source: draft-ietf-httpbis/latest/p2-semantics.xml @ 1515

Last change on this file since 1515 was 1515, checked in by julian.reschke@…, 8 years ago

State that the Content-Type describes the payload only one (related to #332)

  • Property svn:eol-style set to native
  • Property svn:mime-type set to text/xml
File size: 195.5 KB
Line 
1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD NOT</bcp14>">
14  <!ENTITY ID-VERSION "latest">
15  <!ENTITY ID-MONTH "January">
16  <!ENTITY ID-YEAR "2012">
17  <!ENTITY mdash "&#8212;">
18  <!ENTITY architecture               "<xref target='Part1' x:rel='#architecture' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
19  <!ENTITY notation                   "<xref target='Part1' x:rel='#notation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY acks                       "<xref target='Part1' x:rel='#acks' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY messaging                  "<xref target='Part1' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY payload                    "<xref target='Part3' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23  <!ENTITY conditional                "<xref target='Part4' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
24  <!ENTITY range                      "<xref target='Part5' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
25  <!ENTITY caching                    "<xref target='Part6' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
26  <!ENTITY auth                       "<xref target='Part7' 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 agent-driven-negotiation   "<xref target='Part3' x:rel='#agent-driven.negotiation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
29  <!ENTITY notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY field-rules                "<xref target='Part1' x:rel='#field.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY uri                        "<xref target='Part1' x:rel='#uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY effective-request-uri      "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY intermediaries             "<xref target='Part1' x:rel='#intermediaries' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY chunked-encoding           "<xref target='Part1' x:rel='#chunked.encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY request-target             "<xref target='Part1' x:rel='#request-target' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
42  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
43  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
44  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
45  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
46  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
47  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
48  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
49  <!ENTITY header-connection          "<xref target='Part1' x:rel='#header.connection' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
50  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
51  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
52  <!ENTITY header-content-type        "<xref target='Part3' x:rel='#header.content-type' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
53  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
54  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
55  <!ENTITY header-fields              "<xref target='Part1' x:rel='#header.fields' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
56  <!ENTITY header-host                "<xref target='Part1' x:rel='#header.host' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
57  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
58  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
59  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
60  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
61  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
62  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
63  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
64  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
65  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
66  <!ENTITY header-upgrade             "<xref target='Part1' x:rel='#header.upgrade' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
67  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.te' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
68  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
69  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
70  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
71  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
72  <!ENTITY media-types                "<xref target='Part3' x:rel='#media.types' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
73  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
74  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
75  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='#internet.media.type.message.http' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
76  <!ENTITY status-206                 "<xref target='Part5' x:rel='#status.206' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
77  <!ENTITY status-304                 "<xref target='Part4' x:rel='#status.304' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
78  <!ENTITY status-401                 "<xref target='Part7' x:rel='#status.401' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
79  <!ENTITY status-407                 "<xref target='Part7' x:rel='#status.407' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
80  <!ENTITY status-412                 "<xref target='Part4' x:rel='#status.412' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
81  <!ENTITY status-416                 "<xref target='Part5' x:rel='#status.416' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
82  <!ENTITY p3-header-fields           "<xref target='Part3' x:rel='#header.field.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
83  <!ENTITY p4-status-codes            "<xref target='Part4' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
84  <!ENTITY p5-status-codes            "<xref target='Part5' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
85  <!ENTITY p7-status-codes            "<xref target='Part7' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
86  <!ENTITY p6-heuristic               "<xref target='Part6' x:rel='#heuristic.freshness' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
87  <!ENTITY p6-explicit                "<xref target='Part6' x:rel='#calculating.freshness.lifetime' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
88  <!ENTITY p6-invalid                 "<xref target='Part6' x:rel='#invalidation.after.updates.or.deletions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
89]>
90<?rfc toc="yes" ?>
91<?rfc symrefs="yes" ?>
92<?rfc sortrefs="yes" ?>
93<?rfc compact="yes"?>
94<?rfc subcompact="no" ?>
95<?rfc linkmailto="no" ?>
96<?rfc editing="no" ?>
97<?rfc comments="yes"?>
98<?rfc inline="yes"?>
99<?rfc rfcedstyle="yes"?>
100<?rfc-ext allow-markup-in-artwork="yes" ?>
101<?rfc-ext include-references-in-index="yes" ?>
102<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="proposed"
103     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
104     xmlns:x='http://purl.org/net/xml2rfc/ext'
105     xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
106<x:link rel="prev" basename="p1-messaging"/>
107<x:link rel="next" basename="p3-payload"/>
108<front>
109
110  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
111
112  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
113    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
114    <address>
115      <postal>
116        <street>345 Park Ave</street>
117        <city>San Jose</city>
118        <region>CA</region>
119        <code>95110</code>
120        <country>USA</country>
121      </postal>
122      <email>fielding@gbiv.com</email>
123      <uri>http://roy.gbiv.com/</uri>
124    </address>
125  </author>
126
127  <author initials="J." surname="Gettys" fullname="Jim Gettys">
128    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
129    <address>
130      <postal>
131        <street>21 Oak Knoll Road</street>
132        <city>Carlisle</city>
133        <region>MA</region>
134        <code>01741</code>
135        <country>USA</country>
136      </postal>
137      <email>jg@freedesktop.org</email>
138      <uri>http://gettys.wordpress.com/</uri>
139    </address>
140  </author>
141 
142  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
143    <organization abbrev="HP">Hewlett-Packard Company</organization>
144    <address>
145      <postal>
146        <street>HP Labs, Large Scale Systems Group</street>
147        <street>1501 Page Mill Road, MS 1177</street>
148        <city>Palo Alto</city>
149        <region>CA</region>
150        <code>94304</code>
151        <country>USA</country>
152      </postal>
153      <email>JeffMogul@acm.org</email>
154    </address>
155  </author>
156
157  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
158    <organization abbrev="Microsoft">Microsoft Corporation</organization>
159    <address>
160      <postal>
161        <street>1 Microsoft Way</street>
162        <city>Redmond</city>
163        <region>WA</region>
164        <code>98052</code>
165        <country>USA</country>
166      </postal>
167      <email>henrikn@microsoft.com</email>
168    </address>
169  </author>
170
171  <author initials="L." surname="Masinter" fullname="Larry Masinter">
172    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
173    <address>
174      <postal>
175        <street>345 Park Ave</street>
176        <city>San Jose</city>
177        <region>CA</region>
178        <code>95110</code>
179        <country>USA</country>
180      </postal>
181      <email>LMM@acm.org</email>
182      <uri>http://larry.masinter.net/</uri>
183    </address>
184  </author>
185 
186  <author initials="P." surname="Leach" fullname="Paul J. Leach">
187    <organization abbrev="Microsoft">Microsoft Corporation</organization>
188    <address>
189      <postal>
190        <street>1 Microsoft Way</street>
191        <city>Redmond</city>
192        <region>WA</region>
193        <code>98052</code>
194      </postal>
195      <email>paulle@microsoft.com</email>
196    </address>
197  </author>
198   
199  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
200    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
201    <address>
202      <postal>
203        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
204        <street>The Stata Center, Building 32</street>
205        <street>32 Vassar Street</street>
206        <city>Cambridge</city>
207        <region>MA</region>
208        <code>02139</code>
209        <country>USA</country>
210      </postal>
211      <email>timbl@w3.org</email>
212      <uri>http://www.w3.org/People/Berners-Lee/</uri>
213    </address>
214  </author>
215
216  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
217    <organization abbrev="W3C">World Wide Web Consortium</organization>
218    <address>
219      <postal>
220        <street>W3C / ERCIM</street>
221        <street>2004, rte des Lucioles</street>
222        <city>Sophia-Antipolis</city>
223        <region>AM</region>
224        <code>06902</code>
225        <country>France</country>
226      </postal>
227      <email>ylafon@w3.org</email>
228      <uri>http://www.raubacapeu.net/people/yves/</uri>
229    </address>
230  </author>
231
232  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
233    <organization abbrev="greenbytes">greenbytes GmbH</organization>
234    <address>
235      <postal>
236        <street>Hafenweg 16</street>
237        <city>Muenster</city><region>NW</region><code>48155</code>
238        <country>Germany</country>
239      </postal>
240      <phone>+49 251 2807760</phone>
241      <facsimile>+49 251 2807761</facsimile>
242      <email>julian.reschke@greenbytes.de</email>
243      <uri>http://greenbytes.de/tech/webdav/</uri>
244    </address>
245  </author>
246
247  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
248  <workgroup>HTTPbis Working Group</workgroup>
249
250<abstract>
251<t>
252   The Hypertext Transfer Protocol (HTTP) is an application-level protocol for
253   distributed, collaborative, hypertext information systems. HTTP has been in
254   use by the World Wide Web global information initiative since 1990. This
255   document is Part 2 of the seven-part specification that defines the protocol
256   referred to as "HTTP/1.1" and, taken together, obsoletes RFC 2616.
257</t>
258<t>
259   Part 2 defines the semantics of HTTP messages as expressed by request
260   methods, request header fields, response status codes, and response header
261   fields.
262</t>
263</abstract>
264
265<note title="Editorial Note (To be removed by RFC Editor)">
266  <t>
267    Discussion of this draft should take place on the HTTPBIS working group
268    mailing list (ietf-http-wg@w3.org), which is archived at
269    <eref target="http://lists.w3.org/Archives/Public/ietf-http-wg/"/>.
270  </t>
271  <t>
272    The current issues list is at
273    <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/> and related
274    documents (including fancy diffs) can be found at
275    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
276  </t>
277  <t>
278    The changes in this draft are summarized in <xref target="changes.since.18"/>.
279  </t>
280</note>
281</front>
282<middle>
283<section title="Introduction" anchor="introduction">
284<t>
285   This document defines HTTP/1.1 request and response semantics.  Each HTTP
286   message, as defined in &messaging;, is in the form of either a request or
287   a response.  An HTTP server listens on a connection for HTTP requests and
288   responds to each request, in the order received on that connection, with
289   one or more HTTP response messages.  This document defines the commonly
290   agreed upon semantics of the HTTP uniform interface, the intentions defined
291   by each request method, and the various response messages that might be
292   expected as a result of applying that method to the target resource.
293</t>
294<t>
295   This document is currently disorganized in order to minimize the changes
296   between drafts and enable reviewers to see the smaller errata changes.
297   A future draft will reorganize the sections to better reflect the content.
298   In particular, the sections will be ordered according to the typical
299   processing of an HTTP request message (after message parsing): resource
300   mapping, methods, request modifying header fields, response status,
301   status modifying header fields, and resource metadata.  The current mess
302   reflects how widely dispersed these topics and associated requirements
303   had become in <xref target="RFC2616"/>.
304</t>
305
306<section title="Conformance and Error Handling" anchor="intro.conformance.and.error.handling">
307<t>
308   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
309   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
310   document are to be interpreted as described in <xref target="RFC2119"/>.
311</t>
312<t>
313   This document defines conformance criteria for several roles in HTTP
314   communication, including Senders, Recipients, Clients, Servers, User-Agents,
315   Origin Servers, Intermediaries, Proxies and Gateways. See &architecture;
316   for definitions of these terms.
317</t>
318<t>
319   An implementation is considered conformant if it complies with all of the
320   requirements associated with its role(s). Note that SHOULD-level requirements
321   are relevant here, unless one of the documented exceptions is applicable.
322</t>
323<t>
324   This document also uses ABNF to define valid protocol elements
325   (<xref target="notation"/>). In addition to the prose requirements placed
326   upon them, Senders &MUST-NOT; generate protocol elements that are invalid.
327</t>
328<t>
329   Unless noted otherwise, Recipients &MAY; take steps to recover a usable
330   protocol element from an invalid construct. However, HTTP does not define
331   specific error handling mechanisms, except in cases where it has direct
332   impact on security. This is because different uses of the protocol require
333   different error handling strategies; for example, a Web browser may wish to
334   transparently recover from a response where the Location header field
335   doesn't parse according to the ABNF, whereby in a systems control protocol
336   using HTTP, this type of error recovery could lead to dangerous consequences.
337</t>
338</section>
339
340<section title="Syntax Notation" anchor="notation">
341  <x:anchor-alias value="CR"/>
342  <x:anchor-alias value="DIGIT"/>
343  <x:anchor-alias value="LF"/>
344  <x:anchor-alias value="HTAB"/>
345  <x:anchor-alias value="VCHAR"/>
346  <x:anchor-alias value="SP"/>
347<t>
348  This specification uses the ABNF syntax defined in &notation; (which
349  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
350  <xref target="collected.abnf"/> shows the collected ABNF, with the list
351  rule expanded.
352</t>
353<t>
354  The following core rules are included by
355  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
356  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
357  DIGIT (decimal 0-9), DQUOTE (double quote),
358  HEXDIG (hexadecimal 0-9/A-F/a-f), HTAB (horizontal tab), LF (line feed),
359  OCTET (any 8-bit sequence of data), SP (space), and
360  VCHAR (any visible US-ASCII character).
361</t>
362
363<section title="Core Rules" anchor="core.rules">
364  <x:anchor-alias value="obs-text"/>
365  <x:anchor-alias value="quoted-string"/>
366  <x:anchor-alias value="token"/>
367  <x:anchor-alias value="BWS"/>
368  <x:anchor-alias value="OWS"/>
369  <x:anchor-alias value="RWS"/>
370<t>
371  The core rules below are defined in <xref target="Part1"/>:
372</t>
373<figure><artwork type="abnf2616">
374  <x:ref>BWS</x:ref>           = &lt;BWS, defined in &basic-rules;&gt;
375  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
376  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
377  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
378  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &field-rules;&gt;
379  <x:ref>token</x:ref>         = &lt;token, defined in &field-rules;&gt;
380</artwork></figure>
381</section>
382
383<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
384  <x:anchor-alias value="absolute-URI"/>
385  <x:anchor-alias value="comment"/>
386  <x:anchor-alias value="partial-URI"/>
387  <x:anchor-alias value="product"/>
388  <x:anchor-alias value="URI-reference"/>
389<t>
390  The ABNF rules below are defined in other parts:
391</t>
392<figure><!--Part1--><artwork type="abnf2616">
393  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
394  <x:ref>comment</x:ref>       = &lt;comment, defined in &field-rules;&gt;
395  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
396  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
397  <x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in &uri;&gt;
398</artwork></figure>
399</section>
400</section>
401</section>
402
403<section title="Method" anchor="method">
404  <x:anchor-alias value="Method"/>
405  <x:anchor-alias value="extension-method"/>
406<t>
407   The Method token indicates the request method to be performed on the target
408   resource (&effective-request-uri;). The method is case-sensitive.
409</t>
410<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/>
411  <x:ref>Method</x:ref>         = <x:ref>token</x:ref>
412</artwork></figure>
413<t>
414   The list of methods allowed by a resource can be specified in an
415   Allow header field (<xref target="header.allow"/>). The status code of the response
416   always notifies the client whether a method is currently allowed on a
417   resource, since the set of allowed methods can change dynamically. An
418   origin server &SHOULD; respond with the status code 405 (Method Not Allowed)
419   if the method is known by the origin server but not allowed for the
420   resource, and 501 (Not Implemented) if the method is
421   unrecognized or not implemented by the origin server. The methods GET
422   and HEAD &MUST; be supported by all general-purpose servers. All other
423   methods are &OPTIONAL;; however, if the above methods are implemented,
424   they &MUST; be implemented with the same semantics as those specified
425   in <xref target="method.definitions"/>.
426</t>
427
428<section title="Overview of Methods" anchor="overview.of.methods">
429<t>
430  The methods listed below are defined in <xref target="method.definitions"/>.
431</t>
432<texttable align="left">
433  <ttcol>Method Name</ttcol><ttcol>Defined in...</ttcol>
434 
435  <c>OPTIONS</c> <c><xref target="OPTIONS"/></c>
436  <c>GET</c> <c><xref target="GET"/></c>
437  <c>HEAD</c> <c><xref target="HEAD"/></c>
438  <c>POST</c> <c><xref target="POST"/></c>
439  <c>PUT</c> <c><xref target="PUT"/></c>
440  <c>DELETE</c> <c><xref target="DELETE"/></c>
441  <c>TRACE</c> <c><xref target="TRACE"/></c>
442  <c>CONNECT</c> <c><xref target="CONNECT"/></c>
443</texttable>
444<t>
445  Note that this list is not exhaustive &mdash; it does not include request methods defined
446  in other specifications.
447</t>
448</section>
449
450<section title="Method Registry" anchor="method.registry">
451<t>
452  The HTTP Method Registry defines the name space for the Method token in the
453  Request line of an HTTP request.
454</t>
455<t>
456  Registrations &MUST; include the following fields:
457  <list style="symbols">
458    <t>Method Name (see <xref target="method"/>)</t>
459    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
460    <t>Pointer to specification text</t>
461  </list>
462</t>
463<t>
464  Values to be added to this name space are subject to IETF review
465  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
466</t>
467<t>
468  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
469</t>
470
471<section title="Considerations for New Methods" anchor="considerations.for.new.methods">
472<t>
473   When it is necessary to express new semantics for a HTTP request that
474   aren't specific to a single application or media type, and currently defined
475   methods are inadequate, it may be appropriate to register a new method.
476</t>
477<t>
478   HTTP methods are generic; that is, they are potentially applicable to any
479   resource, not just one particular media type, "type" of resource, or
480   application. As such, it is preferred that new HTTP methods be registered
481   in a document that isn't specific to a single application, so that this is
482   clear.
483</t>
484<t>
485   Due to the parsing rules defined in &message-body;, definitions of HTTP
486   methods cannot prohibit the presence of a message-body on either the request
487   or the response message (with responses to HEAD requests being the single
488   exception). Definitions of new methods cannot change this rule, but they can
489   specify that only zero-length bodies (as opposed to absent bodies) are allowed.
490</t>
491<t>
492   New method definitions need to indicate whether they are safe (<xref
493   target="safe.methods"/>), what semantics (if any) the request body has,
494   and whether they are idempotent (<xref target="idempotent.methods"/>).
495   They also need to state whether they can be cached (&caching;); in
496   particular what conditions a cache may store the response, and under what
497   conditions such a stored response may be used to satisfy a subsequent
498   request.
499</t>
500</section>
501
502</section>
503</section>
504
505<section title="Header Fields" anchor="header.fields">
506<t>
507   Header fields are key value pairs that can be used to communicate data about
508   the message, its payload, the target resource, or about the connection
509   itself (i.e., control data).  See &header-fields; for a general definition
510   of their syntax.
511</t>
512
513<section title="Considerations for Creating Header Fields" anchor="considerations.for.creating.header.fields">
514<t>
515   New header fields are registered using the procedures described in
516   <xref target="RFC3864"/>.
517</t>
518<t>
519   The requirements for header field names are defined in
520   <xref target="RFC3864" x:fmt="of" x:sec="4.1"/>.  Authors of specifications
521   defining new fields are advised to keep the name as short as practical, and
522   not to prefix them with "X-" if they are to be registered (either
523   immediately or in the future).
524</t>
525<t>
526   New header field values typically have their syntax defined using ABNF
527   (<xref target="RFC5234"/>), using the extensions defined in &notation-abnf;
528   as necessary, and are usually constrained to the range of ASCII characters.
529   Header fields needing a greater range of characters can use an encoding
530   such as the one defined in <xref target="RFC5987"/>.
531</t>
532<t>
533   Because commas (",") are used as a generic delimiter between field-values,
534   they need to be treated with care if they are allowed in the field-value's
535   payload. Typically, components that might contain a comma are protected with
536   double-quotes using the quoted-string ABNF production (&field-rules;).
537</t>
538<t>
539   For example, a textual date and a URI (either of which might contain a comma)
540   could be safely carried in field-values like these:
541</t>
542<figure><artwork type="example">
543  Example-URI-Field: "http://example.com/a.html,foo",
544                     "http://without-a-comma.example.com/"
545  Example-Date-Field: "Sat, 04 May 1996", "Wed, 14 Sep 2005"
546</artwork></figure>
547<t>
548   Note that double quote delimiters almost always are used with the
549   quoted-string production; using a different syntax inside double quotes
550   will likely cause unnecessary confusion.
551</t>
552<t>
553   Many header fields use a format including (case-insensitively) named
554   parameters (for instance, Content-Type, defined in &header-content-type;).
555   Allowing both unquoted (token) and quoted (quoted-string) syntax for the
556   parameter value enables recipients to use existing parser components. When
557   allowing both forms, the meaning of a parameter value ought to be
558   independent of the syntax used for it (for an example, see the notes on
559   parameter handling for media types in &media-types;).
560</t>
561<t>
562   Authors of specifications defining new header fields are advised to consider
563   documenting:
564  <list style="symbols">
565    <x:lt>
566      <t>Whether the field is a single value, or whether it can be a list
567      (delimited by commas; see &header-fields;).</t>
568      <t>If it does not use the list syntax, document how to treat messages
569      where the header field occurs multiple times (a sensible default would
570      be to ignore the header field, but this might not always be the right
571      choice).</t>
572      <t>Note that intermediaries and software libraries might combine
573      multiple header field instances into a single one, despite the header
574      field not allowing this. A robust format enables recipients to discover
575      these situations (good example: "Content-Type", as the comma can only
576      appear inside quoted strings; bad example: "Location", as a comma can
577      occur inside a URI).</t>
578    </x:lt>
579    <x:lt><t>Under what conditions the header field can be used; e.g., only in
580    responses or requests, in all messages, only on responses to a particular
581    request method.</t></x:lt>
582    <x:lt><t>Whether it is appropriate to list the field-name in the Connection header
583    (i.e., if the header is to be hop-by-hop, see &header-connection;).</t></x:lt>
584    <x:lt><t>Under what conditions intermediaries are allowed to modify the header
585    field's value, insert or delete it.</t></x:lt>
586    <x:lt><t>How the header might interact with caching (see <xref target="Part6"/>).</t></x:lt>
587    <x:lt><t>Whether the header field is useful or allowable in trailers (see
588    &chunked-encoding;).</t></x:lt>
589    <x:lt><t>Whether the header field should be preserved across redirects.</t></x:lt>
590  </list>
591</t>
592</section>
593
594<section title="Request Header Fields" anchor="request.header.fields">
595  <x:anchor-alias value="request-header"/>
596<t>
597   The request header fields allow the client to pass additional
598   information about the request, and about the client itself, to the
599   server. These fields act as request modifiers, with semantics
600   equivalent to the parameters on a programming language method
601   invocation.
602</t>
603<texttable align="left">
604  <ttcol>Header Field Name</ttcol>
605  <ttcol>Defined in...</ttcol>
606
607  <c>Accept</c> <c>&header-accept;</c>
608  <c>Accept-Charset</c> <c>&header-accept-charset;</c>
609  <c>Accept-Encoding</c> <c>&header-accept-encoding;</c>
610  <c>Accept-Language</c> <c>&header-accept-language;</c>
611  <c>Authorization</c> <c>&header-authorization;</c>
612  <c>Expect</c> <c><xref target="header.expect"/></c>
613  <c>From</c> <c><xref target="header.from"/></c>
614  <c>Host</c> <c>&header-host;</c>
615  <c>If-Match</c> <c>&header-if-match;</c>
616  <c>If-Modified-Since</c> <c>&header-if-modified-since;</c>
617  <c>If-None-Match</c> <c>&header-if-none-match;</c>
618  <c>If-Range</c> <c>&header-if-range;</c>
619  <c>If-Unmodified-Since</c> <c>&header-if-unmodified-since;</c>
620  <c>Max-Forwards</c> <c><xref target="header.max-forwards"/></c>
621  <c>Proxy-Authorization</c> <c>&header-proxy-authorization;</c>
622  <c>Range</c> <c>&header-range;</c>
623  <c>Referer</c> <c><xref target="header.referer"/></c>
624  <c>TE</c> <c>&header-te;</c>
625  <c>User-Agent</c> <c><xref target="header.user-agent"/></c>
626</texttable>
627</section>
628
629<section title="Response Header Fields" anchor="response.header.fields">
630  <x:anchor-alias value="response-header"/>
631<t>
632   The response header fields allow the server to pass additional
633   information about the response which cannot be placed in the Status-Line.
634   These header fields give information about the server and about
635   further access to the target resource (&effective-request-uri;).
636</t>
637<texttable align="left">
638  <ttcol>Header Field Name</ttcol><ttcol>Defined in...</ttcol>
639
640  <c>Accept-Ranges</c> <c>&header-accept-ranges;</c>
641  <c>Age</c> <c>&header-age;</c>
642  <c>Allow</c> <c><xref target="header.allow"/></c>
643  <c>Date</c> <c><xref target="header.date"/></c>
644  <c>ETag</c> <c>&header-etag;</c>
645  <c>Location</c> <c><xref target="header.location"/></c>
646  <c>Proxy-Authenticate</c> <c>&header-proxy-authenticate;</c>
647  <c>Retry-After</c> <c><xref target="header.retry-after"/></c>
648  <c>Server</c> <c><xref target="header.server"/></c>
649  <c>Vary</c> <c>&header-vary;</c>
650  <c>WWW-Authenticate</c> <c>&header-www-authenticate;</c>
651</texttable>
652</section>
653
654</section>
655
656<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
657  <x:anchor-alias value="Reason-Phrase"/>
658  <x:anchor-alias value="Status-Code"/>
659  <x:anchor-alias value="extension-code"/>
660<t>
661   The Status-Code element is a 3-digit integer result code of the attempt to
662   understand and satisfy the request.
663</t>
664<t>
665   The Reason-Phrase is intended to give a short textual description of the
666   Status-Code and is intended for a human user. The client does not need
667   to examine or display the Reason-Phrase.
668</t>
669<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"/>
670  <x:ref>Status-Code</x:ref>    = 3<x:ref>DIGIT</x:ref>
671  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>HTAB</x:ref> / <x:ref>SP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
672</artwork></figure>
673<t>
674   HTTP status codes are extensible. HTTP applications are not required
675   to understand the meaning of all registered status codes, though such
676   understanding is obviously desirable. However, applications &MUST;
677   understand the class of any status code, as indicated by the first
678   digit, and treat any unrecognized response as being equivalent to the
679   x00 status code of that class, with the exception that an
680   unrecognized response &MUST-NOT; be cached. For example, if an
681   unrecognized status code of 431 is received by the client, it can
682   safely assume that there was something wrong with its request and
683   treat the response as if it had received a 400 status code. In such
684   cases, user agents &SHOULD; present to the user the representation enclosed
685   with the response, since that representation is likely to include human-readable
686   information which will explain the unusual status.
687</t>
688
689<section title="Overview of Status Codes" anchor="overview.of.status.codes">
690<t> 
691   The status codes listed below are defined in <xref target="status.codes"/>
692   of this specification, &p4-status-codes;, &p5-status-codes;, and &p7-status-codes;.
693   The reason phrases listed here are only recommendations &mdash; they can be
694   replaced by local equivalents without affecting the protocol.
695</t>
696<texttable align="left">
697  <ttcol>Status-Code</ttcol>
698  <ttcol>Reason-Phrase</ttcol>
699  <ttcol>Defined in...</ttcol>
700 
701  <c>100</c> <c>Continue</c> <c><xref target="status.100"/></c>
702  <c>101</c> <c>Switching Protocols</c> <c><xref target="status.101"/></c>
703
704  <c>200</c> <c>OK</c> <c><xref target="status.200"/></c>
705  <c>201</c> <c>Created</c> <c><xref target="status.201"/></c>
706  <c>202</c> <c>Accepted</c> <c><xref target="status.202"/></c>
707  <c>203</c> <c>Non-Authoritative Information</c> <c><xref target="status.203"/></c>
708  <c>204</c> <c>No Content</c> <c><xref target="status.204"/></c>
709  <c>205</c> <c>Reset Content</c> <c><xref target="status.205"/></c>
710  <c>206</c> <c>Partial Content</c> <c>&status-206;</c>
711
712  <c>300</c> <c>Multiple Choices</c> <c><xref target="status.300"/></c>
713  <c>301</c> <c>Moved Permanently</c> <c><xref target="status.301"/></c>
714  <c>302</c> <c>Found</c> <c><xref target="status.302"/></c>
715  <c>303</c> <c>See Other</c> <c><xref target="status.303"/></c>
716  <c>304</c> <c>Not Modified</c> <c>&status-304;</c>
717  <c>305</c> <c>Use Proxy</c> <c><xref target="status.305"/></c>
718  <c>307</c> <c>Temporary Redirect</c> <c><xref target="status.307"/></c>
719
720  <c>400</c> <c>Bad Request</c> <c><xref target="status.400"/></c>
721  <c>401</c> <c>Unauthorized</c> <c>&status-401;</c>
722  <c>402</c> <c>Payment Required</c> <c><xref target="status.402"/></c>
723  <c>403</c> <c>Forbidden</c> <c><xref target="status.403"/></c>
724  <c>404</c> <c>Not Found</c> <c><xref target="status.404"/></c>
725  <c>405</c> <c>Method Not Allowed</c> <c><xref target="status.405"/></c>
726  <c>406</c> <c>Not Acceptable</c> <c><xref target="status.406"/></c>
727  <c>407</c> <c>Proxy Authentication Required</c> <c>&status-407;</c>
728  <c>408</c> <c>Request Time-out</c> <c><xref target="status.408"/></c>
729  <c>409</c> <c>Conflict</c> <c><xref target="status.409"/></c>
730  <c>410</c> <c>Gone</c> <c><xref target="status.410"/></c>
731  <c>411</c> <c>Length Required</c> <c><xref target="status.411"/></c>
732  <c>412</c> <c>Precondition Failed</c> <c>&status-412;</c>
733  <c>413</c> <c>Request Representation Too Large</c> <c><xref target="status.413"/></c>
734  <c>414</c> <c>URI Too Long</c> <c><xref target="status.414"/></c>
735  <c>415</c> <c>Unsupported Media Type</c> <c><xref target="status.415"/></c>
736  <c>416</c> <c>Requested range not satisfiable</c> <c>&status-416;</c>
737  <c>417</c> <c>Expectation Failed</c> <c><xref target="status.417"/></c>
738  <c>426</c> <c>Upgrade Required</c> <c><xref target="status.426"/></c>
739
740  <c>500</c> <c>Internal Server Error</c> <c><xref target="status.500"/></c>
741  <c>501</c> <c>Not Implemented</c> <c><xref target="status.501"/></c>
742  <c>502</c> <c>Bad Gateway</c> <c><xref target="status.502"/></c>
743  <c>503</c> <c>Service Unavailable</c> <c><xref target="status.503"/></c>
744  <c>504</c> <c>Gateway Time-out</c> <c><xref target="status.504"/></c>
745  <c>505</c> <c>HTTP Version not supported</c> <c><xref target="status.505"/></c>
746</texttable>
747<t>
748   Note that this list is not exhaustive &mdash; it does not include
749   extension status codes defined in other specifications.
750</t>
751</section>
752
753<section title="Status Code Registry" anchor="status.code.registry">
754<t>
755  The HTTP Status Code Registry defines the name space for the Status-Code
756  token in the Status-Line of an HTTP response.
757</t>
758<t>
759  Values to be added to this name space are subject to IETF review
760  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
761</t>
762<t>
763  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
764</t>
765
766<section title="Considerations for New Status Codes" anchor="considerations.for.new.status.codes">
767<t>
768   When it is necessary to express new semantics for a HTTP response that
769   aren't specific to a single application or media type, and currently defined
770   status codes are inadequate, a new status code can be registered.
771</t>
772<t>
773   HTTP status codes are generic; that is, they are potentially applicable to
774   any resource, not just one particular media type, "type" of resource, or
775   application. As such, it is preferred that new HTTP status codes be
776   registered in a document that isn't specific to a single application, so
777   that this is clear.
778</t>
779<t>
780   Definitions of new HTTP status codes typically explain the request
781   conditions that produce a response containing the status code (e.g.,
782   combinations of request headers and/or method(s)), along with any
783   interactions with response headers (e.g., those that are required, those
784   that modify the semantics of the response).
785</t>
786<t>
787   New HTTP status codes are required to fall under one of the categories
788   defined in <xref target="status.codes"/>. To allow existing parsers to
789   properly handle them, new status codes cannot disallow a response body,
790   although they can mandate a zero-length response body. They can require the
791   presence of one or more particular HTTP response header(s).
792</t>
793<t>
794   Likewise, their definitions can specify that caches are allowed to use
795   heuristics to determine their freshness (see &caching;; by default, it is
796   not allowed), and can define how to determine the resource which they
797   carry a representation for (see <xref
798   target="identifying.response.associated.with.representation"/>; by default,
799   it is anonymous).
800</t>
801</section>
802
803</section>
804
805</section>
806
807<section title="Representation" anchor="representation">
808<t>
809   Request and Response messages &MAY; transfer a representation if not otherwise
810   restricted by the request method or response status code. A representation
811   consists of metadata (representation header fields) and data (representation
812   body).  When a complete or partial representation is enclosed in an HTTP message,
813   it is referred to as the payload of the message. HTTP representations
814   are defined in &payload;.
815</t>
816<t>
817   A representation body is only present in a message when a message-body is
818   present, as described in &message-body;. The representation body is obtained
819   from the message-body by decoding any Transfer-Encoding that might
820   have been applied to ensure safe and proper transfer of the message.
821</t>
822
823<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
824<t>
825   It is sometimes necessary to determine an identifier for the resource
826   associated with a representation.
827</t>
828<t>
829   An HTTP request representation, when present, is always associated with an
830   anonymous (i.e., unidentified) resource.
831</t>
832<t>
833   In the common case, an HTTP response is a representation of the target
834   resource (see &effective-request-uri;). However, this is not always the
835   case. To determine the URI of the resource a response is associated with,
836   the following rules are used (with the first applicable one being selected):
837</t>
838<t><list style="numbers">
839   <t>If the response status code is 200 or 203 and the request method was GET,
840   the response payload is a representation of the target resource.</t>
841   <t>If the response status code is 204, 206, or 304 and the request method was GET
842   or HEAD, the response payload is a partial representation of the target
843   resource.</t>
844   <t>If the response has a Content-Location header field, and that URI is the same
845   as the effective request URI, the response payload is a representation of the
846   target resource.</t>
847   <t>If the response has a Content-Location header field, and that URI is not the
848   same as the effective request URI, then the response asserts that its
849   payload is a representation of the resource identified by the
850   Content-Location URI. However, such an assertion cannot be trusted unless
851   it can be verified by other means (not defined by HTTP).</t>
852   <t>Otherwise, the response is a representation of an anonymous (i.e.,
853   unidentified) resource.</t>
854</list></t>
855<t>
856  <cref anchor="TODO-req-uri">
857   The comparison function is going to have to be defined somewhere,
858   because we already need to compare URIs for things like cache invalidation.</cref>
859</t>
860</section>
861
862</section>
863
864
865<section title="Method Definitions" anchor="method.definitions">
866<t>
867   The set of common request methods for HTTP/1.1 is defined below. Although
868   this set can be expanded, additional methods cannot be assumed to
869   share the same semantics for separately extended clients and servers.
870</t>
871
872<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
873
874<section title="Safe Methods" anchor="safe.methods">
875<iref item="Safe Methods" primary="true"/>
876<t>
877   Implementors need to be aware that the software represents the user in
878   their interactions over the Internet, and need to allow
879   the user to be aware of any actions they take which might have an
880   unexpected significance to themselves or others.
881</t>
882<t>
883   In particular, the convention has been established that the GET, HEAD,
884   OPTIONS, and TRACE request methods &SHOULD-NOT; have the significance
885   of taking an action other than retrieval. These request methods ought
886   to be considered "<x:dfn anchor="safe">safe</x:dfn>".
887   This allows user agents to represent other methods, such as POST, PUT
888   and DELETE, in a special way, so that the user is made aware of the
889   fact that a possibly unsafe action is being requested.
890</t>
891<t>
892   Naturally, it is not possible to ensure that the server does not
893   generate side-effects as a result of performing a GET request; in
894   fact, some dynamic resources consider that a feature. The important
895   distinction here is that the user did not request the side-effects,
896   so therefore cannot be held accountable for them.
897</t>
898</section>
899
900<section title="Idempotent Methods" anchor="idempotent.methods">
901<iref item="Idempotent Methods" primary="true"/>
902<t>
903   Request methods can also have the property of "idempotence" in that,
904   aside from error or expiration issues, the intended effect of multiple
905   identical requests is the same as for a single request.
906   PUT, DELETE, and all safe request methods are idempotent.
907   It is important to note that idempotence refers only to changes
908   requested by the client: a server is free to change its state due
909   to multiple requests for the purpose of tracking those requests,
910   versioning of results, etc.
911</t>
912</section>
913</section>
914
915<section title="OPTIONS" anchor="OPTIONS">
916  <rdf:Description>
917    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
918  </rdf:Description>
919  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
920  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
921<t>
922   The OPTIONS method requests information about the
923   communication options available on the request/response chain
924   identified by the effective request URI. This method allows a client to
925   determine the options and/or requirements associated with a resource,
926   or the capabilities of a server, without implying a resource action
927   or initiating a resource retrieval.
928</t>
929<t>
930   Responses to the OPTIONS method are not cacheable.
931</t>
932<t>
933   If the OPTIONS request includes a message-body (as indicated by the
934   presence of Content-Length or Transfer-Encoding), then the media type
935   &MUST; be indicated by a Content-Type field. Although this
936   specification does not define any use for such a body, future
937   extensions to HTTP might use the OPTIONS body to make more detailed
938   queries on the server.
939</t>
940<t>
941   If the request-target is an asterisk ("*"), the OPTIONS request is
942   intended to apply to the server in general rather than to a specific
943   resource. Since a server's communication options typically depend on
944   the resource, the "*" request is only useful as a "ping" or "no-op"
945   type of method; it does nothing beyond allowing the client to test
946   the capabilities of the server. For example, this can be used to test
947   a proxy for HTTP/1.1 compliance (or lack thereof).
948</t>
949<t>
950   If the request-target is not an asterisk, the OPTIONS request applies
951   only to the options that are available when communicating with that
952   resource.
953</t>
954<t>
955   A 200 response &SHOULD; include any header fields that indicate
956   optional features implemented by the server and applicable to that
957   resource (e.g., Allow), possibly including extensions not defined by
958   this specification. The response body, if any, &SHOULD; also include
959   information about the communication options. The format for such a
960   body is not defined by this specification, but might be defined by
961   future extensions to HTTP. Content negotiation &MAY; be used to select
962   the appropriate response format. If no response body is included, the
963   response &MUST; include a Content-Length field with a field-value of
964   "0".
965</t>
966<t>
967   The Max-Forwards header field &MAY; be used to target a
968   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
969   If no Max-Forwards field is present in the request, then the forwarded
970   request &MUST-NOT; include a Max-Forwards field.
971</t>
972</section>
973
974<section title="GET" anchor="GET">
975  <rdf:Description>
976    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
977  </rdf:Description>
978  <iref primary="true" item="GET method" x:for-anchor=""/>
979  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
980<t>
981   The GET method requests transfer of a current representation of
982   the target resource.
983</t>
984<t>   
985   If the target resource is a data-producing process, it is the
986   produced data which shall be returned as the representation in the response and not
987   the source text of the process, unless that text happens to be the output of
988   the process.
989</t>
990<t>
991   The semantics of the GET method change to a "conditional GET" if the
992   request message includes an If-Modified-Since, If-Unmodified-Since,
993   If-Match, If-None-Match, or If-Range header field. A conditional GET
994   requests that the representation be transferred only under the
995   circumstances described by the conditional header field(s). The
996   conditional GET request is intended to reduce unnecessary network
997   usage by allowing cached representations to be refreshed without requiring
998   multiple requests or transferring data already held by the client.
999</t>
1000<t>
1001   The semantics of the GET method change to a "partial GET" if the
1002   request message includes a Range header field. A partial GET requests
1003   that only part of the representation be transferred, as described in &header-range;.
1004   The partial GET request is intended to reduce unnecessary
1005   network usage by allowing partially-retrieved representations to be
1006   completed without transferring data already held by the client.
1007</t>
1008<t>
1009   Bodies on GET requests have no defined semantics. Note that sending a body
1010   on a GET request might cause some existing implementations to reject the
1011   request.
1012</t>
1013<t>
1014   The response to a GET request is cacheable and &MAY; be used to satisfy
1015   subsequent GET and HEAD requests (see &caching;).
1016</t>
1017<t>
1018   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
1019</t>
1020</section>
1021
1022<section title="HEAD" anchor="HEAD">
1023  <rdf:Description>
1024    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1025  </rdf:Description>
1026  <iref primary="true" item="HEAD method" x:for-anchor=""/>
1027  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
1028<t>
1029   The HEAD method is identical to GET except that the server &MUST-NOT;
1030   return a message-body in the response. The metadata contained
1031   in the HTTP header fields in response to a HEAD request &SHOULD; be identical
1032   to the information sent in response to a GET request. This method can
1033   be used for obtaining metadata about the representation implied by the
1034   request without transferring the representation body. This method is
1035   often used for testing hypertext links for validity, accessibility,
1036   and recent modification.
1037</t>
1038<t>
1039   The response to a HEAD request is cacheable and &MAY; be used to satisfy
1040   a subsequent HEAD request; see &caching;. It also &MAY; be used to update a previously cached
1041   representation from that resource; if the new field values
1042   indicate that the cached representation differs from the current representation (as
1043   would be indicated by a change in Content-Length, ETag
1044   or Last-Modified), then the cache &MUST; treat the cache entry as
1045   stale.
1046</t>
1047<t>
1048   Bodies on HEAD requests have no defined semantics. Note that sending a body
1049   on a HEAD request might cause some existing implementations to reject the
1050   request.
1051</t>
1052</section>
1053
1054<section title="POST" anchor="POST">
1055  <iref primary="true" item="POST method" x:for-anchor=""/>
1056  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
1057<t>
1058   The POST method requests that the origin server accept the
1059   representation enclosed in the request as data to be processed by the
1060   target resource. POST is designed to allow a uniform method to cover the
1061   following functions:
1062  <list style="symbols">
1063    <t>
1064      Annotation of existing resources;
1065    </t>
1066    <t>
1067        Posting a message to a bulletin board, newsgroup, mailing list,
1068        or similar group of articles;
1069    </t>
1070    <t>
1071        Providing a block of data, such as the result of submitting a
1072        form, to a data-handling process;
1073    </t>
1074    <t>
1075        Extending a database through an append operation.
1076    </t>
1077  </list>
1078</t>
1079<t>
1080   The actual function performed by the POST method is determined by the
1081   server and is usually dependent on the effective request URI.
1082</t>
1083<t>
1084   The action performed by the POST method might not result in a
1085   resource that can be identified by a URI. In this case, either 200
1086   (OK) or 204 (No Content) is the appropriate response status code,
1087   depending on whether or not the response includes a representation that
1088   describes the result.
1089</t>
1090<t>
1091   If a resource has been created on the origin server, the response
1092   &SHOULD; be 201 (Created) and contain a representation which describes the
1093   status of the request and refers to the new resource, and a Location
1094   header field (see <xref target="header.location"/>).
1095</t>
1096<t>
1097   Responses to POST requests are only cacheable when they
1098   include explicit freshness information (see &p6-explicit;). A
1099   cached POST response with a Content-Location header field
1100   (see &header-content-location;) whose value is the effective
1101   Request URI &MAY; be used to satisfy subsequent GET and HEAD requests.
1102</t>
1103<t>
1104   Note that POST caching is not widely implemented.
1105   However, the 303 (See Other) response can be used to direct the
1106   user agent to retrieve a cacheable resource.
1107</t>
1108</section>
1109
1110<section title="PUT" anchor="PUT">
1111  <iref primary="true" item="PUT method" x:for-anchor=""/>
1112  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
1113<t>
1114   The PUT method requests that the state of the target resource
1115   be created or replaced with the state defined by the representation
1116   enclosed in the request message payload.  A successful PUT of a given
1117   representation would suggest that a subsequent GET on that same target
1118   resource will result in an equivalent representation being returned in
1119   a 200 (OK) response.  However, there is no guarantee that such a state
1120   change will be observable, since the target resource might be acted
1121   upon by other user agents in parallel, or might be subject to dynamic
1122   processing by the origin server, before any subsequent GET is received.
1123   A successful response only implies that the user agent's intent was
1124   achieved at the time of its processing by the origin server.
1125</t>
1126<t>   
1127   If the target resource does not have a current representation and
1128   the PUT successfully creates one, then the origin server &MUST; inform
1129   the user agent by sending a 201 (Created) response.  If the target
1130   resource does have a current representation and that representation is
1131   successfully modified in accordance with the state of the enclosed
1132   representation, then either a 200 (OK) or 204 (No Content) response
1133   &SHOULD; be sent to indicate successful completion of the request.
1134</t>
1135<t>
1136   Unrecognized header fields &SHOULD; be ignored (i.e., not saved
1137   as part of the resource state).
1138</t>
1139<t>
1140   An origin server &SHOULD; verify that the PUT representation is
1141   consistent with any constraints which the server has for the target
1142   resource that cannot or will not be changed by the PUT.  This is
1143   particularly important when the origin server uses internal
1144   configuration information related to the URI in order to set the
1145   values for representation metadata on GET responses.  When a PUT
1146   representation is inconsistent with the target resource, the origin
1147   server &SHOULD; either make them consistent, by transforming the
1148   representation or changing the resource configuration, or respond
1149   with an appropriate error message containing sufficient information
1150   to explain why the representation is unsuitable.  The 409 (Conflict)
1151   or 415 (Unsupported Media Type) status codes are suggested, with the
1152   latter being specific to constraints on Content-Type values.
1153</t>
1154<t>
1155   For example, if the target resource is configured to always have a
1156   Content-Type of "text/html" and the representation being PUT has a
1157   Content-Type of "image/jpeg", then the origin server &SHOULD; do one of:
1158   (a) reconfigure the target resource to reflect the new media type;
1159   (b) transform the PUT representation to a format consistent with that
1160   of the resource before saving it as the new resource state; or,
1161   (c) reject the request with a 415 response indicating that the target
1162   resource is limited to "text/html", perhaps including a link to a
1163   different resource that would be a suitable target for the new
1164   representation.
1165</t>
1166<t>
1167   HTTP does not define exactly how a PUT method affects the state
1168   of an origin server beyond what can be expressed by the intent of
1169   the user agent request and the semantics of the origin server response.
1170   It does not define what a resource might be, in any sense of that
1171   word, beyond the interface provided via HTTP.  It does not define
1172   how resource state is "stored", nor how such storage might change
1173   as a result of a change in resource state, nor how the origin server
1174   translates resource state into representations.  Generally speaking,
1175   all implementation details behind the resource interface are
1176   intentionally hidden by the server.
1177</t>
1178<t>
1179   The fundamental difference between the POST and PUT methods is
1180   highlighted by the different intent for the target resource.
1181   The target resource in a POST request is intended to handle the
1182   enclosed representation as a data-accepting process, such as for
1183   a gateway to some other protocol or a document that accepts annotations.
1184   In contrast, the target resource in a PUT request is intended to
1185   take the enclosed representation as a new or replacement value.
1186   Hence, the intent of PUT is idempotent and visible to intermediaries,
1187   even though the exact effect is only known by the origin server.
1188</t>
1189<t>
1190   Proper interpretation of a PUT request presumes that the user agent
1191   knows what target resource is desired.  A service that is intended
1192   to select a proper URI on behalf of the client, after receiving
1193   a state-changing request, &SHOULD; be implemented using the POST
1194   method rather than PUT.  If the origin server will not make the
1195   requested PUT state change to the target resource and instead
1196   wishes to have it applied to a different resource, such as when the
1197   resource has been moved to a different URI, then the origin server
1198   &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
1199   then make its own decision regarding whether or not to redirect the
1200   request.
1201</t>
1202<t>
1203   A PUT request applied to the target resource &MAY; have side-effects
1204   on other resources.  For example, an article might have a URI for
1205   identifying "the current version" (a resource) which is separate
1206   from the URIs identifying each particular version (different
1207   resources that at one point shared the same state as the current version
1208   resource).  A successful PUT request on "the current version" URI might
1209   therefore create a new version resource in addition to changing the
1210   state of the target resource, and might also cause links to be added
1211   between the related resources.
1212</t>
1213<t>
1214   An origin server &SHOULD; reject any PUT request that contains a
1215   Content-Range header field, since it might be misinterpreted as
1216   partial content (or might be partial content that is being mistakenly
1217   PUT as a full representation).  Partial content updates are
1218   possible by targeting a separately identified resource with state
1219   that overlaps a portion of the larger resource, or by using a
1220   different method that has been specifically defined for partial
1221   updates (for example, the PATCH method defined in
1222   <xref target="RFC5789"/>).
1223</t>
1224<t>
1225   Responses to the PUT method are not cacheable. If a PUT request passes
1226   through a cache that has one or more stored responses for the effective
1227   request URI, those stored responses will be invalidated (see
1228   &p6-invalid;).
1229</t>
1230</section>
1231
1232<section title="DELETE" anchor="DELETE">
1233  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1234  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1235<t>
1236   The DELETE method requests that the origin server delete the target
1237   resource. This method &MAY; be overridden by
1238   human intervention (or other means) on the origin server. The client cannot
1239   be guaranteed that the operation has been carried out, even if the
1240   status code returned from the origin server indicates that the action
1241   has been completed successfully. However, the server &SHOULD-NOT; 
1242   indicate success unless, at the time the response is given, it
1243   intends to delete the resource or move it to an inaccessible
1244   location.
1245</t>
1246<t>
1247   A successful response &SHOULD; be 200 (OK) if the response includes an
1248   representation describing the status, 202 (Accepted) if the action has not
1249   yet been enacted, or 204 (No Content) if the action has been enacted
1250   but the response does not include a representation.
1251</t>
1252<t>
1253   Bodies on DELETE requests have no defined semantics. Note that sending a body
1254   on a DELETE request might cause some existing implementations to reject the
1255   request.
1256</t>
1257<t>
1258   Responses to the DELETE method are not cacheable. If a DELETE request
1259   passes through a cache that has one or more stored responses for the
1260   effective request URI, those stored responses will be invalidated (see
1261   &p6-invalid;).
1262</t>
1263</section>
1264
1265<section title="TRACE" anchor="TRACE">
1266  <rdf:Description>
1267    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1268  </rdf:Description>
1269  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1270  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1271<t>
1272   The TRACE method requests a remote, application-layer loop-back
1273   of the request message. The final recipient of the request
1274   &SHOULD; reflect the message received back to the client as the
1275   message-body of a 200 (OK) response. The final recipient is either the
1276   origin server or the first proxy to receive a Max-Forwards
1277   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1278   A TRACE request &MUST-NOT; include a message-body.
1279</t>
1280<t>
1281   TRACE allows the client to see what is being received at the other
1282   end of the request chain and use that data for testing or diagnostic
1283   information. The value of the Via header field (&header-via;) is of
1284   particular interest, since it acts as a trace of the request chain.
1285   Use of the Max-Forwards header field allows the client to limit the
1286   length of the request chain, which is useful for testing a chain of
1287   proxies forwarding messages in an infinite loop.
1288</t>
1289<t>
1290   If the request is valid, the response &SHOULD; have a Content-Type of
1291   "message/http" (see &media-type-message-http;) and contain a message-body
1292   that encloses a copy of the entire request message.
1293   Responses to the TRACE method are not cacheable.
1294</t>
1295</section>
1296
1297<section title="CONNECT" anchor="CONNECT">
1298  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1299  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1300<t>
1301   The CONNECT method requests that the proxy establish a tunnel
1302   to the request-target and then restrict its behavior to blind
1303   forwarding of packets until the connection is closed.
1304</t>
1305<t>
1306   When using CONNECT, the request-target &MUST; use the authority form
1307   (&request-target;); i.e., the request-target consists of only the
1308   host name and port number of the tunnel destination, separated by a colon.
1309   For example,
1310</t>
1311<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1312CONNECT server.example.com:80 HTTP/1.1
1313Host: server.example.com:80
1314
1315</artwork></figure>
1316<t>
1317   Other HTTP mechanisms can be used normally with the CONNECT method &mdash;
1318   except end-to-end protocol Upgrade requests, since the
1319   tunnel must be established first.
1320</t>
1321<t>
1322   For example, proxy authentication might be used to establish the
1323   authority to create a tunnel:
1324</t>
1325<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1326CONNECT server.example.com:80 HTTP/1.1
1327Host: server.example.com:80
1328Proxy-Authorization: basic aGVsbG86d29ybGQ=
1329
1330</artwork></figure>
1331<t>
1332   Bodies on CONNECT requests have no defined semantics. Note that sending a body
1333   on a CONNECT request might cause some existing implementations to reject the
1334   request.
1335</t>
1336<t>
1337   Like any other pipelined HTTP/1.1 request, data to be tunnel may be
1338   sent immediately after the blank line. The usual caveats also apply:
1339   data may be discarded if the eventual response is negative, and the
1340   connection may be reset with no response if more than one TCP segment
1341   is outstanding.
1342</t>
1343
1344<section title="Establishing a Tunnel with CONNECT">
1345<t>
1346   Any successful (2xx) response to a CONNECT request indicates that the
1347   proxy has established a connection to the requested host and port,
1348   and has switched to tunneling the current connection to that server
1349   connection.
1350</t>
1351<t>
1352   It may be the case that the proxy itself can only reach the requested
1353   origin server through another proxy.  In this case, the first proxy
1354   &SHOULD; make a CONNECT request of that next proxy, requesting a tunnel
1355   to the authority.  A proxy &MUST-NOT; respond with any 2xx status code
1356   unless it has either a direct or tunnel connection established to the
1357   authority.
1358</t>
1359<t>
1360   An origin server which receives a CONNECT request for itself &MAY;
1361   respond with a 2xx status code to indicate that a connection is
1362   established.
1363</t>
1364<t>
1365   If at any point either one of the peers gets disconnected, any
1366   outstanding data that came from that peer will be passed to the other
1367   one, and after that also the other connection will be terminated by
1368   the proxy. If there is outstanding data to that peer undelivered,
1369   that data will be discarded.
1370</t>
1371
1372</section>
1373</section>
1374</section>
1375
1376
1377<section title="Status Code Definitions" anchor="status.codes">
1378<t>
1379   The first digit of the Status-Code defines the class of response. The
1380   last two digits do not have any categorization role. There are 5
1381   values for the first digit:
1382  <list style="symbols">
1383    <t>
1384      1xx: Informational - Request received, continuing process
1385    </t>
1386    <t>
1387      2xx: Success - The action was successfully received,
1388        understood, and accepted
1389    </t>
1390    <t>
1391      3xx: Redirection - Further action must be taken in order to
1392        complete the request
1393    </t>
1394    <t>
1395      4xx: Client Error - The request contains bad syntax or cannot
1396        be fulfilled
1397    </t>
1398    <t>
1399      5xx: Server Error - The server failed to fulfill an apparently
1400        valid request
1401    </t>
1402  </list>
1403</t>
1404<t>
1405   Each Status-Code is described below, including any metadata required
1406   in the response.
1407</t>
1408<t>
1409   For most status codes the response can carry a payload, in which case a
1410   Content-Type header field indicates the payload's media type
1411   (&header-content-type;).
1412</t>
1413
1414<section title="Informational 1xx" anchor="status.1xx">
1415<t>
1416   This class of status code indicates a provisional response,
1417   consisting only of the Status-Line and optional header fields, and is
1418   terminated by an empty line. There are no required header fields for this
1419   class of status code. Since HTTP/1.0 did not define any 1xx status
1420   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1421   except under experimental conditions.
1422</t>
1423<t>
1424   A client &MUST; be prepared to accept one or more 1xx status responses
1425   prior to a regular response, even if the client does not expect a 100
1426   (Continue) status message. Unexpected 1xx status responses &MAY; be
1427   ignored by a user agent.
1428</t>
1429<t>
1430   Proxies &MUST; forward 1xx responses, unless the connection between the
1431   proxy and its client has been closed, or unless the proxy itself
1432   requested the generation of the 1xx response. (For example, if a
1433   proxy adds a "Expect: 100-continue" field when it forwards a request,
1434   then it need not forward the corresponding 100 (Continue)
1435   response(s).)
1436</t>
1437
1438<section title="100 Continue" anchor="status.100">
1439  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1440  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1441<t>
1442   The client &SHOULD; continue with its request. This interim response is
1443   used to inform the client that the initial part of the request has
1444   been received and has not yet been rejected by the server. The client
1445   &SHOULD; continue by sending the remainder of the request or, if the
1446   request has already been completed, ignore this response. The server
1447   &MUST; send a final response after the request has been completed. See
1448   &use100; for detailed discussion of the use and handling of this
1449   status code.
1450</t>
1451</section>
1452
1453<section title="101 Switching Protocols" anchor="status.101">
1454  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1455  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1456<t>
1457   The server understands and is willing to comply with the client's
1458   request, via the Upgrade message header field (&header-upgrade;), for a
1459   change in the application protocol being used on this connection. The
1460   server will switch protocols to those defined by the response's
1461   Upgrade header field immediately after the empty line which
1462   terminates the 101 response.
1463</t>
1464<t>
1465   The protocol &SHOULD; be switched only when it is advantageous to do
1466   so. For example, switching to a newer version of HTTP is advantageous
1467   over older versions, and switching to a real-time, synchronous
1468   protocol might be advantageous when delivering resources that use
1469   such features.
1470</t>
1471</section>
1472</section>
1473
1474<section title="Successful 2xx" anchor="status.2xx">
1475<t>
1476   This class of status code indicates that the client's request was
1477   successfully received, understood, and accepted.
1478</t>
1479
1480<section title="200 OK" anchor="status.200">
1481  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1482  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1483<t>
1484   The request has succeeded. The payload returned with the response
1485   is dependent on the method used in the request, for example:
1486  <list style="hanging">
1487    <t hangText="GET">
1488      a representation of the target resource is sent in the response;
1489    </t>
1490    <t hangText="HEAD">
1491      the same representation as GET, except without the message-body;
1492    </t>
1493    <t hangText="POST">
1494      a representation describing or containing the result of the action;
1495    </t>
1496    <t hangText="TRACE">
1497      a representation containing the request message as received by the
1498      end server.
1499    </t>
1500  </list>
1501</t>
1502<t>
1503   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1504   freshness for 200 responses.
1505</t>
1506</section>
1507
1508<section title="201 Created" anchor="status.201">
1509  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1510  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1511<t>
1512   The request has been fulfilled and has resulted in a new resource being
1513   created. The newly created resource can be referenced by the URI(s)
1514   returned in the payload of the response, with the most specific URI
1515   for the resource given by a Location header field. The response
1516   &SHOULD; include a payload containing a list of resource
1517   characteristics and location(s) from which the user or user agent can
1518   choose the one most appropriate.
1519</t>
1520<t>
1521   The origin server &MUST; create the resource before returning the 201 status
1522   code. If the action cannot be carried out immediately, the server &SHOULD;
1523   respond with 202 (Accepted) response instead.
1524</t>
1525<t>
1526   A 201 response &MAY; contain an ETag response header field indicating
1527   the current value of the entity-tag for the representation of the resource
1528   just created (see &header-etag;).
1529</t>
1530</section>
1531
1532<section title="202 Accepted" anchor="status.202">
1533  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1534  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1535<t>
1536   The request has been accepted for processing, but the processing has
1537   not been completed.  The request might or might not eventually be
1538   acted upon, as it might be disallowed when processing actually takes
1539   place. There is no facility for re-sending a status code from an
1540   asynchronous operation such as this.
1541</t>
1542<t>
1543   The 202 response is intentionally non-committal. Its purpose is to
1544   allow a server to accept a request for some other process (perhaps a
1545   batch-oriented process that is only run once per day) without
1546   requiring that the user agent's connection to the server persist
1547   until the process is completed. The representation returned with this
1548   response &SHOULD; include an indication of the request's current status
1549   and either a pointer to a status monitor or some estimate of when the
1550   user can expect the request to be fulfilled.
1551</t>
1552</section>
1553
1554<section title="203 Non-Authoritative Information" anchor="status.203">
1555  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1556  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1557<t>
1558   The representation in the response has been transformed or otherwise
1559   modified by a transforming proxy (&intermediaries;).  Note that the
1560   behavior of transforming intermediaries is controlled by the no-transform
1561   Cache-Control directive (&header-cache-control;).
1562</t>
1563<t>
1564   This status code is only appropriate when the response status code would
1565   have been 200 (OK) otherwise. When the status code before transformation
1566   would have been different, the 214 Transformation Applied warn-code
1567   (&header-warning;) is appropriate.
1568</t>
1569<t>
1570   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1571   freshness for 203 responses.
1572</t>
1573</section>
1574
1575<section title="204 No Content" anchor="status.204">
1576  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1577  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1578<t>
1579   The 204 (No Content) status code indicates that the server has
1580   successfully fulfilled the request and that there is no additional
1581   content to return in the response payload body.  Metadata in the
1582   response header fields refer to the target resource and its current
1583   representation after the requested action.
1584</t>
1585<t>
1586   For example, if a 204 status code is received in response to a PUT
1587   request and the response contains an ETag header field, then the PUT
1588   was successful and the ETag field-value contains the entity-tag for
1589   the new representation of that target resource.
1590</t>
1591<t>
1592   The 204 response allows a server to indicate that the action has been
1593   successfully applied to the target resource while implying that the
1594   user agent &SHOULD-NOT; traverse away from its current "document view"
1595   (if any).  The server assumes that the user agent will provide some
1596   indication of the success to its user, in accord with its own interface,
1597   and apply any new or updated metadata in the response to the active
1598   representation.
1599</t>
1600<t>
1601   For example, a 204 status code is commonly used with document editing
1602   interfaces corresponding to a "save" action, such that the document
1603   being saved remains available to the user for editing. It is also
1604   frequently used with interfaces that expect automated data transfers
1605   to be prevalent, such as within distributed version control systems.
1606</t>
1607<t>
1608   The 204 response &MUST-NOT; include a message-body, and thus is always
1609   terminated by the first empty line after the header fields.
1610</t>
1611</section>
1612
1613<section title="205 Reset Content" anchor="status.205">
1614  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1615  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1616<t>
1617   The server has fulfilled the request and the user agent &SHOULD; reset
1618   the document view which caused the request to be sent. This response
1619   is primarily intended to allow input for actions to take place via
1620   user input, followed by a clearing of the form in which the input is
1621   given so that the user can easily initiate another input action.
1622</t>
1623<t>   
1624   The message-body included with the response &MUST; be empty. Note that
1625   receivers still need to parse the response according to the algorithm defined
1626   in &message-body;.
1627</t>
1628</section>
1629
1630<section title="206 Partial Content" anchor="status.206">
1631  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1632  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1633  <rdf:Description>
1634    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1635  </rdf:Description>
1636<t>
1637   The server has fulfilled the partial GET request for the resource
1638   and the enclosed payload is a partial representation as defined in &status-206;.
1639</t>
1640<t>
1641   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1642   freshness for 206 responses.
1643</t>
1644</section>
1645</section>
1646
1647<section title="Redirection 3xx" anchor="status.3xx">
1648<t>
1649   This class of status code indicates that further action needs to be
1650   taken by the user agent in order to fulfill the request.  If the required
1651   action involves a subsequent HTTP request, it &MAY; be carried out by the
1652   user agent without interaction with the user if and only if the method used
1653   in the second request is known to be "safe", as defined in
1654   <xref target="safe.methods"/>.
1655</t>
1656<t>
1657   There are several types of redirects:
1658   <list style="numbers">
1659      <x:lt>
1660        <t>
1661          Redirects of the request to another URI, either temporarily or
1662          permanently. The new URI is specified in the Location header field.
1663          In this specification, the status codes 301 (Moved Permanently),
1664          302 (Found), and 307 (Temporary Redirect) fall under this category.
1665        </t>
1666      </x:lt>
1667      <x:lt>
1668        <t>
1669          Redirection to a new location that represents an indirect response to
1670          the request, such as the result of a POST operation to be retrieved
1671          with a subsequent GET request. This is status code 303 (See Other).
1672        </t>
1673      </x:lt>
1674      <x:lt>
1675        <t>
1676          Redirection offering a choice of matching resources for use by
1677          agent-driven content negotiation (&agent-driven-negotiation;). This
1678          is status code 300 (Multiple Choices).
1679        </t>
1680      </x:lt>
1681      <x:lt>
1682        <t>
1683          Other kinds of redirection, such as to a cached result (status code 304
1684          (Not Modified)).
1685        </t>
1686      </x:lt>
1687   </list>
1688</t>
1689<x:note>
1690  <t>
1691    <x:h>Note:</x:h> In HTTP/1.0, only the status codes 301 (Moved Permanently)
1692    and 302 (Found) were defined for the first type of redirect, and the second
1693    type did not exist at all (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>).
1694    However it turned out that web forms using POST expected redirects to change
1695    the operation for the subsequent request to retrieval (GET). To address this
1696    use case, HTTP/1.1 introduced the second type of redirect with the status
1697    code 303 (See Other) (<xref target="RFC2068" x:fmt="," x:sec="10.3.4"/>).
1698    As user agents did not change their behavior to maintain backwards
1699    compatibility, the first revision of HTTP/1.1 added yet another status code,
1700    307 (Temporary Redirect), for which the backwards compatibility problems did
1701    not apply (<xref target="RFC2616" x:fmt="," x:sec="10.3.8"/>).
1702    Over 10 years later, most user agents still do method rewriting for
1703    status codes 301 and 302, therefore this specification makes that behavior
1704    compliant in case the original request was POST.
1705  </t>
1706</x:note>
1707<t>
1708   A Location header field on a 3xx response indicates that a client &MAY;
1709   automatically redirect to the URI provided; see <xref target="header.location"/>.
1710</t>
1711<t>
1712   Clients &SHOULD; detect and intervene in cyclical redirections (i.e.,
1713   "infinite" redirection loops).
1714</t>
1715<x:note>
1716  <t>
1717    <x:h>Note:</x:h> An earlier version of this specification recommended a
1718    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1719    Content developers need to be aware that some clients might
1720    implement such a fixed limitation.
1721  </t>
1722</x:note>
1723
1724<section title="300 Multiple Choices" anchor="status.300">
1725  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1726  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1727<t>
1728   The target resource has more than one
1729   representation, each with its own specific location, and agent-driven
1730   negotiation information (&content-negotiation;) is being provided so that
1731   the user (or user agent) can select a preferred representation by
1732   redirecting its request to that location.
1733</t>
1734<t>
1735   Unless it was a HEAD request, the response &SHOULD; include a representation
1736   containing a list of representation metadata and location(s) from
1737   which the user or user agent can choose the one most appropriate. Depending
1738   upon the format and the capabilities of
1739   the user agent, selection of the most appropriate choice &MAY; be
1740   performed automatically. However, this specification does not define
1741   any standard for such automatic selection.
1742</t>
1743<t>
1744   If the server has a preferred choice of representation, it &SHOULD;
1745   include the specific URI for that representation in the Location
1746   field; user agents &MAY; use the Location field value for automatic
1747   redirection.
1748</t>
1749<t>
1750   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1751   freshness for 300 responses.
1752</t>
1753
1754</section>
1755
1756<section title="301 Moved Permanently" anchor="status.301">
1757  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1758  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1759<t>
1760   The target resource has been assigned a new permanent URI and any
1761   future references to this resource &SHOULD; use one of the returned
1762   URIs.  Clients with link editing capabilities ought to automatically
1763   re-link references to the effective request URI to one or more of the new
1764   references returned by the server, where possible.
1765</t>
1766<t>
1767   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1768   freshness for 301 responses.
1769</t>
1770<t>
1771   The new permanent URI &SHOULD; be given by the Location field in the
1772   response. Unless the request method was HEAD, the representation of the
1773   response &SHOULD; contain a short hypertext note with a hyperlink to
1774   the new URI(s).
1775</t>
1776<t>
1777   If the 301 status code is received in response to a request method
1778   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1779   then the request &MAY; be automatically redirected by the user agent without
1780   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1781   request unless it can be confirmed by the user, since this might
1782   change the conditions under which the request was issued.
1783</t>
1784<x:note>
1785  <t>
1786    <x:h>Note:</x:h> For historic reasons, user agents &MAY; change the
1787    request method from POST to GET for the subsequent request. If this
1788    behavior is undesired, status code 307 (Temporary Redirect) can be used
1789    instead.
1790  </t>
1791</x:note>
1792</section>
1793
1794<section title="302 Found" anchor="status.302">
1795  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1796  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1797<t>
1798   The target resource resides temporarily under a different URI.
1799   Since the redirection might be altered on occasion, the client &SHOULD;
1800   continue to use the effective request URI for future requests.
1801</t>
1802<t>
1803   The temporary URI &SHOULD; be given by the Location field in the
1804   response. Unless the request method was HEAD, the representation of the
1805   response &SHOULD; contain a short hypertext note with a hyperlink to
1806   the new URI(s).
1807</t>
1808<t>
1809   If the 302 status code is received in response to a request method
1810   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1811   then the request &MAY; be automatically redirected by the user agent without
1812   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1813   request unless it can be confirmed by the user, since this might
1814   change the conditions under which the request was issued.
1815</t>
1816<x:note>
1817  <t>
1818    <x:h>Note:</x:h> For historic reasons, user agents &MAY; change the
1819    request method from POST to GET for the subsequent request. If this
1820    behavior is undesired, status code 307 (Temporary Redirect) can be used
1821    instead.
1822  </t>
1823</x:note>
1824</section>
1825
1826<section title="303 See Other" anchor="status.303">
1827  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1828  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1829<t>
1830   The 303 status code indicates that the server is redirecting the
1831   user agent to a different resource, as indicated by a URI in the
1832   Location header field, that is intended to provide an indirect
1833   response to the original request.  In order to satisfy the original
1834   request, a user agent &SHOULD; perform a retrieval request using the
1835   Location URI (a GET or HEAD request if using HTTP), which
1836   may itself be redirected further, and present the eventual result as an
1837   answer to the original request.
1838   Note that the new URI in the Location header field is not considered
1839   equivalent to the effective request URI.
1840</t>
1841<t>
1842   This status code is generally applicable to any HTTP method.  It is
1843   primarily used to allow the output of a POST action to redirect
1844   the user agent to a selected resource, since doing so provides the
1845   information corresponding to the POST response in a form that
1846   can be separately identified, bookmarked, and cached independent
1847   of the original request.
1848</t>
1849<t>
1850   A 303 response to a GET request indicates that the requested
1851   resource does not have a representation of its own that can be
1852   transferred by the server over HTTP.  The Location URI indicates a
1853   resource that is descriptive of the target resource, such that the
1854   follow-on representation might be useful to recipients without
1855   implying that it adequately represents the target resource.
1856   Note that answers to the questions of what can be represented, what
1857   representations are adequate, and what might be a useful description
1858   are outside the scope of HTTP and thus entirely determined by the
1859   URI owner(s).
1860</t>
1861<t>
1862   Except for responses to a HEAD request, the representation of a 303
1863   response &SHOULD; contain a short hypertext note with a hyperlink
1864   to the Location URI.
1865</t>
1866</section>
1867
1868<section title="304 Not Modified" anchor="status.304">
1869  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1870  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1871  <rdf:Description>
1872    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1873  </rdf:Description>
1874<t>
1875   The response to the request has not been modified since the conditions
1876   indicated by the client's conditional GET request, as defined in &status-304;.
1877</t>
1878</section>
1879
1880<section title="305 Use Proxy" anchor="status.305">
1881  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1882  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1883<t>
1884   The 305 status code was defined in a previous version of this specification
1885   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1886</t>
1887</section>
1888
1889<section title="306 (Unused)" anchor="status.306">
1890  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1891  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1892<t>
1893   The 306 status code was used in a previous version of the
1894   specification, is no longer used, and the code is reserved.
1895</t>
1896</section>
1897
1898<section title="307 Temporary Redirect" anchor="status.307">
1899  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1900  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1901<t>
1902   The target resource resides temporarily under a different URI.
1903   Since the redirection can change over time, the client &SHOULD;
1904   continue to use the effective request URI for future requests.
1905</t>
1906<t>
1907   The temporary URI &SHOULD; be given by the Location field in the
1908   response. Unless the request method was HEAD, the representation of the
1909   response &SHOULD; contain a short hypertext note with a hyperlink to
1910   the new URI(s).
1911</t>
1912<t>
1913   If the 307 status code is received in response to a request method
1914   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1915   then the request &MAY; be automatically redirected by the user agent without
1916   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1917   request unless it can be confirmed by the user, since this might
1918   change the conditions under which the request was issued.
1919</t>
1920<x:note>
1921  <t>
1922    <x:h>Note:</x:h> This status code is similar to 302 Found, except that
1923    it does not allow rewriting the request method from POST to GET. This
1924    specification defines no equivalent counterpart for 301 Moved Permanently.
1925  </t>
1926</x:note>
1927</section>
1928</section>
1929
1930<section title="Client Error 4xx" anchor="status.4xx">
1931<t>
1932   The 4xx class of status code is intended for cases in which the
1933   client seems to have erred. Except when responding to a HEAD request,
1934   the server &SHOULD; include a representation containing an explanation of the
1935   error situation, and whether it is a temporary or permanent
1936   condition. These status codes are applicable to any request method.
1937   User agents &SHOULD; display any included representation to the user.
1938</t>
1939<t>
1940   If the client is sending data, a server implementation using TCP
1941   &SHOULD; be careful to ensure that the client acknowledges receipt of
1942   the packet(s) containing the response, before the server closes the
1943   input connection. If the client continues sending data to the server
1944   after the close, the server's TCP stack will send a reset packet to
1945   the client, which might erase the client's unacknowledged input buffers
1946   before they can be read and interpreted by the HTTP application.
1947</t>
1948
1949<section title="400 Bad Request" anchor="status.400">
1950  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1951  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1952<t>
1953   The server cannot or will not process the request, due to a client error (e.g.,
1954   malformed syntax).</t>
1955</section>
1956
1957<section title="401 Unauthorized" anchor="status.401">
1958  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1959  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1960  <rdf:Description>
1961    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1962  </rdf:Description>
1963<t>
1964   The request requires user authentication (see &status-401;).
1965</t>
1966</section>
1967
1968<section title="402 Payment Required" anchor="status.402">
1969  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1970  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1971<t>
1972   This code is reserved for future use.
1973</t>
1974</section>
1975
1976<section title="403 Forbidden" anchor="status.403">
1977  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1978  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1979<t>
1980   The server understood the request, but refuses to authorize it. Providing
1981   different user authentication credentials might be successful, but any
1982   credentials that were provided in the request are insufficient. The request
1983   &SHOULD-NOT; be repeated with the same credentials.
1984</t>
1985<t>
1986   If the request method was not HEAD and the server wishes to make
1987   public why the request has not been fulfilled, it &SHOULD; describe the
1988   reason for the refusal in the representation.  If the server does not wish to
1989   make this information available to the client, the status code 404
1990   (Not Found) &MAY; be used instead.
1991</t>
1992</section>
1993
1994<section title="404 Not Found" anchor="status.404">
1995  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1996  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1997<t>
1998   The server has not found anything matching the effective request URI. No
1999   indication is given of whether the condition is temporary or
2000   permanent. The 410 (Gone) status code &SHOULD; be used if the server
2001   knows, through some internally configurable mechanism, that an old
2002   resource is permanently unavailable and has no forwarding address.
2003   This status code is commonly used when the server does not wish to
2004   reveal exactly why the request has been refused, or when no other
2005   response is applicable.
2006</t>
2007</section>
2008
2009<section title="405 Method Not Allowed" anchor="status.405">
2010  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
2011  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
2012<t>
2013   The method specified in the Request-Line is not allowed for the target
2014   resource. The response &MUST; include an Allow header field containing a
2015   list of valid methods for the requested resource.
2016</t>
2017</section>
2018
2019<section title="406 Not Acceptable" anchor="status.406">
2020  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
2021  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
2022<t>
2023   The resource identified by the request is only capable of generating
2024   response representations which have content characteristics not acceptable
2025   according to the Accept and Accept-* header fields sent in the request
2026   (see &p3-header-fields;).
2027</t>
2028<t>
2029   Unless it was a HEAD request, the response &SHOULD; include a representation
2030   containing a list of available representation characteristics and location(s)
2031   from which the user or user agent can choose the one most
2032   appropriate. Depending upon the format and the
2033   capabilities of the user agent, selection of the most appropriate
2034   choice &MAY; be performed automatically. However, this specification
2035   does not define any standard for such automatic selection.
2036</t>
2037<x:note>
2038  <t>
2039    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
2040    not acceptable according to the accept header fields sent in the
2041    request. In some cases, this might even be preferable to sending a
2042    406 response. User agents are encouraged to inspect the header fields of
2043    an incoming response to determine if it is acceptable.
2044  </t>
2045</x:note>
2046<t>
2047   If the response could be unacceptable, a user agent &SHOULD;
2048   temporarily stop receipt of more data and query the user for a
2049   decision on further actions.
2050</t>
2051</section>
2052
2053<section title="407 Proxy Authentication Required" anchor="status.407">
2054  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
2055  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
2056<t>
2057   This code is similar to 401 (Unauthorized), but indicates that the
2058   client must first authenticate itself with the proxy (see &status-407;).
2059</t>
2060</section>
2061
2062<section title="408 Request Timeout" anchor="status.408">
2063  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
2064  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
2065<t>
2066   The client did not produce a request within the time that the server
2067   was prepared to wait. The client &MAY; repeat the request without
2068   modifications at any later time.
2069</t>
2070</section>
2071
2072<section title="409 Conflict" anchor="status.409">
2073  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
2074  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
2075<t>
2076   The request could not be completed due to a conflict with the current
2077   state of the resource. This code is only allowed in situations where
2078   it is expected that the user might be able to resolve the conflict
2079   and resubmit the request. The response body &SHOULD; include enough
2080   information for the user to recognize the source of the conflict.
2081   Ideally, the response representation would include enough information for the
2082   user or user agent to fix the problem; however, that might not be
2083   possible and is not required.
2084</t>
2085<t>
2086   Conflicts are most likely to occur in response to a PUT request. For
2087   example, if versioning were being used and the representation being PUT
2088   included changes to a resource which conflict with those made by an
2089   earlier (third-party) request, the server might use the 409 response
2090   to indicate that it can't complete the request. In this case, the
2091   response representation would likely contain a list of the differences
2092   between the two versions.
2093</t>
2094</section>
2095
2096<section title="410 Gone" anchor="status.410">
2097  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
2098  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
2099<t>
2100   The target resource is no longer available at the server and no
2101   forwarding address is known. This condition is expected to be
2102   considered permanent. Clients with link editing capabilities &SHOULD;
2103   delete references to the effective request URI after user approval. If the
2104   server does not know, or has no facility to determine, whether or not
2105   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
2106   used instead.
2107</t>
2108<t>
2109   The 410 response is primarily intended to assist the task of web
2110   maintenance by notifying the recipient that the resource is
2111   intentionally unavailable and that the server owners desire that
2112   remote links to that resource be removed. Such an event is common for
2113   limited-time, promotional services and for resources belonging to
2114   individuals no longer working at the server's site. It is not
2115   necessary to mark all permanently unavailable resources as "gone" or
2116   to keep the mark for any length of time &mdash; that is left to the
2117   discretion of the server owner.
2118</t>
2119<t>
2120   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine freshness
2121   for 410 responses.
2122</t>
2123
2124</section>
2125
2126<section title="411 Length Required" anchor="status.411">
2127  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
2128  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
2129<t>
2130   The server refuses to accept the request without a defined Content-Length.
2131   The client &MAY; repeat the request if it adds a valid
2132   Content-Length header field containing the length of the message-body
2133   in the request message.
2134</t>
2135</section>
2136
2137<section title="412 Precondition Failed" anchor="status.412">
2138  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
2139  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
2140  <rdf:Description>
2141    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
2142  </rdf:Description>
2143<t>
2144   The precondition given in one or more of the header fields
2145   evaluated to false when it was tested on the server, as defined in
2146   &status-412;.
2147</t>
2148</section>
2149
2150<section title="413 Request Representation Too Large" anchor="status.413">
2151  <iref primary="true" item="413 Request Representation Too Large (status code)" x:for-anchor=""/>
2152  <iref primary="true" item="Status Codes" subitem="413 Request Representation Too Large" x:for-anchor=""/>
2153<t>
2154   The server is refusing to process a request because the request
2155   representation is larger than the server is willing or able to process. The
2156   server &MAY; close the connection to prevent the client from continuing
2157   the request.
2158</t>
2159<t>
2160   If the condition is temporary, the server &SHOULD; include a Retry-After
2161   header field to indicate that it is temporary and after what
2162   time the client &MAY; try again.
2163</t>
2164</section>
2165
2166<section title="414 URI Too Long" anchor="status.414">
2167  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
2168  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
2169<t>
2170   The server is refusing to service the request because the effective request URI
2171   is longer than the server is willing to interpret. This rare
2172   condition is only likely to occur when a client has improperly
2173   converted a POST request to a GET request with long query
2174   information, when the client has descended into a URI "black hole" of
2175   redirection (e.g., a redirected URI prefix that points to a suffix of
2176   itself), or when the server is under attack by a client attempting to
2177   exploit security holes present in some servers using fixed-length
2178   buffers for reading or manipulating the effective request URI.
2179</t>
2180</section>
2181
2182<section title="415 Unsupported Media Type" anchor="status.415">
2183  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
2184  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
2185<t>
2186   The server is refusing to service the request because the request
2187   payload is in a format not supported by this request method on the
2188   target resource.
2189</t>
2190</section>
2191
2192<section title="416 Requested Range Not Satisfiable" anchor="status.416">
2193  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
2194  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
2195  <rdf:Description>
2196    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
2197  </rdf:Description>
2198<t>
2199   The request included a Range header field (&header-range;) and none of
2200   the range-specifier values in this field overlap the current extent
2201   of the selected resource. See &status-416;.
2202</t>
2203</section>
2204
2205<section title="417 Expectation Failed" anchor="status.417">
2206  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
2207  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
2208<t>
2209   The expectation given in an Expect header field (see <xref target="header.expect"/>)
2210   could not be met by this server, or, if the server is a proxy,
2211   the server has unambiguous evidence that the request could not be met
2212   by the next-hop server.
2213</t>
2214</section>
2215
2216<section title="426 Upgrade Required" anchor="status.426">
2217  <iref primary="true" item="426 Upgrade Required (status code)" x:for-anchor=""/>
2218  <iref primary="true" item="Status Codes" subitem="426 Upgrade Required" x:for-anchor=""/>
2219<t>
2220   The request can not be completed without a prior protocol upgrade. This
2221   response &MUST; include an Upgrade header field (&header-upgrade;)
2222   specifying the required protocols.
2223</t>
2224<figure>
2225<preamble>Example:</preamble>
2226<artwork type="message/http; msgtype=&#34;response&#34;" x:indent-with="  ">
2227HTTP/1.1 426 Upgrade Required
2228Upgrade: HTTP/3.0
2229Connection: Upgrade
2230Content-Length: <x:length-of target="s426body"/>
2231Content-Type: text/plain
2232
2233<x:span anchor="s426body">This service requires use of the HTTP/3.0 protocol.
2234</x:span></artwork></figure>
2235<t>
2236   The server &SHOULD; include a message body in the 426 response which
2237   indicates in human readable form the reason for the error and describes any
2238   alternative courses which may be available to the user.
2239</t>
2240</section>
2241</section>
2242
2243<section title="Server Error 5xx" anchor="status.5xx">
2244<t>
2245   Response status codes beginning with the digit "5" indicate cases in
2246   which the server is aware that it has erred or is incapable of
2247   performing the request. Except when responding to a HEAD request, the
2248   server &SHOULD; include a representation containing an explanation of the
2249   error situation, and whether it is a temporary or permanent
2250   condition. User agents &SHOULD; display any included representation to the
2251   user. These response codes are applicable to any request method.
2252</t>
2253
2254<section title="500 Internal Server Error" anchor="status.500">
2255  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
2256  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
2257<t>
2258   The server encountered an unexpected condition which prevented it
2259   from fulfilling the request.
2260</t>
2261</section>
2262
2263<section title="501 Not Implemented" anchor="status.501">
2264  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
2265  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
2266<t>
2267   The server does not support the functionality required to fulfill the
2268   request. This is the appropriate response when the server does not
2269   recognize the request method and is not capable of supporting it for
2270   any resource.
2271</t>
2272</section>
2273
2274<section title="502 Bad Gateway" anchor="status.502">
2275  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
2276  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
2277<t>
2278   The server, while acting as a gateway or proxy, received an invalid
2279   response from the upstream server it accessed in attempting to
2280   fulfill the request.
2281</t>
2282</section>
2283
2284<section title="503 Service Unavailable" anchor="status.503">
2285  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
2286  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
2287<t>
2288   The server is currently unable to handle the request due to a
2289   temporary overloading or maintenance of the server.
2290</t>
2291<t>
2292   The implication is that this is a temporary condition which will be
2293   alleviated after some delay. If known, the length of the delay &MAY; be
2294   indicated in a Retry-After header field (<xref target="header.retry-after"/>).
2295   If no Retry-After is given, the client &SHOULD; handle the response as it
2296   would for a 500 response.
2297</t>
2298<x:note>
2299  <t>
2300    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
2301    server must use it when becoming overloaded. Some servers might wish
2302    to simply refuse the connection.
2303  </t>
2304</x:note>
2305</section>
2306
2307<section title="504 Gateway Timeout" anchor="status.504">
2308  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
2309  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
2310<t>
2311   The server, while acting as a gateway or proxy, did not receive a
2312   timely response from the upstream server specified by the URI (e.g.,
2313   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
2314   to access in attempting to complete the request.
2315</t>
2316<x:note>
2317  <t>
2318    <x:h>Note</x:h> to implementors: some deployed proxies are known to
2319    return 400 or 500 when DNS lookups time out.
2320  </t>
2321</x:note>
2322</section>
2323
2324<section title="505 HTTP Version Not Supported" anchor="status.505">
2325  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
2326  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
2327<t>
2328   The server does not support, or refuses to support, the protocol
2329   version that was used in the request message. The server is
2330   indicating that it is unable or unwilling to complete the request
2331   using the same major version as the client, as described in &http-version;,
2332   other than with this error message. The response &SHOULD; contain
2333   a representation describing why that version is not supported and what other
2334   protocols are supported by that server.
2335</t>
2336
2337</section>
2338</section>
2339</section>
2340
2341
2342<section title="Date/Time Formats" anchor="http.date">
2343  <x:anchor-alias value="HTTP-date"/>
2344<t>
2345   HTTP applications have historically allowed three different formats
2346   for date/time stamps. However, the preferred format is a fixed-length subset
2347   of that defined by <xref target="RFC1123"/>:
2348</t>
2349<figure><artwork type="example" x:indent-with="  ">
2350Sun, 06 Nov 1994 08:49:37 GMT  ; RFC 1123
2351</artwork></figure>
2352<t>
2353   The other formats are described here only for compatibility with obsolete
2354   implementations.
2355</t>
2356<figure><artwork type="example" x:indent-with="  ">
2357Sunday, 06-Nov-94 08:49:37 GMT ; obsolete RFC 850 format
2358Sun Nov  6 08:49:37 1994       ; ANSI C's asctime() format
2359</artwork></figure>
2360<t>
2361   HTTP/1.1 clients and servers that parse a date value &MUST; accept
2362   all three formats (for compatibility with HTTP/1.0), though they &MUST;
2363   only generate the RFC 1123 format for representing HTTP-date values
2364   in header fields.
2365</t>
2366<t>
2367   All HTTP date/time stamps &MUST; be represented in Greenwich Mean Time
2368   (GMT), without exception. For the purposes of HTTP, GMT is exactly
2369   equal to UTC (Coordinated Universal Time). This is indicated in the
2370   first two formats by the inclusion of "GMT" as the three-letter
2371   abbreviation for time zone, and &MUST; be assumed when reading the
2372   asctime format. HTTP-date is case sensitive and &MUST-NOT; include
2373   additional whitespace beyond that specifically included as SP in the
2374   grammar.
2375</t>
2376<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="HTTP-date"/>
2377  <x:ref>HTTP-date</x:ref>    = <x:ref>rfc1123-date</x:ref> / <x:ref>obs-date</x:ref>
2378</artwork></figure>
2379<t anchor="preferred.date.format">
2380  <x:anchor-alias value="rfc1123-date"/>
2381  <x:anchor-alias value="time-of-day"/>
2382  <x:anchor-alias value="hour"/>
2383  <x:anchor-alias value="minute"/>
2384  <x:anchor-alias value="second"/>
2385  <x:anchor-alias value="day-name"/>
2386  <x:anchor-alias value="day"/>
2387  <x:anchor-alias value="month"/>
2388  <x:anchor-alias value="year"/>
2389  <x:anchor-alias value="GMT"/>
2390  Preferred format:
2391</t>
2392<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="rfc1123-date"/><iref primary="true" item="Grammar" subitem="date1"/><iref primary="true" item="Grammar" subitem="time-of-day"/><iref primary="true" item="Grammar" subitem="hour"/><iref primary="true" item="Grammar" subitem="minute"/><iref primary="true" item="Grammar" subitem="second"/><iref primary="true" item="Grammar" subitem="day-name"/><iref primary="true" item="Grammar" subitem="day-name-l"/><iref primary="true" item="Grammar" subitem="day"/><iref primary="true" item="Grammar" subitem="month"/><iref primary="true" item="Grammar" subitem="year"/><iref primary="true" item="Grammar" subitem="GMT"/>
2393  <x:ref>rfc1123-date</x:ref> = <x:ref>day-name</x:ref> "," <x:ref>SP</x:ref> date1 <x:ref>SP</x:ref> <x:ref>time-of-day</x:ref> <x:ref>SP</x:ref> <x:ref>GMT</x:ref>
2394  ; fixed length subset of the format defined in
2395  ; <xref target="RFC1123" x:fmt="of" x:sec="5.2.14"/>
2396 
2397  <x:ref>day-name</x:ref>     = <x:abnf-char-sequence>"Mon"</x:abnf-char-sequence> ; "Mon", case-sensitive
2398               / <x:abnf-char-sequence>"Tue"</x:abnf-char-sequence> ; "Tue", case-sensitive
2399               / <x:abnf-char-sequence>"Wed"</x:abnf-char-sequence> ; "Wed", case-sensitive
2400               / <x:abnf-char-sequence>"Thu"</x:abnf-char-sequence> ; "Thu", case-sensitive
2401               / <x:abnf-char-sequence>"Fri"</x:abnf-char-sequence> ; "Fri", case-sensitive
2402               / <x:abnf-char-sequence>"Sat"</x:abnf-char-sequence> ; "Sat", case-sensitive
2403               / <x:abnf-char-sequence>"Sun"</x:abnf-char-sequence> ; "Sun", case-sensitive
2404               
2405  <x:ref>date1</x:ref>        = <x:ref>day</x:ref> <x:ref>SP</x:ref> <x:ref>month</x:ref> <x:ref>SP</x:ref> <x:ref>year</x:ref>
2406               ; e.g., 02 Jun 1982
2407
2408  <x:ref>day</x:ref>          = 2<x:ref>DIGIT</x:ref>
2409  <x:ref>month</x:ref>        = <x:abnf-char-sequence>"Jan"</x:abnf-char-sequence> ; "Jan", case-sensitive
2410               / <x:abnf-char-sequence>"Feb"</x:abnf-char-sequence> ; "Feb", case-sensitive
2411               / <x:abnf-char-sequence>"Mar"</x:abnf-char-sequence> ; "Mar", case-sensitive
2412               / <x:abnf-char-sequence>"Apr"</x:abnf-char-sequence> ; "Apr", case-sensitive
2413               / <x:abnf-char-sequence>"May"</x:abnf-char-sequence> ; "May", case-sensitive
2414               / <x:abnf-char-sequence>"Jun"</x:abnf-char-sequence> ; "Jun", case-sensitive
2415               / <x:abnf-char-sequence>"Jul"</x:abnf-char-sequence> ; "Jul", case-sensitive
2416               / <x:abnf-char-sequence>"Aug"</x:abnf-char-sequence> ; "Aug", case-sensitive
2417               / <x:abnf-char-sequence>"Sep"</x:abnf-char-sequence> ; "Sep", case-sensitive
2418               / <x:abnf-char-sequence>"Oct"</x:abnf-char-sequence> ; "Oct", case-sensitive
2419               / <x:abnf-char-sequence>"Nov"</x:abnf-char-sequence> ; "Nov", case-sensitive
2420               / <x:abnf-char-sequence>"Dec"</x:abnf-char-sequence> ; "Dec", case-sensitive
2421  <x:ref>year</x:ref>         = 4<x:ref>DIGIT</x:ref>
2422
2423  <x:ref>GMT</x:ref>   = <x:abnf-char-sequence>"GMT"</x:abnf-char-sequence> ; "GMT", case-sensitive
2424
2425  <x:ref>time-of-day</x:ref>  = <x:ref>hour</x:ref> ":" <x:ref>minute</x:ref> ":" <x:ref>second</x:ref>
2426                 ; 00:00:00 - 23:59:59
2427                 
2428  <x:ref>hour</x:ref>         = 2<x:ref>DIGIT</x:ref>               
2429  <x:ref>minute</x:ref>       = 2<x:ref>DIGIT</x:ref>               
2430  <x:ref>second</x:ref>       = 2<x:ref>DIGIT</x:ref>               
2431</artwork></figure>
2432<t>
2433  The semantics of <x:ref>day-name</x:ref>, <x:ref>day</x:ref>,
2434  <x:ref>month</x:ref>, <x:ref>year</x:ref>, and <x:ref>time-of-day</x:ref> are the
2435  same as those defined for the RFC 5322 constructs
2436  with the corresponding name (<xref target="RFC5322" x:fmt="," x:sec="3.3"/>).
2437</t>
2438<t anchor="obsolete.date.formats">
2439  <x:anchor-alias value="obs-date"/>
2440  <x:anchor-alias value="rfc850-date"/>
2441  <x:anchor-alias value="asctime-date"/>
2442  <x:anchor-alias value="date1"/>
2443  <x:anchor-alias value="date2"/>
2444  <x:anchor-alias value="date3"/>
2445  <x:anchor-alias value="rfc1123-date"/>
2446  <x:anchor-alias value="day-name-l"/>
2447  Obsolete formats:
2448</t>
2449<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="obs-date"/>
2450  <x:ref>obs-date</x:ref>     = <x:ref>rfc850-date</x:ref> / <x:ref>asctime-date</x:ref> 
2451</artwork></figure>
2452<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="rfc850-date"/>
2453  <x:ref>rfc850-date</x:ref>  = <x:ref>day-name-l</x:ref> "," <x:ref>SP</x:ref> <x:ref>date2</x:ref> <x:ref>SP</x:ref> <x:ref>time-of-day</x:ref> <x:ref>SP</x:ref> <x:ref>GMT</x:ref>
2454  <x:ref>date2</x:ref>        = <x:ref>day</x:ref> "-" <x:ref>month</x:ref> "-" 2<x:ref>DIGIT</x:ref>
2455                 ; day-month-year (e.g., 02-Jun-82)
2456
2457  <x:ref>day-name-l</x:ref>   = <x:abnf-char-sequence>"Monday"</x:abnf-char-sequence> ; "Monday", case-sensitive
2458         / <x:abnf-char-sequence>"Tuesday"</x:abnf-char-sequence> ; "Tuesday", case-sensitive
2459         / <x:abnf-char-sequence>"Wednesday"</x:abnf-char-sequence> ; "Wednesday", case-sensitive
2460         / <x:abnf-char-sequence>"Thursday"</x:abnf-char-sequence> ; "Thursday", case-sensitive
2461         / <x:abnf-char-sequence>"Friday"</x:abnf-char-sequence> ; "Friday", case-sensitive
2462         / <x:abnf-char-sequence>"Saturday"</x:abnf-char-sequence> ; "Saturday", case-sensitive
2463         / <x:abnf-char-sequence>"Sunday"</x:abnf-char-sequence> ; "Sunday", case-sensitive
2464</artwork></figure>
2465<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="asctime-date"/>
2466  <x:ref>asctime-date</x:ref> = <x:ref>day-name</x:ref> <x:ref>SP</x:ref> <x:ref>date3</x:ref> <x:ref>SP</x:ref> <x:ref>time-of-day</x:ref> <x:ref>SP</x:ref> <x:ref>year</x:ref>
2467  <x:ref>date3</x:ref>        = <x:ref>month</x:ref> <x:ref>SP</x:ref> ( 2<x:ref>DIGIT</x:ref> / ( <x:ref>SP</x:ref> 1<x:ref>DIGIT</x:ref> ))
2468                 ; month day (e.g., Jun  2)
2469</artwork></figure>
2470<x:note>
2471  <t>
2472    <x:h>Note:</x:h> Recipients of date values are encouraged to be robust in
2473    accepting date values that might have been sent by non-HTTP
2474    applications, as is sometimes the case when retrieving or posting
2475    messages via proxies/gateways to SMTP or NNTP.
2476  </t>
2477</x:note>
2478<x:note>
2479  <t>
2480    <x:h>Note:</x:h> HTTP requirements for the date/time stamp format apply only
2481    to their usage within the protocol stream. Clients and servers are
2482    not required to use these formats for user presentation, request
2483    logging, etc.
2484  </t>
2485</x:note>
2486</section>
2487
2488
2489<section title="Header Field Definitions" anchor="header.field.definitions">
2490<t>
2491   This section defines the syntax and semantics of HTTP/1.1 header fields
2492   related to request and response semantics.
2493</t>
2494
2495<section title="Allow" anchor="header.allow">
2496  <iref primary="true" item="Allow header field" x:for-anchor=""/>
2497  <iref primary="true" item="Header Fields" subitem="Allow" x:for-anchor=""/>
2498  <x:anchor-alias value="Allow"/>
2499<t>
2500   The "Allow" header field lists the set of methods advertised as
2501   supported by the target resource. The purpose of this field is strictly to
2502   inform the recipient of valid request methods associated with the resource.
2503</t>
2504<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/>
2505  <x:ref>Allow</x:ref> = #<x:ref>Method</x:ref>
2506</artwork></figure>
2507<t>
2508   Example of use:
2509</t>
2510<figure><artwork type="example">
2511  Allow: GET, HEAD, PUT
2512</artwork></figure>
2513<t>
2514   The actual set of allowed methods is defined by the origin server at the
2515   time of each request.
2516</t>
2517<t>
2518   A proxy &MUST-NOT; modify the Allow header field &mdash; it does not need to
2519   understand all the methods specified in order to handle them according to
2520   the generic message handling rules.
2521</t>
2522</section>
2523
2524<section title="Date" anchor="header.date">
2525  <iref primary="true" item="Date header field" x:for-anchor=""/>
2526  <iref primary="true" item="Header Fields" subitem="Date" x:for-anchor=""/>
2527  <x:anchor-alias value="Date"/>
2528<t>
2529   The "Date" header field represents the date and time at which
2530   the message was originated, having the same semantics as the Origination
2531   Date Field (orig-date) defined in <xref target="RFC5322" x:fmt="of" x:sec="3.6.1"/>.
2532   The field value is an HTTP-date, as defined in <xref target="http.date"/>;
2533   it &MUST; be sent in rfc1123-date format.
2534</t>
2535<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Date"/>
2536  <x:ref>Date</x:ref> = <x:ref>HTTP-date</x:ref>
2537</artwork></figure>
2538<t>
2539   An example is
2540</t>
2541<figure><artwork type="example">
2542  Date: Tue, 15 Nov 1994 08:12:31 GMT
2543</artwork></figure>
2544<t>
2545   Origin servers &MUST; include a Date header field in all responses,
2546   except in these cases:
2547  <list style="numbers">
2548      <t>If the response status code is 100 (Continue) or 101 (Switching
2549         Protocols), the response &MAY; include a Date header field, at
2550         the server's option.</t>
2551
2552      <t>If the response status code conveys a server error, e.g., 500
2553         (Internal Server Error) or 503 (Service Unavailable), and it is
2554         inconvenient or impossible to generate a valid Date.</t>
2555
2556      <t>If the server does not have a clock that can provide a
2557         reasonable approximation of the current time, its responses
2558         &MUST-NOT; include a Date header field.</t>
2559  </list>
2560</t>
2561<t>
2562   A received message that does not have a Date header field &MUST; be
2563   assigned one by the recipient if the message will be cached by that
2564   recipient.
2565</t>
2566<t>
2567   Clients can use the Date header field as well; in order to keep request
2568   messages small, they are advised not to include it when it doesn't convey
2569   any useful information (as is usually the case for requests that do not
2570   contain a payload).
2571</t>
2572<t>
2573   The HTTP-date sent in a Date header field &SHOULD-NOT; represent a date and
2574   time subsequent to the generation of the message. It &SHOULD; represent
2575   the best available approximation of the date and time of message
2576   generation, unless the implementation has no means of generating a
2577   reasonably accurate date and time. In theory, the date ought to
2578   represent the moment just before the payload is generated. In
2579   practice, the date can be generated at any time during the message
2580   origination without affecting its semantic value.
2581</t>
2582</section>
2583
2584<section title="Expect" anchor="header.expect">
2585  <iref primary="true" item="Expect header field" x:for-anchor=""/>
2586  <iref primary="true" item="Header Fields" subitem="Expect" x:for-anchor=""/>
2587  <x:anchor-alias value="Expect"/>
2588  <x:anchor-alias value="expectation"/>
2589  <x:anchor-alias value="expect-param"/>
2590  <x:anchor-alias value="expect-name"/>
2591  <x:anchor-alias value="expect-value"/>
2592<t>
2593   The "Expect" header field is used to indicate that particular
2594   server behaviors are required by the client.
2595</t>
2596<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Expect"/><iref primary="true" item="Grammar" subitem="expectation"/><iref primary="true" item="Grammar" subitem="expect-param"/><iref primary="true" item="Grammar" subitem="expect-value"/><iref primary="true" item="Grammar" subitem="expect-name"/>
2597  <x:ref>Expect</x:ref>       = 1#<x:ref>expectation</x:ref>
2598 
2599  <x:ref>expectation</x:ref>  = <x:ref>expect-name</x:ref> [ <x:ref>BWS</x:ref> "=" <x:ref>BWS</x:ref> <x:ref>expect-value</x:ref> ]
2600                             *( <x:ref>OWS</x:ref> ";" [ <x:ref>OWS</x:ref> <x:ref>expect-param</x:ref> ] )
2601  <x:ref>expect-param</x:ref> = <x:ref>expect-name</x:ref> [ <x:ref>BWS</x:ref> "=" <x:ref>BWS</x:ref> <x:ref>expect-value</x:ref> ]
2602 
2603  <x:ref>expect-name</x:ref>  = <x:ref>token</x:ref>
2604  <x:ref>expect-value</x:ref> = <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref>
2605</artwork></figure>
2606<t>
2607   If all received Expect header field(s) are syntactically valid but contain
2608   an expectation that the recipient does not understand or cannot comply with,
2609   the recipient &MUST; respond with a 417 (Expectation Failed) status code. A
2610   recipient of a syntactically invalid Expectation header field &MUST; respond
2611   with a 4xx status code other than 417.
2612</t>
2613<t>
2614   The only expectation defined by this specification is:
2615</t>
2616<t><iref primary="true" item="100-continue (expect value)"/><iref primary="true" item="Expect Values" subitem="100-continue"/>
2617  100-continue
2618   <list>
2619      <t>
2620        The "100-continue" expectation is defined &use100;. It does not support
2621        any expect-params.
2622      </t>
2623   </list>
2624</t>
2625<t>
2626   Comparison is case-insensitive for names (expect-name), and case-sensitive
2627   for values (expect-value).
2628</t>
2629<t>
2630   The Expect mechanism is hop-by-hop: the above requirements apply to any
2631   server, including proxies. However, the Expect header field itself is
2632   end-to-end; it &MUST; be forwarded if the request is forwarded.
2633</t>
2634<t>
2635   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the Expect
2636   header field.
2637</t>
2638</section>
2639
2640<section title="From" anchor="header.from">
2641  <iref primary="true" item="From header field" x:for-anchor=""/>
2642  <iref primary="true" item="Header Fields" subitem="From" x:for-anchor=""/>
2643  <x:anchor-alias value="From"/>
2644  <x:anchor-alias value="mailbox"/>
2645<t>
2646   The "From" header field, if given, &SHOULD; contain an Internet
2647   e-mail address for the human user who controls the requesting user
2648   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
2649   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
2650</t>
2651<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/>
2652  <x:ref>From</x:ref>    = <x:ref>mailbox</x:ref>
2653 
2654  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2655</artwork></figure>
2656<t>
2657   An example is:
2658</t>
2659<figure><artwork type="example">
2660  From: webmaster@example.org
2661</artwork></figure>
2662<t>
2663   This header field &MAY; be used for logging purposes and as a means for
2664   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2665   be used as an insecure form of access protection. The interpretation
2666   of this field is that the request is being performed on behalf of the
2667   person given, who accepts responsibility for the method performed. In
2668   particular, robot agents &SHOULD; include this header field so that the
2669   person responsible for running the robot can be contacted if problems
2670   occur on the receiving end.
2671</t>
2672<t>
2673   The Internet e-mail address in this field &MAY; be separate from the
2674   Internet host which issued the request. For example, when a request
2675   is passed through a proxy the original issuer's address &SHOULD; be
2676   used.
2677</t>
2678<t>
2679   The client &SHOULD-NOT;  send the From header field without the user's
2680   approval, as it might conflict with the user's privacy interests or
2681   their site's security policy. It is strongly recommended that the
2682   user be able to disable, enable, and modify the value of this field
2683   at any time prior to a request.
2684</t>
2685</section>
2686
2687<section title="Location" anchor="header.location">
2688  <iref primary="true" item="Location header field" x:for-anchor=""/>
2689  <iref primary="true" item="Header Fields" subitem="Location" x:for-anchor=""/>
2690  <x:anchor-alias value="Location"/>
2691<t>
2692   The "Location" header field is used to identify a newly created
2693   resource, or to redirect the recipient to a different location for
2694   completion of the request.
2695</t>
2696<t>
2697   For 201 (Created) responses, the Location is the URI of the new resource
2698   which was created by the request. For 3xx responses, the location &SHOULD;
2699   indicate the server's preferred URI for automatic redirection to the
2700   resource.
2701</t>
2702<t>
2703   The field value consists of a single URI-reference. When it has the form
2704   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2705   the final value is computed by resolving it against the effective request
2706   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
2707</t>
2708<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/>
2709  <x:ref>Location</x:ref> = <x:ref>URI-reference</x:ref>
2710</artwork></figure>
2711<figure>
2712<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical spacing below, it's necessary this way for xml2rfc-->
2713<artwork type="example">
2714  Location: http://www.example.org/pub/WWW/People.html#tim
2715</artwork></figure><figure><artwork type="example">  Location: /index.html
2716</artwork></figure>
2717<x:note>
2718  <t>
2719    <x:h>Note:</x:h> Some recipients attempt to recover from Location fields
2720    that are not valid URI references. This specification does not mandate or
2721    define such processing, but does allow it (see <xref target="intro.conformance.and.error.handling"/>).
2722  </t>
2723</x:note>
2724<t>
2725   There are circumstances in which a fragment identifier in a Location URI
2726   would not be appropriate. For instance, when it appears in a 201 Created
2727   response, where the Location header field specifies the URI for the entire
2728   created resource.
2729</t>
2730<x:note>
2731  <t>
2732    <x:h>Note:</x:h> This specification does not define precedence rules
2733    for the case where the original URI, as navigated to by the user
2734    agent, and the Location header field value both contain fragment
2735    identifiers. Thus be aware that including fragment identifiers might
2736    inconvenience anyone relying on the semantics of the original URI's
2737    fragment identifier.
2738  </t>
2739</x:note>
2740<x:note>
2741  <t>
2742    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2743    from Location in that the Content-Location identifies the most specific
2744    resource corresponding to the enclosed representation.
2745    It is therefore possible for a response to contain header fields for
2746    both Location and Content-Location.
2747  </t>
2748</x:note>
2749</section>
2750
2751<section title="Max-Forwards" anchor="header.max-forwards">
2752  <iref primary="true" item="Max-Forwards header field" x:for-anchor=""/>
2753  <iref primary="true" item="Header Fields" subitem="Max-Forwards" x:for-anchor=""/>
2754  <x:anchor-alias value="Max-Forwards"/>
2755<t>
2756   The "Max-Forwards" header field provides a mechanism with the
2757   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2758   methods to limit the number of times that the request is forwarded by
2759   proxies. This can be useful when the client is attempting to
2760   trace a request which appears to be failing or looping mid-chain.
2761</t>
2762<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/>
2763  <x:ref>Max-Forwards</x:ref> = 1*<x:ref>DIGIT</x:ref>
2764</artwork></figure>
2765<t>
2766   The Max-Forwards value is a decimal integer indicating the remaining
2767   number of times this request message can be forwarded.
2768</t>
2769<t>
2770   Each recipient of a TRACE or OPTIONS request
2771   containing a Max-Forwards header field &MUST; check and update its
2772   value prior to forwarding the request. If the received value is zero
2773   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2774   respond as the final recipient. If the received Max-Forwards value is
2775   greater than zero, then the forwarded message &MUST; contain an updated
2776   Max-Forwards field with a value decremented by one (1).
2777</t>
2778<t>
2779   The Max-Forwards header field &MAY; be ignored for all other request
2780   methods.
2781</t>
2782</section>
2783
2784<section title="Referer" anchor="header.referer">
2785  <iref primary="true" item="Referer header field" x:for-anchor=""/>
2786  <iref primary="true" item="Header Fields" subitem="Referer" x:for-anchor=""/>
2787  <x:anchor-alias value="Referer"/>
2788<t>
2789   The "Referer" [sic] header field allows the client to specify the
2790   URI of the resource from which the effective request URI was obtained (the
2791   "referrer", although the header field is misspelled.).
2792</t>
2793<t>
2794   The Referer header field allows servers to generate lists of back-links to
2795   resources for interest, logging, optimized caching, etc. It also allows
2796   obsolete or mistyped links to be traced for maintenance. Some servers use
2797   Referer as a means of controlling where they allow links from (so-called
2798   "deep linking"), but legitimate requests do not always
2799   contain a Referer header field.
2800</t>
2801<t>
2802   If the effective request URI was obtained from a source that does not have its own
2803   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
2804   sent with the value "about:blank", or not be sent at all. Note that this
2805   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2806</t>
2807<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/>
2808  <x:ref>Referer</x:ref> = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2809</artwork></figure>
2810<t>
2811   Example:
2812</t>
2813<figure><artwork type="example">
2814  Referer: http://www.example.org/hypertext/Overview.html
2815</artwork></figure>
2816<t>
2817   If the field value is a relative URI, it &SHOULD; be interpreted
2818   relative to the effective request URI. The URI &MUST-NOT; include a fragment. See
2819   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2820</t>
2821</section>
2822
2823<section title="Retry-After" anchor="header.retry-after">
2824  <iref primary="true" item="Retry-After header field" x:for-anchor=""/>
2825  <iref primary="true" item="Header Fields" subitem="Retry-After" x:for-anchor=""/>
2826  <x:anchor-alias value="Retry-After"/>
2827<t>
2828   The header "Retry-After" field can be used with a 503 (Service
2829   Unavailable) response to indicate how long the service is expected to
2830   be unavailable to the requesting client. This field &MAY; also be used
2831   with any 3xx (Redirection) response to indicate the minimum time the
2832   user-agent is asked to wait before issuing the redirected request.
2833</t>
2834<t>
2835   The value of this field can be either an HTTP-date or an integer number
2836   of seconds (in decimal) after the time of the response.
2837</t>
2838<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/>
2839  <x:ref>Retry-After</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2840</artwork></figure>
2841<t anchor="rule.delta-seconds">
2842  <x:anchor-alias value="delta-seconds"/>
2843   Time spans are non-negative decimal integers, representing time in
2844   seconds.
2845</t>
2846<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2847  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2848</artwork></figure>
2849<t>
2850   Two examples of its use are
2851</t>
2852<figure><artwork type="example">
2853  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2854  Retry-After: 120
2855</artwork></figure>
2856<t>
2857   In the latter example, the delay is 2 minutes.
2858</t>
2859</section>
2860
2861<section title="Server" anchor="header.server">
2862  <iref primary="true" item="Server header field" x:for-anchor=""/>
2863  <iref primary="true" item="Header Fields" subitem="Server" x:for-anchor=""/>
2864  <x:anchor-alias value="Server"/>
2865<t>
2866   The "Server" header field contains information about the
2867   software used by the origin server to handle the request.
2868</t>
2869<t>
2870   The field can contain multiple product tokens (&product-tokens;) and
2871   comments (&header-fields;) identifying the server and any significant
2872   subproducts. The product tokens are listed in order of their significance
2873   for identifying the application.
2874</t>
2875<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/>
2876  <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> ) )
2877</artwork></figure>
2878<t>
2879   Example:
2880</t>
2881<figure><artwork type="example">
2882  Server: CERN/3.0 libwww/2.17
2883</artwork></figure>
2884<t>
2885   If the response is being forwarded through a proxy, the proxy
2886   application &MUST-NOT; modify the Server header field. Instead, it
2887   &MUST; include a Via field (as described in &header-via;).
2888</t>
2889<x:note>
2890  <t>
2891    <x:h>Note:</x:h> Revealing the specific software version of the server might
2892    allow the server machine to become more vulnerable to attacks
2893    against software that is known to contain security holes. Server
2894    implementors are encouraged to make this field a configurable
2895    option.
2896  </t>
2897</x:note>
2898</section>
2899
2900<section title="User-Agent" anchor="header.user-agent">
2901  <iref primary="true" item="User-Agent header field" x:for-anchor=""/>
2902  <iref primary="true" item="Header Fields" subitem="User-Agent" x:for-anchor=""/>
2903  <x:anchor-alias value="User-Agent"/>
2904<t>
2905   The "User-Agent" header field contains information about the user
2906   agent originating the request. User agents &SHOULD; include this field with
2907   requests.
2908</t>
2909<t>
2910   Typically, it is used for statistical purposes, the tracing of protocol
2911   violations, and tailoring responses to avoid particular user agent
2912   limitations.
2913</t>
2914<t>
2915   The field can contain multiple product tokens (&product-tokens;)
2916   and comments (&header-fields;) identifying the agent and its
2917   significant subproducts. By convention, the product tokens are listed in
2918   order of their significance for identifying the application.
2919</t>
2920<t>
2921   Because this field is usually sent on every request a user agent makes,
2922   implementations are encouraged not to include needlessly fine-grained
2923   detail, and to limit (or even prohibit) the addition of subproducts by third
2924   parties. Overly long and detailed User-Agent field values make requests
2925   larger and can also be used to identify ("fingerprint") the user against
2926   their wishes.
2927</t>
2928<t>
2929   Likewise, implementations are encouraged not to use the product tokens of
2930   other implementations in order to declare compatibility with them, as this
2931   circumvents the purpose of the field. Finally, they are encouraged not to
2932   use comments to identify products; doing so makes the field value more
2933   difficult to parse.
2934</t>
2935<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/>
2936  <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> ) )
2937</artwork></figure>
2938<t>
2939   Example:
2940</t>
2941<figure><artwork type="example">
2942  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2943</artwork></figure>
2944</section>
2945
2946</section>
2947
2948<section title="IANA Considerations" anchor="IANA.considerations">
2949
2950<section title="Method Registry" anchor="method.registration">
2951<t>
2952  The registration procedure for HTTP request methods is defined by
2953  <xref target="method.registry"/> of this document.
2954</t>
2955<t>
2956   The HTTP Method Registry shall be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2957   and be populated with the registrations below:
2958</t>
2959<?BEGININC p2-semantics.iana-methods ?>
2960<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2961<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2962   <ttcol>Method</ttcol>
2963   <ttcol>Safe</ttcol>
2964   <ttcol>Reference</ttcol>
2965   <c>CONNECT</c>
2966   <c>no</c>
2967   <c>
2968      <xref target="CONNECT"/>
2969   </c>
2970   <c>DELETE</c>
2971   <c>no</c>
2972   <c>
2973      <xref target="DELETE"/>
2974   </c>
2975   <c>GET</c>
2976   <c>yes</c>
2977   <c>
2978      <xref target="GET"/>
2979   </c>
2980   <c>HEAD</c>
2981   <c>yes</c>
2982   <c>
2983      <xref target="HEAD"/>
2984   </c>
2985   <c>OPTIONS</c>
2986   <c>yes</c>
2987   <c>
2988      <xref target="OPTIONS"/>
2989   </c>
2990   <c>POST</c>
2991   <c>no</c>
2992   <c>
2993      <xref target="POST"/>
2994   </c>
2995   <c>PUT</c>
2996   <c>no</c>
2997   <c>
2998      <xref target="PUT"/>
2999   </c>
3000   <c>TRACE</c>
3001   <c>yes</c>
3002   <c>
3003      <xref target="TRACE"/>
3004   </c>
3005</texttable>
3006<!--(END)-->
3007<?ENDINC p2-semantics.iana-methods ?>
3008</section>
3009
3010<section title="Status Code Registry" anchor="status.code.registration">
3011<t>
3012   The registration procedure for HTTP Status Codes &mdash; previously defined
3013   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> &mdash; is now defined
3014   by <xref target="status.code.registry"/> of this document.
3015</t>
3016<t>
3017   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
3018   shall be updated with the registrations below:
3019</t>
3020<?BEGININC p2-semantics.iana-status-codes ?>
3021<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
3022<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
3023   <ttcol>Value</ttcol>
3024   <ttcol>Description</ttcol>
3025   <ttcol>Reference</ttcol>
3026   <c>100</c>
3027   <c>Continue</c>
3028   <c>
3029      <xref target="status.100"/>
3030   </c>
3031   <c>101</c>
3032   <c>Switching Protocols</c>
3033   <c>
3034      <xref target="status.101"/>
3035   </c>
3036   <c>200</c>
3037   <c>OK</c>
3038   <c>
3039      <xref target="status.200"/>
3040   </c>
3041   <c>201</c>
3042   <c>Created</c>
3043   <c>
3044      <xref target="status.201"/>
3045   </c>
3046   <c>202</c>
3047   <c>Accepted</c>
3048   <c>
3049      <xref target="status.202"/>
3050   </c>
3051   <c>203</c>
3052   <c>Non-Authoritative Information</c>
3053   <c>
3054      <xref target="status.203"/>
3055   </c>
3056   <c>204</c>
3057   <c>No Content</c>
3058   <c>
3059      <xref target="status.204"/>
3060   </c>
3061   <c>205</c>
3062   <c>Reset Content</c>
3063   <c>
3064      <xref target="status.205"/>
3065   </c>
3066   <c>300</c>
3067   <c>Multiple Choices</c>
3068   <c>
3069      <xref target="status.300"/>
3070   </c>
3071   <c>301</c>
3072   <c>Moved Permanently</c>
3073   <c>
3074      <xref target="status.301"/>
3075   </c>
3076   <c>302</c>
3077   <c>Found</c>
3078   <c>
3079      <xref target="status.302"/>
3080   </c>
3081   <c>303</c>
3082   <c>See Other</c>
3083   <c>
3084      <xref target="status.303"/>
3085   </c>
3086   <c>305</c>
3087   <c>Use Proxy</c>
3088   <c>
3089      <xref target="status.305"/>
3090   </c>
3091   <c>306</c>
3092   <c>(Unused)</c>
3093   <c>
3094      <xref target="status.306"/>
3095   </c>
3096   <c>307</c>
3097   <c>Temporary Redirect</c>
3098   <c>
3099      <xref target="status.307"/>
3100   </c>
3101   <c>400</c>
3102   <c>Bad Request</c>
3103   <c>
3104      <xref target="status.400"/>
3105   </c>
3106   <c>402</c>
3107   <c>Payment Required</c>
3108   <c>
3109      <xref target="status.402"/>
3110   </c>
3111   <c>403</c>
3112   <c>Forbidden</c>
3113   <c>
3114      <xref target="status.403"/>
3115   </c>
3116   <c>404</c>
3117   <c>Not Found</c>
3118   <c>
3119      <xref target="status.404"/>
3120   </c>
3121   <c>405</c>
3122   <c>Method Not Allowed</c>
3123   <c>
3124      <xref target="status.405"/>
3125   </c>
3126   <c>406</c>
3127   <c>Not Acceptable</c>
3128   <c>
3129      <xref target="status.406"/>
3130   </c>
3131   <c>407</c>
3132   <c>Proxy Authentication Required</c>
3133   <c>
3134      <xref target="status.407"/>
3135   </c>
3136   <c>408</c>
3137   <c>Request Timeout</c>
3138   <c>
3139      <xref target="status.408"/>
3140   </c>
3141   <c>409</c>
3142   <c>Conflict</c>
3143   <c>
3144      <xref target="status.409"/>
3145   </c>
3146   <c>410</c>
3147   <c>Gone</c>
3148   <c>
3149      <xref target="status.410"/>
3150   </c>
3151   <c>411</c>
3152   <c>Length Required</c>
3153   <c>
3154      <xref target="status.411"/>
3155   </c>
3156   <c>413</c>
3157   <c>Request Representation Too Large</c>
3158   <c>
3159      <xref target="status.413"/>
3160   </c>
3161   <c>414</c>
3162   <c>URI Too Long</c>
3163   <c>
3164      <xref target="status.414"/>
3165   </c>
3166   <c>415</c>
3167   <c>Unsupported Media Type</c>
3168   <c>
3169      <xref target="status.415"/>
3170   </c>
3171   <c>417</c>
3172   <c>Expectation Failed</c>
3173   <c>
3174      <xref target="status.417"/>
3175   </c>
3176   <c>426</c>
3177   <c>Upgrade Required</c>
3178   <c>
3179      <xref target="status.426"/>
3180   </c>
3181   <c>500</c>
3182   <c>Internal Server Error</c>
3183   <c>
3184      <xref target="status.500"/>
3185   </c>
3186   <c>501</c>
3187   <c>Not Implemented</c>
3188   <c>
3189      <xref target="status.501"/>
3190   </c>
3191   <c>502</c>
3192   <c>Bad Gateway</c>
3193   <c>
3194      <xref target="status.502"/>
3195   </c>
3196   <c>503</c>
3197   <c>Service Unavailable</c>
3198   <c>
3199      <xref target="status.503"/>
3200   </c>
3201   <c>504</c>
3202   <c>Gateway Timeout</c>
3203   <c>
3204      <xref target="status.504"/>
3205   </c>
3206   <c>505</c>
3207   <c>HTTP Version Not Supported</c>
3208   <c>
3209      <xref target="status.505"/>
3210   </c>
3211</texttable>
3212<!--(END)-->
3213<?ENDINC p2-semantics.iana-status-codes ?>
3214</section>
3215<section title="Header Field Registration" anchor="header.field.registration">
3216<t>
3217   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
3218   with the permanent registrations below (see <xref target="RFC3864"/>):
3219</t>
3220<?BEGININC p2-semantics.iana-headers ?>
3221<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
3222<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
3223   <ttcol>Header Field Name</ttcol>
3224   <ttcol>Protocol</ttcol>
3225   <ttcol>Status</ttcol>
3226   <ttcol>Reference</ttcol>
3227
3228   <c>Allow</c>
3229   <c>http</c>
3230   <c>standard</c>
3231   <c>
3232      <xref target="header.allow"/>
3233   </c>
3234   <c>Date</c>
3235   <c>http</c>
3236   <c>standard</c>
3237   <c>
3238      <xref target="header.date"/>
3239   </c>
3240   <c>Expect</c>
3241   <c>http</c>
3242   <c>standard</c>
3243   <c>
3244      <xref target="header.expect"/>
3245   </c>
3246   <c>From</c>
3247   <c>http</c>
3248   <c>standard</c>
3249   <c>
3250      <xref target="header.from"/>
3251   </c>
3252   <c>Location</c>
3253   <c>http</c>
3254   <c>standard</c>
3255   <c>
3256      <xref target="header.location"/>
3257   </c>
3258   <c>Max-Forwards</c>
3259   <c>http</c>
3260   <c>standard</c>
3261   <c>
3262      <xref target="header.max-forwards"/>
3263   </c>
3264   <c>Referer</c>
3265   <c>http</c>
3266   <c>standard</c>
3267   <c>
3268      <xref target="header.referer"/>
3269   </c>
3270   <c>Retry-After</c>
3271   <c>http</c>
3272   <c>standard</c>
3273   <c>
3274      <xref target="header.retry-after"/>
3275   </c>
3276   <c>Server</c>
3277   <c>http</c>
3278   <c>standard</c>
3279   <c>
3280      <xref target="header.server"/>
3281   </c>
3282   <c>User-Agent</c>
3283   <c>http</c>
3284   <c>standard</c>
3285   <c>
3286      <xref target="header.user-agent"/>
3287   </c>
3288</texttable>
3289<!--(END)-->
3290<?ENDINC p2-semantics.iana-headers ?>
3291<t>
3292   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
3293</t>
3294</section>
3295</section>
3296
3297<section title="Security Considerations" anchor="security.considerations">
3298<t>
3299   This section is meant to inform application developers, information
3300   providers, and users of the security limitations in HTTP/1.1 as
3301   described by this document. The discussion does not include
3302   definitive solutions to the problems revealed, though it does make
3303   some suggestions for reducing security risks.
3304</t>
3305
3306<section title="Transfer of Sensitive Information" anchor="security.sensitive">
3307<t>
3308   Like any generic data transfer protocol, HTTP cannot regulate the
3309   content of the data that is transferred, nor is there any a priori
3310   method of determining the sensitivity of any particular piece of
3311   information within the context of any given request. Therefore,
3312   applications &SHOULD; supply as much control over this information as
3313   possible to the provider of that information. Four header fields are
3314   worth special mention in this context: Server, Via, Referer and From.
3315</t>
3316<t>
3317   Revealing the specific software version of the server might allow the
3318   server machine to become more vulnerable to attacks against software
3319   that is known to contain security holes. Implementors &SHOULD; make the
3320   Server header field a configurable option.
3321</t>
3322<t>
3323   Proxies which serve as a portal through a network firewall &SHOULD;
3324   take special precautions regarding the transfer of header information
3325   that identifies the hosts behind the firewall. In particular, they
3326   &SHOULD; remove, or replace with sanitized versions, any Via fields
3327   generated behind the firewall.
3328</t>
3329<t>
3330   The Referer header field allows reading patterns to be studied and reverse
3331   links drawn. Although it can be very useful, its power can be abused
3332   if user details are not separated from the information contained in
3333   the Referer. Even when the personal information has been removed, the
3334   Referer header field might indicate a private document's URI whose
3335   publication would be inappropriate.
3336</t>
3337<t>
3338   The information sent in the From field might conflict with the user's
3339   privacy interests or their site's security policy, and hence it
3340   &SHOULD-NOT;  be transmitted without the user being able to disable,
3341   enable, and modify the contents of the field. The user &MUST; be able
3342   to set the contents of this field within a user preference or
3343   application defaults configuration.
3344</t>
3345<t>
3346   We suggest, though do not require, that a convenient toggle interface
3347   be provided for the user to enable or disable the sending of From and
3348   Referer information.
3349</t>
3350<t>
3351   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref
3352   target="header.server"/>) header fields can sometimes be used to determine
3353   that a specific client or server has a particular security hole which might
3354   be exploited. Unfortunately, this same information is often used for other
3355   valuable purposes for which HTTP currently has no better mechanism.
3356</t>
3357<t>
3358   Furthermore, the User-Agent header field may contain enough entropy to be
3359   used, possibly in conjunction with other material, to uniquely identify the
3360   user.
3361</t>
3362<t>
3363   Some request methods, like TRACE (<xref target="TRACE"/>), expose information
3364   that was sent in request header fields within the body of their response.
3365   Clients &SHOULD; be careful with sensitive information, like Cookies,
3366   Authorization credentials, and other header fields that might be used to
3367   collect data from the client.
3368</t> 
3369</section>
3370
3371<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
3372<t>
3373   Because the source of a link might be private information or might
3374   reveal an otherwise private information source, it is strongly
3375   recommended that the user be able to select whether or not the
3376   Referer field is sent. For example, a browser client could have a
3377   toggle switch for browsing openly/anonymously, which would
3378   respectively enable/disable the sending of Referer and From
3379   information.
3380</t>
3381<t>
3382   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
3383   HTTP request if the referring page was transferred with a secure
3384   protocol.
3385</t>
3386<t>
3387   Authors of services &SHOULD-NOT; use GET-based forms for the submission of
3388   sensitive data because that data will be placed in the request-target. Many
3389   existing servers, proxies, and user agents log or display the request-target
3390   in places where it might be visible to third parties. Such services can
3391   use POST-based form submission instead.
3392</t>
3393</section>
3394
3395<section title="Location Headers and Spoofing" anchor="location.spoofing">
3396<t>
3397   If a single server supports multiple organizations that do not trust
3398   one another, then it &MUST; check the values of Location and Content-Location
3399   header fields in responses that are generated under control of
3400   said organizations to make sure that they do not attempt to
3401   invalidate resources over which they have no authority.
3402</t>
3403</section>
3404
3405<section title="Security Considerations for CONNECT">
3406<t>
3407   Since tunneled data is opaque to the proxy, there are additional
3408   risks to tunneling to other well-known or reserved ports.
3409   A HTTP client CONNECTing to port 25 could relay spam
3410   via SMTP, for example. As such, proxies &SHOULD; restrict CONNECT
3411   access to a small number of known ports.
3412</t>
3413</section>
3414
3415</section>
3416
3417<section title="Acknowledgments" anchor="acks">
3418<t>
3419  See &acks;.
3420</t>
3421</section>
3422</middle>
3423<back>
3424
3425<references title="Normative References">
3426
3427<reference anchor="Part1">
3428  <front>
3429    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
3430    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3431      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3432      <address><email>fielding@gbiv.com</email></address>
3433    </author>
3434    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3435      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3436      <address><email>jg@freedesktop.org</email></address>
3437    </author>
3438    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3439      <organization abbrev="HP">Hewlett-Packard Company</organization>
3440      <address><email>JeffMogul@acm.org</email></address>
3441    </author>
3442    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3443      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3444      <address><email>henrikn@microsoft.com</email></address>
3445    </author>
3446    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3447      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3448      <address><email>LMM@acm.org</email></address>
3449    </author>
3450    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3451      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3452      <address><email>paulle@microsoft.com</email></address>
3453    </author>
3454    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3455      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3456      <address><email>timbl@w3.org</email></address>
3457    </author>
3458    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3459      <organization abbrev="W3C">World Wide Web Consortium</organization>
3460      <address><email>ylafon@w3.org</email></address>
3461    </author>
3462    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3463      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3464      <address><email>julian.reschke@greenbytes.de</email></address>
3465    </author>
3466    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3467  </front>
3468  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
3469  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
3470</reference>
3471
3472<reference anchor="Part3">
3473  <front>
3474    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
3475    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3476      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3477      <address><email>fielding@gbiv.com</email></address>
3478    </author>
3479    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3480      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3481      <address><email>jg@freedesktop.org</email></address>
3482    </author>
3483    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3484      <organization abbrev="HP">Hewlett-Packard Company</organization>
3485      <address><email>JeffMogul@acm.org</email></address>
3486    </author>
3487    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3488      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3489      <address><email>henrikn@microsoft.com</email></address>
3490    </author>
3491    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3492      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3493      <address><email>LMM@acm.org</email></address>
3494    </author>
3495    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3496      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3497      <address><email>paulle@microsoft.com</email></address>
3498    </author>
3499    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3500      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3501      <address><email>timbl@w3.org</email></address>
3502    </author>
3503    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3504      <organization abbrev="W3C">World Wide Web Consortium</organization>
3505      <address><email>ylafon@w3.org</email></address>
3506    </author>
3507    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3508      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3509      <address><email>julian.reschke@greenbytes.de</email></address>
3510    </author>
3511    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3512  </front>
3513  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
3514  <x:source href="p3-payload.xml" basename="p3-payload"/>
3515</reference>
3516
3517<reference anchor="Part4">
3518  <front>
3519    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
3520    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3521      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3522      <address><email>fielding@gbiv.com</email></address>
3523    </author>
3524    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3525      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3526      <address><email>jg@freedesktop.org</email></address>
3527    </author>
3528    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3529      <organization abbrev="HP">Hewlett-Packard Company</organization>
3530      <address><email>JeffMogul@acm.org</email></address>
3531    </author>
3532    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3533      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3534      <address><email>henrikn@microsoft.com</email></address>
3535    </author>
3536    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3537      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3538      <address><email>LMM@acm.org</email></address>
3539    </author>
3540    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3541      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3542      <address><email>paulle@microsoft.com</email></address>
3543    </author>
3544    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3545      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3546      <address><email>timbl@w3.org</email></address>
3547    </author>
3548    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3549      <organization abbrev="W3C">World Wide Web Consortium</organization>
3550      <address><email>ylafon@w3.org</email></address>
3551    </author>
3552    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3553      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3554      <address><email>julian.reschke@greenbytes.de</email></address>
3555    </author>
3556    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3557  </front>
3558  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
3559  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
3560</reference>
3561
3562<reference anchor="Part5">
3563  <front>
3564    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
3565    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3566      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3567      <address><email>fielding@gbiv.com</email></address>
3568    </author>
3569    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3570      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3571      <address><email>jg@freedesktop.org</email></address>
3572    </author>
3573    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3574      <organization abbrev="HP">Hewlett-Packard Company</organization>
3575      <address><email>JeffMogul@acm.org</email></address>
3576    </author>
3577    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3578      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3579      <address><email>henrikn@microsoft.com</email></address>
3580    </author>
3581    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3582      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3583      <address><email>LMM@acm.org</email></address>
3584    </author>
3585    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3586      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3587      <address><email>paulle@microsoft.com</email></address>
3588    </author>
3589    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3590      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3591      <address><email>timbl@w3.org</email></address>
3592    </author>
3593    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3594      <organization abbrev="W3C">World Wide Web Consortium</organization>
3595      <address><email>ylafon@w3.org</email></address>
3596    </author>
3597    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3598      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3599      <address><email>julian.reschke@greenbytes.de</email></address>
3600    </author>
3601    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3602  </front>
3603  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
3604  <x:source href="p5-range.xml" basename="p5-range"/>
3605</reference>
3606
3607<reference anchor="Part6">
3608  <front>
3609    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
3610    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3611      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3612      <address><email>fielding@gbiv.com</email></address>
3613    </author>
3614    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3615      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3616      <address><email>jg@freedesktop.org</email></address>
3617    </author>
3618    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3619      <organization abbrev="HP">Hewlett-Packard Company</organization>
3620      <address><email>JeffMogul@acm.org</email></address>
3621    </author>
3622    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3623      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3624      <address><email>henrikn@microsoft.com</email></address>
3625    </author>
3626    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3627      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3628      <address><email>LMM@acm.org</email></address>
3629    </author>
3630    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3631      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3632      <address><email>paulle@microsoft.com</email></address>
3633    </author>
3634    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3635      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3636      <address><email>timbl@w3.org</email></address>
3637    </author>
3638    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3639      <organization abbrev="W3C">World Wide Web Consortium</organization>
3640      <address><email>ylafon@w3.org</email></address>
3641    </author>
3642    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
3643      <organization>Rackspace</organization>
3644      <address><email>mnot@mnot.net</email></address>
3645    </author>
3646    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3647      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3648      <address><email>julian.reschke@greenbytes.de</email></address>
3649    </author>
3650    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3651  </front>
3652  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
3653  <x:source href="p6-cache.xml" basename="p6-cache"/>
3654</reference>
3655
3656<reference anchor="Part7">
3657  <front>
3658    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
3659    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3660      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3661      <address><email>fielding@gbiv.com</email></address>
3662    </author>
3663    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3664      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3665      <address><email>jg@freedesktop.org</email></address>
3666    </author>
3667    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3668      <organization abbrev="HP">Hewlett-Packard Company</organization>
3669      <address><email>JeffMogul@acm.org</email></address>
3670    </author>
3671    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3672      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3673      <address><email>henrikn@microsoft.com</email></address>
3674    </author>
3675    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3676      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3677      <address><email>LMM@acm.org</email></address>
3678    </author>
3679    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3680      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3681      <address><email>paulle@microsoft.com</email></address>
3682    </author>
3683    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3684      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3685      <address><email>timbl@w3.org</email></address>
3686    </author>
3687    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3688      <organization abbrev="W3C">World Wide Web Consortium</organization>
3689      <address><email>ylafon@w3.org</email></address>
3690    </author>
3691    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3692      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3693      <address><email>julian.reschke@greenbytes.de</email></address>
3694    </author>
3695    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3696  </front>
3697  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3698  <x:source href="p7-auth.xml" basename="p7-auth"/>
3699</reference>
3700
3701<reference anchor="RFC2119">
3702  <front>
3703    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3704    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3705      <organization>Harvard University</organization>
3706      <address><email>sob@harvard.edu</email></address>
3707    </author>
3708    <date month="March" year="1997"/>
3709  </front>
3710  <seriesInfo name="BCP" value="14"/>
3711  <seriesInfo name="RFC" value="2119"/>
3712</reference>
3713
3714<reference anchor="RFC3986">
3715 <front>
3716  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3717  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3718    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3719    <address>
3720       <email>timbl@w3.org</email>
3721       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3722    </address>
3723  </author>
3724  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3725    <organization abbrev="Day Software">Day Software</organization>
3726    <address>
3727      <email>fielding@gbiv.com</email>
3728      <uri>http://roy.gbiv.com/</uri>
3729    </address>
3730  </author>
3731  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3732    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3733    <address>
3734      <email>LMM@acm.org</email>
3735      <uri>http://larry.masinter.net/</uri>
3736    </address>
3737  </author>
3738  <date month='January' year='2005'></date>
3739 </front>
3740 <seriesInfo name="STD" value="66"/>
3741 <seriesInfo name="RFC" value="3986"/>
3742</reference>
3743
3744<reference anchor="RFC5234">
3745  <front>
3746    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3747    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3748      <organization>Brandenburg InternetWorking</organization>
3749      <address>
3750        <email>dcrocker@bbiw.net</email>
3751      </address> 
3752    </author>
3753    <author initials="P." surname="Overell" fullname="Paul Overell">
3754      <organization>THUS plc.</organization>
3755      <address>
3756        <email>paul.overell@thus.net</email>
3757      </address>
3758    </author>
3759    <date month="January" year="2008"/>
3760  </front>
3761  <seriesInfo name="STD" value="68"/>
3762  <seriesInfo name="RFC" value="5234"/>
3763</reference>
3764
3765</references>
3766
3767<references title="Informative References">
3768
3769<reference anchor="RFC1123">
3770  <front>
3771    <title>Requirements for Internet Hosts - Application and Support</title>
3772    <author initials="R." surname="Braden" fullname="Robert Braden">
3773      <organization>University of Southern California (USC), Information Sciences Institute</organization>
3774      <address><email>Braden@ISI.EDU</email></address>
3775    </author>
3776    <date month="October" year="1989"/>
3777  </front>
3778  <seriesInfo name="STD" value="3"/>
3779  <seriesInfo name="RFC" value="1123"/>
3780</reference>
3781
3782<reference anchor="RFC1945">
3783  <front>
3784    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3785    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3786      <organization>MIT, Laboratory for Computer Science</organization>
3787      <address><email>timbl@w3.org</email></address>
3788    </author>
3789    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3790      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3791      <address><email>fielding@ics.uci.edu</email></address>
3792    </author>
3793    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3794      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3795      <address><email>frystyk@w3.org</email></address>
3796    </author>
3797    <date month="May" year="1996"/>
3798  </front>
3799  <seriesInfo name="RFC" value="1945"/>
3800</reference>
3801
3802<reference anchor="RFC2068">
3803  <front>
3804    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3805    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3806      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3807      <address><email>fielding@ics.uci.edu</email></address>
3808    </author>
3809    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3810      <organization>MIT Laboratory for Computer Science</organization>
3811      <address><email>jg@w3.org</email></address>
3812    </author>
3813    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3814      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3815      <address><email>mogul@wrl.dec.com</email></address>
3816    </author>
3817    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3818      <organization>MIT Laboratory for Computer Science</organization>
3819      <address><email>frystyk@w3.org</email></address>
3820    </author>
3821    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3822      <organization>MIT Laboratory for Computer Science</organization>
3823      <address><email>timbl@w3.org</email></address>
3824    </author>
3825    <date month="January" year="1997"/>
3826  </front>
3827  <seriesInfo name="RFC" value="2068"/>
3828</reference>
3829
3830<reference anchor="RFC2616">
3831  <front>
3832    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3833    <author initials="R." surname="Fielding" fullname="R. Fielding">
3834      <organization>University of California, Irvine</organization>
3835      <address><email>fielding@ics.uci.edu</email></address>
3836    </author>
3837    <author initials="J." surname="Gettys" fullname="J. Gettys">
3838      <organization>W3C</organization>
3839      <address><email>jg@w3.org</email></address>
3840    </author>
3841    <author initials="J." surname="Mogul" fullname="J. Mogul">
3842      <organization>Compaq Computer Corporation</organization>
3843      <address><email>mogul@wrl.dec.com</email></address>
3844    </author>
3845    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3846      <organization>MIT Laboratory for Computer Science</organization>
3847      <address><email>frystyk@w3.org</email></address>
3848    </author>
3849    <author initials="L." surname="Masinter" fullname="L. Masinter">
3850      <organization>Xerox Corporation</organization>
3851      <address><email>masinter@parc.xerox.com</email></address>
3852    </author>
3853    <author initials="P." surname="Leach" fullname="P. Leach">
3854      <organization>Microsoft Corporation</organization>
3855      <address><email>paulle@microsoft.com</email></address>
3856    </author>
3857    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3858      <organization>W3C</organization>
3859      <address><email>timbl@w3.org</email></address>
3860    </author>
3861    <date month="June" year="1999"/>
3862  </front>
3863  <seriesInfo name="RFC" value="2616"/>
3864</reference>
3865
3866<reference anchor='RFC2817'>
3867  <front>
3868    <title>Upgrading to TLS Within HTTP/1.1</title>
3869    <author initials='R.' surname='Khare' fullname='R. Khare'>
3870      <organization>4K Associates / UC Irvine</organization>
3871      <address><email>rohit@4K-associates.com</email></address>
3872    </author>
3873    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3874      <organization>Agranat Systems, Inc.</organization>
3875      <address><email>lawrence@agranat.com</email></address>
3876    </author>
3877    <date year='2000' month='May' />
3878  </front>
3879  <seriesInfo name='RFC' value='2817' />
3880</reference>
3881
3882<reference anchor='RFC3864'>
3883  <front>
3884    <title>Registration Procedures for Message Header Fields</title>
3885    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3886      <organization>Nine by Nine</organization>
3887      <address><email>GK-IETF@ninebynine.org</email></address>
3888    </author>
3889    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3890      <organization>BEA Systems</organization>
3891      <address><email>mnot@pobox.com</email></address>
3892    </author>
3893    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3894      <organization>HP Labs</organization>
3895      <address><email>JeffMogul@acm.org</email></address>
3896    </author>
3897    <date year='2004' month='September' />
3898  </front>
3899  <seriesInfo name='BCP' value='90' />
3900  <seriesInfo name='RFC' value='3864' />
3901</reference>
3902
3903<reference anchor='RFC5226'>
3904  <front>
3905    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3906    <author initials='T.' surname='Narten' fullname='T. Narten'>
3907      <organization>IBM</organization>
3908      <address><email>narten@us.ibm.com</email></address>
3909    </author>
3910    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3911      <organization>Google</organization>
3912      <address><email>Harald@Alvestrand.no</email></address>
3913    </author>
3914    <date year='2008' month='May' />
3915  </front>
3916  <seriesInfo name='BCP' value='26' />
3917  <seriesInfo name='RFC' value='5226' />
3918</reference>
3919
3920<reference anchor="RFC5322">
3921  <front>
3922    <title>Internet Message Format</title>
3923    <author initials="P." surname="Resnick" fullname="P. Resnick">
3924      <organization>Qualcomm Incorporated</organization>
3925    </author>
3926    <date year="2008" month="October"/>
3927  </front> 
3928  <seriesInfo name="RFC" value="5322"/>
3929</reference>
3930
3931<reference anchor='RFC5789'>
3932  <front>
3933    <title>PATCH Method for HTTP</title>
3934    <author initials='L.' surname='Dusseault' fullname='L. Dusseault'>
3935      <organization>Linden Lab</organization>
3936    </author>
3937    <author initials='J.' surname='Snell' fullname='J. Snell' />
3938    <date year='2010' month='March' />
3939  </front>
3940  <seriesInfo name='RFC' value='5789' />
3941</reference>
3942
3943<reference anchor="RFC5987">
3944        <front>
3945    <title>Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters</title>
3946    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke">
3947      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3948      <address>
3949        <postal>
3950          <street>Hafenweg 16</street>
3951          <city>Muenster</city><region>NW</region><code>48155</code>
3952          <country>Germany</country>
3953        </postal>
3954        <email>julian.reschke@greenbytes.de</email>     
3955        <uri>http://greenbytes.de/tech/webdav/</uri>   
3956      </address>
3957    </author>
3958    <date month="August" year="2010"/>
3959  </front>
3960  <seriesInfo name="RFC" value="5987"/>
3961</reference>
3962
3963</references>
3964
3965<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3966<t>
3967  This document takes over the Status Code Registry, previously defined
3968  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3969  (<xref target="status.code.registry"/>)
3970</t>
3971<t>
3972  Clarify definition of POST.
3973  (<xref target="POST"/>)
3974</t>
3975<t>
3976  Remove requirement to handle all Content-* header fields; ban use of
3977  Content-Range with PUT.
3978  (<xref target="PUT"/>)
3979</t>
3980<t>
3981  Take over definition of CONNECT method from <xref target="RFC2817"/>.
3982  (<xref target="CONNECT"/>)
3983</t>
3984<t>
3985  Broadened the definition of 203 (Non-Authoritative Information) to include
3986  cases of payload transformations as well.
3987  (<xref target="status.203"/>)
3988</t>
3989<t>
3990  Failed to consider that there are many other request methods that are safe
3991  to automatically redirect, and further that the user agent is able to make
3992  that determination based on the request method semantics.
3993  Furthermore, allow user agents to rewrite the method from POST to GET
3994  for status codes 301 and 302.
3995  (Sections <xref format="counter" target="status.301"/>,
3996  <xref format="counter" target="status.302"/> and
3997  <xref format="counter" target="status.307"/>)
3998</t>
3999<t>
4000  Deprecate 305 Use Proxy status code, because user agents did not implement it.
4001  It used to indicate that the target resource must be accessed through the
4002  proxy given by the Location field. The Location field gave the URI of the
4003  proxy. The recipient was expected to repeat this single request via the proxy.
4004  (<xref target="status.305"/>)
4005</t>
4006<t>
4007  Define status 426 (Upgrade Required) (this was incorporated from
4008  <xref target="RFC2817"/>).
4009  (<xref target="status.426"/>)
4010</t>
4011<t>
4012  Change ABNF productions for header fields to only define the field value.
4013  (<xref target="header.field.definitions"/>)
4014</t>
4015<t>
4016  Reclassify "Allow" as response header field, removing the option to
4017  specify it in a PUT request.
4018  Relax the server requirement on the contents of the Allow header field and
4019  remove requirement on clients to always trust the header field value.
4020  (<xref target="header.allow"/>)
4021</t>
4022<t>
4023  The ABNF for the Expect header field has been both fixed (allowing parameters
4024  for value-less expectations as well) and simplified (allowing trailing
4025  semicolons after "100-continue" when they were invalid before).
4026  (<xref target="header.expect"/>)
4027</t>
4028<t>
4029  Correct syntax of Location header field to allow URI references (including
4030  relative references and fragments), as referred symbol "absoluteURI" wasn't
4031  what was expected, and add some clarifications as to when use of fragments
4032  would not be appropriate.
4033  (<xref target="header.location"/>)
4034</t>
4035<t>
4036  Restrict Max-Forwards header field to OPTIONS and TRACE (previously,
4037  extension methods could have used it as well).
4038  (<xref target="header.max-forwards"/>)
4039</t>
4040<t>
4041  Allow Referer field value of "about:blank" as alternative to not specifying it.
4042  (<xref target="header.referer"/>)
4043</t>
4044<t>
4045  In the description of the Server header field, the Via field
4046  was described as a SHOULD. The requirement was and is stated
4047  correctly in the description of the Via header field in &header-via;.
4048  (<xref target="header.server"/>)
4049</t>
4050</section>
4051
4052<?BEGININC p2-semantics.abnf-appendix ?>
4053<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
4054<figure>
4055<artwork type="abnf" name="p2-semantics.parsed-abnf">
4056<x:ref>Allow</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
4057
4058<x:ref>BWS</x:ref> = &lt;BWS, defined in [Part1], Section 1.2.2&gt;
4059
4060<x:ref>Date</x:ref> = HTTP-date
4061
4062<x:ref>Expect</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
4063
4064<x:ref>From</x:ref> = mailbox
4065
4066<x:ref>GMT</x:ref> = %x47.4D.54 ; GMT
4067
4068<x:ref>HTTP-date</x:ref> = rfc1123-date / obs-date
4069
4070<x:ref>Location</x:ref> = URI-reference
4071
4072<x:ref>Max-Forwards</x:ref> = 1*DIGIT
4073<x:ref>Method</x:ref> = token
4074
4075<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
4076
4077<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
4078<x:ref>Reason-Phrase</x:ref> = *( HTAB / SP / VCHAR / obs-text )
4079<x:ref>Referer</x:ref> = absolute-URI / partial-URI
4080<x:ref>Retry-After</x:ref> = HTTP-date / delta-seconds
4081
4082<x:ref>Server</x:ref> = product *( RWS ( product / comment ) )
4083<x:ref>Status-Code</x:ref> = 3DIGIT
4084
4085<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.7&gt;
4086<x:ref>User-Agent</x:ref> = product *( RWS ( product / comment ) )
4087
4088<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.7&gt;
4089<x:ref>asctime-date</x:ref> = day-name SP date3 SP time-of-day SP year
4090
4091<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2.3&gt;
4092
4093<x:ref>date1</x:ref> = day SP month SP year
4094<x:ref>date2</x:ref> = day "-" month "-" 2DIGIT
4095<x:ref>date3</x:ref> = month SP ( 2DIGIT / ( SP DIGIT ) )
4096<x:ref>day</x:ref> = 2DIGIT
4097<x:ref>day-name</x:ref> = %x4D.6F.6E ; Mon
4098 / %x54.75.65 ; Tue
4099 / %x57.65.64 ; Wed
4100 / %x54.68.75 ; Thu
4101 / %x46.72.69 ; Fri
4102 / %x53.61.74 ; Sat
4103 / %x53.75.6E ; Sun
4104<x:ref>day-name-l</x:ref> = %x4D.6F.6E.64.61.79 ; Monday
4105 / %x54.75.65.73.64.61.79 ; Tuesday
4106 / %x57.65.64.6E.65.73.64.61.79 ; Wednesday
4107 / %x54.68.75.72.73.64.61.79 ; Thursday
4108 / %x46.72.69.64.61.79 ; Friday
4109 / %x53.61.74.75.72.64.61.79 ; Saturday
4110 / %x53.75.6E.64.61.79 ; Sunday
4111<x:ref>delta-seconds</x:ref> = 1*DIGIT
4112
4113<x:ref>expect-name</x:ref> = token
4114<x:ref>expect-param</x:ref> = expect-name [ BWS "=" BWS expect-value ]
4115<x:ref>expect-value</x:ref> = token / quoted-string
4116<x:ref>expectation</x:ref> = expect-name [ BWS "=" BWS expect-value ] *( OWS ";" [
4117 OWS expect-param ] )
4118
4119<x:ref>hour</x:ref> = 2DIGIT
4120
4121<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
4122<x:ref>minute</x:ref> = 2DIGIT
4123<x:ref>month</x:ref> = %x4A.61.6E ; Jan
4124 / %x46.65.62 ; Feb
4125 / %x4D.61.72 ; Mar
4126 / %x41.70.72 ; Apr
4127 / %x4D.61.79 ; May
4128 / %x4A.75.6E ; Jun
4129 / %x4A.75.6C ; Jul
4130 / %x41.75.67 ; Aug
4131 / %x53.65.70 ; Sep
4132 / %x4F.63.74 ; Oct
4133 / %x4E.6F.76 ; Nov
4134 / %x44.65.63 ; Dec
4135
4136<x:ref>obs-date</x:ref> = rfc850-date / asctime-date
4137<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
4138
4139<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.7&gt;
4140<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 5.2&gt;
4141
4142<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 3.2.3&gt;
4143
4144<x:ref>rfc1123-date</x:ref> = day-name "," SP date1 SP time-of-day SP GMT
4145<x:ref>rfc850-date</x:ref> = day-name-l "," SP date2 SP time-of-day SP GMT
4146
4147<x:ref>second</x:ref> = 2DIGIT
4148
4149<x:ref>time-of-day</x:ref> = hour ":" minute ":" second
4150<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 3.2.3&gt;
4151
4152<x:ref>year</x:ref> = 4DIGIT
4153</artwork>
4154</figure>
4155<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
4156; Allow defined but not used
4157; Date defined but not used
4158; Expect defined but not used
4159; From defined but not used
4160; Location defined but not used
4161; Max-Forwards defined but not used
4162; Reason-Phrase defined but not used
4163; Referer defined but not used
4164; Retry-After defined but not used
4165; Server defined but not used
4166; Status-Code defined but not used
4167; User-Agent defined but not used
4168</artwork></figure></section>
4169<?ENDINC p2-semantics.abnf-appendix ?>
4170
4171<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
4172
4173<section title="Since RFC 2616">
4174<t>
4175  Extracted relevant partitions from <xref target="RFC2616"/>.
4176</t>
4177</section>
4178
4179<section title="Since draft-ietf-httpbis-p2-semantics-00">
4180<t>
4181  Closed issues:
4182  <list style="symbols"> 
4183    <t>
4184      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
4185      "Via is a MUST"
4186      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
4187    </t>
4188    <t>
4189      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
4190      "Fragments allowed in Location"
4191      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
4192    </t>
4193    <t>
4194      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
4195      "Safe Methods vs Redirection"
4196      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
4197    </t>
4198    <t>
4199      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
4200      "Revise description of the POST method"
4201      (<eref target="http://purl.org/NET/http-errata#post"/>)
4202    </t>
4203    <t>
4204      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
4205      "Normative and Informative references"
4206    </t>
4207    <t>
4208      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
4209      "RFC2606 Compliance"
4210    </t>
4211    <t>
4212      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
4213      "Informative references"
4214    </t>
4215    <t>
4216      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
4217      "Redundant cross-references"
4218    </t>
4219  </list>
4220</t>
4221<t>
4222  Other changes:
4223  <list style="symbols"> 
4224    <t>
4225      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
4226    </t>
4227  </list>
4228</t>
4229</section>
4230
4231<section title="Since draft-ietf-httpbis-p2-semantics-01">
4232<t>
4233  Closed issues:
4234  <list style="symbols"> 
4235    <t>
4236      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
4237      "PUT side effects"
4238    </t>
4239    <t>
4240      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
4241      "Duplicate Host header requirements"
4242    </t>
4243  </list>
4244</t>
4245<t>
4246  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4247  <list style="symbols"> 
4248    <t>
4249      Move "Product Tokens" section (back) into Part 1, as "token" is used
4250      in the definition of the Upgrade header field.
4251    </t>
4252    <t>
4253      Add explicit references to BNF syntax and rules imported from other parts of the specification.
4254    </t>
4255    <t>
4256      Copy definition of delta-seconds from Part6 instead of referencing it.
4257    </t>
4258  </list>
4259</t>
4260</section>
4261
4262<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
4263<t>
4264  Closed issues:
4265  <list style="symbols"> 
4266    <t>
4267      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
4268      "Requiring Allow in 405 responses"
4269    </t>
4270    <t>
4271      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
4272      "Status Code Registry"
4273    </t>
4274    <t>
4275      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
4276      "Redirection vs. Location"
4277    </t>
4278    <t>
4279      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
4280      "Cacheability of 303 response"
4281    </t>
4282    <t>
4283      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
4284      "305 Use Proxy"
4285    </t>
4286    <t>
4287      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
4288      "Classification for Allow header"
4289    </t>
4290    <t>
4291      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
4292      "PUT - 'store under' vs 'store at'"
4293    </t>
4294  </list>
4295</t>
4296<t>
4297  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
4298  <list style="symbols"> 
4299    <t>
4300      Reference RFC 3984, and update header field registrations for headers defined
4301      in this document.
4302    </t>
4303  </list>
4304</t>
4305<t>
4306  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4307  <list style="symbols"> 
4308    <t>
4309      Replace string literals when the string really is case-sensitive (method).
4310    </t>
4311  </list>
4312</t>
4313</section>
4314
4315<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
4316<t>
4317  Closed issues:
4318  <list style="symbols"> 
4319    <t>
4320      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
4321      "OPTIONS request bodies"
4322    </t>
4323    <t>
4324      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
4325      "Description of CONNECT should refer to RFC2817"
4326    </t>
4327    <t>
4328      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
4329      "Location Content-Location reference request/response mixup"
4330    </t>
4331  </list>
4332</t>
4333<t>
4334  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
4335  <list style="symbols"> 
4336    <t>
4337      Added initial proposal for registration process, plus initial
4338      content (non-HTTP/1.1 methods to be added by a separate specification).
4339    </t>
4340  </list>
4341</t>
4342</section>
4343
4344<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
4345<t>
4346  Closed issues:
4347  <list style="symbols"> 
4348    <t>
4349      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
4350      "Content-*"
4351    </t>
4352    <t>
4353      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
4354      "RFC 2822 is updated by RFC 5322"
4355    </t>
4356  </list>
4357</t>
4358<t>
4359  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4360  <list style="symbols"> 
4361    <t>
4362      Use "/" instead of "|" for alternatives.
4363    </t>
4364    <t>
4365      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
4366      whitespace ("OWS") and required whitespace ("RWS").
4367    </t>
4368    <t>
4369      Rewrite ABNFs to spell out whitespace rules, factor out
4370      header field value format definitions.
4371    </t>
4372  </list>
4373</t>
4374</section>
4375
4376<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
4377<t>
4378  Closed issues:
4379  <list style="symbols"> 
4380    <t>
4381      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
4382      "Reason-Phrase BNF"
4383    </t>
4384  </list>
4385</t>
4386<t>
4387  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4388  <list style="symbols"> 
4389    <t>
4390      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
4391    </t>
4392  </list>
4393</t>
4394</section>
4395
4396<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
4397<t>
4398  Closed issues:
4399  <list style="symbols"> 
4400    <t>
4401      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
4402      "Clarify when Referer is sent"
4403    </t>
4404    <t>
4405      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
4406      "status codes vs methods"
4407    </t>
4408    <t>
4409      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
4410      "Do not require "updates" relation for specs that register status codes or method names"
4411    </t>
4412  </list>
4413</t>
4414</section>
4415
4416<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
4417<t>
4418  Closed issues:
4419  <list style="symbols"> 
4420    <t>
4421      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
4422      "Idempotency"
4423    </t>
4424    <t>
4425      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
4426      "TRACE security considerations"
4427    </t>
4428    <t>
4429      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
4430      "Clarify rules for determining what entities a response carries"
4431    </t>
4432    <t>
4433      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
4434      "update note citing RFC 1945 and 2068"
4435    </t>
4436    <t>
4437      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
4438      "update note about redirect limit"
4439    </t>
4440    <t>
4441      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
4442      "Location header ABNF should use 'URI'"
4443    </t>
4444    <t>
4445      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
4446      "fragments in Location vs status 303"
4447    </t>
4448    <t>
4449      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
4450      "move IANA registrations for optional status codes"
4451    </t>
4452  </list>
4453</t>
4454<t>
4455  Partly resolved issues:
4456  <list style="symbols"> 
4457    <t>
4458      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
4459      "Are OPTIONS and TRACE safe?"
4460    </t>
4461  </list>
4462</t>
4463</section>
4464
4465<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
4466<t>
4467  Closed issues:
4468  <list style="symbols"> 
4469    <t>
4470      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
4471      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
4472      status codes when fixing this previously)
4473    </t>
4474  </list>
4475</t>
4476</section>
4477
4478<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
4479<t>
4480  Closed issues:
4481  <list style="symbols"> 
4482    <t>
4483      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4484      "Fragment combination / precedence during redirects"
4485    </t>
4486  </list>
4487</t>
4488<t>
4489  Partly resolved issues:
4490  <list style="symbols"> 
4491    <t>
4492      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
4493      "Location header payload handling"
4494    </t>
4495    <t>
4496      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
4497      "Term for the requested resource's URI"
4498    </t>
4499  </list>
4500</t>
4501</section>
4502
4503<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
4504<t>
4505  Closed issues:
4506  <list style="symbols"> 
4507    <t>
4508      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
4509      "Clarify 'Requested Variant'"
4510    </t>
4511    <t>
4512      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
4513      "Clarify entity / representation / variant terminology"
4514    </t>
4515    <t>
4516      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/139"/>:
4517      "Methods and Caching"
4518    </t>
4519    <t>
4520      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/190"/>:
4521      "OPTIONS vs Max-Forwards"
4522    </t>
4523    <t>
4524      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/199"/>:
4525      "Status codes and caching"
4526    </t>
4527    <t>
4528      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
4529      "consider removing the 'changes from 2068' sections"
4530    </t>
4531  </list>
4532</t>
4533</section>
4534
4535<section title="Since draft-ietf-httpbis-p2-semantics-11" anchor="changes.since.11">
4536<t>
4537  Closed issues:
4538  <list style="symbols"> 
4539    <t>
4540      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/229"/>:
4541      "Considerations for new status codes"
4542    </t>
4543    <t>
4544      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/230"/>:
4545      "Considerations for new methods"
4546    </t>
4547    <t>
4548      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/232"/>:
4549      "User-Agent guidelines" (relating to the 'User-Agent' header field)
4550    </t>
4551  </list>
4552</t>
4553</section>
4554
4555<section title="Since draft-ietf-httpbis-p2-semantics-12" anchor="changes.since.12">
4556<t>
4557  Closed issues:
4558  <list style="symbols"> 
4559    <t>
4560      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4561      "Fragment combination / precedence during redirects" (added warning
4562      about having a fragid on the redirect may cause inconvenience in
4563      some cases)
4564    </t>
4565    <t>
4566      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/79"/>:
4567      "Content-* vs. PUT"
4568    </t>
4569    <t>
4570      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/88"/>:
4571      "205 Bodies"
4572    </t>
4573    <t>
4574      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/102"/>:
4575      "Understanding Content-* on non-PUT requests"
4576    </t>
4577    <t>
4578      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
4579      "Content-*"
4580    </t>
4581    <t>
4582      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/104"/>:
4583      "Header type defaulting"
4584    </t>
4585    <t>
4586      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
4587      "PUT - 'store under' vs 'store at'"
4588    </t>
4589    <t>
4590      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/137"/>:
4591      "duplicate ABNF for Reason-Phrase"
4592    </t>
4593    <t>
4594      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/180"/>:
4595      "Note special status of Content-* prefix in header registration procedures"
4596    </t>
4597    <t>
4598      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/203"/>:
4599      "Max-Forwards vs extension methods"
4600    </t>
4601    <t>
4602      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/213"/>:
4603      "What is the value space of HTTP status codes?" (actually fixed in
4604      draft-ietf-httpbis-p2-semantics-11)
4605    </t>
4606    <t>
4607      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/224"/>:
4608      "Header Classification"
4609    </t>
4610    <t>
4611      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/225"/>:
4612      "PUT side effect: invalidation or just stale?"
4613    </t>
4614    <t>
4615      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/226"/>:
4616      "proxies not supporting certain methods"
4617    </t>
4618    <t>
4619      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/239"/>:
4620      "Migrate CONNECT from RFC2817 to p2"
4621    </t>
4622    <t>
4623      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/240"/>:
4624      "Migrate Upgrade details from RFC2817"
4625    </t>
4626    <t>
4627      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/267"/>:
4628      "clarify PUT semantics'"
4629    </t>
4630    <t>
4631      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/275"/>:
4632      "duplicate ABNF for 'Method'"
4633    </t>
4634    <t>
4635      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4636      "untangle ABNFs for header fields"
4637    </t>
4638  </list>
4639</t>
4640</section>
4641
4642<section title="Since draft-ietf-httpbis-p2-semantics-13" anchor="changes.since.13">
4643<t>
4644  Closed issues:
4645  <list style="symbols"> 
4646    <t>
4647      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4648      "untangle ABNFs for header fields"
4649    </t>
4650    <t>
4651      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/251"/>:
4652      "message-body in CONNECT request"
4653    </t>
4654  </list>
4655</t>
4656</section>
4657
4658<section title="Since draft-ietf-httpbis-p2-semantics-14" anchor="changes.since.14">
4659<t>
4660  Closed issues:
4661  <list style="symbols"> 
4662    <t>
4663      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/255"/>:
4664      "Clarify status code for rate limiting"
4665    </t>
4666    <t>
4667      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/294"/>:
4668      "clarify 403 forbidden"
4669    </t>
4670    <t>
4671      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/296"/>:
4672      "Clarify 203 Non-Authoritative Information"
4673    </t>
4674    <t>
4675      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/298"/>:
4676      "update default reason phrase for 413"
4677    </t>
4678  </list>
4679</t>
4680</section>
4681
4682<section title="Since draft-ietf-httpbis-p2-semantics-15" anchor="changes.since.15">
4683<t>
4684  Closed issues:
4685  <list style="symbols"> 
4686    <t>
4687      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/285"/>:
4688      "Strength of requirements on Accept re: 406"
4689    </t>
4690    <t>
4691      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/303"/>:
4692      "400 response isn't generic"
4693    </t>
4694  </list>
4695</t>
4696</section>
4697
4698<section title="Since draft-ietf-httpbis-p2-semantics-16" anchor="changes.since.16">
4699<t>
4700  Closed issues:
4701  <list style="symbols"> 
4702    <t>
4703      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/160"/>:
4704      "Redirects and non-GET methods"
4705    </t>
4706    <t>
4707      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/186"/>:
4708      "Document HTTP's error-handling philosophy"
4709    </t>
4710    <t>
4711      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/231"/>:
4712      "Considerations for new headers"
4713    </t>
4714    <t>
4715      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/310"/>:
4716      "clarify 303 redirect on HEAD"
4717    </t>
4718  </list>
4719</t>
4720</section>
4721
4722<section title="Since draft-ietf-httpbis-p2-semantics-17" anchor="changes.since.17">
4723<t>
4724  Closed issues:
4725  <list style="symbols"> 
4726    <t>
4727      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
4728      "Location header payload handling"
4729    </t>
4730    <t>
4731      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/255"/>:
4732      "Clarify status code for rate limiting" (change backed out because
4733      a new status code is being defined for this purpose)
4734    </t>
4735    <t>
4736      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/312"/>:
4737      "should there be a permanent variant of 307"
4738    </t>
4739    <t>
4740      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/325"/>:
4741      "When are Location's semantics triggered?"
4742    </t>
4743    <t>
4744      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/327"/>:
4745      "'expect' grammar missing OWS"
4746    </t>
4747    <t>
4748      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/329"/>:
4749      "header field considerations: quoted-string vs use of double quotes"
4750    </t>
4751  </list>
4752</t>
4753</section>
4754
4755<section title="Since draft-ietf-httpbis-p2-semantics-18" anchor="changes.since.18">
4756<t>
4757  Closed issues:
4758  <list style="symbols"> 
4759    <t>
4760      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/333"/>:
4761      "example for 426 response should have a payload"
4762    </t>
4763  </list>
4764</t>
4765</section>
4766
4767</section>
4768
4769</back>
4770</rfc>
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