source: draft-ietf-httpbis/latest/p2-semantics.xml @ 1448

Last change on this file since 1448 was 1448, checked in by julian.reschke@…, 8 years ago

add advice on parameter syntax (token/quoted-string) (see #231)

  • Property svn:eol-style set to native
File size: 191.5 KB
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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 "October">
16  <!ENTITY ID-YEAR "2011">
17  <!ENTITY mdash "&#8212;">
18  <!ENTITY notation                   "<xref target='Part1' x:rel='#notation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
19  <!ENTITY acks                       "<xref target='Part1' x:rel='#acks' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY messaging                  "<xref target='Part1' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY payload                    "<xref target='Part3' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY conditional                "<xref target='Part4' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23  <!ENTITY range                      "<xref target='Part5' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
24  <!ENTITY caching                    "<xref target='Part6' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
25  <!ENTITY auth                       "<xref target='Part7' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
26  <!ENTITY content-negotiation        "<xref target='Part3' x:rel='#content.negotiation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
27  <!ENTITY agent-driven-negotiation    "<xref target='Part3' x:rel='#agent-driven.negotiation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
28  <!ENTITY notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
29  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY field-rules                "<xref target='Part1' x:rel='#field.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY uri                        "<xref target='Part1' x:rel='#uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY effective-request-uri      "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY intermediaries             "<xref target='Part1' x:rel='#intermediaries' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY chunked-encoding           "<xref target='Part1' x:rel='#chunked.encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY request-target             "<xref target='Part1' x:rel='#request-target' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
42  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
43  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
44  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
45  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
46  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
47  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
48  <!ENTITY header-connection          "<xref target='Part1' x:rel='#header.connection' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
49  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
50  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
51  <!ENTITY header-content-type        "<xref target='Part3' x:rel='#header.content-type' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
52  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
53  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
54  <!ENTITY header-fields              "<xref target='Part1' x:rel='#header.fields' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
55  <!ENTITY header-host                "<xref target='Part1' x:rel='#header.host' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
56  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
57  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
58  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
59  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
60  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
61  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
62  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
63  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
64  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
65  <!ENTITY header-upgrade             "<xref target='Part1' x:rel='#header.upgrade' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
66  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.te' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
67  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
68  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
69  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
70  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
71  <!ENTITY media-types                "<xref target='Part3' x:rel='#media.types' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
72  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
73  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
74  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='#internet.media.type.message.http' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
75  <!ENTITY status-206                 "<xref target='Part5' x:rel='#status.206' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
76  <!ENTITY status-304                 "<xref target='Part4' x:rel='#status.304' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
77  <!ENTITY status-401                 "<xref target='Part7' x:rel='#status.401' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
78  <!ENTITY status-407                 "<xref target='Part7' x:rel='#status.407' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
79  <!ENTITY status-412                 "<xref target='Part4' x:rel='#status.412' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
80  <!ENTITY status-416                 "<xref target='Part5' x:rel='#status.416' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
81  <!ENTITY p3-header-fields           "<xref target='Part3' x:rel='#header.field.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
82  <!ENTITY p4-status-codes            "<xref target='Part4' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
83  <!ENTITY p5-status-codes            "<xref target='Part5' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
84  <!ENTITY p7-status-codes            "<xref target='Part7' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
85  <!ENTITY p6-heuristic               "<xref target='Part6' x:rel='#heuristic.freshness' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
86  <!ENTITY p6-explicit                "<xref target='Part6' x:rel='#calculating.freshness.lifetime' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
87  <!ENTITY p6-invalid                 "<xref target='Part6' x:rel='#invalidation.after.updates.or.deletions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
88]>
89<?rfc toc="yes" ?>
90<?rfc symrefs="yes" ?>
91<?rfc sortrefs="yes" ?>
92<?rfc compact="yes"?>
93<?rfc subcompact="no" ?>
94<?rfc linkmailto="no" ?>
95<?rfc editing="no" ?>
96<?rfc comments="yes"?>
97<?rfc inline="yes"?>
98<?rfc rfcedstyle="yes"?>
99<?rfc-ext allow-markup-in-artwork="yes" ?>
100<?rfc-ext include-references-in-index="yes" ?>
101<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
102     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
103     xmlns:x='http://purl.org/net/xml2rfc/ext'
104     xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
105<front>
106
107  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
108
109  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
110    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
111    <address>
112      <postal>
113        <street>345 Park Ave</street>
114        <city>San Jose</city>
115        <region>CA</region>
116        <code>95110</code>
117        <country>USA</country>
118      </postal>
119      <email>fielding@gbiv.com</email>
120      <uri>http://roy.gbiv.com/</uri>
121    </address>
122  </author>
123
124  <author initials="J." surname="Gettys" fullname="Jim Gettys">
125    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
126    <address>
127      <postal>
128        <street>21 Oak Knoll Road</street>
129        <city>Carlisle</city>
130        <region>MA</region>
131        <code>01741</code>
132        <country>USA</country>
133      </postal>
134      <email>jg@freedesktop.org</email>
135      <uri>http://gettys.wordpress.com/</uri>
136    </address>
137  </author>
138 
139  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
140    <organization abbrev="HP">Hewlett-Packard Company</organization>
141    <address>
142      <postal>
143        <street>HP Labs, Large Scale Systems Group</street>
144        <street>1501 Page Mill Road, MS 1177</street>
145        <city>Palo Alto</city>
146        <region>CA</region>
147        <code>94304</code>
148        <country>USA</country>
149      </postal>
150      <email>JeffMogul@acm.org</email>
151    </address>
152  </author>
153
154  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
155    <organization abbrev="Microsoft">Microsoft Corporation</organization>
156    <address>
157      <postal>
158        <street>1 Microsoft Way</street>
159        <city>Redmond</city>
160        <region>WA</region>
161        <code>98052</code>
162        <country>USA</country>
163      </postal>
164      <email>henrikn@microsoft.com</email>
165    </address>
166  </author>
167
168  <author initials="L." surname="Masinter" fullname="Larry Masinter">
169    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
170    <address>
171      <postal>
172        <street>345 Park Ave</street>
173        <city>San Jose</city>
174        <region>CA</region>
175        <code>95110</code>
176        <country>USA</country>
177      </postal>
178      <email>LMM@acm.org</email>
179      <uri>http://larry.masinter.net/</uri>
180    </address>
181  </author>
182 
183  <author initials="P." surname="Leach" fullname="Paul J. Leach">
184    <organization abbrev="Microsoft">Microsoft Corporation</organization>
185    <address>
186      <postal>
187        <street>1 Microsoft Way</street>
188        <city>Redmond</city>
189        <region>WA</region>
190        <code>98052</code>
191      </postal>
192      <email>paulle@microsoft.com</email>
193    </address>
194  </author>
195   
196  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
197    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
198    <address>
199      <postal>
200        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
201        <street>The Stata Center, Building 32</street>
202        <street>32 Vassar Street</street>
203        <city>Cambridge</city>
204        <region>MA</region>
205        <code>02139</code>
206        <country>USA</country>
207      </postal>
208      <email>timbl@w3.org</email>
209      <uri>http://www.w3.org/People/Berners-Lee/</uri>
210    </address>
211  </author>
212
213  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
214    <organization abbrev="W3C">World Wide Web Consortium</organization>
215    <address>
216      <postal>
217        <street>W3C / ERCIM</street>
218        <street>2004, rte des Lucioles</street>
219        <city>Sophia-Antipolis</city>
220        <region>AM</region>
221        <code>06902</code>
222        <country>France</country>
223      </postal>
224      <email>ylafon@w3.org</email>
225      <uri>http://www.raubacapeu.net/people/yves/</uri>
226    </address>
227  </author>
228
229  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
230    <organization abbrev="greenbytes">greenbytes GmbH</organization>
231    <address>
232      <postal>
233        <street>Hafenweg 16</street>
234        <city>Muenster</city><region>NW</region><code>48155</code>
235        <country>Germany</country>
236      </postal>
237      <phone>+49 251 2807760</phone>
238      <facsimile>+49 251 2807761</facsimile>
239      <email>julian.reschke@greenbytes.de</email>
240      <uri>http://greenbytes.de/tech/webdav/</uri>
241    </address>
242  </author>
243
244  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
245  <workgroup>HTTPbis Working Group</workgroup>
246
247<abstract>
248<t>
249   The Hypertext Transfer Protocol (HTTP) is an application-level protocol for
250   distributed, collaborative, hypertext information systems. HTTP has been in
251   use by the World Wide Web global information initiative since 1990. This
252   document is Part 2 of the seven-part specification that defines the protocol
253   referred to as "HTTP/1.1" and, taken together, obsoletes RFC 2616.
254</t>
255<t>
256   Part 2 defines the semantics of HTTP messages as expressed by request
257   methods, request header fields, response status codes, and response header
258   fields.
259</t>
260</abstract>
261
262<note title="Editorial Note (To be removed by RFC Editor)">
263  <t>
264    Discussion of this draft should take place on the HTTPBIS working group
265    mailing list (ietf-http-wg@w3.org), which is archived at
266    <eref target="http://lists.w3.org/Archives/Public/ietf-http-wg/"/>.
267  </t>
268  <t>
269    The current issues list is at
270    <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/> and related
271    documents (including fancy diffs) can be found at
272    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
273  </t>
274  <t>
275    The changes in this draft are summarized in <xref target="changes.since.16"/>.
276  </t>
277</note>
278</front>
279<middle>
280<section title="Introduction" anchor="introduction">
281<t>
282   This document defines HTTP/1.1 request and response semantics.  Each HTTP
283   message, as defined in &messaging;, is in the form of either a request or
284   a response.  An HTTP server listens on a connection for HTTP requests and
285   responds to each request, in the order received on that connection, with
286   one or more HTTP response messages.  This document defines the commonly
287   agreed upon semantics of the HTTP uniform interface, the intentions defined
288   by each request method, and the various response messages that might be
289   expected as a result of applying that method to the target resource.
290</t>
291<t>
292   This document is currently disorganized in order to minimize the changes
293   between drafts and enable reviewers to see the smaller errata changes.
294   A future draft will reorganize the sections to better reflect the content.
295   In particular, the sections will be ordered according to the typical
296   processing of an HTTP request message (after message parsing): resource
297   mapping, methods, request modifying header fields, response status,
298   status modifying header fields, and resource metadata.  The current mess
299   reflects how widely dispersed these topics and associated requirements
300   had become in <xref target="RFC2616"/>.
301</t>
302
303<section title="Requirements" anchor="intro.requirements">
304<t>
305   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
306   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
307   document are to be interpreted as described in <xref target="RFC2119"/>.
308</t>
309<t>
310   An implementation is not compliant if it fails to satisfy one or more
311   of the "MUST" or "REQUIRED" level requirements for the protocols it
312   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
313   level and all the "SHOULD" level requirements for its protocols is said
314   to be "unconditionally compliant"; one that satisfies all the "MUST"
315   level requirements but not all the "SHOULD" level requirements for its
316   protocols is said to be "conditionally compliant".
317</t>
318</section>
319
320<section title="Syntax Notation" anchor="notation">
321  <x:anchor-alias value="CR"/>
322  <x:anchor-alias value="DIGIT"/>
323  <x:anchor-alias value="LF"/>
324  <x:anchor-alias value="HTAB"/>
325  <x:anchor-alias value="VCHAR"/>
326  <x:anchor-alias value="SP"/>
327<t>
328  This specification uses the ABNF syntax defined in &notation; (which
329  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
330  <xref target="collected.abnf"/> shows the collected ABNF, with the list
331  rule expanded.
332</t>
333<t>
334  The following core rules are included by
335  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
336  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
337  DIGIT (decimal 0-9), DQUOTE (double quote),
338  HEXDIG (hexadecimal 0-9/A-F/a-f), HTAB (horizontal tab), LF (line feed),
339  OCTET (any 8-bit sequence of data), SP (space), and
340  VCHAR (any visible US-ASCII character).
341</t>
342
343<section title="Core Rules" anchor="core.rules">
344  <x:anchor-alias value="obs-text"/>
345  <x:anchor-alias value="quoted-string"/>
346  <x:anchor-alias value="token"/>
347  <x:anchor-alias value="OWS"/>
348  <x:anchor-alias value="RWS"/>
349<t>
350  The core rules below are defined in <xref target="Part1"/>:
351</t>
352<figure><artwork type="abnf2616">
353  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
354  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
355  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
356  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &field-rules;&gt;
357  <x:ref>token</x:ref>         = &lt;token, defined in &field-rules;&gt;
358</artwork></figure>
359</section>
360
361<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
362  <x:anchor-alias value="absolute-URI"/>
363  <x:anchor-alias value="comment"/>
364  <x:anchor-alias value="partial-URI"/>
365  <x:anchor-alias value="product"/>
366  <x:anchor-alias value="URI-reference"/>
367<t>
368  The ABNF rules below are defined in other parts:
369</t>
370<figure><!--Part1--><artwork type="abnf2616">
371  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
372  <x:ref>comment</x:ref>       = &lt;comment, defined in &header-fields;&gt;
373  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
374  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
375  <x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in &uri;&gt;
376</artwork></figure>
377</section>
378</section>
379</section>
380
381<section title="Method" anchor="method">
382  <x:anchor-alias value="Method"/>
383  <x:anchor-alias value="extension-method"/>
384<t>
385   The Method token indicates the request method to be performed on the target
386   resource (&effective-request-uri;). The method is case-sensitive.
387</t>
388<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/>
389  <x:ref>Method</x:ref>         = <x:ref>token</x:ref>
390</artwork></figure>
391<t>
392   The list of methods allowed by a resource can be specified in an
393   Allow header field (<xref target="header.allow"/>). The status code of the response
394   always notifies the client whether a method is currently allowed on a
395   resource, since the set of allowed methods can change dynamically. An
396   origin server &SHOULD; respond with the status code 405 (Method Not Allowed)
397   if the method is known by the origin server but not allowed for the
398   resource, and 501 (Not Implemented) if the method is
399   unrecognized or not implemented by the origin server. The methods GET
400   and HEAD &MUST; be supported by all general-purpose servers. All other
401   methods are &OPTIONAL;; however, if the above methods are implemented,
402   they &MUST; be implemented with the same semantics as those specified
403   in <xref target="method.definitions"/>.
404</t>
405
406<section title="Overview of Methods" anchor="overview.of.methods">
407<t>
408  The methods listed below are defined in <xref target="method.definitions"/>.
409</t>
410<texttable align="left">
411  <ttcol>Method Name</ttcol><ttcol>Defined in...</ttcol>
412 
413  <c>OPTIONS</c> <c><xref target="OPTIONS"/></c>
414  <c>GET</c> <c><xref target="GET"/></c>
415  <c>HEAD</c> <c><xref target="HEAD"/></c>
416  <c>POST</c> <c><xref target="POST"/></c>
417  <c>PUT</c> <c><xref target="PUT"/></c>
418  <c>DELETE</c> <c><xref target="DELETE"/></c>
419  <c>TRACE</c> <c><xref target="TRACE"/></c>
420  <c>CONNECT</c> <c><xref target="CONNECT"/></c>
421</texttable>
422<t>
423  Note that this list is not exhaustive &mdash; it does not include request methods defined
424  in other specifications.
425</t>
426</section>
427
428<section title="Method Registry" anchor="method.registry">
429<t>
430  The HTTP Method Registry defines the name space for the Method token in the
431  Request line of an HTTP request.
432</t>
433<t>
434  Registrations &MUST; include the following fields:
435  <list style="symbols">
436    <t>Method Name (see <xref target="method"/>)</t>
437    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
438    <t>Pointer to specification text</t>
439  </list>
440</t>
441<t>
442  Values to be added to this name space are subject to IETF review
443  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
444</t>
445<t>
446  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
447</t>
448
449<section title="Considerations for New Methods" anchor="considerations.for.new.methods">
450<t>
451   When it is necessary to express new semantics for a HTTP request that
452   aren't specific to a single application or media type, and currently defined
453   methods are inadequate, it may be appropriate to register a new method.
454</t>
455<t>
456   HTTP methods are generic; that is, they are potentially applicable to any
457   resource, not just one particular media type, "type" of resource, or
458   application. As such, it is preferred that new HTTP methods be registered
459   in a document that isn't specific to a single application, so that this is
460   clear.
461</t>
462<t>
463   Due to the parsing rules defined in &message-body;, definitions of HTTP
464   methods cannot prohibit the presence of a message-body on either the request
465   or the response message (with responses to HEAD requests being the single
466   exception). Definitions of new methods cannot change this rule, but they can
467   specify that only zero-length bodies (as opposed to absent bodies) are allowed.
468</t>
469<t>
470   New method definitions need to indicate whether they are safe (<xref
471   target="safe.methods"/>), what semantics (if any) the request body has,
472   and whether they are idempotent (<xref target="idempotent.methods"/>).
473   They also need to state whether they can be cached (&caching;); in
474   particular what conditions a cache may store the response, and under what
475   conditions such a stored response may be used to satisfy a subsequent
476   request.
477</t>
478</section>
479
480</section>
481</section>
482
483<section title="Header Fields" anchor="header.fields">
484<t>
485   Header fields are key value pairs that can be used to communicate data about
486   the message, its payload, the target resource, or about the connection
487   itself (i.e., control data).  See &header-fields; for a general definition
488   of their syntax.
489</t>
490
491<section title="Considerations for Creating Header Fields" anchor="considerations.for.creating.header.fields">
492<t>
493   New header fields are registered using the procedures described in
494   <xref target="RFC3864"/>.
495</t>
496<t>
497   The requirements for header field names are defined in
498   <xref target="RFC3864" x:fmt="of" x:sec="4.1"/>.  Authors of specifications
499   defining new fields are advised to keep the name as short as practical, and
500   not to prefix them with "X-" if they are to be registered (either
501   immediately or in the future).
502</t>
503<t>
504   New header field values typically have their syntax defined using ABNF
505   (<xref target="RFC5234"/>), using the extensions defined in &notation-abnf;
506   as necessary, and are usually constrained to the range of ASCII characters.
507   Header fields needing a greater range of characters can use an encoding
508   such as the one defined in <xref target="RFC5987"/>.
509</t>
510<t>
511   Because commas (",") are used as a generic delimiter between field-values,
512   they need to be treated with care if they are allowed in the field-value's
513   payload. Typically, components that might contain a comma are protected with
514   double-quotes using the quoted-string ABNF production (&field-rules;).
515</t>
516<t>
517   For example, a textual date and a URI (either of which might contain a comma)
518   could be safely carried in field-values like these:
519</t>
520<figure><artwork type="example">
521  Example-URI-Field: "http://example.com/a.html,foo",
522                     "http://without-a-comma.example.com/"
523  Example-Date-Field: "Sat, 04 May 1996", "Wed, 14 Sep 2005"
524</artwork></figure>
525<t>
526   Many header fields use a format including named parameters (for instance,
527   Content-Type, defined in &header-content-type;). Allowing both unquoted
528   (token) and quoted (quoted-string) syntax for the parameter value enables
529   recipients to use existing parser components. Also, the meaning of a value
530   ought to be independent of the syntax variant used for it (for an example,
531   see the notes on parameter handling for media types in &media-types;).
532</t>
533<t>
534   Authors of specifications defining new header fields are advised to consider
535   documenting:
536  <list style="symbols">
537    <x:lt>
538      <t>Whether the field is a single value, or whether it can be a list
539      (delimited by commas; see &header-fields;).</t>
540      <t>If it does not use the list syntax, how to treat messages where the
541      header field occurs multiple times (a sensible default would be to ignore
542      the header field, but this might not always be the right choice).</t>
543    </x:lt>
544    <x:lt><t>Under what conditions the header field can be used; e.g., only in
545    responses or requests, in all messages, only on responses to a particular
546    request method.</t></x:lt>
547    <x:lt><t>Whether it is appropriate to list the field-name in the Connection header
548    (i.e., if the header is to be hop-by-hop, see &header-connection;).</t></x:lt>
549    <x:lt><t>Under what conditions intermediaries are allowed to modify the header
550    field's value, insert or delete it.</t></x:lt>
551    <x:lt><t>How the header might interact with caching (see <xref target="Part6"/>).</t></x:lt>
552    <x:lt><t>Whether the header field is useful or allowable in trailers (see
553    &chunked-encoding;).</t></x:lt>
554    <x:lt><t>Whether the header field should be preserved across redirects.</t></x:lt>
555  </list>
556</t>
557</section>
558
559<section title="Request Header Fields" anchor="request.header.fields">
560  <x:anchor-alias value="request-header"/>
561<t>
562   The request header fields allow the client to pass additional
563   information about the request, and about the client itself, to the
564   server. These fields act as request modifiers, with semantics
565   equivalent to the parameters on a programming language method
566   invocation.
567</t>
568<texttable align="left">
569  <ttcol>Header Field Name</ttcol>
570  <ttcol>Defined in...</ttcol>
571
572  <c>Accept</c> <c>&header-accept;</c>
573  <c>Accept-Charset</c> <c>&header-accept-charset;</c>
574  <c>Accept-Encoding</c> <c>&header-accept-encoding;</c>
575  <c>Accept-Language</c> <c>&header-accept-language;</c>
576  <c>Authorization</c> <c>&header-authorization;</c>
577  <c>Expect</c> <c><xref target="header.expect"/></c>
578  <c>From</c> <c><xref target="header.from"/></c>
579  <c>Host</c> <c>&header-host;</c>
580  <c>If-Match</c> <c>&header-if-match;</c>
581  <c>If-Modified-Since</c> <c>&header-if-modified-since;</c>
582  <c>If-None-Match</c> <c>&header-if-none-match;</c>
583  <c>If-Range</c> <c>&header-if-range;</c>
584  <c>If-Unmodified-Since</c> <c>&header-if-unmodified-since;</c>
585  <c>Max-Forwards</c> <c><xref target="header.max-forwards"/></c>
586  <c>Proxy-Authorization</c> <c>&header-proxy-authorization;</c>
587  <c>Range</c> <c>&header-range;</c>
588  <c>Referer</c> <c><xref target="header.referer"/></c>
589  <c>TE</c> <c>&header-te;</c>
590  <c>User-Agent</c> <c><xref target="header.user-agent"/></c>
591</texttable>
592</section>
593
594<section title="Response Header Fields" anchor="response.header.fields">
595  <x:anchor-alias value="response-header"/>
596<t>
597   The response header fields allow the server to pass additional
598   information about the response which cannot be placed in the Status-Line.
599   These header fields give information about the server and about
600   further access to the target resource (&effective-request-uri;).
601</t>
602<texttable align="left">
603  <ttcol>Header Field Name</ttcol><ttcol>Defined in...</ttcol>
604
605  <c>Accept-Ranges</c> <c>&header-accept-ranges;</c>
606  <c>Age</c> <c>&header-age;</c>
607  <c>Allow</c> <c><xref target="header.allow"/></c>
608  <c>Date</c> <c><xref target="header.date"/></c>
609  <c>ETag</c> <c>&header-etag;</c>
610  <c>Location</c> <c><xref target="header.location"/></c>
611  <c>Proxy-Authenticate</c> <c>&header-proxy-authenticate;</c>
612  <c>Retry-After</c> <c><xref target="header.retry-after"/></c>
613  <c>Server</c> <c><xref target="header.server"/></c>
614  <c>Vary</c> <c>&header-vary;</c>
615  <c>WWW-Authenticate</c> <c>&header-www-authenticate;</c>
616</texttable>
617</section>
618
619</section>
620
621<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
622  <x:anchor-alias value="Reason-Phrase"/>
623  <x:anchor-alias value="Status-Code"/>
624  <x:anchor-alias value="extension-code"/>
625<t>
626   The Status-Code element is a 3-digit integer result code of the attempt to
627   understand and satisfy the request.
628</t>
629<t>
630   The Reason-Phrase is intended to give a short textual description of the
631   Status-Code and is intended for a human user. The client does not need
632   to examine or display the Reason-Phrase.
633</t>
634<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"/>
635  <x:ref>Status-Code</x:ref>    = 3<x:ref>DIGIT</x:ref>
636  <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> )
637</artwork></figure>
638<t>
639   HTTP status codes are extensible. HTTP applications are not required
640   to understand the meaning of all registered status codes, though such
641   understanding is obviously desirable. However, applications &MUST;
642   understand the class of any status code, as indicated by the first
643   digit, and treat any unrecognized response as being equivalent to the
644   x00 status code of that class, with the exception that an
645   unrecognized response &MUST-NOT; be cached. For example, if an
646   unrecognized status code of 431 is received by the client, it can
647   safely assume that there was something wrong with its request and
648   treat the response as if it had received a 400 status code. In such
649   cases, user agents &SHOULD; present to the user the representation enclosed
650   with the response, since that representation is likely to include human-readable
651   information which will explain the unusual status.
652</t>
653
654<section title="Overview of Status Codes" anchor="overview.of.status.codes">
655<t> 
656   The status codes listed below are defined in <xref target="status.codes"/>
657   of this specification, &p4-status-codes;, &p5-status-codes;, and &p7-status-codes;.
658   The reason phrases listed here are only recommendations &mdash; they can be
659   replaced by local equivalents without affecting the protocol.
660</t>
661<texttable align="left">
662  <ttcol>Status-Code</ttcol>
663  <ttcol>Reason-Phrase</ttcol>
664  <ttcol>Defined in...</ttcol>
665 
666  <c>100</c> <c>Continue</c> <c><xref target="status.100"/></c>
667  <c>101</c> <c>Switching Protocols</c> <c><xref target="status.101"/></c>
668
669  <c>200</c> <c>OK</c> <c><xref target="status.200"/></c>
670  <c>201</c> <c>Created</c> <c><xref target="status.201"/></c>
671  <c>202</c> <c>Accepted</c> <c><xref target="status.202"/></c>
672  <c>203</c> <c>Non-Authoritative Information</c> <c><xref target="status.203"/></c>
673  <c>204</c> <c>No Content</c> <c><xref target="status.204"/></c>
674  <c>205</c> <c>Reset Content</c> <c><xref target="status.205"/></c>
675  <c>206</c> <c>Partial Content</c> <c>&status-206;</c>
676
677  <c>300</c> <c>Multiple Choices</c> <c><xref target="status.300"/></c>
678  <c>301</c> <c>Moved Permanently</c> <c><xref target="status.301"/></c>
679  <c>302</c> <c>Found</c> <c><xref target="status.302"/></c>
680  <c>303</c> <c>See Other</c> <c><xref target="status.303"/></c>
681  <c>304</c> <c>Not Modified</c> <c>&status-304;</c>
682  <c>305</c> <c>Use Proxy</c> <c><xref target="status.305"/></c>
683  <c>307</c> <c>Temporary Redirect</c> <c><xref target="status.307"/></c>
684
685  <c>400</c> <c>Bad Request</c> <c><xref target="status.400"/></c>
686  <c>401</c> <c>Unauthorized</c> <c>&status-401;</c>
687  <c>402</c> <c>Payment Required</c> <c><xref target="status.402"/></c>
688  <c>403</c> <c>Forbidden</c> <c><xref target="status.403"/></c>
689  <c>404</c> <c>Not Found</c> <c><xref target="status.404"/></c>
690  <c>405</c> <c>Method Not Allowed</c> <c><xref target="status.405"/></c>
691  <c>406</c> <c>Not Acceptable</c> <c><xref target="status.406"/></c>
692  <c>407</c> <c>Proxy Authentication Required</c> <c>&status-407;</c>
693  <c>408</c> <c>Request Time-out</c> <c><xref target="status.408"/></c>
694  <c>409</c> <c>Conflict</c> <c><xref target="status.409"/></c>
695  <c>410</c> <c>Gone</c> <c><xref target="status.410"/></c>
696  <c>411</c> <c>Length Required</c> <c><xref target="status.411"/></c>
697  <c>412</c> <c>Precondition Failed</c> <c>&status-412;</c>
698  <c>413</c> <c>Request Representation Too Large</c> <c><xref target="status.413"/></c>
699  <c>414</c> <c>URI Too Long</c> <c><xref target="status.414"/></c>
700  <c>415</c> <c>Unsupported Media Type</c> <c><xref target="status.415"/></c>
701  <c>416</c> <c>Requested range not satisfiable</c> <c>&status-416;</c>
702  <c>417</c> <c>Expectation Failed</c> <c><xref target="status.417"/></c>
703  <c>426</c> <c>Upgrade Required</c> <c><xref target="status.426"/></c>
704
705  <c>500</c> <c>Internal Server Error</c> <c><xref target="status.500"/></c>
706  <c>501</c> <c>Not Implemented</c> <c><xref target="status.501"/></c>
707  <c>502</c> <c>Bad Gateway</c> <c><xref target="status.502"/></c>
708  <c>503</c> <c>Service Unavailable</c> <c><xref target="status.503"/></c>
709  <c>504</c> <c>Gateway Time-out</c> <c><xref target="status.504"/></c>
710  <c>505</c> <c>HTTP Version not supported</c> <c><xref target="status.505"/></c>
711</texttable>
712<t>
713   Note that this list is not exhaustive &mdash; it does not include
714   extension status codes defined in other specifications.
715</t>
716</section>
717
718<section title="Status Code Registry" anchor="status.code.registry">
719<t>
720  The HTTP Status Code Registry defines the name space for the Status-Code
721  token in the Status-Line of an HTTP response.
722</t>
723<t>
724  Values to be added to this name space are subject to IETF review
725  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
726</t>
727<t>
728  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
729</t>
730
731<section title="Considerations for New Status Codes" anchor="considerations.for.new.status.codes">
732<t>
733   When it is necessary to express new semantics for a HTTP response that
734   aren't specific to a single application or media type, and currently defined
735   status codes are inadequate, a new status code can be registered.
736</t>
737<t>
738   HTTP status codes are generic; that is, they are potentially applicable to
739   any resource, not just one particular media type, "type" of resource, or
740   application. As such, it is preferred that new HTTP status codes be
741   registered in a document that isn't specific to a single application, so
742   that this is clear.
743</t>
744<t>
745   Definitions of new HTTP status codes typically explain the request
746   conditions that produce a response containing the status code (e.g.,
747   combinations of request headers and/or method(s)), along with any
748   interactions with response headers (e.g., those that are required, those
749   that modify the semantics of the response).
750</t>
751<t>
752   New HTTP status codes are required to fall under one of the categories
753   defined in <xref target="status.codes"/>. To allow existing parsers to
754   properly handle them, new status codes cannot disallow a response body,
755   although they can mandate a zero-length response body. They can require the
756   presence of one or more particular HTTP response header(s).
757</t>
758<t>
759   Likewise, their definitions can specify that caches are allowed to use
760   heuristics to determine their freshness (see &caching;; by default, it is
761   not allowed), and can define how to determine the resource which they
762   carry a representation for (see <xref
763   target="identifying.response.associated.with.representation"/>; by default,
764   it is anonymous).
765</t>
766</section>
767
768</section>
769
770</section>
771
772<section title="Representation" anchor="representation">
773<t>
774   Request and Response messages &MAY; transfer a representation if not otherwise
775   restricted by the request method or response status code. A representation
776   consists of metadata (representation header fields) and data (representation
777   body).  When a complete or partial representation is enclosed in an HTTP message,
778   it is referred to as the payload of the message. HTTP representations
779   are defined in &payload;.
780</t>
781<t>
782   A representation body is only present in a message when a message-body is
783   present, as described in &message-body;. The representation body is obtained
784   from the message-body by decoding any Transfer-Encoding that might
785   have been applied to ensure safe and proper transfer of the message.
786</t>
787
788<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
789<t>
790   It is sometimes necessary to determine an identifier for the resource
791   associated with a representation.
792</t>
793<t>
794   An HTTP request representation, when present, is always associated with an
795   anonymous (i.e., unidentified) resource.
796</t>
797<t>
798   In the common case, an HTTP response is a representation of the target
799   resource (see &effective-request-uri;). However, this is not always the
800   case. To determine the URI of the resource a response is associated with,
801   the following rules are used (with the first applicable one being selected):
802</t>
803<t><list style="numbers">
804   <t>If the response status code is 200 or 203 and the request method was GET,
805   the response payload is a representation of the target resource.</t>
806   <t>If the response status code is 204, 206, or 304 and the request method was GET
807   or HEAD, the response payload is a partial representation of the target
808   resource.</t>
809   <t>If the response has a Content-Location header field, and that URI is the same
810   as the effective request URI, the response payload is a representation of the
811   target resource.</t>
812   <t>If the response has a Content-Location header field, and that URI is not the
813   same as the effective request URI, then the response asserts that its
814   payload is a representation of the resource identified by the
815   Content-Location URI. However, such an assertion cannot be trusted unless
816   it can be verified by other means (not defined by HTTP).</t>
817   <t>Otherwise, the response is a representation of an anonymous (i.e.,
818   unidentified) resource.</t>
819</list></t>
820<t>
821  <cref anchor="TODO-req-uri">
822   The comparison function is going to have to be defined somewhere,
823   because we already need to compare URIs for things like cache invalidation.</cref>
824</t>
825</section>
826
827</section>
828
829
830<section title="Method Definitions" anchor="method.definitions">
831<t>
832   The set of common request methods for HTTP/1.1 is defined below. Although
833   this set can be expanded, additional methods cannot be assumed to
834   share the same semantics for separately extended clients and servers.
835</t>
836
837<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
838
839<section title="Safe Methods" anchor="safe.methods">
840<iref item="Safe Methods" primary="true"/>
841<t>
842   Implementors need to be aware that the software represents the user in
843   their interactions over the Internet, and need to allow
844   the user to be aware of any actions they take which might have an
845   unexpected significance to themselves or others.
846</t>
847<t>
848   In particular, the convention has been established that the GET, HEAD,
849   OPTIONS, and TRACE request methods &SHOULD-NOT; have the significance
850   of taking an action other than retrieval. These request methods ought
851   to be considered "<x:dfn anchor="safe">safe</x:dfn>".
852   This allows user agents to represent other methods, such as POST, PUT
853   and DELETE, in a special way, so that the user is made aware of the
854   fact that a possibly unsafe action is being requested.
855</t>
856<t>
857   Naturally, it is not possible to ensure that the server does not
858   generate side-effects as a result of performing a GET request; in
859   fact, some dynamic resources consider that a feature. The important
860   distinction here is that the user did not request the side-effects,
861   so therefore cannot be held accountable for them.
862</t>
863</section>
864
865<section title="Idempotent Methods" anchor="idempotent.methods">
866<iref item="Idempotent Methods" primary="true"/>
867<t>
868   Request methods can also have the property of "idempotence" in that,
869   aside from error or expiration issues, the intended effect of multiple
870   identical requests is the same as for a single request.
871   PUT, DELETE, and all safe request methods are idempotent.
872   It is important to note that idempotence refers only to changes
873   requested by the client: a server is free to change its state due
874   to multiple requests for the purpose of tracking those requests,
875   versioning of results, etc.
876</t>
877</section>
878</section>
879
880<section title="OPTIONS" anchor="OPTIONS">
881  <rdf:Description>
882    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
883  </rdf:Description>
884  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
885  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
886<t>
887   The OPTIONS method requests information about the
888   communication options available on the request/response chain
889   identified by the effective request URI. This method allows a client to
890   determine the options and/or requirements associated with a resource,
891   or the capabilities of a server, without implying a resource action
892   or initiating a resource retrieval.
893</t>
894<t>
895   Responses to the OPTIONS method are not cacheable.
896</t>
897<t>
898   If the OPTIONS request includes a message-body (as indicated by the
899   presence of Content-Length or Transfer-Encoding), then the media type
900   &MUST; be indicated by a Content-Type field. Although this
901   specification does not define any use for such a body, future
902   extensions to HTTP might use the OPTIONS body to make more detailed
903   queries on the server.
904</t>
905<t>
906   If the request-target is an asterisk ("*"), the OPTIONS request is
907   intended to apply to the server in general rather than to a specific
908   resource. Since a server's communication options typically depend on
909   the resource, the "*" request is only useful as a "ping" or "no-op"
910   type of method; it does nothing beyond allowing the client to test
911   the capabilities of the server. For example, this can be used to test
912   a proxy for HTTP/1.1 compliance (or lack thereof).
913</t>
914<t>
915   If the request-target is not an asterisk, the OPTIONS request applies
916   only to the options that are available when communicating with that
917   resource.
918</t>
919<t>
920   A 200 response &SHOULD; include any header fields that indicate
921   optional features implemented by the server and applicable to that
922   resource (e.g., Allow), possibly including extensions not defined by
923   this specification. The response body, if any, &SHOULD; also include
924   information about the communication options. The format for such a
925   body is not defined by this specification, but might be defined by
926   future extensions to HTTP. Content negotiation &MAY; be used to select
927   the appropriate response format. If no response body is included, the
928   response &MUST; include a Content-Length field with a field-value of
929   "0".
930</t>
931<t>
932   The Max-Forwards header field &MAY; be used to target a
933   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
934   If no Max-Forwards field is present in the request, then the forwarded
935   request &MUST-NOT; include a Max-Forwards field.
936</t>
937</section>
938
939<section title="GET" anchor="GET">
940  <rdf:Description>
941    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
942  </rdf:Description>
943  <iref primary="true" item="GET method" x:for-anchor=""/>
944  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
945<t>
946   The GET method requests transfer of a current representation of
947   the target resource.
948</t>
949<t>   
950   If the target resource is a data-producing process, it is the
951   produced data which shall be returned as the representation in the response and not
952   the source text of the process, unless that text happens to be the output of
953   the process.
954</t>
955<t>
956   The semantics of the GET method change to a "conditional GET" if the
957   request message includes an If-Modified-Since, If-Unmodified-Since,
958   If-Match, If-None-Match, or If-Range header field. A conditional GET
959   requests that the representation be transferred only under the
960   circumstances described by the conditional header field(s). The
961   conditional GET request is intended to reduce unnecessary network
962   usage by allowing cached representations to be refreshed without requiring
963   multiple requests or transferring data already held by the client.
964</t>
965<t>
966   The semantics of the GET method change to a "partial GET" if the
967   request message includes a Range header field. A partial GET requests
968   that only part of the representation be transferred, as described in &header-range;.
969   The partial GET request is intended to reduce unnecessary
970   network usage by allowing partially-retrieved representations to be
971   completed without transferring data already held by the client.
972</t>
973<t>
974   Bodies on GET requests have no defined semantics. Note that sending a body
975   on a GET request might cause some existing implementations to reject the
976   request.
977</t>
978<t>
979   The response to a GET request is cacheable and &MAY; be used to satisfy
980   subsequent GET and HEAD requests (see &caching;).
981</t>
982<t>
983   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
984</t>
985</section>
986
987<section title="HEAD" anchor="HEAD">
988  <rdf:Description>
989    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
990  </rdf:Description>
991  <iref primary="true" item="HEAD method" x:for-anchor=""/>
992  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
993<t>
994   The HEAD method is identical to GET except that the server &MUST-NOT;
995   return a message-body in the response. The metadata contained
996   in the HTTP header fields in response to a HEAD request &SHOULD; be identical
997   to the information sent in response to a GET request. This method can
998   be used for obtaining metadata about the representation implied by the
999   request without transferring the representation body. This method is
1000   often used for testing hypertext links for validity, accessibility,
1001   and recent modification.
1002</t>
1003<t>
1004   The response to a HEAD request is cacheable and &MAY; be used to satisfy
1005   a subsequent HEAD request; see &caching;. It also &MAY; be used to update a previously cached
1006   representation from that resource; if the new field values
1007   indicate that the cached representation differs from the current representation (as
1008   would be indicated by a change in Content-Length, ETag
1009   or Last-Modified), then the cache &MUST; treat the cache entry as
1010   stale.
1011</t>
1012<t>
1013   Bodies on HEAD requests have no defined semantics. Note that sending a body
1014   on a HEAD request might cause some existing implementations to reject the
1015   request.
1016</t>
1017</section>
1018
1019<section title="POST" anchor="POST">
1020  <iref primary="true" item="POST method" x:for-anchor=""/>
1021  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
1022<t>
1023   The POST method requests that the origin server accept the
1024   representation enclosed in the request as data to be processed by the
1025   target resource. POST is designed to allow a uniform method to cover the
1026   following functions:
1027  <list style="symbols">
1028    <t>
1029      Annotation of existing resources;
1030    </t>
1031    <t>
1032        Posting a message to a bulletin board, newsgroup, mailing list,
1033        or similar group of articles;
1034    </t>
1035    <t>
1036        Providing a block of data, such as the result of submitting a
1037        form, to a data-handling process;
1038    </t>
1039    <t>
1040        Extending a database through an append operation.
1041    </t>
1042  </list>
1043</t>
1044<t>
1045   The actual function performed by the POST method is determined by the
1046   server and is usually dependent on the effective request URI.
1047</t>
1048<t>
1049   The action performed by the POST method might not result in a
1050   resource that can be identified by a URI. In this case, either 200
1051   (OK) or 204 (No Content) is the appropriate response status code,
1052   depending on whether or not the response includes a representation that
1053   describes the result.
1054</t>
1055<t>
1056   If a resource has been created on the origin server, the response
1057   &SHOULD; be 201 (Created) and contain a representation which describes the
1058   status of the request and refers to the new resource, and a Location
1059   header field (see <xref target="header.location"/>).
1060</t>
1061<t>
1062   Responses to POST requests are only cacheable when they
1063   include explicit freshness information (see &p6-explicit;). A
1064   cached POST response with a Content-Location header field
1065   (see &header-content-location;) whose value is the effective
1066   Request URI &MAY; be used to satisfy subsequent GET and HEAD requests.
1067</t>
1068<t>
1069   Note that POST caching is not widely implemented.
1070   However, the 303 (See Other) response can be used to direct the
1071   user agent to retrieve a cacheable resource.
1072</t>
1073</section>
1074
1075<section title="PUT" anchor="PUT">
1076  <iref primary="true" item="PUT method" x:for-anchor=""/>
1077  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
1078<t>
1079   The PUT method requests that the state of the target resource
1080   be created or replaced with the state defined by the representation
1081   enclosed in the request message payload.  A successful PUT of a given
1082   representation would suggest that a subsequent GET on that same target
1083   resource will result in an equivalent representation being returned in
1084   a 200 (OK) response.  However, there is no guarantee that such a state
1085   change will be observable, since the target resource might be acted
1086   upon by other user agents in parallel, or might be subject to dynamic
1087   processing by the origin server, before any subsequent GET is received.
1088   A successful response only implies that the user agent's intent was
1089   achieved at the time of its processing by the origin server.
1090</t>
1091<t>   
1092   If the target resource does not have a current representation and
1093   the PUT successfully creates one, then the origin server &MUST; inform
1094   the user agent by sending a 201 (Created) response.  If the target
1095   resource does have a current representation and that representation is
1096   successfully modified in accordance with the state of the enclosed
1097   representation, then either a 200 (OK) or 204 (No Content) response
1098   &SHOULD; be sent to indicate successful completion of the request.
1099</t>
1100<t>
1101   Unrecognized header fields &SHOULD; be ignored (i.e., not saved
1102   as part of the resource state).
1103</t>
1104<t>
1105   An origin server &SHOULD; verify that the PUT representation is
1106   consistent with any constraints which the server has for the target
1107   resource that cannot or will not be changed by the PUT.  This is
1108   particularly important when the origin server uses internal
1109   configuration information related to the URI in order to set the
1110   values for representation metadata on GET responses.  When a PUT
1111   representation is inconsistent with the target resource, the origin
1112   server &SHOULD; either make them consistent, by transforming the
1113   representation or changing the resource configuration, or respond
1114   with an appropriate error message containing sufficient information
1115   to explain why the representation is unsuitable.  The 409 (Conflict)
1116   or 415 (Unsupported Media Type) status codes are suggested, with the
1117   latter being specific to constraints on Content-Type values.
1118</t>
1119<t>
1120   For example, if the target resource is configured to always have a
1121   Content-Type of "text/html" and the representation being PUT has a
1122   Content-Type of "image/jpeg", then the origin server &SHOULD; do one of:
1123   (a) reconfigure the target resource to reflect the new media type;
1124   (b) transform the PUT representation to a format consistent with that
1125   of the resource before saving it as the new resource state; or,
1126   (c) reject the request with a 415 response indicating that the target
1127   resource is limited to "text/html", perhaps including a link to a
1128   different resource that would be a suitable target for the new
1129   representation.
1130</t>
1131<t>
1132   HTTP does not define exactly how a PUT method affects the state
1133   of an origin server beyond what can be expressed by the intent of
1134   the user agent request and the semantics of the origin server response.
1135   It does not define what a resource might be, in any sense of that
1136   word, beyond the interface provided via HTTP.  It does not define
1137   how resource state is "stored", nor how such storage might change
1138   as a result of a change in resource state, nor how the origin server
1139   translates resource state into representations.  Generally speaking,
1140   all implementation details behind the resource interface are
1141   intentionally hidden by the server.
1142</t>
1143<t>
1144   The fundamental difference between the POST and PUT methods is
1145   highlighted by the different intent for the target resource.
1146   The target resource in a POST request is intended to handle the
1147   enclosed representation as a data-accepting process, such as for
1148   a gateway to some other protocol or a document that accepts annotations.
1149   In contrast, the target resource in a PUT request is intended to
1150   take the enclosed representation as a new or replacement value.
1151   Hence, the intent of PUT is idempotent and visible to intermediaries,
1152   even though the exact effect is only known by the origin server.
1153</t>
1154<t>
1155   Proper interpretation of a PUT request presumes that the user agent
1156   knows what target resource is desired.  A service that is intended
1157   to select a proper URI on behalf of the client, after receiving
1158   a state-changing request, &SHOULD; be implemented using the POST
1159   method rather than PUT.  If the origin server will not make the
1160   requested PUT state change to the target resource and instead
1161   wishes to have it applied to a different resource, such as when the
1162   resource has been moved to a different URI, then the origin server
1163   &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
1164   then make its own decision regarding whether or not to redirect the
1165   request.
1166</t>
1167<t>
1168   A PUT request applied to the target resource &MAY; have side-effects
1169   on other resources.  For example, an article might have a URI for
1170   identifying "the current version" (a resource) which is separate
1171   from the URIs identifying each particular version (different
1172   resources that at one point shared the same state as the current version
1173   resource).  A successful PUT request on "the current version" URI might
1174   therefore create a new version resource in addition to changing the
1175   state of the target resource, and might also cause links to be added
1176   between the related resources.
1177</t>
1178<t>
1179   An origin server &SHOULD; reject any PUT request that contains a
1180   Content-Range header field, since it might be misinterpreted as
1181   partial content (or might be partial content that is being mistakenly
1182   PUT as a full representation).  Partial content updates are
1183   possible by targeting a separately identified resource with state
1184   that overlaps a portion of the larger resource, or by using a
1185   different method that has been specifically defined for partial
1186   updates (for example, the PATCH method defined in
1187   <xref target="RFC5789"/>).
1188</t>
1189<t>
1190   Responses to the PUT method are not cacheable. If a PUT request passes
1191   through a cache that has one or more stored responses for the effective
1192   request URI, those stored responses will be invalidated (see
1193   &p6-invalid;).
1194</t>
1195</section>
1196
1197<section title="DELETE" anchor="DELETE">
1198  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1199  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1200<t>
1201   The DELETE method requests that the origin server delete the target
1202   resource. This method &MAY; be overridden by
1203   human intervention (or other means) on the origin server. The client cannot
1204   be guaranteed that the operation has been carried out, even if the
1205   status code returned from the origin server indicates that the action
1206   has been completed successfully. However, the server &SHOULD-NOT; 
1207   indicate success unless, at the time the response is given, it
1208   intends to delete the resource or move it to an inaccessible
1209   location.
1210</t>
1211<t>
1212   A successful response &SHOULD; be 200 (OK) if the response includes an
1213   representation describing the status, 202 (Accepted) if the action has not
1214   yet been enacted, or 204 (No Content) if the action has been enacted
1215   but the response does not include a representation.
1216</t>
1217<t>
1218   Bodies on DELETE requests have no defined semantics. Note that sending a body
1219   on a DELETE request might cause some existing implementations to reject the
1220   request.
1221</t>
1222<t>
1223   Responses to the DELETE method are not cacheable. If a DELETE request
1224   passes through a cache that has one or more stored responses for the
1225   effective request URI, those stored responses will be invalidated (see
1226   &p6-invalid;).
1227</t>
1228</section>
1229
1230<section title="TRACE" anchor="TRACE">
1231  <rdf:Description>
1232    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1233  </rdf:Description>
1234  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1235  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1236<t>
1237   The TRACE method requests a remote, application-layer loop-back
1238   of the request message. The final recipient of the request
1239   &SHOULD; reflect the message received back to the client as the
1240   message-body of a 200 (OK) response. The final recipient is either the
1241   origin server or the first proxy to receive a Max-Forwards
1242   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1243   A TRACE request &MUST-NOT; include a message-body.
1244</t>
1245<t>
1246   TRACE allows the client to see what is being received at the other
1247   end of the request chain and use that data for testing or diagnostic
1248   information. The value of the Via header field (&header-via;) is of
1249   particular interest, since it acts as a trace of the request chain.
1250   Use of the Max-Forwards header field allows the client to limit the
1251   length of the request chain, which is useful for testing a chain of
1252   proxies forwarding messages in an infinite loop.
1253</t>
1254<t>
1255   If the request is valid, the response &SHOULD; have a Content-Type of
1256   "message/http" (see &media-type-message-http;) and contain a message-body
1257   that encloses a copy of the entire request message.
1258   Responses to the TRACE method are not cacheable.
1259</t>
1260</section>
1261
1262<section title="CONNECT" anchor="CONNECT">
1263  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1264  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1265<t>
1266   The CONNECT method requests that the proxy establish a tunnel
1267   to the request-target and then restrict its behavior to blind
1268   forwarding of packets until the connection is closed.
1269</t>
1270<t>
1271   When using CONNECT, the request-target &MUST; use the authority form
1272   (&request-target;); i.e., the request-target consists of only the
1273   host name and port number of the tunnel destination, separated by a colon.
1274   For example,
1275</t>
1276<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1277CONNECT server.example.com:80 HTTP/1.1
1278Host: server.example.com:80
1279
1280</artwork></figure>
1281<t>
1282   Other HTTP mechanisms can be used normally with the CONNECT method &mdash;
1283   except end-to-end protocol Upgrade requests, since the
1284   tunnel must be established first.
1285</t>
1286<t>
1287   For example, proxy authentication might be used to establish the
1288   authority to create a tunnel:
1289</t>
1290<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1291CONNECT server.example.com:80 HTTP/1.1
1292Host: server.example.com:80
1293Proxy-Authorization: basic aGVsbG86d29ybGQ=
1294
1295</artwork></figure>
1296<t>
1297   Bodies on CONNECT requests have no defined semantics. Note that sending a body
1298   on a CONNECT request might cause some existing implementations to reject the
1299   request.
1300</t>
1301<t>
1302   Like any other pipelined HTTP/1.1 request, data to be tunnel may be
1303   sent immediately after the blank line. The usual caveats also apply:
1304   data may be discarded if the eventual response is negative, and the
1305   connection may be reset with no response if more than one TCP segment
1306   is outstanding.
1307</t>
1308
1309<section title="Establishing a Tunnel with CONNECT">
1310<t>
1311   Any successful (2xx) response to a CONNECT request indicates that the
1312   proxy has established a connection to the requested host and port,
1313   and has switched to tunneling the current connection to that server
1314   connection.
1315</t>
1316<t>
1317   It may be the case that the proxy itself can only reach the requested
1318   origin server through another proxy.  In this case, the first proxy
1319   &SHOULD; make a CONNECT request of that next proxy, requesting a tunnel
1320   to the authority.  A proxy &MUST-NOT; respond with any 2xx status code
1321   unless it has either a direct or tunnel connection established to the
1322   authority.
1323</t>
1324<t>
1325   An origin server which receives a CONNECT request for itself &MAY;
1326   respond with a 2xx status code to indicate that a connection is
1327   established.
1328</t>
1329<t>
1330   If at any point either one of the peers gets disconnected, any
1331   outstanding data that came from that peer will be passed to the other
1332   one, and after that also the other connection will be terminated by
1333   the proxy. If there is outstanding data to that peer undelivered,
1334   that data will be discarded.
1335</t>
1336
1337</section>
1338</section>
1339</section>
1340
1341
1342<section title="Status Code Definitions" anchor="status.codes">
1343<t>
1344   The first digit of the Status-Code defines the class of response. The
1345   last two digits do not have any categorization role. There are 5
1346   values for the first digit:
1347  <list style="symbols">
1348    <t>
1349      1xx: Informational - Request received, continuing process
1350    </t>
1351    <t>
1352      2xx: Success - The action was successfully received,
1353        understood, and accepted
1354    </t>
1355    <t>
1356      3xx: Redirection - Further action must be taken in order to
1357        complete the request
1358    </t>
1359    <t>
1360      4xx: Client Error - The request contains bad syntax or cannot
1361        be fulfilled
1362    </t>
1363    <t>
1364      5xx: Server Error - The server failed to fulfill an apparently
1365        valid request
1366    </t>
1367  </list>
1368</t>
1369<t>
1370   Each Status-Code is described below, including any metadata required
1371   in the response.
1372</t>
1373
1374<section title="Informational 1xx" anchor="status.1xx">
1375<t>
1376   This class of status code indicates a provisional response,
1377   consisting only of the Status-Line and optional header fields, and is
1378   terminated by an empty line. There are no required header fields for this
1379   class of status code. Since HTTP/1.0 did not define any 1xx status
1380   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1381   except under experimental conditions.
1382</t>
1383<t>
1384   A client &MUST; be prepared to accept one or more 1xx status responses
1385   prior to a regular response, even if the client does not expect a 100
1386   (Continue) status message. Unexpected 1xx status responses &MAY; be
1387   ignored by a user agent.
1388</t>
1389<t>
1390   Proxies &MUST; forward 1xx responses, unless the connection between the
1391   proxy and its client has been closed, or unless the proxy itself
1392   requested the generation of the 1xx response. (For example, if a
1393   proxy adds a "Expect: 100-continue" field when it forwards a request,
1394   then it need not forward the corresponding 100 (Continue)
1395   response(s).)
1396</t>
1397
1398<section title="100 Continue" anchor="status.100">
1399  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1400  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1401<t>
1402   The client &SHOULD; continue with its request. This interim response is
1403   used to inform the client that the initial part of the request has
1404   been received and has not yet been rejected by the server. The client
1405   &SHOULD; continue by sending the remainder of the request or, if the
1406   request has already been completed, ignore this response. The server
1407   &MUST; send a final response after the request has been completed. See
1408   &use100; for detailed discussion of the use and handling of this
1409   status code.
1410</t>
1411</section>
1412
1413<section title="101 Switching Protocols" anchor="status.101">
1414  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1415  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1416<t>
1417   The server understands and is willing to comply with the client's
1418   request, via the Upgrade message header field (&header-upgrade;), for a
1419   change in the application protocol being used on this connection. The
1420   server will switch protocols to those defined by the response's
1421   Upgrade header field immediately after the empty line which
1422   terminates the 101 response.
1423</t>
1424<t>
1425   The protocol &SHOULD; be switched only when it is advantageous to do
1426   so. For example, switching to a newer version of HTTP is advantageous
1427   over older versions, and switching to a real-time, synchronous
1428   protocol might be advantageous when delivering resources that use
1429   such features.
1430</t>
1431</section>
1432</section>
1433
1434<section title="Successful 2xx" anchor="status.2xx">
1435<t>
1436   This class of status code indicates that the client's request was
1437   successfully received, understood, and accepted.
1438</t>
1439
1440<section title="200 OK" anchor="status.200">
1441  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1442  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1443<t>
1444   The request has succeeded. The payload returned with the response
1445   is dependent on the method used in the request, for example:
1446  <list style="hanging">
1447    <t hangText="GET">
1448      a representation of the target resource is sent in the response;
1449    </t>
1450    <t hangText="HEAD">
1451      the same representation as GET, except without the message-body;
1452    </t>
1453    <t hangText="POST">
1454      a representation describing or containing the result of the action;
1455    </t>
1456    <t hangText="TRACE">
1457      a representation containing the request message as received by the
1458      end server.
1459    </t>
1460  </list>
1461</t>
1462<t>
1463   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1464   freshness for 200 responses.
1465</t>
1466</section>
1467
1468<section title="201 Created" anchor="status.201">
1469  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1470  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1471<t>
1472   The request has been fulfilled and has resulted in a new resource being
1473   created. The newly created resource can be referenced by the URI(s)
1474   returned in the payload of the response, with the most specific URI
1475   for the resource given by a Location header field. The response
1476   &SHOULD; include a payload containing a list of resource
1477   characteristics and location(s) from which the user or user agent can
1478   choose the one most appropriate. The payload format is specified by
1479   the media type given in the Content-Type header field. The origin
1480   server &MUST; create the resource before returning the 201 status code.
1481   If the action cannot be carried out immediately, the server &SHOULD;
1482   respond with 202 (Accepted) response instead.
1483</t>
1484<t>
1485   A 201 response &MAY; contain an ETag response header field indicating
1486   the current value of the entity-tag for the representation of the resource
1487   just created (see &header-etag;).
1488</t>
1489</section>
1490
1491<section title="202 Accepted" anchor="status.202">
1492  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1493  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1494<t>
1495   The request has been accepted for processing, but the processing has
1496   not been completed.  The request might or might not eventually be
1497   acted upon, as it might be disallowed when processing actually takes
1498   place. There is no facility for re-sending a status code from an
1499   asynchronous operation such as this.
1500</t>
1501<t>
1502   The 202 response is intentionally non-committal. Its purpose is to
1503   allow a server to accept a request for some other process (perhaps a
1504   batch-oriented process that is only run once per day) without
1505   requiring that the user agent's connection to the server persist
1506   until the process is completed. The representation returned with this
1507   response &SHOULD; include an indication of the request's current status
1508   and either a pointer to a status monitor or some estimate of when the
1509   user can expect the request to be fulfilled.
1510</t>
1511</section>
1512
1513<section title="203 Non-Authoritative Information" anchor="status.203">
1514  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1515  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1516<t>
1517   The representation in the response has been transformed or otherwise
1518   modified by a transforming proxy (&intermediaries;).  Note that the
1519   behaviour of transforming intermediaries is controlled by the no-transform
1520   Cache-Control directive (&header-cache-control;).
1521</t>
1522<t>
1523   This status code is only appropriate when the response status code would
1524   have been 200 (OK) otherwise. When the status code before transformation
1525   would have been different, the 214 Transformation Applied warn-code
1526   (&header-warning;) is appropriate.
1527</t>
1528<t>
1529   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1530   freshness for 203 responses.
1531</t>
1532</section>
1533
1534<section title="204 No Content" anchor="status.204">
1535  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1536  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1537<t>
1538   The 204 (No Content) status code indicates that the server has
1539   successfully fulfilled the request and that there is no additional
1540   content to return in the response payload body.  Metadata in the
1541   response header fields refer to the target resource and its current
1542   representation after the requested action.
1543</t>
1544<t>
1545   For example, if a 204 status code is received in response to a PUT
1546   request and the response contains an ETag header field, then the PUT
1547   was successful and the ETag field-value contains the entity-tag for
1548   the new representation of that target resource.
1549</t>
1550<t>
1551   The 204 response allows a server to indicate that the action has been
1552   successfully applied to the target resource while implying that the
1553   user agent &SHOULD-NOT; traverse away from its current "document view"
1554   (if any).  The server assumes that the user agent will provide some
1555   indication of the success to its user, in accord with its own interface,
1556   and apply any new or updated metadata in the response to the active
1557   representation.
1558</t>
1559<t>
1560   For example, a 204 status code is commonly used with document editing
1561   interfaces corresponding to a "save" action, such that the document
1562   being saved remains available to the user for editing. It is also
1563   frequently used with interfaces that expect automated data transfers
1564   to be prevalent, such as within distributed version control systems.
1565</t>
1566<t>
1567   The 204 response &MUST-NOT; include a message-body, and thus is always
1568   terminated by the first empty line after the header fields.
1569</t>
1570</section>
1571
1572<section title="205 Reset Content" anchor="status.205">
1573  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1574  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1575<t>
1576   The server has fulfilled the request and the user agent &SHOULD; reset
1577   the document view which caused the request to be sent. This response
1578   is primarily intended to allow input for actions to take place via
1579   user input, followed by a clearing of the form in which the input is
1580   given so that the user can easily initiate another input action.
1581</t>
1582<t>   
1583   The message-body included with the response &MUST; be empty. Note that
1584   receivers still need to parse the response according to the algorithm defined
1585   in &message-body;.
1586</t>
1587</section>
1588
1589<section title="206 Partial Content" anchor="status.206">
1590  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1591  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1592  <rdf:Description>
1593    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1594  </rdf:Description>
1595<t>
1596   The server has fulfilled the partial GET request for the resource
1597   and the enclosed payload is a partial representation as defined in &status-206;.
1598</t>
1599<t>
1600   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1601   freshness for 206 responses.
1602</t>
1603</section>
1604</section>
1605
1606<section title="Redirection 3xx" anchor="status.3xx">
1607<t>
1608   This class of status code indicates that further action needs to be
1609   taken by the user agent in order to fulfill the request.  If the required
1610   action involves a subsequent HTTP request, it &MAY; be carried out by the
1611   user agent without interaction with the user if and only if the method used
1612   in the second request is known to be "safe", as defined in
1613   <xref target="safe.methods"/>.
1614</t>
1615<t>
1616   There are several types of redirects:
1617   <list style="numbers">
1618      <x:lt>
1619        <t>
1620          Redirects of the request to another URI, either temporarily or
1621          permanently. The new URI is specified in the Location header field.
1622          In this specification, the status codes 301 (Moved Permanently),
1623          302 (Found), and 307 (Temporary Redirect) fall under this category.
1624        </t>
1625      </x:lt>
1626      <x:lt>
1627        <t>
1628          Redirection to a new location that represents an indirect response to
1629          the request, such as the result of a POST operation to be retrieved
1630          with a subsequent GET request. This is status code 303 (See Other).
1631        </t>
1632      </x:lt>
1633      <x:lt>
1634        <t>
1635          Redirection offering a choice of matching resources for use by
1636          agent-driven content negotiation (&agent-driven-negotiation;). This
1637          is status code 300 (Multiple Choices).
1638        </t>
1639      </x:lt>
1640      <x:lt>
1641        <t>
1642          Other kinds of redirection, such as to a cached result (status code 304
1643          (Not Modified)).
1644        </t>
1645      </x:lt>
1646   </list>
1647</t>
1648<x:note>
1649  <t>
1650    <x:h>Note:</x:h> In HTTP/1.0, only the status codes 301 (Moved Permanently)
1651    and 302 (Found) were defined for the first type of redirect, and the second
1652    type did not exist at all (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>).
1653    However it turned out that web forms using POST expected redirects to change
1654    the operation for the subsequent request to retrieval (GET). To address this
1655    use case, HTTP/1.1 introduced the second type of redirect with the status
1656    code 303 (See Other) (<xref target="RFC2068" x:fmt="," x:sec="10.3.4"/>).
1657    As user agents did not change their behavior to maintain backwards
1658    compatibility, the first revision of HTTP/1.1 added yet another status code,
1659    307 (Temporary Redirect), for which the backwards compatibility problems did
1660    not apply (<xref target="RFC2616" x:fmt="," x:sec="10.3.8"/>).
1661    Over 10 years later, most user agents still do method rewriting for
1662    status codes 301 and 302, therefore this specification makes that behavior
1663    compliant in case the original request was POST.
1664  </t>
1665</x:note>
1666<t>
1667   Clients &SHOULD; detect and intervene in cyclical redirections (i.e.,
1668   "infinite" redirection loops).
1669</t>
1670<x:note>
1671  <t>
1672    <x:h>Note:</x:h> An earlier version of this specification recommended a
1673    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1674    Content developers need to be aware that some clients might
1675    implement such a fixed limitation.
1676  </t>
1677</x:note>
1678
1679<section title="300 Multiple Choices" anchor="status.300">
1680  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1681  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1682<t>
1683   The target resource has more than one
1684   representation, each with its own specific location, and agent-driven
1685   negotiation information (&content-negotiation;) is being provided so that
1686   the user (or user agent) can select a preferred representation by
1687   redirecting its request to that location.
1688</t>
1689<t>
1690   Unless it was a HEAD request, the response &SHOULD; include a representation
1691   containing a list of representation metadata and location(s) from
1692   which the user or user agent can choose the one most appropriate. The
1693   data format is specified by the media type given in the Content-Type
1694   header field. Depending upon the format and the capabilities of
1695   the user agent, selection of the most appropriate choice &MAY; be
1696   performed automatically. However, this specification does not define
1697   any standard for such automatic selection.
1698</t>
1699<t>
1700   If the server has a preferred choice of representation, it &SHOULD;
1701   include the specific URI for that representation in the Location
1702   field; user agents &MAY; use the Location field value for automatic
1703   redirection.
1704</t>
1705<t>
1706   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1707   freshness for 300 responses.
1708</t>
1709
1710</section>
1711
1712<section title="301 Moved Permanently" anchor="status.301">
1713  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1714  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1715<t>
1716   The target resource has been assigned a new permanent URI and any
1717   future references to this resource &SHOULD; use one of the returned
1718   URIs.  Clients with link editing capabilities ought to automatically
1719   re-link references to the effective request URI to one or more of the new
1720   references returned by the server, where possible.
1721</t>
1722<t>
1723   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1724   freshness for 301 responses.
1725</t>
1726<t>
1727   The new permanent URI &SHOULD; be given by the Location field in the
1728   response. Unless the request method was HEAD, the representation of the
1729   response &SHOULD; contain a short hypertext note with a hyperlink to
1730   the new URI(s).
1731</t>
1732<t>
1733   If the 301 status code is received in response to a request method
1734   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1735   then the request &MAY; be automatically redirected by the user agent without
1736   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1737   request unless it can be confirmed by the user, since this might
1738   change the conditions under which the request was issued.
1739</t>
1740<x:note>
1741  <t>
1742    <x:h>Note:</x:h> For historic reasons, user agents &MAY; change the
1743    request method from POST to GET for the subsequent request. If this
1744    behavior is undesired, status code 307 (Temporary Redirect) can be used
1745    instead.
1746  </t>
1747</x:note>
1748</section>
1749
1750<section title="302 Found" anchor="status.302">
1751  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1752  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1753<t>
1754   The target resource resides temporarily under a different URI.
1755   Since the redirection might be altered on occasion, the client &SHOULD;
1756   continue to use the effective request URI for future requests.
1757</t>
1758<t>
1759   The temporary URI &SHOULD; be given by the Location field in the
1760   response. Unless the request method was HEAD, the representation of the
1761   response &SHOULD; contain a short hypertext note with a hyperlink to
1762   the new URI(s).
1763</t>
1764<t>
1765   If the 302 status code is received in response to a request method
1766   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1767   then the request &MAY; be automatically redirected by the user agent without
1768   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1769   request unless it can be confirmed by the user, since this might
1770   change the conditions under which the request was issued.
1771</t>
1772<x:note>
1773  <t>
1774    <x:h>Note:</x:h> For historic reasons, user agents &MAY; change the
1775    request method from POST to GET for the subsequent request. If this
1776    behavior is undesired, status code 307 (Temporary Redirect) can be used
1777    instead.
1778    <cref anchor="issue312">but see <eref target="http://trac.tools.ietf.org/wg/httpbis/trac/ticket/312"/></cref>
1779  </t>
1780</x:note>
1781</section>
1782
1783<section title="303 See Other" anchor="status.303">
1784  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1785  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1786<t>
1787   The 303 status code indicates that the server is redirecting the
1788   user agent to a different resource, as indicated by a URI in the
1789   Location header field, that is intended to provide an indirect
1790   response to the original request.  In order to satisfy the original
1791   request, a user agent &SHOULD; perform a retrieval request using the
1792   Location URI (a GET or HEAD request if using HTTP), which
1793   may itself be redirected further, and present the eventual result as an
1794   answer to the original request.
1795   Note that the new URI in the Location header field is not considered
1796   equivalent to the effective request URI.
1797</t>
1798<t>
1799   This status code is generally applicable to any HTTP method.  It is
1800   primarily used to allow the output of a POST action to redirect
1801   the user agent to a selected resource, since doing so provides the
1802   information corresponding to the POST response in a form that
1803   can be separately identified, bookmarked, and cached independent
1804   of the original request.
1805</t>
1806<t>
1807   A 303 response to a GET request indicates that the requested
1808   resource does not have a representation of its own that can be
1809   transferred by the server over HTTP.  The Location URI indicates a
1810   resource that is descriptive of the target resource, such that the
1811   follow-on representation might be useful to recipients without
1812   implying that it adequately represents the target resource.
1813   Note that answers to the questions of what can be represented, what
1814   representations are adequate, and what might be a useful description
1815   are outside the scope of HTTP and thus entirely determined by the
1816   URI owner(s).
1817</t>
1818<t>
1819   Except for responses to a HEAD request, the representation of a 303
1820   response &SHOULD; contain a short hypertext note with a hyperlink
1821   to the Location URI.
1822</t>
1823</section>
1824
1825<section title="304 Not Modified" anchor="status.304">
1826  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1827  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1828  <rdf:Description>
1829    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1830  </rdf:Description>
1831<t>
1832   The response to the request has not been modified since the conditions
1833   indicated by the client's conditional GET request, as defined in &status-304;.
1834</t>
1835</section>
1836
1837<section title="305 Use Proxy" anchor="status.305">
1838  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1839  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1840<t>
1841   The 305 status code was defined in a previous version of this specification
1842   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1843</t>
1844</section>
1845
1846<section title="306 (Unused)" anchor="status.306">
1847  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1848  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1849<t>
1850   The 306 status code was used in a previous version of the
1851   specification, is no longer used, and the code is reserved.
1852</t>
1853</section>
1854
1855<section title="307 Temporary Redirect" anchor="status.307">
1856  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1857  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1858<t>
1859   The target resource resides temporarily under a different URI.
1860   Since the redirection can change over time, the client &SHOULD;
1861   continue to use the effective request URI for future requests.
1862</t>
1863<t>
1864   The temporary URI &SHOULD; be given by the Location field in the
1865   response. Unless the request method was HEAD, the representation of the
1866   response &SHOULD; contain a short hypertext note with a hyperlink to
1867   the new URI(s), since many pre-HTTP/1.1 user agents do not
1868   understand the 307 status code. Therefore, the note &SHOULD; contain the
1869   information necessary for a user to repeat the original request on
1870   the new URI.
1871</t>
1872<t>
1873   If the 307 status code is received in response to a request method
1874   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1875   then the request &MAY; be automatically redirected by the user agent without
1876   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1877   request unless it can be confirmed by the user, since this might
1878   change the conditions under which the request was issued.
1879</t>
1880</section>
1881</section>
1882
1883<section title="Client Error 4xx" anchor="status.4xx">
1884<t>
1885   The 4xx class of status code is intended for cases in which the
1886   client seems to have erred. Except when responding to a HEAD request,
1887   the server &SHOULD; include a representation containing an explanation of the
1888   error situation, and whether it is a temporary or permanent
1889   condition. These status codes are applicable to any request method.
1890   User agents &SHOULD; display any included representation to the user.
1891</t>
1892<t>
1893   If the client is sending data, a server implementation using TCP
1894   &SHOULD; be careful to ensure that the client acknowledges receipt of
1895   the packet(s) containing the response, before the server closes the
1896   input connection. If the client continues sending data to the server
1897   after the close, the server's TCP stack will send a reset packet to
1898   the client, which might erase the client's unacknowledged input buffers
1899   before they can be read and interpreted by the HTTP application.
1900</t>
1901
1902<section title="400 Bad Request" anchor="status.400">
1903  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1904  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1905<t>
1906   The server cannot or will not process the request, due to a client error (e.g.,
1907   malformed syntax).</t>
1908</section>
1909
1910<section title="401 Unauthorized" anchor="status.401">
1911  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1912  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1913  <rdf:Description>
1914    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1915  </rdf:Description>
1916<t>
1917   The request requires user authentication (see &status-401;).
1918</t>
1919</section>
1920
1921<section title="402 Payment Required" anchor="status.402">
1922  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1923  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1924<t>
1925   This code is reserved for future use.
1926</t>
1927</section>
1928
1929<section title="403 Forbidden" anchor="status.403">
1930  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1931  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1932<t>
1933   The server understood the request, but refuses to authorize it. Providing
1934   different user authentication credentials might be successful, but any
1935   credentials that were provided in the request are insufficient. The request
1936   &SHOULD-NOT; be repeated with the same credentials.
1937</t>
1938<t>
1939   If the request method was not HEAD and the server wishes to make
1940   public why the request has not been fulfilled, it &SHOULD; describe the
1941   reason for the refusal in the representation.  If the server does not wish to
1942   make this information available to the client, the status code 404
1943   (Not Found) &MAY; be used instead.
1944</t>
1945</section>
1946
1947<section title="404 Not Found" anchor="status.404">
1948  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1949  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1950<t>
1951   The server has not found anything matching the effective request URI. No
1952   indication is given of whether the condition is temporary or
1953   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1954   knows, through some internally configurable mechanism, that an old
1955   resource is permanently unavailable and has no forwarding address.
1956   This status code is commonly used when the server does not wish to
1957   reveal exactly why the request has been refused, or when no other
1958   response is applicable.
1959</t>
1960</section>
1961
1962<section title="405 Method Not Allowed" anchor="status.405">
1963  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1964  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1965<t>
1966   The method specified in the Request-Line is not allowed for the target
1967   resource. The response &MUST; include an Allow header field containing a
1968   list of valid methods for the requested resource.
1969</t>
1970</section>
1971
1972<section title="406 Not Acceptable" anchor="status.406">
1973  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1974  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1975<t>
1976   The resource identified by the request is only capable of generating
1977   response representations which have content characteristics not acceptable
1978   according to the Accept and Accept-* header fields sent in the request
1979   (see &p3-header-fields;).
1980</t>
1981<t>
1982   Unless it was a HEAD request, the response &SHOULD; include a representation
1983   containing a list of available representation characteristics and location(s)
1984   from which the user or user agent can choose the one most
1985   appropriate. The data format is specified by the media type given
1986   in the Content-Type header field. Depending upon the format and the
1987   capabilities of the user agent, selection of the most appropriate
1988   choice &MAY; be performed automatically. However, this specification
1989   does not define any standard for such automatic selection.
1990</t>
1991<x:note>
1992  <t>
1993    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1994    not acceptable according to the accept header fields sent in the
1995    request. In some cases, this might even be preferable to sending a
1996    406 response. User agents are encouraged to inspect the header fields of
1997    an incoming response to determine if it is acceptable.
1998  </t>
1999</x:note>
2000<t>
2001   If the response could be unacceptable, a user agent &SHOULD;
2002   temporarily stop receipt of more data and query the user for a
2003   decision on further actions.
2004</t>
2005</section>
2006
2007<section title="407 Proxy Authentication Required" anchor="status.407">
2008  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
2009  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
2010<t>
2011   This code is similar to 401 (Unauthorized), but indicates that the
2012   client must first authenticate itself with the proxy (see &status-407;).
2013</t>
2014</section>
2015
2016<section title="408 Request Timeout" anchor="status.408">
2017  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
2018  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
2019<t>
2020   The client did not produce a request within the time that the server
2021   was prepared to wait. The client &MAY; repeat the request without
2022   modifications at any later time.
2023</t>
2024</section>
2025
2026<section title="409 Conflict" anchor="status.409">
2027  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
2028  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
2029<t>
2030   The request could not be completed due to a conflict with the current
2031   state of the resource. This code is only allowed in situations where
2032   it is expected that the user might be able to resolve the conflict
2033   and resubmit the request. The response body &SHOULD; include enough
2034   information for the user to recognize the source of the conflict.
2035   Ideally, the response representation would include enough information for the
2036   user or user agent to fix the problem; however, that might not be
2037   possible and is not required.
2038</t>
2039<t>
2040   Conflicts are most likely to occur in response to a PUT request. For
2041   example, if versioning were being used and the representation being PUT
2042   included changes to a resource which conflict with those made by an
2043   earlier (third-party) request, the server might use the 409 response
2044   to indicate that it can't complete the request. In this case, the
2045   response representation would likely contain a list of the differences
2046   between the two versions in a format defined by the response
2047   Content-Type.
2048</t>
2049</section>
2050
2051<section title="410 Gone" anchor="status.410">
2052  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
2053  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
2054<t>
2055   The target resource is no longer available at the server and no
2056   forwarding address is known. This condition is expected to be
2057   considered permanent. Clients with link editing capabilities &SHOULD;
2058   delete references to the effective request URI after user approval. If the
2059   server does not know, or has no facility to determine, whether or not
2060   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
2061   used instead.
2062</t>
2063<t>
2064   The 410 response is primarily intended to assist the task of web
2065   maintenance by notifying the recipient that the resource is
2066   intentionally unavailable and that the server owners desire that
2067   remote links to that resource be removed. Such an event is common for
2068   limited-time, promotional services and for resources belonging to
2069   individuals no longer working at the server's site. It is not
2070   necessary to mark all permanently unavailable resources as "gone" or
2071   to keep the mark for any length of time &mdash; that is left to the
2072   discretion of the server owner.
2073</t>
2074<t>
2075   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine freshness
2076   for 410 responses.
2077</t>
2078
2079</section>
2080
2081<section title="411 Length Required" anchor="status.411">
2082  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
2083  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
2084<t>
2085   The server refuses to accept the request without a defined Content-Length.
2086   The client &MAY; repeat the request if it adds a valid
2087   Content-Length header field containing the length of the message-body
2088   in the request message.
2089</t>
2090</section>
2091
2092<section title="412 Precondition Failed" anchor="status.412">
2093  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
2094  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
2095  <rdf:Description>
2096    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
2097  </rdf:Description>
2098<t>
2099   The precondition given in one or more of the header fields
2100   evaluated to false when it was tested on the server, as defined in
2101   &status-412;.
2102</t>
2103</section>
2104
2105<section title="413 Request Representation Too Large" anchor="status.413">
2106  <iref primary="true" item="413 Request Representation Too Large (status code)" x:for-anchor=""/>
2107  <iref primary="true" item="Status Codes" subitem="413 Request Representation Too Large" x:for-anchor=""/>
2108<t>
2109   The server is refusing to process a request because the request
2110   representation is larger than the server is willing or able to process. The
2111   server &MAY; close the connection to prevent the client from continuing
2112   the request.
2113</t>
2114<t>
2115   If the condition is temporary, the server &SHOULD; include a Retry-After
2116   header field to indicate that it is temporary and after what
2117   time the client &MAY; try again.
2118</t>
2119</section>
2120
2121<section title="414 URI Too Long" anchor="status.414">
2122  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
2123  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
2124<t>
2125   The server is refusing to service the request because the effective request URI
2126   is longer than the server is willing to interpret. This rare
2127   condition is only likely to occur when a client has improperly
2128   converted a POST request to a GET request with long query
2129   information, when the client has descended into a URI "black hole" of
2130   redirection (e.g., a redirected URI prefix that points to a suffix of
2131   itself), or when the server is under attack by a client attempting to
2132   exploit security holes present in some servers using fixed-length
2133   buffers for reading or manipulating the effective request URI.
2134</t>
2135</section>
2136
2137<section title="415 Unsupported Media Type" anchor="status.415">
2138  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
2139  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
2140<t>
2141   The server is refusing to service the request because the request
2142   payload is in a format not supported by this request method on the
2143   target resource.
2144</t>
2145</section>
2146
2147<section title="416 Requested Range Not Satisfiable" anchor="status.416">
2148  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
2149  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
2150  <rdf:Description>
2151    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
2152  </rdf:Description>
2153<t>
2154   The request included a Range header field (&header-range;) and none of
2155   the range-specifier values in this field overlap the current extent
2156   of the selected resource. See &status-416;.
2157</t>
2158</section>
2159
2160<section title="417 Expectation Failed" anchor="status.417">
2161  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
2162  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
2163<t>
2164   The expectation given in an Expect header field (see <xref target="header.expect"/>)
2165   could not be met by this server, or, if the server is a proxy,
2166   the server has unambiguous evidence that the request could not be met
2167   by the next-hop server.
2168</t>
2169</section>
2170
2171<section title="426 Upgrade Required" anchor="status.426">
2172  <iref primary="true" item="426 Upgrade Required (status code)" x:for-anchor=""/>
2173  <iref primary="true" item="Status Codes" subitem="426 Upgrade Required" x:for-anchor=""/>
2174<t>
2175   The request can not be completed without a prior protocol upgrade. This
2176   response &MUST; include an Upgrade header field (&header-upgrade;)
2177   specifying the required protocols.
2178</t>
2179<figure>
2180<preamble>Example:</preamble>
2181<artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
2182HTTP/1.1 426 Upgrade Required
2183Upgrade: HTTP/2.0
2184Connection: Upgrade
2185
2186</artwork></figure>
2187<t>
2188   The server &SHOULD; include a message body in the 426 response which
2189   indicates in human readable form the reason for the error and describes any
2190   alternative courses which may be available to the user.
2191</t>
2192</section>
2193</section>
2194
2195<section title="Server Error 5xx" anchor="status.5xx">
2196<t>
2197   Response status codes beginning with the digit "5" indicate cases in
2198   which the server is aware that it has erred or is incapable of
2199   performing the request. Except when responding to a HEAD request, the
2200   server &SHOULD; include a representation containing an explanation of the
2201   error situation, and whether it is a temporary or permanent
2202   condition. User agents &SHOULD; display any included representation to the
2203   user. These response codes are applicable to any request method.
2204</t>
2205
2206<section title="500 Internal Server Error" anchor="status.500">
2207  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
2208  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
2209<t>
2210   The server encountered an unexpected condition which prevented it
2211   from fulfilling the request.
2212</t>
2213</section>
2214
2215<section title="501 Not Implemented" anchor="status.501">
2216  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
2217  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
2218<t>
2219   The server does not support the functionality required to fulfill the
2220   request. This is the appropriate response when the server does not
2221   recognize the request method and is not capable of supporting it for
2222   any resource.
2223</t>
2224</section>
2225
2226<section title="502 Bad Gateway" anchor="status.502">
2227  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
2228  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
2229<t>
2230   The server, while acting as a gateway or proxy, received an invalid
2231   response from the upstream server it accessed in attempting to
2232   fulfill the request.
2233</t>
2234</section>
2235
2236<section title="503 Service Unavailable" anchor="status.503">
2237  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
2238  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
2239<t>
2240   The server is currently unable or unwilling to handle the request due to
2241   reasons such as temporary overloading, maintenance of the server, or rate
2242   limiting of the client.
2243</t>
2244<t>
2245   The implication is that this is a temporary condition which will be
2246   alleviated after some delay. If known, the length of the delay &MAY; be
2247   indicated in a Retry-After header field (<xref target="header.retry-after"/>).
2248   If no Retry-After is given, the client &SHOULD; handle the response as it
2249   would for a 500 response.
2250</t>
2251<x:note>
2252  <t>
2253    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
2254    server must use it when becoming overloaded. Some servers might wish
2255    to simply refuse the connection.
2256  </t>
2257</x:note>
2258</section>
2259
2260<section title="504 Gateway Timeout" anchor="status.504">
2261  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
2262  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
2263<t>
2264   The server, while acting as a gateway or proxy, did not receive a
2265   timely response from the upstream server specified by the URI (e.g.,
2266   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
2267   to access in attempting to complete the request.
2268</t>
2269<x:note>
2270  <t>
2271    <x:h>Note</x:h> to implementors: some deployed proxies are known to
2272    return 400 or 500 when DNS lookups time out.
2273  </t>
2274</x:note>
2275</section>
2276
2277<section title="505 HTTP Version Not Supported" anchor="status.505">
2278  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
2279  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
2280<t>
2281   The server does not support, or refuses to support, the protocol
2282   version that was used in the request message. The server is
2283   indicating that it is unable or unwilling to complete the request
2284   using the same major version as the client, as described in &http-version;,
2285   other than with this error message. The response &SHOULD; contain
2286   a representation describing why that version is not supported and what other
2287   protocols are supported by that server.
2288</t>
2289
2290</section>
2291</section>
2292</section>
2293
2294
2295<section title="Date/Time Formats" anchor="http.date">
2296  <x:anchor-alias value="HTTP-date"/>
2297<t>
2298   HTTP applications have historically allowed three different formats
2299   for date/time stamps. However, the preferred format is a fixed-length subset
2300   of that defined by <xref target="RFC1123"/>:
2301</t>
2302<figure><artwork type="example" x:indent-with="  ">
2303Sun, 06 Nov 1994 08:49:37 GMT  ; RFC 1123
2304</artwork></figure>
2305<t>
2306   The other formats are described here only for compatibility with obsolete
2307   implementations.
2308</t>
2309<figure><artwork type="example" x:indent-with="  ">
2310Sunday, 06-Nov-94 08:49:37 GMT ; obsolete RFC 850 format
2311Sun Nov  6 08:49:37 1994       ; ANSI C's asctime() format
2312</artwork></figure>
2313<t>
2314   HTTP/1.1 clients and servers that parse a date value &MUST; accept
2315   all three formats (for compatibility with HTTP/1.0), though they &MUST;
2316   only generate the RFC 1123 format for representing HTTP-date values
2317   in header fields.
2318</t>
2319<t>
2320   All HTTP date/time stamps &MUST; be represented in Greenwich Mean Time
2321   (GMT), without exception. For the purposes of HTTP, GMT is exactly
2322   equal to UTC (Coordinated Universal Time). This is indicated in the
2323   first two formats by the inclusion of "GMT" as the three-letter
2324   abbreviation for time zone, and &MUST; be assumed when reading the
2325   asctime format. HTTP-date is case sensitive and &MUST-NOT; include
2326   additional whitespace beyond that specifically included as SP in the
2327   grammar.
2328</t>
2329<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="HTTP-date"/>
2330  <x:ref>HTTP-date</x:ref>    = <x:ref>rfc1123-date</x:ref> / <x:ref>obs-date</x:ref>
2331</artwork></figure>
2332<t anchor="preferred.date.format">
2333  <x:anchor-alias value="rfc1123-date"/>
2334  <x:anchor-alias value="time-of-day"/>
2335  <x:anchor-alias value="hour"/>
2336  <x:anchor-alias value="minute"/>
2337  <x:anchor-alias value="second"/>
2338  <x:anchor-alias value="day-name"/>
2339  <x:anchor-alias value="day"/>
2340  <x:anchor-alias value="month"/>
2341  <x:anchor-alias value="year"/>
2342  <x:anchor-alias value="GMT"/>
2343  Preferred format:
2344</t>
2345<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"/>
2346  <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>
2347  ; fixed length subset of the format defined in
2348  ; <xref target="RFC1123" x:fmt="of" x:sec="5.2.14"/>
2349 
2350  <x:ref>day-name</x:ref>     = <x:abnf-char-sequence>"Mon"</x:abnf-char-sequence> ; "Mon", case-sensitive
2351               / <x:abnf-char-sequence>"Tue"</x:abnf-char-sequence> ; "Tue", case-sensitive
2352               / <x:abnf-char-sequence>"Wed"</x:abnf-char-sequence> ; "Wed", case-sensitive
2353               / <x:abnf-char-sequence>"Thu"</x:abnf-char-sequence> ; "Thu", case-sensitive
2354               / <x:abnf-char-sequence>"Fri"</x:abnf-char-sequence> ; "Fri", case-sensitive
2355               / <x:abnf-char-sequence>"Sat"</x:abnf-char-sequence> ; "Sat", case-sensitive
2356               / <x:abnf-char-sequence>"Sun"</x:abnf-char-sequence> ; "Sun", case-sensitive
2357               
2358  <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>
2359               ; e.g., 02 Jun 1982
2360
2361  <x:ref>day</x:ref>          = 2<x:ref>DIGIT</x:ref>
2362  <x:ref>month</x:ref>        = <x:abnf-char-sequence>"Jan"</x:abnf-char-sequence> ; "Jan", case-sensitive
2363               / <x:abnf-char-sequence>"Feb"</x:abnf-char-sequence> ; "Feb", case-sensitive
2364               / <x:abnf-char-sequence>"Mar"</x:abnf-char-sequence> ; "Mar", case-sensitive
2365               / <x:abnf-char-sequence>"Apr"</x:abnf-char-sequence> ; "Apr", case-sensitive
2366               / <x:abnf-char-sequence>"May"</x:abnf-char-sequence> ; "May", case-sensitive
2367               / <x:abnf-char-sequence>"Jun"</x:abnf-char-sequence> ; "Jun", case-sensitive
2368               / <x:abnf-char-sequence>"Jul"</x:abnf-char-sequence> ; "Jul", case-sensitive
2369               / <x:abnf-char-sequence>"Aug"</x:abnf-char-sequence> ; "Aug", case-sensitive
2370               / <x:abnf-char-sequence>"Sep"</x:abnf-char-sequence> ; "Sep", case-sensitive
2371               / <x:abnf-char-sequence>"Oct"</x:abnf-char-sequence> ; "Oct", case-sensitive
2372               / <x:abnf-char-sequence>"Nov"</x:abnf-char-sequence> ; "Nov", case-sensitive
2373               / <x:abnf-char-sequence>"Dec"</x:abnf-char-sequence> ; "Dec", case-sensitive
2374  <x:ref>year</x:ref>         = 4<x:ref>DIGIT</x:ref>
2375
2376  <x:ref>GMT</x:ref>   = <x:abnf-char-sequence>"GMT"</x:abnf-char-sequence> ; "GMT", case-sensitive
2377
2378  <x:ref>time-of-day</x:ref>  = <x:ref>hour</x:ref> ":" <x:ref>minute</x:ref> ":" <x:ref>second</x:ref>
2379                 ; 00:00:00 - 23:59:59
2380                 
2381  <x:ref>hour</x:ref>         = 2<x:ref>DIGIT</x:ref>               
2382  <x:ref>minute</x:ref>       = 2<x:ref>DIGIT</x:ref>               
2383  <x:ref>second</x:ref>       = 2<x:ref>DIGIT</x:ref>               
2384</artwork></figure>
2385<t>
2386  The semantics of <x:ref>day-name</x:ref>, <x:ref>day</x:ref>,
2387  <x:ref>month</x:ref>, <x:ref>year</x:ref>, and <x:ref>time-of-day</x:ref> are the
2388  same as those defined for the RFC 5322 constructs
2389  with the corresponding name (<xref target="RFC5322" x:fmt="," x:sec="3.3"/>).
2390</t>
2391<t anchor="obsolete.date.formats">
2392  <x:anchor-alias value="obs-date"/>
2393  <x:anchor-alias value="rfc850-date"/>
2394  <x:anchor-alias value="asctime-date"/>
2395  <x:anchor-alias value="date1"/>
2396  <x:anchor-alias value="date2"/>
2397  <x:anchor-alias value="date3"/>
2398  <x:anchor-alias value="rfc1123-date"/>
2399  <x:anchor-alias value="day-name-l"/>
2400  Obsolete formats:
2401</t>
2402<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="obs-date"/>
2403  <x:ref>obs-date</x:ref>     = <x:ref>rfc850-date</x:ref> / <x:ref>asctime-date</x:ref> 
2404</artwork></figure>
2405<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="rfc850-date"/>
2406  <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>
2407  <x:ref>date2</x:ref>        = <x:ref>day</x:ref> "-" <x:ref>month</x:ref> "-" 2<x:ref>DIGIT</x:ref>
2408                 ; day-month-year (e.g., 02-Jun-82)
2409
2410  <x:ref>day-name-l</x:ref>   = <x:abnf-char-sequence>"Monday"</x:abnf-char-sequence> ; "Monday", case-sensitive
2411         / <x:abnf-char-sequence>"Tuesday"</x:abnf-char-sequence> ; "Tuesday", case-sensitive
2412         / <x:abnf-char-sequence>"Wednesday"</x:abnf-char-sequence> ; "Wednesday", case-sensitive
2413         / <x:abnf-char-sequence>"Thursday"</x:abnf-char-sequence> ; "Thursday", case-sensitive
2414         / <x:abnf-char-sequence>"Friday"</x:abnf-char-sequence> ; "Friday", case-sensitive
2415         / <x:abnf-char-sequence>"Saturday"</x:abnf-char-sequence> ; "Saturday", case-sensitive
2416         / <x:abnf-char-sequence>"Sunday"</x:abnf-char-sequence> ; "Sunday", case-sensitive
2417</artwork></figure>
2418<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="asctime-date"/>
2419  <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>
2420  <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> ))
2421                 ; month day (e.g., Jun  2)
2422</artwork></figure>
2423<x:note>
2424  <t>
2425    <x:h>Note:</x:h> Recipients of date values are encouraged to be robust in
2426    accepting date values that might have been sent by non-HTTP
2427    applications, as is sometimes the case when retrieving or posting
2428    messages via proxies/gateways to SMTP or NNTP.
2429  </t>
2430</x:note>
2431<x:note>
2432  <t>
2433    <x:h>Note:</x:h> HTTP requirements for the date/time stamp format apply only
2434    to their usage within the protocol stream. Clients and servers are
2435    not required to use these formats for user presentation, request
2436    logging, etc.
2437  </t>
2438</x:note>
2439</section>
2440
2441
2442<section title="Header Field Definitions" anchor="header.field.definitions">
2443<t>
2444   This section defines the syntax and semantics of HTTP/1.1 header fields
2445   related to request and response semantics.
2446</t>
2447
2448<section title="Allow" anchor="header.allow">
2449  <iref primary="true" item="Allow header field" x:for-anchor=""/>
2450  <iref primary="true" item="Header Fields" subitem="Allow" x:for-anchor=""/>
2451  <x:anchor-alias value="Allow"/>
2452<t>
2453   The "Allow" header field lists the set of methods advertised as
2454   supported by the target resource. The purpose of this field is strictly to
2455   inform the recipient of valid request methods associated with the resource.
2456</t>
2457<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/>
2458  <x:ref>Allow</x:ref> = #<x:ref>Method</x:ref>
2459</artwork></figure>
2460<t>
2461   Example of use:
2462</t>
2463<figure><artwork type="example">
2464  Allow: GET, HEAD, PUT
2465</artwork></figure>
2466<t>
2467   The actual set of allowed methods is defined by the origin server at the
2468   time of each request.
2469</t>
2470<t>
2471   A proxy &MUST-NOT; modify the Allow header field &mdash; it does not need to
2472   understand all the methods specified in order to handle them according to
2473   the generic message handling rules.
2474</t>
2475</section>
2476
2477<section title="Date" anchor="header.date">
2478  <iref primary="true" item="Date header field" x:for-anchor=""/>
2479  <iref primary="true" item="Header Fields" subitem="Date" x:for-anchor=""/>
2480  <x:anchor-alias value="Date"/>
2481<t>
2482   The "Date" header field represents the date and time at which
2483   the message was originated, having the same semantics as the Origination
2484   Date Field (orig-date) defined in <xref target="RFC5322" x:fmt="of" x:sec="3.6.1"/>.
2485   The field value is an HTTP-date, as defined in <xref target="http.date"/>;
2486   it &MUST; be sent in rfc1123-date format.
2487</t>
2488<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Date"/>
2489  <x:ref>Date</x:ref> = <x:ref>HTTP-date</x:ref>
2490</artwork></figure>
2491<t>
2492   An example is
2493</t>
2494<figure><artwork type="example">
2495  Date: Tue, 15 Nov 1994 08:12:31 GMT
2496</artwork></figure>
2497<t>
2498   Origin servers &MUST; include a Date header field in all responses,
2499   except in these cases:
2500  <list style="numbers">
2501      <t>If the response status code is 100 (Continue) or 101 (Switching
2502         Protocols), the response &MAY; include a Date header field, at
2503         the server's option.</t>
2504
2505      <t>If the response status code conveys a server error, e.g., 500
2506         (Internal Server Error) or 503 (Service Unavailable), and it is
2507         inconvenient or impossible to generate a valid Date.</t>
2508
2509      <t>If the server does not have a clock that can provide a
2510         reasonable approximation of the current time, its responses
2511         &MUST-NOT; include a Date header field.</t>
2512  </list>
2513</t>
2514<t>
2515   A received message that does not have a Date header field &MUST; be
2516   assigned one by the recipient if the message will be cached by that
2517   recipient.
2518</t>
2519<t>
2520   Clients can use the Date header field as well; in order to keep request
2521   messages small, they are advised not to include it when it doesn't convey
2522   any useful information (as it is usually the case for requests that do not
2523   contain a payload).
2524</t>
2525<t>
2526   The HTTP-date sent in a Date header field &SHOULD-NOT; represent a date and
2527   time subsequent to the generation of the message. It &SHOULD; represent
2528   the best available approximation of the date and time of message
2529   generation, unless the implementation has no means of generating a
2530   reasonably accurate date and time. In theory, the date ought to
2531   represent the moment just before the payload is generated. In
2532   practice, the date can be generated at any time during the message
2533   origination without affecting its semantic value.
2534</t>
2535</section>
2536
2537<section title="Expect" anchor="header.expect">
2538  <iref primary="true" item="Expect header field" x:for-anchor=""/>
2539  <iref primary="true" item="Header Fields" subitem="Expect" x:for-anchor=""/>
2540  <x:anchor-alias value="Expect"/>
2541  <x:anchor-alias value="expectation"/>
2542  <x:anchor-alias value="expectation-extension"/>
2543  <x:anchor-alias value="expect-params"/>
2544<t>
2545   The "Expect" header field is used to indicate that particular
2546   server behaviors are required by the client.
2547</t>
2548<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Expect"/><iref primary="true" item="Grammar" subitem="expectation"/><iref primary="true" item="Grammar" subitem="expectation-extension"/><iref primary="true" item="Grammar" subitem="expect-params"/>
2549  <x:ref>Expect</x:ref>       = 1#<x:ref>expectation</x:ref>
2550 
2551  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
2552  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
2553                           *<x:ref>expect-params</x:ref> ]
2554  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
2555</artwork></figure>
2556<t>
2557   A server that does not understand or is unable to comply with any of
2558   the expectation values in the Expect field of a request &MUST; respond
2559   with appropriate error status code. The server &MUST; respond with a 417
2560   (Expectation Failed) status code if any of the expectations cannot be met
2561   or, if there are other problems with the request, some other 4xx
2562   status code.
2563</t>
2564<t>
2565   This header field is defined with extensible syntax to allow for
2566   future extensions. If a server receives a request containing an
2567   Expect field that includes an expectation-extension that it does not
2568   support, it &MUST; respond with a 417 (Expectation Failed) status code.
2569</t>
2570<t>
2571   Comparison of expectation values is case-insensitive for unquoted
2572   tokens (including the 100-continue token), and is case-sensitive for
2573   quoted-string expectation-extensions.
2574</t>
2575<t>
2576   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
2577   return a 417 (Expectation Failed) status code if it receives a request
2578   with an expectation that it cannot meet. However, the Expect
2579   header field itself is end-to-end; it &MUST; be forwarded if the
2580   request is forwarded.
2581</t>
2582<t>
2583   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
2584   Expect header field.
2585</t>
2586<t>
2587   See &use100; for the use of the 100 (Continue) status code.
2588</t>
2589</section>
2590
2591<section title="From" anchor="header.from">
2592  <iref primary="true" item="From header field" x:for-anchor=""/>
2593  <iref primary="true" item="Header Fields" subitem="From" x:for-anchor=""/>
2594  <x:anchor-alias value="From"/>
2595  <x:anchor-alias value="mailbox"/>
2596<t>
2597   The "From" header field, if given, &SHOULD; contain an Internet
2598   e-mail address for the human user who controls the requesting user
2599   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
2600   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
2601</t>
2602<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/>
2603  <x:ref>From</x:ref>    = <x:ref>mailbox</x:ref>
2604 
2605  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2606</artwork></figure>
2607<t>
2608   An example is:
2609</t>
2610<figure><artwork type="example">
2611  From: webmaster@example.org
2612</artwork></figure>
2613<t>
2614   This header field &MAY; be used for logging purposes and as a means for
2615   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2616   be used as an insecure form of access protection. The interpretation
2617   of this field is that the request is being performed on behalf of the
2618   person given, who accepts responsibility for the method performed. In
2619   particular, robot agents &SHOULD; include this header field so that the
2620   person responsible for running the robot can be contacted if problems
2621   occur on the receiving end.
2622</t>
2623<t>
2624   The Internet e-mail address in this field &MAY; be separate from the
2625   Internet host which issued the request. For example, when a request
2626   is passed through a proxy the original issuer's address &SHOULD; be
2627   used.
2628</t>
2629<t>
2630   The client &SHOULD-NOT;  send the From header field without the user's
2631   approval, as it might conflict with the user's privacy interests or
2632   their site's security policy. It is strongly recommended that the
2633   user be able to disable, enable, and modify the value of this field
2634   at any time prior to a request.
2635</t>
2636</section>
2637
2638<section title="Location" anchor="header.location">
2639  <iref primary="true" item="Location header field" x:for-anchor=""/>
2640  <iref primary="true" item="Header Fields" subitem="Location" x:for-anchor=""/>
2641  <x:anchor-alias value="Location"/>
2642<t>
2643   The "Location" header field is used to identify a newly created
2644   resource, or to redirect the recipient to a different location for
2645   completion of the request.
2646</t>
2647<t>
2648   For 201 (Created) responses, the Location is the URI of the new resource
2649   which was created by the request. For 3xx responses, the location &SHOULD;
2650   indicate the server's preferred URI for automatic redirection to the
2651   resource.
2652</t>
2653<t>
2654   The field value consists of a single URI-reference. When it has the form
2655   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2656   the final value is computed by resolving it against the effective request
2657   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
2658</t>
2659<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/>
2660  <x:ref>Location</x:ref> = <x:ref>URI-reference</x:ref>
2661</artwork></figure>
2662<figure>
2663<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical spacing below, it's necessary this way for xml2rfc-->
2664<artwork type="example">
2665  Location: http://www.example.org/pub/WWW/People.html#tim
2666</artwork></figure><figure><artwork type="example">  Location: /index.html
2667</artwork></figure>
2668<t>
2669   There are circumstances in which a fragment identifier in a Location URI
2670   would not be appropriate. For instance, when it appears in a 201 Created
2671   response, where the Location header field specifies the URI for the entire
2672   created resource.
2673</t>
2674<x:note>
2675  <t>
2676    <x:h>Note:</x:h> This specification does not define precedence rules
2677    for the case where the original URI, as navigated to by the user
2678    agent, and the Location header field value both contain fragment
2679    identifiers. Thus be aware that including fragment identifiers might
2680    inconvenience anyone relying on the semantics of the original URI's
2681    fragment identifier.
2682  </t>
2683</x:note>
2684<x:note>
2685  <t>
2686    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2687    from Location in that the Content-Location identifies the most specific
2688    resource corresponding to the enclosed representation.
2689    It is therefore possible for a response to contain header fields for
2690    both Location and Content-Location.
2691  </t>
2692</x:note>
2693</section>
2694
2695<section title="Max-Forwards" anchor="header.max-forwards">
2696  <iref primary="true" item="Max-Forwards header field" x:for-anchor=""/>
2697  <iref primary="true" item="Header Fields" subitem="Max-Forwards" x:for-anchor=""/>
2698  <x:anchor-alias value="Max-Forwards"/>
2699<t>
2700   The "Max-Forwards" header field provides a mechanism with the
2701   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2702   methods to limit the number of times that the request is forwarded by
2703   proxies. This can be useful when the client is attempting to
2704   trace a request which appears to be failing or looping in mid-chain.
2705</t>
2706<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/>
2707  <x:ref>Max-Forwards</x:ref> = 1*<x:ref>DIGIT</x:ref>
2708</artwork></figure>
2709<t>
2710   The Max-Forwards value is a decimal integer indicating the remaining
2711   number of times this request message can be forwarded.
2712</t>
2713<t>
2714   Each recipient of a TRACE or OPTIONS request
2715   containing a Max-Forwards header field &MUST; check and update its
2716   value prior to forwarding the request. If the received value is zero
2717   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2718   respond as the final recipient. If the received Max-Forwards value is
2719   greater than zero, then the forwarded message &MUST; contain an updated
2720   Max-Forwards field with a value decremented by one (1).
2721</t>
2722<t>
2723   The Max-Forwards header field &MAY; be ignored for all other request
2724   methods.
2725</t>
2726</section>
2727
2728<section title="Referer" anchor="header.referer">
2729  <iref primary="true" item="Referer header field" x:for-anchor=""/>
2730  <iref primary="true" item="Header Fields" subitem="Referer" x:for-anchor=""/>
2731  <x:anchor-alias value="Referer"/>
2732<t>
2733   The "Referer" [sic] header field allows the client to specify the
2734   URI of the resource from which the effective request URI was obtained (the
2735   "referrer", although the header field is misspelled.).
2736</t>
2737<t>
2738   The Referer header field allows servers to generate lists of back-links to
2739   resources for interest, logging, optimized caching, etc. It also allows
2740   obsolete or mistyped links to be traced for maintenance. Some servers use
2741   Referer as a means of controlling where they allow links from (so-called
2742   "deep linking"), but legitimate requests do not always
2743   contain a Referer header field.
2744</t>
2745<t>
2746   If the effective request URI was obtained from a source that does not have its own
2747   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
2748   sent with the value "about:blank", or not be sent at all. Note that this
2749   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2750</t>
2751<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/>
2752  <x:ref>Referer</x:ref> = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2753</artwork></figure>
2754<t>
2755   Example:
2756</t>
2757<figure><artwork type="example">
2758  Referer: http://www.example.org/hypertext/Overview.html
2759</artwork></figure>
2760<t>
2761   If the field value is a relative URI, it &SHOULD; be interpreted
2762   relative to the effective request URI. The URI &MUST-NOT; include a fragment. See
2763   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2764</t>
2765</section>
2766
2767<section title="Retry-After" anchor="header.retry-after">
2768  <iref primary="true" item="Retry-After header field" x:for-anchor=""/>
2769  <iref primary="true" item="Header Fields" subitem="Retry-After" x:for-anchor=""/>
2770  <x:anchor-alias value="Retry-After"/>
2771<t>
2772   The header "Retry-After" field can be used with a 503 (Service
2773   Unavailable) response to indicate how long the service is expected to
2774   be unavailable to the requesting client. This field &MAY; also be used
2775   with any 3xx (Redirection) response to indicate the minimum time the
2776   user-agent is asked wait before issuing the redirected request.
2777</t>
2778<t>
2779   The value of this field can be either an HTTP-date or an integer number
2780   of seconds (in decimal) after the time of the response.
2781</t>
2782<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/>
2783  <x:ref>Retry-After</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2784</artwork></figure>
2785<t anchor="rule.delta-seconds">
2786  <x:anchor-alias value="delta-seconds"/>
2787   Time spans are non-negative decimal integers, representing time in
2788   seconds.
2789</t>
2790<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2791  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2792</artwork></figure>
2793<t>
2794   Two examples of its use are
2795</t>
2796<figure><artwork type="example">
2797  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2798  Retry-After: 120
2799</artwork></figure>
2800<t>
2801   In the latter example, the delay is 2 minutes.
2802</t>
2803</section>
2804
2805<section title="Server" anchor="header.server">
2806  <iref primary="true" item="Server header field" x:for-anchor=""/>
2807  <iref primary="true" item="Header Fields" subitem="Server" x:for-anchor=""/>
2808  <x:anchor-alias value="Server"/>
2809<t>
2810   The "Server" header field contains information about the
2811   software used by the origin server to handle the request.
2812</t>
2813<t>
2814   The field can contain multiple product tokens (&product-tokens;) and
2815   comments (&header-fields;) identifying the server and any significant
2816   subproducts. The product tokens are listed in order of their significance
2817   for identifying the application.
2818</t>
2819<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/>
2820  <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> ) )
2821</artwork></figure>
2822<t>
2823   Example:
2824</t>
2825<figure><artwork type="example">
2826  Server: CERN/3.0 libwww/2.17
2827</artwork></figure>
2828<t>
2829   If the response is being forwarded through a proxy, the proxy
2830   application &MUST-NOT; modify the Server header field. Instead, it
2831   &MUST; include a Via field (as described in &header-via;).
2832</t>
2833<x:note>
2834  <t>
2835    <x:h>Note:</x:h> Revealing the specific software version of the server might
2836    allow the server machine to become more vulnerable to attacks
2837    against software that is known to contain security holes. Server
2838    implementors are encouraged to make this field a configurable
2839    option.
2840  </t>
2841</x:note>
2842</section>
2843
2844<section title="User-Agent" anchor="header.user-agent">
2845  <iref primary="true" item="User-Agent header field" x:for-anchor=""/>
2846  <iref primary="true" item="Header Fields" subitem="User-Agent" x:for-anchor=""/>
2847  <x:anchor-alias value="User-Agent"/>
2848<t>
2849   The "User-Agent" header field contains information about the user
2850   agent originating the request. User agents &SHOULD; include this field with
2851   requests.
2852</t>
2853<t>
2854   Typically, it is used for statistical purposes, the tracing of protocol
2855   violations, and tailoring responses to avoid particular user agent
2856   limitations.
2857</t>
2858<t>
2859   The field can contain multiple product tokens (&product-tokens;)
2860   and comments (&header-fields;) identifying the agent and its
2861   significant subproducts. By convention, the product tokens are listed in
2862   order of their significance for identifying the application.
2863</t>
2864<t>
2865   Because this field is usually sent on every request a user agent makes,
2866   implementations are encouraged not to include needlessly fine-grained
2867   detail, and to limit (or even prohibit) the addition of subproducts by third
2868   parties. Overly long and detailed User-Agent field values make requests
2869   larger and can also be used to identify ("fingerprint") the user against
2870   their wishes.
2871</t>
2872<t>
2873   Likewise, implementations are encouraged not to use the product tokens of
2874   other implementations in order to declare compatibility with them, as this
2875   circumvents the purpose of the field. Finally, they are encouraged not to
2876   use comments to identify products; doing so makes the field value more
2877   difficult to parse.
2878</t>
2879<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/>
2880  <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> ) )
2881</artwork></figure>
2882<t>
2883   Example:
2884</t>
2885<figure><artwork type="example">
2886  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2887</artwork></figure>
2888</section>
2889
2890</section>
2891
2892<section title="IANA Considerations" anchor="IANA.considerations">
2893
2894<section title="Method Registry" anchor="method.registration">
2895<t>
2896  The registration procedure for HTTP request methods is defined by
2897  <xref target="method.registry"/> of this document.
2898</t>
2899<t>
2900   The HTTP Method Registry shall be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2901   and be populated with the registrations below:
2902</t>
2903<?BEGININC p2-semantics.iana-methods ?>
2904<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2905<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2906   <ttcol>Method</ttcol>
2907   <ttcol>Safe</ttcol>
2908   <ttcol>Reference</ttcol>
2909   <c>CONNECT</c>
2910   <c>no</c>
2911   <c>
2912      <xref target="CONNECT"/>
2913   </c>
2914   <c>DELETE</c>
2915   <c>no</c>
2916   <c>
2917      <xref target="DELETE"/>
2918   </c>
2919   <c>GET</c>
2920   <c>yes</c>
2921   <c>
2922      <xref target="GET"/>
2923   </c>
2924   <c>HEAD</c>
2925   <c>yes</c>
2926   <c>
2927      <xref target="HEAD"/>
2928   </c>
2929   <c>OPTIONS</c>
2930   <c>yes</c>
2931   <c>
2932      <xref target="OPTIONS"/>
2933   </c>
2934   <c>POST</c>
2935   <c>no</c>
2936   <c>
2937      <xref target="POST"/>
2938   </c>
2939   <c>PUT</c>
2940   <c>no</c>
2941   <c>
2942      <xref target="PUT"/>
2943   </c>
2944   <c>TRACE</c>
2945   <c>yes</c>
2946   <c>
2947      <xref target="TRACE"/>
2948   </c>
2949</texttable>
2950<!--(END)-->
2951<?ENDINC p2-semantics.iana-methods ?>
2952</section>
2953
2954<section title="Status Code Registry" anchor="status.code.registration">
2955<t>
2956   The registration procedure for HTTP Status Codes &mdash; previously defined
2957   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> &mdash; is now defined
2958   by <xref target="status.code.registry"/> of this document.
2959</t>
2960<t>
2961   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2962   shall be updated with the registrations below:
2963</t>
2964<?BEGININC p2-semantics.iana-status-codes ?>
2965<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2966<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2967   <ttcol>Value</ttcol>
2968   <ttcol>Description</ttcol>
2969   <ttcol>Reference</ttcol>
2970   <c>100</c>
2971   <c>Continue</c>
2972   <c>
2973      <xref target="status.100"/>
2974   </c>
2975   <c>101</c>
2976   <c>Switching Protocols</c>
2977   <c>
2978      <xref target="status.101"/>
2979   </c>
2980   <c>200</c>
2981   <c>OK</c>
2982   <c>
2983      <xref target="status.200"/>
2984   </c>
2985   <c>201</c>
2986   <c>Created</c>
2987   <c>
2988      <xref target="status.201"/>
2989   </c>
2990   <c>202</c>
2991   <c>Accepted</c>
2992   <c>
2993      <xref target="status.202"/>
2994   </c>
2995   <c>203</c>
2996   <c>Non-Authoritative Information</c>
2997   <c>
2998      <xref target="status.203"/>
2999   </c>
3000   <c>204</c>
3001   <c>No Content</c>
3002   <c>
3003      <xref target="status.204"/>
3004   </c>
3005   <c>205</c>
3006   <c>Reset Content</c>
3007   <c>
3008      <xref target="status.205"/>
3009   </c>
3010   <c>300</c>
3011   <c>Multiple Choices</c>
3012   <c>
3013      <xref target="status.300"/>
3014   </c>
3015   <c>301</c>
3016   <c>Moved Permanently</c>
3017   <c>
3018      <xref target="status.301"/>
3019   </c>
3020   <c>302</c>
3021   <c>Found</c>
3022   <c>
3023      <xref target="status.302"/>
3024   </c>
3025   <c>303</c>
3026   <c>See Other</c>
3027   <c>
3028      <xref target="status.303"/>
3029   </c>
3030   <c>305</c>
3031   <c>Use Proxy</c>
3032   <c>
3033      <xref target="status.305"/>
3034   </c>
3035   <c>306</c>
3036   <c>(Unused)</c>
3037   <c>
3038      <xref target="status.306"/>
3039   </c>
3040   <c>307</c>
3041   <c>Temporary Redirect</c>
3042   <c>
3043      <xref target="status.307"/>
3044   </c>
3045   <c>400</c>
3046   <c>Bad Request</c>
3047   <c>
3048      <xref target="status.400"/>
3049   </c>
3050   <c>402</c>
3051   <c>Payment Required</c>
3052   <c>
3053      <xref target="status.402"/>
3054   </c>
3055   <c>403</c>
3056   <c>Forbidden</c>
3057   <c>
3058      <xref target="status.403"/>
3059   </c>
3060   <c>404</c>
3061   <c>Not Found</c>
3062   <c>
3063      <xref target="status.404"/>
3064   </c>
3065   <c>405</c>
3066   <c>Method Not Allowed</c>
3067   <c>
3068      <xref target="status.405"/>
3069   </c>
3070   <c>406</c>
3071   <c>Not Acceptable</c>
3072   <c>
3073      <xref target="status.406"/>
3074   </c>
3075   <c>407</c>
3076   <c>Proxy Authentication Required</c>
3077   <c>
3078      <xref target="status.407"/>
3079   </c>
3080   <c>408</c>
3081   <c>Request Timeout</c>
3082   <c>
3083      <xref target="status.408"/>
3084   </c>
3085   <c>409</c>
3086   <c>Conflict</c>
3087   <c>
3088      <xref target="status.409"/>
3089   </c>
3090   <c>410</c>
3091   <c>Gone</c>
3092   <c>
3093      <xref target="status.410"/>
3094   </c>
3095   <c>411</c>
3096   <c>Length Required</c>
3097   <c>
3098      <xref target="status.411"/>
3099   </c>
3100   <c>413</c>
3101   <c>Request Representation Too Large</c>
3102   <c>
3103      <xref target="status.413"/>
3104   </c>
3105   <c>414</c>
3106   <c>URI Too Long</c>
3107   <c>
3108      <xref target="status.414"/>
3109   </c>
3110   <c>415</c>
3111   <c>Unsupported Media Type</c>
3112   <c>
3113      <xref target="status.415"/>
3114   </c>
3115   <c>417</c>
3116   <c>Expectation Failed</c>
3117   <c>
3118      <xref target="status.417"/>
3119   </c>
3120   <c>426</c>
3121   <c>Upgrade Required</c>
3122   <c>
3123      <xref target="status.426"/>
3124   </c>
3125   <c>500</c>
3126   <c>Internal Server Error</c>
3127   <c>
3128      <xref target="status.500"/>
3129   </c>
3130   <c>501</c>
3131   <c>Not Implemented</c>
3132   <c>
3133      <xref target="status.501"/>
3134   </c>
3135   <c>502</c>
3136   <c>Bad Gateway</c>
3137   <c>
3138      <xref target="status.502"/>
3139   </c>
3140   <c>503</c>
3141   <c>Service Unavailable</c>
3142   <c>
3143      <xref target="status.503"/>
3144   </c>
3145   <c>504</c>
3146   <c>Gateway Timeout</c>
3147   <c>
3148      <xref target="status.504"/>
3149   </c>
3150   <c>505</c>
3151   <c>HTTP Version Not Supported</c>
3152   <c>
3153      <xref target="status.505"/>
3154   </c>
3155</texttable>
3156<!--(END)-->
3157<?ENDINC p2-semantics.iana-status-codes ?>
3158</section>
3159<section title="Header Field Registration" anchor="header.field.registration">
3160<t>
3161   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
3162   with the permanent registrations below (see <xref target="RFC3864"/>):
3163</t>
3164<?BEGININC p2-semantics.iana-headers ?>
3165<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
3166<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
3167   <ttcol>Header Field Name</ttcol>
3168   <ttcol>Protocol</ttcol>
3169   <ttcol>Status</ttcol>
3170   <ttcol>Reference</ttcol>
3171
3172   <c>Allow</c>
3173   <c>http</c>
3174   <c>standard</c>
3175   <c>
3176      <xref target="header.allow"/>
3177   </c>
3178   <c>Date</c>
3179   <c>http</c>
3180   <c>standard</c>
3181   <c>
3182      <xref target="header.date"/>
3183   </c>
3184   <c>Expect</c>
3185   <c>http</c>
3186   <c>standard</c>
3187   <c>
3188      <xref target="header.expect"/>
3189   </c>
3190   <c>From</c>
3191   <c>http</c>
3192   <c>standard</c>
3193   <c>
3194      <xref target="header.from"/>
3195   </c>
3196   <c>Location</c>
3197   <c>http</c>
3198   <c>standard</c>
3199   <c>
3200      <xref target="header.location"/>
3201   </c>
3202   <c>Max-Forwards</c>
3203   <c>http</c>
3204   <c>standard</c>
3205   <c>
3206      <xref target="header.max-forwards"/>
3207   </c>
3208   <c>Referer</c>
3209   <c>http</c>
3210   <c>standard</c>
3211   <c>
3212      <xref target="header.referer"/>
3213   </c>
3214   <c>Retry-After</c>
3215   <c>http</c>
3216   <c>standard</c>
3217   <c>
3218      <xref target="header.retry-after"/>
3219   </c>
3220   <c>Server</c>
3221   <c>http</c>
3222   <c>standard</c>
3223   <c>
3224      <xref target="header.server"/>
3225   </c>
3226   <c>User-Agent</c>
3227   <c>http</c>
3228   <c>standard</c>
3229   <c>
3230      <xref target="header.user-agent"/>
3231   </c>
3232</texttable>
3233<!--(END)-->
3234<?ENDINC p2-semantics.iana-headers ?>
3235<t>
3236   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
3237</t>
3238</section>
3239</section>
3240
3241<section title="Security Considerations" anchor="security.considerations">
3242<t>
3243   This section is meant to inform application developers, information
3244   providers, and users of the security limitations in HTTP/1.1 as
3245   described by this document. The discussion does not include
3246   definitive solutions to the problems revealed, though it does make
3247   some suggestions for reducing security risks.
3248</t>
3249
3250<section title="Transfer of Sensitive Information" anchor="security.sensitive">
3251<t>
3252   Like any generic data transfer protocol, HTTP cannot regulate the
3253   content of the data that is transferred, nor is there any a priori
3254   method of determining the sensitivity of any particular piece of
3255   information within the context of any given request. Therefore,
3256   applications &SHOULD; supply as much control over this information as
3257   possible to the provider of that information. Four header fields are
3258   worth special mention in this context: Server, Via, Referer and From.
3259</t>
3260<t>
3261   Revealing the specific software version of the server might allow the
3262   server machine to become more vulnerable to attacks against software
3263   that is known to contain security holes. Implementors &SHOULD; make the
3264   Server header field a configurable option.
3265</t>
3266<t>
3267   Proxies which serve as a portal through a network firewall &SHOULD;
3268   take special precautions regarding the transfer of header information
3269   that identifies the hosts behind the firewall. In particular, they
3270   &SHOULD; remove, or replace with sanitized versions, any Via fields
3271   generated behind the firewall.
3272</t>
3273<t>
3274   The Referer header field allows reading patterns to be studied and reverse
3275   links drawn. Although it can be very useful, its power can be abused
3276   if user details are not separated from the information contained in
3277   the Referer. Even when the personal information has been removed, the
3278   Referer header field might indicate a private document's URI whose
3279   publication would be inappropriate.
3280</t>
3281<t>
3282   The information sent in the From field might conflict with the user's
3283   privacy interests or their site's security policy, and hence it
3284   &SHOULD-NOT;  be transmitted without the user being able to disable,
3285   enable, and modify the contents of the field. The user &MUST; be able
3286   to set the contents of this field within a user preference or
3287   application defaults configuration.
3288</t>
3289<t>
3290   We suggest, though do not require, that a convenient toggle interface
3291   be provided for the user to enable or disable the sending of From and
3292   Referer information.
3293</t>
3294<t>
3295   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref
3296   target="header.server"/>) header fields can sometimes be used to determine
3297   that a specific client or server have a particular security hole which might
3298   be exploited. Unfortunately, this same information is often used for other
3299   valuable purposes for which HTTP currently has no better mechanism.
3300</t>
3301<t>
3302   Furthermore, the User-Agent header field may contain enough entropy to be
3303   used, possibly in conjunction with other material, to uniquely identify the
3304   user.
3305</t>
3306<t>
3307   Some request methods, like TRACE (<xref target="TRACE"/>), expose information
3308   that was sent in request header fields within the body of their response.
3309   Clients &SHOULD; be careful with sensitive information, like Cookies,
3310   Authorization credentials, and other header fields that might be used to
3311   collect data from the client.
3312</t> 
3313</section>
3314
3315<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
3316<t>
3317   Because the source of a link might be private information or might
3318   reveal an otherwise private information source, it is strongly
3319   recommended that the user be able to select whether or not the
3320   Referer field is sent. For example, a browser client could have a
3321   toggle switch for browsing openly/anonymously, which would
3322   respectively enable/disable the sending of Referer and From
3323   information.
3324</t>
3325<t>
3326   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
3327   HTTP request if the referring page was transferred with a secure
3328   protocol.
3329</t>
3330<t>
3331   Authors of services &SHOULD-NOT; use GET-based forms for the submission of
3332   sensitive data because that data will be placed in the request-target. Many
3333   existing servers, proxies, and user agents log or display the request-target
3334   in places where it might be visible to third parties. Such services can
3335   use POST-based form submission instead.
3336</t>
3337</section>
3338
3339<section title="Location Headers and Spoofing" anchor="location.spoofing">
3340<t>
3341   If a single server supports multiple organizations that do not trust
3342   one another, then it &MUST; check the values of Location and Content-Location
3343   header fields in responses that are generated under control of
3344   said organizations to make sure that they do not attempt to
3345   invalidate resources over which they have no authority.
3346</t>
3347</section>
3348
3349<section title="Security Considerations for CONNECT">
3350<t>
3351   Since tunneled data is opaque to the proxy, there are additional
3352   risks to tunneling to other well-known or reserved ports.
3353   A HTTP client CONNECTing to port 25 could relay spam
3354   via SMTP, for example. As such, proxies &SHOULD; restrict CONNECT
3355   access to a small number of known ports.
3356</t>
3357</section>
3358
3359</section>
3360
3361<section title="Acknowledgments" anchor="acks">
3362<t>
3363  See &acks;.
3364</t>
3365</section>
3366</middle>
3367<back>
3368
3369<references title="Normative References">
3370
3371<reference anchor="Part1">
3372  <front>
3373    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
3374    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3375      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3376      <address><email>fielding@gbiv.com</email></address>
3377    </author>
3378    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3379      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3380      <address><email>jg@freedesktop.org</email></address>
3381    </author>
3382    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3383      <organization abbrev="HP">Hewlett-Packard Company</organization>
3384      <address><email>JeffMogul@acm.org</email></address>
3385    </author>
3386    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3387      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3388      <address><email>henrikn@microsoft.com</email></address>
3389    </author>
3390    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3391      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3392      <address><email>LMM@acm.org</email></address>
3393    </author>
3394    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3395      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3396      <address><email>paulle@microsoft.com</email></address>
3397    </author>
3398    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3399      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3400      <address><email>timbl@w3.org</email></address>
3401    </author>
3402    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3403      <organization abbrev="W3C">World Wide Web Consortium</organization>
3404      <address><email>ylafon@w3.org</email></address>
3405    </author>
3406    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3407      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3408      <address><email>julian.reschke@greenbytes.de</email></address>
3409    </author>
3410    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3411  </front>
3412  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
3413  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
3414</reference>
3415
3416<reference anchor="Part3">
3417  <front>
3418    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
3419    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3420      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3421      <address><email>fielding@gbiv.com</email></address>
3422    </author>
3423    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3424      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3425      <address><email>jg@freedesktop.org</email></address>
3426    </author>
3427    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3428      <organization abbrev="HP">Hewlett-Packard Company</organization>
3429      <address><email>JeffMogul@acm.org</email></address>
3430    </author>
3431    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3432      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3433      <address><email>henrikn@microsoft.com</email></address>
3434    </author>
3435    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3436      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3437      <address><email>LMM@acm.org</email></address>
3438    </author>
3439    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3440      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3441      <address><email>paulle@microsoft.com</email></address>
3442    </author>
3443    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3444      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3445      <address><email>timbl@w3.org</email></address>
3446    </author>
3447    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3448      <organization abbrev="W3C">World Wide Web Consortium</organization>
3449      <address><email>ylafon@w3.org</email></address>
3450    </author>
3451    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3452      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3453      <address><email>julian.reschke@greenbytes.de</email></address>
3454    </author>
3455    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3456  </front>
3457  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
3458  <x:source href="p3-payload.xml" basename="p3-payload"/>
3459</reference>
3460
3461<reference anchor="Part4">
3462  <front>
3463    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
3464    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3465      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3466      <address><email>fielding@gbiv.com</email></address>
3467    </author>
3468    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3469      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3470      <address><email>jg@freedesktop.org</email></address>
3471    </author>
3472    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3473      <organization abbrev="HP">Hewlett-Packard Company</organization>
3474      <address><email>JeffMogul@acm.org</email></address>
3475    </author>
3476    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3477      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3478      <address><email>henrikn@microsoft.com</email></address>
3479    </author>
3480    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3481      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3482      <address><email>LMM@acm.org</email></address>
3483    </author>
3484    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3485      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3486      <address><email>paulle@microsoft.com</email></address>
3487    </author>
3488    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3489      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3490      <address><email>timbl@w3.org</email></address>
3491    </author>
3492    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3493      <organization abbrev="W3C">World Wide Web Consortium</organization>
3494      <address><email>ylafon@w3.org</email></address>
3495    </author>
3496    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3497      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3498      <address><email>julian.reschke@greenbytes.de</email></address>
3499    </author>
3500    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3501  </front>
3502  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
3503  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
3504</reference>
3505
3506<reference anchor="Part5">
3507  <front>
3508    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
3509    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3510      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3511      <address><email>fielding@gbiv.com</email></address>
3512    </author>
3513    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3514      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3515      <address><email>jg@freedesktop.org</email></address>
3516    </author>
3517    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3518      <organization abbrev="HP">Hewlett-Packard Company</organization>
3519      <address><email>JeffMogul@acm.org</email></address>
3520    </author>
3521    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3522      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3523      <address><email>henrikn@microsoft.com</email></address>
3524    </author>
3525    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3526      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3527      <address><email>LMM@acm.org</email></address>
3528    </author>
3529    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3530      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3531      <address><email>paulle@microsoft.com</email></address>
3532    </author>
3533    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3534      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3535      <address><email>timbl@w3.org</email></address>
3536    </author>
3537    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3538      <organization abbrev="W3C">World Wide Web Consortium</organization>
3539      <address><email>ylafon@w3.org</email></address>
3540    </author>
3541    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3542      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3543      <address><email>julian.reschke@greenbytes.de</email></address>
3544    </author>
3545    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3546  </front>
3547  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
3548  <x:source href="p5-range.xml" basename="p5-range"/>
3549</reference>
3550
3551<reference anchor="Part6">
3552  <front>
3553    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
3554    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3555      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3556      <address><email>fielding@gbiv.com</email></address>
3557    </author>
3558    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3559      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3560      <address><email>jg@freedesktop.org</email></address>
3561    </author>
3562    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3563      <organization abbrev="HP">Hewlett-Packard Company</organization>
3564      <address><email>JeffMogul@acm.org</email></address>
3565    </author>
3566    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3567      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3568      <address><email>henrikn@microsoft.com</email></address>
3569    </author>
3570    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3571      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3572      <address><email>LMM@acm.org</email></address>
3573    </author>
3574    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3575      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3576      <address><email>paulle@microsoft.com</email></address>
3577    </author>
3578    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3579      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3580      <address><email>timbl@w3.org</email></address>
3581    </author>
3582    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3583      <organization abbrev="W3C">World Wide Web Consortium</organization>
3584      <address><email>ylafon@w3.org</email></address>
3585    </author>
3586    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
3587      <organization>Rackspace</organization>
3588      <address><email>mnot@mnot.net</email></address>
3589    </author>
3590    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3591      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3592      <address><email>julian.reschke@greenbytes.de</email></address>
3593    </author>
3594    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3595  </front>
3596  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
3597  <x:source href="p6-cache.xml" basename="p6-cache"/>
3598</reference>
3599
3600<reference anchor="Part7">
3601  <front>
3602    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
3603    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3604      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3605      <address><email>fielding@gbiv.com</email></address>
3606    </author>
3607    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3608      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3609      <address><email>jg@freedesktop.org</email></address>
3610    </author>
3611    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3612      <organization abbrev="HP">Hewlett-Packard Company</organization>
3613      <address><email>JeffMogul@acm.org</email></address>
3614    </author>
3615    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3616      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3617      <address><email>henrikn@microsoft.com</email></address>
3618    </author>
3619    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3620      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3621      <address><email>LMM@acm.org</email></address>
3622    </author>
3623    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3624      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3625      <address><email>paulle@microsoft.com</email></address>
3626    </author>
3627    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3628      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3629      <address><email>timbl@w3.org</email></address>
3630    </author>
3631    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3632      <organization abbrev="W3C">World Wide Web Consortium</organization>
3633      <address><email>ylafon@w3.org</email></address>
3634    </author>
3635    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3636      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3637      <address><email>julian.reschke@greenbytes.de</email></address>
3638    </author>
3639    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3640  </front>
3641  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3642  <x:source href="p7-auth.xml" basename="p7-auth"/>
3643</reference>
3644
3645<reference anchor="RFC2119">
3646  <front>
3647    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3648    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3649      <organization>Harvard University</organization>
3650      <address><email>sob@harvard.edu</email></address>
3651    </author>
3652    <date month="March" year="1997"/>
3653  </front>
3654  <seriesInfo name="BCP" value="14"/>
3655  <seriesInfo name="RFC" value="2119"/>
3656</reference>
3657
3658<reference anchor="RFC3986">
3659 <front>
3660  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3661  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3662    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3663    <address>
3664       <email>timbl@w3.org</email>
3665       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3666    </address>
3667  </author>
3668  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3669    <organization abbrev="Day Software">Day Software</organization>
3670    <address>
3671      <email>fielding@gbiv.com</email>
3672      <uri>http://roy.gbiv.com/</uri>
3673    </address>
3674  </author>
3675  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3676    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3677    <address>
3678      <email>LMM@acm.org</email>
3679      <uri>http://larry.masinter.net/</uri>
3680    </address>
3681  </author>
3682  <date month='January' year='2005'></date>
3683 </front>
3684 <seriesInfo name="STD" value="66"/>
3685 <seriesInfo name="RFC" value="3986"/>
3686</reference>
3687
3688<reference anchor="RFC5234">
3689  <front>
3690    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3691    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3692      <organization>Brandenburg InternetWorking</organization>
3693      <address>
3694        <email>dcrocker@bbiw.net</email>
3695      </address> 
3696    </author>
3697    <author initials="P." surname="Overell" fullname="Paul Overell">
3698      <organization>THUS plc.</organization>
3699      <address>
3700        <email>paul.overell@thus.net</email>
3701      </address>
3702    </author>
3703    <date month="January" year="2008"/>
3704  </front>
3705  <seriesInfo name="STD" value="68"/>
3706  <seriesInfo name="RFC" value="5234"/>
3707</reference>
3708
3709</references>
3710
3711<references title="Informative References">
3712
3713<reference anchor="RFC1123">
3714  <front>
3715    <title>Requirements for Internet Hosts - Application and Support</title>
3716    <author initials="R." surname="Braden" fullname="Robert Braden">
3717      <organization>University of Southern California (USC), Information Sciences Institute</organization>
3718      <address><email>Braden@ISI.EDU</email></address>
3719    </author>
3720    <date month="October" year="1989"/>
3721  </front>
3722  <seriesInfo name="STD" value="3"/>
3723  <seriesInfo name="RFC" value="1123"/>
3724</reference>
3725
3726<reference anchor="RFC1945">
3727  <front>
3728    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3729    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3730      <organization>MIT, Laboratory for Computer Science</organization>
3731      <address><email>timbl@w3.org</email></address>
3732    </author>
3733    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3734      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3735      <address><email>fielding@ics.uci.edu</email></address>
3736    </author>
3737    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3738      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3739      <address><email>frystyk@w3.org</email></address>
3740    </author>
3741    <date month="May" year="1996"/>
3742  </front>
3743  <seriesInfo name="RFC" value="1945"/>
3744</reference>
3745
3746<reference anchor="RFC2068">
3747  <front>
3748    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3749    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3750      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3751      <address><email>fielding@ics.uci.edu</email></address>
3752    </author>
3753    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3754      <organization>MIT Laboratory for Computer Science</organization>
3755      <address><email>jg@w3.org</email></address>
3756    </author>
3757    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3758      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3759      <address><email>mogul@wrl.dec.com</email></address>
3760    </author>
3761    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3762      <organization>MIT Laboratory for Computer Science</organization>
3763      <address><email>frystyk@w3.org</email></address>
3764    </author>
3765    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3766      <organization>MIT Laboratory for Computer Science</organization>
3767      <address><email>timbl@w3.org</email></address>
3768    </author>
3769    <date month="January" year="1997"/>
3770  </front>
3771  <seriesInfo name="RFC" value="2068"/>
3772</reference>
3773
3774<reference anchor="RFC2616">
3775  <front>
3776    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3777    <author initials="R." surname="Fielding" fullname="R. Fielding">
3778      <organization>University of California, Irvine</organization>
3779      <address><email>fielding@ics.uci.edu</email></address>
3780    </author>
3781    <author initials="J." surname="Gettys" fullname="J. Gettys">
3782      <organization>W3C</organization>
3783      <address><email>jg@w3.org</email></address>
3784    </author>
3785    <author initials="J." surname="Mogul" fullname="J. Mogul">
3786      <organization>Compaq Computer Corporation</organization>
3787      <address><email>mogul@wrl.dec.com</email></address>
3788    </author>
3789    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3790      <organization>MIT Laboratory for Computer Science</organization>
3791      <address><email>frystyk@w3.org</email></address>
3792    </author>
3793    <author initials="L." surname="Masinter" fullname="L. Masinter">
3794      <organization>Xerox Corporation</organization>
3795      <address><email>masinter@parc.xerox.com</email></address>
3796    </author>
3797    <author initials="P." surname="Leach" fullname="P. Leach">
3798      <organization>Microsoft Corporation</organization>
3799      <address><email>paulle@microsoft.com</email></address>
3800    </author>
3801    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3802      <organization>W3C</organization>
3803      <address><email>timbl@w3.org</email></address>
3804    </author>
3805    <date month="June" year="1999"/>
3806  </front>
3807  <seriesInfo name="RFC" value="2616"/>
3808</reference>
3809
3810<reference anchor='RFC2817'>
3811  <front>
3812    <title>Upgrading to TLS Within HTTP/1.1</title>
3813    <author initials='R.' surname='Khare' fullname='R. Khare'>
3814      <organization>4K Associates / UC Irvine</organization>
3815      <address><email>rohit@4K-associates.com</email></address>
3816    </author>
3817    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3818      <organization>Agranat Systems, Inc.</organization>
3819      <address><email>lawrence@agranat.com</email></address>
3820    </author>
3821    <date year='2000' month='May' />
3822  </front>
3823  <seriesInfo name='RFC' value='2817' />
3824</reference>
3825
3826<reference anchor='RFC3864'>
3827  <front>
3828    <title>Registration Procedures for Message Header Fields</title>
3829    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3830      <organization>Nine by Nine</organization>
3831      <address><email>GK-IETF@ninebynine.org</email></address>
3832    </author>
3833    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3834      <organization>BEA Systems</organization>
3835      <address><email>mnot@pobox.com</email></address>
3836    </author>
3837    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3838      <organization>HP Labs</organization>
3839      <address><email>JeffMogul@acm.org</email></address>
3840    </author>
3841    <date year='2004' month='September' />
3842  </front>
3843  <seriesInfo name='BCP' value='90' />
3844  <seriesInfo name='RFC' value='3864' />
3845</reference>
3846
3847<reference anchor='RFC5226'>
3848  <front>
3849    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3850    <author initials='T.' surname='Narten' fullname='T. Narten'>
3851      <organization>IBM</organization>
3852      <address><email>narten@us.ibm.com</email></address>
3853    </author>
3854    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3855      <organization>Google</organization>
3856      <address><email>Harald@Alvestrand.no</email></address>
3857    </author>
3858    <date year='2008' month='May' />
3859  </front>
3860  <seriesInfo name='BCP' value='26' />
3861  <seriesInfo name='RFC' value='5226' />
3862</reference>
3863
3864<reference anchor="RFC5322">
3865  <front>
3866    <title>Internet Message Format</title>
3867    <author initials="P." surname="Resnick" fullname="P. Resnick">
3868      <organization>Qualcomm Incorporated</organization>
3869    </author>
3870    <date year="2008" month="October"/>
3871  </front> 
3872  <seriesInfo name="RFC" value="5322"/>
3873</reference>
3874
3875<reference anchor='RFC5789'>
3876  <front>
3877    <title>PATCH Method for HTTP</title>
3878    <author initials='L.' surname='Dusseault' fullname='L. Dusseault'>
3879      <organization>Linden Lab</organization>
3880    </author>
3881    <author initials='J.' surname='Snell' fullname='J. Snell' />
3882    <date year='2010' month='March' />
3883  </front>
3884  <seriesInfo name='RFC' value='5789' />
3885</reference>
3886
3887<reference anchor="RFC5987">
3888        <front>
3889    <title>Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters</title>
3890    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke">
3891      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3892      <address>
3893        <postal>
3894          <street>Hafenweg 16</street>
3895          <city>Muenster</city><region>NW</region><code>48155</code>
3896          <country>Germany</country>
3897        </postal>
3898        <email>julian.reschke@greenbytes.de</email>     
3899        <uri>http://greenbytes.de/tech/webdav/</uri>   
3900      </address>
3901    </author>
3902    <date month="August" year="2010"/>
3903  </front>
3904  <seriesInfo name="RFC" value="5987"/>
3905</reference>
3906
3907</references>
3908
3909<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3910<t>
3911  This document takes over the Status Code Registry, previously defined
3912  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3913  (<xref target="status.code.registry"/>)
3914</t>
3915<t>
3916  Clarify definition of POST.
3917  (<xref target="POST"/>)
3918</t>
3919<t>
3920  Remove requirement to handle all Content-* header fields; ban use of
3921  Content-Range with PUT.
3922  (<xref target="PUT"/>)
3923</t>
3924<t>
3925  Take over definition of CONNECT method from <xref target="RFC2817"/>.
3926  (<xref target="CONNECT"/>)
3927</t>
3928<t>
3929  Broadened the definition of 203 (Non-Authoritative Information) to include
3930  cases of payload transformations as well.
3931  (<xref target="status.203"/>)
3932</t>
3933<t>
3934  Failed to consider that there are many other request methods that are safe
3935  to automatically redirect, and further that the user agent is able to make
3936  that determination based on the request method semantics.
3937  Furthermore, allow user agents to rewrite the method from POST to GET
3938  for status codes 301 and 302.
3939  (Sections <xref format="counter" target="status.301"/>,
3940  <xref format="counter" target="status.302"/> and
3941  <xref format="counter" target="status.307"/>)
3942</t>
3943<t>
3944  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3945  It used to indicate that the target resource must be accessed through the
3946  proxy given by the Location field. The Location field gave the URI of the
3947  proxy. The recipient was expected to repeat this single request via the proxy.
3948  (<xref target="status.305"/>)
3949</t>
3950<t>
3951  Define status 426 (Upgrade Required) (this was incorporated from
3952  <xref target="RFC2817"/>).
3953  (<xref target="status.426"/>)
3954</t>
3955<t>
3956  Change ABNF productions for header fields to only define the field value.
3957  (<xref target="header.field.definitions"/>)
3958</t>
3959<t>
3960  Reclassify "Allow" as response header field, removing the option to
3961  specify it in a PUT request.
3962  Relax the server requirement on the contents of the Allow header field and
3963  remove requirement on clients to always trust the header field value.
3964  (<xref target="header.allow"/>)
3965</t>
3966<t>
3967  Correct syntax of Location header field to allow URI references (including
3968  relative references and fragments), as referred symbol "absoluteURI" wasn't
3969  what was expected, and add some clarifications as to when use of fragments
3970  would not be appropriate.
3971  (<xref target="header.location"/>)
3972</t>
3973<t>
3974  Restrict Max-Forwards header field to OPTIONS and TRACE (previously,
3975  extension methods could have used it as well).
3976  (<xref target="header.max-forwards"/>)
3977</t>
3978<t>
3979  Allow Referer field value of "about:blank" as alternative to not specifying it.
3980  (<xref target="header.referer"/>)
3981</t>
3982<t>
3983  In the description of the Server header field, the Via field
3984  was described as a SHOULD. The requirement was and is stated
3985  correctly in the description of the Via header field in &header-via;.
3986  (<xref target="header.server"/>)
3987</t>
3988</section>
3989
3990<?BEGININC p2-semantics.abnf-appendix ?>
3991<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3992<figure>
3993<artwork type="abnf" name="p2-semantics.parsed-abnf">
3994<x:ref>Allow</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3995
3996<x:ref>Date</x:ref> = HTTP-date
3997
3998<x:ref>Expect</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3999
4000<x:ref>From</x:ref> = mailbox
4001
4002<x:ref>GMT</x:ref> = %x47.4D.54 ; GMT
4003
4004<x:ref>HTTP-date</x:ref> = rfc1123-date / obs-date
4005
4006<x:ref>Location</x:ref> = URI-reference
4007
4008<x:ref>Max-Forwards</x:ref> = 1*DIGIT
4009<x:ref>Method</x:ref> = token
4010
4011<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
4012
4013<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
4014<x:ref>Reason-Phrase</x:ref> = *( HTAB / SP / VCHAR / obs-text )
4015<x:ref>Referer</x:ref> = absolute-URI / partial-URI
4016<x:ref>Retry-After</x:ref> = HTTP-date / delta-seconds
4017
4018<x:ref>Server</x:ref> = product *( RWS ( product / comment ) )
4019<x:ref>Status-Code</x:ref> = 3DIGIT
4020
4021<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.7&gt;
4022<x:ref>User-Agent</x:ref> = product *( RWS ( product / comment ) )
4023
4024<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.7&gt;
4025<x:ref>asctime-date</x:ref> = day-name SP date3 SP time-of-day SP year
4026
4027<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2&gt;
4028
4029<x:ref>date1</x:ref> = day SP month SP year
4030<x:ref>date2</x:ref> = day "-" month "-" 2DIGIT
4031<x:ref>date3</x:ref> = month SP ( 2DIGIT / ( SP DIGIT ) )
4032<x:ref>day</x:ref> = 2DIGIT
4033<x:ref>day-name</x:ref> = %x4D.6F.6E ; Mon
4034 / %x54.75.65 ; Tue
4035 / %x57.65.64 ; Wed
4036 / %x54.68.75 ; Thu
4037 / %x46.72.69 ; Fri
4038 / %x53.61.74 ; Sat
4039 / %x53.75.6E ; Sun
4040<x:ref>day-name-l</x:ref> = %x4D.6F.6E.64.61.79 ; Monday
4041 / %x54.75.65.73.64.61.79 ; Tuesday
4042 / %x57.65.64.6E.65.73.64.61.79 ; Wednesday
4043 / %x54.68.75.72.73.64.61.79 ; Thursday
4044 / %x46.72.69.64.61.79 ; Friday
4045 / %x53.61.74.75.72.64.61.79 ; Saturday
4046 / %x53.75.6E.64.61.79 ; Sunday
4047<x:ref>delta-seconds</x:ref> = 1*DIGIT
4048
4049<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
4050<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
4051<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
4052 *expect-params ]
4053
4054<x:ref>hour</x:ref> = 2DIGIT
4055
4056<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
4057<x:ref>minute</x:ref> = 2DIGIT
4058<x:ref>month</x:ref> = %x4A.61.6E ; Jan
4059 / %x46.65.62 ; Feb
4060 / %x4D.61.72 ; Mar
4061 / %x41.70.72 ; Apr
4062 / %x4D.61.79 ; May
4063 / %x4A.75.6E ; Jun
4064 / %x4A.75.6C ; Jul
4065 / %x41.75.67 ; Aug
4066 / %x53.65.70 ; Sep
4067 / %x4F.63.74 ; Oct
4068 / %x4E.6F.76 ; Nov
4069 / %x44.65.63 ; Dec
4070
4071<x:ref>obs-date</x:ref> = rfc850-date / asctime-date
4072<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
4073
4074<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.7&gt;
4075<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 5.2&gt;
4076
4077<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 3.2.3&gt;
4078
4079<x:ref>rfc1123-date</x:ref> = day-name "," SP date1 SP time-of-day SP GMT
4080<x:ref>rfc850-date</x:ref> = day-name-l "," SP date2 SP time-of-day SP GMT
4081
4082<x:ref>second</x:ref> = 2DIGIT
4083
4084<x:ref>time-of-day</x:ref> = hour ":" minute ":" second
4085<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 3.2.3&gt;
4086
4087<x:ref>year</x:ref> = 4DIGIT
4088</artwork>
4089</figure>
4090<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
4091; Allow defined but not used
4092; Date defined but not used
4093; Expect defined but not used
4094; From defined but not used
4095; Location defined but not used
4096; Max-Forwards defined but not used
4097; Reason-Phrase defined but not used
4098; Referer defined but not used
4099; Retry-After defined but not used
4100; Server defined but not used
4101; Status-Code defined but not used
4102; User-Agent defined but not used
4103</artwork></figure></section>
4104<?ENDINC p2-semantics.abnf-appendix ?>
4105
4106<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
4107
4108<section title="Since RFC 2616">
4109<t>
4110  Extracted relevant partitions from <xref target="RFC2616"/>.
4111</t>
4112</section>
4113
4114<section title="Since draft-ietf-httpbis-p2-semantics-00">
4115<t>
4116  Closed issues:
4117  <list style="symbols"> 
4118    <t>
4119      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
4120      "Via is a MUST"
4121      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
4122    </t>
4123    <t>
4124      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
4125      "Fragments allowed in Location"
4126      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
4127    </t>
4128    <t>
4129      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
4130      "Safe Methods vs Redirection"
4131      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
4132    </t>
4133    <t>
4134      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
4135      "Revise description of the POST method"
4136      (<eref target="http://purl.org/NET/http-errata#post"/>)
4137    </t>
4138    <t>
4139      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
4140      "Normative and Informative references"
4141    </t>
4142    <t>
4143      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
4144      "RFC2606 Compliance"
4145    </t>
4146    <t>
4147      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
4148      "Informative references"
4149    </t>
4150    <t>
4151      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
4152      "Redundant cross-references"
4153    </t>
4154  </list>
4155</t>
4156<t>
4157  Other changes:
4158  <list style="symbols"> 
4159    <t>
4160      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
4161    </t>
4162  </list>
4163</t>
4164</section>
4165
4166<section title="Since draft-ietf-httpbis-p2-semantics-01">
4167<t>
4168  Closed issues:
4169  <list style="symbols"> 
4170    <t>
4171      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
4172      "PUT side effects"
4173    </t>
4174    <t>
4175      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
4176      "Duplicate Host header requirements"
4177    </t>
4178  </list>
4179</t>
4180<t>
4181  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4182  <list style="symbols"> 
4183    <t>
4184      Move "Product Tokens" section (back) into Part 1, as "token" is used
4185      in the definition of the Upgrade header field.
4186    </t>
4187    <t>
4188      Add explicit references to BNF syntax and rules imported from other parts of the specification.
4189    </t>
4190    <t>
4191      Copy definition of delta-seconds from Part6 instead of referencing it.
4192    </t>
4193  </list>
4194</t>
4195</section>
4196
4197<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
4198<t>
4199  Closed issues:
4200  <list style="symbols"> 
4201    <t>
4202      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
4203      "Requiring Allow in 405 responses"
4204    </t>
4205    <t>
4206      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
4207      "Status Code Registry"
4208    </t>
4209    <t>
4210      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
4211      "Redirection vs. Location"
4212    </t>
4213    <t>
4214      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
4215      "Cacheability of 303 response"
4216    </t>
4217    <t>
4218      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
4219      "305 Use Proxy"
4220    </t>
4221    <t>
4222      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
4223      "Classification for Allow header"
4224    </t>
4225    <t>
4226      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
4227      "PUT - 'store under' vs 'store at'"
4228    </t>
4229  </list>
4230</t>
4231<t>
4232  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
4233  <list style="symbols"> 
4234    <t>
4235      Reference RFC 3984, and update header field registrations for headers defined
4236      in this document.
4237    </t>
4238  </list>
4239</t>
4240<t>
4241  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4242  <list style="symbols"> 
4243    <t>
4244      Replace string literals when the string really is case-sensitive (method).
4245    </t>
4246  </list>
4247</t>
4248</section>
4249
4250<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
4251<t>
4252  Closed issues:
4253  <list style="symbols"> 
4254    <t>
4255      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
4256      "OPTIONS request bodies"
4257    </t>
4258    <t>
4259      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
4260      "Description of CONNECT should refer to RFC2817"
4261    </t>
4262    <t>
4263      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
4264      "Location Content-Location reference request/response mixup"
4265    </t>
4266  </list>
4267</t>
4268<t>
4269  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
4270  <list style="symbols"> 
4271    <t>
4272      Added initial proposal for registration process, plus initial
4273      content (non-HTTP/1.1 methods to be added by a separate specification).
4274    </t>
4275  </list>
4276</t>
4277</section>
4278
4279<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
4280<t>
4281  Closed issues:
4282  <list style="symbols"> 
4283    <t>
4284      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
4285      "Content-*"
4286    </t>
4287    <t>
4288      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
4289      "RFC 2822 is updated by RFC 5322"
4290    </t>
4291  </list>
4292</t>
4293<t>
4294  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4295  <list style="symbols"> 
4296    <t>
4297      Use "/" instead of "|" for alternatives.
4298    </t>
4299    <t>
4300      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
4301      whitespace ("OWS") and required whitespace ("RWS").
4302    </t>
4303    <t>
4304      Rewrite ABNFs to spell out whitespace rules, factor out
4305      header field value format definitions.
4306    </t>
4307  </list>
4308</t>
4309</section>
4310
4311<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
4312<t>
4313  Closed issues:
4314  <list style="symbols"> 
4315    <t>
4316      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
4317      "Reason-Phrase BNF"
4318    </t>
4319  </list>
4320</t>
4321<t>
4322  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4323  <list style="symbols"> 
4324    <t>
4325      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
4326    </t>
4327  </list>
4328</t>
4329</section>
4330
4331<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
4332<t>
4333  Closed issues:
4334  <list style="symbols"> 
4335    <t>
4336      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
4337      "Clarify when Referer is sent"
4338    </t>
4339    <t>
4340      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
4341      "status codes vs methods"
4342    </t>
4343    <t>
4344      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
4345      "Do not require "updates" relation for specs that register status codes or method names"
4346    </t>
4347  </list>
4348</t>
4349</section>
4350
4351<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
4352<t>
4353  Closed issues:
4354  <list style="symbols"> 
4355    <t>
4356      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
4357      "Idempotency"
4358    </t>
4359    <t>
4360      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
4361      "TRACE security considerations"
4362    </t>
4363    <t>
4364      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
4365      "Clarify rules for determining what entities a response carries"
4366    </t>
4367    <t>
4368      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
4369      "update note citing RFC 1945 and 2068"
4370    </t>
4371    <t>
4372      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
4373      "update note about redirect limit"
4374    </t>
4375    <t>
4376      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
4377      "Location header ABNF should use 'URI'"
4378    </t>
4379    <t>
4380      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
4381      "fragments in Location vs status 303"
4382    </t>
4383    <t>
4384      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
4385      "move IANA registrations for optional status codes"
4386    </t>
4387  </list>
4388</t>
4389<t>
4390  Partly resolved issues:
4391  <list style="symbols"> 
4392    <t>
4393      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
4394      "Are OPTIONS and TRACE safe?"
4395    </t>
4396  </list>
4397</t>
4398</section>
4399
4400<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
4401<t>
4402  Closed issues:
4403  <list style="symbols"> 
4404    <t>
4405      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
4406      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
4407      status codes when fixing this previously)
4408    </t>
4409  </list>
4410</t>
4411</section>
4412
4413<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
4414<t>
4415  Closed issues:
4416  <list style="symbols"> 
4417    <t>
4418      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4419      "Fragment combination / precedence during redirects"
4420    </t>
4421  </list>
4422</t>
4423<t>
4424  Partly resolved issues:
4425  <list style="symbols"> 
4426    <t>
4427      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
4428      "Location header payload handling"
4429    </t>
4430    <t>
4431      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
4432      "Term for the requested resource's URI"
4433    </t>
4434  </list>
4435</t>
4436</section>
4437
4438<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
4439<t>
4440  Closed issues:
4441  <list style="symbols"> 
4442    <t>
4443      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
4444      "Clarify 'Requested Variant'"
4445    </t>
4446    <t>
4447      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
4448      "Clarify entity / representation / variant terminology"
4449    </t>
4450    <t>
4451      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/139"/>:
4452      "Methods and Caching"
4453    </t>
4454    <t>
4455      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/190"/>:
4456      "OPTIONS vs Max-Forwards"
4457    </t>
4458    <t>
4459      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/199"/>:
4460      "Status codes and caching"
4461    </t>
4462    <t>
4463      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
4464      "consider removing the 'changes from 2068' sections"
4465    </t>
4466  </list>
4467</t>
4468</section>
4469
4470<section title="Since draft-ietf-httpbis-p2-semantics-11" anchor="changes.since.11">
4471<t>
4472  Closed issues:
4473  <list style="symbols"> 
4474    <t>
4475      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/229"/>:
4476      "Considerations for new status codes"
4477    </t>
4478    <t>
4479      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/230"/>:
4480      "Considerations for new methods"
4481    </t>
4482    <t>
4483      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/232"/>:
4484      "User-Agent guidelines" (relating to the 'User-Agent' header field)
4485    </t>
4486  </list>
4487</t>
4488</section>
4489
4490<section title="Since draft-ietf-httpbis-p2-semantics-12" anchor="changes.since.12">
4491<t>
4492  Closed issues:
4493  <list style="symbols"> 
4494    <t>
4495      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4496      "Fragment combination / precedence during redirects" (added warning
4497      about having a fragid on the redirect may cause inconvenience in
4498      some cases)
4499    </t>
4500    <t>
4501      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/79"/>:
4502      "Content-* vs. PUT"
4503    </t>
4504    <t>
4505      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/88"/>:
4506      "205 Bodies"
4507    </t>
4508    <t>
4509      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/102"/>:
4510      "Understanding Content-* on non-PUT requests"
4511    </t>
4512    <t>
4513      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
4514      "Content-*"
4515    </t>
4516    <t>
4517      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/104"/>:
4518      "Header type defaulting"
4519    </t>
4520    <t>
4521      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
4522      "PUT - 'store under' vs 'store at'"
4523    </t>
4524    <t>
4525      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/137"/>:
4526      "duplicate ABNF for Reason-Phrase"
4527    </t>
4528    <t>
4529      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/180"/>:
4530      "Note special status of Content-* prefix in header registration procedures"
4531    </t>
4532    <t>
4533      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/203"/>:
4534      "Max-Forwards vs extension methods"
4535    </t>
4536    <t>
4537      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/213"/>:
4538      "What is the value space of HTTP status codes?" (actually fixed in
4539      draft-ietf-httpbis-p2-semantics-11)
4540    </t>
4541    <t>
4542      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/224"/>:
4543      "Header Classification"
4544    </t>
4545    <t>
4546      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/225"/>:
4547      "PUT side effect: invalidation or just stale?"
4548    </t>
4549    <t>
4550      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/226"/>:
4551      "proxies not supporting certain methods"
4552    </t>
4553    <t>
4554      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/239"/>:
4555      "Migrate CONNECT from RFC2817 to p2"
4556    </t>
4557    <t>
4558      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/240"/>:
4559      "Migrate Upgrade details from RFC2817"
4560    </t>
4561    <t>
4562      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/267"/>:
4563      "clarify PUT semantics'"
4564    </t>
4565    <t>
4566      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/275"/>:
4567      "duplicate ABNF for 'Method'"
4568    </t>
4569    <t>
4570      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4571      "untangle ABNFs for header fields"
4572    </t>
4573  </list>
4574</t>
4575</section>
4576
4577<section title="Since draft-ietf-httpbis-p2-semantics-13" anchor="changes.since.13">
4578<t>
4579  Closed issues:
4580  <list style="symbols"> 
4581    <t>
4582      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4583      "untangle ABNFs for header fields"
4584    </t>
4585    <t>
4586      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/251"/>:
4587      "message-body in CONNECT request"
4588    </t>
4589  </list>
4590</t>
4591</section>
4592
4593<section title="Since draft-ietf-httpbis-p2-semantics-14" anchor="changes.since.14">
4594<t>
4595  Closed issues:
4596  <list style="symbols"> 
4597    <t>
4598      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/255"/>:
4599      "Clarify status code for rate limiting"
4600    </t>
4601    <t>
4602      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/294"/>:
4603      "clarify 403 forbidden"
4604    </t>
4605    <t>
4606      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/296"/>:
4607      "Clarify 203 Non-Authoritative Information"
4608    </t>
4609    <t>
4610      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/298"/>:
4611      "update default reason phrase for 413"
4612    </t>
4613  </list>
4614</t>
4615</section>
4616
4617<section title="Since draft-ietf-httpbis-p2-semantics-15" anchor="changes.since.15">
4618<t>
4619  Closed issues:
4620  <list style="symbols"> 
4621    <t>
4622      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/285"/>:
4623      "Strength of requirements on Accept re: 406"
4624    </t>
4625    <t>
4626      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/303"/>:
4627      "400 response isn't generic"
4628    </t>
4629  </list>
4630</t>
4631</section>
4632
4633<section title="Since draft-ietf-httpbis-p2-semantics-16" anchor="changes.since.16">
4634<t>
4635  Closed issues:
4636  <list style="symbols"> 
4637    <t>
4638      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/160"/>:
4639      "Redirects and non-GET methods"
4640    </t>
4641    <t>
4642      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/310"/>:
4643      "clarify 303 redirect on HEAD"
4644    </t>
4645  </list>
4646</t>
4647<t>
4648  Work-in-progress:
4649  <list style="symbols"> 
4650    <t>
4651      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/231"/>:
4652      "Considerations for new headers"
4653    </t>
4654  </list>
4655</t>
4656</section>
4657
4658</section>
4659
4660</back>
4661</rfc>
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