source: draft-ietf-httpbis/latest/p2-semantics.xml @ 1523

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1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD NOT</bcp14>">
14  <!ENTITY ID-VERSION "latest">
15  <!ENTITY ID-MONTH "February">
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 abnf-extension             "<xref target='Part1' x:rel='#abnf.extension' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY whitespace                 "<xref target='Part1' x:rel='#whitespace' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY field-components           "<xref target='Part1' x:rel='#field.components' 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<x:feedback template="mailto:ietf-http-wg@w3.org?subject={docname},%20%22{section}%22&amp;body=&lt;{ref}&gt;:"/>
109<front>
110
111  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
112
113  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
114    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
115    <address>
116      <postal>
117        <street>345 Park Ave</street>
118        <city>San Jose</city>
119        <region>CA</region>
120        <code>95110</code>
121        <country>USA</country>
122      </postal>
123      <email>fielding@gbiv.com</email>
124      <uri>http://roy.gbiv.com/</uri>
125    </address>
126  </author>
127
128  <author initials="J." surname="Gettys" fullname="Jim Gettys">
129    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
130    <address>
131      <postal>
132        <street>21 Oak Knoll Road</street>
133        <city>Carlisle</city>
134        <region>MA</region>
135        <code>01741</code>
136        <country>USA</country>
137      </postal>
138      <email>jg@freedesktop.org</email>
139      <uri>http://gettys.wordpress.com/</uri>
140    </address>
141  </author>
142 
143  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
144    <organization abbrev="HP">Hewlett-Packard Company</organization>
145    <address>
146      <postal>
147        <street>HP Labs, Large Scale Systems Group</street>
148        <street>1501 Page Mill Road, MS 1177</street>
149        <city>Palo Alto</city>
150        <region>CA</region>
151        <code>94304</code>
152        <country>USA</country>
153      </postal>
154      <email>JeffMogul@acm.org</email>
155    </address>
156  </author>
157
158  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
159    <organization abbrev="Microsoft">Microsoft Corporation</organization>
160    <address>
161      <postal>
162        <street>1 Microsoft Way</street>
163        <city>Redmond</city>
164        <region>WA</region>
165        <code>98052</code>
166        <country>USA</country>
167      </postal>
168      <email>henrikn@microsoft.com</email>
169    </address>
170  </author>
171
172  <author initials="L." surname="Masinter" fullname="Larry Masinter">
173    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
174    <address>
175      <postal>
176        <street>345 Park Ave</street>
177        <city>San Jose</city>
178        <region>CA</region>
179        <code>95110</code>
180        <country>USA</country>
181      </postal>
182      <email>LMM@acm.org</email>
183      <uri>http://larry.masinter.net/</uri>
184    </address>
185  </author>
186 
187  <author initials="P." surname="Leach" fullname="Paul J. Leach">
188    <organization abbrev="Microsoft">Microsoft Corporation</organization>
189    <address>
190      <postal>
191        <street>1 Microsoft Way</street>
192        <city>Redmond</city>
193        <region>WA</region>
194        <code>98052</code>
195      </postal>
196      <email>paulle@microsoft.com</email>
197    </address>
198  </author>
199   
200  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
201    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
202    <address>
203      <postal>
204        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
205        <street>The Stata Center, Building 32</street>
206        <street>32 Vassar Street</street>
207        <city>Cambridge</city>
208        <region>MA</region>
209        <code>02139</code>
210        <country>USA</country>
211      </postal>
212      <email>timbl@w3.org</email>
213      <uri>http://www.w3.org/People/Berners-Lee/</uri>
214    </address>
215  </author>
216
217  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
218    <organization abbrev="W3C">World Wide Web Consortium</organization>
219    <address>
220      <postal>
221        <street>W3C / ERCIM</street>
222        <street>2004, rte des Lucioles</street>
223        <city>Sophia-Antipolis</city>
224        <region>AM</region>
225        <code>06902</code>
226        <country>France</country>
227      </postal>
228      <email>ylafon@w3.org</email>
229      <uri>http://www.raubacapeu.net/people/yves/</uri>
230    </address>
231  </author>
232
233  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
234    <organization abbrev="greenbytes">greenbytes GmbH</organization>
235    <address>
236      <postal>
237        <street>Hafenweg 16</street>
238        <city>Muenster</city><region>NW</region><code>48155</code>
239        <country>Germany</country>
240      </postal>
241      <phone>+49 251 2807760</phone>
242      <facsimile>+49 251 2807761</facsimile>
243      <email>julian.reschke@greenbytes.de</email>
244      <uri>http://greenbytes.de/tech/webdav/</uri>
245    </address>
246  </author>
247
248  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
249  <workgroup>HTTPbis Working Group</workgroup>
250
251<abstract>
252<t>
253   The Hypertext Transfer Protocol (HTTP) is an application-level protocol for
254   distributed, collaborative, hypertext information systems. HTTP has been in
255   use by the World Wide Web global information initiative since 1990. This
256   document is Part 2 of the seven-part specification that defines the protocol
257   referred to as "HTTP/1.1" and, taken together, obsoletes RFC 2616.
258</t>
259<t>
260   Part 2 defines the semantics of HTTP messages as expressed by request
261   methods, request header fields, response status codes, and response header
262   fields.
263</t>
264</abstract>
265
266<note title="Editorial Note (To be removed by RFC Editor)">
267  <t>
268    Discussion of this draft should take place on the HTTPBIS working group
269    mailing list (ietf-http-wg@w3.org), which is archived at
270    <eref target="http://lists.w3.org/Archives/Public/ietf-http-wg/"/>.
271  </t>
272  <t>
273    The current issues list is at
274    <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/> and related
275    documents (including fancy diffs) can be found at
276    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
277  </t>
278  <t>
279    The changes in this draft are summarized in <xref target="changes.since.18"/>.
280  </t>
281</note>
282</front>
283<middle>
284<section title="Introduction" anchor="introduction">
285<t>
286   This document defines HTTP/1.1 request and response semantics.  Each HTTP
287   message, as defined in &messaging;, is in the form of either a request or
288   a response.  An HTTP server listens on a connection for HTTP requests and
289   responds to each request, in the order received on that connection, with
290   one or more HTTP response messages.  This document defines the commonly
291   agreed upon semantics of the HTTP uniform interface, the intentions defined
292   by each request method, and the various response messages that might be
293   expected as a result of applying that method to the target resource.
294</t>
295<t>
296   This document is currently disorganized in order to minimize the changes
297   between drafts and enable reviewers to see the smaller errata changes.
298   A future draft will reorganize the sections to better reflect the content.
299   In particular, the sections will be ordered according to the typical
300   processing of an HTTP request message (after message parsing): resource
301   mapping, methods, request modifying header fields, response status,
302   status modifying header fields, and resource metadata.  The current mess
303   reflects how widely dispersed these topics and associated requirements
304   had become in <xref target="RFC2616"/>.
305</t>
306
307<section title="Conformance and Error Handling" anchor="intro.conformance.and.error.handling">
308<t>
309   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
310   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
311   document are to be interpreted as described in <xref target="RFC2119"/>.
312</t>
313<t>
314   This document defines conformance criteria for several roles in HTTP
315   communication, including Senders, Recipients, Clients, Servers, User-Agents,
316   Origin Servers, Intermediaries, Proxies and Gateways. See &architecture;
317   for definitions of these terms.
318</t>
319<t>
320   An implementation is considered conformant if it complies with all of the
321   requirements associated with its role(s). Note that SHOULD-level requirements
322   are relevant here, unless one of the documented exceptions is applicable.
323</t>
324<t>
325   This document also uses ABNF to define valid protocol elements
326   (<xref target="notation"/>). In addition to the prose requirements placed
327   upon them, Senders &MUST-NOT; generate protocol elements that are invalid.
328</t>
329<t>
330   Unless noted otherwise, Recipients &MAY; take steps to recover a usable
331   protocol element from an invalid construct. However, HTTP does not define
332   specific error handling mechanisms, except in cases where it has direct
333   impact on security. This is because different uses of the protocol require
334   different error handling strategies; for example, a Web browser may wish to
335   transparently recover from a response where the Location header field
336   doesn't parse according to the ABNF, whereby in a systems control protocol
337   using HTTP, this type of error recovery could lead to dangerous consequences.
338</t>
339</section>
340
341<section title="Syntax Notation" anchor="notation">
342  <x:anchor-alias value="CR"/>
343  <x:anchor-alias value="DIGIT"/>
344  <x:anchor-alias value="LF"/>
345  <x:anchor-alias value="HTAB"/>
346  <x:anchor-alias value="VCHAR"/>
347  <x:anchor-alias value="SP"/>
348<t>
349   This specification uses the Augmented Backus-Naur Form (ABNF) notation
350   of <xref target="RFC5234"/> with the list rule extension defined in
351   &notation;<xref target="collected.abnf"/> shows the collected ABNF
352   with the list rule expanded.
353</t>
354<t>
355  The following core rules are included by
356  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
357  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
358  DIGIT (decimal 0-9), DQUOTE (double quote),
359  HEXDIG (hexadecimal 0-9/A-F/a-f), HTAB (horizontal tab), LF (line feed),
360  OCTET (any 8-bit sequence of data), SP (space), and
361  VCHAR (any visible US-ASCII character).
362</t>
363
364<section title="Core Rules" anchor="core.rules">
365  <x:anchor-alias value="obs-text"/>
366  <x:anchor-alias value="quoted-string"/>
367  <x:anchor-alias value="token"/>
368  <x:anchor-alias value="BWS"/>
369  <x:anchor-alias value="OWS"/>
370  <x:anchor-alias value="RWS"/>
371<t>
372  The core rules below are defined in <xref target="Part1"/>:
373</t>
374<figure><artwork type="abnf2616">
375  <x:ref>BWS</x:ref>           = &lt;BWS, defined in &whitespace;&gt;
376  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &whitespace;&gt;
377  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &whitespace;&gt;
378  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &field-components;&gt;
379  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &field-components;&gt;
380  <x:ref>token</x:ref>         = &lt;token, defined in &field-components;&gt;
381</artwork></figure>
382</section>
383
384<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
385  <x:anchor-alias value="absolute-URI"/>
386  <x:anchor-alias value="comment"/>
387  <x:anchor-alias value="partial-URI"/>
388  <x:anchor-alias value="product"/>
389  <x:anchor-alias value="URI-reference"/>
390<t>
391  The ABNF rules below are defined in other parts:
392</t>
393<figure><!--Part1--><artwork type="abnf2616">
394  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
395  <x:ref>comment</x:ref>       = &lt;comment, defined in &field-components;&gt;
396  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
397  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
398  <x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in &uri;&gt;
399</artwork></figure>
400</section>
401</section>
402</section>
403
404<section title="Method" anchor="method">
405  <x:anchor-alias value="Method"/>
406  <x:anchor-alias value="extension-method"/>
407<t>
408   The Method token indicates the request method to be performed on the target
409   resource (&effective-request-uri;). The method is case-sensitive.
410</t>
411<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/>
412  <x:ref>Method</x:ref>         = <x:ref>token</x:ref>
413</artwork></figure>
414<t>
415   The list of methods allowed by a resource can be specified in an
416   Allow header field (<xref target="header.allow"/>). The status code of the response
417   always notifies the client whether a method is currently allowed on a
418   resource, since the set of allowed methods can change dynamically. An
419   origin server &SHOULD; respond with the status code 405 (Method Not Allowed)
420   if the method is known by the origin server but not allowed for the
421   resource, and 501 (Not Implemented) if the method is
422   unrecognized or not implemented by the origin server. The methods GET
423   and HEAD &MUST; be supported by all general-purpose servers. All other
424   methods are &OPTIONAL;; however, if the above methods are implemented,
425   they &MUST; be implemented with the same semantics as those specified
426   in <xref target="method.definitions"/>.
427</t>
428
429<section title="Overview of Methods" anchor="overview.of.methods">
430<t>
431  The methods listed below are defined in <xref target="method.definitions"/>.
432</t>
433<texttable align="left">
434  <ttcol>Method Name</ttcol><ttcol>Defined in...</ttcol>
435 
436  <c>OPTIONS</c> <c><xref target="OPTIONS"/></c>
437  <c>GET</c> <c><xref target="GET"/></c>
438  <c>HEAD</c> <c><xref target="HEAD"/></c>
439  <c>POST</c> <c><xref target="POST"/></c>
440  <c>PUT</c> <c><xref target="PUT"/></c>
441  <c>DELETE</c> <c><xref target="DELETE"/></c>
442  <c>TRACE</c> <c><xref target="TRACE"/></c>
443  <c>CONNECT</c> <c><xref target="CONNECT"/></c>
444</texttable>
445<t>
446  Note that this list is not exhaustive &mdash; it does not include request methods defined
447  in other specifications.
448</t>
449</section>
450
451<section title="Method Registry" anchor="method.registry">
452<t>
453  The HTTP Method Registry defines the name space for the Method token in the
454  Request line of an HTTP request.
455</t>
456<t>
457  Registrations &MUST; include the following fields:
458  <list style="symbols">
459    <t>Method Name (see <xref target="method"/>)</t>
460    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
461    <t>Pointer to specification text</t>
462  </list>
463</t>
464<t>
465  Values to be added to this name space are subject to IETF review
466  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
467</t>
468<t>
469  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
470</t>
471
472<section title="Considerations for New Methods" anchor="considerations.for.new.methods">
473<t>
474   When it is necessary to express new semantics for a HTTP request that
475   aren't specific to a single application or media type, and currently defined
476   methods are inadequate, it may be appropriate to register a new method.
477</t>
478<t>
479   HTTP methods are generic; that is, they are potentially applicable to any
480   resource, not just one particular media type, "type" of resource, or
481   application. As such, it is preferred that new HTTP methods be registered
482   in a document that isn't specific to a single application, so that this is
483   clear.
484</t>
485<t>
486   Due to the parsing rules defined in &message-body;, definitions of HTTP
487   methods cannot prohibit the presence of a message-body on either the request
488   or the response message (with responses to HEAD requests being the single
489   exception). Definitions of new methods cannot change this rule, but they can
490   specify that only zero-length bodies (as opposed to absent bodies) are allowed.
491</t>
492<t>
493   New method definitions need to indicate whether they are safe (<xref
494   target="safe.methods"/>), what semantics (if any) the request body has,
495   and whether they are idempotent (<xref target="idempotent.methods"/>).
496   They also need to state whether they can be cached (&caching;); in
497   particular what conditions a cache may store the response, and under what
498   conditions such a stored response may be used to satisfy a subsequent
499   request.
500</t>
501</section>
502
503</section>
504</section>
505
506<section title="Header Fields" anchor="header.fields">
507<t>
508   Header fields are key value pairs that can be used to communicate data about
509   the message, its payload, the target resource, or about the connection
510   itself (i.e., control data).  See &header-fields; for a general definition
511   of their syntax.
512</t>
513
514<section title="Considerations for Creating Header Fields" anchor="considerations.for.creating.header.fields">
515<t>
516   New header fields are registered using the procedures described in
517   <xref target="RFC3864"/>.
518</t>
519<t>
520   The requirements for header field names are defined in
521   <xref target="RFC3864" x:fmt="of" x:sec="4.1"/>.  Authors of specifications
522   defining new fields are advised to keep the name as short as practical, and
523   not to prefix them with "X-" if they are to be registered (either
524   immediately or in the future).
525</t>
526<t>
527   New header field values typically have their syntax defined using ABNF
528   (<xref target="RFC5234"/>), using the extension defined in &abnf-extension;
529   as necessary, and are usually constrained to the range of ASCII characters.
530   Header fields needing a greater range of characters can use an encoding
531   such as the one defined in <xref target="RFC5987"/>.
532</t>
533<t>
534   Because commas (",") are used as a generic delimiter between field-values,
535   they need to be treated with care if they are allowed in the field-value's
536   payload. Typically, components that might contain a comma are protected with
537   double-quotes using the quoted-string ABNF production (&field-components;).
538</t>
539<t>
540   For example, a textual date and a URI (either of which might contain a comma)
541   could be safely carried in field-values like these:
542</t>
543<figure><artwork type="example">
544  Example-URI-Field: "http://example.com/a.html,foo",
545                     "http://without-a-comma.example.com/"
546  Example-Date-Field: "Sat, 04 May 1996", "Wed, 14 Sep 2005"
547</artwork></figure>
548<t>
549   Note that double quote delimiters almost always are used with the
550   quoted-string production; using a different syntax inside double quotes
551   will likely cause unnecessary confusion.
552</t>
553<t>
554   Many header fields use a format including (case-insensitively) named
555   parameters (for instance, Content-Type, defined in &header-content-type;).
556   Allowing both unquoted (token) and quoted (quoted-string) syntax for the
557   parameter value enables recipients to use existing parser components. When
558   allowing both forms, the meaning of a parameter value ought to be
559   independent of the syntax used for it (for an example, see the notes on
560   parameter handling for media types in &media-types;).
561</t>
562<t>
563   Authors of specifications defining new header fields are advised to consider
564   documenting:
565  <list style="symbols">
566    <x:lt>
567      <t>Whether the field is a single value, or whether it can be a list
568      (delimited by commas; see &header-fields;).</t>
569      <t>If it does not use the list syntax, document how to treat messages
570      where the header field occurs multiple times (a sensible default would
571      be to ignore the header field, but this might not always be the right
572      choice).</t>
573      <t>Note that intermediaries and software libraries might combine
574      multiple header field instances into a single one, despite the header
575      field not allowing this. A robust format enables recipients to discover
576      these situations (good example: "Content-Type", as the comma can only
577      appear inside quoted strings; bad example: "Location", as a comma can
578      occur inside a URI).</t>
579    </x:lt>
580    <x:lt><t>Under what conditions the header field can be used; e.g., only in
581    responses or requests, in all messages, only on responses to a particular
582    request method.</t></x:lt>
583    <x:lt><t>Whether it is appropriate to list the field-name in the Connection header
584    (i.e., if the header is to be hop-by-hop, see &header-connection;).</t></x:lt>
585    <x:lt><t>Under what conditions intermediaries are allowed to modify the header
586    field's value, insert or delete it.</t></x:lt>
587    <x:lt><t>How the header might interact with caching (see <xref target="Part6"/>).</t></x:lt>
588    <x:lt><t>Whether the header field is useful or allowable in trailers (see
589    &chunked-encoding;).</t></x:lt>
590    <x:lt><t>Whether the header field should be preserved across redirects.</t></x:lt>
591  </list>
592</t>
593</section>
594
595<section title="Request Header Fields" anchor="request.header.fields">
596  <x:anchor-alias value="request-header"/>
597<t>
598   The request header fields allow the client to pass additional
599   information about the request, and about the client itself, to the
600   server. These fields act as request modifiers, with semantics
601   equivalent to the parameters on a programming language method
602   invocation.
603</t>
604<texttable align="left">
605  <ttcol>Header Field Name</ttcol>
606  <ttcol>Defined in...</ttcol>
607
608  <c>Accept</c> <c>&header-accept;</c>
609  <c>Accept-Charset</c> <c>&header-accept-charset;</c>
610  <c>Accept-Encoding</c> <c>&header-accept-encoding;</c>
611  <c>Accept-Language</c> <c>&header-accept-language;</c>
612  <c>Authorization</c> <c>&header-authorization;</c>
613  <c>Expect</c> <c><xref target="header.expect"/></c>
614  <c>From</c> <c><xref target="header.from"/></c>
615  <c>Host</c> <c>&header-host;</c>
616  <c>If-Match</c> <c>&header-if-match;</c>
617  <c>If-Modified-Since</c> <c>&header-if-modified-since;</c>
618  <c>If-None-Match</c> <c>&header-if-none-match;</c>
619  <c>If-Range</c> <c>&header-if-range;</c>
620  <c>If-Unmodified-Since</c> <c>&header-if-unmodified-since;</c>
621  <c>Max-Forwards</c> <c><xref target="header.max-forwards"/></c>
622  <c>Proxy-Authorization</c> <c>&header-proxy-authorization;</c>
623  <c>Range</c> <c>&header-range;</c>
624  <c>Referer</c> <c><xref target="header.referer"/></c>
625  <c>TE</c> <c>&header-te;</c>
626  <c>User-Agent</c> <c><xref target="header.user-agent"/></c>
627</texttable>
628</section>
629
630<section title="Response Header Fields" anchor="response.header.fields">
631  <x:anchor-alias value="response-header"/>
632<t>
633   The response header fields allow the server to pass additional
634   information about the response which cannot be placed in the Status-Line.
635   These header fields give information about the server and about
636   further access to the target resource (&effective-request-uri;).
637</t>
638<texttable align="left">
639  <ttcol>Header Field Name</ttcol><ttcol>Defined in...</ttcol>
640
641  <c>Accept-Ranges</c> <c>&header-accept-ranges;</c>
642  <c>Age</c> <c>&header-age;</c>
643  <c>Allow</c> <c><xref target="header.allow"/></c>
644  <c>Date</c> <c><xref target="header.date"/></c>
645  <c>ETag</c> <c>&header-etag;</c>
646  <c>Location</c> <c><xref target="header.location"/></c>
647  <c>Proxy-Authenticate</c> <c>&header-proxy-authenticate;</c>
648  <c>Retry-After</c> <c><xref target="header.retry-after"/></c>
649  <c>Server</c> <c><xref target="header.server"/></c>
650  <c>Vary</c> <c>&header-vary;</c>
651  <c>WWW-Authenticate</c> <c>&header-www-authenticate;</c>
652</texttable>
653</section>
654
655</section>
656
657<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
658  <x:anchor-alias value="Reason-Phrase"/>
659  <x:anchor-alias value="Status-Code"/>
660  <x:anchor-alias value="extension-code"/>
661<t>
662   The Status-Code element is a 3-digit integer result code of the attempt to
663   understand and satisfy the request.
664</t>
665<t>
666   The Reason-Phrase is intended to give a short textual description of the
667   Status-Code and is intended for a human user. The client does not need
668   to examine or display the Reason-Phrase.
669</t>
670<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"/>
671  <x:ref>Status-Code</x:ref>    = 3<x:ref>DIGIT</x:ref>
672  <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> )
673</artwork></figure>
674<t>
675   HTTP status codes are extensible. HTTP applications are not required
676   to understand the meaning of all registered status codes, though such
677   understanding is obviously desirable. However, applications &MUST;
678   understand the class of any status code, as indicated by the first
679   digit, and treat any unrecognized response as being equivalent to the
680   x00 status code of that class, with the exception that an
681   unrecognized response &MUST-NOT; be cached. For example, if an
682   unrecognized status code of 431 is received by the client, it can
683   safely assume that there was something wrong with its request and
684   treat the response as if it had received a 400 status code. In such
685   cases, user agents &SHOULD; present to the user the representation enclosed
686   with the response, since that representation is likely to include human-readable
687   information which will explain the unusual status.
688</t>
689
690<section title="Overview of Status Codes" anchor="overview.of.status.codes">
691<t> 
692   The status codes listed below are defined in <xref target="status.codes"/>
693   of this specification, &p4-status-codes;, &p5-status-codes;, and &p7-status-codes;.
694   The reason phrases listed here are only recommendations &mdash; they can be
695   replaced by local equivalents without affecting the protocol.
696</t>
697<texttable align="left">
698  <ttcol>Status-Code</ttcol>
699  <ttcol>Reason-Phrase</ttcol>
700  <ttcol>Defined in...</ttcol>
701 
702  <c>100</c> <c>Continue</c> <c><xref target="status.100"/></c>
703  <c>101</c> <c>Switching Protocols</c> <c><xref target="status.101"/></c>
704
705  <c>200</c> <c>OK</c> <c><xref target="status.200"/></c>
706  <c>201</c> <c>Created</c> <c><xref target="status.201"/></c>
707  <c>202</c> <c>Accepted</c> <c><xref target="status.202"/></c>
708  <c>203</c> <c>Non-Authoritative Information</c> <c><xref target="status.203"/></c>
709  <c>204</c> <c>No Content</c> <c><xref target="status.204"/></c>
710  <c>205</c> <c>Reset Content</c> <c><xref target="status.205"/></c>
711  <c>206</c> <c>Partial Content</c> <c>&status-206;</c>
712
713  <c>300</c> <c>Multiple Choices</c> <c><xref target="status.300"/></c>
714  <c>301</c> <c>Moved Permanently</c> <c><xref target="status.301"/></c>
715  <c>302</c> <c>Found</c> <c><xref target="status.302"/></c>
716  <c>303</c> <c>See Other</c> <c><xref target="status.303"/></c>
717  <c>304</c> <c>Not Modified</c> <c>&status-304;</c>
718  <c>305</c> <c>Use Proxy</c> <c><xref target="status.305"/></c>
719  <c>307</c> <c>Temporary Redirect</c> <c><xref target="status.307"/></c>
720
721  <c>400</c> <c>Bad Request</c> <c><xref target="status.400"/></c>
722  <c>401</c> <c>Unauthorized</c> <c>&status-401;</c>
723  <c>402</c> <c>Payment Required</c> <c><xref target="status.402"/></c>
724  <c>403</c> <c>Forbidden</c> <c><xref target="status.403"/></c>
725  <c>404</c> <c>Not Found</c> <c><xref target="status.404"/></c>
726  <c>405</c> <c>Method Not Allowed</c> <c><xref target="status.405"/></c>
727  <c>406</c> <c>Not Acceptable</c> <c><xref target="status.406"/></c>
728  <c>407</c> <c>Proxy Authentication Required</c> <c>&status-407;</c>
729  <c>408</c> <c>Request Time-out</c> <c><xref target="status.408"/></c>
730  <c>409</c> <c>Conflict</c> <c><xref target="status.409"/></c>
731  <c>410</c> <c>Gone</c> <c><xref target="status.410"/></c>
732  <c>411</c> <c>Length Required</c> <c><xref target="status.411"/></c>
733  <c>412</c> <c>Precondition Failed</c> <c>&status-412;</c>
734  <c>413</c> <c>Request Representation Too Large</c> <c><xref target="status.413"/></c>
735  <c>414</c> <c>URI Too Long</c> <c><xref target="status.414"/></c>
736  <c>415</c> <c>Unsupported Media Type</c> <c><xref target="status.415"/></c>
737  <c>416</c> <c>Requested range not satisfiable</c> <c>&status-416;</c>
738  <c>417</c> <c>Expectation Failed</c> <c><xref target="status.417"/></c>
739  <c>426</c> <c>Upgrade Required</c> <c><xref target="status.426"/></c>
740
741  <c>500</c> <c>Internal Server Error</c> <c><xref target="status.500"/></c>
742  <c>501</c> <c>Not Implemented</c> <c><xref target="status.501"/></c>
743  <c>502</c> <c>Bad Gateway</c> <c><xref target="status.502"/></c>
744  <c>503</c> <c>Service Unavailable</c> <c><xref target="status.503"/></c>
745  <c>504</c> <c>Gateway Time-out</c> <c><xref target="status.504"/></c>
746  <c>505</c> <c>HTTP Version not supported</c> <c><xref target="status.505"/></c>
747</texttable>
748<t>
749   Note that this list is not exhaustive &mdash; it does not include
750   extension status codes defined in other specifications.
751</t>
752</section>
753
754<section title="Status Code Registry" anchor="status.code.registry">
755<t>
756  The HTTP Status Code Registry defines the name space for the Status-Code
757  token in the Status-Line of an HTTP response.
758</t>
759<t>
760  Values to be added to this name space are subject to IETF review
761  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
762</t>
763<t>
764  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
765</t>
766
767<section title="Considerations for New Status Codes" anchor="considerations.for.new.status.codes">
768<t>
769   When it is necessary to express new semantics for a HTTP response that
770   aren't specific to a single application or media type, and currently defined
771   status codes are inadequate, a new status code can be registered.
772</t>
773<t>
774   HTTP status codes are generic; that is, they are potentially applicable to
775   any resource, not just one particular media type, "type" of resource, or
776   application. As such, it is preferred that new HTTP status codes be
777   registered in a document that isn't specific to a single application, so
778   that this is clear.
779</t>
780<t>
781   Definitions of new HTTP status codes typically explain the request
782   conditions that produce a response containing the status code (e.g.,
783   combinations of request headers and/or method(s)), along with any
784   interactions with response headers (e.g., those that are required, those
785   that modify the semantics of the response).
786</t>
787<t>
788   New HTTP status codes are required to fall under one of the categories
789   defined in <xref target="status.codes"/>. To allow existing parsers to
790   properly handle them, new status codes cannot disallow a response body,
791   although they can mandate a zero-length response body. They can require the
792   presence of one or more particular HTTP response header(s).
793</t>
794<t>
795   Likewise, their definitions can specify that caches are allowed to use
796   heuristics to determine their freshness (see &caching;; by default, it is
797   not allowed), and can define how to determine the resource which they
798   carry a representation for (see <xref
799   target="identifying.response.associated.with.representation"/>; by default,
800   it is anonymous).
801</t>
802</section>
803
804</section>
805
806</section>
807
808<section title="Representation" anchor="representation">
809<t>
810   Request and Response messages &MAY; transfer a representation if not otherwise
811   restricted by the request method or response status code. A representation
812   consists of metadata (representation header fields) and data (representation
813   body).  When a complete or partial representation is enclosed in an HTTP message,
814   it is referred to as the payload of the message. HTTP representations
815   are defined in &payload;.
816</t>
817<t>
818   A representation body is only present in a message when a message-body is
819   present, as described in &message-body;. The representation body is obtained
820   from the message-body by decoding any Transfer-Encoding that might
821   have been applied to ensure safe and proper transfer of the message.
822</t>
823
824<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
825<t>
826   It is sometimes necessary to determine an identifier for the resource
827   associated with a representation.
828</t>
829<t>
830   An HTTP request representation, when present, is always associated with an
831   anonymous (i.e., unidentified) resource.
832</t>
833<t>
834   In the common case, an HTTP response is a representation of the target
835   resource (see &effective-request-uri;). However, this is not always the
836   case. To determine the URI of the resource a response is associated with,
837   the following rules are used (with the first applicable one being selected):
838</t>
839<t><list style="numbers">
840   <t>If the response status code is 200 or 203 and the request method was GET,
841   the response payload is a representation of the target resource.</t>
842   <t>If the response status code is 204, 206, or 304 and the request method was GET
843   or HEAD, the response payload is a partial representation of the target
844   resource.</t>
845   <t>If the response has a Content-Location header field, and that URI is the same
846   as the effective request URI, the response payload is a representation of the
847   target resource.</t>
848   <t>If the response has a Content-Location header field, and that URI is not the
849   same as the effective request URI, then the response asserts that its
850   payload is a representation of the resource identified by the
851   Content-Location URI. However, such an assertion cannot be trusted unless
852   it can be verified by other means (not defined by HTTP).</t>
853   <t>Otherwise, the response is a representation of an anonymous (i.e.,
854   unidentified) resource.</t>
855</list></t>
856<t>
857  <cref anchor="TODO-req-uri">
858   The comparison function is going to have to be defined somewhere,
859   because we already need to compare URIs for things like cache invalidation.</cref>
860</t>
861</section>
862
863</section>
864
865
866<section title="Method Definitions" anchor="method.definitions">
867<t>
868   The set of common request methods for HTTP/1.1 is defined below. Although
869   this set can be expanded, additional methods cannot be assumed to
870   share the same semantics for separately extended clients and servers.
871</t>
872
873<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
874
875<section title="Safe Methods" anchor="safe.methods">
876<iref item="Safe Methods" primary="true"/>
877<t>
878   Implementors need to be aware that the software represents the user in
879   their interactions over the Internet, and need to allow
880   the user to be aware of any actions they take which might have an
881   unexpected significance to themselves or others.
882</t>
883<t>
884   In particular, the convention has been established that the GET, HEAD,
885   OPTIONS, and TRACE request methods &SHOULD-NOT; have the significance
886   of taking an action other than retrieval. These request methods ought
887   to be considered "<x:dfn anchor="safe">safe</x:dfn>".
888   This allows user agents to represent other methods, such as POST, PUT
889   and DELETE, in a special way, so that the user is made aware of the
890   fact that a possibly unsafe action is being requested.
891</t>
892<t>
893   Naturally, it is not possible to ensure that the server does not
894   generate side-effects as a result of performing a GET request; in
895   fact, some dynamic resources consider that a feature. The important
896   distinction here is that the user did not request the side-effects,
897   so therefore cannot be held accountable for them.
898</t>
899</section>
900
901<section title="Idempotent Methods" anchor="idempotent.methods">
902<iref item="Idempotent Methods" primary="true"/>
903<t>
904   Request methods can also have the property of "idempotence" in that,
905   aside from error or expiration issues, the intended effect of multiple
906   identical requests is the same as for a single request.
907   PUT, DELETE, and all safe request methods are idempotent.
908   It is important to note that idempotence refers only to changes
909   requested by the client: a server is free to change its state due
910   to multiple requests for the purpose of tracking those requests,
911   versioning of results, etc.
912</t>
913</section>
914</section>
915
916<section title="OPTIONS" anchor="OPTIONS">
917  <rdf:Description>
918    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
919  </rdf:Description>
920  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
921  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
922<t>
923   The OPTIONS method requests information about the
924   communication options available on the request/response chain
925   identified by the effective request URI. This method allows a client to
926   determine the options and/or requirements associated with a resource,
927   or the capabilities of a server, without implying a resource action
928   or initiating a resource retrieval.
929</t>
930<t>
931   Responses to the OPTIONS method are not cacheable.
932</t>
933<t>
934   If the OPTIONS request includes a message-body (as indicated by the
935   presence of Content-Length or Transfer-Encoding), then the media type
936   &MUST; be indicated by a Content-Type field. Although this
937   specification does not define any use for such a body, future
938   extensions to HTTP might use the OPTIONS body to make more detailed
939   queries on the server.
940</t>
941<t>
942   If the request-target is an asterisk ("*"), the OPTIONS request is
943   intended to apply to the server in general rather than to a specific
944   resource. Since a server's communication options typically depend on
945   the resource, the "*" request is only useful as a "ping" or "no-op"
946   type of method; it does nothing beyond allowing the client to test
947   the capabilities of the server. For example, this can be used to test
948   a proxy for HTTP/1.1 conformance (or lack thereof).
949</t>
950<t>
951   If the request-target is not an asterisk, the OPTIONS request applies
952   only to the options that are available when communicating with that
953   resource.
954</t>
955<t>
956   A 200 response &SHOULD; include any header fields that indicate
957   optional features implemented by the server and applicable to that
958   resource (e.g., Allow), possibly including extensions not defined by
959   this specification. The response body, if any, &SHOULD; also include
960   information about the communication options. The format for such a
961   body is not defined by this specification, but might be defined by
962   future extensions to HTTP. Content negotiation &MAY; be used to select
963   the appropriate response format. If no response body is included, the
964   response &MUST; include a Content-Length field with a field-value of
965   "0".
966</t>
967<t>
968   The Max-Forwards header field &MAY; be used to target a
969   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
970   If no Max-Forwards field is present in the request, then the forwarded
971   request &MUST-NOT; include a Max-Forwards field.
972</t>
973</section>
974
975<section title="GET" anchor="GET">
976  <rdf:Description>
977    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
978  </rdf:Description>
979  <iref primary="true" item="GET method" x:for-anchor=""/>
980  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
981<t>
982   The GET method requests transfer of a current representation of
983   the target resource.
984</t>
985<t>   
986   If the target resource is a data-producing process, it is the
987   produced data which shall be returned as the representation in the response and not
988   the source text of the process, unless that text happens to be the output of
989   the process.
990</t>
991<t>
992   The semantics of the GET method change to a "conditional GET" if the
993   request message includes an If-Modified-Since, If-Unmodified-Since,
994   If-Match, If-None-Match, or If-Range header field. A conditional GET
995   requests that the representation be transferred only under the
996   circumstances described by the conditional header field(s). The
997   conditional GET request is intended to reduce unnecessary network
998   usage by allowing cached representations to be refreshed without requiring
999   multiple requests or transferring data already held by the client.
1000</t>
1001<t>
1002   The semantics of the GET method change to a "partial GET" if the
1003   request message includes a Range header field. A partial GET requests
1004   that only part of the representation be transferred, as described in &header-range;.
1005   The partial GET request is intended to reduce unnecessary
1006   network usage by allowing partially-retrieved representations to be
1007   completed without transferring data already held by the client.
1008</t>
1009<t>
1010   Bodies on GET requests have no defined semantics. Note that sending a body
1011   on a GET request might cause some existing implementations to reject the
1012   request.
1013</t>
1014<t>
1015   The response to a GET request is cacheable and &MAY; be used to satisfy
1016   subsequent GET and HEAD requests (see &caching;).
1017</t>
1018<t>
1019   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
1020</t>
1021</section>
1022
1023<section title="HEAD" anchor="HEAD">
1024  <rdf:Description>
1025    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1026  </rdf:Description>
1027  <iref primary="true" item="HEAD method" x:for-anchor=""/>
1028  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
1029<t>
1030   The HEAD method is identical to GET except that the server &MUST-NOT;
1031   return a message-body in the response. The metadata contained
1032   in the HTTP header fields in response to a HEAD request &SHOULD; be identical
1033   to the information sent in response to a GET request. This method can
1034   be used for obtaining metadata about the representation implied by the
1035   request without transferring the representation body. This method is
1036   often used for testing hypertext links for validity, accessibility,
1037   and recent modification.
1038</t>
1039<t>
1040   The response to a HEAD request is cacheable and &MAY; be used to satisfy
1041   a subsequent HEAD request; see &caching;. It also &MAY; be used to update a previously cached
1042   representation from that resource; if the new field values
1043   indicate that the cached representation differs from the current representation (as
1044   would be indicated by a change in Content-Length, ETag
1045   or Last-Modified), then the cache &MUST; treat the cache entry as
1046   stale.
1047</t>
1048<t>
1049   Bodies on HEAD requests have no defined semantics. Note that sending a body
1050   on a HEAD request might cause some existing implementations to reject the
1051   request.
1052</t>
1053</section>
1054
1055<section title="POST" anchor="POST">
1056  <iref primary="true" item="POST method" x:for-anchor=""/>
1057  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
1058<t>
1059   The POST method requests that the origin server accept the
1060   representation enclosed in the request as data to be processed by the
1061   target resource. POST is designed to allow a uniform method to cover the
1062   following functions:
1063  <list style="symbols">
1064    <t>
1065      Annotation of existing resources;
1066    </t>
1067    <t>
1068        Posting a message to a bulletin board, newsgroup, mailing list,
1069        or similar group of articles;
1070    </t>
1071    <t>
1072        Providing a block of data, such as the result of submitting a
1073        form, to a data-handling process;
1074    </t>
1075    <t>
1076        Extending a database through an append operation.
1077    </t>
1078  </list>
1079</t>
1080<t>
1081   The actual function performed by the POST method is determined by the
1082   server and is usually dependent on the effective request URI.
1083</t>
1084<t>
1085   The action performed by the POST method might not result in a
1086   resource that can be identified by a URI. In this case, either 200
1087   (OK) or 204 (No Content) is the appropriate response status code,
1088   depending on whether or not the response includes a representation that
1089   describes the result.
1090</t>
1091<t>
1092   If a resource has been created on the origin server, the response
1093   &SHOULD; be 201 (Created) and contain a representation which describes the
1094   status of the request and refers to the new resource, and a Location
1095   header field (see <xref target="header.location"/>).
1096</t>
1097<t>
1098   Responses to POST requests are only cacheable when they
1099   include explicit freshness information (see &p6-explicit;). A
1100   cached POST response with a Content-Location header field
1101   (see &header-content-location;) whose value is the effective
1102   Request URI &MAY; be used to satisfy subsequent GET and HEAD requests.
1103</t>
1104<t>
1105   Note that POST caching is not widely implemented.
1106   However, the 303 (See Other) response can be used to direct the
1107   user agent to retrieve a cacheable resource.
1108</t>
1109</section>
1110
1111<section title="PUT" anchor="PUT">
1112  <iref primary="true" item="PUT method" x:for-anchor=""/>
1113  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
1114<t>
1115   The PUT method requests that the state of the target resource
1116   be created or replaced with the state defined by the representation
1117   enclosed in the request message payload.  A successful PUT of a given
1118   representation would suggest that a subsequent GET on that same target
1119   resource will result in an equivalent representation being returned in
1120   a 200 (OK) response.  However, there is no guarantee that such a state
1121   change will be observable, since the target resource might be acted
1122   upon by other user agents in parallel, or might be subject to dynamic
1123   processing by the origin server, before any subsequent GET is received.
1124   A successful response only implies that the user agent's intent was
1125   achieved at the time of its processing by the origin server.
1126</t>
1127<t>   
1128   If the target resource does not have a current representation and
1129   the PUT successfully creates one, then the origin server &MUST; inform
1130   the user agent by sending a 201 (Created) response.  If the target
1131   resource does have a current representation and that representation is
1132   successfully modified in accordance with the state of the enclosed
1133   representation, then either a 200 (OK) or 204 (No Content) response
1134   &SHOULD; be sent to indicate successful completion of the request.
1135</t>
1136<t>
1137   Unrecognized header fields &SHOULD; be ignored (i.e., not saved
1138   as part of the resource state).
1139</t>
1140<t>
1141   An origin server &SHOULD; verify that the PUT representation is
1142   consistent with any constraints which the server has for the target
1143   resource that cannot or will not be changed by the PUT.  This is
1144   particularly important when the origin server uses internal
1145   configuration information related to the URI in order to set the
1146   values for representation metadata on GET responses.  When a PUT
1147   representation is inconsistent with the target resource, the origin
1148   server &SHOULD; either make them consistent, by transforming the
1149   representation or changing the resource configuration, or respond
1150   with an appropriate error message containing sufficient information
1151   to explain why the representation is unsuitable.  The 409 (Conflict)
1152   or 415 (Unsupported Media Type) status codes are suggested, with the
1153   latter being specific to constraints on Content-Type values.
1154</t>
1155<t>
1156   For example, if the target resource is configured to always have a
1157   Content-Type of "text/html" and the representation being PUT has a
1158   Content-Type of "image/jpeg", then the origin server &SHOULD; do one of:
1159   (a) reconfigure the target resource to reflect the new media type;
1160   (b) transform the PUT representation to a format consistent with that
1161   of the resource before saving it as the new resource state; or,
1162   (c) reject the request with a 415 response indicating that the target
1163   resource is limited to "text/html", perhaps including a link to a
1164   different resource that would be a suitable target for the new
1165   representation.
1166</t>
1167<t>
1168   HTTP does not define exactly how a PUT method affects the state
1169   of an origin server beyond what can be expressed by the intent of
1170   the user agent request and the semantics of the origin server response.
1171   It does not define what a resource might be, in any sense of that
1172   word, beyond the interface provided via HTTP.  It does not define
1173   how resource state is "stored", nor how such storage might change
1174   as a result of a change in resource state, nor how the origin server
1175   translates resource state into representations.  Generally speaking,
1176   all implementation details behind the resource interface are
1177   intentionally hidden by the server.
1178</t>
1179<t>
1180   The fundamental difference between the POST and PUT methods is
1181   highlighted by the different intent for the target resource.
1182   The target resource in a POST request is intended to handle the
1183   enclosed representation as a data-accepting process, such as for
1184   a gateway to some other protocol or a document that accepts annotations.
1185   In contrast, the target resource in a PUT request is intended to
1186   take the enclosed representation as a new or replacement value.
1187   Hence, the intent of PUT is idempotent and visible to intermediaries,
1188   even though the exact effect is only known by the origin server.
1189</t>
1190<t>
1191   Proper interpretation of a PUT request presumes that the user agent
1192   knows what target resource is desired.  A service that is intended
1193   to select a proper URI on behalf of the client, after receiving
1194   a state-changing request, &SHOULD; be implemented using the POST
1195   method rather than PUT.  If the origin server will not make the
1196   requested PUT state change to the target resource and instead
1197   wishes to have it applied to a different resource, such as when the
1198   resource has been moved to a different URI, then the origin server
1199   &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
1200   then make its own decision regarding whether or not to redirect the
1201   request.
1202</t>
1203<t>
1204   A PUT request applied to the target resource &MAY; have side-effects
1205   on other resources.  For example, an article might have a URI for
1206   identifying "the current version" (a resource) which is separate
1207   from the URIs identifying each particular version (different
1208   resources that at one point shared the same state as the current version
1209   resource).  A successful PUT request on "the current version" URI might
1210   therefore create a new version resource in addition to changing the
1211   state of the target resource, and might also cause links to be added
1212   between the related resources.
1213</t>
1214<t>
1215   An origin server &SHOULD; reject any PUT request that contains a
1216   Content-Range header field, since it might be misinterpreted as
1217   partial content (or might be partial content that is being mistakenly
1218   PUT as a full representation).  Partial content updates are
1219   possible by targeting a separately identified resource with state
1220   that overlaps a portion of the larger resource, or by using a
1221   different method that has been specifically defined for partial
1222   updates (for example, the PATCH method defined in
1223   <xref target="RFC5789"/>).
1224</t>
1225<t>
1226   Responses to the PUT method are not cacheable. If a PUT request passes
1227   through a cache that has one or more stored responses for the effective
1228   request URI, those stored responses will be invalidated (see
1229   &p6-invalid;).
1230</t>
1231</section>
1232
1233<section title="DELETE" anchor="DELETE">
1234  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1235  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1236<t>
1237   The DELETE method requests that the origin server delete the target
1238   resource. This method &MAY; be overridden by
1239   human intervention (or other means) on the origin server. The client cannot
1240   be guaranteed that the operation has been carried out, even if the
1241   status code returned from the origin server indicates that the action
1242   has been completed successfully. However, the server &SHOULD-NOT; 
1243   indicate success unless, at the time the response is given, it
1244   intends to delete the resource or move it to an inaccessible
1245   location.
1246</t>
1247<t>
1248   A successful response &SHOULD; be 200 (OK) if the response includes an
1249   representation describing the status, 202 (Accepted) if the action has not
1250   yet been enacted, or 204 (No Content) if the action has been enacted
1251   but the response does not include a representation.
1252</t>
1253<t>
1254   Bodies on DELETE requests have no defined semantics. Note that sending a body
1255   on a DELETE request might cause some existing implementations to reject the
1256   request.
1257</t>
1258<t>
1259   Responses to the DELETE method are not cacheable. If a DELETE request
1260   passes through a cache that has one or more stored responses for the
1261   effective request URI, those stored responses will be invalidated (see
1262   &p6-invalid;).
1263</t>
1264</section>
1265
1266<section title="TRACE" anchor="TRACE">
1267  <rdf:Description>
1268    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1269  </rdf:Description>
1270  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1271  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1272<t>
1273   The TRACE method requests a remote, application-layer loop-back
1274   of the request message. The final recipient of the request
1275   &SHOULD; reflect the message received back to the client as the
1276   message-body of a 200 (OK) response. The final recipient is either the
1277   origin server or the first proxy to receive a Max-Forwards
1278   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1279   A TRACE request &MUST-NOT; include a message-body.
1280</t>
1281<t>
1282   TRACE allows the client to see what is being received at the other
1283   end of the request chain and use that data for testing or diagnostic
1284   information. The value of the Via header field (&header-via;) is of
1285   particular interest, since it acts as a trace of the request chain.
1286   Use of the Max-Forwards header field allows the client to limit the
1287   length of the request chain, which is useful for testing a chain of
1288   proxies forwarding messages in an infinite loop.
1289</t>
1290<t>
1291   If the request is valid, the response &SHOULD; have a Content-Type of
1292   "message/http" (see &media-type-message-http;) and contain a message-body
1293   that encloses a copy of the entire request message.
1294   Responses to the TRACE method are not cacheable.
1295</t>
1296</section>
1297
1298<section title="CONNECT" anchor="CONNECT">
1299  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1300  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1301<t>
1302   The CONNECT method requests that the proxy establish a tunnel
1303   to the request-target and then restrict its behavior to blind
1304   forwarding of packets until the connection is closed.
1305</t>
1306<t>
1307   When using CONNECT, the request-target &MUST; use the authority form
1308   (&request-target;); i.e., the request-target consists of only the
1309   host name and port number of the tunnel destination, separated by a colon.
1310   For example,
1311</t>
1312<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1313CONNECT server.example.com:80 HTTP/1.1
1314Host: server.example.com:80
1315
1316</artwork></figure>
1317<t>
1318   Other HTTP mechanisms can be used normally with the CONNECT method &mdash;
1319   except end-to-end protocol Upgrade requests, since the
1320   tunnel must be established first.
1321</t>
1322<t>
1323   For example, proxy authentication might be used to establish the
1324   authority to create a tunnel:
1325</t>
1326<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1327CONNECT server.example.com:80 HTTP/1.1
1328Host: server.example.com:80
1329Proxy-Authorization: basic aGVsbG86d29ybGQ=
1330
1331</artwork></figure>
1332<t>
1333   Bodies on CONNECT requests have no defined semantics. Note that sending a body
1334   on a CONNECT request might cause some existing implementations to reject the
1335   request.
1336</t>
1337<t>
1338   Like any other pipelined HTTP/1.1 request, data to be tunnel may be
1339   sent immediately after the blank line. The usual caveats also apply:
1340   data may be discarded if the eventual response is negative, and the
1341   connection may be reset with no response if more than one TCP segment
1342   is outstanding.
1343</t>
1344
1345<section title="Establishing a Tunnel with CONNECT">
1346<t>
1347   Any successful (2xx) response to a CONNECT request indicates that the
1348   proxy has established a connection to the requested host and port,
1349   and has switched to tunneling the current connection to that server
1350   connection.
1351</t>
1352<t>
1353   It may be the case that the proxy itself can only reach the requested
1354   origin server through another proxy.  In this case, the first proxy
1355   &SHOULD; make a CONNECT request of that next proxy, requesting a tunnel
1356   to the authority.  A proxy &MUST-NOT; respond with any 2xx status code
1357   unless it has either a direct or tunnel connection established to the
1358   authority.
1359</t>
1360<t>
1361   An origin server which receives a CONNECT request for itself &MAY;
1362   respond with a 2xx status code to indicate that a connection is
1363   established.
1364</t>
1365<t>
1366   If at any point either one of the peers gets disconnected, any
1367   outstanding data that came from that peer will be passed to the other
1368   one, and after that also the other connection will be terminated by
1369   the proxy. If there is outstanding data to that peer undelivered,
1370   that data will be discarded.
1371</t>
1372
1373</section>
1374</section>
1375</section>
1376
1377
1378<section title="Status Code Definitions" anchor="status.codes">
1379<t>
1380   The first digit of the Status-Code defines the class of response. The
1381   last two digits do not have any categorization role. There are 5
1382   values for the first digit:
1383  <list style="symbols">
1384    <t>
1385      1xx: Informational - Request received, continuing process
1386    </t>
1387    <t>
1388      2xx: Success - The action was successfully received,
1389        understood, and accepted
1390    </t>
1391    <t>
1392      3xx: Redirection - Further action must be taken in order to
1393        complete the request
1394    </t>
1395    <t>
1396      4xx: Client Error - The request contains bad syntax or cannot
1397        be fulfilled
1398    </t>
1399    <t>
1400      5xx: Server Error - The server failed to fulfill an apparently
1401        valid request
1402    </t>
1403  </list>
1404</t>
1405<t>
1406   Each Status-Code is described below, including any metadata required
1407   in the response.
1408</t>
1409<t>
1410   For most status codes the response can carry a payload, in which case a
1411   Content-Type header field indicates the payload's media type
1412   (&header-content-type;).
1413</t>
1414
1415<section title="Informational 1xx" anchor="status.1xx">
1416<t>
1417   This class of status code indicates a provisional response,
1418   consisting only of the Status-Line and optional header fields, and is
1419   terminated by an empty line. There are no required header fields for this
1420   class of status code. Since HTTP/1.0 did not define any 1xx status
1421   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1422   except under experimental conditions.
1423</t>
1424<t>
1425   A client &MUST; be prepared to accept one or more 1xx status responses
1426   prior to a regular response, even if the client does not expect a 100
1427   (Continue) status message. Unexpected 1xx status responses &MAY; be
1428   ignored by a user agent.
1429</t>
1430<t>
1431   Proxies &MUST; forward 1xx responses, unless the connection between the
1432   proxy and its client has been closed, or unless the proxy itself
1433   requested the generation of the 1xx response. (For example, if a
1434   proxy adds a "Expect: 100-continue" field when it forwards a request,
1435   then it need not forward the corresponding 100 (Continue)
1436   response(s).)
1437</t>
1438
1439<section title="100 Continue" anchor="status.100">
1440  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1441  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1442<t>
1443   The client &SHOULD; continue with its request. This interim response is
1444   used to inform the client that the initial part of the request has
1445   been received and has not yet been rejected by the server. The client
1446   &SHOULD; continue by sending the remainder of the request or, if the
1447   request has already been completed, ignore this response. The server
1448   &MUST; send a final response after the request has been completed. See
1449   &use100; for detailed discussion of the use and handling of this
1450   status code.
1451</t>
1452</section>
1453
1454<section title="101 Switching Protocols" anchor="status.101">
1455  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1456  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1457<t>
1458   The server understands and is willing to comply with the client's
1459   request, via the Upgrade message header field (&header-upgrade;), for a
1460   change in the application protocol being used on this connection. The
1461   server will switch protocols to those defined by the response's
1462   Upgrade header field immediately after the empty line which
1463   terminates the 101 response.
1464</t>
1465<t>
1466   The protocol &SHOULD; be switched only when it is advantageous to do
1467   so. For example, switching to a newer version of HTTP is advantageous
1468   over older versions, and switching to a real-time, synchronous
1469   protocol might be advantageous when delivering resources that use
1470   such features.
1471</t>
1472</section>
1473</section>
1474
1475<section title="Successful 2xx" anchor="status.2xx">
1476<t>
1477   This class of status code indicates that the client's request was
1478   successfully received, understood, and accepted.
1479</t>
1480
1481<section title="200 OK" anchor="status.200">
1482  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1483  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1484<t>
1485   The request has succeeded. The payload returned with the response
1486   is dependent on the method used in the request, for example:
1487  <list style="hanging">
1488    <t hangText="GET">
1489      a representation of the target resource is sent in the response;
1490    </t>
1491    <t hangText="HEAD">
1492      the same representation as GET, except without the message-body;
1493    </t>
1494    <t hangText="POST">
1495      a representation describing or containing the result of the action;
1496    </t>
1497    <t hangText="TRACE">
1498      a representation containing the request message as received by the
1499      end server.
1500    </t>
1501  </list>
1502</t>
1503<t>
1504   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1505   freshness for 200 responses.
1506</t>
1507</section>
1508
1509<section title="201 Created" anchor="status.201">
1510  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1511  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1512<t>
1513   The request has been fulfilled and has resulted in a new resource being
1514   created. The newly created resource can be referenced by the URI(s)
1515   returned in the payload of the response, with the most specific URI
1516   for the resource given by a Location header field. The response
1517   can include a payload containing a list of resource
1518   characteristics and location(s) from which the user or user agent can
1519   choose the one most appropriate.
1520</t>
1521<t>
1522   The origin server &MUST; create the resource before returning the 201 status
1523   code. If the action cannot be carried out immediately, the server &SHOULD;
1524   respond with 202 (Accepted) response instead.
1525</t>
1526<t>
1527   A 201 response &MAY; contain an ETag response header field indicating
1528   the current value of the entity-tag for the representation of the resource
1529   just created (see &header-etag;).
1530</t>
1531</section>
1532
1533<section title="202 Accepted" anchor="status.202">
1534  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1535  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1536<t>
1537   The request has been accepted for processing, but the processing has
1538   not been completed.  The request might or might not eventually be
1539   acted upon, as it might be disallowed when processing actually takes
1540   place. There is no facility for re-sending a status code from an
1541   asynchronous operation such as this.
1542</t>
1543<t>
1544   The 202 response is intentionally non-committal. Its purpose is to
1545   allow a server to accept a request for some other process (perhaps a
1546   batch-oriented process that is only run once per day) without
1547   requiring that the user agent's connection to the server persist
1548   until the process is completed. The representation returned with this
1549   response &SHOULD; include an indication of the request's current status
1550   and either a pointer to a status monitor or some estimate of when the
1551   user can expect the request to be fulfilled.
1552</t>
1553</section>
1554
1555<section title="203 Non-Authoritative Information" anchor="status.203">
1556  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1557  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1558<t>
1559   The representation in the response has been transformed or otherwise
1560   modified by a transforming proxy (&intermediaries;).  Note that the
1561   behavior of transforming intermediaries is controlled by the no-transform
1562   Cache-Control directive (&header-cache-control;).
1563</t>
1564<t>
1565   This status code is only appropriate when the response status code would
1566   have been 200 (OK) otherwise. When the status code before transformation
1567   would have been different, the 214 Transformation Applied warn-code
1568   (&header-warning;) is appropriate.
1569</t>
1570<t>
1571   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1572   freshness for 203 responses.
1573</t>
1574</section>
1575
1576<section title="204 No Content" anchor="status.204">
1577  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1578  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1579<t>
1580   The 204 (No Content) status code indicates that the server has
1581   successfully fulfilled the request and that there is no additional
1582   content to return in the response payload body.  Metadata in the
1583   response header fields refer to the target resource and its current
1584   representation after the requested action.
1585</t>
1586<t>
1587   For example, if a 204 status code is received in response to a PUT
1588   request and the response contains an ETag header field, then the PUT
1589   was successful and the ETag field-value contains the entity-tag for
1590   the new representation of that target resource.
1591</t>
1592<t>
1593   The 204 response allows a server to indicate that the action has been
1594   successfully applied to the target resource while implying that the
1595   user agent &SHOULD-NOT; traverse away from its current "document view"
1596   (if any).  The server assumes that the user agent will provide some
1597   indication of the success to its user, in accord with its own interface,
1598   and apply any new or updated metadata in the response to the active
1599   representation.
1600</t>
1601<t>
1602   For example, a 204 status code is commonly used with document editing
1603   interfaces corresponding to a "save" action, such that the document
1604   being saved remains available to the user for editing. It is also
1605   frequently used with interfaces that expect automated data transfers
1606   to be prevalent, such as within distributed version control systems.
1607</t>
1608<t>
1609   The 204 response &MUST-NOT; include a message-body, and thus is always
1610   terminated by the first empty line after the header fields.
1611</t>
1612</section>
1613
1614<section title="205 Reset Content" anchor="status.205">
1615  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1616  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1617<t>
1618   The server has fulfilled the request and the user agent &SHOULD; reset
1619   the document view which caused the request to be sent. This response
1620   is primarily intended to allow input for actions to take place via
1621   user input, followed by a clearing of the form in which the input is
1622   given so that the user can easily initiate another input action.
1623</t>
1624<t>   
1625   The message-body included with the response &MUST; be empty. Note that
1626   receivers still need to parse the response according to the algorithm defined
1627   in &message-body;.
1628</t>
1629</section>
1630
1631<section title="206 Partial Content" anchor="status.206">
1632  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1633  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1634  <rdf:Description>
1635    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1636  </rdf:Description>
1637<t>
1638   The server has fulfilled the partial GET request for the resource
1639   and the enclosed payload is a partial representation as defined in &status-206;.
1640</t>
1641<t>
1642   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1643   freshness for 206 responses.
1644</t>
1645</section>
1646</section>
1647
1648<section title="Redirection 3xx" anchor="status.3xx">
1649<t>
1650   This class of status code indicates that further action needs to be
1651   taken by the user agent in order to fulfill the request.  If the required
1652   action involves a subsequent HTTP request, it &MAY; be carried out by the
1653   user agent without interaction with the user if and only if the method used
1654   in the second request is known to be "safe", as defined in
1655   <xref target="safe.methods"/>.
1656</t>
1657<t>
1658   There are several types of redirects:
1659   <list style="numbers">
1660      <x:lt>
1661        <t>
1662          Redirects of the request to another URI, either temporarily or
1663          permanently. The new URI is specified in the Location header field.
1664          In this specification, the status codes 301 (Moved Permanently),
1665          302 (Found), and 307 (Temporary Redirect) fall under this category.
1666        </t>
1667      </x:lt>
1668      <x:lt>
1669        <t>
1670          Redirection to a new location that represents an indirect response to
1671          the request, such as the result of a POST operation to be retrieved
1672          with a subsequent GET request. This is status code 303 (See Other).
1673        </t>
1674      </x:lt>
1675      <x:lt>
1676        <t>
1677          Redirection offering a choice of matching resources for use by
1678          agent-driven content negotiation (&agent-driven-negotiation;). This
1679          is status code 300 (Multiple Choices).
1680        </t>
1681      </x:lt>
1682      <x:lt>
1683        <t>
1684          Other kinds of redirection, such as to a cached result (status code 304
1685          (Not Modified)).
1686        </t>
1687      </x:lt>
1688   </list>
1689</t>
1690<x:note>
1691  <t>
1692    <x:h>Note:</x:h> In HTTP/1.0, only the status codes 301 (Moved Permanently)
1693    and 302 (Found) were defined for the first type of redirect, and the second
1694    type did not exist at all (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>).
1695    However it turned out that web forms using POST expected redirects to change
1696    the operation for the subsequent request to retrieval (GET). To address this
1697    use case, HTTP/1.1 introduced the second type of redirect with the status
1698    code 303 (See Other) (<xref target="RFC2068" x:fmt="," x:sec="10.3.4"/>).
1699    As user agents did not change their behavior to maintain backwards
1700    compatibility, the first revision of HTTP/1.1 added yet another status code,
1701    307 (Temporary Redirect), for which the backwards compatibility problems did
1702    not apply (<xref target="RFC2616" x:fmt="," x:sec="10.3.8"/>).
1703    Over 10 years later, most user agents still do method rewriting for
1704    status codes 301 and 302, therefore this specification makes that behavior
1705    conformant in case the original request was POST.
1706  </t>
1707</x:note>
1708<t>
1709   A Location header field on a 3xx response indicates that a client &MAY;
1710   automatically redirect to the URI provided; see <xref target="header.location"/>.
1711</t>
1712<t>
1713   Clients &SHOULD; detect and intervene in cyclical redirections (i.e.,
1714   "infinite" redirection loops).
1715</t>
1716<x:note>
1717  <t>
1718    <x:h>Note:</x:h> An earlier version of this specification recommended a
1719    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1720    Content developers need to be aware that some clients might
1721    implement such a fixed limitation.
1722  </t>
1723</x:note>
1724
1725<section title="300 Multiple Choices" anchor="status.300">
1726  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1727  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1728<t>
1729   The target resource has more than one
1730   representation, each with its own specific location, and agent-driven
1731   negotiation information (&content-negotiation;) is being provided so that
1732   the user (or user agent) can select a preferred representation by
1733   redirecting its request to that location.
1734</t>
1735<t>
1736   Unless it was a HEAD request, the response &SHOULD; include a representation
1737   containing a list of representation metadata and location(s) from
1738   which the user or user agent can choose the one most appropriate. Depending
1739   upon the format and the capabilities of
1740   the user agent, selection of the most appropriate choice &MAY; be
1741   performed automatically. However, this specification does not define
1742   any standard for such automatic selection.
1743</t>
1744<t>
1745   If the server has a preferred choice of representation, it &SHOULD;
1746   include the specific URI for that representation in the Location
1747   field; user agents &MAY; use the Location field value for automatic
1748   redirection.
1749</t>
1750<t>
1751   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1752   freshness for 300 responses.
1753</t>
1754
1755</section>
1756
1757<section title="301 Moved Permanently" anchor="status.301">
1758  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1759  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1760<t>
1761   The target resource has been assigned a new permanent URI and any
1762   future references to this resource &SHOULD; use one of the returned
1763   URIs.  Clients with link editing capabilities ought to automatically
1764   re-link references to the effective request URI to one or more of the new
1765   references returned by the server, where possible.
1766</t>
1767<t>
1768   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1769   freshness for 301 responses.
1770</t>
1771<t>
1772   The new permanent URI &SHOULD; be given by the Location field in the
1773   response. A response payload can contain a short hypertext note with a
1774   hyperlink to 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. A response payload can contain a short hypertext note with a
1805   hyperlink to the new URI(s).
1806</t>
1807<t>
1808   If the 302 status code is received in response to a request method
1809   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1810   then the request &MAY; be automatically redirected by the user agent without
1811   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1812   request unless it can be confirmed by the user, since this might
1813   change the conditions under which the request was issued.
1814</t>
1815<x:note>
1816  <t>
1817    <x:h>Note:</x:h> For historic reasons, user agents &MAY; change the
1818    request method from POST to GET for the subsequent request. If this
1819    behavior is undesired, status code 307 (Temporary Redirect) can be used
1820    instead.
1821  </t>
1822</x:note>
1823</section>
1824
1825<section title="303 See Other" anchor="status.303">
1826  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1827  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1828<t>
1829   The 303 status code indicates that the server is redirecting the
1830   user agent to a different resource, as indicated by a URI in the
1831   Location header field, that is intended to provide an indirect
1832   response to the original request.  In order to satisfy the original
1833   request, a user agent &SHOULD; perform a retrieval request using the
1834   Location URI (a GET or HEAD request if using HTTP), which
1835   may itself be redirected further, and present the eventual result as an
1836   answer to the original request.
1837   Note that the new URI in the Location header field is not considered
1838   equivalent to the effective request URI.
1839</t>
1840<t>
1841   This status code is generally applicable to any HTTP method.  It is
1842   primarily used to allow the output of a POST action to redirect
1843   the user agent to a selected resource, since doing so provides the
1844   information corresponding to the POST response in a form that
1845   can be separately identified, bookmarked, and cached independent
1846   of the original request.
1847</t>
1848<t>
1849   A 303 response to a GET request indicates that the requested
1850   resource does not have a representation of its own that can be
1851   transferred by the server over HTTP.  The Location URI indicates a
1852   resource that is descriptive of the target resource, such that the
1853   follow-on representation might be useful to recipients without
1854   implying that it adequately represents the target resource.
1855   Note that answers to the questions of what can be represented, what
1856   representations are adequate, and what might be a useful description
1857   are outside the scope of HTTP and thus entirely determined by the
1858   URI owner(s).
1859</t>
1860<t>
1861   Except for responses to a HEAD request, the representation of a 303
1862   response &SHOULD; contain a short hypertext note with a hyperlink
1863   to the Location URI.
1864</t>
1865</section>
1866
1867<section title="304 Not Modified" anchor="status.304">
1868  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1869  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1870  <rdf:Description>
1871    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1872  </rdf:Description>
1873<t>
1874   The response to the request has not been modified since the conditions
1875   indicated by the client's conditional GET request, as defined in &status-304;.
1876</t>
1877</section>
1878
1879<section title="305 Use Proxy" anchor="status.305">
1880  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1881  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1882<t>
1883   The 305 status code was defined in a previous version of this specification
1884   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1885</t>
1886</section>
1887
1888<section title="306 (Unused)" anchor="status.306">
1889  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1890  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1891<t>
1892   The 306 status code was used in a previous version of the
1893   specification, is no longer used, and the code is reserved.
1894</t>
1895</section>
1896
1897<section title="307 Temporary Redirect" anchor="status.307">
1898  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1899  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1900<t>
1901   The target resource resides temporarily under a different URI.
1902   Since the redirection can change over time, the client &SHOULD;
1903   continue to use the effective request URI for future requests.
1904</t>
1905<t>
1906   The temporary URI &SHOULD; be given by the Location field in the
1907   response. A response payload can contain a short hypertext note with a
1908   hyperlink to the new URI(s).
1909</t>
1910<t>
1911   If the 307 status code is received in response to a request method
1912   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1913   then the request &MAY; be automatically redirected by the user agent without
1914   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1915   request unless it can be confirmed by the user, since this might
1916   change the conditions under which the request was issued.
1917</t>
1918<x:note>
1919  <t>
1920    <x:h>Note:</x:h> This status code is similar to 302 Found, except that
1921    it does not allow rewriting the request method from POST to GET. This
1922    specification defines no equivalent counterpart for 301 Moved Permanently.
1923  </t>
1924</x:note>
1925</section>
1926</section>
1927
1928<section title="Client Error 4xx" anchor="status.4xx">
1929<t>
1930   The 4xx class of status code is intended for cases in which the
1931   client seems to have erred. Except when responding to a HEAD request,
1932   the server &SHOULD; include a representation containing an explanation of the
1933   error situation, and whether it is a temporary or permanent
1934   condition. These status codes are applicable to any request method.
1935   User agents &SHOULD; display any included representation to the user.
1936</t>
1937<t>
1938   If the client is sending data, a server implementation using TCP
1939   &SHOULD; be careful to ensure that the client acknowledges receipt of
1940   the packet(s) containing the response, before the server closes the
1941   input connection. If the client continues sending data to the server
1942   after the close, the server's TCP stack will send a reset packet to
1943   the client, which might erase the client's unacknowledged input buffers
1944   before they can be read and interpreted by the HTTP application.
1945</t>
1946
1947<section title="400 Bad Request" anchor="status.400">
1948  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1949  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1950<t>
1951   The server cannot or will not process the request, due to a client error (e.g.,
1952   malformed syntax).</t>
1953</section>
1954
1955<section title="401 Unauthorized" anchor="status.401">
1956  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1957  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1958  <rdf:Description>
1959    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1960  </rdf:Description>
1961<t>
1962   The request requires user authentication (see &status-401;).
1963</t>
1964</section>
1965
1966<section title="402 Payment Required" anchor="status.402">
1967  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1968  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1969<t>
1970   This code is reserved for future use.
1971</t>
1972</section>
1973
1974<section title="403 Forbidden" anchor="status.403">
1975  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1976  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1977<t>
1978   The server understood the request, but refuses to authorize it. Providing
1979   different user authentication credentials might be successful, but any
1980   credentials that were provided in the request are insufficient. The request
1981   &SHOULD-NOT; be repeated with the same credentials.
1982</t>
1983<t>
1984   If the request method was not HEAD and the server wishes to make
1985   public why the request has not been fulfilled, it &SHOULD; describe the
1986   reason for the refusal in the representation.  If the server does not wish to
1987   make this information available to the client, the status code 404
1988   (Not Found) &MAY; be used instead.
1989</t>
1990</section>
1991
1992<section title="404 Not Found" anchor="status.404">
1993  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1994  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1995<t>
1996   The server has not found anything matching the effective request URI. No
1997   indication is given of whether the condition is temporary or
1998   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1999   knows, through some internally configurable mechanism, that an old
2000   resource is permanently unavailable and has no forwarding address.
2001   This status code is commonly used when the server does not wish to
2002   reveal exactly why the request has been refused, or when no other
2003   response is applicable.
2004</t>
2005</section>
2006
2007<section title="405 Method Not Allowed" anchor="status.405">
2008  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
2009  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
2010<t>
2011   The method specified in the Request-Line is not allowed for the target
2012   resource. The response &MUST; include an Allow header field containing a
2013   list of valid methods for the requested resource.
2014</t>
2015</section>
2016
2017<section title="406 Not Acceptable" anchor="status.406">
2018  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
2019  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
2020<t>
2021   The resource identified by the request is only capable of generating
2022   response representations which have content characteristics not acceptable
2023   according to the Accept and Accept-* header fields sent in the request
2024   (see &p3-header-fields;).
2025</t>
2026<t>
2027   Unless it was a HEAD request, the response &SHOULD; include a representation
2028   containing a list of available representation characteristics and location(s)
2029   from which the user or user agent can choose the one most
2030   appropriate. Depending upon the format and the
2031   capabilities of the user agent, selection of the most appropriate
2032   choice &MAY; be performed automatically. However, this specification
2033   does not define any standard for such automatic selection.
2034</t>
2035<x:note>
2036  <t>
2037    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
2038    not acceptable according to the accept header fields sent in the
2039    request. In some cases, this might even be preferable to sending a
2040    406 response. User agents are encouraged to inspect the header fields of
2041    an incoming response to determine if it is acceptable.
2042  </t>
2043</x:note>
2044<t>
2045   If the response could be unacceptable, a user agent &SHOULD;
2046   temporarily stop receipt of more data and query the user for a
2047   decision on further actions.
2048</t>
2049</section>
2050
2051<section title="407 Proxy Authentication Required" anchor="status.407">
2052  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
2053  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
2054<t>
2055   This code is similar to 401 (Unauthorized), but indicates that the
2056   client must first authenticate itself with the proxy (see &status-407;).
2057</t>
2058</section>
2059
2060<section title="408 Request Timeout" anchor="status.408">
2061  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
2062  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
2063<t>
2064   The client did not produce a request within the time that the server
2065   was prepared to wait. The client &MAY; repeat the request without
2066   modifications at any later time.
2067</t>
2068</section>
2069
2070<section title="409 Conflict" anchor="status.409">
2071  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
2072  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
2073<t>
2074   The request could not be completed due to a conflict with the current
2075   state of the resource. This code is only allowed in situations where
2076   it is expected that the user might be able to resolve the conflict
2077   and resubmit the request. The response body &SHOULD; include enough
2078   information for the user to recognize the source of the conflict.
2079   Ideally, the response representation would include enough information for the
2080   user or user agent to fix the problem; however, that might not be
2081   possible and is not required.
2082</t>
2083<t>
2084   Conflicts are most likely to occur in response to a PUT request. For
2085   example, if versioning were being used and the representation being PUT
2086   included changes to a resource which conflict with those made by an
2087   earlier (third-party) request, the server might use the 409 response
2088   to indicate that it can't complete the request. In this case, the
2089   response representation would likely contain a list of the differences
2090   between the two versions.
2091</t>
2092</section>
2093
2094<section title="410 Gone" anchor="status.410">
2095  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
2096  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
2097<t>
2098   The target resource is no longer available at the server and no
2099   forwarding address is known. This condition is expected to be
2100   considered permanent. Clients with link editing capabilities &SHOULD;
2101   delete references to the effective request URI after user approval. If the
2102   server does not know, or has no facility to determine, whether or not
2103   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
2104   used instead.
2105</t>
2106<t>
2107   The 410 response is primarily intended to assist the task of web
2108   maintenance by notifying the recipient that the resource is
2109   intentionally unavailable and that the server owners desire that
2110   remote links to that resource be removed. Such an event is common for
2111   limited-time, promotional services and for resources belonging to
2112   individuals no longer working at the server's site. It is not
2113   necessary to mark all permanently unavailable resources as "gone" or
2114   to keep the mark for any length of time &mdash; that is left to the
2115   discretion of the server owner.
2116</t>
2117<t>
2118   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine freshness
2119   for 410 responses.
2120</t>
2121
2122</section>
2123
2124<section title="411 Length Required" anchor="status.411">
2125  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
2126  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
2127<t>
2128   The server refuses to accept the request without a defined Content-Length.
2129   The client &MAY; repeat the request if it adds a valid
2130   Content-Length header field containing the length of the message-body
2131   in the request message.
2132</t>
2133</section>
2134
2135<section title="412 Precondition Failed" anchor="status.412">
2136  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
2137  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
2138  <rdf:Description>
2139    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
2140  </rdf:Description>
2141<t>
2142   The precondition given in one or more of the header fields
2143   evaluated to false when it was tested on the server, as defined in
2144   &status-412;.
2145</t>
2146</section>
2147
2148<section title="413 Request Representation Too Large" anchor="status.413">
2149  <iref primary="true" item="413 Request Representation Too Large (status code)" x:for-anchor=""/>
2150  <iref primary="true" item="Status Codes" subitem="413 Request Representation Too Large" x:for-anchor=""/>
2151<t>
2152   The server is refusing to process a request because the request
2153   representation is larger than the server is willing or able to process. The
2154   server &MAY; close the connection to prevent the client from continuing
2155   the request.
2156</t>
2157<t>
2158   If the condition is temporary, the server &SHOULD; include a Retry-After
2159   header field to indicate that it is temporary and after what
2160   time the client &MAY; try again.
2161</t>
2162</section>
2163
2164<section title="414 URI Too Long" anchor="status.414">
2165  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
2166  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
2167<t>
2168   The server is refusing to service the request because the effective request URI
2169   is longer than the server is willing to interpret. This rare
2170   condition is only likely to occur when a client has improperly
2171   converted a POST request to a GET request with long query
2172   information, when the client has descended into a URI "black hole" of
2173   redirection (e.g., a redirected URI prefix that points to a suffix of
2174   itself), or when the server is under attack by a client attempting to
2175   exploit security holes present in some servers using fixed-length
2176   buffers for reading or manipulating the effective request URI.
2177</t>
2178</section>
2179
2180<section title="415 Unsupported Media Type" anchor="status.415">
2181  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
2182  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
2183<t>
2184   The server is refusing to service the request because the request
2185   payload is in a format not supported by this request method on the
2186   target resource.
2187</t>
2188</section>
2189
2190<section title="416 Requested Range Not Satisfiable" anchor="status.416">
2191  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
2192  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
2193  <rdf:Description>
2194    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
2195  </rdf:Description>
2196<t>
2197   The request included a Range header field (&header-range;) and none of
2198   the range-specifier values in this field overlap the current extent
2199   of the selected resource. See &status-416;.
2200</t>
2201</section>
2202
2203<section title="417 Expectation Failed" anchor="status.417">
2204  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
2205  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
2206<t>
2207   The expectation given in an Expect header field (see <xref target="header.expect"/>)
2208   could not be met by this server, or, if the server is a proxy,
2209   the server has unambiguous evidence that the request could not be met
2210   by the next-hop server.
2211</t>
2212</section>
2213
2214<section title="426 Upgrade Required" anchor="status.426">
2215  <iref primary="true" item="426 Upgrade Required (status code)" x:for-anchor=""/>
2216  <iref primary="true" item="Status Codes" subitem="426 Upgrade Required" x:for-anchor=""/>
2217<t>
2218   The request can not be completed without a prior protocol upgrade. This
2219   response &MUST; include an Upgrade header field (&header-upgrade;)
2220   specifying the required protocols.
2221</t>
2222<figure>
2223<preamble>Example:</preamble>
2224<artwork type="message/http; msgtype=&#34;response&#34;" x:indent-with="  ">
2225HTTP/1.1 426 Upgrade Required
2226Upgrade: HTTP/3.0
2227Connection: Upgrade
2228Content-Length: <x:length-of target="s426body"/>
2229Content-Type: text/plain
2230
2231<x:span anchor="s426body">This service requires use of the HTTP/3.0 protocol.
2232</x:span></artwork></figure>
2233<t>
2234   The server &SHOULD; include a message body in the 426 response which
2235   indicates in human readable form the reason for the error and describes any
2236   alternative courses which may be available to the user.
2237</t>
2238</section>
2239</section>
2240
2241<section title="Server Error 5xx" anchor="status.5xx">
2242<t>
2243   Response status codes beginning with the digit "5" indicate cases in
2244   which the server is aware that it has erred or is incapable of
2245   performing the request. Except when responding to a HEAD request, the
2246   server &SHOULD; include a representation containing an explanation of the
2247   error situation, and whether it is a temporary or permanent
2248   condition. User agents &SHOULD; display any included representation to the
2249   user. These response codes are applicable to any request method.
2250</t>
2251
2252<section title="500 Internal Server Error" anchor="status.500">
2253  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
2254  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
2255<t>
2256   The server encountered an unexpected condition which prevented it
2257   from fulfilling the request.
2258</t>
2259</section>
2260
2261<section title="501 Not Implemented" anchor="status.501">
2262  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
2263  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
2264<t>
2265   The server does not support the functionality required to fulfill the
2266   request. This is the appropriate response when the server does not
2267   recognize the request method and is not capable of supporting it for
2268   any resource.
2269</t>
2270</section>
2271
2272<section title="502 Bad Gateway" anchor="status.502">
2273  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
2274  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
2275<t>
2276   The server, while acting as a gateway or proxy, received an invalid
2277   response from the upstream server it accessed in attempting to
2278   fulfill the request.
2279</t>
2280</section>
2281
2282<section title="503 Service Unavailable" anchor="status.503">
2283  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
2284  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
2285<t>
2286   The server is currently unable to handle the request due to a
2287   temporary overloading or maintenance of the server.
2288</t>
2289<t>
2290   The implication is that this is a temporary condition which will be
2291   alleviated after some delay. If known, the length of the delay &MAY; be
2292   indicated in a Retry-After header field (<xref target="header.retry-after"/>).
2293   If no Retry-After is given, the client &SHOULD; handle the response as it
2294   would for a 500 response.
2295</t>
2296<x:note>
2297  <t>
2298    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
2299    server must use it when becoming overloaded. Some servers might wish
2300    to simply refuse the connection.
2301  </t>
2302</x:note>
2303</section>
2304
2305<section title="504 Gateway Timeout" anchor="status.504">
2306  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
2307  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
2308<t>
2309   The server, while acting as a gateway or proxy, did not receive a
2310   timely response from the upstream server specified by the URI (e.g.,
2311   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
2312   to access in attempting to complete the request.
2313</t>
2314<x:note>
2315  <t>
2316    <x:h>Note</x:h> to implementors: some deployed proxies are known to
2317    return 400 or 500 when DNS lookups time out.
2318  </t>
2319</x:note>
2320</section>
2321
2322<section title="505 HTTP Version Not Supported" anchor="status.505">
2323  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
2324  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
2325<t>
2326   The server does not support, or refuses to support, the protocol
2327   version that was used in the request message. The server is
2328   indicating that it is unable or unwilling to complete the request
2329   using the same major version as the client, as described in &http-version;,
2330   other than with this error message. The response &SHOULD; contain
2331   a representation describing why that version is not supported and what other
2332   protocols are supported by that server.
2333</t>
2334
2335</section>
2336</section>
2337</section>
2338
2339
2340<section title="Date/Time Formats" anchor="http.date">
2341  <x:anchor-alias value="HTTP-date"/>
2342<t>
2343   HTTP applications have historically allowed three different formats
2344   for date/time stamps. However, the preferred format is a fixed-length subset
2345   of that defined by <xref target="RFC1123"/>:
2346</t>
2347<figure><artwork type="example" x:indent-with="  ">
2348Sun, 06 Nov 1994 08:49:37 GMT  ; RFC 1123
2349</artwork></figure>
2350<t>
2351   The other formats are described here only for compatibility with obsolete
2352   implementations.
2353</t>
2354<figure><artwork type="example" x:indent-with="  ">
2355Sunday, 06-Nov-94 08:49:37 GMT ; obsolete RFC 850 format
2356Sun Nov  6 08:49:37 1994       ; ANSI C's asctime() format
2357</artwork></figure>
2358<t>
2359   HTTP/1.1 clients and servers that parse a date value &MUST; accept
2360   all three formats (for compatibility with HTTP/1.0), though they &MUST;
2361   only generate the RFC 1123 format for representing HTTP-date values
2362   in header fields.
2363</t>
2364<t>
2365   All HTTP date/time stamps &MUST; be represented in Greenwich Mean Time
2366   (GMT), without exception. For the purposes of HTTP, GMT is exactly
2367   equal to UTC (Coordinated Universal Time). This is indicated in the
2368   first two formats by the inclusion of "GMT" as the three-letter
2369   abbreviation for time zone, and &MUST; be assumed when reading the
2370   asctime format. HTTP-date is case sensitive and &MUST-NOT; include
2371   additional whitespace beyond that specifically included as SP in the
2372   grammar.
2373</t>
2374<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="HTTP-date"/>
2375  <x:ref>HTTP-date</x:ref>    = <x:ref>rfc1123-date</x:ref> / <x:ref>obs-date</x:ref>
2376</artwork></figure>
2377<t anchor="preferred.date.format">
2378  <x:anchor-alias value="rfc1123-date"/>
2379  <x:anchor-alias value="time-of-day"/>
2380  <x:anchor-alias value="hour"/>
2381  <x:anchor-alias value="minute"/>
2382  <x:anchor-alias value="second"/>
2383  <x:anchor-alias value="day-name"/>
2384  <x:anchor-alias value="day"/>
2385  <x:anchor-alias value="month"/>
2386  <x:anchor-alias value="year"/>
2387  <x:anchor-alias value="GMT"/>
2388  Preferred format:
2389</t>
2390<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"/>
2391  <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>
2392  ; fixed length subset of the format defined in
2393  ; <xref target="RFC1123" x:fmt="of" x:sec="5.2.14"/>
2394 
2395  <x:ref>day-name</x:ref>     = <x:abnf-char-sequence>"Mon"</x:abnf-char-sequence> ; "Mon", case-sensitive
2396               / <x:abnf-char-sequence>"Tue"</x:abnf-char-sequence> ; "Tue", case-sensitive
2397               / <x:abnf-char-sequence>"Wed"</x:abnf-char-sequence> ; "Wed", case-sensitive
2398               / <x:abnf-char-sequence>"Thu"</x:abnf-char-sequence> ; "Thu", case-sensitive
2399               / <x:abnf-char-sequence>"Fri"</x:abnf-char-sequence> ; "Fri", case-sensitive
2400               / <x:abnf-char-sequence>"Sat"</x:abnf-char-sequence> ; "Sat", case-sensitive
2401               / <x:abnf-char-sequence>"Sun"</x:abnf-char-sequence> ; "Sun", case-sensitive
2402               
2403  <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>
2404               ; e.g., 02 Jun 1982
2405
2406  <x:ref>day</x:ref>          = 2<x:ref>DIGIT</x:ref>
2407  <x:ref>month</x:ref>        = <x:abnf-char-sequence>"Jan"</x:abnf-char-sequence> ; "Jan", case-sensitive
2408               / <x:abnf-char-sequence>"Feb"</x:abnf-char-sequence> ; "Feb", case-sensitive
2409               / <x:abnf-char-sequence>"Mar"</x:abnf-char-sequence> ; "Mar", case-sensitive
2410               / <x:abnf-char-sequence>"Apr"</x:abnf-char-sequence> ; "Apr", case-sensitive
2411               / <x:abnf-char-sequence>"May"</x:abnf-char-sequence> ; "May", case-sensitive
2412               / <x:abnf-char-sequence>"Jun"</x:abnf-char-sequence> ; "Jun", case-sensitive
2413               / <x:abnf-char-sequence>"Jul"</x:abnf-char-sequence> ; "Jul", case-sensitive
2414               / <x:abnf-char-sequence>"Aug"</x:abnf-char-sequence> ; "Aug", case-sensitive
2415               / <x:abnf-char-sequence>"Sep"</x:abnf-char-sequence> ; "Sep", case-sensitive
2416               / <x:abnf-char-sequence>"Oct"</x:abnf-char-sequence> ; "Oct", case-sensitive
2417               / <x:abnf-char-sequence>"Nov"</x:abnf-char-sequence> ; "Nov", case-sensitive
2418               / <x:abnf-char-sequence>"Dec"</x:abnf-char-sequence> ; "Dec", case-sensitive
2419  <x:ref>year</x:ref>         = 4<x:ref>DIGIT</x:ref>
2420
2421  <x:ref>GMT</x:ref>   = <x:abnf-char-sequence>"GMT"</x:abnf-char-sequence> ; "GMT", case-sensitive
2422
2423  <x:ref>time-of-day</x:ref>  = <x:ref>hour</x:ref> ":" <x:ref>minute</x:ref> ":" <x:ref>second</x:ref>
2424                 ; 00:00:00 - 23:59:59
2425                 
2426  <x:ref>hour</x:ref>         = 2<x:ref>DIGIT</x:ref>               
2427  <x:ref>minute</x:ref>       = 2<x:ref>DIGIT</x:ref>               
2428  <x:ref>second</x:ref>       = 2<x:ref>DIGIT</x:ref>               
2429</artwork></figure>
2430<t>
2431  The semantics of <x:ref>day-name</x:ref>, <x:ref>day</x:ref>,
2432  <x:ref>month</x:ref>, <x:ref>year</x:ref>, and <x:ref>time-of-day</x:ref> are the
2433  same as those defined for the RFC 5322 constructs
2434  with the corresponding name (<xref target="RFC5322" x:fmt="," x:sec="3.3"/>).
2435</t>
2436<t anchor="obsolete.date.formats">
2437  <x:anchor-alias value="obs-date"/>
2438  <x:anchor-alias value="rfc850-date"/>
2439  <x:anchor-alias value="asctime-date"/>
2440  <x:anchor-alias value="date1"/>
2441  <x:anchor-alias value="date2"/>
2442  <x:anchor-alias value="date3"/>
2443  <x:anchor-alias value="rfc1123-date"/>
2444  <x:anchor-alias value="day-name-l"/>
2445  Obsolete formats:
2446</t>
2447<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="obs-date"/>
2448  <x:ref>obs-date</x:ref>     = <x:ref>rfc850-date</x:ref> / <x:ref>asctime-date</x:ref> 
2449</artwork></figure>
2450<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="rfc850-date"/>
2451  <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>
2452  <x:ref>date2</x:ref>        = <x:ref>day</x:ref> "-" <x:ref>month</x:ref> "-" 2<x:ref>DIGIT</x:ref>
2453                 ; day-month-year (e.g., 02-Jun-82)
2454
2455  <x:ref>day-name-l</x:ref>   = <x:abnf-char-sequence>"Monday"</x:abnf-char-sequence> ; "Monday", case-sensitive
2456         / <x:abnf-char-sequence>"Tuesday"</x:abnf-char-sequence> ; "Tuesday", case-sensitive
2457         / <x:abnf-char-sequence>"Wednesday"</x:abnf-char-sequence> ; "Wednesday", case-sensitive
2458         / <x:abnf-char-sequence>"Thursday"</x:abnf-char-sequence> ; "Thursday", case-sensitive
2459         / <x:abnf-char-sequence>"Friday"</x:abnf-char-sequence> ; "Friday", case-sensitive
2460         / <x:abnf-char-sequence>"Saturday"</x:abnf-char-sequence> ; "Saturday", case-sensitive
2461         / <x:abnf-char-sequence>"Sunday"</x:abnf-char-sequence> ; "Sunday", case-sensitive
2462</artwork></figure>
2463<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="asctime-date"/>
2464  <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>
2465  <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> ))
2466                 ; month day (e.g., Jun  2)
2467</artwork></figure>
2468<x:note>
2469  <t>
2470    <x:h>Note:</x:h> Recipients of date values are encouraged to be robust in
2471    accepting date values that might have been sent by non-HTTP
2472    applications, as is sometimes the case when retrieving or posting
2473    messages via proxies/gateways to SMTP or NNTP.
2474  </t>
2475</x:note>
2476<x:note>
2477  <t>
2478    <x:h>Note:</x:h> HTTP requirements for the date/time stamp format apply only
2479    to their usage within the protocol stream. Clients and servers are
2480    not required to use these formats for user presentation, request
2481    logging, etc.
2482  </t>
2483</x:note>
2484</section>
2485
2486
2487<section title="Header Field Definitions" anchor="header.field.definitions">
2488<t>
2489   This section defines the syntax and semantics of HTTP/1.1 header fields
2490   related to request and response semantics.
2491</t>
2492
2493<section title="Allow" anchor="header.allow">
2494  <iref primary="true" item="Allow header field" x:for-anchor=""/>
2495  <iref primary="true" item="Header Fields" subitem="Allow" x:for-anchor=""/>
2496  <x:anchor-alias value="Allow"/>
2497<t>
2498   The "Allow" header field lists the set of methods advertised as
2499   supported by the target resource. The purpose of this field is strictly to
2500   inform the recipient of valid request methods associated with the resource.
2501</t>
2502<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/>
2503  <x:ref>Allow</x:ref> = #<x:ref>Method</x:ref>
2504</artwork></figure>
2505<t>
2506   Example of use:
2507</t>
2508<figure><artwork type="example">
2509  Allow: GET, HEAD, PUT
2510</artwork></figure>
2511<t>
2512   The actual set of allowed methods is defined by the origin server at the
2513   time of each request.
2514</t>
2515<t>
2516   A proxy &MUST-NOT; modify the Allow header field &mdash; it does not need to
2517   understand all the methods specified in order to handle them according to
2518   the generic message handling rules.
2519</t>
2520</section>
2521
2522<section title="Date" anchor="header.date">
2523  <iref primary="true" item="Date header field" x:for-anchor=""/>
2524  <iref primary="true" item="Header Fields" subitem="Date" x:for-anchor=""/>
2525  <x:anchor-alias value="Date"/>
2526<t>
2527   The "Date" header field represents the date and time at which
2528   the message was originated, having the same semantics as the Origination
2529   Date Field (orig-date) defined in <xref target="RFC5322" x:fmt="of" x:sec="3.6.1"/>.
2530   The field value is an HTTP-date, as defined in <xref target="http.date"/>;
2531   it &MUST; be sent in rfc1123-date format.
2532</t>
2533<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Date"/>
2534  <x:ref>Date</x:ref> = <x:ref>HTTP-date</x:ref>
2535</artwork></figure>
2536<t>
2537   An example is
2538</t>
2539<figure><artwork type="example">
2540  Date: Tue, 15 Nov 1994 08:12:31 GMT
2541</artwork></figure>
2542<t>
2543   Origin servers &MUST; include a Date header field in all responses,
2544   except in these cases:
2545  <list style="numbers">
2546      <t>If the response status code is 100 (Continue) or 101 (Switching
2547         Protocols), the response &MAY; include a Date header field, at
2548         the server's option.</t>
2549
2550      <t>If the response status code conveys a server error, e.g., 500
2551         (Internal Server Error) or 503 (Service Unavailable), and it is
2552         inconvenient or impossible to generate a valid Date.</t>
2553
2554      <t>If the server does not have a clock that can provide a
2555         reasonable approximation of the current time, its responses
2556         &MUST-NOT; include a Date header field.</t>
2557  </list>
2558</t>
2559<t>
2560   A received message that does not have a Date header field &MUST; be
2561   assigned one by the recipient if the message will be cached by that
2562   recipient.
2563</t>
2564<t>
2565   Clients can use the Date header field as well; in order to keep request
2566   messages small, they are advised not to include it when it doesn't convey
2567   any useful information (as is usually the case for requests that do not
2568   contain a payload).
2569</t>
2570<t>
2571   The HTTP-date sent in a Date header field &SHOULD-NOT; represent a date and
2572   time subsequent to the generation of the message. It &SHOULD; represent
2573   the best available approximation of the date and time of message
2574   generation, unless the implementation has no means of generating a
2575   reasonably accurate date and time. In theory, the date ought to
2576   represent the moment just before the payload is generated. In
2577   practice, the date can be generated at any time during the message
2578   origination without affecting its semantic value.
2579</t>
2580</section>
2581
2582<section title="Expect" anchor="header.expect">
2583  <iref primary="true" item="Expect header field" x:for-anchor=""/>
2584  <iref primary="true" item="Header Fields" subitem="Expect" x:for-anchor=""/>
2585  <x:anchor-alias value="Expect"/>
2586  <x:anchor-alias value="expectation"/>
2587  <x:anchor-alias value="expect-param"/>
2588  <x:anchor-alias value="expect-name"/>
2589  <x:anchor-alias value="expect-value"/>
2590<t>
2591   The "Expect" header field is used to indicate that particular
2592   server behaviors are required by the client.
2593</t>
2594<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"/>
2595  <x:ref>Expect</x:ref>       = 1#<x:ref>expectation</x:ref>
2596 
2597  <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> ]
2598                             *( <x:ref>OWS</x:ref> ";" [ <x:ref>OWS</x:ref> <x:ref>expect-param</x:ref> ] )
2599  <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> ]
2600 
2601  <x:ref>expect-name</x:ref>  = <x:ref>token</x:ref>
2602  <x:ref>expect-value</x:ref> = <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref>
2603</artwork></figure>
2604<t>
2605   If all received Expect header field(s) are syntactically valid but contain
2606   an expectation that the recipient does not understand or cannot comply with,
2607   the recipient &MUST; respond with a 417 (Expectation Failed) status code. A
2608   recipient of a syntactically invalid Expectation header field &MUST; respond
2609   with a 4xx status code other than 417.
2610</t>
2611<t>
2612   The only expectation defined by this specification is:
2613</t>
2614<t><iref primary="true" item="100-continue (expect value)"/><iref primary="true" item="Expect Values" subitem="100-continue"/>
2615  100-continue
2616   <list>
2617      <t>
2618        The "100-continue" expectation is defined &use100;. It does not support
2619        any expect-params.
2620      </t>
2621   </list>
2622</t>
2623<t>
2624   Comparison is case-insensitive for names (expect-name), and case-sensitive
2625   for values (expect-value).
2626</t>
2627<t>
2628   The Expect mechanism is hop-by-hop: the above requirements apply to any
2629   server, including proxies. However, the Expect header field itself is
2630   end-to-end; it &MUST; be forwarded if the request is forwarded.
2631</t>
2632<t>
2633   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the Expect
2634   header field.
2635</t>
2636</section>
2637
2638<section title="From" anchor="header.from">
2639  <iref primary="true" item="From header field" x:for-anchor=""/>
2640  <iref primary="true" item="Header Fields" subitem="From" x:for-anchor=""/>
2641  <x:anchor-alias value="From"/>
2642  <x:anchor-alias value="mailbox"/>
2643<t>
2644   The "From" header field, if given, &SHOULD; contain an Internet
2645   e-mail address for the human user who controls the requesting user
2646   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
2647   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
2648</t>
2649<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/>
2650  <x:ref>From</x:ref>    = <x:ref>mailbox</x:ref>
2651 
2652  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2653</artwork></figure>
2654<t>
2655   An example is:
2656</t>
2657<figure><artwork type="example">
2658  From: webmaster@example.org
2659</artwork></figure>
2660<t>
2661   This header field &MAY; be used for logging purposes and as a means for
2662   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2663   be used as an insecure form of access protection. The interpretation
2664   of this field is that the request is being performed on behalf of the
2665   person given, who accepts responsibility for the method performed. In
2666   particular, robot agents &SHOULD; include this header field so that the
2667   person responsible for running the robot can be contacted if problems
2668   occur on the receiving end.
2669</t>
2670<t>
2671   The Internet e-mail address in this field &MAY; be separate from the
2672   Internet host which issued the request. For example, when a request
2673   is passed through a proxy the original issuer's address &SHOULD; be
2674   used.
2675</t>
2676<t>
2677   The client &SHOULD-NOT;  send the From header field without the user's
2678   approval, as it might conflict with the user's privacy interests or
2679   their site's security policy. It is strongly recommended that the
2680   user be able to disable, enable, and modify the value of this field
2681   at any time prior to a request.
2682</t>
2683</section>
2684
2685<section title="Location" anchor="header.location">
2686  <iref primary="true" item="Location header field" x:for-anchor=""/>
2687  <iref primary="true" item="Header Fields" subitem="Location" x:for-anchor=""/>
2688  <x:anchor-alias value="Location"/>
2689<t>
2690   The "Location" header field is used to identify a newly created
2691   resource, or to redirect the recipient to a different location for
2692   completion of the request.
2693</t>
2694<t>
2695   For 201 (Created) responses, the Location is the URI of the new resource
2696   which was created by the request. For 3xx responses, the location &SHOULD;
2697   indicate the server's preferred URI for automatic redirection to the
2698   resource.
2699</t>
2700<t>
2701   The field value consists of a single URI-reference. When it has the form
2702   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2703   the final value is computed by resolving it against the effective request
2704   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
2705</t>
2706<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/>
2707  <x:ref>Location</x:ref> = <x:ref>URI-reference</x:ref>
2708</artwork></figure>
2709<figure>
2710<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical spacing below, it's necessary this way for xml2rfc-->
2711<artwork type="example">
2712  Location: http://www.example.org/pub/WWW/People.html#tim
2713</artwork></figure><figure><artwork type="example">  Location: /index.html
2714</artwork></figure>
2715<x:note>
2716  <t>
2717    <x:h>Note:</x:h> Some recipients attempt to recover from Location fields
2718    that are not valid URI references. This specification does not mandate or
2719    define such processing, but does allow it (see <xref target="intro.conformance.and.error.handling"/>).
2720  </t>
2721</x:note>
2722<t>
2723   There are circumstances in which a fragment identifier in a Location URI
2724   would not be appropriate. For instance, when it appears in a 201 Created
2725   response, where the Location header field specifies the URI for the entire
2726   created resource.
2727</t>
2728<x:note>
2729  <t>
2730    <x:h>Note:</x:h> This specification does not define precedence rules
2731    for the case where the original URI, as navigated to by the user
2732    agent, and the Location header field value both contain fragment
2733    identifiers. Thus be aware that including fragment identifiers might
2734    inconvenience anyone relying on the semantics of the original URI's
2735    fragment identifier.
2736  </t>
2737</x:note>
2738<x:note>
2739  <t>
2740    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2741    from Location in that the Content-Location identifies the most specific
2742    resource corresponding to the enclosed representation.
2743    It is therefore possible for a response to contain header fields for
2744    both Location and Content-Location.
2745  </t>
2746</x:note>
2747</section>
2748
2749<section title="Max-Forwards" anchor="header.max-forwards">
2750  <iref primary="true" item="Max-Forwards header field" x:for-anchor=""/>
2751  <iref primary="true" item="Header Fields" subitem="Max-Forwards" x:for-anchor=""/>
2752  <x:anchor-alias value="Max-Forwards"/>
2753<t>
2754   The "Max-Forwards" header field provides a mechanism with the
2755   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2756   methods to limit the number of times that the request is forwarded by
2757   proxies. This can be useful when the client is attempting to
2758   trace a request which appears to be failing or looping mid-chain.
2759</t>
2760<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/>
2761  <x:ref>Max-Forwards</x:ref> = 1*<x:ref>DIGIT</x:ref>
2762</artwork></figure>
2763<t>
2764   The Max-Forwards value is a decimal integer indicating the remaining
2765   number of times this request message can be forwarded.
2766</t>
2767<t>
2768   Each recipient of a TRACE or OPTIONS request
2769   containing a Max-Forwards header field &MUST; check and update its
2770   value prior to forwarding the request. If the received value is zero
2771   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2772   respond as the final recipient. If the received Max-Forwards value is
2773   greater than zero, then the forwarded message &MUST; contain an updated
2774   Max-Forwards field with a value decremented by one (1).
2775</t>
2776<t>
2777   The Max-Forwards header field &MAY; be ignored for all other request
2778   methods.
2779</t>
2780</section>
2781
2782<section title="Referer" anchor="header.referer">
2783  <iref primary="true" item="Referer header field" x:for-anchor=""/>
2784  <iref primary="true" item="Header Fields" subitem="Referer" x:for-anchor=""/>
2785  <x:anchor-alias value="Referer"/>
2786<t>
2787   The "Referer" [sic] header field allows the client to specify the
2788   URI of the resource from which the effective request URI was obtained (the
2789   "referrer", although the header field is misspelled.).
2790</t>
2791<t>
2792   The Referer header field allows servers to generate lists of back-links to
2793   resources for interest, logging, optimized caching, etc. It also allows
2794   obsolete or mistyped links to be traced for maintenance. Some servers use
2795   Referer as a means of controlling where they allow links from (so-called
2796   "deep linking"), but legitimate requests do not always
2797   contain a Referer header field.
2798</t>
2799<t>
2800   If the effective request URI was obtained from a source that does not have its own
2801   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
2802   sent with the value "about:blank", or not be sent at all. Note that this
2803   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2804</t>
2805<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/>
2806  <x:ref>Referer</x:ref> = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2807</artwork></figure>
2808<t>
2809   Example:
2810</t>
2811<figure><artwork type="example">
2812  Referer: http://www.example.org/hypertext/Overview.html
2813</artwork></figure>
2814<t>
2815   If the field value is a relative URI, it &SHOULD; be interpreted
2816   relative to the effective request URI. The URI &MUST-NOT; include a fragment. See
2817   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2818</t>
2819</section>
2820
2821<section title="Retry-After" anchor="header.retry-after">
2822  <iref primary="true" item="Retry-After header field" x:for-anchor=""/>
2823  <iref primary="true" item="Header Fields" subitem="Retry-After" x:for-anchor=""/>
2824  <x:anchor-alias value="Retry-After"/>
2825<t>
2826   The header "Retry-After" field can be used with a 503 (Service
2827   Unavailable) response to indicate how long the service is expected to
2828   be unavailable to the requesting client. This field &MAY; also be used
2829   with any 3xx (Redirection) response to indicate the minimum time the
2830   user-agent is asked to wait before issuing the redirected request.
2831</t>
2832<t>
2833   The value of this field can be either an HTTP-date or an integer number
2834   of seconds (in decimal) after the time of the response.
2835</t>
2836<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/>
2837  <x:ref>Retry-After</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2838</artwork></figure>
2839<t anchor="rule.delta-seconds">
2840  <x:anchor-alias value="delta-seconds"/>
2841   Time spans are non-negative decimal integers, representing time in
2842   seconds.
2843</t>
2844<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2845  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2846</artwork></figure>
2847<t>
2848   Two examples of its use are
2849</t>
2850<figure><artwork type="example">
2851  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2852  Retry-After: 120
2853</artwork></figure>
2854<t>
2855   In the latter example, the delay is 2 minutes.
2856</t>
2857</section>
2858
2859<section title="Server" anchor="header.server">
2860  <iref primary="true" item="Server header field" x:for-anchor=""/>
2861  <iref primary="true" item="Header Fields" subitem="Server" x:for-anchor=""/>
2862  <x:anchor-alias value="Server"/>
2863<t>
2864   The "Server" header field contains information about the
2865   software used by the origin server to handle the request.
2866</t>
2867<t>
2868   The field can contain multiple product tokens (&product-tokens;) and
2869   comments (&header-fields;) identifying the server and any significant
2870   subproducts. The product tokens are listed in order of their significance
2871   for identifying the application.
2872</t>
2873<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/>
2874  <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> ) )
2875</artwork></figure>
2876<t>
2877   Example:
2878</t>
2879<figure><artwork type="example">
2880  Server: CERN/3.0 libwww/2.17
2881</artwork></figure>
2882<t>
2883   If the response is being forwarded through a proxy, the proxy
2884   application &MUST-NOT; modify the Server header field. Instead, it
2885   &MUST; include a Via field (as described in &header-via;).
2886</t>
2887<x:note>
2888  <t>
2889    <x:h>Note:</x:h> Revealing the specific software version of the server might
2890    allow the server machine to become more vulnerable to attacks
2891    against software that is known to contain security holes. Server
2892    implementors are encouraged to make this field a configurable
2893    option.
2894  </t>
2895</x:note>
2896</section>
2897
2898<section title="User-Agent" anchor="header.user-agent">
2899  <iref primary="true" item="User-Agent header field" x:for-anchor=""/>
2900  <iref primary="true" item="Header Fields" subitem="User-Agent" x:for-anchor=""/>
2901  <x:anchor-alias value="User-Agent"/>
2902<t>
2903   The "User-Agent" header field contains information about the user
2904   agent originating the request. User agents &SHOULD; include this field with
2905   requests.
2906</t>
2907<t>
2908   Typically, it is used for statistical purposes, the tracing of protocol
2909   violations, and tailoring responses to avoid particular user agent
2910   limitations.
2911</t>
2912<t>
2913   The field can contain multiple product tokens (&product-tokens;)
2914   and comments (&header-fields;) identifying the agent and its
2915   significant subproducts. By convention, the product tokens are listed in
2916   order of their significance for identifying the application.
2917</t>
2918<t>
2919   Because this field is usually sent on every request a user agent makes,
2920   implementations are encouraged not to include needlessly fine-grained
2921   detail, and to limit (or even prohibit) the addition of subproducts by third
2922   parties. Overly long and detailed User-Agent field values make requests
2923   larger and can also be used to identify ("fingerprint") the user against
2924   their wishes.
2925</t>
2926<t>
2927   Likewise, implementations are encouraged not to use the product tokens of
2928   other implementations in order to declare compatibility with them, as this
2929   circumvents the purpose of the field. Finally, they are encouraged not to
2930   use comments to identify products; doing so makes the field value more
2931   difficult to parse.
2932</t>
2933<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/>
2934  <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> ) )
2935</artwork></figure>
2936<t>
2937   Example:
2938</t>
2939<figure><artwork type="example">
2940  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2941</artwork></figure>
2942</section>
2943
2944</section>
2945
2946<section title="IANA Considerations" anchor="IANA.considerations">
2947
2948<section title="Method Registry" anchor="method.registration">
2949<t>
2950  The registration procedure for HTTP request methods is defined by
2951  <xref target="method.registry"/> of this document.
2952</t>
2953<t>
2954   The HTTP Method Registry shall be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2955   and be populated with the registrations below:
2956</t>
2957<?BEGININC p2-semantics.iana-methods ?>
2958<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2959<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2960   <ttcol>Method</ttcol>
2961   <ttcol>Safe</ttcol>
2962   <ttcol>Reference</ttcol>
2963   <c>CONNECT</c>
2964   <c>no</c>
2965   <c>
2966      <xref target="CONNECT"/>
2967   </c>
2968   <c>DELETE</c>
2969   <c>no</c>
2970   <c>
2971      <xref target="DELETE"/>
2972   </c>
2973   <c>GET</c>
2974   <c>yes</c>
2975   <c>
2976      <xref target="GET"/>
2977   </c>
2978   <c>HEAD</c>
2979   <c>yes</c>
2980   <c>
2981      <xref target="HEAD"/>
2982   </c>
2983   <c>OPTIONS</c>
2984   <c>yes</c>
2985   <c>
2986      <xref target="OPTIONS"/>
2987   </c>
2988   <c>POST</c>
2989   <c>no</c>
2990   <c>
2991      <xref target="POST"/>
2992   </c>
2993   <c>PUT</c>
2994   <c>no</c>
2995   <c>
2996      <xref target="PUT"/>
2997   </c>
2998   <c>TRACE</c>
2999   <c>yes</c>
3000   <c>
3001      <xref target="TRACE"/>
3002   </c>
3003</texttable>
3004<!--(END)-->
3005<?ENDINC p2-semantics.iana-methods ?>
3006</section>
3007
3008<section title="Status Code Registry" anchor="status.code.registration">
3009<t>
3010   The registration procedure for HTTP Status Codes &mdash; previously defined
3011   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> &mdash; is now defined
3012   by <xref target="status.code.registry"/> of this document.
3013</t>
3014<t>
3015   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
3016   shall be updated with the registrations below:
3017</t>
3018<?BEGININC p2-semantics.iana-status-codes ?>
3019<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
3020<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
3021   <ttcol>Value</ttcol>
3022   <ttcol>Description</ttcol>
3023   <ttcol>Reference</ttcol>
3024   <c>100</c>
3025   <c>Continue</c>
3026   <c>
3027      <xref target="status.100"/>
3028   </c>
3029   <c>101</c>
3030   <c>Switching Protocols</c>
3031   <c>
3032      <xref target="status.101"/>
3033   </c>
3034   <c>200</c>
3035   <c>OK</c>
3036   <c>
3037      <xref target="status.200"/>
3038   </c>
3039   <c>201</c>
3040   <c>Created</c>
3041   <c>
3042      <xref target="status.201"/>
3043   </c>
3044   <c>202</c>
3045   <c>Accepted</c>
3046   <c>
3047      <xref target="status.202"/>
3048   </c>
3049   <c>203</c>
3050   <c>Non-Authoritative Information</c>
3051   <c>
3052      <xref target="status.203"/>
3053   </c>
3054   <c>204</c>
3055   <c>No Content</c>
3056   <c>
3057      <xref target="status.204"/>
3058   </c>
3059   <c>205</c>
3060   <c>Reset Content</c>
3061   <c>
3062      <xref target="status.205"/>
3063   </c>
3064   <c>300</c>
3065   <c>Multiple Choices</c>
3066   <c>
3067      <xref target="status.300"/>
3068   </c>
3069   <c>301</c>
3070   <c>Moved Permanently</c>
3071   <c>
3072      <xref target="status.301"/>
3073   </c>
3074   <c>302</c>
3075   <c>Found</c>
3076   <c>
3077      <xref target="status.302"/>
3078   </c>
3079   <c>303</c>
3080   <c>See Other</c>
3081   <c>
3082      <xref target="status.303"/>
3083   </c>
3084   <c>305</c>
3085   <c>Use Proxy</c>
3086   <c>
3087      <xref target="status.305"/>
3088   </c>
3089   <c>306</c>
3090   <c>(Unused)</c>
3091   <c>
3092      <xref target="status.306"/>
3093   </c>
3094   <c>307</c>
3095   <c>Temporary Redirect</c>
3096   <c>
3097      <xref target="status.307"/>
3098   </c>
3099   <c>400</c>
3100   <c>Bad Request</c>
3101   <c>
3102      <xref target="status.400"/>
3103   </c>
3104   <c>402</c>
3105   <c>Payment Required</c>
3106   <c>
3107      <xref target="status.402"/>
3108   </c>
3109   <c>403</c>
3110   <c>Forbidden</c>
3111   <c>
3112      <xref target="status.403"/>
3113   </c>
3114   <c>404</c>
3115   <c>Not Found</c>
3116   <c>
3117      <xref target="status.404"/>
3118   </c>
3119   <c>405</c>
3120   <c>Method Not Allowed</c>
3121   <c>
3122      <xref target="status.405"/>
3123   </c>
3124   <c>406</c>
3125   <c>Not Acceptable</c>
3126   <c>
3127      <xref target="status.406"/>
3128   </c>
3129   <c>407</c>
3130   <c>Proxy Authentication Required</c>
3131   <c>
3132      <xref target="status.407"/>
3133   </c>
3134   <c>408</c>
3135   <c>Request Timeout</c>
3136   <c>
3137      <xref target="status.408"/>
3138   </c>
3139   <c>409</c>
3140   <c>Conflict</c>
3141   <c>
3142      <xref target="status.409"/>
3143   </c>
3144   <c>410</c>
3145   <c>Gone</c>
3146   <c>
3147      <xref target="status.410"/>
3148   </c>
3149   <c>411</c>
3150   <c>Length Required</c>
3151   <c>
3152      <xref target="status.411"/>
3153   </c>
3154   <c>413</c>
3155   <c>Request Representation Too Large</c>
3156   <c>
3157      <xref target="status.413"/>
3158   </c>
3159   <c>414</c>
3160   <c>URI Too Long</c>
3161   <c>
3162      <xref target="status.414"/>
3163   </c>
3164   <c>415</c>
3165   <c>Unsupported Media Type</c>
3166   <c>
3167      <xref target="status.415"/>
3168   </c>
3169   <c>417</c>
3170   <c>Expectation Failed</c>
3171   <c>
3172      <xref target="status.417"/>
3173   </c>
3174   <c>426</c>
3175   <c>Upgrade Required</c>
3176   <c>
3177      <xref target="status.426"/>
3178   </c>
3179   <c>500</c>
3180   <c>Internal Server Error</c>
3181   <c>
3182      <xref target="status.500"/>
3183   </c>
3184   <c>501</c>
3185   <c>Not Implemented</c>
3186   <c>
3187      <xref target="status.501"/>
3188   </c>
3189   <c>502</c>
3190   <c>Bad Gateway</c>
3191   <c>
3192      <xref target="status.502"/>
3193   </c>
3194   <c>503</c>
3195   <c>Service Unavailable</c>
3196   <c>
3197      <xref target="status.503"/>
3198   </c>
3199   <c>504</c>
3200   <c>Gateway Timeout</c>
3201   <c>
3202      <xref target="status.504"/>
3203   </c>
3204   <c>505</c>
3205   <c>HTTP Version Not Supported</c>
3206   <c>
3207      <xref target="status.505"/>
3208   </c>
3209</texttable>
3210<!--(END)-->
3211<?ENDINC p2-semantics.iana-status-codes ?>
3212</section>
3213<section title="Header Field Registration" anchor="header.field.registration">
3214<t>
3215   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
3216   with the permanent registrations below (see <xref target="RFC3864"/>):
3217</t>
3218<?BEGININC p2-semantics.iana-headers ?>
3219<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
3220<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
3221   <ttcol>Header Field Name</ttcol>
3222   <ttcol>Protocol</ttcol>
3223   <ttcol>Status</ttcol>
3224   <ttcol>Reference</ttcol>
3225
3226   <c>Allow</c>
3227   <c>http</c>
3228   <c>standard</c>
3229   <c>
3230      <xref target="header.allow"/>
3231   </c>
3232   <c>Date</c>
3233   <c>http</c>
3234   <c>standard</c>
3235   <c>
3236      <xref target="header.date"/>
3237   </c>
3238   <c>Expect</c>
3239   <c>http</c>
3240   <c>standard</c>
3241   <c>
3242      <xref target="header.expect"/>
3243   </c>
3244   <c>From</c>
3245   <c>http</c>
3246   <c>standard</c>
3247   <c>
3248      <xref target="header.from"/>
3249   </c>
3250   <c>Location</c>
3251   <c>http</c>
3252   <c>standard</c>
3253   <c>
3254      <xref target="header.location"/>
3255   </c>
3256   <c>Max-Forwards</c>
3257   <c>http</c>
3258   <c>standard</c>
3259   <c>
3260      <xref target="header.max-forwards"/>
3261   </c>
3262   <c>Referer</c>
3263   <c>http</c>
3264   <c>standard</c>
3265   <c>
3266      <xref target="header.referer"/>
3267   </c>
3268   <c>Retry-After</c>
3269   <c>http</c>
3270   <c>standard</c>
3271   <c>
3272      <xref target="header.retry-after"/>
3273   </c>
3274   <c>Server</c>
3275   <c>http</c>
3276   <c>standard</c>
3277   <c>
3278      <xref target="header.server"/>
3279   </c>
3280   <c>User-Agent</c>
3281   <c>http</c>
3282   <c>standard</c>
3283   <c>
3284      <xref target="header.user-agent"/>
3285   </c>
3286</texttable>
3287<!--(END)-->
3288<?ENDINC p2-semantics.iana-headers ?>
3289<t>
3290   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
3291</t>
3292</section>
3293</section>
3294
3295<section title="Security Considerations" anchor="security.considerations">
3296<t>
3297   This section is meant to inform application developers, information
3298   providers, and users of the security limitations in HTTP/1.1 as
3299   described by this document. The discussion does not include
3300   definitive solutions to the problems revealed, though it does make
3301   some suggestions for reducing security risks.
3302</t>
3303
3304<section title="Transfer of Sensitive Information" anchor="security.sensitive">
3305<t>
3306   Like any generic data transfer protocol, HTTP cannot regulate the
3307   content of the data that is transferred, nor is there any a priori
3308   method of determining the sensitivity of any particular piece of
3309   information within the context of any given request. Therefore,
3310   applications &SHOULD; supply as much control over this information as
3311   possible to the provider of that information. Four header fields are
3312   worth special mention in this context: Server, Via, Referer and From.
3313</t>
3314<t>
3315   Revealing the specific software version of the server might allow the
3316   server machine to become more vulnerable to attacks against software
3317   that is known to contain security holes. Implementors &SHOULD; make the
3318   Server header field a configurable option.
3319</t>
3320<t>
3321   Proxies which serve as a portal through a network firewall &SHOULD;
3322   take special precautions regarding the transfer of header information
3323   that identifies the hosts behind the firewall. In particular, they
3324   &SHOULD; remove, or replace with sanitized versions, any Via fields
3325   generated behind the firewall.
3326</t>
3327<t>
3328   The Referer header field allows reading patterns to be studied and reverse
3329   links drawn. Although it can be very useful, its power can be abused
3330   if user details are not separated from the information contained in
3331   the Referer. Even when the personal information has been removed, the
3332   Referer header field might indicate a private document's URI whose
3333   publication would be inappropriate.
3334</t>
3335<t>
3336   The information sent in the From field might conflict with the user's
3337   privacy interests or their site's security policy, and hence it
3338   &SHOULD-NOT;  be transmitted without the user being able to disable,
3339   enable, and modify the contents of the field. The user &MUST; be able
3340   to set the contents of this field within a user preference or
3341   application defaults configuration.
3342</t>
3343<t>
3344   We suggest, though do not require, that a convenient toggle interface
3345   be provided for the user to enable or disable the sending of From and
3346   Referer information.
3347</t>
3348<t>
3349   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref
3350   target="header.server"/>) header fields can sometimes be used to determine
3351   that a specific client or server has a particular security hole which might
3352   be exploited. Unfortunately, this same information is often used for other
3353   valuable purposes for which HTTP currently has no better mechanism.
3354</t>
3355<t>
3356   Furthermore, the User-Agent header field may contain enough entropy to be
3357   used, possibly in conjunction with other material, to uniquely identify the
3358   user.
3359</t>
3360<t>
3361   Some request methods, like TRACE (<xref target="TRACE"/>), expose information
3362   that was sent in request header fields within the body of their response.
3363   Clients &SHOULD; be careful with sensitive information, like Cookies,
3364   Authorization credentials, and other header fields that might be used to
3365   collect data from the client.
3366</t> 
3367</section>
3368
3369<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
3370<t>
3371   Because the source of a link might be private information or might
3372   reveal an otherwise private information source, it is strongly
3373   recommended that the user be able to select whether or not the
3374   Referer field is sent. For example, a browser client could have a
3375   toggle switch for browsing openly/anonymously, which would
3376   respectively enable/disable the sending of Referer and From
3377   information.
3378</t>
3379<t>
3380   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
3381   HTTP request if the referring page was transferred with a secure
3382   protocol.
3383</t>
3384<t>
3385   Authors of services &SHOULD-NOT; use GET-based forms for the submission of
3386   sensitive data because that data will be placed in the request-target. Many
3387   existing servers, proxies, and user agents log or display the request-target
3388   in places where it might be visible to third parties. Such services can
3389   use POST-based form submission instead.
3390</t>
3391</section>
3392
3393<section title="Location Headers and Spoofing" anchor="location.spoofing">
3394<t>
3395   If a single server supports multiple organizations that do not trust
3396   one another, then it &MUST; check the values of Location and Content-Location
3397   header fields in responses that are generated under control of
3398   said organizations to make sure that they do not attempt to
3399   invalidate resources over which they have no authority.
3400</t>
3401</section>
3402
3403<section title="Security Considerations for CONNECT">
3404<t>
3405   Since tunneled data is opaque to the proxy, there are additional
3406   risks to tunneling to other well-known or reserved ports.
3407   A HTTP client CONNECTing to port 25 could relay spam
3408   via SMTP, for example. As such, proxies &SHOULD; restrict CONNECT
3409   access to a small number of known ports.
3410</t>
3411</section>
3412
3413</section>
3414
3415<section title="Acknowledgments" anchor="acks">
3416<t>
3417  See &acks;.
3418</t>
3419</section>
3420</middle>
3421<back>
3422
3423<references title="Normative References">
3424
3425<reference anchor="Part1">
3426  <front>
3427    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
3428    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3429      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3430      <address><email>fielding@gbiv.com</email></address>
3431    </author>
3432    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3433      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3434      <address><email>jg@freedesktop.org</email></address>
3435    </author>
3436    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3437      <organization abbrev="HP">Hewlett-Packard Company</organization>
3438      <address><email>JeffMogul@acm.org</email></address>
3439    </author>
3440    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3441      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3442      <address><email>henrikn@microsoft.com</email></address>
3443    </author>
3444    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3445      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3446      <address><email>LMM@acm.org</email></address>
3447    </author>
3448    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3449      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3450      <address><email>paulle@microsoft.com</email></address>
3451    </author>
3452    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3453      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3454      <address><email>timbl@w3.org</email></address>
3455    </author>
3456    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3457      <organization abbrev="W3C">World Wide Web Consortium</organization>
3458      <address><email>ylafon@w3.org</email></address>
3459    </author>
3460    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3461      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3462      <address><email>julian.reschke@greenbytes.de</email></address>
3463    </author>
3464    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3465  </front>
3466  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
3467  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
3468</reference>
3469
3470<reference anchor="Part3">
3471  <front>
3472    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
3473    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3474      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3475      <address><email>fielding@gbiv.com</email></address>
3476    </author>
3477    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3478      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3479      <address><email>jg@freedesktop.org</email></address>
3480    </author>
3481    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3482      <organization abbrev="HP">Hewlett-Packard Company</organization>
3483      <address><email>JeffMogul@acm.org</email></address>
3484    </author>
3485    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3486      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3487      <address><email>henrikn@microsoft.com</email></address>
3488    </author>
3489    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3490      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3491      <address><email>LMM@acm.org</email></address>
3492    </author>
3493    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3494      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3495      <address><email>paulle@microsoft.com</email></address>
3496    </author>
3497    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3498      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3499      <address><email>timbl@w3.org</email></address>
3500    </author>
3501    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3502      <organization abbrev="W3C">World Wide Web Consortium</organization>
3503      <address><email>ylafon@w3.org</email></address>
3504    </author>
3505    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3506      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3507      <address><email>julian.reschke@greenbytes.de</email></address>
3508    </author>
3509    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3510  </front>
3511  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
3512  <x:source href="p3-payload.xml" basename="p3-payload"/>
3513</reference>
3514
3515<reference anchor="Part4">
3516  <front>
3517    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
3518    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3519      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3520      <address><email>fielding@gbiv.com</email></address>
3521    </author>
3522    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3523      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3524      <address><email>jg@freedesktop.org</email></address>
3525    </author>
3526    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3527      <organization abbrev="HP">Hewlett-Packard Company</organization>
3528      <address><email>JeffMogul@acm.org</email></address>
3529    </author>
3530    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3531      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3532      <address><email>henrikn@microsoft.com</email></address>
3533    </author>
3534    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3535      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3536      <address><email>LMM@acm.org</email></address>
3537    </author>
3538    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3539      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3540      <address><email>paulle@microsoft.com</email></address>
3541    </author>
3542    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3543      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3544      <address><email>timbl@w3.org</email></address>
3545    </author>
3546    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3547      <organization abbrev="W3C">World Wide Web Consortium</organization>
3548      <address><email>ylafon@w3.org</email></address>
3549    </author>
3550    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3551      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3552      <address><email>julian.reschke@greenbytes.de</email></address>
3553    </author>
3554    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3555  </front>
3556  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
3557  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
3558</reference>
3559
3560<reference anchor="Part5">
3561  <front>
3562    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
3563    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3564      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3565      <address><email>fielding@gbiv.com</email></address>
3566    </author>
3567    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3568      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3569      <address><email>jg@freedesktop.org</email></address>
3570    </author>
3571    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3572      <organization abbrev="HP">Hewlett-Packard Company</organization>
3573      <address><email>JeffMogul@acm.org</email></address>
3574    </author>
3575    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3576      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3577      <address><email>henrikn@microsoft.com</email></address>
3578    </author>
3579    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3580      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3581      <address><email>LMM@acm.org</email></address>
3582    </author>
3583    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3584      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3585      <address><email>paulle@microsoft.com</email></address>
3586    </author>
3587    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3588      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3589      <address><email>timbl@w3.org</email></address>
3590    </author>
3591    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3592      <organization abbrev="W3C">World Wide Web Consortium</organization>
3593      <address><email>ylafon@w3.org</email></address>
3594    </author>
3595    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3596      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3597      <address><email>julian.reschke@greenbytes.de</email></address>
3598    </author>
3599    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3600  </front>
3601  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
3602  <x:source href="p5-range.xml" basename="p5-range"/>
3603</reference>
3604
3605<reference anchor="Part6">
3606  <front>
3607    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
3608    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3609      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3610      <address><email>fielding@gbiv.com</email></address>
3611    </author>
3612    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3613      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3614      <address><email>jg@freedesktop.org</email></address>
3615    </author>
3616    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3617      <organization abbrev="HP">Hewlett-Packard Company</organization>
3618      <address><email>JeffMogul@acm.org</email></address>
3619    </author>
3620    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3621      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3622      <address><email>henrikn@microsoft.com</email></address>
3623    </author>
3624    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3625      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3626      <address><email>LMM@acm.org</email></address>
3627    </author>
3628    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3629      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3630      <address><email>paulle@microsoft.com</email></address>
3631    </author>
3632    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3633      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3634      <address><email>timbl@w3.org</email></address>
3635    </author>
3636    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3637      <organization abbrev="W3C">World Wide Web Consortium</organization>
3638      <address><email>ylafon@w3.org</email></address>
3639    </author>
3640    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
3641      <organization>Rackspace</organization>
3642      <address><email>mnot@mnot.net</email></address>
3643    </author>
3644    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3645      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3646      <address><email>julian.reschke@greenbytes.de</email></address>
3647    </author>
3648    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3649  </front>
3650  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
3651  <x:source href="p6-cache.xml" basename="p6-cache"/>
3652</reference>
3653
3654<reference anchor="Part7">
3655  <front>
3656    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
3657    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3658      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3659      <address><email>fielding@gbiv.com</email></address>
3660    </author>
3661    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3662      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3663      <address><email>jg@freedesktop.org</email></address>
3664    </author>
3665    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3666      <organization abbrev="HP">Hewlett-Packard Company</organization>
3667      <address><email>JeffMogul@acm.org</email></address>
3668    </author>
3669    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3670      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3671      <address><email>henrikn@microsoft.com</email></address>
3672    </author>
3673    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3674      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3675      <address><email>LMM@acm.org</email></address>
3676    </author>
3677    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3678      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3679      <address><email>paulle@microsoft.com</email></address>
3680    </author>
3681    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3682      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3683      <address><email>timbl@w3.org</email></address>
3684    </author>
3685    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3686      <organization abbrev="W3C">World Wide Web Consortium</organization>
3687      <address><email>ylafon@w3.org</email></address>
3688    </author>
3689    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3690      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3691      <address><email>julian.reschke@greenbytes.de</email></address>
3692    </author>
3693    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3694  </front>
3695  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3696  <x:source href="p7-auth.xml" basename="p7-auth"/>
3697</reference>
3698
3699<reference anchor="RFC2119">
3700  <front>
3701    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3702    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3703      <organization>Harvard University</organization>
3704      <address><email>sob@harvard.edu</email></address>
3705    </author>
3706    <date month="March" year="1997"/>
3707  </front>
3708  <seriesInfo name="BCP" value="14"/>
3709  <seriesInfo name="RFC" value="2119"/>
3710</reference>
3711
3712<reference anchor="RFC3986">
3713 <front>
3714  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3715  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3716    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3717    <address>
3718       <email>timbl@w3.org</email>
3719       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3720    </address>
3721  </author>
3722  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3723    <organization abbrev="Day Software">Day Software</organization>
3724    <address>
3725      <email>fielding@gbiv.com</email>
3726      <uri>http://roy.gbiv.com/</uri>
3727    </address>
3728  </author>
3729  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3730    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3731    <address>
3732      <email>LMM@acm.org</email>
3733      <uri>http://larry.masinter.net/</uri>
3734    </address>
3735  </author>
3736  <date month='January' year='2005'></date>
3737 </front>
3738 <seriesInfo name="STD" value="66"/>
3739 <seriesInfo name="RFC" value="3986"/>
3740</reference>
3741
3742<reference anchor="RFC5234">
3743  <front>
3744    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3745    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3746      <organization>Brandenburg InternetWorking</organization>
3747      <address>
3748        <email>dcrocker@bbiw.net</email>
3749      </address> 
3750    </author>
3751    <author initials="P." surname="Overell" fullname="Paul Overell">
3752      <organization>THUS plc.</organization>
3753      <address>
3754        <email>paul.overell@thus.net</email>
3755      </address>
3756    </author>
3757    <date month="January" year="2008"/>
3758  </front>
3759  <seriesInfo name="STD" value="68"/>
3760  <seriesInfo name="RFC" value="5234"/>
3761</reference>
3762
3763</references>
3764
3765<references title="Informative References">
3766
3767<reference anchor="RFC1123">
3768  <front>
3769    <title>Requirements for Internet Hosts - Application and Support</title>
3770    <author initials="R." surname="Braden" fullname="Robert Braden">
3771      <organization>University of Southern California (USC), Information Sciences Institute</organization>
3772      <address><email>Braden@ISI.EDU</email></address>
3773    </author>
3774    <date month="October" year="1989"/>
3775  </front>
3776  <seriesInfo name="STD" value="3"/>
3777  <seriesInfo name="RFC" value="1123"/>
3778</reference>
3779
3780<reference anchor="RFC1945">
3781  <front>
3782    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3783    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3784      <organization>MIT, Laboratory for Computer Science</organization>
3785      <address><email>timbl@w3.org</email></address>
3786    </author>
3787    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3788      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3789      <address><email>fielding@ics.uci.edu</email></address>
3790    </author>
3791    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3792      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3793      <address><email>frystyk@w3.org</email></address>
3794    </author>
3795    <date month="May" year="1996"/>
3796  </front>
3797  <seriesInfo name="RFC" value="1945"/>
3798</reference>
3799
3800<reference anchor="RFC2068">
3801  <front>
3802    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3803    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3804      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3805      <address><email>fielding@ics.uci.edu</email></address>
3806    </author>
3807    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3808      <organization>MIT Laboratory for Computer Science</organization>
3809      <address><email>jg@w3.org</email></address>
3810    </author>
3811    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3812      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3813      <address><email>mogul@wrl.dec.com</email></address>
3814    </author>
3815    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3816      <organization>MIT Laboratory for Computer Science</organization>
3817      <address><email>frystyk@w3.org</email></address>
3818    </author>
3819    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3820      <organization>MIT Laboratory for Computer Science</organization>
3821      <address><email>timbl@w3.org</email></address>
3822    </author>
3823    <date month="January" year="1997"/>
3824  </front>
3825  <seriesInfo name="RFC" value="2068"/>
3826</reference>
3827
3828<reference anchor="RFC2616">
3829  <front>
3830    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3831    <author initials="R." surname="Fielding" fullname="R. Fielding">
3832      <organization>University of California, Irvine</organization>
3833      <address><email>fielding@ics.uci.edu</email></address>
3834    </author>
3835    <author initials="J." surname="Gettys" fullname="J. Gettys">
3836      <organization>W3C</organization>
3837      <address><email>jg@w3.org</email></address>
3838    </author>
3839    <author initials="J." surname="Mogul" fullname="J. Mogul">
3840      <organization>Compaq Computer Corporation</organization>
3841      <address><email>mogul@wrl.dec.com</email></address>
3842    </author>
3843    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3844      <organization>MIT Laboratory for Computer Science</organization>
3845      <address><email>frystyk@w3.org</email></address>
3846    </author>
3847    <author initials="L." surname="Masinter" fullname="L. Masinter">
3848      <organization>Xerox Corporation</organization>
3849      <address><email>masinter@parc.xerox.com</email></address>
3850    </author>
3851    <author initials="P." surname="Leach" fullname="P. Leach">
3852      <organization>Microsoft Corporation</organization>
3853      <address><email>paulle@microsoft.com</email></address>
3854    </author>
3855    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3856      <organization>W3C</organization>
3857      <address><email>timbl@w3.org</email></address>
3858    </author>
3859    <date month="June" year="1999"/>
3860  </front>
3861  <seriesInfo name="RFC" value="2616"/>
3862</reference>
3863
3864<reference anchor='RFC2817'>
3865  <front>
3866    <title>Upgrading to TLS Within HTTP/1.1</title>
3867    <author initials='R.' surname='Khare' fullname='R. Khare'>
3868      <organization>4K Associates / UC Irvine</organization>
3869      <address><email>rohit@4K-associates.com</email></address>
3870    </author>
3871    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3872      <organization>Agranat Systems, Inc.</organization>
3873      <address><email>lawrence@agranat.com</email></address>
3874    </author>
3875    <date year='2000' month='May' />
3876  </front>
3877  <seriesInfo name='RFC' value='2817' />
3878</reference>
3879
3880<reference anchor='RFC3864'>
3881  <front>
3882    <title>Registration Procedures for Message Header Fields</title>
3883    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3884      <organization>Nine by Nine</organization>
3885      <address><email>GK-IETF@ninebynine.org</email></address>
3886    </author>
3887    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3888      <organization>BEA Systems</organization>
3889      <address><email>mnot@pobox.com</email></address>
3890    </author>
3891    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3892      <organization>HP Labs</organization>
3893      <address><email>JeffMogul@acm.org</email></address>
3894    </author>
3895    <date year='2004' month='September' />
3896  </front>
3897  <seriesInfo name='BCP' value='90' />
3898  <seriesInfo name='RFC' value='3864' />
3899</reference>
3900
3901<reference anchor='RFC5226'>
3902  <front>
3903    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3904    <author initials='T.' surname='Narten' fullname='T. Narten'>
3905      <organization>IBM</organization>
3906      <address><email>narten@us.ibm.com</email></address>
3907    </author>
3908    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3909      <organization>Google</organization>
3910      <address><email>Harald@Alvestrand.no</email></address>
3911    </author>
3912    <date year='2008' month='May' />
3913  </front>
3914  <seriesInfo name='BCP' value='26' />
3915  <seriesInfo name='RFC' value='5226' />
3916</reference>
3917
3918<reference anchor="RFC5322">
3919  <front>
3920    <title>Internet Message Format</title>
3921    <author initials="P." surname="Resnick" fullname="P. Resnick">
3922      <organization>Qualcomm Incorporated</organization>
3923    </author>
3924    <date year="2008" month="October"/>
3925  </front> 
3926  <seriesInfo name="RFC" value="5322"/>
3927</reference>
3928
3929<reference anchor='RFC5789'>
3930  <front>
3931    <title>PATCH Method for HTTP</title>
3932    <author initials='L.' surname='Dusseault' fullname='L. Dusseault'>
3933      <organization>Linden Lab</organization>
3934    </author>
3935    <author initials='J.' surname='Snell' fullname='J. Snell' />
3936    <date year='2010' month='March' />
3937  </front>
3938  <seriesInfo name='RFC' value='5789' />
3939</reference>
3940
3941<reference anchor="RFC5987">
3942        <front>
3943    <title>Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters</title>
3944    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke">
3945      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3946      <address>
3947        <postal>
3948          <street>Hafenweg 16</street>
3949          <city>Muenster</city><region>NW</region><code>48155</code>
3950          <country>Germany</country>
3951        </postal>
3952        <email>julian.reschke@greenbytes.de</email>     
3953        <uri>http://greenbytes.de/tech/webdav/</uri>   
3954      </address>
3955    </author>
3956    <date month="August" year="2010"/>
3957  </front>
3958  <seriesInfo name="RFC" value="5987"/>
3959</reference>
3960
3961</references>
3962
3963<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3964<t>
3965  This document takes over the Status Code Registry, previously defined
3966  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3967  (<xref target="status.code.registry"/>)
3968</t>
3969<t>
3970  Clarify definition of POST.
3971  (<xref target="POST"/>)
3972</t>
3973<t>
3974  Remove requirement to handle all Content-* header fields; ban use of
3975  Content-Range with PUT.
3976  (<xref target="PUT"/>)
3977</t>
3978<t>
3979  Take over definition of CONNECT method from <xref target="RFC2817"/>.
3980  (<xref target="CONNECT"/>)
3981</t>
3982<t>
3983  Broadened the definition of 203 (Non-Authoritative Information) to include
3984  cases of payload transformations as well.
3985  (<xref target="status.203"/>)
3986</t>
3987<t>
3988  Removed the normative requirements on response payloads for status codes
3989  301, 302, and 307.
3990  (<xref target="status.3xx"/>)
3991</t>
3992<t>
3993  Failed to consider that there are many other request methods that are safe
3994  to automatically redirect, and further that the user agent is able to make
3995  that determination based on the request method semantics.
3996  Furthermore, allow user agents to rewrite the method from POST to GET
3997  for status codes 301 and 302.
3998  (Sections <xref format="counter" target="status.301"/>,
3999  <xref format="counter" target="status.302"/> and
4000  <xref format="counter" target="status.307"/>)
4001</t>
4002<t>
4003  Deprecate 305 Use Proxy status code, because user agents did not implement it.
4004  It used to indicate that the target resource must be accessed through the
4005  proxy given by the Location field. The Location field gave the URI of the
4006  proxy. The recipient was expected to repeat this single request via the proxy.
4007  (<xref target="status.305"/>)
4008</t>
4009<t>
4010  Define status 426 (Upgrade Required) (this was incorporated from
4011  <xref target="RFC2817"/>).
4012  (<xref target="status.426"/>)
4013</t>
4014<t>
4015  Change ABNF productions for header fields to only define the field value.
4016  (<xref target="header.field.definitions"/>)
4017</t>
4018<t>
4019  Reclassify "Allow" as response header field, removing the option to
4020  specify it in a PUT request.
4021  Relax the server requirement on the contents of the Allow header field and
4022  remove requirement on clients to always trust the header field value.
4023  (<xref target="header.allow"/>)
4024</t>
4025<t>
4026  The ABNF for the Expect header field has been both fixed (allowing parameters
4027  for value-less expectations as well) and simplified (allowing trailing
4028  semicolons after "100-continue" when they were invalid before).
4029  (<xref target="header.expect"/>)
4030</t>
4031<t>
4032  Correct syntax of Location header field to allow URI references (including
4033  relative references and fragments), as referred symbol "absoluteURI" wasn't
4034  what was expected, and add some clarifications as to when use of fragments
4035  would not be appropriate.
4036  (<xref target="header.location"/>)
4037</t>
4038<t>
4039  Restrict Max-Forwards header field to OPTIONS and TRACE (previously,
4040  extension methods could have used it as well).
4041  (<xref target="header.max-forwards"/>)
4042</t>
4043<t>
4044  Allow Referer field value of "about:blank" as alternative to not specifying it.
4045  (<xref target="header.referer"/>)
4046</t>
4047<t>
4048  In the description of the Server header field, the Via field
4049  was described as a SHOULD. The requirement was and is stated
4050  correctly in the description of the Via header field in &header-via;.
4051  (<xref target="header.server"/>)
4052</t>
4053</section>
4054
4055<?BEGININC p2-semantics.abnf-appendix ?>
4056<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
4057<figure>
4058<artwork type="abnf" name="p2-semantics.parsed-abnf">
4059<x:ref>Allow</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
4060
4061<x:ref>BWS</x:ref> = &lt;BWS, defined in [Part1], Section 3.2.1&gt;
4062
4063<x:ref>Date</x:ref> = HTTP-date
4064
4065<x:ref>Expect</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
4066
4067<x:ref>From</x:ref> = mailbox
4068
4069<x:ref>GMT</x:ref> = %x47.4D.54 ; GMT
4070
4071<x:ref>HTTP-date</x:ref> = rfc1123-date / obs-date
4072
4073<x:ref>Location</x:ref> = URI-reference
4074
4075<x:ref>Max-Forwards</x:ref> = 1*DIGIT
4076<x:ref>Method</x:ref> = token
4077
4078<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 3.2.1&gt;
4079
4080<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 3.2.1&gt;
4081<x:ref>Reason-Phrase</x:ref> = *( HTAB / SP / VCHAR / obs-text )
4082<x:ref>Referer</x:ref> = absolute-URI / partial-URI
4083<x:ref>Retry-After</x:ref> = HTTP-date / delta-seconds
4084
4085<x:ref>Server</x:ref> = product *( RWS ( product / comment ) )
4086<x:ref>Status-Code</x:ref> = 3DIGIT
4087
4088<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.7&gt;
4089<x:ref>User-Agent</x:ref> = product *( RWS ( product / comment ) )
4090
4091<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.7&gt;
4092<x:ref>asctime-date</x:ref> = day-name SP date3 SP time-of-day SP year
4093
4094<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2.4&gt;
4095
4096<x:ref>date1</x:ref> = day SP month SP year
4097<x:ref>date2</x:ref> = day "-" month "-" 2DIGIT
4098<x:ref>date3</x:ref> = month SP ( 2DIGIT / ( SP DIGIT ) )
4099<x:ref>day</x:ref> = 2DIGIT
4100<x:ref>day-name</x:ref> = %x4D.6F.6E ; Mon
4101 / %x54.75.65 ; Tue
4102 / %x57.65.64 ; Wed
4103 / %x54.68.75 ; Thu
4104 / %x46.72.69 ; Fri
4105 / %x53.61.74 ; Sat
4106 / %x53.75.6E ; Sun
4107<x:ref>day-name-l</x:ref> = %x4D.6F.6E.64.61.79 ; Monday
4108 / %x54.75.65.73.64.61.79 ; Tuesday
4109 / %x57.65.64.6E.65.73.64.61.79 ; Wednesday
4110 / %x54.68.75.72.73.64.61.79 ; Thursday
4111 / %x46.72.69.64.61.79 ; Friday
4112 / %x53.61.74.75.72.64.61.79 ; Saturday
4113 / %x53.75.6E.64.61.79 ; Sunday
4114<x:ref>delta-seconds</x:ref> = 1*DIGIT
4115
4116<x:ref>expect-name</x:ref> = token
4117<x:ref>expect-param</x:ref> = expect-name [ BWS "=" BWS expect-value ]
4118<x:ref>expect-value</x:ref> = token / quoted-string
4119<x:ref>expectation</x:ref> = expect-name [ BWS "=" BWS expect-value ] *( OWS ";" [
4120 OWS expect-param ] )
4121
4122<x:ref>hour</x:ref> = 2DIGIT
4123
4124<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
4125<x:ref>minute</x:ref> = 2DIGIT
4126<x:ref>month</x:ref> = %x4A.61.6E ; Jan
4127 / %x46.65.62 ; Feb
4128 / %x4D.61.72 ; Mar
4129 / %x41.70.72 ; Apr
4130 / %x4D.61.79 ; May
4131 / %x4A.75.6E ; Jun
4132 / %x4A.75.6C ; Jul
4133 / %x41.75.67 ; Aug
4134 / %x53.65.70 ; Sep
4135 / %x4F.63.74 ; Oct
4136 / %x4E.6F.76 ; Nov
4137 / %x44.65.63 ; Dec
4138
4139<x:ref>obs-date</x:ref> = rfc850-date / asctime-date
4140<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 3.2.4&gt;
4141
4142<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.7&gt;
4143<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 5.2&gt;
4144
4145<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 3.2.4&gt;
4146
4147<x:ref>rfc1123-date</x:ref> = day-name "," SP date1 SP time-of-day SP GMT
4148<x:ref>rfc850-date</x:ref> = day-name-l "," SP date2 SP time-of-day SP GMT
4149
4150<x:ref>second</x:ref> = 2DIGIT
4151
4152<x:ref>time-of-day</x:ref> = hour ":" minute ":" second
4153<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 3.2.4&gt;
4154
4155<x:ref>year</x:ref> = 4DIGIT
4156</artwork>
4157</figure>
4158<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
4159; Allow defined but not used
4160; Date defined but not used
4161; Expect defined but not used
4162; From defined but not used
4163; Location defined but not used
4164; Max-Forwards defined but not used
4165; Reason-Phrase defined but not used
4166; Referer defined but not used
4167; Retry-After defined but not used
4168; Server defined but not used
4169; Status-Code defined but not used
4170; User-Agent defined but not used
4171</artwork></figure></section>
4172<?ENDINC p2-semantics.abnf-appendix ?>
4173
4174<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
4175
4176<section title="Since RFC 2616">
4177<t>
4178  Extracted relevant partitions from <xref target="RFC2616"/>.
4179</t>
4180</section>
4181
4182<section title="Since draft-ietf-httpbis-p2-semantics-00">
4183<t>
4184  Closed issues:
4185  <list style="symbols"> 
4186    <t>
4187      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
4188      "Via is a MUST"
4189      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
4190    </t>
4191    <t>
4192      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
4193      "Fragments allowed in Location"
4194      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
4195    </t>
4196    <t>
4197      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
4198      "Safe Methods vs Redirection"
4199      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
4200    </t>
4201    <t>
4202      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
4203      "Revise description of the POST method"
4204      (<eref target="http://purl.org/NET/http-errata#post"/>)
4205    </t>
4206    <t>
4207      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
4208      "Normative and Informative references"
4209    </t>
4210    <t>
4211      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
4212      "RFC2606 Compliance"
4213    </t>
4214    <t>
4215      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
4216      "Informative references"
4217    </t>
4218    <t>
4219      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
4220      "Redundant cross-references"
4221    </t>
4222  </list>
4223</t>
4224<t>
4225  Other changes:
4226  <list style="symbols"> 
4227    <t>
4228      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
4229    </t>
4230  </list>
4231</t>
4232</section>
4233
4234<section title="Since draft-ietf-httpbis-p2-semantics-01">
4235<t>
4236  Closed issues:
4237  <list style="symbols"> 
4238    <t>
4239      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
4240      "PUT side effects"
4241    </t>
4242    <t>
4243      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
4244      "Duplicate Host header requirements"
4245    </t>
4246  </list>
4247</t>
4248<t>
4249  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4250  <list style="symbols"> 
4251    <t>
4252      Move "Product Tokens" section (back) into Part 1, as "token" is used
4253      in the definition of the Upgrade header field.
4254    </t>
4255    <t>
4256      Add explicit references to BNF syntax and rules imported from other parts of the specification.
4257    </t>
4258    <t>
4259      Copy definition of delta-seconds from Part6 instead of referencing it.
4260    </t>
4261  </list>
4262</t>
4263</section>
4264
4265<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
4266<t>
4267  Closed issues:
4268  <list style="symbols"> 
4269    <t>
4270      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
4271      "Requiring Allow in 405 responses"
4272    </t>
4273    <t>
4274      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
4275      "Status Code Registry"
4276    </t>
4277    <t>
4278      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
4279      "Redirection vs. Location"
4280    </t>
4281    <t>
4282      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
4283      "Cacheability of 303 response"
4284    </t>
4285    <t>
4286      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
4287      "305 Use Proxy"
4288    </t>
4289    <t>
4290      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
4291      "Classification for Allow header"
4292    </t>
4293    <t>
4294      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
4295      "PUT - 'store under' vs 'store at'"
4296    </t>
4297  </list>
4298</t>
4299<t>
4300  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
4301  <list style="symbols"> 
4302    <t>
4303      Reference RFC 3984, and update header field registrations for headers defined
4304      in this document.
4305    </t>
4306  </list>
4307</t>
4308<t>
4309  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4310  <list style="symbols"> 
4311    <t>
4312      Replace string literals when the string really is case-sensitive (method).
4313    </t>
4314  </list>
4315</t>
4316</section>
4317
4318<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
4319<t>
4320  Closed issues:
4321  <list style="symbols"> 
4322    <t>
4323      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
4324      "OPTIONS request bodies"
4325    </t>
4326    <t>
4327      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
4328      "Description of CONNECT should refer to RFC2817"
4329    </t>
4330    <t>
4331      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
4332      "Location Content-Location reference request/response mixup"
4333    </t>
4334  </list>
4335</t>
4336<t>
4337  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
4338  <list style="symbols"> 
4339    <t>
4340      Added initial proposal for registration process, plus initial
4341      content (non-HTTP/1.1 methods to be added by a separate specification).
4342    </t>
4343  </list>
4344</t>
4345</section>
4346
4347<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
4348<t>
4349  Closed issues:
4350  <list style="symbols"> 
4351    <t>
4352      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
4353      "Content-*"
4354    </t>
4355    <t>
4356      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
4357      "RFC 2822 is updated by RFC 5322"
4358    </t>
4359  </list>
4360</t>
4361<t>
4362  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4363  <list style="symbols"> 
4364    <t>
4365      Use "/" instead of "|" for alternatives.
4366    </t>
4367    <t>
4368      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
4369      whitespace ("OWS") and required whitespace ("RWS").
4370    </t>
4371    <t>
4372      Rewrite ABNFs to spell out whitespace rules, factor out
4373      header field value format definitions.
4374    </t>
4375  </list>
4376</t>
4377</section>
4378
4379<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
4380<t>
4381  Closed issues:
4382  <list style="symbols"> 
4383    <t>
4384      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
4385      "Reason-Phrase BNF"
4386    </t>
4387  </list>
4388</t>
4389<t>
4390  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4391  <list style="symbols"> 
4392    <t>
4393      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
4394    </t>
4395  </list>
4396</t>
4397</section>
4398
4399<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
4400<t>
4401  Closed issues:
4402  <list style="symbols"> 
4403    <t>
4404      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
4405      "Clarify when Referer is sent"
4406    </t>
4407    <t>
4408      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
4409      "status codes vs methods"
4410    </t>
4411    <t>
4412      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
4413      "Do not require "updates" relation for specs that register status codes or method names"
4414    </t>
4415  </list>
4416</t>
4417</section>
4418
4419<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
4420<t>
4421  Closed issues:
4422  <list style="symbols"> 
4423    <t>
4424      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
4425      "Idempotency"
4426    </t>
4427    <t>
4428      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
4429      "TRACE security considerations"
4430    </t>
4431    <t>
4432      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
4433      "Clarify rules for determining what entities a response carries"
4434    </t>
4435    <t>
4436      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
4437      "update note citing RFC 1945 and 2068"
4438    </t>
4439    <t>
4440      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
4441      "update note about redirect limit"
4442    </t>
4443    <t>
4444      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
4445      "Location header ABNF should use 'URI'"
4446    </t>
4447    <t>
4448      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
4449      "fragments in Location vs status 303"
4450    </t>
4451    <t>
4452      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
4453      "move IANA registrations for optional status codes"
4454    </t>
4455  </list>
4456</t>
4457<t>
4458  Partly resolved issues:
4459  <list style="symbols"> 
4460    <t>
4461      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
4462      "Are OPTIONS and TRACE safe?"
4463    </t>
4464  </list>
4465</t>
4466</section>
4467
4468<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
4469<t>
4470  Closed issues:
4471  <list style="symbols"> 
4472    <t>
4473      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
4474      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
4475      status codes when fixing this previously)
4476    </t>
4477  </list>
4478</t>
4479</section>
4480
4481<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
4482<t>
4483  Closed issues:
4484  <list style="symbols"> 
4485    <t>
4486      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4487      "Fragment combination / precedence during redirects"
4488    </t>
4489  </list>
4490</t>
4491<t>
4492  Partly resolved issues:
4493  <list style="symbols"> 
4494    <t>
4495      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
4496      "Location header payload handling"
4497    </t>
4498    <t>
4499      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
4500      "Term for the requested resource's URI"
4501    </t>
4502  </list>
4503</t>
4504</section>
4505
4506<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
4507<t>
4508  Closed issues:
4509  <list style="symbols"> 
4510    <t>
4511      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
4512      "Clarify 'Requested Variant'"
4513    </t>
4514    <t>
4515      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
4516      "Clarify entity / representation / variant terminology"
4517    </t>
4518    <t>
4519      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/139"/>:
4520      "Methods and Caching"
4521    </t>
4522    <t>
4523      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/190"/>:
4524      "OPTIONS vs Max-Forwards"
4525    </t>
4526    <t>
4527      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/199"/>:
4528      "Status codes and caching"
4529    </t>
4530    <t>
4531      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
4532      "consider removing the 'changes from 2068' sections"
4533    </t>
4534  </list>
4535</t>
4536</section>
4537
4538<section title="Since draft-ietf-httpbis-p2-semantics-11" anchor="changes.since.11">
4539<t>
4540  Closed issues:
4541  <list style="symbols"> 
4542    <t>
4543      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/229"/>:
4544      "Considerations for new status codes"
4545    </t>
4546    <t>
4547      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/230"/>:
4548      "Considerations for new methods"
4549    </t>
4550    <t>
4551      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/232"/>:
4552      "User-Agent guidelines" (relating to the 'User-Agent' header field)
4553    </t>
4554  </list>
4555</t>
4556</section>
4557
4558<section title="Since draft-ietf-httpbis-p2-semantics-12" anchor="changes.since.12">
4559<t>
4560  Closed issues:
4561  <list style="symbols"> 
4562    <t>
4563      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4564      "Fragment combination / precedence during redirects" (added warning
4565      about having a fragid on the redirect may cause inconvenience in
4566      some cases)
4567    </t>
4568    <t>
4569      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/79"/>:
4570      "Content-* vs. PUT"
4571    </t>
4572    <t>
4573      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/88"/>:
4574      "205 Bodies"
4575    </t>
4576    <t>
4577      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/102"/>:
4578      "Understanding Content-* on non-PUT requests"
4579    </t>
4580    <t>
4581      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
4582      "Content-*"
4583    </t>
4584    <t>
4585      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/104"/>:
4586      "Header type defaulting"
4587    </t>
4588    <t>
4589      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
4590      "PUT - 'store under' vs 'store at'"
4591    </t>
4592    <t>
4593      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/137"/>:
4594      "duplicate ABNF for Reason-Phrase"
4595    </t>
4596    <t>
4597      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/180"/>:
4598      "Note special status of Content-* prefix in header registration procedures"
4599    </t>
4600    <t>
4601      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/203"/>:
4602      "Max-Forwards vs extension methods"
4603    </t>
4604    <t>
4605      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/213"/>:
4606      "What is the value space of HTTP status codes?" (actually fixed in
4607      draft-ietf-httpbis-p2-semantics-11)
4608    </t>
4609    <t>
4610      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/224"/>:
4611      "Header Classification"
4612    </t>
4613    <t>
4614      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/225"/>:
4615      "PUT side effect: invalidation or just stale?"
4616    </t>
4617    <t>
4618      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/226"/>:
4619      "proxies not supporting certain methods"
4620    </t>
4621    <t>
4622      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/239"/>:
4623      "Migrate CONNECT from RFC2817 to p2"
4624    </t>
4625    <t>
4626      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/240"/>:
4627      "Migrate Upgrade details from RFC2817"
4628    </t>
4629    <t>
4630      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/267"/>:
4631      "clarify PUT semantics'"
4632    </t>
4633    <t>
4634      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/275"/>:
4635      "duplicate ABNF for 'Method'"
4636    </t>
4637    <t>
4638      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4639      "untangle ABNFs for header fields"
4640    </t>
4641  </list>
4642</t>
4643</section>
4644
4645<section title="Since draft-ietf-httpbis-p2-semantics-13" anchor="changes.since.13">
4646<t>
4647  Closed issues:
4648  <list style="symbols"> 
4649    <t>
4650      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4651      "untangle ABNFs for header fields"
4652    </t>
4653    <t>
4654      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/251"/>:
4655      "message-body in CONNECT request"
4656    </t>
4657  </list>
4658</t>
4659</section>
4660
4661<section title="Since draft-ietf-httpbis-p2-semantics-14" anchor="changes.since.14">
4662<t>
4663  Closed issues:
4664  <list style="symbols"> 
4665    <t>
4666      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/255"/>:
4667      "Clarify status code for rate limiting"
4668    </t>
4669    <t>
4670      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/294"/>:
4671      "clarify 403 forbidden"
4672    </t>
4673    <t>
4674      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/296"/>:
4675      "Clarify 203 Non-Authoritative Information"
4676    </t>
4677    <t>
4678      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/298"/>:
4679      "update default reason phrase for 413"
4680    </t>
4681  </list>
4682</t>
4683</section>
4684
4685<section title="Since draft-ietf-httpbis-p2-semantics-15" anchor="changes.since.15">
4686<t>
4687  Closed issues:
4688  <list style="symbols"> 
4689    <t>
4690      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/285"/>:
4691      "Strength of requirements on Accept re: 406"
4692    </t>
4693    <t>
4694      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/303"/>:
4695      "400 response isn't generic"
4696    </t>
4697  </list>
4698</t>
4699</section>
4700
4701<section title="Since draft-ietf-httpbis-p2-semantics-16" anchor="changes.since.16">
4702<t>
4703  Closed issues:
4704  <list style="symbols"> 
4705    <t>
4706      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/160"/>:
4707      "Redirects and non-GET methods"
4708    </t>
4709    <t>
4710      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/186"/>:
4711      "Document HTTP's error-handling philosophy"
4712    </t>
4713    <t>
4714      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/231"/>:
4715      "Considerations for new headers"
4716    </t>
4717    <t>
4718      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/310"/>:
4719      "clarify 303 redirect on HEAD"
4720    </t>
4721  </list>
4722</t>
4723</section>
4724
4725<section title="Since draft-ietf-httpbis-p2-semantics-17" anchor="changes.since.17">
4726<t>
4727  Closed issues:
4728  <list style="symbols"> 
4729    <t>
4730      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
4731      "Location header payload handling"
4732    </t>
4733    <t>
4734      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/255"/>:
4735      "Clarify status code for rate limiting" (change backed out because
4736      a new status code is being defined for this purpose)
4737    </t>
4738    <t>
4739      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/312"/>:
4740      "should there be a permanent variant of 307"
4741    </t>
4742    <t>
4743      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/325"/>:
4744      "When are Location's semantics triggered?"
4745    </t>
4746    <t>
4747      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/327"/>:
4748      "'expect' grammar missing OWS"
4749    </t>
4750    <t>
4751      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/329"/>:
4752      "header field considerations: quoted-string vs use of double quotes"
4753    </t>
4754  </list>
4755</t>
4756</section>
4757
4758<section title="Since draft-ietf-httpbis-p2-semantics-18" anchor="changes.since.18">
4759<t>
4760  Closed issues:
4761  <list style="symbols"> 
4762    <t>
4763      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/332"/>:
4764      "relax requirements on hypertext in 3/4/5xx error responses"
4765    </t>
4766    <t>
4767      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/333"/>:
4768      "example for 426 response should have a payload"
4769    </t>
4770  </list>
4771</t>
4772</section>
4773
4774</section>
4775
4776</back>
4777</rfc>
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