source: draft-ietf-httpbis/latest/p2-semantics.xml @ 1368

Last change on this file since 1368 was 1368, checked in by julian.reschke@…, 8 years ago

bump up document dates; update to latest version of rfc2629.xslt.

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1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD NOT</bcp14>">
14  <!ENTITY ID-VERSION "latest">
15  <!ENTITY ID-MONTH "August">
16  <!ENTITY ID-YEAR "2011">
17  <!ENTITY mdash "&#8212;">
18  <!ENTITY notation                   "<xref target='Part1' x:rel='#notation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
19  <!ENTITY acks                       "<xref target='Part1' x:rel='#acks' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY messaging                  "<xref target='Part1' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY payload                    "<xref target='Part3' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY conditional                "<xref target='Part4' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23  <!ENTITY range                      "<xref target='Part5' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
24  <!ENTITY caching                    "<xref target='Part6' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
25  <!ENTITY auth                       "<xref target='Part7' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
26  <!ENTITY combining-responses        "<xref target='Part6' x:rel='#combining.responses' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
27  <!ENTITY content-negotiation        "<xref target='Part3' x:rel='#content.negotiation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
28  <!ENTITY notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
29  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY uri                        "<xref target='Part1' x:rel='#uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY effective-request-uri      "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY intermediaries             "<xref target='Part1' x:rel='#intermediaries' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY full-date                  "<xref target='Part1' x:rel='#date.time.formats.full.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY request-target             "<xref target='Part1' x:rel='#request-target' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
42  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
43  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
44  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
45  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
46  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
47  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
48  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
49  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
50  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
51  <!ENTITY header-fields              "<xref target='Part1' x:rel='#header.fields' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
52  <!ENTITY header-host                "<xref target='Part1' x:rel='#header.host' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
53  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
54  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
55  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
56  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
57  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
58  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
59  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
60  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
61  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
62  <!ENTITY header-upgrade             "<xref target='Part1' x:rel='#header.upgrade' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
63  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.te' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
64  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
65  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
66  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
67  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
68  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
69  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
70  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='#internet.media.type.message.http' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
71  <!ENTITY status-206                 "<xref target='Part5' x:rel='#status.206' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
72  <!ENTITY status-304                 "<xref target='Part4' x:rel='#status.304' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
73  <!ENTITY status-401                 "<xref target='Part7' x:rel='#status.401' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
74  <!ENTITY status-407                 "<xref target='Part7' x:rel='#status.407' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
75  <!ENTITY status-412                 "<xref target='Part4' x:rel='#status.412' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
76  <!ENTITY status-416                 "<xref target='Part5' x:rel='#status.416' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
77  <!ENTITY p3-header-fields           "<xref target='Part3' x:rel='#header.fields' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
78  <!ENTITY p4-status-codes            "<xref target='Part4' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
79  <!ENTITY p5-status-codes            "<xref target='Part5' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
80  <!ENTITY p7-status-codes            "<xref target='Part7' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
81  <!ENTITY p6-heuristic               "<xref target='Part6' x:rel='#heuristic.freshness' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
82  <!ENTITY p6-explicit                "<xref target='Part6' x:rel='#calculating.freshness.lifetime' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
83  <!ENTITY p6-invalid                 "<xref target='Part6' x:rel='#invalidation.after.updates.or.deletions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
84]>
85<?rfc toc="yes" ?>
86<?rfc symrefs="yes" ?>
87<?rfc sortrefs="yes" ?>
88<?rfc compact="yes"?>
89<?rfc subcompact="no" ?>
90<?rfc linkmailto="no" ?>
91<?rfc editing="no" ?>
92<?rfc comments="yes"?>
93<?rfc inline="yes"?>
94<?rfc rfcedstyle="yes"?>
95<?rfc-ext allow-markup-in-artwork="yes" ?>
96<?rfc-ext include-references-in-index="yes" ?>
97<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
98     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
99     xmlns:x='http://purl.org/net/xml2rfc/ext'
100     xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
101<front>
102
103  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
104
105  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
106    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
107    <address>
108      <postal>
109        <street>345 Park Ave</street>
110        <city>San Jose</city>
111        <region>CA</region>
112        <code>95110</code>
113        <country>USA</country>
114      </postal>
115      <email>fielding@gbiv.com</email>
116      <uri>http://roy.gbiv.com/</uri>
117    </address>
118  </author>
119
120  <author initials="J." surname="Gettys" fullname="Jim Gettys">
121    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
122    <address>
123      <postal>
124        <street>21 Oak Knoll Road</street>
125        <city>Carlisle</city>
126        <region>MA</region>
127        <code>01741</code>
128        <country>USA</country>
129      </postal>
130      <email>jg@freedesktop.org</email>
131      <uri>http://gettys.wordpress.com/</uri>
132    </address>
133  </author>
134 
135  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
136    <organization abbrev="HP">Hewlett-Packard Company</organization>
137    <address>
138      <postal>
139        <street>HP Labs, Large Scale Systems Group</street>
140        <street>1501 Page Mill Road, MS 1177</street>
141        <city>Palo Alto</city>
142        <region>CA</region>
143        <code>94304</code>
144        <country>USA</country>
145      </postal>
146      <email>JeffMogul@acm.org</email>
147    </address>
148  </author>
149
150  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
151    <organization abbrev="Microsoft">Microsoft Corporation</organization>
152    <address>
153      <postal>
154        <street>1 Microsoft Way</street>
155        <city>Redmond</city>
156        <region>WA</region>
157        <code>98052</code>
158        <country>USA</country>
159      </postal>
160      <email>henrikn@microsoft.com</email>
161    </address>
162  </author>
163
164  <author initials="L." surname="Masinter" fullname="Larry Masinter">
165    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
166    <address>
167      <postal>
168        <street>345 Park Ave</street>
169        <city>San Jose</city>
170        <region>CA</region>
171        <code>95110</code>
172        <country>USA</country>
173      </postal>
174      <email>LMM@acm.org</email>
175      <uri>http://larry.masinter.net/</uri>
176    </address>
177  </author>
178 
179  <author initials="P." surname="Leach" fullname="Paul J. Leach">
180    <organization abbrev="Microsoft">Microsoft Corporation</organization>
181    <address>
182      <postal>
183        <street>1 Microsoft Way</street>
184        <city>Redmond</city>
185        <region>WA</region>
186        <code>98052</code>
187      </postal>
188      <email>paulle@microsoft.com</email>
189    </address>
190  </author>
191   
192  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
193    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
194    <address>
195      <postal>
196        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
197        <street>The Stata Center, Building 32</street>
198        <street>32 Vassar Street</street>
199        <city>Cambridge</city>
200        <region>MA</region>
201        <code>02139</code>
202        <country>USA</country>
203      </postal>
204      <email>timbl@w3.org</email>
205      <uri>http://www.w3.org/People/Berners-Lee/</uri>
206    </address>
207  </author>
208
209  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
210    <organization abbrev="W3C">World Wide Web Consortium</organization>
211    <address>
212      <postal>
213        <street>W3C / ERCIM</street>
214        <street>2004, rte des Lucioles</street>
215        <city>Sophia-Antipolis</city>
216        <region>AM</region>
217        <code>06902</code>
218        <country>France</country>
219      </postal>
220      <email>ylafon@w3.org</email>
221      <uri>http://www.raubacapeu.net/people/yves/</uri>
222    </address>
223  </author>
224
225  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
226    <organization abbrev="greenbytes">greenbytes GmbH</organization>
227    <address>
228      <postal>
229        <street>Hafenweg 16</street>
230        <city>Muenster</city><region>NW</region><code>48155</code>
231        <country>Germany</country>
232      </postal>
233      <phone>+49 251 2807760</phone>
234      <facsimile>+49 251 2807761</facsimile>
235      <email>julian.reschke@greenbytes.de</email>
236      <uri>http://greenbytes.de/tech/webdav/</uri>
237    </address>
238  </author>
239
240  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
241  <workgroup>HTTPbis Working Group</workgroup>
242
243<abstract>
244<t>
245   The Hypertext Transfer Protocol (HTTP) is an application-level
246   protocol for distributed, collaborative, hypermedia information
247   systems. HTTP has been in use by the World Wide Web global information
248   initiative since 1990. This document is Part 2 of the seven-part specification
249   that defines the protocol referred to as "HTTP/1.1" and, taken together,
250   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
251   as expressed by request methods, request header fields, response status codes,
252   and response header fields.
253</t>
254</abstract>
255
256<note title="Editorial Note (To be removed by RFC Editor)">
257  <t>
258    Discussion of this draft should take place on the HTTPBIS working group
259    mailing list (ietf-http-wg@w3.org), which is archived at
260    <eref target="http://lists.w3.org/Archives/Public/ietf-http-wg/"/>.
261  </t>
262  <t>
263    The current issues list is at
264    <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/> and related
265    documents (including fancy diffs) can be found at
266    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
267  </t>
268  <t>
269    The changes in this draft are summarized in <xref target="changes.since.15"/>.
270  </t>
271</note>
272</front>
273<middle>
274<section title="Introduction" anchor="introduction">
275<t>
276   This document defines HTTP/1.1 request and response semantics.  Each HTTP
277   message, as defined in &messaging;, is in the form of either a request or
278   a response.  An HTTP server listens on a connection for HTTP requests and
279   responds to each request, in the order received on that connection, with
280   one or more HTTP response messages.  This document defines the commonly
281   agreed upon semantics of the HTTP uniform interface, the intentions defined
282   by each request method, and the various response messages that might be
283   expected as a result of applying that method to the target resource.
284</t>
285<t>
286   This document is currently disorganized in order to minimize the changes
287   between drafts and enable reviewers to see the smaller errata changes.
288   A future draft will reorganize the sections to better reflect the content.
289   In particular, the sections will be ordered according to the typical
290   processing of an HTTP request message (after message parsing): resource
291   mapping, methods, request modifying header fields, response status,
292   status modifying header fields, and resource metadata.  The current mess
293   reflects how widely dispersed these topics and associated requirements
294   had become in <xref target="RFC2616"/>.
295</t>
296
297<section title="Requirements" anchor="intro.requirements">
298<t>
299   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
300   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
301   document are to be interpreted as described in <xref target="RFC2119"/>.
302</t>
303<t>
304   An implementation is not compliant if it fails to satisfy one or more
305   of the "MUST" or "REQUIRED" level requirements for the protocols it
306   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
307   level and all the "SHOULD" level requirements for its protocols is said
308   to be "unconditionally compliant"; one that satisfies all the "MUST"
309   level requirements but not all the "SHOULD" level requirements for its
310   protocols is said to be "conditionally compliant".
311</t>
312</section>
313
314<section title="Syntax Notation" anchor="notation">
315  <x:anchor-alias value="CR"/>
316  <x:anchor-alias value="DIGIT"/>
317  <x:anchor-alias value="LF"/>
318  <x:anchor-alias value="VCHAR"/>
319  <x:anchor-alias value="WSP"/>
320<t>
321  This specification uses the ABNF syntax defined in &notation; (which
322  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
323  <xref target="collected.abnf"/> shows the collected ABNF, with the list
324  rule expanded.
325</t>
326<t>
327  The following core rules are included by
328  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
329  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
330  DIGIT (decimal 0-9), DQUOTE (double quote),
331  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
332  OCTET (any 8-bit sequence of data), SP (space),
333  VCHAR (any visible USASCII character),
334  and WSP (whitespace).
335</t>
336
337<section title="Core Rules" anchor="core.rules">
338  <x:anchor-alias value="obs-text"/>
339  <x:anchor-alias value="quoted-string"/>
340  <x:anchor-alias value="token"/>
341  <x:anchor-alias value="OWS"/>
342  <x:anchor-alias value="RWS"/>
343<t>
344  The core rules below are defined in &basic-rules;:
345</t>
346<figure><artwork type="abnf2616">
347  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
348  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
349  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
350  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
351  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
352</artwork></figure>
353</section>
354
355<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
356  <x:anchor-alias value="absolute-URI"/>
357  <x:anchor-alias value="comment"/>
358  <x:anchor-alias value="HTTP-date"/>
359  <x:anchor-alias value="partial-URI"/>
360  <x:anchor-alias value="product"/>
361  <x:anchor-alias value="URI-reference"/>
362<t>
363  The ABNF rules below are defined in other parts:
364</t>
365<figure><!--Part1--><artwork type="abnf2616">
366  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
367  <x:ref>comment</x:ref>       = &lt;comment, defined in &header-fields;&gt;
368  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
369  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
370  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
371  <x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in &uri;&gt;
372</artwork></figure>
373</section>
374</section>
375</section>
376
377<section title="Method" anchor="method">
378  <x:anchor-alias value="Method"/>
379  <x:anchor-alias value="extension-method"/>
380<t>
381   The Method token indicates the request method to be performed on the target
382   resource (&effective-request-uri;). The method is case-sensitive.
383</t>
384<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/>
385  <x:ref>Method</x:ref>         = <x:ref>token</x:ref>
386</artwork></figure>
387<t>
388   The list of methods allowed by a resource can be specified in an
389   Allow header field (<xref target="header.allow"/>). The status code of the response
390   always notifies the client whether a method is currently allowed on a
391   resource, since the set of allowed methods can change dynamically. An
392   origin server &SHOULD; respond with the status code 405 (Method Not Allowed)
393   if the method is known by the origin server but not allowed for the
394   resource, and 501 (Not Implemented) if the method is
395   unrecognized or not implemented by the origin server. The methods GET
396   and HEAD &MUST; be supported by all general-purpose servers. All other
397   methods are &OPTIONAL;; however, if the above methods are implemented,
398   they &MUST; be implemented with the same semantics as those specified
399   in <xref target="method.definitions"/>.
400</t>
401
402<section title="Overview of Methods" anchor="overview.of.methods">
403<t>
404  The methods listed below are defined in <xref target="method.definitions"/>.
405</t>
406<texttable align="left">
407  <ttcol>Method Name</ttcol><ttcol>Defined in...</ttcol>
408 
409  <c>OPTIONS</c> <c><xref target="OPTIONS"/></c>
410  <c>GET</c> <c><xref target="GET"/></c>
411  <c>HEAD</c> <c><xref target="HEAD"/></c>
412  <c>POST</c> <c><xref target="POST"/></c>
413  <c>PUT</c> <c><xref target="PUT"/></c>
414  <c>DELETE</c> <c><xref target="DELETE"/></c>
415  <c>TRACE</c> <c><xref target="TRACE"/></c>
416  <c>CONNECT</c> <c><xref target="CONNECT"/></c>
417</texttable>
418<t>
419  Note that this list is not exhaustive &mdash; it does not include request methods defined
420  in other specifications.
421</t>
422</section>
423
424<section title="Method Registry" anchor="method.registry">
425<t>
426  The HTTP Method Registry defines the name space for the Method token in the
427  Request line of an HTTP request.
428</t>
429<t>
430  Registrations &MUST; include the following fields:
431  <list style="symbols">
432    <t>Method Name (see <xref target="method"/>)</t>
433    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
434    <t>Pointer to specification text</t>
435  </list>
436</t>
437<t>
438  Values to be added to this name space are subject to IETF review
439  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
440</t>
441<t>
442  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
443</t>
444
445<section title="Considerations for New Methods" anchor="considerations.for.new.methods">
446<t>
447   When it is necessary to express new semantics for a HTTP request that
448   aren't specific to a single application or media type, and currently defined
449   methods are inadequate, it may be appropriate to register a new method.
450</t>
451<t>
452   HTTP methods are generic; that is, they are potentially applicable to any
453   resource, not just one particular media type, "type" of resource, or
454   application. As such, it is preferred that new HTTP methods be registered
455   in a document that isn't specific to a single application, so that this is
456   clear.
457</t>
458<t>
459   Due to the parsing rules defined in &message-body;, definitions of HTTP
460   methods cannot prohibit the presence of a message-body on either the request
461   or the response message (with responses to HEAD requests being the single
462   exception). Definitions of new methods cannot change this rule, but they can
463   specify that only zero-length bodies (as opposed to absent bodies) are allowed.
464</t>
465<t>
466   New method definitions need to indicate whether they are safe (<xref
467   target="safe.methods"/>), what semantics (if any) the request body has,
468   and whether they are idempotent (<xref target="idempotent.methods"/>).
469   They also need to state whether they can be cached (&caching;); in
470   particular what conditions a cache may store the response, and under what
471   conditions such a stored response may be used to satisfy a subsequent
472   request.
473</t>
474</section>
475
476</section>
477</section>
478
479<section title="Request Header Fields" anchor="request.header.fields">
480  <x:anchor-alias value="request-header"/>
481<t>
482   The request header fields allow the client to pass additional
483   information about the request, and about the client itself, to the
484   server. These fields act as request modifiers, with semantics
485   equivalent to the parameters on a programming language method
486   invocation.
487</t>
488<texttable align="left">
489  <ttcol>Header Field Name</ttcol>
490  <ttcol>Defined in...</ttcol>
491
492  <c>Accept</c> <c>&header-accept;</c>
493  <c>Accept-Charset</c> <c>&header-accept-charset;</c>
494  <c>Accept-Encoding</c> <c>&header-accept-encoding;</c>
495  <c>Accept-Language</c> <c>&header-accept-language;</c>
496  <c>Authorization</c> <c>&header-authorization;</c>
497  <c>Expect</c> <c><xref target="header.expect"/></c>
498  <c>From</c> <c><xref target="header.from"/></c>
499  <c>Host</c> <c>&header-host;</c>
500  <c>If-Match</c> <c>&header-if-match;</c>
501  <c>If-Modified-Since</c> <c>&header-if-modified-since;</c>
502  <c>If-None-Match</c> <c>&header-if-none-match;</c>
503  <c>If-Range</c> <c>&header-if-range;</c>
504  <c>If-Unmodified-Since</c> <c>&header-if-unmodified-since;</c>
505  <c>Max-Forwards</c> <c><xref target="header.max-forwards"/></c>
506  <c>Proxy-Authorization</c> <c>&header-proxy-authorization;</c>
507  <c>Range</c> <c>&header-range;</c>
508  <c>Referer</c> <c><xref target="header.referer"/></c>
509  <c>TE</c> <c>&header-te;</c>
510  <c>User-Agent</c> <c><xref target="header.user-agent"/></c>
511</texttable>
512</section>
513
514<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
515  <x:anchor-alias value="Reason-Phrase"/>
516  <x:anchor-alias value="Status-Code"/>
517  <x:anchor-alias value="extension-code"/>
518<t>
519   The Status-Code element is a 3-digit integer result code of the attempt to
520   understand and satisfy the request.
521</t>
522<t>
523   The Reason-Phrase is intended to give a short textual description of the
524   Status-Code and is intended for a human user. The client does not need
525   to examine or display the Reason-Phrase.
526</t>
527<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"/>
528  <x:ref>Status-Code</x:ref>    = 3<x:ref>DIGIT</x:ref>
529  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
530</artwork></figure>
531<t>
532   HTTP status codes are extensible. HTTP applications are not required
533   to understand the meaning of all registered status codes, though such
534   understanding is obviously desirable. However, applications &MUST;
535   understand the class of any status code, as indicated by the first
536   digit, and treat any unrecognized response as being equivalent to the
537   x00 status code of that class, with the exception that an
538   unrecognized response &MUST-NOT; be cached. For example, if an
539   unrecognized status code of 431 is received by the client, it can
540   safely assume that there was something wrong with its request and
541   treat the response as if it had received a 400 status code. In such
542   cases, user agents &SHOULD; present to the user the representation enclosed
543   with the response, since that representation is likely to include human-readable
544   information which will explain the unusual status.
545</t>
546
547<section title="Overview of Status Codes" anchor="overview.of.status.codes">
548<t> 
549   The status codes listed below are defined in <xref target="status.codes"/>
550   of this specification, &p4-status-codes;, &p5-status-codes;, and &p7-status-codes;.
551   The reason phrases listed here are only recommendations &mdash; they can be
552   replaced by local equivalents without affecting the protocol.
553</t>
554<texttable align="left">
555  <ttcol>Status-Code</ttcol>
556  <ttcol>Reason-Phrase</ttcol>
557  <ttcol>Defined in...</ttcol>
558 
559  <c>100</c> <c>Continue</c> <c><xref target="status.100"/></c>
560  <c>101</c> <c>Switching Protocols</c> <c><xref target="status.101"/></c>
561
562  <c>200</c> <c>OK</c> <c><xref target="status.200"/></c>
563  <c>201</c> <c>Created</c> <c><xref target="status.201"/></c>
564  <c>202</c> <c>Accepted</c> <c><xref target="status.202"/></c>
565  <c>203</c> <c>Non-Authoritative Information</c> <c><xref target="status.203"/></c>
566  <c>204</c> <c>No Content</c> <c><xref target="status.204"/></c>
567  <c>205</c> <c>Reset Content</c> <c><xref target="status.205"/></c>
568  <c>206</c> <c>Partial Content</c> <c>&status-206;</c>
569
570  <c>300</c> <c>Multiple Choices</c> <c><xref target="status.300"/></c>
571  <c>301</c> <c>Moved Permanently</c> <c><xref target="status.301"/></c>
572  <c>302</c> <c>Found</c> <c><xref target="status.302"/></c>
573  <c>303</c> <c>See Other</c> <c><xref target="status.303"/></c>
574  <c>304</c> <c>Not Modified</c> <c>&status-304;</c>
575  <c>305</c> <c>Use Proxy</c> <c><xref target="status.305"/></c>
576  <c>307</c> <c>Temporary Redirect</c> <c><xref target="status.307"/></c>
577
578  <c>400</c> <c>Bad Request</c> <c><xref target="status.400"/></c>
579  <c>401</c> <c>Unauthorized</c> <c>&status-401;</c>
580  <c>402</c> <c>Payment Required</c> <c><xref target="status.402"/></c>
581  <c>403</c> <c>Forbidden</c> <c><xref target="status.403"/></c>
582  <c>404</c> <c>Not Found</c> <c><xref target="status.404"/></c>
583  <c>405</c> <c>Method Not Allowed</c> <c><xref target="status.405"/></c>
584  <c>406</c> <c>Not Acceptable</c> <c><xref target="status.406"/></c>
585  <c>407</c> <c>Proxy Authentication Required</c> <c>&status-407;</c>
586  <c>408</c> <c>Request Time-out</c> <c><xref target="status.408"/></c>
587  <c>409</c> <c>Conflict</c> <c><xref target="status.409"/></c>
588  <c>410</c> <c>Gone</c> <c><xref target="status.410"/></c>
589  <c>411</c> <c>Length Required</c> <c><xref target="status.411"/></c>
590  <c>412</c> <c>Precondition Failed</c> <c>&status-412;</c>
591  <c>413</c> <c>Request Representation Too Large</c> <c><xref target="status.413"/></c>
592  <c>414</c> <c>URI Too Long</c> <c><xref target="status.414"/></c>
593  <c>415</c> <c>Unsupported Media Type</c> <c><xref target="status.415"/></c>
594  <c>416</c> <c>Requested range not satisfiable</c> <c>&status-416;</c>
595  <c>417</c> <c>Expectation Failed</c> <c><xref target="status.417"/></c>
596  <c>426</c> <c>Upgrade Required</c> <c><xref target="status.426"/></c>
597
598  <c>500</c> <c>Internal Server Error</c> <c><xref target="status.500"/></c>
599  <c>501</c> <c>Not Implemented</c> <c><xref target="status.501"/></c>
600  <c>502</c> <c>Bad Gateway</c> <c><xref target="status.502"/></c>
601  <c>503</c> <c>Service Unavailable</c> <c><xref target="status.503"/></c>
602  <c>504</c> <c>Gateway Time-out</c> <c><xref target="status.504"/></c>
603  <c>505</c> <c>HTTP Version not supported</c> <c><xref target="status.505"/></c>
604</texttable>
605<t>
606   Note that this list is not exhaustive &mdash; it does not include
607   extension status codes defined in other specifications.
608</t>
609</section>
610
611<section title="Status Code Registry" anchor="status.code.registry">
612<t>
613  The HTTP Status Code Registry defines the name space for the Status-Code
614  token in the Status-Line of an HTTP response.
615</t>
616<t>
617  Values to be added to this name space are subject to IETF review
618  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
619</t>
620<t>
621  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
622</t>
623
624<section title="Considerations for New Status Codes" anchor="considerations.for.new.status.codes">
625<t>
626   When it is necessary to express new semantics for a HTTP response that
627   aren't specific to a single application or media type, and currently defined
628   status codes are inadequate, a new status code can be registered.
629</t>
630<t>
631   HTTP status codes are generic; that is, they are potentially applicable to
632   any resource, not just one particular media type, "type" of resource, or
633   application. As such, it is preferred that new HTTP status codes be
634   registered in a document that isn't specific to a single application, so
635   that this is clear.
636</t>
637<t>
638   Definitions of new HTTP status codes typically explain the request
639   conditions that produce a response containing the status code (e.g.,
640   combinations of request headers and/or method(s)), along with any
641   interactions with response headers (e.g., those that are required, those
642   that modify the semantics of the response).
643</t>
644<t>
645   New HTTP status codes are required to fall under one of the categories
646   defined in <xref target="status.codes"/>. To allow existing parsers to
647   properly handle them, new status codes cannot disallow a response body,
648   although they can mandate a zero-length response body. They can require the
649   presence of one or more particular HTTP response header(s).
650</t>
651<t>
652   Likewise, their definitions can specify that caches are allowed to use
653   heuristics to determine their freshness (see &caching;; by default, it is
654   not allowed), and can define how to determine the resource which they
655   carry a representation for (see <xref
656   target="identifying.response.associated.with.representation"/>; by default,
657   it is anonymous).
658</t>
659</section>
660
661</section>
662
663</section>
664
665<section title="Response Header Fields" anchor="response.header.fields">
666  <x:anchor-alias value="response-header"/>
667<t>
668   The response header fields allow the server to pass additional
669   information about the response which cannot be placed in the Status-Line.
670   These header fields give information about the server and about
671   further access to the target resource (&effective-request-uri;).
672</t>
673<texttable align="left">
674  <ttcol>Header Field Name</ttcol><ttcol>Defined in...</ttcol>
675
676  <c>Accept-Ranges</c> <c>&header-accept-ranges;</c>
677  <c>Age</c> <c>&header-age;</c>
678  <c>Allow</c> <c><xref target="header.allow"/></c>
679  <c>ETag</c> <c>&header-etag;</c>
680  <c>Location</c> <c><xref target="header.location"/></c>
681  <c>Proxy-Authenticate</c> <c>&header-proxy-authenticate;</c>
682  <c>Retry-After</c> <c><xref target="header.retry-after"/></c>
683  <c>Server</c> <c><xref target="header.server"/></c>
684  <c>Vary</c> <c>&header-vary;</c>
685  <c>WWW-Authenticate</c> <c>&header-www-authenticate;</c>
686</texttable>
687</section>
688
689<section title="Representation" anchor="representation">
690<t>
691   Request and Response messages &MAY; transfer a representation if not otherwise
692   restricted by the request method or response status code. A representation
693   consists of metadata (representation header fields) and data (representation
694   body).  When a complete or partial representation is enclosed in an HTTP message,
695   it is referred to as the payload of the message. HTTP representations
696   are defined in &payload;.
697</t>
698<t>
699   A representation body is only present in a message when a message-body is
700   present, as described in &message-body;. The representation body is obtained
701   from the message-body by decoding any Transfer-Encoding that might
702   have been applied to ensure safe and proper transfer of the message.
703</t>
704
705<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
706<t>
707   It is sometimes necessary to determine an identifier for the resource
708   associated with a representation.
709</t>
710<t>
711   An HTTP request representation, when present, is always associated with an
712   anonymous (i.e., unidentified) resource.
713</t>
714<t>
715   In the common case, an HTTP response is a representation of the target
716   resource (see &effective-request-uri;). However, this is not always the
717   case. To determine the URI of the resource a response is associated with,
718   the following rules are used (with the first applicable one being selected):
719</t>
720<t><list style="numbers">
721   <t>If the response status code is 200 or 203 and the request method was GET,
722   the response payload is a representation of the target resource.</t>
723   <t>If the response status code is 204, 206, or 304 and the request method was GET
724   or HEAD, the response payload is a partial representation of the target
725   resource (see &combining-responses;).</t>
726   <t>If the response has a Content-Location header field, and that URI is the same
727   as the effective request URI, the response payload is a representation of the
728   target resource.</t>
729   <t>If the response has a Content-Location header field, and that URI is not the
730   same as the effective request URI, then the response asserts that its
731   payload is a representation of the resource identified by the
732   Content-Location URI. However, such an assertion cannot be trusted unless
733   it can be verified by other means (not defined by HTTP).</t>
734   <t>Otherwise, the response is a representation of an anonymous (i.e.,
735   unidentified) resource.</t>
736</list></t>
737<t>
738  <cref anchor="TODO-req-uri">
739   The comparison function is going to have to be defined somewhere,
740   because we already need to compare URIs for things like cache invalidation.</cref>
741</t>
742</section>
743
744</section>
745
746
747<section title="Method Definitions" anchor="method.definitions">
748<t>
749   The set of common request methods for HTTP/1.1 is defined below. Although
750   this set can be expanded, additional methods cannot be assumed to
751   share the same semantics for separately extended clients and servers.
752</t>
753
754<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
755
756<section title="Safe Methods" anchor="safe.methods">
757<iref item="Safe Methods" primary="true"/>
758<t>
759   Implementors need to be aware that the software represents the user in
760   their interactions over the Internet, and need to allow
761   the user to be aware of any actions they take which might have an
762   unexpected significance to themselves or others.
763</t>
764<t>
765   In particular, the convention has been established that the GET, HEAD,
766   OPTIONS, and TRACE request methods &SHOULD-NOT; have the significance
767   of taking an action other than retrieval. These request methods ought
768   to be considered "<x:dfn anchor="safe">safe</x:dfn>".
769   This allows user agents to represent other methods, such as POST, PUT
770   and DELETE, in a special way, so that the user is made aware of the
771   fact that a possibly unsafe action is being requested.
772</t>
773<t>
774   Naturally, it is not possible to ensure that the server does not
775   generate side-effects as a result of performing a GET request; in
776   fact, some dynamic resources consider that a feature. The important
777   distinction here is that the user did not request the side-effects,
778   so therefore cannot be held accountable for them.
779</t>
780</section>
781
782<section title="Idempotent Methods" anchor="idempotent.methods">
783<iref item="Idempotent Methods" primary="true"/>
784<t>
785   Request methods can also have the property of "idempotence" in that,
786   aside from error or expiration issues, the intended effect of multiple
787   identical requests is the same as for a single request.
788   PUT, DELETE, and all safe request methods are idempotent.
789   It is important to note that idempotence refers only to changes
790   requested by the client: a server is free to change its state due
791   to multiple requests for the purpose of tracking those requests,
792   versioning of results, etc.
793</t>
794</section>
795</section>
796
797<section title="OPTIONS" anchor="OPTIONS">
798  <rdf:Description>
799    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
800  </rdf:Description>
801  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
802  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
803<t>
804   The OPTIONS method requests information about the
805   communication options available on the request/response chain
806   identified by the effective request URI. This method allows a client to
807   determine the options and/or requirements associated with a resource,
808   or the capabilities of a server, without implying a resource action
809   or initiating a resource retrieval.
810</t>
811<t>
812   Responses to the OPTIONS method are not cacheable.
813</t>
814<t>
815   If the OPTIONS request includes a message-body (as indicated by the
816   presence of Content-Length or Transfer-Encoding), then the media type
817   &MUST; be indicated by a Content-Type field. Although this
818   specification does not define any use for such a body, future
819   extensions to HTTP might use the OPTIONS body to make more detailed
820   queries on the server.
821</t>
822<t>
823   If the request-target is an asterisk ("*"), the OPTIONS request is
824   intended to apply to the server in general rather than to a specific
825   resource. Since a server's communication options typically depend on
826   the resource, the "*" request is only useful as a "ping" or "no-op"
827   type of method; it does nothing beyond allowing the client to test
828   the capabilities of the server. For example, this can be used to test
829   a proxy for HTTP/1.1 compliance (or lack thereof).
830</t>
831<t>
832   If the request-target is not an asterisk, the OPTIONS request applies
833   only to the options that are available when communicating with that
834   resource.
835</t>
836<t>
837   A 200 response &SHOULD; include any header fields that indicate
838   optional features implemented by the server and applicable to that
839   resource (e.g., Allow), possibly including extensions not defined by
840   this specification. The response body, if any, &SHOULD; also include
841   information about the communication options. The format for such a
842   body is not defined by this specification, but might be defined by
843   future extensions to HTTP. Content negotiation &MAY; be used to select
844   the appropriate response format. If no response body is included, the
845   response &MUST; include a Content-Length field with a field-value of
846   "0".
847</t>
848<t>
849   The Max-Forwards header field &MAY; be used to target a
850   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
851   If no Max-Forwards field is present in the request, then the forwarded
852   request &MUST-NOT; include a Max-Forwards field.
853</t>
854</section>
855
856<section title="GET" anchor="GET">
857  <rdf:Description>
858    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
859  </rdf:Description>
860  <iref primary="true" item="GET method" x:for-anchor=""/>
861  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
862<t>
863   The GET method requests transfer of a current representation of
864   the target resource.
865</t>
866<t>   
867   If the target resource is a data-producing process, it is the
868   produced data which shall be returned as the representation in the response and not
869   the source text of the process, unless that text happens to be the output of
870   the process.
871</t>
872<t>
873   The semantics of the GET method change to a "conditional GET" if the
874   request message includes an If-Modified-Since, If-Unmodified-Since,
875   If-Match, If-None-Match, or If-Range header field. A conditional GET
876   requests that the representation be transferred only under the
877   circumstances described by the conditional header field(s). The
878   conditional GET request is intended to reduce unnecessary network
879   usage by allowing cached representations to be refreshed without requiring
880   multiple requests or transferring data already held by the client.
881</t>
882<t>
883   The semantics of the GET method change to a "partial GET" if the
884   request message includes a Range header field. A partial GET requests
885   that only part of the representation be transferred, as described in &header-range;.
886   The partial GET request is intended to reduce unnecessary
887   network usage by allowing partially-retrieved representations to be
888   completed without transferring data already held by the client.
889</t>
890<t>
891   Bodies on GET requests have no defined semantics. Note that sending a body
892   on a GET request might cause some existing implementations to reject the
893   request.
894</t>
895<t>
896   The response to a GET request is cacheable and &MAY; be used to satisfy
897   subsequent GET and HEAD requests (see &caching;).
898</t>
899<t>
900   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
901</t>
902</section>
903
904<section title="HEAD" anchor="HEAD">
905  <rdf:Description>
906    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
907  </rdf:Description>
908  <iref primary="true" item="HEAD method" x:for-anchor=""/>
909  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
910<t>
911   The HEAD method is identical to GET except that the server &MUST-NOT;
912   return a message-body in the response. The metadata contained
913   in the HTTP header fields in response to a HEAD request &SHOULD; be identical
914   to the information sent in response to a GET request. This method can
915   be used for obtaining metadata about the representation implied by the
916   request without transferring the representation body. This method is
917   often used for testing hypertext links for validity, accessibility,
918   and recent modification.
919</t>
920<t>
921   The response to a HEAD request is cacheable and &MAY; be used to satisfy
922   a subsequent HEAD request; see &caching;. It also &MAY; be used to update a previously cached
923   representation from that resource; if the new field values
924   indicate that the cached representation differs from the current representation (as
925   would be indicated by a change in Content-Length, ETag
926   or Last-Modified), then the cache &MUST; treat the cache entry as
927   stale.
928</t>
929<t>
930   Bodies on HEAD requests have no defined semantics. Note that sending a body
931   on a HEAD request might cause some existing implementations to reject the
932   request.
933</t>
934</section>
935
936<section title="POST" anchor="POST">
937  <iref primary="true" item="POST method" x:for-anchor=""/>
938  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
939<t>
940   The POST method requests that the origin server accept the
941   representation enclosed in the request as data to be processed by the
942   target resource. POST is designed to allow a uniform method to cover the
943   following functions:
944  <list style="symbols">
945    <t>
946      Annotation of existing resources;
947    </t>
948    <t>
949        Posting a message to a bulletin board, newsgroup, mailing list,
950        or similar group of articles;
951    </t>
952    <t>
953        Providing a block of data, such as the result of submitting a
954        form, to a data-handling process;
955    </t>
956    <t>
957        Extending a database through an append operation.
958    </t>
959  </list>
960</t>
961<t>
962   The actual function performed by the POST method is determined by the
963   server and is usually dependent on the effective request URI.
964</t>
965<t>
966   The action performed by the POST method might not result in a
967   resource that can be identified by a URI. In this case, either 200
968   (OK) or 204 (No Content) is the appropriate response status code,
969   depending on whether or not the response includes a representation that
970   describes the result.
971</t>
972<t>
973   If a resource has been created on the origin server, the response
974   &SHOULD; be 201 (Created) and contain a representation which describes the
975   status of the request and refers to the new resource, and a Location
976   header field (see <xref target="header.location"/>).
977</t>
978<t>
979   Responses to POST requests are only cacheable when they
980   include explicit freshness information (see &p6-explicit;). A
981   cached POST response with a Content-Location header field
982   (see &header-content-location;) whose value is the effective
983   Request URI &MAY; be used to satisfy subsequent GET and HEAD requests.
984</t>
985<t>
986   Note that POST caching is not widely implemented.
987   However, the 303 (See Other) response can be used to direct the
988   user agent to retrieve a cacheable resource.
989</t>
990</section>
991
992<section title="PUT" anchor="PUT">
993  <iref primary="true" item="PUT method" x:for-anchor=""/>
994  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
995<t>
996   The PUT method requests that the state of the target resource
997   be created or replaced with the state defined by the representation
998   enclosed in the request message payload.  A successful PUT of a given
999   representation would suggest that a subsequent GET on that same target
1000   resource will result in an equivalent representation being returned in
1001   a 200 (OK) response.  However, there is no guarantee that such a state
1002   change will be observable, since the target resource might be acted
1003   upon by other user agents in parallel, or might be subject to dynamic
1004   processing by the origin server, before any subsequent GET is received.
1005   A successful response only implies that the user agent's intent was
1006   achieved at the time of its processing by the origin server.
1007</t>
1008<t>   
1009   If the target resource does not have a current representation and
1010   the PUT successfully creates one, then the origin server &MUST; inform
1011   the user agent by sending a 201 (Created) response.  If the target
1012   resource does have a current representation and that representation is
1013   successfully modified in accordance with the state of the enclosed
1014   representation, then either a 200 (OK) or 204 (No Content) response
1015   &SHOULD; be sent to indicate successful completion of the request.
1016</t>
1017<t>
1018   Unrecognized header fields &SHOULD; be ignored (i.e., not saved
1019   as part of the resource state).
1020</t>
1021<t>
1022   An origin server &SHOULD; verify that the PUT representation is
1023   consistent with any constraints which the server has for the target
1024   resource that cannot or will not be changed by the PUT.  This is
1025   particularly important when the origin server uses internal
1026   configuration information related to the URI in order to set the
1027   values for representation metadata on GET responses.  When a PUT
1028   representation is inconsistent with the target resource, the origin
1029   server &SHOULD; either make them consistent, by transforming the
1030   representation or changing the resource configuration, or respond
1031   with an appropriate error message containing sufficient information
1032   to explain why the representation is unsuitable.  The 409 (Conflict)
1033   or 415 (Unsupported Media Type) status codes are suggested, with the
1034   latter being specific to constraints on Content-Type values.
1035</t>
1036<t>
1037   For example, if the target resource is configured to always have a
1038   Content-Type of "text/html" and the representation being PUT has a
1039   Content-Type of "image/jpeg", then the origin server &SHOULD; do one of:
1040   (a) reconfigure the target resource to reflect the new media type;
1041   (b) transform the PUT representation to a format consistent with that
1042   of the resource before saving it as the new resource state; or,
1043   (c) reject the request with a 415 response indicating that the target
1044   resource is limited to "text/html", perhaps including a link to a
1045   different resource that would be a suitable target for the new
1046   representation.
1047</t>
1048<t>
1049   HTTP does not define exactly how a PUT method affects the state
1050   of an origin server beyond what can be expressed by the intent of
1051   the user agent request and the semantics of the origin server response.
1052   It does not define what a resource might be, in any sense of that
1053   word, beyond the interface provided via HTTP.  It does not define
1054   how resource state is "stored", nor how such storage might change
1055   as a result of a change in resource state, nor how the origin server
1056   translates resource state into representations.  Generally speaking,
1057   all implementation details behind the resource interface are
1058   intentionally hidden by the server.
1059</t>
1060<t>
1061   The fundamental difference between the POST and PUT methods is
1062   highlighted by the different intent for the target resource.
1063   The target resource in a POST request is intended to handle the
1064   enclosed representation as a data-accepting process, such as for
1065   a gateway to some other protocol or a document that accepts annotations.
1066   In contrast, the target resource in a PUT request is intended to
1067   take the enclosed representation as a new or replacement value.
1068   Hence, the intent of PUT is idempotent and visible to intermediaries,
1069   even though the exact effect is only known by the origin server.
1070</t>
1071<t>
1072   Proper interpretation of a PUT request presumes that the user agent
1073   knows what target resource is desired.  A service that is intended
1074   to select a proper URI on behalf of the client, after receiving
1075   a state-changing request, &SHOULD; be implemented using the POST
1076   method rather than PUT.  If the origin server will not make the
1077   requested PUT state change to the target resource and instead
1078   wishes to have it applied to a different resource, such as when the
1079   resource has been moved to a different URI, then the origin server
1080   &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
1081   then make its own decision regarding whether or not to redirect the
1082   request.
1083</t>
1084<t>
1085   A PUT request applied to the target resource &MAY; have side-effects
1086   on other resources.  For example, an article might have a URI for
1087   identifying "the current version" (a resource) which is separate
1088   from the URIs identifying each particular version (different
1089   resources that at one point shared the same state as the current version
1090   resource).  A successful PUT request on "the current version" URI might
1091   therefore create a new version resource in addition to changing the
1092   state of the target resource, and might also cause links to be added
1093   between the related resources.
1094</t>
1095<t>
1096   An origin server &SHOULD; reject any PUT request that contains a
1097   Content-Range header field, since it might be misinterpreted as
1098   partial content (or might be partial content that is being mistakenly
1099   PUT as a full representation).  Partial content updates are
1100   possible by targeting a separately identified resource with state
1101   that overlaps a portion of the larger resource, or by using a
1102   different method that has been specifically defined for partial
1103   updates (for example, the PATCH method defined in
1104   <xref target="RFC5789"/>).
1105</t>
1106<t>
1107   Responses to the PUT method are not cacheable. If a PUT request passes
1108   through a cache that has one or more stored responses for the effective
1109   request URI, those stored responses will be invalidated (see
1110   &p6-invalid;).
1111</t>
1112</section>
1113
1114<section title="DELETE" anchor="DELETE">
1115  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1116  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1117<t>
1118   The DELETE method requests that the origin server delete the target
1119   resource. This method &MAY; be overridden by
1120   human intervention (or other means) on the origin server. The client cannot
1121   be guaranteed that the operation has been carried out, even if the
1122   status code returned from the origin server indicates that the action
1123   has been completed successfully. However, the server &SHOULD-NOT; 
1124   indicate success unless, at the time the response is given, it
1125   intends to delete the resource or move it to an inaccessible
1126   location.
1127</t>
1128<t>
1129   A successful response &SHOULD; be 200 (OK) if the response includes an
1130   representation describing the status, 202 (Accepted) if the action has not
1131   yet been enacted, or 204 (No Content) if the action has been enacted
1132   but the response does not include a representation.
1133</t>
1134<t>
1135   Bodies on DELETE requests have no defined semantics. Note that sending a body
1136   on a DELETE request might cause some existing implementations to reject the
1137   request.
1138</t>
1139<t>
1140   Responses to the DELETE method are not cacheable. If a DELETE request
1141   passes through a cache that has one or more stored responses for the
1142   effective request URI, those stored responses will be invalidated (see
1143   &p6-invalid;).
1144</t>
1145</section>
1146
1147<section title="TRACE" anchor="TRACE">
1148  <rdf:Description>
1149    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1150  </rdf:Description>
1151  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1152  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1153<t>
1154   The TRACE method requests a remote, application-layer loop-back
1155   of the request message. The final recipient of the request
1156   &SHOULD; reflect the message received back to the client as the
1157   message-body of a 200 (OK) response. The final recipient is either the
1158   origin server or the first proxy to receive a Max-Forwards
1159   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1160   A TRACE request &MUST-NOT; include a message-body.
1161</t>
1162<t>
1163   TRACE allows the client to see what is being received at the other
1164   end of the request chain and use that data for testing or diagnostic
1165   information. The value of the Via header field (&header-via;) is of
1166   particular interest, since it acts as a trace of the request chain.
1167   Use of the Max-Forwards header field allows the client to limit the
1168   length of the request chain, which is useful for testing a chain of
1169   proxies forwarding messages in an infinite loop.
1170</t>
1171<t>
1172   If the request is valid, the response &SHOULD; have a Content-Type of
1173   "message/http" (see &media-type-message-http;) and contain a message-body
1174   that encloses a copy of the entire request message.
1175   Responses to the TRACE method are not cacheable.
1176</t>
1177</section>
1178
1179<section title="CONNECT" anchor="CONNECT">
1180  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1181  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1182<t>
1183   The CONNECT method requests that the proxy establish a tunnel
1184   to the request-target and then restrict its behavior to blind
1185   forwarding of packets until the connection is closed.
1186</t>
1187<t>
1188   When using CONNECT, the request-target &MUST; use the authority form
1189   (&request-target;); i.e., the request-target consists of only the
1190   host name and port number of the tunnel destination, separated by a colon.
1191   For example,
1192</t>
1193<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1194CONNECT server.example.com:80 HTTP/1.1
1195Host: server.example.com:80
1196
1197</artwork></figure>
1198<t>
1199   Other HTTP mechanisms can be used normally with the CONNECT method &mdash;
1200   except end-to-end protocol Upgrade requests, since the
1201   tunnel must be established first.
1202</t>
1203<t>
1204   For example, proxy authentication might be used to establish the
1205   authority to create a tunnel:
1206</t>
1207<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1208CONNECT server.example.com:80 HTTP/1.1
1209Host: server.example.com:80
1210Proxy-Authorization: basic aGVsbG86d29ybGQ=
1211
1212</artwork></figure>
1213<t>
1214   Bodies on CONNECT requests have no defined semantics. Note that sending a body
1215   on a CONNECT request might cause some existing implementations to reject the
1216   request.
1217</t>
1218<t>
1219   Like any other pipelined HTTP/1.1 request, data to be tunnel may be
1220   sent immediately after the blank line. The usual caveats also apply:
1221   data may be discarded if the eventual response is negative, and the
1222   connection may be reset with no response if more than one TCP segment
1223   is outstanding.
1224</t>
1225
1226<section title="Establishing a Tunnel with CONNECT">
1227<t>
1228   Any successful (2xx) response to a CONNECT request indicates that the
1229   proxy has established a connection to the requested host and port,
1230   and has switched to tunneling the current connection to that server
1231   connection.
1232</t>
1233<t>
1234   It may be the case that the proxy itself can only reach the requested
1235   origin server through another proxy.  In this case, the first proxy
1236   &SHOULD; make a CONNECT request of that next proxy, requesting a tunnel
1237   to the authority.  A proxy &MUST-NOT; respond with any 2xx status code
1238   unless it has either a direct or tunnel connection established to the
1239   authority.
1240</t>
1241<t>
1242   An origin server which receives a CONNECT request for itself &MAY;
1243   respond with a 2xx status code to indicate that a connection is
1244   established.
1245</t>
1246<t>
1247   If at any point either one of the peers gets disconnected, any
1248   outstanding data that came from that peer will be passed to the other
1249   one, and after that also the other connection will be terminated by
1250   the proxy. If there is outstanding data to that peer undelivered,
1251   that data will be discarded.
1252</t>
1253
1254</section>
1255</section>
1256</section>
1257
1258
1259<section title="Status Code Definitions" anchor="status.codes">
1260<t>
1261   Each Status-Code is described below, including any metadata required
1262   in the response.
1263</t>
1264
1265<section title="Informational 1xx" anchor="status.1xx">
1266<t>
1267   This class of status code indicates a provisional response,
1268   consisting only of the Status-Line and optional header fields, and is
1269   terminated by an empty line. There are no required header fields for this
1270   class of status code. Since HTTP/1.0 did not define any 1xx status
1271   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1272   except under experimental conditions.
1273</t>
1274<t>
1275   A client &MUST; be prepared to accept one or more 1xx status responses
1276   prior to a regular response, even if the client does not expect a 100
1277   (Continue) status message. Unexpected 1xx status responses &MAY; be
1278   ignored by a user agent.
1279</t>
1280<t>
1281   Proxies &MUST; forward 1xx responses, unless the connection between the
1282   proxy and its client has been closed, or unless the proxy itself
1283   requested the generation of the 1xx response. (For example, if a
1284   proxy adds a "Expect: 100-continue" field when it forwards a request,
1285   then it need not forward the corresponding 100 (Continue)
1286   response(s).)
1287</t>
1288
1289<section title="100 Continue" anchor="status.100">
1290  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1291  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1292<t>
1293   The client &SHOULD; continue with its request. This interim response is
1294   used to inform the client that the initial part of the request has
1295   been received and has not yet been rejected by the server. The client
1296   &SHOULD; continue by sending the remainder of the request or, if the
1297   request has already been completed, ignore this response. The server
1298   &MUST; send a final response after the request has been completed. See
1299   &use100; for detailed discussion of the use and handling of this
1300   status code.
1301</t>
1302</section>
1303
1304<section title="101 Switching Protocols" anchor="status.101">
1305  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1306  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1307<t>
1308   The server understands and is willing to comply with the client's
1309   request, via the Upgrade message header field (&header-upgrade;), for a
1310   change in the application protocol being used on this connection. The
1311   server will switch protocols to those defined by the response's
1312   Upgrade header field immediately after the empty line which
1313   terminates the 101 response.
1314</t>
1315<t>
1316   The protocol &SHOULD; be switched only when it is advantageous to do
1317   so. For example, switching to a newer version of HTTP is advantageous
1318   over older versions, and switching to a real-time, synchronous
1319   protocol might be advantageous when delivering resources that use
1320   such features.
1321</t>
1322</section>
1323</section>
1324
1325<section title="Successful 2xx" anchor="status.2xx">
1326<t>
1327   This class of status code indicates that the client's request was
1328   successfully received, understood, and accepted.
1329</t>
1330
1331<section title="200 OK" anchor="status.200">
1332  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1333  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1334<t>
1335   The request has succeeded. The payload returned with the response
1336   is dependent on the method used in the request, for example:
1337  <list style="hanging">
1338    <t hangText="GET">
1339      a representation of the target resource is sent in the response;
1340    </t>
1341    <t hangText="HEAD">
1342      the same representation as GET, except without the message-body;
1343    </t>
1344    <t hangText="POST">
1345      a representation describing or containing the result of the action;
1346    </t>
1347    <t hangText="TRACE">
1348      a representation containing the request message as received by the
1349      end server.
1350    </t>
1351  </list>
1352</t>
1353<t>
1354   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1355   freshness for 200 responses.
1356</t>
1357</section>
1358
1359<section title="201 Created" anchor="status.201">
1360  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1361  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1362<t>
1363   The request has been fulfilled and has resulted in a new resource being
1364   created. The newly created resource can be referenced by the URI(s)
1365   returned in the payload of the response, with the most specific URI
1366   for the resource given by a Location header field. The response
1367   &SHOULD; include a payload containing a list of resource
1368   characteristics and location(s) from which the user or user agent can
1369   choose the one most appropriate. The payload format is specified by
1370   the media type given in the Content-Type header field. The origin
1371   server &MUST; create the resource before returning the 201 status code.
1372   If the action cannot be carried out immediately, the server &SHOULD;
1373   respond with 202 (Accepted) response instead.
1374</t>
1375<t>
1376   A 201 response &MAY; contain an ETag response header field indicating
1377   the current value of the entity-tag for the representation of the resource
1378   just created (see &header-etag;).
1379</t>
1380</section>
1381
1382<section title="202 Accepted" anchor="status.202">
1383  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1384  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1385<t>
1386   The request has been accepted for processing, but the processing has
1387   not been completed.  The request might or might not eventually be
1388   acted upon, as it might be disallowed when processing actually takes
1389   place. There is no facility for re-sending a status code from an
1390   asynchronous operation such as this.
1391</t>
1392<t>
1393   The 202 response is intentionally non-committal. Its purpose is to
1394   allow a server to accept a request for some other process (perhaps a
1395   batch-oriented process that is only run once per day) without
1396   requiring that the user agent's connection to the server persist
1397   until the process is completed. The representation returned with this
1398   response &SHOULD; include an indication of the request's current status
1399   and either a pointer to a status monitor or some estimate of when the
1400   user can expect the request to be fulfilled.
1401</t>
1402</section>
1403
1404<section title="203 Non-Authoritative Information" anchor="status.203">
1405  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1406  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1407<t>
1408   The representation in the response has been transformed or otherwise
1409   modified by a transforming proxy (&intermediaries;).  Note that the
1410   behaviour of transforming intermediaries is controlled by the no-transform
1411   Cache-Control directive (&header-cache-control;).
1412</t>
1413<t>
1414   This status code is only appropriate when the response status code would
1415   have been 200 (OK) otherwise. When the status code before transformation
1416   would have been different, the 214 Transformation Applied warn-code
1417   (&header-warning;) is appropriate.
1418</t>
1419<t>
1420   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1421   freshness for 203 responses.
1422</t>
1423</section>
1424
1425<section title="204 No Content" anchor="status.204">
1426  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1427  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1428<t>
1429   The 204 (No Content) status code indicates that the server has
1430   successfully fulfilled the request and that there is no additional
1431   content to return in the response payload body.  Metadata in the
1432   response header fields refer to the target resource and its current
1433   representation after the requested action.
1434</t>
1435<t>
1436   For example, if a 204 status code is received in response to a PUT
1437   request and the response contains an ETag header field, then the PUT
1438   was successful and the ETag field-value contains the entity-tag for
1439   the new representation of that target resource.
1440</t>
1441<t>
1442   The 204 response allows a server to indicate that the action has been
1443   successfully applied to the target resource while implying that the
1444   user agent &SHOULD-NOT; traverse away from its current "document view"
1445   (if any).  The server assumes that the user agent will provide some
1446   indication of the success to its user, in accord with its own interface,
1447   and apply any new or updated metadata in the response to the active
1448   representation.
1449</t>
1450<t>
1451   For example, a 204 status code is commonly used with document editing
1452   interfaces corresponding to a "save" action, such that the document
1453   being saved remains available to the user for editing. It is also
1454   frequently used with interfaces that expect automated data transfers
1455   to be prevalent, such as within distributed version control systems.
1456</t>
1457<t>
1458   The 204 response &MUST-NOT; include a message-body, and thus is always
1459   terminated by the first empty line after the header fields.
1460</t>
1461</section>
1462
1463<section title="205 Reset Content" anchor="status.205">
1464  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1465  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1466<t>
1467   The server has fulfilled the request and the user agent &SHOULD; reset
1468   the document view which caused the request to be sent. This response
1469   is primarily intended to allow input for actions to take place via
1470   user input, followed by a clearing of the form in which the input is
1471   given so that the user can easily initiate another input action.
1472</t>
1473<t>   
1474   The message-body included with the response &MUST; be empty. Note that
1475   receivers still need to parse the response according to the algorithm defined
1476   in &message-body;.
1477</t>
1478</section>
1479
1480<section title="206 Partial Content" anchor="status.206">
1481  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1482  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1483  <rdf:Description>
1484    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1485  </rdf:Description>
1486<t>
1487   The server has fulfilled the partial GET request for the resource
1488   and the enclosed payload is a partial representation as defined in &status-206;.
1489</t>
1490<t>
1491   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1492   freshness for 206 responses.
1493</t>
1494</section>
1495</section>
1496
1497<section title="Redirection 3xx" anchor="status.3xx">
1498<t>
1499   This class of status code indicates that further action needs to be
1500   taken by the user agent in order to fulfill the request.  The action
1501   required &MAY; be carried out by the user agent without interaction
1502   with the user if and only if the method used in the second request is
1503   known to be "safe", as defined in <xref target="safe.methods"/>.
1504   A client &SHOULD; detect infinite redirection loops, since such loops
1505   generate network traffic for each redirection.
1506</t>
1507<x:note>
1508  <t>
1509    <x:h>Note:</x:h> An earlier version of this specification recommended a
1510    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1511    Content developers need to be aware that some clients might
1512    implement such a fixed limitation.
1513  </t>
1514</x:note>
1515
1516<section title="300 Multiple Choices" anchor="status.300">
1517  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1518  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1519<t>
1520   The target resource has more than one
1521   representation, each with its own specific location, and agent-driven
1522   negotiation information (&content-negotiation;) is being provided so that
1523   the user (or user agent) can select a preferred representation by
1524   redirecting its request to that location.
1525</t>
1526<t>
1527   Unless it was a HEAD request, the response &SHOULD; include a representation
1528   containing a list of representation metadata and location(s) from
1529   which the user or user agent can choose the one most appropriate. The
1530   data format is specified by the media type given in the Content-Type
1531   header field. Depending upon the format and the capabilities of
1532   the user agent, selection of the most appropriate choice &MAY; be
1533   performed automatically. However, this specification does not define
1534   any standard for such automatic selection.
1535</t>
1536<t>
1537   If the server has a preferred choice of representation, it &SHOULD;
1538   include the specific URI for that representation in the Location
1539   field; user agents &MAY; use the Location field value for automatic
1540   redirection.
1541</t>
1542<t>
1543   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1544   freshness for 300 responses.
1545</t>
1546
1547</section>
1548
1549<section title="301 Moved Permanently" anchor="status.301">
1550  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1551  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1552<t>
1553   The target resource has been assigned a new permanent URI and any
1554   future references to this resource &SHOULD; use one of the returned
1555   URIs.  Clients with link editing capabilities ought to automatically
1556   re-link references to the effective request URI to one or more of the new
1557   references returned by the server, where possible.
1558</t>
1559<t>
1560   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1561   freshness for 301 responses.
1562</t>
1563<t>
1564   The new permanent URI &SHOULD; be given by the Location field in the
1565   response. Unless the request method was HEAD, the representation of the
1566   response &SHOULD; contain a short hypertext note with a hyperlink to
1567   the new URI(s).
1568</t>
1569<t>
1570   If the 301 status code is received in response to a request method
1571   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1572   then the request &MAY; be automatically redirected by the user agent without
1573   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1574   request unless it can be confirmed by the user, since this might
1575   change the conditions under which the request was issued.
1576</t>
1577<x:note>
1578  <t>
1579    <x:h>Note:</x:h> When automatically redirecting a POST request after
1580    receiving a 301 status code, some existing HTTP/1.0 user agents
1581    will erroneously change it into a GET request.
1582  </t>
1583</x:note>
1584</section>
1585
1586<section title="302 Found" anchor="status.302">
1587  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1588  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1589<t>
1590   The target resource resides temporarily under a different URI.
1591   Since the redirection might be altered on occasion, the client &SHOULD;
1592   continue to use the effective request URI for future requests.
1593</t>
1594<t>
1595   The temporary URI &SHOULD; be given by the Location field in the
1596   response. Unless the request method was HEAD, the representation of the
1597   response &SHOULD; contain a short hypertext note with a hyperlink to
1598   the new URI(s).
1599</t>
1600<t>
1601   If the 302 status code is received in response to a request method
1602   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1603   then the request &MAY; be automatically redirected by the user agent without
1604   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1605   request unless it can be confirmed by the user, since this might
1606   change the conditions under which the request was issued.
1607</t>
1608<x:note>
1609  <t>
1610    <x:h>Note:</x:h> HTTP/1.0 (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>)
1611    and the first version of HTTP/1.1 (<xref target="RFC2068" x:fmt="," x:sec ="10.3.3"/>)
1612    specify that the client is not allowed to change the method on the
1613    redirected request.  However, most existing user agent implementations
1614    treat 302 as if it were a 303 response, performing a GET on the Location
1615    field-value regardless of the original request method. Therefore, a
1616    previous version of this specification
1617    (<xref target="RFC2616" x:fmt="," x:sec="10.3.3"/>) has added the
1618    status codes
1619    <xref target="status.303" format="none">303</xref> and
1620    <xref target="status.307" format="none">307</xref> for servers that wish
1621    to make unambiguously clear which kind of reaction is expected of the
1622    client.
1623  </t>
1624</x:note>
1625</section>
1626
1627<section title="303 See Other" anchor="status.303">
1628  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1629  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1630<t>
1631   The server directs the user agent to a different resource, indicated
1632   by a URI in the Location header field, that provides an indirect
1633   response to the original request.  The user agent &MAY; perform a GET
1634   request on the URI in the Location field in order to obtain a
1635   representation corresponding to the response, be redirected again,
1636   or end with an error status.  The Location URI is not a substitute
1637   reference for the effective request URI.
1638</t>
1639<t>
1640   The 303 status code is generally applicable to any HTTP method.  It is
1641   primarily used to allow the output of a POST action to redirect
1642   the user agent to a selected resource, since doing so provides the
1643   information corresponding to the POST response in a form that
1644   can be separately identified, bookmarked, and cached independent
1645   of the original request.
1646</t>
1647<t>
1648   A 303 response to a GET request indicates that the requested
1649   resource does not have a representation of its own that can be
1650   transferred by the server over HTTP.  The Location URI indicates a
1651   resource that is descriptive of the target resource, such that the
1652   follow-on representation might be useful to recipients without
1653   implying that it adequately represents the target resource.
1654   Note that answers to the questions of what can be represented, what
1655   representations are adequate, and what might be a useful description
1656   are outside the scope of HTTP and thus entirely determined by the
1657   URI owner(s).
1658</t>
1659<t>
1660   Except for responses to a HEAD request, the representation of a 303
1661   response &SHOULD; contain a short hypertext note with a hyperlink
1662   to the Location URI.
1663</t>
1664</section>
1665
1666<section title="304 Not Modified" anchor="status.304">
1667  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1668  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1669  <rdf:Description>
1670    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1671  </rdf:Description>
1672<t>
1673   The response to the request has not been modified since the conditions
1674   indicated by the client's conditional GET request, as defined in &status-304;.
1675</t>
1676</section>
1677
1678<section title="305 Use Proxy" anchor="status.305">
1679  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1680  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1681<t>
1682   The 305 status code was defined in a previous version of this specification
1683   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1684</t>
1685</section>
1686
1687<section title="306 (Unused)" anchor="status.306">
1688  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1689  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1690<t>
1691   The 306 status code was used in a previous version of the
1692   specification, is no longer used, and the code is reserved.
1693</t>
1694</section>
1695
1696<section title="307 Temporary Redirect" anchor="status.307">
1697  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1698  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1699<t>
1700   The target resource resides temporarily under a different URI.
1701   Since the redirection can change over time, the client &SHOULD;
1702   continue to use the effective request URI for future requests.
1703</t>
1704<t>
1705   The temporary URI &SHOULD; be given by the Location field in the
1706   response. Unless the request method was HEAD, the representation of the
1707   response &SHOULD; contain a short hypertext note with a hyperlink to
1708   the new URI(s), since many pre-HTTP/1.1 user agents do not
1709   understand the 307 status code. Therefore, the note &SHOULD; contain the
1710   information necessary for a user to repeat the original request on
1711   the new URI.
1712</t>
1713<t>
1714   If the 307 status code is received in response to a request method
1715   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1716   then the request &MAY; be automatically redirected by the user agent without
1717   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1718   request unless it can be confirmed by the user, since this might
1719   change the conditions under which the request was issued.
1720</t>
1721</section>
1722</section>
1723
1724<section title="Client Error 4xx" anchor="status.4xx">
1725<t>
1726   The 4xx class of status code is intended for cases in which the
1727   client seems to have erred. Except when responding to a HEAD request,
1728   the server &SHOULD; include a representation containing an explanation of the
1729   error situation, and whether it is a temporary or permanent
1730   condition. These status codes are applicable to any request method.
1731   User agents &SHOULD; display any included representation to the user.
1732</t>
1733<t>
1734   If the client is sending data, a server implementation using TCP
1735   &SHOULD; be careful to ensure that the client acknowledges receipt of
1736   the packet(s) containing the response, before the server closes the
1737   input connection. If the client continues sending data to the server
1738   after the close, the server's TCP stack will send a reset packet to
1739   the client, which might erase the client's unacknowledged input buffers
1740   before they can be read and interpreted by the HTTP application.
1741</t>
1742
1743<section title="400 Bad Request" anchor="status.400">
1744  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1745  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1746<t>
1747   The server cannot or will not process the request, due to a client error (e.g.,
1748   malformed syntax).</t>
1749</section>
1750
1751<section title="401 Unauthorized" anchor="status.401">
1752  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1753  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1754  <rdf:Description>
1755    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1756  </rdf:Description>
1757<t>
1758   The request requires user authentication (see &status-401;).
1759</t>
1760</section>
1761
1762<section title="402 Payment Required" anchor="status.402">
1763  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1764  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1765<t>
1766   This code is reserved for future use.
1767</t>
1768</section>
1769
1770<section title="403 Forbidden" anchor="status.403">
1771  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1772  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1773<t>
1774   The server understood the request, but refuses to authorize it. Providing
1775   different user authentication credentials might be successful, but any
1776   credentials that were provided in the request are insufficient. The request
1777   &SHOULD-NOT; be repeated with the same credentials.
1778</t>
1779<t>
1780   If the request method was not HEAD and the server wishes to make
1781   public why the request has not been fulfilled, it &SHOULD; describe the
1782   reason for the refusal in the representation.  If the server does not wish to
1783   make this information available to the client, the status code 404
1784   (Not Found) &MAY; be used instead.
1785</t>
1786</section>
1787
1788<section title="404 Not Found" anchor="status.404">
1789  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1790  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1791<t>
1792   The server has not found anything matching the effective request URI. No
1793   indication is given of whether the condition is temporary or
1794   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1795   knows, through some internally configurable mechanism, that an old
1796   resource is permanently unavailable and has no forwarding address.
1797   This status code is commonly used when the server does not wish to
1798   reveal exactly why the request has been refused, or when no other
1799   response is applicable.
1800</t>
1801</section>
1802
1803<section title="405 Method Not Allowed" anchor="status.405">
1804  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1805  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1806<t>
1807   The method specified in the Request-Line is not allowed for the target
1808   resource. The response &MUST; include an Allow header field containing a
1809   list of valid methods for the requested resource.
1810</t>
1811</section>
1812
1813<section title="406 Not Acceptable" anchor="status.406">
1814  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1815  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1816<t>
1817   The resource identified by the request is only capable of generating
1818   response representations which have content characteristics not acceptable
1819   according to the Accept and Accept-* header fields sent in the request
1820   (see &p3-header-fields;).
1821</t>
1822<t>
1823   Unless it was a HEAD request, the response &SHOULD; include a representation
1824   containing a list of available representation characteristics and location(s)
1825   from which the user or user agent can choose the one most
1826   appropriate. The data format is specified by the media type given
1827   in the Content-Type header field. Depending upon the format and the
1828   capabilities of the user agent, selection of the most appropriate
1829   choice &MAY; be performed automatically. However, this specification
1830   does not define any standard for such automatic selection.
1831</t>
1832<x:note>
1833  <t>
1834    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1835    not acceptable according to the accept header fields sent in the
1836    request. In some cases, this might even be preferable to sending a
1837    406 response. User agents are encouraged to inspect the header fields of
1838    an incoming response to determine if it is acceptable.
1839  </t>
1840</x:note>
1841<t>
1842   If the response could be unacceptable, a user agent &SHOULD;
1843   temporarily stop receipt of more data and query the user for a
1844   decision on further actions.
1845</t>
1846</section>
1847
1848<section title="407 Proxy Authentication Required" anchor="status.407">
1849  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1850  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1851<t>
1852   This code is similar to 401 (Unauthorized), but indicates that the
1853   client must first authenticate itself with the proxy (see &status-407;).
1854</t>
1855</section>
1856
1857<section title="408 Request Timeout" anchor="status.408">
1858  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1859  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1860<t>
1861   The client did not produce a request within the time that the server
1862   was prepared to wait. The client &MAY; repeat the request without
1863   modifications at any later time.
1864</t>
1865</section>
1866
1867<section title="409 Conflict" anchor="status.409">
1868  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1869  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1870<t>
1871   The request could not be completed due to a conflict with the current
1872   state of the resource. This code is only allowed in situations where
1873   it is expected that the user might be able to resolve the conflict
1874   and resubmit the request. The response body &SHOULD; include enough
1875   information for the user to recognize the source of the conflict.
1876   Ideally, the response representation would include enough information for the
1877   user or user agent to fix the problem; however, that might not be
1878   possible and is not required.
1879</t>
1880<t>
1881   Conflicts are most likely to occur in response to a PUT request. For
1882   example, if versioning were being used and the representation being PUT
1883   included changes to a resource which conflict with those made by an
1884   earlier (third-party) request, the server might use the 409 response
1885   to indicate that it can't complete the request. In this case, the
1886   response representation would likely contain a list of the differences
1887   between the two versions in a format defined by the response
1888   Content-Type.
1889</t>
1890</section>
1891
1892<section title="410 Gone" anchor="status.410">
1893  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1894  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1895<t>
1896   The target resource is no longer available at the server and no
1897   forwarding address is known. This condition is expected to be
1898   considered permanent. Clients with link editing capabilities &SHOULD;
1899   delete references to the effective request URI after user approval. If the
1900   server does not know, or has no facility to determine, whether or not
1901   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1902   used instead.
1903</t>
1904<t>
1905   The 410 response is primarily intended to assist the task of web
1906   maintenance by notifying the recipient that the resource is
1907   intentionally unavailable and that the server owners desire that
1908   remote links to that resource be removed. Such an event is common for
1909   limited-time, promotional services and for resources belonging to
1910   individuals no longer working at the server's site. It is not
1911   necessary to mark all permanently unavailable resources as "gone" or
1912   to keep the mark for any length of time &mdash; that is left to the
1913   discretion of the server owner.
1914</t>
1915<t>
1916   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine freshness
1917   for 410 responses.
1918</t>
1919
1920</section>
1921
1922<section title="411 Length Required" anchor="status.411">
1923  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1924  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1925<t>
1926   The server refuses to accept the request without a defined Content-Length.
1927   The client &MAY; repeat the request if it adds a valid
1928   Content-Length header field containing the length of the message-body
1929   in the request message.
1930</t>
1931</section>
1932
1933<section title="412 Precondition Failed" anchor="status.412">
1934  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1935  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1936  <rdf:Description>
1937    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1938  </rdf:Description>
1939<t>
1940   The precondition given in one or more of the header fields
1941   evaluated to false when it was tested on the server, as defined in
1942   &status-412;.
1943</t>
1944</section>
1945
1946<section title="413 Request Representation Too Large" anchor="status.413">
1947  <iref primary="true" item="413 Request Representation Too Large (status code)" x:for-anchor=""/>
1948  <iref primary="true" item="Status Codes" subitem="413 Request Representation Too Large" x:for-anchor=""/>
1949<t>
1950   The server is refusing to process a request because the request
1951   representation is larger than the server is willing or able to process. The
1952   server &MAY; close the connection to prevent the client from continuing
1953   the request.
1954</t>
1955<t>
1956   If the condition is temporary, the server &SHOULD; include a Retry-After
1957   header field to indicate that it is temporary and after what
1958   time the client &MAY; try again.
1959</t>
1960</section>
1961
1962<section title="414 URI Too Long" anchor="status.414">
1963  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
1964  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
1965<t>
1966   The server is refusing to service the request because the effective request URI
1967   is longer than the server is willing to interpret. This rare
1968   condition is only likely to occur when a client has improperly
1969   converted a POST request to a GET request with long query
1970   information, when the client has descended into a URI "black hole" of
1971   redirection (e.g., a redirected URI prefix that points to a suffix of
1972   itself), or when the server is under attack by a client attempting to
1973   exploit security holes present in some servers using fixed-length
1974   buffers for reading or manipulating the effective request URI.
1975</t>
1976</section>
1977
1978<section title="415 Unsupported Media Type" anchor="status.415">
1979  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1980  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1981<t>
1982   The server is refusing to service the request because the request
1983   payload is in a format not supported by this request method on the
1984   target resource.
1985</t>
1986</section>
1987
1988<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1989  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1990  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1991  <rdf:Description>
1992    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1993  </rdf:Description>
1994<t>
1995   The request included a Range header field (&header-range;) and none of
1996   the range-specifier values in this field overlap the current extent
1997   of the selected resource. See &status-416;.
1998</t>
1999</section>
2000
2001<section title="417 Expectation Failed" anchor="status.417">
2002  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
2003  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
2004<t>
2005   The expectation given in an Expect header field (see <xref target="header.expect"/>)
2006   could not be met by this server, or, if the server is a proxy,
2007   the server has unambiguous evidence that the request could not be met
2008   by the next-hop server.
2009</t>
2010</section>
2011
2012<section title="426 Upgrade Required" anchor="status.426">
2013  <iref primary="true" item="426 Upgrade Required (status code)" x:for-anchor=""/>
2014  <iref primary="true" item="Status Codes" subitem="426 Upgrade Required" x:for-anchor=""/>
2015<t>
2016   The request can not be completed without a prior protocol upgrade. This
2017   response &MUST; include an Upgrade header field (&header-upgrade;)
2018   specifying the required protocols.
2019</t>
2020<figure>
2021<preamble>Example:</preamble>
2022<artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
2023HTTP/1.1 426 Upgrade Required
2024Upgrade: HTTP/2.0
2025Connection: Upgrade
2026
2027</artwork></figure>
2028<t>
2029   The server &SHOULD; include a message body in the 426 response which
2030   indicates in human readable form the reason for the error and describes any
2031   alternative courses which may be available to the user.
2032</t>
2033</section>
2034</section>
2035
2036<section title="Server Error 5xx" anchor="status.5xx">
2037<t>
2038   Response status codes beginning with the digit "5" indicate cases in
2039   which the server is aware that it has erred or is incapable of
2040   performing the request. Except when responding to a HEAD request, the
2041   server &SHOULD; include a representation containing an explanation of the
2042   error situation, and whether it is a temporary or permanent
2043   condition. User agents &SHOULD; display any included representation to the
2044   user. These response codes are applicable to any request method.
2045</t>
2046
2047<section title="500 Internal Server Error" anchor="status.500">
2048  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
2049  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
2050<t>
2051   The server encountered an unexpected condition which prevented it
2052   from fulfilling the request.
2053</t>
2054</section>
2055
2056<section title="501 Not Implemented" anchor="status.501">
2057  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
2058  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
2059<t>
2060   The server does not support the functionality required to fulfill the
2061   request. This is the appropriate response when the server does not
2062   recognize the request method and is not capable of supporting it for
2063   any resource.
2064</t>
2065</section>
2066
2067<section title="502 Bad Gateway" anchor="status.502">
2068  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
2069  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
2070<t>
2071   The server, while acting as a gateway or proxy, received an invalid
2072   response from the upstream server it accessed in attempting to
2073   fulfill the request.
2074</t>
2075</section>
2076
2077<section title="503 Service Unavailable" anchor="status.503">
2078  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
2079  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
2080<t>
2081   The server is currently unable or unwilling to handle the request due to
2082   reasons such as temporary overloading, maintenance of the server, or rate
2083   limiting of the client.
2084</t>
2085<t>
2086   The implication is that this is a temporary condition which will be
2087   alleviated after some delay. If known, the length of the delay &MAY; be
2088   indicated in a Retry-After header field (<xref target="header.retry-after"/>).
2089   If no Retry-After is given, the client &SHOULD; handle the response as it
2090   would for a 500 response.
2091</t>
2092<x:note>
2093  <t>
2094    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
2095    server must use it when becoming overloaded. Some servers might wish
2096    to simply refuse the connection.
2097  </t>
2098</x:note>
2099</section>
2100
2101<section title="504 Gateway Timeout" anchor="status.504">
2102  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
2103  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
2104<t>
2105   The server, while acting as a gateway or proxy, did not receive a
2106   timely response from the upstream server specified by the URI (e.g.,
2107   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
2108   to access in attempting to complete the request.
2109</t>
2110<x:note>
2111  <t>
2112    <x:h>Note</x:h> to implementors: some deployed proxies are known to
2113    return 400 or 500 when DNS lookups time out.
2114  </t>
2115</x:note>
2116</section>
2117
2118<section title="505 HTTP Version Not Supported" anchor="status.505">
2119  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
2120  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
2121<t>
2122   The server does not support, or refuses to support, the protocol
2123   version that was used in the request message. The server is
2124   indicating that it is unable or unwilling to complete the request
2125   using the same major version as the client, as described in &http-version;,
2126   other than with this error message. The response &SHOULD; contain
2127   a representation describing why that version is not supported and what other
2128   protocols are supported by that server.
2129</t>
2130
2131</section>
2132</section>
2133</section>
2134
2135
2136<section title="Header Field Definitions" anchor="header.fields">
2137<t>
2138   This section defines the syntax and semantics of HTTP/1.1 header fields
2139   related to request and response semantics.
2140</t>
2141
2142<section title="Allow" anchor="header.allow">
2143  <iref primary="true" item="Allow header field" x:for-anchor=""/>
2144  <iref primary="true" item="Header Fields" subitem="Allow" x:for-anchor=""/>
2145  <x:anchor-alias value="Allow"/>
2146<t>
2147   The "Allow" header field lists the set of methods advertised as
2148   supported by the target resource. The purpose of this field is strictly to
2149   inform the recipient of valid request methods associated with the resource.
2150</t>
2151<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/>
2152  <x:ref>Allow</x:ref> = #<x:ref>Method</x:ref>
2153</artwork></figure>
2154<t>
2155   Example of use:
2156</t>
2157<figure><artwork type="example">
2158  Allow: GET, HEAD, PUT
2159</artwork></figure>
2160<t>
2161   The actual set of allowed methods is defined by the origin server at the
2162   time of each request.
2163</t>
2164<t>
2165   A proxy &MUST-NOT; modify the Allow header field &mdash; it does not need to
2166   understand all the methods specified in order to handle them according to
2167   the generic message handling rules.
2168</t>
2169</section>
2170
2171<section title="Expect" anchor="header.expect">
2172  <iref primary="true" item="Expect header field" x:for-anchor=""/>
2173  <iref primary="true" item="Header Fields" subitem="Expect" x:for-anchor=""/>
2174  <x:anchor-alias value="Expect"/>
2175  <x:anchor-alias value="expectation"/>
2176  <x:anchor-alias value="expectation-extension"/>
2177  <x:anchor-alias value="expect-params"/>
2178<t>
2179   The "Expect" header field is used to indicate that particular
2180   server behaviors are required by the client.
2181</t>
2182<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Expect"/><iref primary="true" item="Grammar" subitem="expectation"/><iref primary="true" item="Grammar" subitem="expectation-extension"/><iref primary="true" item="Grammar" subitem="expect-params"/>
2183  <x:ref>Expect</x:ref>       = 1#<x:ref>expectation</x:ref>
2184 
2185  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
2186  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
2187                           *<x:ref>expect-params</x:ref> ]
2188  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
2189</artwork></figure>
2190<t>
2191   A server that does not understand or is unable to comply with any of
2192   the expectation values in the Expect field of a request &MUST; respond
2193   with appropriate error status code. The server &MUST; respond with a 417
2194   (Expectation Failed) status code if any of the expectations cannot be met
2195   or, if there are other problems with the request, some other 4xx
2196   status code.
2197</t>
2198<t>
2199   This header field is defined with extensible syntax to allow for
2200   future extensions. If a server receives a request containing an
2201   Expect field that includes an expectation-extension that it does not
2202   support, it &MUST; respond with a 417 (Expectation Failed) status code.
2203</t>
2204<t>
2205   Comparison of expectation values is case-insensitive for unquoted
2206   tokens (including the 100-continue token), and is case-sensitive for
2207   quoted-string expectation-extensions.
2208</t>
2209<t>
2210   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
2211   return a 417 (Expectation Failed) status code if it receives a request
2212   with an expectation that it cannot meet. However, the Expect
2213   header field itself is end-to-end; it &MUST; be forwarded if the
2214   request is forwarded.
2215</t>
2216<t>
2217   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
2218   Expect header field.
2219</t>
2220<t>
2221   See &use100; for the use of the 100 (Continue) status code.
2222</t>
2223</section>
2224
2225<section title="From" anchor="header.from">
2226  <iref primary="true" item="From header field" x:for-anchor=""/>
2227  <iref primary="true" item="Header Fields" subitem="From" x:for-anchor=""/>
2228  <x:anchor-alias value="From"/>
2229  <x:anchor-alias value="mailbox"/>
2230<t>
2231   The "From" header field, if given, &SHOULD; contain an Internet
2232   e-mail address for the human user who controls the requesting user
2233   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
2234   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
2235</t>
2236<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/>
2237  <x:ref>From</x:ref>    = <x:ref>mailbox</x:ref>
2238 
2239  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2240</artwork></figure>
2241<t>
2242   An example is:
2243</t>
2244<figure><artwork type="example">
2245  From: webmaster@example.org
2246</artwork></figure>
2247<t>
2248   This header field &MAY; be used for logging purposes and as a means for
2249   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2250   be used as an insecure form of access protection. The interpretation
2251   of this field is that the request is being performed on behalf of the
2252   person given, who accepts responsibility for the method performed. In
2253   particular, robot agents &SHOULD; include this header field so that the
2254   person responsible for running the robot can be contacted if problems
2255   occur on the receiving end.
2256</t>
2257<t>
2258   The Internet e-mail address in this field &MAY; be separate from the
2259   Internet host which issued the request. For example, when a request
2260   is passed through a proxy the original issuer's address &SHOULD; be
2261   used.
2262</t>
2263<t>
2264   The client &SHOULD-NOT;  send the From header field without the user's
2265   approval, as it might conflict with the user's privacy interests or
2266   their site's security policy. It is strongly recommended that the
2267   user be able to disable, enable, and modify the value of this field
2268   at any time prior to a request.
2269</t>
2270</section>
2271
2272<section title="Location" anchor="header.location">
2273  <iref primary="true" item="Location header field" x:for-anchor=""/>
2274  <iref primary="true" item="Header Fields" subitem="Location" x:for-anchor=""/>
2275  <x:anchor-alias value="Location"/>
2276<t>
2277   The "Location" header field is used to identify a newly created
2278   resource, or to redirect the recipient to a different location for
2279   completion of the request.
2280</t>
2281<t>
2282   For 201 (Created) responses, the Location is the URI of the new resource
2283   which was created by the request. For 3xx responses, the location &SHOULD;
2284   indicate the server's preferred URI for automatic redirection to the
2285   resource.
2286</t>
2287<t>
2288   The field value consists of a single URI-reference. When it has the form
2289   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2290   the final value is computed by resolving it against the effective request
2291   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
2292</t>
2293<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/>
2294  <x:ref>Location</x:ref> = <x:ref>URI-reference</x:ref>
2295</artwork></figure>
2296<figure>
2297<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical WSP below, it's necessary this way for xml2rfc-->
2298<artwork type="example">
2299  Location: http://www.example.org/pub/WWW/People.html#tim
2300</artwork></figure><figure><artwork type="example">  Location: /index.html
2301</artwork></figure>
2302<t>
2303   There are circumstances in which a fragment identifier in a Location URI
2304   would not be appropriate. For instance, when it appears in a 201 Created
2305   response, where the Location header field specifies the URI for the entire
2306   created resource.
2307</t>
2308<x:note>
2309  <t>
2310    <x:h>Note:</x:h> This specification does not define precedence rules
2311    for the case where the original URI, as navigated to by the user
2312    agent, and the Location header field value both contain fragment
2313    identifiers. Thus be aware that including fragment identifiers might
2314    inconvenience anyone relying on the semantics of the original URI's
2315    fragment identifier.
2316  </t>
2317</x:note>
2318<x:note>
2319  <t>
2320    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2321    from Location in that the Content-Location identifies the most specific
2322    resource corresponding to the enclosed representation.
2323    It is therefore possible for a response to contain header fields for
2324    both Location and Content-Location.
2325  </t>
2326</x:note>
2327</section>
2328
2329<section title="Max-Forwards" anchor="header.max-forwards">
2330  <iref primary="true" item="Max-Forwards header field" x:for-anchor=""/>
2331  <iref primary="true" item="Header Fields" subitem="Max-Forwards" x:for-anchor=""/>
2332  <x:anchor-alias value="Max-Forwards"/>
2333<t>
2334   The "Max-Forwards" header field provides a mechanism with the
2335   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2336   methods to limit the number of times that the request is forwarded by
2337   proxies. This can be useful when the client is attempting to
2338   trace a request which appears to be failing or looping in mid-chain.
2339</t>
2340<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/>
2341  <x:ref>Max-Forwards</x:ref> = 1*<x:ref>DIGIT</x:ref>
2342</artwork></figure>
2343<t>
2344   The Max-Forwards value is a decimal integer indicating the remaining
2345   number of times this request message can be forwarded.
2346</t>
2347<t>
2348   Each recipient of a TRACE or OPTIONS request
2349   containing a Max-Forwards header field &MUST; check and update its
2350   value prior to forwarding the request. If the received value is zero
2351   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2352   respond as the final recipient. If the received Max-Forwards value is
2353   greater than zero, then the forwarded message &MUST; contain an updated
2354   Max-Forwards field with a value decremented by one (1).
2355</t>
2356<t>
2357   The Max-Forwards header field &MAY; be ignored for all other request
2358   methods.
2359</t>
2360</section>
2361
2362<section title="Referer" anchor="header.referer">
2363  <iref primary="true" item="Referer header field" x:for-anchor=""/>
2364  <iref primary="true" item="Header Fields" subitem="Referer" x:for-anchor=""/>
2365  <x:anchor-alias value="Referer"/>
2366<t>
2367   The "Referer" [sic] header field allows the client to specify the
2368   URI of the resource from which the effective request URI was obtained (the
2369   "referrer", although the header field is misspelled.).
2370</t>
2371<t>
2372   The Referer header field allows servers to generate lists of back-links to
2373   resources for interest, logging, optimized caching, etc. It also allows
2374   obsolete or mistyped links to be traced for maintenance. Some servers use
2375   Referer as a means of controlling where they allow links from (so-called
2376   "deep linking"), but legitimate requests do not always
2377   contain a Referer header field.
2378</t>
2379<t>
2380   If the effective request URI was obtained from a source that does not have its own
2381   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
2382   sent with the value "about:blank", or not be sent at all. Note that this
2383   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2384</t>
2385<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/>
2386  <x:ref>Referer</x:ref> = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2387</artwork></figure>
2388<t>
2389   Example:
2390</t>
2391<figure><artwork type="example">
2392  Referer: http://www.example.org/hypertext/Overview.html
2393</artwork></figure>
2394<t>
2395   If the field value is a relative URI, it &SHOULD; be interpreted
2396   relative to the effective request URI. The URI &MUST-NOT; include a fragment. See
2397   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2398</t>
2399</section>
2400
2401<section title="Retry-After" anchor="header.retry-after">
2402  <iref primary="true" item="Retry-After header field" x:for-anchor=""/>
2403  <iref primary="true" item="Header Fields" subitem="Retry-After" x:for-anchor=""/>
2404  <x:anchor-alias value="Retry-After"/>
2405<t>
2406   The header "Retry-After" field can be used with a 503 (Service
2407   Unavailable) response to indicate how long the service is expected to
2408   be unavailable to the requesting client. This field &MAY; also be used
2409   with any 3xx (Redirection) response to indicate the minimum time the
2410   user-agent is asked wait before issuing the redirected request.
2411</t>
2412<t>
2413   The value of this field can be either an HTTP-date or an integer number
2414   of seconds (in decimal) after the time of the response.
2415</t>
2416<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/>
2417  <x:ref>Retry-After</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2418</artwork></figure>
2419<t anchor="rule.delta-seconds">
2420  <x:anchor-alias value="delta-seconds"/>
2421   Time spans are non-negative decimal integers, representing time in
2422   seconds.
2423</t>
2424<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2425  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2426</artwork></figure>
2427<t>
2428   Two examples of its use are
2429</t>
2430<figure><artwork type="example">
2431  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2432  Retry-After: 120
2433</artwork></figure>
2434<t>
2435   In the latter example, the delay is 2 minutes.
2436</t>
2437</section>
2438
2439<section title="Server" anchor="header.server">
2440  <iref primary="true" item="Server header field" x:for-anchor=""/>
2441  <iref primary="true" item="Header Fields" subitem="Server" x:for-anchor=""/>
2442  <x:anchor-alias value="Server"/>
2443<t>
2444   The "Server" header field contains information about the
2445   software used by the origin server to handle the request.
2446</t>
2447<t>
2448   The field can contain multiple product tokens (&product-tokens;) and
2449   comments (&header-fields;) identifying the server and any significant
2450   subproducts. The product tokens are listed in order of their significance
2451   for identifying the application.
2452</t>
2453<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/>
2454  <x:ref>Server</x:ref> = <x:ref>product</x:ref> *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2455</artwork></figure>
2456<t>
2457   Example:
2458</t>
2459<figure><artwork type="example">
2460  Server: CERN/3.0 libwww/2.17
2461</artwork></figure>
2462<t>
2463   If the response is being forwarded through a proxy, the proxy
2464   application &MUST-NOT; modify the Server header field. Instead, it
2465   &MUST; include a Via field (as described in &header-via;).
2466</t>
2467<x:note>
2468  <t>
2469    <x:h>Note:</x:h> Revealing the specific software version of the server might
2470    allow the server machine to become more vulnerable to attacks
2471    against software that is known to contain security holes. Server
2472    implementors are encouraged to make this field a configurable
2473    option.
2474  </t>
2475</x:note>
2476</section>
2477
2478<section title="User-Agent" anchor="header.user-agent">
2479  <iref primary="true" item="User-Agent header field" x:for-anchor=""/>
2480  <iref primary="true" item="Header Fields" subitem="User-Agent" x:for-anchor=""/>
2481  <x:anchor-alias value="User-Agent"/>
2482<t>
2483   The "User-Agent" header field contains information about the user
2484   agent originating the request. User agents &SHOULD; include this field with
2485   requests.
2486</t>
2487<t>
2488   Typically, it is used for statistical purposes, the tracing of protocol
2489   violations, and tailoring responses to avoid particular user agent
2490   limitations.
2491</t>
2492<t>
2493   The field can contain multiple product tokens (&product-tokens;)
2494   and comments (&header-fields;) identifying the agent and its
2495   significant subproducts. By convention, the product tokens are listed in
2496   order of their significance for identifying the application.
2497</t>
2498<t>
2499   Because this field is usually sent on every request a user agent makes,
2500   implementations are encouraged not to include needlessly fine-grained
2501   detail, and to limit (or even prohibit) the addition of subproducts by third
2502   parties. Overly long and detailed User-Agent field values make requests
2503   larger and can also be used to identify ("fingerprint") the user against
2504   their wishes.
2505</t>
2506<t>
2507   Likewise, implementations are encouraged not to use the product tokens of
2508   other implementations in order to declare compatibility with them, as this
2509   circumvents the purpose of the field. Finally, they are encouraged not to
2510   use comments to identify products; doing so makes the field value more
2511   difficult to parse.
2512</t>
2513<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/>
2514  <x:ref>User-Agent</x:ref> = <x:ref>product</x:ref> *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2515</artwork></figure>
2516<t>
2517   Example:
2518</t>
2519<figure><artwork type="example">
2520  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2521</artwork></figure>
2522</section>
2523
2524</section>
2525
2526<section title="IANA Considerations" anchor="IANA.considerations">
2527
2528<section title="Method Registry" anchor="method.registration">
2529<t>
2530  The registration procedure for HTTP request methods is defined by
2531  <xref target="method.registry"/> of this document.
2532</t>
2533<t>
2534   The HTTP Method Registry shall be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2535   and be populated with the registrations below:
2536</t>
2537<?BEGININC p2-semantics.iana-methods ?>
2538<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2539<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2540   <ttcol>Method</ttcol>
2541   <ttcol>Safe</ttcol>
2542   <ttcol>Reference</ttcol>
2543   <c>CONNECT</c>
2544   <c>no</c>
2545   <c>
2546      <xref target="CONNECT"/>
2547   </c>
2548   <c>DELETE</c>
2549   <c>no</c>
2550   <c>
2551      <xref target="DELETE"/>
2552   </c>
2553   <c>GET</c>
2554   <c>yes</c>
2555   <c>
2556      <xref target="GET"/>
2557   </c>
2558   <c>HEAD</c>
2559   <c>yes</c>
2560   <c>
2561      <xref target="HEAD"/>
2562   </c>
2563   <c>OPTIONS</c>
2564   <c>yes</c>
2565   <c>
2566      <xref target="OPTIONS"/>
2567   </c>
2568   <c>POST</c>
2569   <c>no</c>
2570   <c>
2571      <xref target="POST"/>
2572   </c>
2573   <c>PUT</c>
2574   <c>no</c>
2575   <c>
2576      <xref target="PUT"/>
2577   </c>
2578   <c>TRACE</c>
2579   <c>yes</c>
2580   <c>
2581      <xref target="TRACE"/>
2582   </c>
2583</texttable>
2584<!--(END)-->
2585<?ENDINC p2-semantics.iana-methods ?>
2586</section>
2587
2588<section title="Status Code Registry" anchor="status.code.registration">
2589<t>
2590   The registration procedure for HTTP Status Codes &mdash; previously defined
2591   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> &mdash; is now defined
2592   by <xref target="status.code.registry"/> of this document.
2593</t>
2594<t>
2595   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2596   shall be updated with the registrations below:
2597</t>
2598<?BEGININC p2-semantics.iana-status-codes ?>
2599<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2600<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2601   <ttcol>Value</ttcol>
2602   <ttcol>Description</ttcol>
2603   <ttcol>Reference</ttcol>
2604   <c>100</c>
2605   <c>Continue</c>
2606   <c>
2607      <xref target="status.100"/>
2608   </c>
2609   <c>101</c>
2610   <c>Switching Protocols</c>
2611   <c>
2612      <xref target="status.101"/>
2613   </c>
2614   <c>200</c>
2615   <c>OK</c>
2616   <c>
2617      <xref target="status.200"/>
2618   </c>
2619   <c>201</c>
2620   <c>Created</c>
2621   <c>
2622      <xref target="status.201"/>
2623   </c>
2624   <c>202</c>
2625   <c>Accepted</c>
2626   <c>
2627      <xref target="status.202"/>
2628   </c>
2629   <c>203</c>
2630   <c>Non-Authoritative Information</c>
2631   <c>
2632      <xref target="status.203"/>
2633   </c>
2634   <c>204</c>
2635   <c>No Content</c>
2636   <c>
2637      <xref target="status.204"/>
2638   </c>
2639   <c>205</c>
2640   <c>Reset Content</c>
2641   <c>
2642      <xref target="status.205"/>
2643   </c>
2644   <c>300</c>
2645   <c>Multiple Choices</c>
2646   <c>
2647      <xref target="status.300"/>
2648   </c>
2649   <c>301</c>
2650   <c>Moved Permanently</c>
2651   <c>
2652      <xref target="status.301"/>
2653   </c>
2654   <c>302</c>
2655   <c>Found</c>
2656   <c>
2657      <xref target="status.302"/>
2658   </c>
2659   <c>303</c>
2660   <c>See Other</c>
2661   <c>
2662      <xref target="status.303"/>
2663   </c>
2664   <c>305</c>
2665   <c>Use Proxy</c>
2666   <c>
2667      <xref target="status.305"/>
2668   </c>
2669   <c>306</c>
2670   <c>(Unused)</c>
2671   <c>
2672      <xref target="status.306"/>
2673   </c>
2674   <c>307</c>
2675   <c>Temporary Redirect</c>
2676   <c>
2677      <xref target="status.307"/>
2678   </c>
2679   <c>400</c>
2680   <c>Bad Request</c>
2681   <c>
2682      <xref target="status.400"/>
2683   </c>
2684   <c>402</c>
2685   <c>Payment Required</c>
2686   <c>
2687      <xref target="status.402"/>
2688   </c>
2689   <c>403</c>
2690   <c>Forbidden</c>
2691   <c>
2692      <xref target="status.403"/>
2693   </c>
2694   <c>404</c>
2695   <c>Not Found</c>
2696   <c>
2697      <xref target="status.404"/>
2698   </c>
2699   <c>405</c>
2700   <c>Method Not Allowed</c>
2701   <c>
2702      <xref target="status.405"/>
2703   </c>
2704   <c>406</c>
2705   <c>Not Acceptable</c>
2706   <c>
2707      <xref target="status.406"/>
2708   </c>
2709   <c>407</c>
2710   <c>Proxy Authentication Required</c>
2711   <c>
2712      <xref target="status.407"/>
2713   </c>
2714   <c>408</c>
2715   <c>Request Timeout</c>
2716   <c>
2717      <xref target="status.408"/>
2718   </c>
2719   <c>409</c>
2720   <c>Conflict</c>
2721   <c>
2722      <xref target="status.409"/>
2723   </c>
2724   <c>410</c>
2725   <c>Gone</c>
2726   <c>
2727      <xref target="status.410"/>
2728   </c>
2729   <c>411</c>
2730   <c>Length Required</c>
2731   <c>
2732      <xref target="status.411"/>
2733   </c>
2734   <c>413</c>
2735   <c>Request Representation Too Large</c>
2736   <c>
2737      <xref target="status.413"/>
2738   </c>
2739   <c>414</c>
2740   <c>URI Too Long</c>
2741   <c>
2742      <xref target="status.414"/>
2743   </c>
2744   <c>415</c>
2745   <c>Unsupported Media Type</c>
2746   <c>
2747      <xref target="status.415"/>
2748   </c>
2749   <c>417</c>
2750   <c>Expectation Failed</c>
2751   <c>
2752      <xref target="status.417"/>
2753   </c>
2754   <c>426</c>
2755   <c>Upgrade Required</c>
2756   <c>
2757      <xref target="status.426"/>
2758   </c>
2759   <c>500</c>
2760   <c>Internal Server Error</c>
2761   <c>
2762      <xref target="status.500"/>
2763   </c>
2764   <c>501</c>
2765   <c>Not Implemented</c>
2766   <c>
2767      <xref target="status.501"/>
2768   </c>
2769   <c>502</c>
2770   <c>Bad Gateway</c>
2771   <c>
2772      <xref target="status.502"/>
2773   </c>
2774   <c>503</c>
2775   <c>Service Unavailable</c>
2776   <c>
2777      <xref target="status.503"/>
2778   </c>
2779   <c>504</c>
2780   <c>Gateway Timeout</c>
2781   <c>
2782      <xref target="status.504"/>
2783   </c>
2784   <c>505</c>
2785   <c>HTTP Version Not Supported</c>
2786   <c>
2787      <xref target="status.505"/>
2788   </c>
2789</texttable>
2790<!--(END)-->
2791<?ENDINC p2-semantics.iana-status-codes ?>
2792</section>
2793<section title="Header Field Registration" anchor="header.field.registration">
2794<t>
2795   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
2796   with the permanent registrations below (see <xref target="RFC3864"/>):
2797</t>
2798<?BEGININC p2-semantics.iana-headers ?>
2799<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2800<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2801   <ttcol>Header Field Name</ttcol>
2802   <ttcol>Protocol</ttcol>
2803   <ttcol>Status</ttcol>
2804   <ttcol>Reference</ttcol>
2805
2806   <c>Allow</c>
2807   <c>http</c>
2808   <c>standard</c>
2809   <c>
2810      <xref target="header.allow"/>
2811   </c>
2812   <c>Expect</c>
2813   <c>http</c>
2814   <c>standard</c>
2815   <c>
2816      <xref target="header.expect"/>
2817   </c>
2818   <c>From</c>
2819   <c>http</c>
2820   <c>standard</c>
2821   <c>
2822      <xref target="header.from"/>
2823   </c>
2824   <c>Location</c>
2825   <c>http</c>
2826   <c>standard</c>
2827   <c>
2828      <xref target="header.location"/>
2829   </c>
2830   <c>Max-Forwards</c>
2831   <c>http</c>
2832   <c>standard</c>
2833   <c>
2834      <xref target="header.max-forwards"/>
2835   </c>
2836   <c>Referer</c>
2837   <c>http</c>
2838   <c>standard</c>
2839   <c>
2840      <xref target="header.referer"/>
2841   </c>
2842   <c>Retry-After</c>
2843   <c>http</c>
2844   <c>standard</c>
2845   <c>
2846      <xref target="header.retry-after"/>
2847   </c>
2848   <c>Server</c>
2849   <c>http</c>
2850   <c>standard</c>
2851   <c>
2852      <xref target="header.server"/>
2853   </c>
2854   <c>User-Agent</c>
2855   <c>http</c>
2856   <c>standard</c>
2857   <c>
2858      <xref target="header.user-agent"/>
2859   </c>
2860</texttable>
2861<!--(END)-->
2862<?ENDINC p2-semantics.iana-headers ?>
2863<t>
2864   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2865</t>
2866</section>
2867</section>
2868
2869<section title="Security Considerations" anchor="security.considerations">
2870<t>
2871   This section is meant to inform application developers, information
2872   providers, and users of the security limitations in HTTP/1.1 as
2873   described by this document. The discussion does not include
2874   definitive solutions to the problems revealed, though it does make
2875   some suggestions for reducing security risks.
2876</t>
2877
2878<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2879<t>
2880   Like any generic data transfer protocol, HTTP cannot regulate the
2881   content of the data that is transferred, nor is there any a priori
2882   method of determining the sensitivity of any particular piece of
2883   information within the context of any given request. Therefore,
2884   applications &SHOULD; supply as much control over this information as
2885   possible to the provider of that information. Four header fields are
2886   worth special mention in this context: Server, Via, Referer and From.
2887</t>
2888<t>
2889   Revealing the specific software version of the server might allow the
2890   server machine to become more vulnerable to attacks against software
2891   that is known to contain security holes. Implementors &SHOULD; make the
2892   Server header field a configurable option.
2893</t>
2894<t>
2895   Proxies which serve as a portal through a network firewall &SHOULD;
2896   take special precautions regarding the transfer of header information
2897   that identifies the hosts behind the firewall. In particular, they
2898   &SHOULD; remove, or replace with sanitized versions, any Via fields
2899   generated behind the firewall.
2900</t>
2901<t>
2902   The Referer header field allows reading patterns to be studied and reverse
2903   links drawn. Although it can be very useful, its power can be abused
2904   if user details are not separated from the information contained in
2905   the Referer. Even when the personal information has been removed, the
2906   Referer header field might indicate a private document's URI whose
2907   publication would be inappropriate.
2908</t>
2909<t>
2910   The information sent in the From field might conflict with the user's
2911   privacy interests or their site's security policy, and hence it
2912   &SHOULD-NOT;  be transmitted without the user being able to disable,
2913   enable, and modify the contents of the field. The user &MUST; be able
2914   to set the contents of this field within a user preference or
2915   application defaults configuration.
2916</t>
2917<t>
2918   We suggest, though do not require, that a convenient toggle interface
2919   be provided for the user to enable or disable the sending of From and
2920   Referer information.
2921</t>
2922<t>
2923   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref
2924   target="header.server"/>) header fields can sometimes be used to determine
2925   that a specific client or server have a particular security hole which might
2926   be exploited. Unfortunately, this same information is often used for other
2927   valuable purposes for which HTTP currently has no better mechanism.
2928</t>
2929<t>
2930   Furthermore, the User-Agent header field may contain enough entropy to be
2931   used, possibly in conjunction with other material, to uniquely identify the
2932   user.
2933</t>
2934<t>
2935   Some request methods, like TRACE (<xref target="TRACE"/>), expose information
2936   that was sent in request header fields within the body of their response.
2937   Clients &SHOULD; be careful with sensitive information, like Cookies,
2938   Authorization credentials, and other header fields that might be used to
2939   collect data from the client.
2940</t> 
2941</section>
2942
2943<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2944<t>
2945   Because the source of a link might be private information or might
2946   reveal an otherwise private information source, it is strongly
2947   recommended that the user be able to select whether or not the
2948   Referer field is sent. For example, a browser client could have a
2949   toggle switch for browsing openly/anonymously, which would
2950   respectively enable/disable the sending of Referer and From
2951   information.
2952</t>
2953<t>
2954   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2955   HTTP request if the referring page was transferred with a secure
2956   protocol.
2957</t>
2958<t>
2959   Authors of services &SHOULD-NOT; use GET-based forms for the submission of
2960   sensitive data because that data will be placed in the request-target. Many
2961   existing servers, proxies, and user agents log or display the request-target
2962   in places where it might be visible to third parties. Such services can
2963   use POST-based form submission instead.
2964</t>
2965</section>
2966
2967<section title="Location Headers and Spoofing" anchor="location.spoofing">
2968<t>
2969   If a single server supports multiple organizations that do not trust
2970   one another, then it &MUST; check the values of Location and Content-Location
2971   header fields in responses that are generated under control of
2972   said organizations to make sure that they do not attempt to
2973   invalidate resources over which they have no authority.
2974</t>
2975</section>
2976
2977<section title="Security Considerations for CONNECT">
2978<t>
2979   Since tunneled data is opaque to the proxy, there are additional
2980   risks to tunneling to other well-known or reserved ports.
2981   A HTTP client CONNECTing to port 25 could relay spam
2982   via SMTP, for example. As such, proxies &SHOULD; restrict CONNECT
2983   access to a small number of known ports.
2984</t>
2985</section>
2986
2987</section>
2988
2989<section title="Acknowledgments" anchor="acks">
2990<t>
2991  See &acks;.
2992</t>
2993</section>
2994</middle>
2995<back>
2996
2997<references title="Normative References">
2998
2999<reference anchor="Part1">
3000  <front>
3001    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
3002    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3003      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3004      <address><email>fielding@gbiv.com</email></address>
3005    </author>
3006    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3007      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3008      <address><email>jg@freedesktop.org</email></address>
3009    </author>
3010    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3011      <organization abbrev="HP">Hewlett-Packard Company</organization>
3012      <address><email>JeffMogul@acm.org</email></address>
3013    </author>
3014    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3015      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3016      <address><email>henrikn@microsoft.com</email></address>
3017    </author>
3018    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3019      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3020      <address><email>LMM@acm.org</email></address>
3021    </author>
3022    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3023      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3024      <address><email>paulle@microsoft.com</email></address>
3025    </author>
3026    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3027      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3028      <address><email>timbl@w3.org</email></address>
3029    </author>
3030    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3031      <organization abbrev="W3C">World Wide Web Consortium</organization>
3032      <address><email>ylafon@w3.org</email></address>
3033    </author>
3034    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3035      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3036      <address><email>julian.reschke@greenbytes.de</email></address>
3037    </author>
3038    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3039  </front>
3040  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
3041  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
3042</reference>
3043
3044<reference anchor="Part3">
3045  <front>
3046    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
3047    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3048      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3049      <address><email>fielding@gbiv.com</email></address>
3050    </author>
3051    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3052      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3053      <address><email>jg@freedesktop.org</email></address>
3054    </author>
3055    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3056      <organization abbrev="HP">Hewlett-Packard Company</organization>
3057      <address><email>JeffMogul@acm.org</email></address>
3058    </author>
3059    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3060      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3061      <address><email>henrikn@microsoft.com</email></address>
3062    </author>
3063    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3064      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3065      <address><email>LMM@acm.org</email></address>
3066    </author>
3067    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3068      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3069      <address><email>paulle@microsoft.com</email></address>
3070    </author>
3071    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3072      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3073      <address><email>timbl@w3.org</email></address>
3074    </author>
3075    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3076      <organization abbrev="W3C">World Wide Web Consortium</organization>
3077      <address><email>ylafon@w3.org</email></address>
3078    </author>
3079    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3080      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3081      <address><email>julian.reschke@greenbytes.de</email></address>
3082    </author>
3083    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3084  </front>
3085  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
3086  <x:source href="p3-payload.xml" basename="p3-payload"/>
3087</reference>
3088
3089<reference anchor="Part4">
3090  <front>
3091    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
3092    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3093      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3094      <address><email>fielding@gbiv.com</email></address>
3095    </author>
3096    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3097      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3098      <address><email>jg@freedesktop.org</email></address>
3099    </author>
3100    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3101      <organization abbrev="HP">Hewlett-Packard Company</organization>
3102      <address><email>JeffMogul@acm.org</email></address>
3103    </author>
3104    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3105      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3106      <address><email>henrikn@microsoft.com</email></address>
3107    </author>
3108    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3109      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3110      <address><email>LMM@acm.org</email></address>
3111    </author>
3112    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3113      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3114      <address><email>paulle@microsoft.com</email></address>
3115    </author>
3116    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3117      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3118      <address><email>timbl@w3.org</email></address>
3119    </author>
3120    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3121      <organization abbrev="W3C">World Wide Web Consortium</organization>
3122      <address><email>ylafon@w3.org</email></address>
3123    </author>
3124    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3125      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3126      <address><email>julian.reschke@greenbytes.de</email></address>
3127    </author>
3128    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3129  </front>
3130  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
3131  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
3132</reference>
3133
3134<reference anchor="Part5">
3135  <front>
3136    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
3137    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3138      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3139      <address><email>fielding@gbiv.com</email></address>
3140    </author>
3141    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3142      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3143      <address><email>jg@freedesktop.org</email></address>
3144    </author>
3145    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3146      <organization abbrev="HP">Hewlett-Packard Company</organization>
3147      <address><email>JeffMogul@acm.org</email></address>
3148    </author>
3149    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3150      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3151      <address><email>henrikn@microsoft.com</email></address>
3152    </author>
3153    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3154      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3155      <address><email>LMM@acm.org</email></address>
3156    </author>
3157    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3158      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3159      <address><email>paulle@microsoft.com</email></address>
3160    </author>
3161    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3162      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3163      <address><email>timbl@w3.org</email></address>
3164    </author>
3165    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3166      <organization abbrev="W3C">World Wide Web Consortium</organization>
3167      <address><email>ylafon@w3.org</email></address>
3168    </author>
3169    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3170      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3171      <address><email>julian.reschke@greenbytes.de</email></address>
3172    </author>
3173    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3174  </front>
3175  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
3176  <x:source href="p5-range.xml" basename="p5-range"/>
3177</reference>
3178
3179<reference anchor="Part6">
3180  <front>
3181    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
3182    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3183      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3184      <address><email>fielding@gbiv.com</email></address>
3185    </author>
3186    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3187      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3188      <address><email>jg@freedesktop.org</email></address>
3189    </author>
3190    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3191      <organization abbrev="HP">Hewlett-Packard Company</organization>
3192      <address><email>JeffMogul@acm.org</email></address>
3193    </author>
3194    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3195      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3196      <address><email>henrikn@microsoft.com</email></address>
3197    </author>
3198    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3199      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3200      <address><email>LMM@acm.org</email></address>
3201    </author>
3202    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3203      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3204      <address><email>paulle@microsoft.com</email></address>
3205    </author>
3206    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3207      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3208      <address><email>timbl@w3.org</email></address>
3209    </author>
3210    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3211      <organization abbrev="W3C">World Wide Web Consortium</organization>
3212      <address><email>ylafon@w3.org</email></address>
3213    </author>
3214    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
3215      <address><email>mnot@mnot.net</email></address>
3216    </author>
3217    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3218      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3219      <address><email>julian.reschke@greenbytes.de</email></address>
3220    </author>
3221    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3222  </front>
3223  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
3224  <x:source href="p6-cache.xml" basename="p6-cache"/>
3225</reference>
3226
3227<reference anchor="Part7">
3228  <front>
3229    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
3230    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3231      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3232      <address><email>fielding@gbiv.com</email></address>
3233    </author>
3234    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3235      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3236      <address><email>jg@freedesktop.org</email></address>
3237    </author>
3238    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3239      <organization abbrev="HP">Hewlett-Packard Company</organization>
3240      <address><email>JeffMogul@acm.org</email></address>
3241    </author>
3242    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3243      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3244      <address><email>henrikn@microsoft.com</email></address>
3245    </author>
3246    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3247      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3248      <address><email>LMM@acm.org</email></address>
3249    </author>
3250    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3251      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3252      <address><email>paulle@microsoft.com</email></address>
3253    </author>
3254    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3255      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3256      <address><email>timbl@w3.org</email></address>
3257    </author>
3258    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3259      <organization abbrev="W3C">World Wide Web Consortium</organization>
3260      <address><email>ylafon@w3.org</email></address>
3261    </author>
3262    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3263      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3264      <address><email>julian.reschke@greenbytes.de</email></address>
3265    </author>
3266    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3267  </front>
3268  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3269  <x:source href="p7-auth.xml" basename="p7-auth"/>
3270</reference>
3271
3272<reference anchor="RFC2119">
3273  <front>
3274    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3275    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3276      <organization>Harvard University</organization>
3277      <address><email>sob@harvard.edu</email></address>
3278    </author>
3279    <date month="March" year="1997"/>
3280  </front>
3281  <seriesInfo name="BCP" value="14"/>
3282  <seriesInfo name="RFC" value="2119"/>
3283</reference>
3284
3285<reference anchor="RFC3986">
3286 <front>
3287  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3288  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3289    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3290    <address>
3291       <email>timbl@w3.org</email>
3292       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3293    </address>
3294  </author>
3295  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3296    <organization abbrev="Day Software">Day Software</organization>
3297    <address>
3298      <email>fielding@gbiv.com</email>
3299      <uri>http://roy.gbiv.com/</uri>
3300    </address>
3301  </author>
3302  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3303    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3304    <address>
3305      <email>LMM@acm.org</email>
3306      <uri>http://larry.masinter.net/</uri>
3307    </address>
3308  </author>
3309  <date month='January' year='2005'></date>
3310 </front>
3311 <seriesInfo name="STD" value="66"/>
3312 <seriesInfo name="RFC" value="3986"/>
3313</reference>
3314
3315<reference anchor="RFC5234">
3316  <front>
3317    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3318    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3319      <organization>Brandenburg InternetWorking</organization>
3320      <address>
3321        <email>dcrocker@bbiw.net</email>
3322      </address> 
3323    </author>
3324    <author initials="P." surname="Overell" fullname="Paul Overell">
3325      <organization>THUS plc.</organization>
3326      <address>
3327        <email>paul.overell@thus.net</email>
3328      </address>
3329    </author>
3330    <date month="January" year="2008"/>
3331  </front>
3332  <seriesInfo name="STD" value="68"/>
3333  <seriesInfo name="RFC" value="5234"/>
3334</reference>
3335
3336</references>
3337
3338<references title="Informative References">
3339
3340<reference anchor="RFC1945">
3341  <front>
3342    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3343    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3344      <organization>MIT, Laboratory for Computer Science</organization>
3345      <address><email>timbl@w3.org</email></address>
3346    </author>
3347    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3348      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3349      <address><email>fielding@ics.uci.edu</email></address>
3350    </author>
3351    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3352      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3353      <address><email>frystyk@w3.org</email></address>
3354    </author>
3355    <date month="May" year="1996"/>
3356  </front>
3357  <seriesInfo name="RFC" value="1945"/>
3358</reference>
3359
3360<reference anchor="RFC2068">
3361  <front>
3362    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3363    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3364      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3365      <address><email>fielding@ics.uci.edu</email></address>
3366    </author>
3367    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3368      <organization>MIT Laboratory for Computer Science</organization>
3369      <address><email>jg@w3.org</email></address>
3370    </author>
3371    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3372      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3373      <address><email>mogul@wrl.dec.com</email></address>
3374    </author>
3375    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3376      <organization>MIT Laboratory for Computer Science</organization>
3377      <address><email>frystyk@w3.org</email></address>
3378    </author>
3379    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3380      <organization>MIT Laboratory for Computer Science</organization>
3381      <address><email>timbl@w3.org</email></address>
3382    </author>
3383    <date month="January" year="1997"/>
3384  </front>
3385  <seriesInfo name="RFC" value="2068"/>
3386</reference>
3387
3388<reference anchor="RFC2616">
3389  <front>
3390    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3391    <author initials="R." surname="Fielding" fullname="R. Fielding">
3392      <organization>University of California, Irvine</organization>
3393      <address><email>fielding@ics.uci.edu</email></address>
3394    </author>
3395    <author initials="J." surname="Gettys" fullname="J. Gettys">
3396      <organization>W3C</organization>
3397      <address><email>jg@w3.org</email></address>
3398    </author>
3399    <author initials="J." surname="Mogul" fullname="J. Mogul">
3400      <organization>Compaq Computer Corporation</organization>
3401      <address><email>mogul@wrl.dec.com</email></address>
3402    </author>
3403    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3404      <organization>MIT Laboratory for Computer Science</organization>
3405      <address><email>frystyk@w3.org</email></address>
3406    </author>
3407    <author initials="L." surname="Masinter" fullname="L. Masinter">
3408      <organization>Xerox Corporation</organization>
3409      <address><email>masinter@parc.xerox.com</email></address>
3410    </author>
3411    <author initials="P." surname="Leach" fullname="P. Leach">
3412      <organization>Microsoft Corporation</organization>
3413      <address><email>paulle@microsoft.com</email></address>
3414    </author>
3415    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3416      <organization>W3C</organization>
3417      <address><email>timbl@w3.org</email></address>
3418    </author>
3419    <date month="June" year="1999"/>
3420  </front>
3421  <seriesInfo name="RFC" value="2616"/>
3422</reference>
3423
3424<reference anchor='RFC2817'>
3425  <front>
3426    <title>Upgrading to TLS Within HTTP/1.1</title>
3427    <author initials='R.' surname='Khare' fullname='R. Khare'>
3428      <organization>4K Associates / UC Irvine</organization>
3429      <address><email>rohit@4K-associates.com</email></address>
3430    </author>
3431    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3432      <organization>Agranat Systems, Inc.</organization>
3433      <address><email>lawrence@agranat.com</email></address>
3434    </author>
3435    <date year='2000' month='May' />
3436  </front>
3437  <seriesInfo name='RFC' value='2817' />
3438</reference>
3439
3440<reference anchor='RFC3864'>
3441  <front>
3442    <title>Registration Procedures for Message Header Fields</title>
3443    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3444      <organization>Nine by Nine</organization>
3445      <address><email>GK-IETF@ninebynine.org</email></address>
3446    </author>
3447    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3448      <organization>BEA Systems</organization>
3449      <address><email>mnot@pobox.com</email></address>
3450    </author>
3451    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3452      <organization>HP Labs</organization>
3453      <address><email>JeffMogul@acm.org</email></address>
3454    </author>
3455    <date year='2004' month='September' />
3456  </front>
3457  <seriesInfo name='BCP' value='90' />
3458  <seriesInfo name='RFC' value='3864' />
3459</reference>
3460
3461<reference anchor='RFC5226'>
3462  <front>
3463    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3464    <author initials='T.' surname='Narten' fullname='T. Narten'>
3465      <organization>IBM</organization>
3466      <address><email>narten@us.ibm.com</email></address>
3467    </author>
3468    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3469      <organization>Google</organization>
3470      <address><email>Harald@Alvestrand.no</email></address>
3471    </author>
3472    <date year='2008' month='May' />
3473  </front>
3474  <seriesInfo name='BCP' value='26' />
3475  <seriesInfo name='RFC' value='5226' />
3476</reference>
3477
3478<reference anchor="RFC5322">
3479  <front>
3480    <title>Internet Message Format</title>
3481    <author initials="P." surname="Resnick" fullname="P. Resnick">
3482      <organization>Qualcomm Incorporated</organization>
3483    </author>
3484    <date year="2008" month="October"/>
3485  </front> 
3486  <seriesInfo name="RFC" value="5322"/>
3487</reference>
3488
3489<reference anchor='RFC5789'>
3490  <front>
3491    <title>PATCH Method for HTTP</title>
3492    <author initials='L.' surname='Dusseault' fullname='L. Dusseault'>
3493      <organization>Linden Lab</organization>
3494    </author>
3495    <author initials='J.' surname='Snell' fullname='J. Snell' />
3496    <date year='2010' month='March' />
3497  </front>
3498  <seriesInfo name='RFC' value='5789' />
3499</reference>
3500
3501</references>
3502
3503<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3504<t>
3505  This document takes over the Status Code Registry, previously defined
3506  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3507  (<xref target="status.code.registry"/>)
3508</t>
3509<t>
3510  Clarify definition of POST.
3511  (<xref target="POST"/>)
3512</t>
3513<t>
3514  Remove requirement to handle all Content-* header fields; ban use of
3515  Content-Range with PUT.
3516  (<xref target="PUT"/>)
3517</t>
3518<t>
3519  Take over definition of CONNECT method from <xref target="RFC2817"/>.
3520  (<xref target="CONNECT"/>)
3521</t>
3522<t>
3523  Broadened the definition of 203 (Non-Authoritative Information) to include
3524  cases of payload transformations as well.
3525  (<xref target="status.203"/>)
3526</t>
3527<t>
3528  Failed to consider that there are
3529  many other request methods that are safe to automatically redirect,
3530  and further that the user agent is able to make that determination
3531  based on the request method semantics.
3532  (Sections <xref format="counter" target="status.301"/>,
3533  <xref format="counter" target="status.302"/> and
3534  <xref format="counter" target="status.307"/>)
3535</t>
3536<t>
3537  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3538  It used to indicate that the target resource must be accessed through the
3539  proxy given by the Location field. The Location field gave the URI of the
3540  proxy. The recipient was expected to repeat this single request via the proxy.
3541  (<xref target="status.305"/>)
3542</t>
3543<t>
3544  Define status 426 (Upgrade Required) (this was incorporated from
3545  <xref target="RFC2817"/>).
3546  (<xref target="status.426"/>)
3547</t>
3548<t>
3549  Change ABNF productions for header fields to only define the field value.
3550  (<xref target="header.fields"/>)
3551</t>
3552<t>
3553  Reclassify "Allow" as response header field, removing the option to
3554  specify it in a PUT request.
3555  Relax the server requirement on the contents of the Allow header field and
3556  remove requirement on clients to always trust the header field value.
3557  (<xref target="header.allow"/>)
3558</t>
3559<t>
3560  Correct syntax of Location header field to allow URI references (including
3561  relative references and fragments), as referred symbol "absoluteURI" wasn't
3562  what was expected, and add some clarifications as to when use of fragments
3563  would not be appropriate.
3564  (<xref target="header.location"/>)
3565</t>
3566<t>
3567  Restrict Max-Forwards header field to OPTIONS and TRACE (previously,
3568  extension methods could have used it as well).
3569  (<xref target="header.max-forwards"/>)
3570</t>
3571<t>
3572  Allow Referer field value of "about:blank" as alternative to not specifying it.
3573  (<xref target="header.referer"/>)
3574</t>
3575<t>
3576  In the description of the Server header field, the Via field
3577  was described as a SHOULD. The requirement was and is stated
3578  correctly in the description of the Via header field in &header-via;.
3579  (<xref target="header.server"/>)
3580</t>
3581</section>
3582
3583<?BEGININC p2-semantics.abnf-appendix ?>
3584<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3585<figure>
3586<artwork type="abnf" name="p2-semantics.parsed-abnf">
3587<x:ref>Allow</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3588
3589<x:ref>Expect</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3590
3591<x:ref>From</x:ref> = mailbox
3592
3593<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 6.1&gt;
3594
3595<x:ref>Location</x:ref> = URI-reference
3596
3597<x:ref>Max-Forwards</x:ref> = 1*DIGIT
3598<x:ref>Method</x:ref> = token
3599
3600<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
3601
3602<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3603<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
3604<x:ref>Referer</x:ref> = absolute-URI / partial-URI
3605<x:ref>Retry-After</x:ref> = HTTP-date / delta-seconds
3606
3607<x:ref>Server</x:ref> = product *( RWS ( product / comment ) )
3608<x:ref>Status-Code</x:ref> = 3DIGIT
3609
3610<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.7&gt;
3611<x:ref>User-Agent</x:ref> = product *( RWS ( product / comment ) )
3612
3613<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.7&gt;
3614
3615<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2&gt;
3616
3617<x:ref>delta-seconds</x:ref> = 1*DIGIT
3618
3619<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
3620<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
3621<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
3622 *expect-params ]
3623
3624<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
3625
3626<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
3627
3628<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.7&gt;
3629<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 6.3&gt;
3630
3631<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
3632
3633<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
3634</artwork>
3635</figure>
3636<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
3637; Allow defined but not used
3638; Expect defined but not used
3639; From defined but not used
3640; Location defined but not used
3641; Max-Forwards defined but not used
3642; Reason-Phrase defined but not used
3643; Referer defined but not used
3644; Retry-After defined but not used
3645; Server defined but not used
3646; Status-Code defined but not used
3647; User-Agent defined but not used
3648</artwork></figure></section>
3649<?ENDINC p2-semantics.abnf-appendix ?>
3650
3651<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3652
3653<section title="Since RFC 2616">
3654<t>
3655  Extracted relevant partitions from <xref target="RFC2616"/>.
3656</t>
3657</section>
3658
3659<section title="Since draft-ietf-httpbis-p2-semantics-00">
3660<t>
3661  Closed issues:
3662  <list style="symbols"> 
3663    <t>
3664      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3665      "Via is a MUST"
3666      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3667    </t>
3668    <t>
3669      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3670      "Fragments allowed in Location"
3671      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3672    </t>
3673    <t>
3674      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3675      "Safe Methods vs Redirection"
3676      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3677    </t>
3678    <t>
3679      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3680      "Revise description of the POST method"
3681      (<eref target="http://purl.org/NET/http-errata#post"/>)
3682    </t>
3683    <t>
3684      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3685      "Normative and Informative references"
3686    </t>
3687    <t>
3688      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3689      "RFC2606 Compliance"
3690    </t>
3691    <t>
3692      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3693      "Informative references"
3694    </t>
3695    <t>
3696      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3697      "Redundant cross-references"
3698    </t>
3699  </list>
3700</t>
3701<t>
3702  Other changes:
3703  <list style="symbols"> 
3704    <t>
3705      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3706    </t>
3707  </list>
3708</t>
3709</section>
3710
3711<section title="Since draft-ietf-httpbis-p2-semantics-01">
3712<t>
3713  Closed issues:
3714  <list style="symbols"> 
3715    <t>
3716      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3717      "PUT side effects"
3718    </t>
3719    <t>
3720      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3721      "Duplicate Host header requirements"
3722    </t>
3723  </list>
3724</t>
3725<t>
3726  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3727  <list style="symbols"> 
3728    <t>
3729      Move "Product Tokens" section (back) into Part 1, as "token" is used
3730      in the definition of the Upgrade header field.
3731    </t>
3732    <t>
3733      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3734    </t>
3735    <t>
3736      Copy definition of delta-seconds from Part6 instead of referencing it.
3737    </t>
3738  </list>
3739</t>
3740</section>
3741
3742<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3743<t>
3744  Closed issues:
3745  <list style="symbols"> 
3746    <t>
3747      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3748      "Requiring Allow in 405 responses"
3749    </t>
3750    <t>
3751      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3752      "Status Code Registry"
3753    </t>
3754    <t>
3755      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3756      "Redirection vs. Location"
3757    </t>
3758    <t>
3759      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3760      "Cacheability of 303 response"
3761    </t>
3762    <t>
3763      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3764      "305 Use Proxy"
3765    </t>
3766    <t>
3767      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3768      "Classification for Allow header"
3769    </t>
3770    <t>
3771      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3772      "PUT - 'store under' vs 'store at'"
3773    </t>
3774  </list>
3775</t>
3776<t>
3777  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3778  <list style="symbols"> 
3779    <t>
3780      Reference RFC 3984, and update header field registrations for headers defined
3781      in this document.
3782    </t>
3783  </list>
3784</t>
3785<t>
3786  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3787  <list style="symbols"> 
3788    <t>
3789      Replace string literals when the string really is case-sensitive (method).
3790    </t>
3791  </list>
3792</t>
3793</section>
3794
3795<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3796<t>
3797  Closed issues:
3798  <list style="symbols"> 
3799    <t>
3800      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
3801      "OPTIONS request bodies"
3802    </t>
3803    <t>
3804      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
3805      "Description of CONNECT should refer to RFC2817"
3806    </t>
3807    <t>
3808      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
3809      "Location Content-Location reference request/response mixup"
3810    </t>
3811  </list>
3812</t>
3813<t>
3814  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
3815  <list style="symbols"> 
3816    <t>
3817      Added initial proposal for registration process, plus initial
3818      content (non-HTTP/1.1 methods to be added by a separate specification).
3819    </t>
3820  </list>
3821</t>
3822</section>
3823
3824<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3825<t>
3826  Closed issues:
3827  <list style="symbols"> 
3828    <t>
3829      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3830      "Content-*"
3831    </t>
3832    <t>
3833      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3834      "RFC 2822 is updated by RFC 5322"
3835    </t>
3836  </list>
3837</t>
3838<t>
3839  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3840  <list style="symbols"> 
3841    <t>
3842      Use "/" instead of "|" for alternatives.
3843    </t>
3844    <t>
3845      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3846      whitespace ("OWS") and required whitespace ("RWS").
3847    </t>
3848    <t>
3849      Rewrite ABNFs to spell out whitespace rules, factor out
3850      header field value format definitions.
3851    </t>
3852  </list>
3853</t>
3854</section>
3855
3856<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3857<t>
3858  Closed issues:
3859  <list style="symbols"> 
3860    <t>
3861      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
3862      "Reason-Phrase BNF"
3863    </t>
3864  </list>
3865</t>
3866<t>
3867  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3868  <list style="symbols"> 
3869    <t>
3870      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3871    </t>
3872  </list>
3873</t>
3874</section>
3875
3876<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
3877<t>
3878  Closed issues:
3879  <list style="symbols"> 
3880    <t>
3881      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
3882      "Clarify when Referer is sent"
3883    </t>
3884    <t>
3885      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
3886      "status codes vs methods"
3887    </t>
3888    <t>
3889      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
3890      "Do not require "updates" relation for specs that register status codes or method names"
3891    </t>
3892  </list>
3893</t>
3894</section>
3895
3896<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
3897<t>
3898  Closed issues:
3899  <list style="symbols"> 
3900    <t>
3901      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
3902      "Idempotency"
3903    </t>
3904    <t>
3905      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
3906      "TRACE security considerations"
3907    </t>
3908    <t>
3909      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
3910      "Clarify rules for determining what entities a response carries"
3911    </t>
3912    <t>
3913      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
3914      "update note citing RFC 1945 and 2068"
3915    </t>
3916    <t>
3917      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
3918      "update note about redirect limit"
3919    </t>
3920    <t>
3921      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
3922      "Location header ABNF should use 'URI'"
3923    </t>
3924    <t>
3925      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
3926      "fragments in Location vs status 303"
3927    </t>
3928    <t>
3929      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
3930      "move IANA registrations for optional status codes"
3931    </t>
3932  </list>
3933</t>
3934<t>
3935  Partly resolved issues:
3936  <list style="symbols"> 
3937    <t>
3938      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
3939      "Are OPTIONS and TRACE safe?"
3940    </t>
3941  </list>
3942</t>
3943</section>
3944
3945<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
3946<t>
3947  Closed issues:
3948  <list style="symbols"> 
3949    <t>
3950      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3951      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
3952      status codes when fixing this previously)
3953    </t>
3954  </list>
3955</t>
3956</section>
3957
3958<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
3959<t>
3960  Closed issues:
3961  <list style="symbols"> 
3962    <t>
3963      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
3964      "Fragment combination / precedence during redirects"
3965    </t>
3966  </list>
3967</t>
3968<t>
3969  Partly resolved issues:
3970  <list style="symbols"> 
3971    <t>
3972      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
3973      "Location header payload handling"
3974    </t>
3975    <t>
3976      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
3977      "Term for the requested resource's URI"
3978    </t>
3979  </list>
3980</t>
3981</section>
3982
3983<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
3984<t>
3985  Closed issues:
3986  <list style="symbols"> 
3987    <t>
3988      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
3989      "Clarify 'Requested Variant'"
3990    </t>
3991    <t>
3992      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
3993      "Clarify entity / representation / variant terminology"
3994    </t>
3995    <t>
3996      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/139"/>:
3997      "Methods and Caching"
3998    </t>
3999    <t>
4000      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/190"/>:
4001      "OPTIONS vs Max-Forwards"
4002    </t>
4003    <t>
4004      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/199"/>:
4005      "Status codes and caching"
4006    </t>
4007    <t>
4008      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
4009      "consider removing the 'changes from 2068' sections"
4010    </t>
4011  </list>
4012</t>
4013</section>
4014
4015<section title="Since draft-ietf-httpbis-p2-semantics-11" anchor="changes.since.11">
4016<t>
4017  Closed issues:
4018  <list style="symbols"> 
4019    <t>
4020      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/229"/>:
4021      "Considerations for new status codes"
4022    </t>
4023    <t>
4024      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/230"/>:
4025      "Considerations for new methods"
4026    </t>
4027    <t>
4028      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/232"/>:
4029      "User-Agent guidelines" (relating to the 'User-Agent' header field)
4030    </t>
4031  </list>
4032</t>
4033</section>
4034
4035<section title="Since draft-ietf-httpbis-p2-semantics-12" anchor="changes.since.12">
4036<t>
4037  Closed issues:
4038  <list style="symbols"> 
4039    <t>
4040      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4041      "Fragment combination / precedence during redirects" (added warning
4042      about having a fragid on the redirect may cause inconvenience in
4043      some cases)
4044    </t>
4045    <t>
4046      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/79"/>:
4047      "Content-* vs. PUT"
4048    </t>
4049    <t>
4050      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/88"/>:
4051      "205 Bodies"
4052    </t>
4053    <t>
4054      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/102"/>:
4055      "Understanding Content-* on non-PUT requests"
4056    </t>
4057    <t>
4058      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
4059      "Content-*"
4060    </t>
4061    <t>
4062      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/104"/>:
4063      "Header type defaulting"
4064    </t>
4065    <t>
4066      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
4067      "PUT - 'store under' vs 'store at'"
4068    </t>
4069    <t>
4070      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/137"/>:
4071      "duplicate ABNF for Reason-Phrase"
4072    </t>
4073    <t>
4074      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/180"/>:
4075      "Note special status of Content-* prefix in header registration procedures"
4076    </t>
4077    <t>
4078      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/203"/>:
4079      "Max-Forwards vs extension methods"
4080    </t>
4081    <t>
4082      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/213"/>:
4083      "What is the value space of HTTP status codes?" (actually fixed in
4084      draft-ietf-httpbis-p2-semantics-11)
4085    </t>
4086    <t>
4087      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/224"/>:
4088      "Header Classification"
4089    </t>
4090    <t>
4091      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/225"/>:
4092      "PUT side effect: invalidation or just stale?"
4093    </t>
4094    <t>
4095      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/226"/>:
4096      "proxies not supporting certain methods"
4097    </t>
4098    <t>
4099      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/239"/>:
4100      "Migrate CONNECT from RFC2817 to p2"
4101    </t>
4102    <t>
4103      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/240"/>:
4104      "Migrate Upgrade details from RFC2817"
4105    </t>
4106    <t>
4107      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/267"/>:
4108      "clarify PUT semantics'"
4109    </t>
4110    <t>
4111      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/275"/>:
4112      "duplicate ABNF for 'Method'"
4113    </t>
4114    <t>
4115      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4116      "untangle ABNFs for header fields"
4117    </t>
4118  </list>
4119</t>
4120</section>
4121
4122<section title="Since draft-ietf-httpbis-p2-semantics-13" anchor="changes.since.13">
4123<t>
4124  Closed issues:
4125  <list style="symbols"> 
4126    <t>
4127      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4128      "untangle ABNFs for header fields"
4129    </t>
4130    <t>
4131      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/251"/>:
4132      "message-body in CONNECT request"
4133    </t>
4134  </list>
4135</t>
4136</section>
4137
4138<section title="Since draft-ietf-httpbis-p2-semantics-14" anchor="changes.since.14">
4139<t>
4140  Closed issues:
4141  <list style="symbols"> 
4142    <t>
4143      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/255"/>:
4144      "Clarify status code for rate limiting"
4145    </t>
4146    <t>
4147      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/294"/>:
4148      "clarify 403 forbidden"
4149    </t>
4150    <t>
4151      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/296"/>:
4152      "Clarify 203 Non-Authoritative Information"
4153    </t>
4154    <t>
4155      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/298"/>:
4156      "update default reason phrase for 413"
4157    </t>
4158  </list>
4159</t>
4160</section>
4161
4162<section title="Since draft-ietf-httpbis-p2-semantics-15" anchor="changes.since.15">
4163<t>
4164  Closed issues:
4165  <list style="symbols"> 
4166    <t>
4167      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/285"/>:
4168      "Strength of requirements on Accept re: 406"
4169    </t>
4170    <t>
4171      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/303"/>:
4172      "400 response isn't generic"
4173    </t>
4174  </list>
4175</t>
4176</section>
4177</section>
4178
4179</back>
4180</rfc>
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