.505"/>
2452   </c>
2453</texttable>
2454<!--(END)-->
2455</section>
2456<section title="Message Header Registration" anchor="message.header.registration">
2457<t>
2458   The Message Header Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> should be updated
2459   with the permanent registrations below (see <xref target="RFC3864"/>):
2460</t>
2461<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2462<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2463   <ttcol>Header Field Name</ttcol>
2464   <ttcol>Protocol</ttcol>
2465   <ttcol>Status</ttcol>
2466   <ttcol>Reference</ttcol>
2467   <c>Allow</c>
2468   <c>http</c>
2469   <c>standard</c>
2470   <c>
2471      <xref target="header.allow"/>
2472   </c>
2473   <c>Expect</c>
2474   <c>http</c>
2475   <c>standard</c>
2476   <c>
2477      <xref target="header.expect"/>
2478   </c>
2479   <c>From</c>
2480   <c>http</c>
2481   <c>standard</c>
2482   <c>
2483      <xref target="header.from"/>
2484   </c>
2485   <c>Location</c>
2486   <c>http</c>
2487   <c>standard</c>
2488   <c>
2489      <xref target="header.location"/>
2490   </c>
2491   <c>Max-Forwards</c>
2492   <c>http</c>
2493   <c>standard</c>
2494   <c>
2495      <xref target="header.max-forwards"/>
2496   </c>
2497   <c>Referer</c>
2498   <c>http</c>
2499   <c>standard</c>
2500   <c>
2501      <xref target="header.referer"/>
2502   </c>
2503   <c>Retry-After</c>
2504   <c>http</c>
2505   <c>standard</c>
2506   <c>
2507      <xref target="header.retry-after"/>
2508   </c>
2509   <c>Server</c>
2510   <c>http</c>
2511   <c>standard</c>
2512   <c>
2513      <xref target="header.server"/>
2514   </c>
2515   <c>User-Agent</c>
2516   <c>http</c>
2517   <c>standard</c>
2518   <c>
2519      <xref target="header.user-agent"/>
2520   </c>
2521</texttable>
2522<!--(END)-->
2523<t>
2524   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2525</t>
2526</section>
2527</section>
2528
2529<section title="Security Considerations" anchor="security.considerations">
2530<t>
2531   This section is meant to inform application developers, information
2532   providers, and users of the security limitations in HTTP/1.1 as
2533   described by this document. The discussion does not include
2534   definitive solutions to the problems revealed, though it does make
2535   some suggestions for reducing security risks.
2536</t>
2537
2538<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2539<t>
2540   Like any generic data transfer protocol, HTTP cannot regulate the
2541   content of the data that is transferred, nor is there any a priori
2542   method of determining the sensitivity of any particular piece of
2543   information within the context of any given request. Therefore,
2544   applications &SHOULD; supply as much control over this information as
2545   possible to the provider of that information. Four header fields are
2546   worth special mention in this context: Server, Via, Referer and From.
2547</t>
2548<t>
2549   Revealing the specific software version of the server might allow the
2550   server machine to become more vulnerable to attacks against software
2551   that is known to contain security holes. Implementors &SHOULD; make the
2552   Server header field a configurable option.
2553</t>
2554<t>
2555   Proxies which serve as a portal through a network firewall &SHOULD;
2556   take special precautions regarding the transfer of header information
2557   that identifies the hosts behind the firewall. In particular, they
2558   &SHOULD; remove, or replace with sanitized versions, any Via fields
2559   generated behind the firewall.
2560</t>
2561<t>
2562   The Referer header allows reading patterns to be studied and reverse
2563   links drawn. Although it can be very useful, its power can be abused
2564   if user details are not separated from the information contained in
2565   the Referer. Even when the personal information has been removed, the
2566   Referer header might indicate a private document's URI whose
2567   publication would be inappropriate.
2568</t>
2569<t>
2570   The information sent in the From field might conflict with the user's
2571   privacy interests or their site's security policy, and hence it
2572   &SHOULD-NOT;  be transmitted without the user being able to disable,
2573   enable, and modify the contents of the field. The user &MUST; be able
2574   to set the contents of this field within a user preference or
2575   application defaults configuration.
2576</t>
2577<t>
2578   We suggest, though do not require, that a convenient toggle interface
2579   be provided for the user to enable or disable the sending of From and
2580   Referer information.
2581</t>
2582<t>
2583   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2584   fields can sometimes be used to determine that a specific client or
2585   server have a particular security hole which might be exploited.
2586   Unfortunately, this same information is often used for other valuable
2587   purposes for which HTTP currently has no better mechanism.
2588</t>
2589</section>
2590
2591<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2592<t>
2593   Because the source of a link might be private information or might
2594   reveal an otherwise private information source, it is strongly
2595   recommended that the user be able to select whether or not the
2596   Referer field is sent. For example, a browser client could have a
2597   toggle switch for browsing openly/anonymously, which would
2598   respectively enable/disable the sending of Referer and From
2599   information.
2600</t>
2601<t>
2602   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2603   HTTP request if the referring page was transferred with a secure
2604   protocol.
2605</t>
2606<t>
2607   Authors of services should not use
2608   GET-based forms for the submission of sensitive data because that
2609   data will be encoded in the Request-target. Many existing
2610   servers, proxies, and user agents log or display the Request-target in
2611   places where it might be visible to third parties. Such services can
2612   use POST-based form submission instead.
2613</t>
2614</section>
2615
2616<section title="Location Headers and Spoofing" anchor="location.spoofing">
2617<t>
2618   If a single server supports multiple organizations that do not trust
2619   one another, then it &MUST; check the values of Location and Content-Location
2620   headers in responses that are generated under control of
2621   said organizations to make sure that they do not attempt to
2622   invalidate resources over which they have no authority.
2623</t>
2624</section>
2625
2626</section>
2627
2628<section title="Acknowledgments" anchor="ack">
2629</section>
2630</middle>
2631<back>
2632
2633<references title="Normative References">
2634
2635<reference anchor="Part1">
2636  <front>
2637    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2638    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2639      <organization abbrev="Day Software">Day Software</organization>
2640      <address><email>fielding@gbiv.com</email></address>
2641    </author>
2642    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2643      <organization>One Laptop per Child</organization>
2644      <address><email>jg@laptop.org</email></address>
2645    </author>
2646    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2647      <organization abbrev="HP">Hewlett-Packard Company</organization>
2648      <address><email>JeffMogul@acm.org</email></address>
2649    </author>
2650    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2651      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2652      <address><email>henrikn@microsoft.com</email></address>
2653    </author>
2654    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2655      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2656      <address><email>LMM@acm.org</email></address>
2657    </author>
2658    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2659      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2660      <address><email>paulle@microsoft.com</email></address>
2661    </author>
2662    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2663      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2664      <address><email>timbl@w3.org</email></address>
2665    </author>
2666    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2667      <organization abbrev="W3C">World Wide Web Consortium</organization>
2668      <address><email>ylafon@w3.org</email></address>
2669    </author>
2670    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2671      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2672      <address><email>julian.reschke@greenbytes.de</email></address>
2673    </author>
2674    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2675  </front>
2676  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2677  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2678</reference>
2679
2680<reference anchor="Part3">
2681  <front>
2682    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2683    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2684      <organization abbrev="Day Software">Day Software</organization>
2685      <address><email>fielding@gbiv.com</email></address>
2686    </author>
2687    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2688      <organization>One Laptop per Child</organization>
2689      <address><email>jg@laptop.org</email></address>
2690    </author>
2691    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2692      <organization abbrev="HP">Hewlett-Packard Company</organization>
2693      <address><email>JeffMogul@acm.org</email></address>
2694    </author>
2695    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2696      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2697      <address><email>henrikn@microsoft.com</email></address>
2698    </author>
2699    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2700      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2701      <address><email>LMM@acm.org</email></address>
2702    </author>
2703    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2704      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2705      <address><email>paulle@microsoft.com</email></address>
2706    </author>
2707    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2708      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2709      <address><email>timbl@w3.org</email></address>
2710    </author>
2711    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2712      <organization abbrev="W3C">World Wide Web Consortium</organization>
2713      <address><email>ylafon@w3.org</email></address>
2714    </author>
2715    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2716      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2717      <address><email>julian.reschke@greenbytes.de</email></address>
2718    </author>
2719    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2720  </front>
2721  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2722  <x:source href="p3-payload.xml" basename="p3-payload"/>
2723</reference>
2724
2725<reference anchor="Part4">
2726  <front>
2727    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2728    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2729      <organization abbrev="Day Software">Day Software</organization>
2730      <address><email>fielding@gbiv.com</email></address>
2731    </author>
2732    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2733      <organization>One Laptop per Child</organization>
2734      <address><email>jg@laptop.org</email></address>
2735    </author>
2736    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2737      <organization abbrev="HP">Hewlett-Packard Company</organization>
2738      <address><email>JeffMogul@acm.org</email></address>
2739    </author>
2740    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2741      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2742      <address><email>henrikn@microsoft.com</email></address>
2743    </author>
2744    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2745      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2746      <address><email>LMM@acm.org</email></address>
2747    </author>
2748    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2749      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2750      <address><email>paulle@microsoft.com</email></address>
2751    </author>
2752    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2753      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2754      <address><email>timbl@w3.org</email></address>
2755    </author>
2756    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2757      <organization abbrev="W3C">World Wide Web Consortium</organization>
2758      <address><email>ylafon@w3.org</email></address>
2759    </author>
2760    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2761      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2762      <address><email>julian.reschke@greenbytes.de</email></address>
2763    </author>
2764    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2765  </front>
2766  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2767  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2768</reference>
2769
2770<reference anchor="Part5">
2771  <front>
2772    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2773    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2774      <organization abbrev="Day Software">Day Software</organization>
2775      <address><email>fielding@gbiv.com</email></address>
2776    </author>
2777    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2778      <organization>One Laptop per Child</organization>
2779      <address><email>jg@laptop.org</email></address>
2780    </author>
2781    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2782      <organization abbrev="HP">Hewlett-Packard Company</organization>
2783      <address><email>JeffMogul@acm.org</email></address>
2784    </author>
2785    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2786      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2787      <address><email>henrikn@microsoft.com</email></address>
2788    </author>
2789    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2790      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2791      <address><email>LMM@acm.org</email></address>
2792    </author>
2793    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2794      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2795      <address><email>paulle@microsoft.com</email></address>
2796    </author>
2797    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2798      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2799      <address><email>timbl@w3.org</email></address>
2800    </author>
2801    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2802      <organization abbrev="W3C">World Wide Web Consortium</organization>
2803      <address><email>ylafon@w3.org</email></address>
2804    </author>
2805    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2806      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2807      <address><email>julian.reschke@greenbytes.de</email></address>
2808    </author>
2809    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2810  </front>
2811  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
2812  <x:source href="p5-range.xml" basename="p5-range"/>
2813</reference>
2814
2815<reference anchor="Part6">
2816  <front>
2817    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2818    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2819      <organization abbrev="Day Software">Day Software</organization>
2820      <address><email>fielding@gbiv.com</email></address>
2821    </author>
2822    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2823      <organization>One Laptop per Child</organization>
2824      <address><email>jg@laptop.org</email></address>
2825    </author>
2826    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2827      <organization abbrev="HP">Hewlett-Packard Company</organization>
2828      <address><email>JeffMogul@acm.org</email></address>
2829    </author>
2830    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2831      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2832      <address><email>henrikn@microsoft.com</email></address>
2833    </author>
2834    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2835      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2836      <address><email>LMM@acm.org</email></address>
2837    </author>
2838    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2839      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2840      <address><email>paulle@microsoft.com</email></address>
2841    </author>
2842    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2843      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2844      <address><email>timbl@w3.org</email></address>
2845    </author>
2846    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2847      <organization abbrev="W3C">World Wide Web Consortium</organization>
2848      <address><email>ylafon@w3.org</email></address>
2849    </author>
2850    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2851      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2852      <address><email>julian.reschke@greenbytes.de</email></address>
2853    </author>
2854    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2855  </front>
2856  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2857  <x:source href="p6-cache.xml" basename="p6-cache"/>
2858</reference>
2859
2860<reference anchor="Part7">
2861  <front>
2862    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2863    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2864      <organization abbrev="Day Software">Day Software</organization>
2865      <address><email>fielding@gbiv.com</email></address>
2866    </author>
2867    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2868      <organization>One Laptop per Child</organization>
2869      <address><email>jg@laptop.org</email></address>
2870    </author>
2871    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2872      <organization abbrev="HP">Hewlett-Packard Company</organization>
2873      <address><email>JeffMogul@acm.org</email></address>
2874    </author>
2875    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2876      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2877      <address><email>henrikn@microsoft.com</email></address>
2878    </author>
2879    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2880      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2881      <address><email>LMM@acm.org</email></address>
2882    </author>
2883    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2884      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2885      <address><email>paulle@microsoft.com</email></address>
2886    </author>
2887    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2888      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2889      <address><email>timbl@w3.org</email></address>
2890    </author>
2891    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2892      <organization abbrev="W3C">World Wide Web Consortium</organization>
2893      <address><email>ylafon@w3.org</email></address>
2894    </author>
2895    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2896      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2897      <address><email>julian.reschke@greenbytes.de</email></address>
2898    </author>
2899    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2900  </front>
2901  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
2902  <x:source href="p7-auth.xml" basename="p7-auth"/>
2903</reference>
2904
2905<reference anchor="RFC2119">
2906  <front>
2907    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2908    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2909      <organization>Harvard University</organization>
2910      <address><email>sob@harvard.edu</email></address>
2911    </author>
2912    <date month="March" year="1997"/>
2913  </front>
2914  <seriesInfo name="BCP" value="14"/>
2915  <seriesInfo name="RFC" value="2119"/>
2916</reference>
2917
2918<reference anchor="RFC5234">
2919  <front>
2920    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
2921    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
2922      <organization>Brandenburg InternetWorking</organization>
2923      <address>
2924      <postal>
2925      <street>675 Spruce Dr.</street>
2926      <city>Sunnyvale</city>
2927      <region>CA</region>
2928      <code>94086</code>
2929      <country>US</country></postal>
2930      <phone>+1.408.246.8253</phone>
2931      <email>dcrocker@bbiw.net</email></address> 
2932    </author>
2933    <author initials="P." surname="Overell" fullname="Paul Overell">
2934      <organization>THUS plc.</organization>
2935      <address>
2936      <postal>
2937      <street>1/2 Berkeley Square</street>
2938      <street>99 Berkely Street</street>
2939      <city>Glasgow</city>
2940      <code>G3 7HR</code>
2941      <country>UK</country></postal>
2942      <email>paul.overell@thus.net</email></address>
2943    </author>
2944    <date month="January" year="2008"/>
2945  </front>
2946  <seriesInfo name="STD" value="68"/>
2947  <seriesInfo name="RFC" value="5234"/>
2948</reference>
2949
2950</references>
2951
2952<references title="Informative References">
2953
2954<reference anchor="RFC1945">
2955  <front>
2956    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2957    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2958      <organization>MIT, Laboratory for Computer Science</organization>
2959      <address><email>timbl@w3.org</email></address>
2960    </author>
2961    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2962      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2963      <address><email>fielding@ics.uci.edu</email></address>
2964    </author>
2965    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2966      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2967      <address><email>frystyk@w3.org</email></address>
2968    </author>
2969    <date month="May" year="1996"/>
2970  </front>
2971  <seriesInfo name="RFC" value="1945"/>
2972</reference>
2973
2974<reference anchor="RFC2068">
2975  <front>
2976    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2977    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2978      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2979      <address><email>fielding@ics.uci.edu</email></address>
2980    </author>
2981    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2982      <organization>MIT Laboratory for Computer Science</organization>
2983      <address><email>jg@w3.org</email></address>
2984    </author>
2985    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2986      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2987      <address><email>mogul@wrl.dec.com</email></address>
2988    </author>
2989    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2990      <organization>MIT Laboratory for Computer Science</organization>
2991      <address><email>frystyk@w3.org</email></address>
2992    </author>
2993    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2994      <organization>MIT Laboratory for Computer Science</organization>
2995      <address><email>timbl@w3.org</email></address>
2996    </author>
2997    <date month="January" year="1997"/>
2998  </front>
2999  <seriesInfo name="RFC" value="2068"/>
3000</reference>
3001
3002<reference anchor="RFC2616">
3003  <front>
3004    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3005    <author initials="R." surname="Fielding" fullname="R. Fielding">
3006      <organization>University of California, Irvine</organization>
3007      <address><email>fielding@ics.uci.edu</email></address>
3008    </author>
3009    <author initials="J." surname="Gettys" fullname="J. Gettys">
3010      <organization>W3C</organization>
3011      <address><email>jg@w3.org</email></address>
3012    </author>
3013    <author initials="J." surname="Mogul" fullname="J. Mogul">
3014      <organization>Compaq Computer Corporation</organization>
3015      <address><email>mogul@wrl.dec.com</email></address>
3016    </author>
3017    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3018      <organization>MIT Laboratory for Computer Science</organization>
3019      <address><email>frystyk@w3.org</email></address>
3020    </author>
3021    <author initials="L." surname="Masinter" fullname="L. Masinter">
3022      <organization>Xerox Corporation</organization>
3023      <address><email>masinter@parc.xerox.com</email></address>
3024    </author>
3025    <author initials="P." surname="Leach" fullname="P. Leach">
3026      <organization>Microsoft Corporation</organization>
3027      <address><email>paulle@microsoft.com</email></address>
3028    </author>
3029    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3030      <organization>W3C</organization>
3031      <address><email>timbl@w3.org</email></address>
3032    </author>
3033    <date month="June" year="1999"/>
3034  </front>
3035  <seriesInfo name="RFC" value="2616"/>
3036</reference>
3037
3038<reference anchor='RFC2817'>
3039  <front>
3040    <title>Upgrading to TLS Within HTTP/1.1</title>
3041    <author initials='R.' surname='Khare' fullname='R. Khare'>
3042      <organization>4K Associates / UC Irvine</organization>
3043      <address><email>rohit@4K-associates.com</email></address>
3044    </author>
3045    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3046      <organization>Agranat Systems, Inc.</organization>
3047      <address><email>lawrence@agranat.com</email></address>
3048    </author>
3049    <date year='2000' month='May' />
3050  </front>
3051  <seriesInfo name='RFC' value='2817' />
3052</reference>
3053
3054<reference anchor='RFC3864'>
3055  <front>
3056    <title>Registration Procedures for Message Header Fields</title>
3057    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3058      <organization>Nine by Nine</organization>
3059      <address><email>GK-IETF@ninebynine.org</email></address>
3060    </author>
3061    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3062      <organization>BEA Systems</organization>
3063      <address><email>mnot@pobox.com</email></address>
3064    </author>
3065    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3066      <organization>HP Labs</organization>
3067      <address><email>JeffMogul@acm.org</email></address>
3068    </author>
3069    <date year='2004' month='September' />
3070  </front>
3071  <seriesInfo name='BCP' value='90' />
3072  <seriesInfo name='RFC' value='3864' />
3073</reference>
3074
3075<reference anchor='RFC5226'>
3076  <front>
3077    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3078    <author initials='T.' surname='Narten' fullname='T. Narten'>
3079      <organization>IBM</organization>
3080      <address><email>narten@us.ibm.com</email></address>
3081    </author>
3082    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3083      <organization>Google</organization>
3084      <address><email>Harald@Alvestrand.no</email></address>
3085    </author>
3086    <date year='2008' month='May' />
3087  </front>
3088  <seriesInfo name='BCP' value='26' />
3089  <seriesInfo name='RFC' value='5226' />
3090</reference>
3091
3092<reference anchor="RFC5322">
3093  <front>
3094    <title>Internet Message Format</title>
3095    <author initials="P." surname="Resnick" fullname="P. Resnick">
3096      <organization>Qualcomm Incorporated</organization>
3097    </author>
3098    <date year="2008" month="October"/>
3099  </front> 
3100  <seriesInfo name="RFC" value="5322"/>
3101</reference>
3102
3103</references>
3104
3105<section title="Compatibility with Previous Versions" anchor="compatibility">
3106<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
3107<t>
3108   Clarified which error code should be used for inbound server failures
3109   (e.g. DNS failures). (<xref target="status.504"/>).
3110</t>
3111<t>
3112   201 (Created) had a race that required an Etag be sent when a resource is
3113   first created. (<xref target="status.201"/>).
3114</t>
3115<t>
3116   Rewrite of message transmission requirements to make it much harder
3117   for implementors to get it wrong, as the consequences of errors here
3118   can have significant impact on the Internet, and to deal with the
3119   following problems:
3120  <list style="numbers">
3121      <t>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
3122         this was incorrectly placing a requirement on the behavior of
3123         an implementation of a future version of HTTP/1.x</t>
3124
3125      <t>Made it clear that user-agents should retry requests, not
3126         "clients" in general.</t>
3127
3128      <t>Converted requirements for clients to ignore unexpected 100
3129         (Continue) responses, and for proxies to forward 100 responses,
3130         into a general requirement for 1xx responses.</t>
3131
3132      <t>Modified some TCP-specific language, to make it clearer that
3133         non-TCP transports are possible for HTTP.</t>
3134
3135      <t>Require that the origin server &MUST-NOT; wait for the request
3136         body before it sends a required 100 (Continue) response.</t>
3137
3138      <t>Allow, rather than require, a server to omit 100 (Continue) if
3139         it has already seen some of the request body.</t>
3140
3141      <t>Allow servers to defend against denial-of-service attacks and
3142         broken clients.</t>
3143  </list>
3144</t>
3145<t>
3146   This change adds the Expect header and 417 status code.
3147</t>
3148<t>
3149   Clean up confusion between 403 and 404 responses. (Section <xref target="status.403" format="counter"/>,
3150   <xref target="status.404" format="counter"/>, and <xref target="status.410" format="counter"/>)
3151</t>
3152<t>
3153   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
3154   implemented in previous versions of this specification. See <xref target="RFC2068" x:fmt="of" x:sec="19.6.1"/>.
3155</t>
3156</section>
3157
3158<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3159<t>
3160  This document takes over the Status Code Registry, previously defined
3161  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3162  (<xref target="status.code.registry"/>)
3163</t>
3164<t>
3165  Clarify definition of POST.
3166  (<xref target="POST"/>)
3167</t>
3168<t>
3169  Failed to consider that there are
3170  many other request methods that are safe to automatically redirect,
3171  and further that the user agent is able to make that determination
3172  based on the request method semantics.
3173  (Sections <xref format="counter" target="status.301"/>,
3174  <xref format="counter" target="status.302"/> and
3175  <xref format="counter" target="status.307"/>)
3176</t>
3177<t>
3178  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3179  It used to indicate that the requested resource must be accessed through the
3180  proxy given by the Location field. The Location field gave the URI of the
3181  proxy. The recipient was expected to repeat this single request via the proxy.
3182  (<xref target="status.305"/>)
3183</t>
3184<t>
3185  Reclassify Allow header as response header, removing the option to
3186  specify it in a PUT request.
3187  Relax the server requirement on the contents of the Allow header and
3188  remove requirement on clients to always trust the header value.
3189  (<xref target="header.allow"/>)
3190</t>
3191<t>
3192  Correct syntax of Location header to allow fragment,
3193  as referred symbol wasn't what was expected, and add some
3194  clarifications as to when it would not be appropriate.
3195  (<xref target="header.location"/>)
3196</t>
3197<t>
3198  In the description of the Server header, the Via field
3199  was described as a SHOULD. The requirement was and is stated
3200  correctly in the description of the Via header in &header-via;.
3201  (<xref target="header.server"/>)
3202</t>
3203</section>
3204
3205</section>
3206
3207<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3208<figure>
3209<artwork type="abnf" name="p2-semantics.parsed-abnf">
3210<x:ref>Accept</x:ref> = &lt;Accept, defined in [Part3], Section 5.1&gt;
3211<x:ref>Accept-Charset</x:ref> = &lt;Accept-Charset, defined in [Part3], Section 5.2&gt;
3212<x:ref>Accept-Encoding</x:ref> = &lt;Accept-Encoding, defined in [Part3], Section 5.3&gt;
3213<x:ref>Accept-Language</x:ref> = &lt;Accept-Language, defined in [Part3], Section 5.4&gt;
3214<x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in [Part5], Section 5.1&gt;
3215<x:ref>Age</x:ref> = &lt;Age, defined in [Part6], Section 3.1&gt;
3216<x:ref>Allow</x:ref> = "Allow:" OWS Allow-v
3217<x:ref>Allow-v</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3218<x:ref>Authorization</x:ref> = &lt;Authorization, defined in [Part7], Section 3.1&gt;
3219
3220<x:ref>ETag</x:ref> = &lt;ETag, defined in [Part4], Section 6.1&gt;
3221<x:ref>Expect</x:ref> = "Expect:" OWS Expect-v
3222<x:ref>Expect-v</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3223
3224<x:ref>From</x:ref> = "From:" OWS From-v
3225<x:ref>From-v</x:ref> = mailbox
3226
3227<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 3.2.1&gt;
3228<x:ref>Host</x:ref> = &lt;Host, defined in [Part1], Section 2.1&gt;
3229
3230<x:ref>If-Match</x:ref> = &lt;If-Match, defined in [Part4], Section 6.2&gt;
3231If-Modified-Since =
3232 &lt;If-Modified-Since, defined in [Part4], Section 6.3&gt;
3233<x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in [Part4], Section 6.4&gt;
3234<x:ref>If-Range</x:ref> = &lt;If-Range, defined in [Part5], Section 5.3&gt;
3235If-Unmodified-Since =
3236 &lt;If-Unmodified-Since, defined in [Part4], Section 6.5&gt;
3237
3238<x:ref>Location</x:ref> = "Location:" OWS Location-v
3239<x:ref>Location-v</x:ref> = absolute-URI [ "#" fragment ]
3240
3241<x:ref>Max-Forwards</x:ref> = "Max-Forwards:" OWS Max-Forwards-v
3242<x:ref>Max-Forwards-v</x:ref> = 1*DIGIT
3243<x:ref>Method</x:ref> = %x4F.50.54.49.4F.4E.53 / %x47.45.54 / %x48.45.41.44 /
3244 %x50.4F.54 / %x50.55.54 / %x44.45.4C.45.54.45 / %x54.52.41.43.45 /
3245 %x43.4E.4E.45.43.54 / extension-method
3246
3247<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
3248
3249Proxy-Authenticate =
3250 &lt;Proxy-Authenticate, defined in [Part7], Section 3.2&gt;
3251Proxy-Authorization =
3252 &lt;Proxy-Authorization, defined in [Part7], Section 3.3&gt;
3253
3254<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3255<x:ref>Range</x:ref> = &lt;Range, defined in [Part5], Section 5.4&gt;
3256<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
3257<x:ref>Referer</x:ref> = "Referer:" OWS Referer-v
3258<x:ref>Referer-v</x:ref> = absolute-URI / partial-URI
3259<x:ref>Retry-After</x:ref> = "Retry-After:" OWS Retry-After-v
3260<x:ref>Retry-After-v</x:ref> = HTTP-date / delta-seconds
3261
3262<x:ref>Server</x:ref> = "Server:" OWS Server-v
3263<x:ref>Server-v</x:ref> = product *( RWS ( product / comment ) )
3264<x:ref>Status-Code</x:ref> = "100" / "101" / "200" / "201" / "202" / "203" / "204" /
3265 "205" / "206" / "300" / "301" / "302" / "303" / "304" / "305" /
3266 "307" / "400" / "401" / "402" / "403" / "404" / "405" / "406" /
3267 "407" / "408" / "409" / "410" / "411" / "412" / "413" / "414" /
3268 "415" / "416" / "417" / "500" / "501" / "502" / "503" / "504" /
3269 "505" / extension-code
3270
3271<x:ref>TE</x:ref> = &lt;TE, defined in [Part1], Section 8.8&gt;
3272
3273<x:ref>User-Agent</x:ref> = "User-Agent:" OWS User-Agent-v
3274<x:ref>User-Agent-v</x:ref> = product *( RWS ( product / comment ) )
3275
3276<x:ref>Vary</x:ref> = &lt;Vary, defined in [Part6], Section 3.5&gt;
3277
3278WWW-Authenticate =
3279 &lt;WWW-Authenticate, defined in [Part7], Section 3.4&gt;
3280
3281<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.1&gt;
3282
3283<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 1.2.2&gt;
3284
3285<x:ref>delta-seconds</x:ref> = 1*DIGIT
3286
3287<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
3288<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
3289<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
3290 *expect-params ]
3291<x:ref>extension-code</x:ref> = 3DIGIT
3292<x:ref>extension-method</x:ref> = token
3293
3294<x:ref>fragment</x:ref> = &lt;fragment, defined in [Part1], Section 2.1&gt;
3295
3296<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
3297
3298<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
3299
3300<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.1&gt;
3301<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 3.4&gt;
3302
3303<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
3304
3305<x:ref>request-header</x:ref> = Accept / Accept-Charset / Accept-Encoding /
3306 Accept-Language / Authorization / Expect / From / Host / If-Match /
3307 If-Modified-Since / If-None-Match / If-Range / If-Unmodified-Since /
3308 Max-Forwards / Proxy-Authorization / Range / Referer / TE /
3309 User-Agent
3310<x:ref>response-header</x:ref> = Accept-Ranges / Age / Allow / ETag / Location /
3311 Proxy-Authenticate / Retry-After / Server / Vary / WWW-Authenticate
3312
3313<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
3314
3315
3316</artwork>
3317</figure>
3318<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
3319; Reason-Phrase defined but not used
3320; Status-Code defined but not used
3321; request-header defined but not used
3322; response-header defined but not used
3323</artwork></figure></section>
3324
3325<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3326
3327<section title="Since RFC2616">
3328<t>
3329  Extracted relevant partitions from <xref target="RFC2616"/>.
3330</t>
3331</section>
3332
3333<section title="Since draft-ietf-httpbis-p2-semantics-00">
3334<t>
3335  Closed issues:
3336  <list style="symbols"> 
3337    <t>
3338      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3339      "Via is a MUST"
3340      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3341    </t>
3342    <t>
3343      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3344      "Fragments allowed in Location"
3345      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3346    </t>
3347    <t>
3348      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3349      "Safe Methods vs Redirection"
3350      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3351    </t>
3352    <t>
3353      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3354      "Revise description of the POST method"
3355      (<eref target="http://purl.org/NET/http-errata#post"/>)
3356    </t>
3357    <t>
3358      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3359      "Normative and Informative references"
3360    </t>
3361    <t>
3362      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3363      "RFC2606 Compliance"
3364    </t>
3365    <t>
3366      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3367      "Informative references"
3368    </t>
3369    <t>
3370      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3371      "Redundant cross-references"
3372    </t>
3373  </list>
3374</t>
3375<t>
3376  Other changes:
3377  <list style="symbols"> 
3378    <t>
3379      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3380    </t>
3381  </list>
3382</t>
3383</section>
3384
3385<section title="Since draft-ietf-httpbis-p2-semantics-01">
3386<t>
3387  Closed issues:
3388  <list style="symbols"> 
3389    <t>
3390      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3391      "PUT side effects"
3392    </t>
3393    <t>
3394      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3395      "Duplicate Host header requirements"
3396    </t>
3397  </list>
3398</t>
3399<t>
3400  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3401  <list style="symbols"> 
3402    <t>
3403      Move "Product Tokens" section (back) into Part 1, as "token" is used
3404      in the definition of the Upgrade header.
3405    </t>
3406    <t>
3407      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3408    </t>
3409    <t>
3410      Copy definition of delta-seconds from Part6 instead of referencing it.
3411    </t>
3412  </list>
3413</t>
3414</section>
3415
3416<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3417<t>
3418  Closed issues:
3419  <list style="symbols"> 
3420    <t>
3421      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3422      "Requiring Allow in 405 responses"
3423    </t>
3424    <t>
3425      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3426      "Status Code Registry"
3427    </t>
3428    <t>
3429      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3430      "Redirection vs. Location"
3431    </t>
3432    <t>
3433      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3434      "Cacheability of 303 response"
3435    </t>
3436    <t>
3437      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3438      "305 Use Proxy"
3439    </t>
3440    <t>
3441      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3442      "Classification for Allow header"
3443    </t>
3444    <t>
3445      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3446      "PUT - 'store under' vs 'store at'"
3447    </t>
3448  </list>
3449</t>
3450<t>
3451  Ongoing work on IANA Message Header Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3452  <list style="symbols"> 
3453    <t>
3454      Reference RFC 3984, and update header registrations for headers defined
3455      in this document.
3456    </t>
3457  </list>
3458</t>
3459<t>
3460  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3461  <list style="symbols"> 
3462    <t>
3463      Replace string literals when the string really is case-sensitive (method).
3464    </t>
3465  </list>
3466</t>
3467</section>
3468
3469<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3470<t>
3471  Closed issues:
3472  <list style="symbols"> 
3473    <t>
3474      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
3475      "OPTIONS request bodies"
3476    </t>
3477    <t>
3478      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
3479      "Description of CONNECT should refer to RFC2817"
3480    </t>
3481    <t>
3482      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
3483      "Location Content-Location reference request/response mixup"
3484    </t>
3485  </list>
3486</t>
3487<t>
3488  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
3489  <list style="symbols"> 
3490    <t>
3491      Added initial proposal for registration process, plus initial
3492      content (non-HTTP/1.1 methods to be added by a separate specification).
3493    </t>
3494  </list>
3495</t>
3496</section>
3497
3498<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3499<t>
3500  Closed issues:
3501  <list style="symbols"> 
3502    <t>
3503      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3504      "Content-*"
3505    </t>
3506    <t>
3507      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3508      "RFC 2822 is updated by RFC 5322"
3509    </t>
3510  </list>
3511</t>
3512<t>
3513  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3514  <list style="symbols"> 
3515    <t>
3516      Use "/" instead of "|" for alternatives.
3517    </t>
3518    <t>
3519      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3520      whitespace ("OWS") and required whitespace ("RWS").
3521    </t>
3522    <t>
3523      Rewrite ABNFs to spell out whitespace rules, factor out
3524      header value format definitions.
3525    </t>
3526  </list>
3527</t>
3528</section>
3529
3530<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3531<t>
3532  Closed issues:
3533  <list style="symbols"> 
3534    <t>
3535      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
3536      "Reason-Phrase BNF"
3537    </t>
3538  </list>
3539</t>
3540<t>
3541  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3542  <list style="symbols"> 
3543    <t>
3544      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3545    </t>
3546  </list>
3547</t>
3548</section>
3549
3550</section>
3551
3552</back>
3553</rfc>
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