source: draft-ietf-httpbis/latest/p2-semantics.xml @ 1451

Last change on this file since 1451 was 1451, checked in by julian.reschke@…, 8 years ago

param names are case-insensitive (see #231)

  • Property svn:eol-style set to native
File size: 191.6 KB
Line 
1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD NOT</bcp14>">
14  <!ENTITY ID-VERSION "latest">
15  <!ENTITY ID-MONTH "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 (case-insensitively) named
527   parameters (for instance, Content-Type, defined in &header-content-type;).
528   Allowing both unquoted (token) and quoted (quoted-string) syntax for the
529   parameter value enables recipients to use existing parser components. Also,
530   the meaning of a value ought to be independent of the syntax variant used
531   for it (for an example, see the notes on parameter handling for media types
532   in &media-types;).
533</t>
534<t>
535   Authors of specifications defining new header fields are advised to consider
536   documenting:
537  <list style="symbols">
538    <x:lt>
539      <t>Whether the field is a single value, or whether it can be a list
540      (delimited by commas; see &header-fields;).</t>
541      <t>If it does not use the list syntax, how to treat messages where the
542      header field occurs multiple times (a sensible default would be to ignore
543      the header field, but this might not always be the right choice).</t>
544    </x:lt>
545    <x:lt><t>Under what conditions the header field can be used; e.g., only in
546    responses or requests, in all messages, only on responses to a particular
547    request method.</t></x:lt>
548    <x:lt><t>Whether it is appropriate to list the field-name in the Connection header
549    (i.e., if the header is to be hop-by-hop, see &header-connection;).</t></x:lt>
550    <x:lt><t>Under what conditions intermediaries are allowed to modify the header
551    field's value, insert or delete it.</t></x:lt>
552    <x:lt><t>How the header might interact with caching (see <xref target="Part6"/>).</t></x:lt>
553    <x:lt><t>Whether the header field is useful or allowable in trailers (see
554    &chunked-encoding;).</t></x:lt>
555    <x:lt><t>Whether the header field should be preserved across redirects.</t></x:lt>
556  </list>
557</t>
558</section>
559
560<section title="Request Header Fields" anchor="request.header.fields">
561  <x:anchor-alias value="request-header"/>
562<t>
563   The request header fields allow the client to pass additional
564   information about the request, and about the client itself, to the
565   server. These fields act as request modifiers, with semantics
566   equivalent to the parameters on a programming language method
567   invocation.
568</t>
569<texttable align="left">
570  <ttcol>Header Field Name</ttcol>
571  <ttcol>Defined in...</ttcol>
572
573  <c>Accept</c> <c>&header-accept;</c>
574  <c>Accept-Charset</c> <c>&header-accept-charset;</c>
575  <c>Accept-Encoding</c> <c>&header-accept-encoding;</c>
576  <c>Accept-Language</c> <c>&header-accept-language;</c>
577  <c>Authorization</c> <c>&header-authorization;</c>
578  <c>Expect</c> <c><xref target="header.expect"/></c>
579  <c>From</c> <c><xref target="header.from"/></c>
580  <c>Host</c> <c>&header-host;</c>
581  <c>If-Match</c> <c>&header-if-match;</c>
582  <c>If-Modified-Since</c> <c>&header-if-modified-since;</c>
583  <c>If-None-Match</c> <c>&header-if-none-match;</c>
584  <c>If-Range</c> <c>&header-if-range;</c>
585  <c>If-Unmodified-Since</c> <c>&header-if-unmodified-since;</c>
586  <c>Max-Forwards</c> <c><xref target="header.max-forwards"/></c>
587  <c>Proxy-Authorization</c> <c>&header-proxy-authorization;</c>
588  <c>Range</c> <c>&header-range;</c>
589  <c>Referer</c> <c><xref target="header.referer"/></c>
590  <c>TE</c> <c>&header-te;</c>
591  <c>User-Agent</c> <c><xref target="header.user-agent"/></c>
592</texttable>
593</section>
594
595<section title="Response Header Fields" anchor="response.header.fields">
596  <x:anchor-alias value="response-header"/>
597<t>
598   The response header fields allow the server to pass additional
599   information about the response which cannot be placed in the Status-Line.
600   These header fields give information about the server and about
601   further access to the target resource (&effective-request-uri;).
602</t>
603<texttable align="left">
604  <ttcol>Header Field Name</ttcol><ttcol>Defined in...</ttcol>
605
606  <c>Accept-Ranges</c> <c>&header-accept-ranges;</c>
607  <c>Age</c> <c>&header-age;</c>
608  <c>Allow</c> <c><xref target="header.allow"/></c>
609  <c>Date</c> <c><xref target="header.date"/></c>
610  <c>ETag</c> <c>&header-etag;</c>
611  <c>Location</c> <c><xref target="header.location"/></c>
612  <c>Proxy-Authenticate</c> <c>&header-proxy-authenticate;</c>
613  <c>Retry-After</c> <c><xref target="header.retry-after"/></c>
614  <c>Server</c> <c><xref target="header.server"/></c>
615  <c>Vary</c> <c>&header-vary;</c>
616  <c>WWW-Authenticate</c> <c>&header-www-authenticate;</c>
617</texttable>
618</section>
619
620</section>
621
622<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
623  <x:anchor-alias value="Reason-Phrase"/>
624  <x:anchor-alias value="Status-Code"/>
625  <x:anchor-alias value="extension-code"/>
626<t>
627   The Status-Code element is a 3-digit integer result code of the attempt to
628   understand and satisfy the request.
629</t>
630<t>
631   The Reason-Phrase is intended to give a short textual description of the
632   Status-Code and is intended for a human user. The client does not need
633   to examine or display the Reason-Phrase.
634</t>
635<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"/>
636  <x:ref>Status-Code</x:ref>    = 3<x:ref>DIGIT</x:ref>
637  <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> )
638</artwork></figure>
639<t>
640   HTTP status codes are extensible. HTTP applications are not required
641   to understand the meaning of all registered status codes, though such
642   understanding is obviously desirable. However, applications &MUST;
643   understand the class of any status code, as indicated by the first
644   digit, and treat any unrecognized response as being equivalent to the
645   x00 status code of that class, with the exception that an
646   unrecognized response &MUST-NOT; be cached. For example, if an
647   unrecognized status code of 431 is received by the client, it can
648   safely assume that there was something wrong with its request and
649   treat the response as if it had received a 400 status code. In such
650   cases, user agents &SHOULD; present to the user the representation enclosed
651   with the response, since that representation is likely to include human-readable
652   information which will explain the unusual status.
653</t>
654
655<section title="Overview of Status Codes" anchor="overview.of.status.codes">
656<t> 
657   The status codes listed below are defined in <xref target="status.codes"/>
658   of this specification, &p4-status-codes;, &p5-status-codes;, and &p7-status-codes;.
659   The reason phrases listed here are only recommendations &mdash; they can be
660   replaced by local equivalents without affecting the protocol.
661</t>
662<texttable align="left">
663  <ttcol>Status-Code</ttcol>
664  <ttcol>Reason-Phrase</ttcol>
665  <ttcol>Defined in...</ttcol>
666 
667  <c>100</c> <c>Continue</c> <c><xref target="status.100"/></c>
668  <c>101</c> <c>Switching Protocols</c> <c><xref target="status.101"/></c>
669
670  <c>200</c> <c>OK</c> <c><xref target="status.200"/></c>
671  <c>201</c> <c>Created</c> <c><xref target="status.201"/></c>
672  <c>202</c> <c>Accepted</c> <c><xref target="status.202"/></c>
673  <c>203</c> <c>Non-Authoritative Information</c> <c><xref target="status.203"/></c>
674  <c>204</c> <c>No Content</c> <c><xref target="status.204"/></c>
675  <c>205</c> <c>Reset Content</c> <c><xref target="status.205"/></c>
676  <c>206</c> <c>Partial Content</c> <c>&status-206;</c>
677
678  <c>300</c> <c>Multiple Choices</c> <c><xref target="status.300"/></c>
679  <c>301</c> <c>Moved Permanently</c> <c><xref target="status.301"/></c>
680  <c>302</c> <c>Found</c> <c><xref target="status.302"/></c>
681  <c>303</c> <c>See Other</c> <c><xref target="status.303"/></c>
682  <c>304</c> <c>Not Modified</c> <c>&status-304;</c>
683  <c>305</c> <c>Use Proxy</c> <c><xref target="status.305"/></c>
684  <c>307</c> <c>Temporary Redirect</c> <c><xref target="status.307"/></c>
685
686  <c>400</c> <c>Bad Request</c> <c><xref target="status.400"/></c>
687  <c>401</c> <c>Unauthorized</c> <c>&status-401;</c>
688  <c>402</c> <c>Payment Required</c> <c><xref target="status.402"/></c>
689  <c>403</c> <c>Forbidden</c> <c><xref target="status.403"/></c>
690  <c>404</c> <c>Not Found</c> <c><xref target="status.404"/></c>
691  <c>405</c> <c>Method Not Allowed</c> <c><xref target="status.405"/></c>
692  <c>406</c> <c>Not Acceptable</c> <c><xref target="status.406"/></c>
693  <c>407</c> <c>Proxy Authentication Required</c> <c>&status-407;</c>
694  <c>408</c> <c>Request Time-out</c> <c><xref target="status.408"/></c>
695  <c>409</c> <c>Conflict</c> <c><xref target="status.409"/></c>
696  <c>410</c> <c>Gone</c> <c><xref target="status.410"/></c>
697  <c>411</c> <c>Length Required</c> <c><xref target="status.411"/></c>
698  <c>412</c> <c>Precondition Failed</c> <c>&status-412;</c>
699  <c>413</c> <c>Request Representation Too Large</c> <c><xref target="status.413"/></c>
700  <c>414</c> <c>URI Too Long</c> <c><xref target="status.414"/></c>
701  <c>415</c> <c>Unsupported Media Type</c> <c><xref target="status.415"/></c>
702  <c>416</c> <c>Requested range not satisfiable</c> <c>&status-416;</c>
703  <c>417</c> <c>Expectation Failed</c> <c><xref target="status.417"/></c>
704  <c>426</c> <c>Upgrade Required</c> <c><xref target="status.426"/></c>
705
706  <c>500</c> <c>Internal Server Error</c> <c><xref target="status.500"/></c>
707  <c>501</c> <c>Not Implemented</c> <c><xref target="status.501"/></c>
708  <c>502</c> <c>Bad Gateway</c> <c><xref target="status.502"/></c>
709  <c>503</c> <c>Service Unavailable</c> <c><xref target="status.503"/></c>
710  <c>504</c> <c>Gateway Time-out</c> <c><xref target="status.504"/></c>
711  <c>505</c> <c>HTTP Version not supported</c> <c><xref target="status.505"/></c>
712</texttable>
713<t>
714   Note that this list is not exhaustive &mdash; it does not include
715   extension status codes defined in other specifications.
716</t>
717</section>
718
719<section title="Status Code Registry" anchor="status.code.registry">
720<t>
721  The HTTP Status Code Registry defines the name space for the Status-Code
722  token in the Status-Line of an HTTP response.
723</t>
724<t>
725  Values to be added to this name space are subject to IETF review
726  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
727</t>
728<t>
729  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
730</t>
731
732<section title="Considerations for New Status Codes" anchor="considerations.for.new.status.codes">
733<t>
734   When it is necessary to express new semantics for a HTTP response that
735   aren't specific to a single application or media type, and currently defined
736   status codes are inadequate, a new status code can be registered.
737</t>
738<t>
739   HTTP status codes are generic; that is, they are potentially applicable to
740   any resource, not just one particular media type, "type" of resource, or
741   application. As such, it is preferred that new HTTP status codes be
742   registered in a document that isn't specific to a single application, so
743   that this is clear.
744</t>
745<t>
746   Definitions of new HTTP status codes typically explain the request
747   conditions that produce a response containing the status code (e.g.,
748   combinations of request headers and/or method(s)), along with any
749   interactions with response headers (e.g., those that are required, those
750   that modify the semantics of the response).
751</t>
752<t>
753   New HTTP status codes are required to fall under one of the categories
754   defined in <xref target="status.codes"/>. To allow existing parsers to
755   properly handle them, new status codes cannot disallow a response body,
756   although they can mandate a zero-length response body. They can require the
757   presence of one or more particular HTTP response header(s).
758</t>
759<t>
760   Likewise, their definitions can specify that caches are allowed to use
761   heuristics to determine their freshness (see &caching;; by default, it is
762   not allowed), and can define how to determine the resource which they
763   carry a representation for (see <xref
764   target="identifying.response.associated.with.representation"/>; by default,
765   it is anonymous).
766</t>
767</section>
768
769</section>
770
771</section>
772
773<section title="Representation" anchor="representation">
774<t>
775   Request and Response messages &MAY; transfer a representation if not otherwise
776   restricted by the request method or response status code. A representation
777   consists of metadata (representation header fields) and data (representation
778   body).  When a complete or partial representation is enclosed in an HTTP message,
779   it is referred to as the payload of the message. HTTP representations
780   are defined in &payload;.
781</t>
782<t>
783   A representation body is only present in a message when a message-body is
784   present, as described in &message-body;. The representation body is obtained
785   from the message-body by decoding any Transfer-Encoding that might
786   have been applied to ensure safe and proper transfer of the message.
787</t>
788
789<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
790<t>
791   It is sometimes necessary to determine an identifier for the resource
792   associated with a representation.
793</t>
794<t>
795   An HTTP request representation, when present, is always associated with an
796   anonymous (i.e., unidentified) resource.
797</t>
798<t>
799   In the common case, an HTTP response is a representation of the target
800   resource (see &effective-request-uri;). However, this is not always the
801   case. To determine the URI of the resource a response is associated with,
802   the following rules are used (with the first applicable one being selected):
803</t>
804<t><list style="numbers">
805   <t>If the response status code is 200 or 203 and the request method was GET,
806   the response payload is a representation of the target resource.</t>
807   <t>If the response status code is 204, 206, or 304 and the request method was GET
808   or HEAD, the response payload is a partial representation of the target
809   resource.</t>
810   <t>If the response has a Content-Location header field, and that URI is the same
811   as the effective request URI, the response payload is a representation of the
812   target resource.</t>
813   <t>If the response has a Content-Location header field, and that URI is not the
814   same as the effective request URI, then the response asserts that its
815   payload is a representation of the resource identified by the
816   Content-Location URI. However, such an assertion cannot be trusted unless
817   it can be verified by other means (not defined by HTTP).</t>
818   <t>Otherwise, the response is a representation of an anonymous (i.e.,
819   unidentified) resource.</t>
820</list></t>
821<t>
822  <cref anchor="TODO-req-uri">
823   The comparison function is going to have to be defined somewhere,
824   because we already need to compare URIs for things like cache invalidation.</cref>
825</t>
826</section>
827
828</section>
829
830
831<section title="Method Definitions" anchor="method.definitions">
832<t>
833   The set of common request methods for HTTP/1.1 is defined below. Although
834   this set can be expanded, additional methods cannot be assumed to
835   share the same semantics for separately extended clients and servers.
836</t>
837
838<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
839
840<section title="Safe Methods" anchor="safe.methods">
841<iref item="Safe Methods" primary="true"/>
842<t>
843   Implementors need to be aware that the software represents the user in
844   their interactions over the Internet, and need to allow
845   the user to be aware of any actions they take which might have an
846   unexpected significance to themselves or others.
847</t>
848<t>
849   In particular, the convention has been established that the GET, HEAD,
850   OPTIONS, and TRACE request methods &SHOULD-NOT; have the significance
851   of taking an action other than retrieval. These request methods ought
852   to be considered "<x:dfn anchor="safe">safe</x:dfn>".
853   This allows user agents to represent other methods, such as POST, PUT
854   and DELETE, in a special way, so that the user is made aware of the
855   fact that a possibly unsafe action is being requested.
856</t>
857<t>
858   Naturally, it is not possible to ensure that the server does not
859   generate side-effects as a result of performing a GET request; in
860   fact, some dynamic resources consider that a feature. The important
861   distinction here is that the user did not request the side-effects,
862   so therefore cannot be held accountable for them.
863</t>
864</section>
865
866<section title="Idempotent Methods" anchor="idempotent.methods">
867<iref item="Idempotent Methods" primary="true"/>
868<t>
869   Request methods can also have the property of "idempotence" in that,
870   aside from error or expiration issues, the intended effect of multiple
871   identical requests is the same as for a single request.
872   PUT, DELETE, and all safe request methods are idempotent.
873   It is important to note that idempotence refers only to changes
874   requested by the client: a server is free to change its state due
875   to multiple requests for the purpose of tracking those requests,
876   versioning of results, etc.
877</t>
878</section>
879</section>
880
881<section title="OPTIONS" anchor="OPTIONS">
882  <rdf:Description>
883    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
884  </rdf:Description>
885  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
886  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
887<t>
888   The OPTIONS method requests information about the
889   communication options available on the request/response chain
890   identified by the effective request URI. This method allows a client to
891   determine the options and/or requirements associated with a resource,
892   or the capabilities of a server, without implying a resource action
893   or initiating a resource retrieval.
894</t>
895<t>
896   Responses to the OPTIONS method are not cacheable.
897</t>
898<t>
899   If the OPTIONS request includes a message-body (as indicated by the
900   presence of Content-Length or Transfer-Encoding), then the media type
901   &MUST; be indicated by a Content-Type field. Although this
902   specification does not define any use for such a body, future
903   extensions to HTTP might use the OPTIONS body to make more detailed
904   queries on the server.
905</t>
906<t>
907   If the request-target is an asterisk ("*"), the OPTIONS request is
908   intended to apply to the server in general rather than to a specific
909   resource. Since a server's communication options typically depend on
910   the resource, the "*" request is only useful as a "ping" or "no-op"
911   type of method; it does nothing beyond allowing the client to test
912   the capabilities of the server. For example, this can be used to test
913   a proxy for HTTP/1.1 compliance (or lack thereof).
914</t>
915<t>
916   If the request-target is not an asterisk, the OPTIONS request applies
917   only to the options that are available when communicating with that
918   resource.
919</t>
920<t>
921   A 200 response &SHOULD; include any header fields that indicate
922   optional features implemented by the server and applicable to that
923   resource (e.g., Allow), possibly including extensions not defined by
924   this specification. The response body, if any, &SHOULD; also include
925   information about the communication options. The format for such a
926   body is not defined by this specification, but might be defined by
927   future extensions to HTTP. Content negotiation &MAY; be used to select
928   the appropriate response format. If no response body is included, the
929   response &MUST; include a Content-Length field with a field-value of
930   "0".
931</t>
932<t>
933   The Max-Forwards header field &MAY; be used to target a
934   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
935   If no Max-Forwards field is present in the request, then the forwarded
936   request &MUST-NOT; include a Max-Forwards field.
937</t>
938</section>
939
940<section title="GET" anchor="GET">
941  <rdf:Description>
942    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
943  </rdf:Description>
944  <iref primary="true" item="GET method" x:for-anchor=""/>
945  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
946<t>
947   The GET method requests transfer of a current representation of
948   the target resource.
949</t>
950<t>   
951   If the target resource is a data-producing process, it is the
952   produced data which shall be returned as the representation in the response and not
953   the source text of the process, unless that text happens to be the output of
954   the process.
955</t>
956<t>
957   The semantics of the GET method change to a "conditional GET" if the
958   request message includes an If-Modified-Since, If-Unmodified-Since,
959   If-Match, If-None-Match, or If-Range header field. A conditional GET
960   requests that the representation be transferred only under the
961   circumstances described by the conditional header field(s). The
962   conditional GET request is intended to reduce unnecessary network
963   usage by allowing cached representations to be refreshed without requiring
964   multiple requests or transferring data already held by the client.
965</t>
966<t>
967   The semantics of the GET method change to a "partial GET" if the
968   request message includes a Range header field. A partial GET requests
969   that only part of the representation be transferred, as described in &header-range;.
970   The partial GET request is intended to reduce unnecessary
971   network usage by allowing partially-retrieved representations to be
972   completed without transferring data already held by the client.
973</t>
974<t>
975   Bodies on GET requests have no defined semantics. Note that sending a body
976   on a GET request might cause some existing implementations to reject the
977   request.
978</t>
979<t>
980   The response to a GET request is cacheable and &MAY; be used to satisfy
981   subsequent GET and HEAD requests (see &caching;).
982</t>
983<t>
984   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
985</t>
986</section>
987
988<section title="HEAD" anchor="HEAD">
989  <rdf:Description>
990    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
991  </rdf:Description>
992  <iref primary="true" item="HEAD method" x:for-anchor=""/>
993  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
994<t>
995   The HEAD method is identical to GET except that the server &MUST-NOT;
996   return a message-body in the response. The metadata contained
997   in the HTTP header fields in response to a HEAD request &SHOULD; be identical
998   to the information sent in response to a GET request. This method can
999   be used for obtaining metadata about the representation implied by the
1000   request without transferring the representation body. This method is
1001   often used for testing hypertext links for validity, accessibility,
1002   and recent modification.
1003</t>
1004<t>
1005   The response to a HEAD request is cacheable and &MAY; be used to satisfy
1006   a subsequent HEAD request; see &caching;. It also &MAY; be used to update a previously cached
1007   representation from that resource; if the new field values
1008   indicate that the cached representation differs from the current representation (as
1009   would be indicated by a change in Content-Length, ETag
1010   or Last-Modified), then the cache &MUST; treat the cache entry as
1011   stale.
1012</t>
1013<t>
1014   Bodies on HEAD requests have no defined semantics. Note that sending a body
1015   on a HEAD request might cause some existing implementations to reject the
1016   request.
1017</t>
1018</section>
1019
1020<section title="POST" anchor="POST">
1021  <iref primary="true" item="POST method" x:for-anchor=""/>
1022  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
1023<t>
1024   The POST method requests that the origin server accept the
1025   representation enclosed in the request as data to be processed by the
1026   target resource. POST is designed to allow a uniform method to cover the
1027   following functions:
1028  <list style="symbols">
1029    <t>
1030      Annotation of existing resources;
1031    </t>
1032    <t>
1033        Posting a message to a bulletin board, newsgroup, mailing list,
1034        or similar group of articles;
1035    </t>
1036    <t>
1037        Providing a block of data, such as the result of submitting a
1038        form, to a data-handling process;
1039    </t>
1040    <t>
1041        Extending a database through an append operation.
1042    </t>
1043  </list>
1044</t>
1045<t>
1046   The actual function performed by the POST method is determined by the
1047   server and is usually dependent on the effective request URI.
1048</t>
1049<t>
1050   The action performed by the POST method might not result in a
1051   resource that can be identified by a URI. In this case, either 200
1052   (OK) or 204 (No Content) is the appropriate response status code,
1053   depending on whether or not the response includes a representation that
1054   describes the result.
1055</t>
1056<t>
1057   If a resource has been created on the origin server, the response
1058   &SHOULD; be 201 (Created) and contain a representation which describes the
1059   status of the request and refers to the new resource, and a Location
1060   header field (see <xref target="header.location"/>).
1061</t>
1062<t>
1063   Responses to POST requests are only cacheable when they
1064   include explicit freshness information (see &p6-explicit;). A
1065   cached POST response with a Content-Location header field
1066   (see &header-content-location;) whose value is the effective
1067   Request URI &MAY; be used to satisfy subsequent GET and HEAD requests.
1068</t>
1069<t>
1070   Note that POST caching is not widely implemented.
1071   However, the 303 (See Other) response can be used to direct the
1072   user agent to retrieve a cacheable resource.
1073</t>
1074</section>
1075
1076<section title="PUT" anchor="PUT">
1077  <iref primary="true" item="PUT method" x:for-anchor=""/>
1078  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
1079<t>
1080   The PUT method requests that the state of the target resource
1081   be created or replaced with the state defined by the representation
1082   enclosed in the request message payload.  A successful PUT of a given
1083   representation would suggest that a subsequent GET on that same target
1084   resource will result in an equivalent representation being returned in
1085   a 200 (OK) response.  However, there is no guarantee that such a state
1086   change will be observable, since the target resource might be acted
1087   upon by other user agents in parallel, or might be subject to dynamic
1088   processing by the origin server, before any subsequent GET is received.
1089   A successful response only implies that the user agent's intent was
1090   achieved at the time of its processing by the origin server.
1091</t>
1092<t>   
1093   If the target resource does not have a current representation and
1094   the PUT successfully creates one, then the origin server &MUST; inform
1095   the user agent by sending a 201 (Created) response.  If the target
1096   resource does have a current representation and that representation is
1097   successfully modified in accordance with the state of the enclosed
1098   representation, then either a 200 (OK) or 204 (No Content) response
1099   &SHOULD; be sent to indicate successful completion of the request.
1100</t>
1101<t>
1102   Unrecognized header fields &SHOULD; be ignored (i.e., not saved
1103   as part of the resource state).
1104</t>
1105<t>
1106   An origin server &SHOULD; verify that the PUT representation is
1107   consistent with any constraints which the server has for the target
1108   resource that cannot or will not be changed by the PUT.  This is
1109   particularly important when the origin server uses internal
1110   configuration information related to the URI in order to set the
1111   values for representation metadata on GET responses.  When a PUT
1112   representation is inconsistent with the target resource, the origin
1113   server &SHOULD; either make them consistent, by transforming the
1114   representation or changing the resource configuration, or respond
1115   with an appropriate error message containing sufficient information
1116   to explain why the representation is unsuitable.  The 409 (Conflict)
1117   or 415 (Unsupported Media Type) status codes are suggested, with the
1118   latter being specific to constraints on Content-Type values.
1119</t>
1120<t>
1121   For example, if the target resource is configured to always have a
1122   Content-Type of "text/html" and the representation being PUT has a
1123   Content-Type of "image/jpeg", then the origin server &SHOULD; do one of:
1124   (a) reconfigure the target resource to reflect the new media type;
1125   (b) transform the PUT representation to a format consistent with that
1126   of the resource before saving it as the new resource state; or,
1127   (c) reject the request with a 415 response indicating that the target
1128   resource is limited to "text/html", perhaps including a link to a
1129   different resource that would be a suitable target for the new
1130   representation.
1131</t>
1132<t>
1133   HTTP does not define exactly how a PUT method affects the state
1134   of an origin server beyond what can be expressed by the intent of
1135   the user agent request and the semantics of the origin server response.
1136   It does not define what a resource might be, in any sense of that
1137   word, beyond the interface provided via HTTP.  It does not define
1138   how resource state is "stored", nor how such storage might change
1139   as a result of a change in resource state, nor how the origin server
1140   translates resource state into representations.  Generally speaking,
1141   all implementation details behind the resource interface are
1142   intentionally hidden by the server.
1143</t>
1144<t>
1145   The fundamental difference between the POST and PUT methods is
1146   highlighted by the different intent for the target resource.
1147   The target resource in a POST request is intended to handle the
1148   enclosed representation as a data-accepting process, such as for
1149   a gateway to some other protocol or a document that accepts annotations.
1150   In contrast, the target resource in a PUT request is intended to
1151   take the enclosed representation as a new or replacement value.
1152   Hence, the intent of PUT is idempotent and visible to intermediaries,
1153   even though the exact effect is only known by the origin server.
1154</t>
1155<t>
1156   Proper interpretation of a PUT request presumes that the user agent
1157   knows what target resource is desired.  A service that is intended
1158   to select a proper URI on behalf of the client, after receiving
1159   a state-changing request, &SHOULD; be implemented using the POST
1160   method rather than PUT.  If the origin server will not make the
1161   requested PUT state change to the target resource and instead
1162   wishes to have it applied to a different resource, such as when the
1163   resource has been moved to a different URI, then the origin server
1164   &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
1165   then make its own decision regarding whether or not to redirect the
1166   request.
1167</t>
1168<t>
1169   A PUT request applied to the target resource &MAY; have side-effects
1170   on other resources.  For example, an article might have a URI for
1171   identifying "the current version" (a resource) which is separate
1172   from the URIs identifying each particular version (different
1173   resources that at one point shared the same state as the current version
1174   resource).  A successful PUT request on "the current version" URI might
1175   therefore create a new version resource in addition to changing the
1176   state of the target resource, and might also cause links to be added
1177   between the related resources.
1178</t>
1179<t>
1180   An origin server &SHOULD; reject any PUT request that contains a
1181   Content-Range header field, since it might be misinterpreted as
1182   partial content (or might be partial content that is being mistakenly
1183   PUT as a full representation).  Partial content updates are
1184   possible by targeting a separately identified resource with state
1185   that overlaps a portion of the larger resource, or by using a
1186   different method that has been specifically defined for partial
1187   updates (for example, the PATCH method defined in
1188   <xref target="RFC5789"/>).
1189</t>
1190<t>
1191   Responses to the PUT method are not cacheable. If a PUT request passes
1192   through a cache that has one or more stored responses for the effective
1193   request URI, those stored responses will be invalidated (see
1194   &p6-invalid;).
1195</t>
1196</section>
1197
1198<section title="DELETE" anchor="DELETE">
1199  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1200  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1201<t>
1202   The DELETE method requests that the origin server delete the target
1203   resource. This method &MAY; be overridden by
1204   human intervention (or other means) on the origin server. The client cannot
1205   be guaranteed that the operation has been carried out, even if the
1206   status code returned from the origin server indicates that the action
1207   has been completed successfully. However, the server &SHOULD-NOT; 
1208   indicate success unless, at the time the response is given, it
1209   intends to delete the resource or move it to an inaccessible
1210   location.
1211</t>
1212<t>
1213   A successful response &SHOULD; be 200 (OK) if the response includes an
1214   representation describing the status, 202 (Accepted) if the action has not
1215   yet been enacted, or 204 (No Content) if the action has been enacted
1216   but the response does not include a representation.
1217</t>
1218<t>
1219   Bodies on DELETE requests have no defined semantics. Note that sending a body
1220   on a DELETE request might cause some existing implementations to reject the
1221   request.
1222</t>
1223<t>
1224   Responses to the DELETE method are not cacheable. If a DELETE request
1225   passes through a cache that has one or more stored responses for the
1226   effective request URI, those stored responses will be invalidated (see
1227   &p6-invalid;).
1228</t>
1229</section>
1230
1231<section title="TRACE" anchor="TRACE">
1232  <rdf:Description>
1233    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1234  </rdf:Description>
1235  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1236  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1237<t>
1238   The TRACE method requests a remote, application-layer loop-back
1239   of the request message. The final recipient of the request
1240   &SHOULD; reflect the message received back to the client as the
1241   message-body of a 200 (OK) response. The final recipient is either the
1242   origin server or the first proxy to receive a Max-Forwards
1243   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1244   A TRACE request &MUST-NOT; include a message-body.
1245</t>
1246<t>
1247   TRACE allows the client to see what is being received at the other
1248   end of the request chain and use that data for testing or diagnostic
1249   information. The value of the Via header field (&header-via;) is of
1250   particular interest, since it acts as a trace of the request chain.
1251   Use of the Max-Forwards header field allows the client to limit the
1252   length of the request chain, which is useful for testing a chain of
1253   proxies forwarding messages in an infinite loop.
1254</t>
1255<t>
1256   If the request is valid, the response &SHOULD; have a Content-Type of
1257   "message/http" (see &media-type-message-http;) and contain a message-body
1258   that encloses a copy of the entire request message.
1259   Responses to the TRACE method are not cacheable.
1260</t>
1261</section>
1262
1263<section title="CONNECT" anchor="CONNECT">
1264  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1265  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1266<t>
1267   The CONNECT method requests that the proxy establish a tunnel
1268   to the request-target and then restrict its behavior to blind
1269   forwarding of packets until the connection is closed.
1270</t>
1271<t>
1272   When using CONNECT, the request-target &MUST; use the authority form
1273   (&request-target;); i.e., the request-target consists of only the
1274   host name and port number of the tunnel destination, separated by a colon.
1275   For example,
1276</t>
1277<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1278CONNECT server.example.com:80 HTTP/1.1
1279Host: server.example.com:80
1280
1281</artwork></figure>
1282<t>
1283   Other HTTP mechanisms can be used normally with the CONNECT method &mdash;
1284   except end-to-end protocol Upgrade requests, since the
1285   tunnel must be established first.
1286</t>
1287<t>
1288   For example, proxy authentication might be used to establish the
1289   authority to create a tunnel:
1290</t>
1291<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1292CONNECT server.example.com:80 HTTP/1.1
1293Host: server.example.com:80
1294Proxy-Authorization: basic aGVsbG86d29ybGQ=
1295
1296</artwork></figure>
1297<t>
1298   Bodies on CONNECT requests have no defined semantics. Note that sending a body
1299   on a CONNECT request might cause some existing implementations to reject the
1300   request.
1301</t>
1302<t>
1303   Like any other pipelined HTTP/1.1 request, data to be tunnel may be
1304   sent immediately after the blank line. The usual caveats also apply:
1305   data may be discarded if the eventual response is negative, and the
1306   connection may be reset with no response if more than one TCP segment
1307   is outstanding.
1308</t>
1309
1310<section title="Establishing a Tunnel with CONNECT">
1311<t>
1312   Any successful (2xx) response to a CONNECT request indicates that the
1313   proxy has established a connection to the requested host and port,
1314   and has switched to tunneling the current connection to that server
1315   connection.
1316</t>
1317<t>
1318   It may be the case that the proxy itself can only reach the requested
1319   origin server through another proxy.  In this case, the first proxy
1320   &SHOULD; make a CONNECT request of that next proxy, requesting a tunnel
1321   to the authority.  A proxy &MUST-NOT; respond with any 2xx status code
1322   unless it has either a direct or tunnel connection established to the
1323   authority.
1324</t>
1325<t>
1326   An origin server which receives a CONNECT request for itself &MAY;
1327   respond with a 2xx status code to indicate that a connection is
1328   established.
1329</t>
1330<t>
1331   If at any point either one of the peers gets disconnected, any
1332   outstanding data that came from that peer will be passed to the other
1333   one, and after that also the other connection will be terminated by
1334   the proxy. If there is outstanding data to that peer undelivered,
1335   that data will be discarded.
1336</t>
1337
1338</section>
1339</section>
1340</section>
1341
1342
1343<section title="Status Code Definitions" anchor="status.codes">
1344<t>
1345   The first digit of the Status-Code defines the class of response. The
1346   last two digits do not have any categorization role. There are 5
1347   values for the first digit:
1348  <list style="symbols">
1349    <t>
1350      1xx: Informational - Request received, continuing process
1351    </t>
1352    <t>
1353      2xx: Success - The action was successfully received,
1354        understood, and accepted
1355    </t>
1356    <t>
1357      3xx: Redirection - Further action must be taken in order to
1358        complete the request
1359    </t>
1360    <t>
1361      4xx: Client Error - The request contains bad syntax or cannot
1362        be fulfilled
1363    </t>
1364    <t>
1365      5xx: Server Error - The server failed to fulfill an apparently
1366        valid request
1367    </t>
1368  </list>
1369</t>
1370<t>
1371   Each Status-Code is described below, including any metadata required
1372   in the response.
1373</t>
1374
1375<section title="Informational 1xx" anchor="status.1xx">
1376<t>
1377   This class of status code indicates a provisional response,
1378   consisting only of the Status-Line and optional header fields, and is
1379   terminated by an empty line. There are no required header fields for this
1380   class of status code. Since HTTP/1.0 did not define any 1xx status
1381   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1382   except under experimental conditions.
1383</t>
1384<t>
1385   A client &MUST; be prepared to accept one or more 1xx status responses
1386   prior to a regular response, even if the client does not expect a 100
1387   (Continue) status message. Unexpected 1xx status responses &MAY; be
1388   ignored by a user agent.
1389</t>
1390<t>
1391   Proxies &MUST; forward 1xx responses, unless the connection between the
1392   proxy and its client has been closed, or unless the proxy itself
1393   requested the generation of the 1xx response. (For example, if a
1394   proxy adds a "Expect: 100-continue" field when it forwards a request,
1395   then it need not forward the corresponding 100 (Continue)
1396   response(s).)
1397</t>
1398
1399<section title="100 Continue" anchor="status.100">
1400  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1401  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1402<t>
1403   The client &SHOULD; continue with its request. This interim response is
1404   used to inform the client that the initial part of the request has
1405   been received and has not yet been rejected by the server. The client
1406   &SHOULD; continue by sending the remainder of the request or, if the
1407   request has already been completed, ignore this response. The server
1408   &MUST; send a final response after the request has been completed. See
1409   &use100; for detailed discussion of the use and handling of this
1410   status code.
1411</t>
1412</section>
1413
1414<section title="101 Switching Protocols" anchor="status.101">
1415  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1416  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1417<t>
1418   The server understands and is willing to comply with the client's
1419   request, via the Upgrade message header field (&header-upgrade;), for a
1420   change in the application protocol being used on this connection. The
1421   server will switch protocols to those defined by the response's
1422   Upgrade header field immediately after the empty line which
1423   terminates the 101 response.
1424</t>
1425<t>
1426   The protocol &SHOULD; be switched only when it is advantageous to do
1427   so. For example, switching to a newer version of HTTP is advantageous
1428   over older versions, and switching to a real-time, synchronous
1429   protocol might be advantageous when delivering resources that use
1430   such features.
1431</t>
1432</section>
1433</section>
1434
1435<section title="Successful 2xx" anchor="status.2xx">
1436<t>
1437   This class of status code indicates that the client's request was
1438   successfully received, understood, and accepted.
1439</t>
1440
1441<section title="200 OK" anchor="status.200">
1442  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1443  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1444<t>
1445   The request has succeeded. The payload returned with the response
1446   is dependent on the method used in the request, for example:
1447  <list style="hanging">
1448    <t hangText="GET">
1449      a representation of the target resource is sent in the response;
1450    </t>
1451    <t hangText="HEAD">
1452      the same representation as GET, except without the message-body;
1453    </t>
1454    <t hangText="POST">
1455      a representation describing or containing the result of the action;
1456    </t>
1457    <t hangText="TRACE">
1458      a representation containing the request message as received by the
1459      end server.
1460    </t>
1461  </list>
1462</t>
1463<t>
1464   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1465   freshness for 200 responses.
1466</t>
1467</section>
1468
1469<section title="201 Created" anchor="status.201">
1470  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1471  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1472<t>
1473   The request has been fulfilled and has resulted in a new resource being
1474   created. The newly created resource can be referenced by the URI(s)
1475   returned in the payload of the response, with the most specific URI
1476   for the resource given by a Location header field. The response
1477   &SHOULD; include a payload containing a list of resource
1478   characteristics and location(s) from which the user or user agent can
1479   choose the one most appropriate. The payload format is specified by
1480   the media type given in the Content-Type header field. The origin
1481   server &MUST; create the resource before returning the 201 status code.
1482   If the action cannot be carried out immediately, the server &SHOULD;
1483   respond with 202 (Accepted) response instead.
1484</t>
1485<t>
1486   A 201 response &MAY; contain an ETag response header field indicating
1487   the current value of the entity-tag for the representation of the resource
1488   just created (see &header-etag;).
1489</t>
1490</section>
1491
1492<section title="202 Accepted" anchor="status.202">
1493  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1494  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1495<t>
1496   The request has been accepted for processing, but the processing has
1497   not been completed.  The request might or might not eventually be
1498   acted upon, as it might be disallowed when processing actually takes
1499   place. There is no facility for re-sending a status code from an
1500   asynchronous operation such as this.
1501</t>
1502<t>
1503   The 202 response is intentionally non-committal. Its purpose is to
1504   allow a server to accept a request for some other process (perhaps a
1505   batch-oriented process that is only run once per day) without
1506   requiring that the user agent's connection to the server persist
1507   until the process is completed. The representation returned with this
1508   response &SHOULD; include an indication of the request's current status
1509   and either a pointer to a status monitor or some estimate of when the
1510   user can expect the request to be fulfilled.
1511</t>
1512</section>
1513
1514<section title="203 Non-Authoritative Information" anchor="status.203">
1515  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1516  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1517<t>
1518   The representation in the response has been transformed or otherwise
1519   modified by a transforming proxy (&intermediaries;).  Note that the
1520   behaviour of transforming intermediaries is controlled by the no-transform
1521   Cache-Control directive (&header-cache-control;).
1522</t>
1523<t>
1524   This status code is only appropriate when the response status code would
1525   have been 200 (OK) otherwise. When the status code before transformation
1526   would have been different, the 214 Transformation Applied warn-code
1527   (&header-warning;) is appropriate.
1528</t>
1529<t>
1530   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1531   freshness for 203 responses.
1532</t>
1533</section>
1534
1535<section title="204 No Content" anchor="status.204">
1536  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1537  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1538<t>
1539   The 204 (No Content) status code indicates that the server has
1540   successfully fulfilled the request and that there is no additional
1541   content to return in the response payload body.  Metadata in the
1542   response header fields refer to the target resource and its current
1543   representation after the requested action.
1544</t>
1545<t>
1546   For example, if a 204 status code is received in response to a PUT
1547   request and the response contains an ETag header field, then the PUT
1548   was successful and the ETag field-value contains the entity-tag for
1549   the new representation of that target resource.
1550</t>
1551<t>
1552   The 204 response allows a server to indicate that the action has been
1553   successfully applied to the target resource while implying that the
1554   user agent &SHOULD-NOT; traverse away from its current "document view"
1555   (if any).  The server assumes that the user agent will provide some
1556   indication of the success to its user, in accord with its own interface,
1557   and apply any new or updated metadata in the response to the active
1558   representation.
1559</t>
1560<t>
1561   For example, a 204 status code is commonly used with document editing
1562   interfaces corresponding to a "save" action, such that the document
1563   being saved remains available to the user for editing. It is also
1564   frequently used with interfaces that expect automated data transfers
1565   to be prevalent, such as within distributed version control systems.
1566</t>
1567<t>
1568   The 204 response &MUST-NOT; include a message-body, and thus is always
1569   terminated by the first empty line after the header fields.
1570</t>
1571</section>
1572
1573<section title="205 Reset Content" anchor="status.205">
1574  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1575  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1576<t>
1577   The server has fulfilled the request and the user agent &SHOULD; reset
1578   the document view which caused the request to be sent. This response
1579   is primarily intended to allow input for actions to take place via
1580   user input, followed by a clearing of the form in which the input is
1581   given so that the user can easily initiate another input action.
1582</t>
1583<t>   
1584   The message-body included with the response &MUST; be empty. Note that
1585   receivers still need to parse the response according to the algorithm defined
1586   in &message-body;.
1587</t>
1588</section>
1589
1590<section title="206 Partial Content" anchor="status.206">
1591  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1592  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1593  <rdf:Description>
1594    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1595  </rdf:Description>
1596<t>
1597   The server has fulfilled the partial GET request for the resource
1598   and the enclosed payload is a partial representation as defined in &status-206;.
1599</t>
1600<t>
1601   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1602   freshness for 206 responses.
1603</t>
1604</section>
1605</section>
1606
1607<section title="Redirection 3xx" anchor="status.3xx">
1608<t>
1609   This class of status code indicates that further action needs to be
1610   taken by the user agent in order to fulfill the request.  If the required
1611   action involves a subsequent HTTP request, it &MAY; be carried out by the
1612   user agent without interaction with the user if and only if the method used
1613   in the second request is known to be "safe", as defined in
1614   <xref target="safe.methods"/>.
1615</t>
1616<t>
1617   There are several types of redirects:
1618   <list style="numbers">
1619      <x:lt>
1620        <t>
1621          Redirects of the request to another URI, either temporarily or
1622          permanently. The new URI is specified in the Location header field.
1623          In this specification, the status codes 301 (Moved Permanently),
1624          302 (Found), and 307 (Temporary Redirect) fall under this category.
1625        </t>
1626      </x:lt>
1627      <x:lt>
1628        <t>
1629          Redirection to a new location that represents an indirect response to
1630          the request, such as the result of a POST operation to be retrieved
1631          with a subsequent GET request. This is status code 303 (See Other).
1632        </t>
1633      </x:lt>
1634      <x:lt>
1635        <t>
1636          Redirection offering a choice of matching resources for use by
1637          agent-driven content negotiation (&agent-driven-negotiation;). This
1638          is status code 300 (Multiple Choices).
1639        </t>
1640      </x:lt>
1641      <x:lt>
1642        <t>
1643          Other kinds of redirection, such as to a cached result (status code 304
1644          (Not Modified)).
1645        </t>
1646      </x:lt>
1647   </list>
1648</t>
1649<x:note>
1650  <t>
1651    <x:h>Note:</x:h> In HTTP/1.0, only the status codes 301 (Moved Permanently)
1652    and 302 (Found) were defined for the first type of redirect, and the second
1653    type did not exist at all (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>).
1654    However it turned out that web forms using POST expected redirects to change
1655    the operation for the subsequent request to retrieval (GET). To address this
1656    use case, HTTP/1.1 introduced the second type of redirect with the status
1657    code 303 (See Other) (<xref target="RFC2068" x:fmt="," x:sec="10.3.4"/>).
1658    As user agents did not change their behavior to maintain backwards
1659    compatibility, the first revision of HTTP/1.1 added yet another status code,
1660    307 (Temporary Redirect), for which the backwards compatibility problems did
1661    not apply (<xref target="RFC2616" x:fmt="," x:sec="10.3.8"/>).
1662    Over 10 years later, most user agents still do method rewriting for
1663    status codes 301 and 302, therefore this specification makes that behavior
1664    compliant in case the original request was POST.
1665  </t>
1666</x:note>
1667<t>
1668   Clients &SHOULD; detect and intervene in cyclical redirections (i.e.,
1669   "infinite" redirection loops).
1670</t>
1671<x:note>
1672  <t>
1673    <x:h>Note:</x:h> An earlier version of this specification recommended a
1674    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1675    Content developers need to be aware that some clients might
1676    implement such a fixed limitation.
1677  </t>
1678</x:note>
1679
1680<section title="300 Multiple Choices" anchor="status.300">
1681  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1682  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1683<t>
1684   The target resource has more than one
1685   representation, each with its own specific location, and agent-driven
1686   negotiation information (&content-negotiation;) is being provided so that
1687   the user (or user agent) can select a preferred representation by
1688   redirecting its request to that location.
1689</t>
1690<t>
1691   Unless it was a HEAD request, the response &SHOULD; include a representation
1692   containing a list of representation metadata and location(s) from
1693   which the user or user agent can choose the one most appropriate. The
1694   data format is specified by the media type given in the Content-Type
1695   header field. Depending upon the format and the capabilities of
1696   the user agent, selection of the most appropriate choice &MAY; be
1697   performed automatically. However, this specification does not define
1698   any standard for such automatic selection.
1699</t>
1700<t>
1701   If the server has a preferred choice of representation, it &SHOULD;
1702   include the specific URI for that representation in the Location
1703   field; user agents &MAY; use the Location field value for automatic
1704   redirection.
1705</t>
1706<t>
1707   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1708   freshness for 300 responses.
1709</t>
1710
1711</section>
1712
1713<section title="301 Moved Permanently" anchor="status.301">
1714  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1715  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1716<t>
1717   The target resource has been assigned a new permanent URI and any
1718   future references to this resource &SHOULD; use one of the returned
1719   URIs.  Clients with link editing capabilities ought to automatically
1720   re-link references to the effective request URI to one or more of the new
1721   references returned by the server, where possible.
1722</t>
1723<t>
1724   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1725   freshness for 301 responses.
1726</t>
1727<t>
1728   The new permanent URI &SHOULD; be given by the Location field in the
1729   response. Unless the request method was HEAD, the representation of the
1730   response &SHOULD; contain a short hypertext note with a hyperlink to
1731   the new URI(s).
1732</t>
1733<t>
1734   If the 301 status code is received in response to a request method
1735   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1736   then the request &MAY; be automatically redirected by the user agent without
1737   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1738   request unless it can be confirmed by the user, since this might
1739   change the conditions under which the request was issued.
1740</t>
1741<x:note>
1742  <t>
1743    <x:h>Note:</x:h> For historic reasons, user agents &MAY; change the
1744    request method from POST to GET for the subsequent request. If this
1745    behavior is undesired, status code 307 (Temporary Redirect) can be used
1746    instead.
1747  </t>
1748</x:note>
1749</section>
1750
1751<section title="302 Found" anchor="status.302">
1752  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1753  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1754<t>
1755   The target resource resides temporarily under a different URI.
1756   Since the redirection might be altered on occasion, the client &SHOULD;
1757   continue to use the effective request URI for future requests.
1758</t>
1759<t>
1760   The temporary URI &SHOULD; be given by the Location field in the
1761   response. Unless the request method was HEAD, the representation of the
1762   response &SHOULD; contain a short hypertext note with a hyperlink to
1763   the new URI(s).
1764</t>
1765<t>
1766   If the 302 status code is received in response to a request method
1767   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1768   then the request &MAY; be automatically redirected by the user agent without
1769   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1770   request unless it can be confirmed by the user, since this might
1771   change the conditions under which the request was issued.
1772</t>
1773<x:note>
1774  <t>
1775    <x:h>Note:</x:h> For historic reasons, user agents &MAY; change the
1776    request method from POST to GET for the subsequent request. If this
1777    behavior is undesired, status code 307 (Temporary Redirect) can be used
1778    instead.
1779    <cref anchor="issue312">but see <eref target="http://trac.tools.ietf.org/wg/httpbis/trac/ticket/312"/></cref>
1780  </t>
1781</x:note>
1782</section>
1783
1784<section title="303 See Other" anchor="status.303">
1785  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1786  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1787<t>
1788   The 303 status code indicates that the server is redirecting the
1789   user agent to a different resource, as indicated by a URI in the
1790   Location header field, that is intended to provide an indirect
1791   response to the original request.  In order to satisfy the original
1792   request, a user agent &SHOULD; perform a retrieval request using the
1793   Location URI (a GET or HEAD request if using HTTP), which
1794   may itself be redirected further, and present the eventual result as an
1795   answer to the original request.
1796   Note that the new URI in the Location header field is not considered
1797   equivalent to the effective request URI.
1798</t>
1799<t>
1800   This status code is generally applicable to any HTTP method.  It is
1801   primarily used to allow the output of a POST action to redirect
1802   the user agent to a selected resource, since doing so provides the
1803   information corresponding to the POST response in a form that
1804   can be separately identified, bookmarked, and cached independent
1805   of the original request.
1806</t>
1807<t>
1808   A 303 response to a GET request indicates that the requested
1809   resource does not have a representation of its own that can be
1810   transferred by the server over HTTP.  The Location URI indicates a
1811   resource that is descriptive of the target resource, such that the
1812   follow-on representation might be useful to recipients without
1813   implying that it adequately represents the target resource.
1814   Note that answers to the questions of what can be represented, what
1815   representations are adequate, and what might be a useful description
1816   are outside the scope of HTTP and thus entirely determined by the
1817   URI owner(s).
1818</t>
1819<t>
1820   Except for responses to a HEAD request, the representation of a 303
1821   response &SHOULD; contain a short hypertext note with a hyperlink
1822   to the Location URI.
1823</t>
1824</section>
1825
1826<section title="304 Not Modified" anchor="status.304">
1827  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1828  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1829  <rdf:Description>
1830    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1831  </rdf:Description>
1832<t>
1833   The response to the request has not been modified since the conditions
1834   indicated by the client's conditional GET request, as defined in &status-304;.
1835</t>
1836</section>
1837
1838<section title="305 Use Proxy" anchor="status.305">
1839  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1840  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1841<t>
1842   The 305 status code was defined in a previous version of this specification
1843   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1844</t>
1845</section>
1846
1847<section title="306 (Unused)" anchor="status.306">
1848  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1849  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1850<t>
1851   The 306 status code was used in a previous version of the
1852   specification, is no longer used, and the code is reserved.
1853</t>
1854</section>
1855
1856<section title="307 Temporary Redirect" anchor="status.307">
1857  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1858  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1859<t>
1860   The target resource resides temporarily under a different URI.
1861   Since the redirection can change over time, the client &SHOULD;
1862   continue to use the effective request URI for future requests.
1863</t>
1864<t>
1865   The temporary URI &SHOULD; be given by the Location field in the
1866   response. Unless the request method was HEAD, the representation of the
1867   response &SHOULD; contain a short hypertext note with a hyperlink to
1868   the new URI(s), since many pre-HTTP/1.1 user agents do not
1869   understand the 307 status code. Therefore, the note &SHOULD; contain the
1870   information necessary for a user to repeat the original request on
1871   the new URI.
1872</t>
1873<t>
1874   If the 307 status code is received in response to a request method
1875   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1876   then the request &MAY; be automatically redirected by the user agent without
1877   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1878   request unless it can be confirmed by the user, since this might
1879   change the conditions under which the request was issued.
1880</t>
1881</section>
1882</section>
1883
1884<section title="Client Error 4xx" anchor="status.4xx">
1885<t>
1886   The 4xx class of status code is intended for cases in which the
1887   client seems to have erred. Except when responding to a HEAD request,
1888   the server &SHOULD; include a representation containing an explanation of the
1889   error situation, and whether it is a temporary or permanent
1890   condition. These status codes are applicable to any request method.
1891   User agents &SHOULD; display any included representation to the user.
1892</t>
1893<t>
1894   If the client is sending data, a server implementation using TCP
1895   &SHOULD; be careful to ensure that the client acknowledges receipt of
1896   the packet(s) containing the response, before the server closes the
1897   input connection. If the client continues sending data to the server
1898   after the close, the server's TCP stack will send a reset packet to
1899   the client, which might erase the client's unacknowledged input buffers
1900   before they can be read and interpreted by the HTTP application.
1901</t>
1902
1903<section title="400 Bad Request" anchor="status.400">
1904  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1905  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1906<t>
1907   The server cannot or will not process the request, due to a client error (e.g.,
1908   malformed syntax).</t>
1909</section>
1910
1911<section title="401 Unauthorized" anchor="status.401">
1912  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1913  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1914  <rdf:Description>
1915    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1916  </rdf:Description>
1917<t>
1918   The request requires user authentication (see &status-401;).
1919</t>
1920</section>
1921
1922<section title="402 Payment Required" anchor="status.402">
1923  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1924  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1925<t>
1926   This code is reserved for future use.
1927</t>
1928</section>
1929
1930<section title="403 Forbidden" anchor="status.403">
1931  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1932  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1933<t>
1934   The server understood the request, but refuses to authorize it. Providing
1935   different user authentication credentials might be successful, but any
1936   credentials that were provided in the request are insufficient. The request
1937   &SHOULD-NOT; be repeated with the same credentials.
1938</t>
1939<t>
1940   If the request method was not HEAD and the server wishes to make
1941   public why the request has not been fulfilled, it &SHOULD; describe the
1942   reason for the refusal in the representation.  If the server does not wish to
1943   make this information available to the client, the status code 404
1944   (Not Found) &MAY; be used instead.
1945</t>
1946</section>
1947
1948<section title="404 Not Found" anchor="status.404">
1949  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1950  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1951<t>
1952   The server has not found anything matching the effective request URI. No
1953   indication is given of whether the condition is temporary or
1954   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1955   knows, through some internally configurable mechanism, that an old
1956   resource is permanently unavailable and has no forwarding address.
1957   This status code is commonly used when the server does not wish to
1958   reveal exactly why the request has been refused, or when no other
1959   response is applicable.
1960</t>
1961</section>
1962
1963<section title="405 Method Not Allowed" anchor="status.405">
1964  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1965  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1966<t>
1967   The method specified in the Request-Line is not allowed for the target
1968   resource. The response &MUST; include an Allow header field containing a
1969   list of valid methods for the requested resource.
1970</t>
1971</section>
1972
1973<section title="406 Not Acceptable" anchor="status.406">
1974  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1975  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1976<t>
1977   The resource identified by the request is only capable of generating
1978   response representations which have content characteristics not acceptable
1979   according to the Accept and Accept-* header fields sent in the request
1980   (see &p3-header-fields;).
1981</t>
1982<t>
1983   Unless it was a HEAD request, the response &SHOULD; include a representation
1984   containing a list of available representation characteristics and location(s)
1985   from which the user or user agent can choose the one most
1986   appropriate. The data format is specified by the media type given
1987   in the Content-Type header field. Depending upon the format and the
1988   capabilities of the user agent, selection of the most appropriate
1989   choice &MAY; be performed automatically. However, this specification
1990   does not define any standard for such automatic selection.
1991</t>
1992<x:note>
1993  <t>
1994    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1995    not acceptable according to the accept header fields sent in the
1996    request. In some cases, this might even be preferable to sending a
1997    406 response. User agents are encouraged to inspect the header fields of
1998    an incoming response to determine if it is acceptable.
1999  </t>
2000</x:note>
2001<t>
2002   If the response could be unacceptable, a user agent &SHOULD;
2003   temporarily stop receipt of more data and query the user for a
2004   decision on further actions.
2005</t>
2006</section>
2007
2008<section title="407 Proxy Authentication Required" anchor="status.407">
2009  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
2010  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
2011<t>
2012   This code is similar to 401 (Unauthorized), but indicates that the
2013   client must first authenticate itself with the proxy (see &status-407;).
2014</t>
2015</section>
2016
2017<section title="408 Request Timeout" anchor="status.408">
2018  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
2019  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
2020<t>
2021   The client did not produce a request within the time that the server
2022   was prepared to wait. The client &MAY; repeat the request without
2023   modifications at any later time.
2024</t>
2025</section>
2026
2027<section title="409 Conflict" anchor="status.409">
2028  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
2029  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
2030<t>
2031   The request could not be completed due to a conflict with the current
2032   state of the resource. This code is only allowed in situations where
2033   it is expected that the user might be able to resolve the conflict
2034   and resubmit the request. The response body &SHOULD; include enough
2035   information for the user to recognize the source of the conflict.
2036   Ideally, the response representation would include enough information for the
2037   user or user agent to fix the problem; however, that might not be
2038   possible and is not required.
2039</t>
2040<t>
2041   Conflicts are most likely to occur in response to a PUT request. For
2042   example, if versioning were being used and the representation being PUT
2043   included changes to a resource which conflict with those made by an
2044   earlier (third-party) request, the server might use the 409 response
2045   to indicate that it can't complete the request. In this case, the
2046   response representation would likely contain a list of the differences
2047   between the two versions in a format defined by the response
2048   Content-Type.
2049</t>
2050</section>
2051
2052<section title="410 Gone" anchor="status.410">
2053  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
2054  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
2055<t>
2056   The target resource is no longer available at the server and no
2057   forwarding address is known. This condition is expected to be
2058   considered permanent. Clients with link editing capabilities &SHOULD;
2059   delete references to the effective request URI after user approval. If the
2060   server does not know, or has no facility to determine, whether or not
2061   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
2062   used instead.
2063</t>
2064<t>
2065   The 410 response is primarily intended to assist the task of web
2066   maintenance by notifying the recipient that the resource is
2067   intentionally unavailable and that the server owners desire that
2068   remote links to that resource be removed. Such an event is common for
2069   limited-time, promotional services and for resources belonging to
2070   individuals no longer working at the server's site. It is not
2071   necessary to mark all permanently unavailable resources as "gone" or
2072   to keep the mark for any length of time &mdash; that is left to the
2073   discretion of the server owner.
2074</t>
2075<t>
2076   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine freshness
2077   for 410 responses.
2078</t>
2079
2080</section>
2081
2082<section title="411 Length Required" anchor="status.411">
2083  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
2084  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
2085<t>
2086   The server refuses to accept the request without a defined Content-Length.
2087   The client &MAY; repeat the request if it adds a valid
2088   Content-Length header field containing the length of the message-body
2089   in the request message.
2090</t>
2091</section>
2092
2093<section title="412 Precondition Failed" anchor="status.412">
2094  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
2095  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
2096  <rdf:Description>
2097    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
2098  </rdf:Description>
2099<t>
2100   The precondition given in one or more of the header fields
2101   evaluated to false when it was tested on the server, as defined in
2102   &status-412;.
2103</t>
2104</section>
2105
2106<section title="413 Request Representation Too Large" anchor="status.413">
2107  <iref primary="true" item="413 Request Representation Too Large (status code)" x:for-anchor=""/>
2108  <iref primary="true" item="Status Codes" subitem="413 Request Representation Too Large" x:for-anchor=""/>
2109<t>
2110   The server is refusing to process a request because the request
2111   representation is larger than the server is willing or able to process. The
2112   server &MAY; close the connection to prevent the client from continuing
2113   the request.
2114</t>
2115<t>
2116   If the condition is temporary, the server &SHOULD; include a Retry-After
2117   header field to indicate that it is temporary and after what
2118   time the client &MAY; try again.
2119</t>
2120</section>
2121
2122<section title="414 URI Too Long" anchor="status.414">
2123  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
2124  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
2125<t>
2126   The server is refusing to service the request because the effective request URI
2127   is longer than the server is willing to interpret. This rare
2128   condition is only likely to occur when a client has improperly
2129   converted a POST request to a GET request with long query
2130   information, when the client has descended into a URI "black hole" of
2131   redirection (e.g., a redirected URI prefix that points to a suffix of
2132   itself), or when the server is under attack by a client attempting to
2133   exploit security holes present in some servers using fixed-length
2134   buffers for reading or manipulating the effective request URI.
2135</t>
2136</section>
2137
2138<section title="415 Unsupported Media Type" anchor="status.415">
2139  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
2140  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
2141<t>
2142   The server is refusing to service the request because the request
2143   payload is in a format not supported by this request method on the
2144   target resource.
2145</t>
2146</section>
2147
2148<section title="416 Requested Range Not Satisfiable" anchor="status.416">
2149  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
2150  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
2151  <rdf:Description>
2152    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
2153  </rdf:Description>
2154<t>
2155   The request included a Range header field (&header-range;) and none of
2156   the range-specifier values in this field overlap the current extent
2157   of the selected resource. See &status-416;.
2158</t>
2159</section>
2160
2161<section title="417 Expectation Failed" anchor="status.417">
2162  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
2163  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
2164<t>
2165   The expectation given in an Expect header field (see <xref target="header.expect"/>)
2166   could not be met by this server, or, if the server is a proxy,
2167   the server has unambiguous evidence that the request could not be met
2168   by the next-hop server.
2169</t>
2170</section>
2171
2172<section title="426 Upgrade Required" anchor="status.426">
2173  <iref primary="true" item="426 Upgrade Required (status code)" x:for-anchor=""/>
2174  <iref primary="true" item="Status Codes" subitem="426 Upgrade Required" x:for-anchor=""/>
2175<t>
2176   The request can not be completed without a prior protocol upgrade. This
2177   response &MUST; include an Upgrade header field (&header-upgrade;)
2178   specifying the required protocols.
2179</t>
2180<figure>
2181<preamble>Example:</preamble>
2182<artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
2183HTTP/1.1 426 Upgrade Required
2184Upgrade: HTTP/2.0
2185Connection: Upgrade
2186
2187</artwork></figure>
2188<t>
2189   The server &SHOULD; include a message body in the 426 response which
2190   indicates in human readable form the reason for the error and describes any
2191   alternative courses which may be available to the user.
2192</t>
2193</section>
2194</section>
2195
2196<section title="Server Error 5xx" anchor="status.5xx">
2197<t>
2198   Response status codes beginning with the digit "5" indicate cases in
2199   which the server is aware that it has erred or is incapable of
2200   performing the request. Except when responding to a HEAD request, the
2201   server &SHOULD; include a representation containing an explanation of the
2202   error situation, and whether it is a temporary or permanent
2203   condition. User agents &SHOULD; display any included representation to the
2204   user. These response codes are applicable to any request method.
2205</t>
2206
2207<section title="500 Internal Server Error" anchor="status.500">
2208  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
2209  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
2210<t>
2211   The server encountered an unexpected condition which prevented it
2212   from fulfilling the request.
2213</t>
2214</section>
2215
2216<section title="501 Not Implemented" anchor="status.501">
2217  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
2218  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
2219<t>
2220   The server does not support the functionality required to fulfill the
2221   request. This is the appropriate response when the server does not
2222   recognize the request method and is not capable of supporting it for
2223   any resource.
2224</t>
2225</section>
2226
2227<section title="502 Bad Gateway" anchor="status.502">
2228  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
2229  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
2230<t>
2231   The server, while acting as a gateway or proxy, received an invalid
2232   response from the upstream server it accessed in attempting to
2233   fulfill the request.
2234</t>
2235</section>
2236
2237<section title="503 Service Unavailable" anchor="status.503">
2238  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
2239  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
2240<t>
2241   The server is currently unable or unwilling to handle the request due to
2242   reasons such as temporary overloading, maintenance of the server, or rate
2243   limiting of the client.
2244</t>
2245<t>
2246   The implication is that this is a temporary condition which will be
2247   alleviated after some delay. If known, the length of the delay &MAY; be
2248   indicated in a Retry-After header field (<xref target="header.retry-after"/>).
2249   If no Retry-After is given, the client &SHOULD; handle the response as it
2250   would for a 500 response.
2251</t>
2252<x:note>
2253  <t>
2254    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
2255    server must use it when becoming overloaded. Some servers might wish
2256    to simply refuse the connection.
2257  </t>
2258</x:note>
2259</section>
2260
2261<section title="504 Gateway Timeout" anchor="status.504">
2262  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
2263  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
2264<t>
2265   The server, while acting as a gateway or proxy, did not receive a
2266   timely response from the upstream server specified by the URI (e.g.,
2267   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
2268   to access in attempting to complete the request.
2269</t>
2270<x:note>
2271  <t>
2272    <x:h>Note</x:h> to implementors: some deployed proxies are known to
2273    return 400 or 500 when DNS lookups time out.
2274  </t>
2275</x:note>
2276</section>
2277
2278<section title="505 HTTP Version Not Supported" anchor="status.505">
2279  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
2280  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
2281<t>
2282   The server does not support, or refuses to support, the protocol
2283   version that was used in the request message. The server is
2284   indicating that it is unable or unwilling to complete the request
2285   using the same major version as the client, as described in &http-version;,
2286   other than with this error message. The response &SHOULD; contain
2287   a representation describing why that version is not supported and what other
2288   protocols are supported by that server.
2289</t>
2290
2291</section>
2292</section>
2293</section>
2294
2295
2296<section title="Date/Time Formats" anchor="http.date">
2297  <x:anchor-alias value="HTTP-date"/>
2298<t>
2299   HTTP applications have historically allowed three different formats
2300   for date/time stamps. However, the preferred format is a fixed-length subset
2301   of that defined by <xref target="RFC1123"/>:
2302</t>
2303<figure><artwork type="example" x:indent-with="  ">
2304Sun, 06 Nov 1994 08:49:37 GMT  ; RFC 1123
2305</artwork></figure>
2306<t>
2307   The other formats are described here only for compatibility with obsolete
2308   implementations.
2309</t>
2310<figure><artwork type="example" x:indent-with="  ">
2311Sunday, 06-Nov-94 08:49:37 GMT ; obsolete RFC 850 format
2312Sun Nov  6 08:49:37 1994       ; ANSI C's asctime() format
2313</artwork></figure>
2314<t>
2315   HTTP/1.1 clients and servers that parse a date value &MUST; accept
2316   all three formats (for compatibility with HTTP/1.0), though they &MUST;
2317   only generate the RFC 1123 format for representing HTTP-date values
2318   in header fields.
2319</t>
2320<t>
2321   All HTTP date/time stamps &MUST; be represented in Greenwich Mean Time
2322   (GMT), without exception. For the purposes of HTTP, GMT is exactly
2323   equal to UTC (Coordinated Universal Time). This is indicated in the
2324   first two formats by the inclusion of "GMT" as the three-letter
2325   abbreviation for time zone, and &MUST; be assumed when reading the
2326   asctime format. HTTP-date is case sensitive and &MUST-NOT; include
2327   additional whitespace beyond that specifically included as SP in the
2328   grammar.
2329</t>
2330<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="HTTP-date"/>
2331  <x:ref>HTTP-date</x:ref>    = <x:ref>rfc1123-date</x:ref> / <x:ref>obs-date</x:ref>
2332</artwork></figure>
2333<t anchor="preferred.date.format">
2334  <x:anchor-alias value="rfc1123-date"/>
2335  <x:anchor-alias value="time-of-day"/>
2336  <x:anchor-alias value="hour"/>
2337  <x:anchor-alias value="minute"/>
2338  <x:anchor-alias value="second"/>
2339  <x:anchor-alias value="day-name"/>
2340  <x:anchor-alias value="day"/>
2341  <x:anchor-alias value="month"/>
2342  <x:anchor-alias value="year"/>
2343  <x:anchor-alias value="GMT"/>
2344  Preferred format:
2345</t>
2346<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"/>
2347  <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>
2348  ; fixed length subset of the format defined in
2349  ; <xref target="RFC1123" x:fmt="of" x:sec="5.2.14"/>
2350 
2351  <x:ref>day-name</x:ref>     = <x:abnf-char-sequence>"Mon"</x:abnf-char-sequence> ; "Mon", case-sensitive
2352               / <x:abnf-char-sequence>"Tue"</x:abnf-char-sequence> ; "Tue", case-sensitive
2353               / <x:abnf-char-sequence>"Wed"</x:abnf-char-sequence> ; "Wed", case-sensitive
2354               / <x:abnf-char-sequence>"Thu"</x:abnf-char-sequence> ; "Thu", case-sensitive
2355               / <x:abnf-char-sequence>"Fri"</x:abnf-char-sequence> ; "Fri", case-sensitive
2356               / <x:abnf-char-sequence>"Sat"</x:abnf-char-sequence> ; "Sat", case-sensitive
2357               / <x:abnf-char-sequence>"Sun"</x:abnf-char-sequence> ; "Sun", case-sensitive
2358               
2359  <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>
2360               ; e.g., 02 Jun 1982
2361
2362  <x:ref>day</x:ref>          = 2<x:ref>DIGIT</x:ref>
2363  <x:ref>month</x:ref>        = <x:abnf-char-sequence>"Jan"</x:abnf-char-sequence> ; "Jan", case-sensitive
2364               / <x:abnf-char-sequence>"Feb"</x:abnf-char-sequence> ; "Feb", case-sensitive
2365               / <x:abnf-char-sequence>"Mar"</x:abnf-char-sequence> ; "Mar", case-sensitive
2366               / <x:abnf-char-sequence>"Apr"</x:abnf-char-sequence> ; "Apr", case-sensitive
2367               / <x:abnf-char-sequence>"May"</x:abnf-char-sequence> ; "May", case-sensitive
2368               / <x:abnf-char-sequence>"Jun"</x:abnf-char-sequence> ; "Jun", case-sensitive
2369               / <x:abnf-char-sequence>"Jul"</x:abnf-char-sequence> ; "Jul", case-sensitive
2370               / <x:abnf-char-sequence>"Aug"</x:abnf-char-sequence> ; "Aug", case-sensitive
2371               / <x:abnf-char-sequence>"Sep"</x:abnf-char-sequence> ; "Sep", case-sensitive
2372               / <x:abnf-char-sequence>"Oct"</x:abnf-char-sequence> ; "Oct", case-sensitive
2373               / <x:abnf-char-sequence>"Nov"</x:abnf-char-sequence> ; "Nov", case-sensitive
2374               / <x:abnf-char-sequence>"Dec"</x:abnf-char-sequence> ; "Dec", case-sensitive
2375  <x:ref>year</x:ref>         = 4<x:ref>DIGIT</x:ref>
2376
2377  <x:ref>GMT</x:ref>   = <x:abnf-char-sequence>"GMT"</x:abnf-char-sequence> ; "GMT", case-sensitive
2378
2379  <x:ref>time-of-day</x:ref>  = <x:ref>hour</x:ref> ":" <x:ref>minute</x:ref> ":" <x:ref>second</x:ref>
2380                 ; 00:00:00 - 23:59:59
2381                 
2382  <x:ref>hour</x:ref>         = 2<x:ref>DIGIT</x:ref>               
2383  <x:ref>minute</x:ref>       = 2<x:ref>DIGIT</x:ref>               
2384  <x:ref>second</x:ref>       = 2<x:ref>DIGIT</x:ref>               
2385</artwork></figure>
2386<t>
2387  The semantics of <x:ref>day-name</x:ref>, <x:ref>day</x:ref>,
2388  <x:ref>month</x:ref>, <x:ref>year</x:ref>, and <x:ref>time-of-day</x:ref> are the
2389  same as those defined for the RFC 5322 constructs
2390  with the corresponding name (<xref target="RFC5322" x:fmt="," x:sec="3.3"/>).
2391</t>
2392<t anchor="obsolete.date.formats">
2393  <x:anchor-alias value="obs-date"/>
2394  <x:anchor-alias value="rfc850-date"/>
2395  <x:anchor-alias value="asctime-date"/>
2396  <x:anchor-alias value="date1"/>
2397  <x:anchor-alias value="date2"/>
2398  <x:anchor-alias value="date3"/>
2399  <x:anchor-alias value="rfc1123-date"/>
2400  <x:anchor-alias value="day-name-l"/>
2401  Obsolete formats:
2402</t>
2403<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="obs-date"/>
2404  <x:ref>obs-date</x:ref>     = <x:ref>rfc850-date</x:ref> / <x:ref>asctime-date</x:ref> 
2405</artwork></figure>
2406<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="rfc850-date"/>
2407  <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>
2408  <x:ref>date2</x:ref>        = <x:ref>day</x:ref> "-" <x:ref>month</x:ref> "-" 2<x:ref>DIGIT</x:ref>
2409                 ; day-month-year (e.g., 02-Jun-82)
2410
2411  <x:ref>day-name-l</x:ref>   = <x:abnf-char-sequence>"Monday"</x:abnf-char-sequence> ; "Monday", case-sensitive
2412         / <x:abnf-char-sequence>"Tuesday"</x:abnf-char-sequence> ; "Tuesday", case-sensitive
2413         / <x:abnf-char-sequence>"Wednesday"</x:abnf-char-sequence> ; "Wednesday", case-sensitive
2414         / <x:abnf-char-sequence>"Thursday"</x:abnf-char-sequence> ; "Thursday", case-sensitive
2415         / <x:abnf-char-sequence>"Friday"</x:abnf-char-sequence> ; "Friday", case-sensitive
2416         / <x:abnf-char-sequence>"Saturday"</x:abnf-char-sequence> ; "Saturday", case-sensitive
2417         / <x:abnf-char-sequence>"Sunday"</x:abnf-char-sequence> ; "Sunday", case-sensitive
2418</artwork></figure>
2419<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="asctime-date"/>
2420  <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>
2421  <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> ))
2422                 ; month day (e.g., Jun  2)
2423</artwork></figure>
2424<x:note>
2425  <t>
2426    <x:h>Note:</x:h> Recipients of date values are encouraged to be robust in
2427    accepting date values that might have been sent by non-HTTP
2428    applications, as is sometimes the case when retrieving or posting
2429    messages via proxies/gateways to SMTP or NNTP.
2430  </t>
2431</x:note>
2432<x:note>
2433  <t>
2434    <x:h>Note:</x:h> HTTP requirements for the date/time stamp format apply only
2435    to their usage within the protocol stream. Clients and servers are
2436    not required to use these formats for user presentation, request
2437    logging, etc.
2438  </t>
2439</x:note>
2440</section>
2441
2442
2443<section title="Header Field Definitions" anchor="header.field.definitions">
2444<t>
2445   This section defines the syntax and semantics of HTTP/1.1 header fields
2446   related to request and response semantics.
2447</t>
2448
2449<section title="Allow" anchor="header.allow">
2450  <iref primary="true" item="Allow header field" x:for-anchor=""/>
2451  <iref primary="true" item="Header Fields" subitem="Allow" x:for-anchor=""/>
2452  <x:anchor-alias value="Allow"/>
2453<t>
2454   The "Allow" header field lists the set of methods advertised as
2455   supported by the target resource. The purpose of this field is strictly to
2456   inform the recipient of valid request methods associated with the resource.
2457</t>
2458<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/>
2459  <x:ref>Allow</x:ref> = #<x:ref>Method</x:ref>
2460</artwork></figure>
2461<t>
2462   Example of use:
2463</t>
2464<figure><artwork type="example">
2465  Allow: GET, HEAD, PUT
2466</artwork></figure>
2467<t>
2468   The actual set of allowed methods is defined by the origin server at the
2469   time of each request.
2470</t>
2471<t>
2472   A proxy &MUST-NOT; modify the Allow header field &mdash; it does not need to
2473   understand all the methods specified in order to handle them according to
2474   the generic message handling rules.
2475</t>
2476</section>
2477
2478<section title="Date" anchor="header.date">
2479  <iref primary="true" item="Date header field" x:for-anchor=""/>
2480  <iref primary="true" item="Header Fields" subitem="Date" x:for-anchor=""/>
2481  <x:anchor-alias value="Date"/>
2482<t>
2483   The "Date" header field represents the date and time at which
2484   the message was originated, having the same semantics as the Origination
2485   Date Field (orig-date) defined in <xref target="RFC5322" x:fmt="of" x:sec="3.6.1"/>.
2486   The field value is an HTTP-date, as defined in <xref target="http.date"/>;
2487   it &MUST; be sent in rfc1123-date format.
2488</t>
2489<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Date"/>
2490  <x:ref>Date</x:ref> = <x:ref>HTTP-date</x:ref>
2491</artwork></figure>
2492<t>
2493   An example is
2494</t>
2495<figure><artwork type="example">
2496  Date: Tue, 15 Nov 1994 08:12:31 GMT
2497</artwork></figure>
2498<t>
2499   Origin servers &MUST; include a Date header field in all responses,
2500   except in these cases:
2501  <list style="numbers">
2502      <t>If the response status code is 100 (Continue) or 101 (Switching
2503         Protocols), the response &MAY; include a Date header field, at
2504         the server's option.</t>
2505
2506      <t>If the response status code conveys a server error, e.g., 500
2507         (Internal Server Error) or 503 (Service Unavailable), and it is
2508         inconvenient or impossible to generate a valid Date.</t>
2509
2510      <t>If the server does not have a clock that can provide a
2511         reasonable approximation of the current time, its responses
2512         &MUST-NOT; include a Date header field.</t>
2513  </list>
2514</t>
2515<t>
2516   A received message that does not have a Date header field &MUST; be
2517   assigned one by the recipient if the message will be cached by that
2518   recipient.
2519</t>
2520<t>
2521   Clients can use the Date header field as well; in order to keep request
2522   messages small, they are advised not to include it when it doesn't convey
2523   any useful information (as it is usually the case for requests that do not
2524   contain a payload).
2525</t>
2526<t>
2527   The HTTP-date sent in a Date header field &SHOULD-NOT; represent a date and
2528   time subsequent to the generation of the message. It &SHOULD; represent
2529   the best available approximation of the date and time of message
2530   generation, unless the implementation has no means of generating a
2531   reasonably accurate date and time. In theory, the date ought to
2532   represent the moment just before the payload is generated. In
2533   practice, the date can be generated at any time during the message
2534   origination without affecting its semantic value.
2535</t>
2536</section>
2537
2538<section title="Expect" anchor="header.expect">
2539  <iref primary="true" item="Expect header field" x:for-anchor=""/>
2540  <iref primary="true" item="Header Fields" subitem="Expect" x:for-anchor=""/>
2541  <x:anchor-alias value="Expect"/>
2542  <x:anchor-alias value="expectation"/>
2543  <x:anchor-alias value="expectation-extension"/>
2544  <x:anchor-alias value="expect-params"/>
2545<t>
2546   The "Expect" header field is used to indicate that particular
2547   server behaviors are required by the client.
2548</t>
2549<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"/>
2550  <x:ref>Expect</x:ref>       = 1#<x:ref>expectation</x:ref>
2551 
2552  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
2553  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
2554                           *<x:ref>expect-params</x:ref> ]
2555  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
2556</artwork></figure>
2557<t>
2558   A server that does not understand or is unable to comply with any of
2559   the expectation values in the Expect field of a request &MUST; respond
2560   with appropriate error status code. The server &MUST; respond with a 417
2561   (Expectation Failed) status code if any of the expectations cannot be met
2562   or, if there are other problems with the request, some other 4xx
2563   status code.
2564</t>
2565<t>
2566   This header field is defined with extensible syntax to allow for
2567   future extensions. If a server receives a request containing an
2568   Expect field that includes an expectation-extension that it does not
2569   support, it &MUST; respond with a 417 (Expectation Failed) status code.
2570</t>
2571<t>
2572   Comparison of expectation values is case-insensitive for unquoted
2573   tokens (including the 100-continue token), and is case-sensitive for
2574   quoted-string expectation-extensions.
2575</t>
2576<t>
2577   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
2578   return a 417 (Expectation Failed) status code if it receives a request
2579   with an expectation that it cannot meet. However, the Expect
2580   header field itself is end-to-end; it &MUST; be forwarded if the
2581   request is forwarded.
2582</t>
2583<t>
2584   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
2585   Expect header field.
2586</t>
2587<t>
2588   See &use100; for the use of the 100 (Continue) status code.
2589</t>
2590</section>
2591
2592<section title="From" anchor="header.from">
2593  <iref primary="true" item="From header field" x:for-anchor=""/>
2594  <iref primary="true" item="Header Fields" subitem="From" x:for-anchor=""/>
2595  <x:anchor-alias value="From"/>
2596  <x:anchor-alias value="mailbox"/>
2597<t>
2598   The "From" header field, if given, &SHOULD; contain an Internet
2599   e-mail address for the human user who controls the requesting user
2600   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
2601   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
2602</t>
2603<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/>
2604  <x:ref>From</x:ref>    = <x:ref>mailbox</x:ref>
2605 
2606  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2607</artwork></figure>
2608<t>
2609   An example is:
2610</t>
2611<figure><artwork type="example">
2612  From: webmaster@example.org
2613</artwork></figure>
2614<t>
2615   This header field &MAY; be used for logging purposes and as a means for
2616   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2617   be used as an insecure form of access protection. The interpretation
2618   of this field is that the request is being performed on behalf of the
2619   person given, who accepts responsibility for the method performed. In
2620   particular, robot agents &SHOULD; include this header field so that the
2621   person responsible for running the robot can be contacted if problems
2622   occur on the receiving end.
2623</t>
2624<t>
2625   The Internet e-mail address in this field &MAY; be separate from the
2626   Internet host which issued the request. For example, when a request
2627   is passed through a proxy the original issuer's address &SHOULD; be
2628   used.
2629</t>
2630<t>
2631   The client &SHOULD-NOT;  send the From header field without the user's
2632   approval, as it might conflict with the user's privacy interests or
2633   their site's security policy. It is strongly recommended that the
2634   user be able to disable, enable, and modify the value of this field
2635   at any time prior to a request.
2636</t>
2637</section>
2638
2639<section title="Location" anchor="header.location">
2640  <iref primary="true" item="Location header field" x:for-anchor=""/>
2641  <iref primary="true" item="Header Fields" subitem="Location" x:for-anchor=""/>
2642  <x:anchor-alias value="Location"/>
2643<t>
2644   The "Location" header field is used to identify a newly created
2645   resource, or to redirect the recipient to a different location for
2646   completion of the request.
2647</t>
2648<t>
2649   For 201 (Created) responses, the Location is the URI of the new resource
2650   which was created by the request. For 3xx responses, the location &SHOULD;
2651   indicate the server's preferred URI for automatic redirection to the
2652   resource.
2653</t>
2654<t>
2655   The field value consists of a single URI-reference. When it has the form
2656   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2657   the final value is computed by resolving it against the effective request
2658   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
2659</t>
2660<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/>
2661  <x:ref>Location</x:ref> = <x:ref>URI-reference</x:ref>
2662</artwork></figure>
2663<figure>
2664<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical spacing below, it's necessary this way for xml2rfc-->
2665<artwork type="example">
2666  Location: http://www.example.org/pub/WWW/People.html#tim
2667</artwork></figure><figure><artwork type="example">  Location: /index.html
2668</artwork></figure>
2669<t>
2670   There are circumstances in which a fragment identifier in a Location URI
2671   would not be appropriate. For instance, when it appears in a 201 Created
2672   response, where the Location header field specifies the URI for the entire
2673   created resource.
2674</t>
2675<x:note>
2676  <t>
2677    <x:h>Note:</x:h> This specification does not define precedence rules
2678    for the case where the original URI, as navigated to by the user
2679    agent, and the Location header field value both contain fragment
2680    identifiers. Thus be aware that including fragment identifiers might
2681    inconvenience anyone relying on the semantics of the original URI's
2682    fragment identifier.
2683  </t>
2684</x:note>
2685<x:note>
2686  <t>
2687    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2688    from Location in that the Content-Location identifies the most specific
2689    resource corresponding to the enclosed representation.
2690    It is therefore possible for a response to contain header fields for
2691    both Location and Content-Location.
2692  </t>
2693</x:note>
2694</section>
2695
2696<section title="Max-Forwards" anchor="header.max-forwards">
2697  <iref primary="true" item="Max-Forwards header field" x:for-anchor=""/>
2698  <iref primary="true" item="Header Fields" subitem="Max-Forwards" x:for-anchor=""/>
2699  <x:anchor-alias value="Max-Forwards"/>
2700<t>
2701   The "Max-Forwards" header field provides a mechanism with the
2702   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2703   methods to limit the number of times that the request is forwarded by
2704   proxies. This can be useful when the client is attempting to
2705   trace a request which appears to be failing or looping in mid-chain.
2706</t>
2707<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/>
2708  <x:ref>Max-Forwards</x:ref> = 1*<x:ref>DIGIT</x:ref>
2709</artwork></figure>
2710<t>
2711   The Max-Forwards value is a decimal integer indicating the remaining
2712   number of times this request message can be forwarded.
2713</t>
2714<t>
2715   Each recipient of a TRACE or OPTIONS request
2716   containing a Max-Forwards header field &MUST; check and update its
2717   value prior to forwarding the request. If the received value is zero
2718   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2719   respond as the final recipient. If the received Max-Forwards value is
2720   greater than zero, then the forwarded message &MUST; contain an updated
2721   Max-Forwards field with a value decremented by one (1).
2722</t>
2723<t>
2724   The Max-Forwards header field &MAY; be ignored for all other request
2725   methods.
2726</t>
2727</section>
2728
2729<section title="Referer" anchor="header.referer">
2730  <iref primary="true" item="Referer header field" x:for-anchor=""/>
2731  <iref primary="true" item="Header Fields" subitem="Referer" x:for-anchor=""/>
2732  <x:anchor-alias value="Referer"/>
2733<t>
2734   The "Referer" [sic] header field allows the client to specify the
2735   URI of the resource from which the effective request URI was obtained (the
2736   "referrer", although the header field is misspelled.).
2737</t>
2738<t>
2739   The Referer header field allows servers to generate lists of back-links to
2740   resources for interest, logging, optimized caching, etc. It also allows
2741   obsolete or mistyped links to be traced for maintenance. Some servers use
2742   Referer as a means of controlling where they allow links from (so-called
2743   "deep linking"), but legitimate requests do not always
2744   contain a Referer header field.
2745</t>
2746<t>
2747   If the effective request URI was obtained from a source that does not have its own
2748   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
2749   sent with the value "about:blank", or not be sent at all. Note that this
2750   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2751</t>
2752<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/>
2753  <x:ref>Referer</x:ref> = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2754</artwork></figure>
2755<t>
2756   Example:
2757</t>
2758<figure><artwork type="example">
2759  Referer: http://www.example.org/hypertext/Overview.html
2760</artwork></figure>
2761<t>
2762   If the field value is a relative URI, it &SHOULD; be interpreted
2763   relative to the effective request URI. The URI &MUST-NOT; include a fragment. See
2764   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2765</t>
2766</section>
2767
2768<section title="Retry-After" anchor="header.retry-after">
2769  <iref primary="true" item="Retry-After header field" x:for-anchor=""/>
2770  <iref primary="true" item="Header Fields" subitem="Retry-After" x:for-anchor=""/>
2771  <x:anchor-alias value="Retry-After"/>
2772<t>
2773   The header "Retry-After" field can be used with a 503 (Service
2774   Unavailable) response to indicate how long the service is expected to
2775   be unavailable to the requesting client. This field &MAY; also be used
2776   with any 3xx (Redirection) response to indicate the minimum time the
2777   user-agent is asked wait before issuing the redirected request.
2778</t>
2779<t>
2780   The value of this field can be either an HTTP-date or an integer number
2781   of seconds (in decimal) after the time of the response.
2782</t>
2783<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/>
2784  <x:ref>Retry-After</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2785</artwork></figure>
2786<t anchor="rule.delta-seconds">
2787  <x:anchor-alias value="delta-seconds"/>
2788   Time spans are non-negative decimal integers, representing time in
2789   seconds.
2790</t>
2791<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2792  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2793</artwork></figure>
2794<t>
2795   Two examples of its use are
2796</t>
2797<figure><artwork type="example">
2798  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2799  Retry-After: 120
2800</artwork></figure>
2801<t>
2802   In the latter example, the delay is 2 minutes.
2803</t>
2804</section>
2805
2806<section title="Server" anchor="header.server">
2807  <iref primary="true" item="Server header field" x:for-anchor=""/>
2808  <iref primary="true" item="Header Fields" subitem="Server" x:for-anchor=""/>
2809  <x:anchor-alias value="Server"/>
2810<t>
2811   The "Server" header field contains information about the
2812   software used by the origin server to handle the request.
2813</t>
2814<t>
2815   The field can contain multiple product tokens (&product-tokens;) and
2816   comments (&header-fields;) identifying the server and any significant
2817   subproducts. The product tokens are listed in order of their significance
2818   for identifying the application.
2819</t>
2820<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/>
2821  <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> ) )
2822</artwork></figure>
2823<t>
2824   Example:
2825</t>
2826<figure><artwork type="example">
2827  Server: CERN/3.0 libwww/2.17
2828</artwork></figure>
2829<t>
2830   If the response is being forwarded through a proxy, the proxy
2831   application &MUST-NOT; modify the Server header field. Instead, it
2832   &MUST; include a Via field (as described in &header-via;).
2833</t>
2834<x:note>
2835  <t>
2836    <x:h>Note:</x:h> Revealing the specific software version of the server might
2837    allow the server machine to become more vulnerable to attacks
2838    against software that is known to contain security holes. Server
2839    implementors are encouraged to make this field a configurable
2840    option.
2841  </t>
2842</x:note>
2843</section>
2844
2845<section title="User-Agent" anchor="header.user-agent">
2846  <iref primary="true" item="User-Agent header field" x:for-anchor=""/>
2847  <iref primary="true" item="Header Fields" subitem="User-Agent" x:for-anchor=""/>
2848  <x:anchor-alias value="User-Agent"/>
2849<t>
2850   The "User-Agent" header field contains information about the user
2851   agent originating the request. User agents &SHOULD; include this field with
2852   requests.
2853</t>
2854<t>
2855   Typically, it is used for statistical purposes, the tracing of protocol
2856   violations, and tailoring responses to avoid particular user agent
2857   limitations.
2858</t>
2859<t>
2860   The field can contain multiple product tokens (&product-tokens;)
2861   and comments (&header-fields;) identifying the agent and its
2862   significant subproducts. By convention, the product tokens are listed in
2863   order of their significance for identifying the application.
2864</t>
2865<t>
2866   Because this field is usually sent on every request a user agent makes,
2867   implementations are encouraged not to include needlessly fine-grained
2868   detail, and to limit (or even prohibit) the addition of subproducts by third
2869   parties. Overly long and detailed User-Agent field values make requests
2870   larger and can also be used to identify ("fingerprint") the user against
2871   their wishes.
2872</t>
2873<t>
2874   Likewise, implementations are encouraged not to use the product tokens of
2875   other implementations in order to declare compatibility with them, as this
2876   circumvents the purpose of the field. Finally, they are encouraged not to
2877   use comments to identify products; doing so makes the field value more
2878   difficult to parse.
2879</t>
2880<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/>
2881  <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> ) )
2882</artwork></figure>
2883<t>
2884   Example:
2885</t>
2886<figure><artwork type="example">
2887  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2888</artwork></figure>
2889</section>
2890
2891</section>
2892
2893<section title="IANA Considerations" anchor="IANA.considerations">
2894
2895<section title="Method Registry" anchor="method.registration">
2896<t>
2897  The registration procedure for HTTP request methods is defined by
2898  <xref target="method.registry"/> of this document.
2899</t>
2900<t>
2901   The HTTP Method Registry shall be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2902   and be populated with the registrations below:
2903</t>
2904<?BEGININC p2-semantics.iana-methods ?>
2905<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2906<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2907   <ttcol>Method</ttcol>
2908   <ttcol>Safe</ttcol>
2909   <ttcol>Reference</ttcol>
2910   <c>CONNECT</c>
2911   <c>no</c>
2912   <c>
2913      <xref target="CONNECT"/>
2914   </c>
2915   <c>DELETE</c>
2916   <c>no</c>
2917   <c>
2918      <xref target="DELETE"/>
2919   </c>
2920   <c>GET</c>
2921   <c>yes</c>
2922   <c>
2923      <xref target="GET"/>
2924   </c>
2925   <c>HEAD</c>
2926   <c>yes</c>
2927   <c>
2928      <xref target="HEAD"/>
2929   </c>
2930   <c>OPTIONS</c>
2931   <c>yes</c>
2932   <c>
2933      <xref target="OPTIONS"/>
2934   </c>
2935   <c>POST</c>
2936   <c>no</c>
2937   <c>
2938      <xref target="POST"/>
2939   </c>
2940   <c>PUT</c>
2941   <c>no</c>
2942   <c>
2943      <xref target="PUT"/>
2944   </c>
2945   <c>TRACE</c>
2946   <c>yes</c>
2947   <c>
2948      <xref target="TRACE"/>
2949   </c>
2950</texttable>
2951<!--(END)-->
2952<?ENDINC p2-semantics.iana-methods ?>
2953</section>
2954
2955<section title="Status Code Registry" anchor="status.code.registration">
2956<t>
2957   The registration procedure for HTTP Status Codes &mdash; previously defined
2958   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> &mdash; is now defined
2959   by <xref target="status.code.registry"/> of this document.
2960</t>
2961<t>
2962   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2963   shall be updated with the registrations below:
2964</t>
2965<?BEGININC p2-semantics.iana-status-codes ?>
2966<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2967<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2968   <ttcol>Value</ttcol>
2969   <ttcol>Description</ttcol>
2970   <ttcol>Reference</ttcol>
2971   <c>100</c>
2972   <c>Continue</c>
2973   <c>
2974      <xref target="status.100"/>
2975   </c>
2976   <c>101</c>
2977   <c>Switching Protocols</c>
2978   <c>
2979      <xref target="status.101"/>
2980   </c>
2981   <c>200</c>
2982   <c>OK</c>
2983   <c>
2984      <xref target="status.200"/>
2985   </c>
2986   <c>201</c>
2987   <c>Created</c>
2988   <c>
2989      <xref target="status.201"/>
2990   </c>
2991   <c>202</c>
2992   <c>Accepted</c>
2993   <c>
2994      <xref target="status.202"/>
2995   </c>
2996   <c>203</c>
2997   <c>Non-Authoritative Information</c>
2998   <c>
2999      <xref target="status.203"/>
3000   </c>
3001   <c>204</c>
3002   <c>No Content</c>
3003   <c>
3004      <xref target="status.204"/>
3005   </c>
3006   <c>205</c>
3007   <c>Reset Content</c>
3008   <c>
3009      <xref target="status.205"/>
3010   </c>
3011   <c>300</c>
3012   <c>Multiple Choices</c>
3013   <c>
3014      <xref target="status.300"/>
3015   </c>
3016   <c>301</c>
3017   <c>Moved Permanently</c>
3018   <c>
3019      <xref target="status.301"/>
3020   </c>
3021   <c>302</c>
3022   <c>Found</c>
3023   <c>
3024      <xref target="status.302"/>
3025   </c>
3026   <c>303</c>
3027   <c>See Other</c>
3028   <c>
3029      <xref target="status.303"/>
3030   </c>
3031   <c>305</c>
3032   <c>Use Proxy</c>
3033   <c>
3034      <xref target="status.305"/>
3035   </c>
3036   <c>306</c>
3037   <c>(Unused)</c>
3038   <c>
3039      <xref target="status.306"/>
3040   </c>
3041   <c>307</c>
3042   <c>Temporary Redirect</c>
3043   <c>
3044      <xref target="status.307"/>
3045   </c>
3046   <c>400</c>
3047   <c>Bad Request</c>
3048   <c>
3049      <xref target="status.400"/>
3050   </c>
3051   <c>402</c>
3052   <c>Payment Required</c>
3053   <c>
3054      <xref target="status.402"/>
3055   </c>
3056   <c>403</c>
3057   <c>Forbidden</c>
3058   <c>
3059      <xref target="status.403"/>
3060   </c>
3061   <c>404</c>
3062   <c>Not Found</c>
3063   <c>
3064      <xref target="status.404"/>
3065   </c>
3066   <c>405</c>
3067   <c>Method Not Allowed</c>
3068   <c>
3069      <xref target="status.405"/>
3070   </c>
3071   <c>406</c>
3072   <c>Not Acceptable</c>
3073   <c>
3074      <xref target="status.406"/>
3075   </c>
3076   <c>407</c>
3077   <c>Proxy Authentication Required</c>
3078   <c>
3079      <xref target="status.407"/>
3080   </c>
3081   <c>408</c>
3082   <c>Request Timeout</c>
3083   <c>
3084      <xref target="status.408"/>
3085   </c>
3086   <c>409</c>
3087   <c>Conflict</c>
3088   <c>
3089      <xref target="status.409"/>
3090   </c>
3091   <c>410</c>
3092   <c>Gone</c>
3093   <c>
3094      <xref target="status.410"/>
3095   </c>
3096   <c>411</c>
3097   <c>Length Required</c>
3098   <c>
3099      <xref target="status.411"/>
3100   </c>
3101   <c>413</c>
3102   <c>Request Representation Too Large</c>
3103   <c>
3104      <xref target="status.413"/>
3105   </c>
3106   <c>414</c>
3107   <c>URI Too Long</c>
3108   <c>
3109      <xref target="status.414"/>
3110   </c>
3111   <c>415</c>
3112   <c>Unsupported Media Type</c>
3113   <c>
3114      <xref target="status.415"/>
3115   </c>
3116   <c>417</c>
3117   <c>Expectation Failed</c>
3118   <c>
3119      <xref target="status.417"/>
3120   </c>
3121   <c>426</c>
3122   <c>Upgrade Required</c>
3123   <c>
3124      <xref target="status.426"/>
3125   </c>
3126   <c>500</c>
3127   <c>Internal Server Error</c>
3128   <c>
3129      <xref target="status.500"/>
3130   </c>
3131   <c>501</c>
3132   <c>Not Implemented</c>
3133   <c>
3134      <xref target="status.501"/>
3135   </c>
3136   <c>502</c>
3137   <c>Bad Gateway</c>
3138   <c>
3139      <xref target="status.502"/>
3140   </c>
3141   <c>503</c>
3142   <c>Service Unavailable</c>
3143   <c>
3144      <xref target="status.503"/>
3145   </c>
3146   <c>504</c>
3147   <c>Gateway Timeout</c>
3148   <c>
3149      <xref target="status.504"/>
3150   </c>
3151   <c>505</c>
3152   <c>HTTP Version Not Supported</c>
3153   <c>
3154      <xref target="status.505"/>
3155   </c>
3156</texttable>
3157<!--(END)-->
3158<?ENDINC p2-semantics.iana-status-codes ?>
3159</section>
3160<section title="Header Field Registration" anchor="header.field.registration">
3161<t>
3162   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
3163   with the permanent registrations below (see <xref target="RFC3864"/>):
3164</t>
3165<?BEGININC p2-semantics.iana-headers ?>
3166<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
3167<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
3168   <ttcol>Header Field Name</ttcol>
3169   <ttcol>Protocol</ttcol>
3170   <ttcol>Status</ttcol>
3171   <ttcol>Reference</ttcol>
3172
3173   <c>Allow</c>
3174   <c>http</c>
3175   <c>standard</c>
3176   <c>
3177      <xref target="header.allow"/>
3178   </c>
3179   <c>Date</c>
3180   <c>http</c>
3181   <c>standard</c>
3182   <c>
3183      <xref target="header.date"/>
3184   </c>
3185   <c>Expect</c>
3186   <c>http</c>
3187   <c>standard</c>
3188   <c>
3189      <xref target="header.expect"/>
3190   </c>
3191   <c>From</c>
3192   <c>http</c>
3193   <c>standard</c>
3194   <c>
3195      <xref target="header.from"/>
3196   </c>
3197   <c>Location</c>
3198   <c>http</c>
3199   <c>standard</c>
3200   <c>
3201      <xref target="header.location"/>
3202   </c>
3203   <c>Max-Forwards</c>
3204   <c>http</c>
3205   <c>standard</c>
3206   <c>
3207      <xref target="header.max-forwards"/>
3208   </c>
3209   <c>Referer</c>
3210   <c>http</c>
3211   <c>standard</c>
3212   <c>
3213      <xref target="header.referer"/>
3214   </c>
3215   <c>Retry-After</c>
3216   <c>http</c>
3217   <c>standard</c>
3218   <c>
3219      <xref target="header.retry-after"/>
3220   </c>
3221   <c>Server</c>
3222   <c>http</c>
3223   <c>standard</c>
3224   <c>
3225      <xref target="header.server"/>
3226   </c>
3227   <c>User-Agent</c>
3228   <c>http</c>
3229   <c>standard</c>
3230   <c>
3231      <xref target="header.user-agent"/>
3232   </c>
3233</texttable>
3234<!--(END)-->
3235<?ENDINC p2-semantics.iana-headers ?>
3236<t>
3237   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
3238</t>
3239</section>
3240</section>
3241
3242<section title="Security Considerations" anchor="security.considerations">
3243<t>
3244   This section is meant to inform application developers, information
3245   providers, and users of the security limitations in HTTP/1.1 as
3246   described by this document. The discussion does not include
3247   definitive solutions to the problems revealed, though it does make
3248   some suggestions for reducing security risks.
3249</t>
3250
3251<section title="Transfer of Sensitive Information" anchor="security.sensitive">
3252<t>
3253   Like any generic data transfer protocol, HTTP cannot regulate the
3254   content of the data that is transferred, nor is there any a priori
3255   method of determining the sensitivity of any particular piece of
3256   information within the context of any given request. Therefore,
3257   applications &SHOULD; supply as much control over this information as
3258   possible to the provider of that information. Four header fields are
3259   worth special mention in this context: Server, Via, Referer and From.
3260</t>
3261<t>
3262   Revealing the specific software version of the server might allow the
3263   server machine to become more vulnerable to attacks against software
3264   that is known to contain security holes. Implementors &SHOULD; make the
3265   Server header field a configurable option.
3266</t>
3267<t>
3268   Proxies which serve as a portal through a network firewall &SHOULD;
3269   take special precautions regarding the transfer of header information
3270   that identifies the hosts behind the firewall. In particular, they
3271   &SHOULD; remove, or replace with sanitized versions, any Via fields
3272   generated behind the firewall.
3273</t>
3274<t>
3275   The Referer header field allows reading patterns to be studied and reverse
3276   links drawn. Although it can be very useful, its power can be abused
3277   if user details are not separated from the information contained in
3278   the Referer. Even when the personal information has been removed, the
3279   Referer header field might indicate a private document's URI whose
3280   publication would be inappropriate.
3281</t>
3282<t>
3283   The information sent in the From field might conflict with the user's
3284   privacy interests or their site's security policy, and hence it
3285   &SHOULD-NOT;  be transmitted without the user being able to disable,
3286   enable, and modify the contents of the field. The user &MUST; be able
3287   to set the contents of this field within a user preference or
3288   application defaults configuration.
3289</t>
3290<t>
3291   We suggest, though do not require, that a convenient toggle interface
3292   be provided for the user to enable or disable the sending of From and
3293   Referer information.
3294</t>
3295<t>
3296   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref
3297   target="header.server"/>) header fields can sometimes be used to determine
3298   that a specific client or server have a particular security hole which might
3299   be exploited. Unfortunately, this same information is often used for other
3300   valuable purposes for which HTTP currently has no better mechanism.
3301</t>
3302<t>
3303   Furthermore, the User-Agent header field may contain enough entropy to be
3304   used, possibly in conjunction with other material, to uniquely identify the
3305   user.
3306</t>
3307<t>
3308   Some request methods, like TRACE (<xref target="TRACE"/>), expose information
3309   that was sent in request header fields within the body of their response.
3310   Clients &SHOULD; be careful with sensitive information, like Cookies,
3311   Authorization credentials, and other header fields that might be used to
3312   collect data from the client.
3313</t> 
3314</section>
3315
3316<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
3317<t>
3318   Because the source of a link might be private information or might
3319   reveal an otherwise private information source, it is strongly
3320   recommended that the user be able to select whether or not the
3321   Referer field is sent. For example, a browser client could have a
3322   toggle switch for browsing openly/anonymously, which would
3323   respectively enable/disable the sending of Referer and From
3324   information.
3325</t>
3326<t>
3327   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
3328   HTTP request if the referring page was transferred with a secure
3329   protocol.
3330</t>
3331<t>
3332   Authors of services &SHOULD-NOT; use GET-based forms for the submission of
3333   sensitive data because that data will be placed in the request-target. Many
3334   existing servers, proxies, and user agents log or display the request-target
3335   in places where it might be visible to third parties. Such services can
3336   use POST-based form submission instead.
3337</t>
3338</section>
3339
3340<section title="Location Headers and Spoofing" anchor="location.spoofing">
3341<t>
3342   If a single server supports multiple organizations that do not trust
3343   one another, then it &MUST; check the values of Location and Content-Location
3344   header fields in responses that are generated under control of
3345   said organizations to make sure that they do not attempt to
3346   invalidate resources over which they have no authority.
3347</t>
3348</section>
3349
3350<section title="Security Considerations for CONNECT">
3351<t>
3352   Since tunneled data is opaque to the proxy, there are additional
3353   risks to tunneling to other well-known or reserved ports.
3354   A HTTP client CONNECTing to port 25 could relay spam
3355   via SMTP, for example. As such, proxies &SHOULD; restrict CONNECT
3356   access to a small number of known ports.
3357</t>
3358</section>
3359
3360</section>
3361
3362<section title="Acknowledgments" anchor="acks">
3363<t>
3364  See &acks;.
3365</t>
3366</section>
3367</middle>
3368<back>
3369
3370<references title="Normative References">
3371
3372<reference anchor="Part1">
3373  <front>
3374    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
3375    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3376      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3377      <address><email>fielding@gbiv.com</email></address>
3378    </author>
3379    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3380      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3381      <address><email>jg@freedesktop.org</email></address>
3382    </author>
3383    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3384      <organization abbrev="HP">Hewlett-Packard Company</organization>
3385      <address><email>JeffMogul@acm.org</email></address>
3386    </author>
3387    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3388      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3389      <address><email>henrikn@microsoft.com</email></address>
3390    </author>
3391    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3392      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3393      <address><email>LMM@acm.org</email></address>
3394    </author>
3395    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3396      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3397      <address><email>paulle@microsoft.com</email></address>
3398    </author>
3399    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3400      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3401      <address><email>timbl@w3.org</email></address>
3402    </author>
3403    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3404      <organization abbrev="W3C">World Wide Web Consortium</organization>
3405      <address><email>ylafon@w3.org</email></address>
3406    </author>
3407    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3408      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3409      <address><email>julian.reschke@greenbytes.de</email></address>
3410    </author>
3411    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3412  </front>
3413  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
3414  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
3415</reference>
3416
3417<reference anchor="Part3">
3418  <front>
3419    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
3420    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3421      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3422      <address><email>fielding@gbiv.com</email></address>
3423    </author>
3424    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3425      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3426      <address><email>jg@freedesktop.org</email></address>
3427    </author>
3428    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3429      <organization abbrev="HP">Hewlett-Packard Company</organization>
3430      <address><email>JeffMogul@acm.org</email></address>
3431    </author>
3432    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3433      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3434      <address><email>henrikn@microsoft.com</email></address>
3435    </author>
3436    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3437      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3438      <address><email>LMM@acm.org</email></address>
3439    </author>
3440    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3441      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3442      <address><email>paulle@microsoft.com</email></address>
3443    </author>
3444    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3445      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3446      <address><email>timbl@w3.org</email></address>
3447    </author>
3448    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3449      <organization abbrev="W3C">World Wide Web Consortium</organization>
3450      <address><email>ylafon@w3.org</email></address>
3451    </author>
3452    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3453      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3454      <address><email>julian.reschke@greenbytes.de</email></address>
3455    </author>
3456    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3457  </front>
3458  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
3459  <x:source href="p3-payload.xml" basename="p3-payload"/>
3460</reference>
3461
3462<reference anchor="Part4">
3463  <front>
3464    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
3465    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3466      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3467      <address><email>fielding@gbiv.com</email></address>
3468    </author>
3469    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3470      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3471      <address><email>jg@freedesktop.org</email></address>
3472    </author>
3473    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3474      <organization abbrev="HP">Hewlett-Packard Company</organization>
3475      <address><email>JeffMogul@acm.org</email></address>
3476    </author>
3477    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3478      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3479      <address><email>henrikn@microsoft.com</email></address>
3480    </author>
3481    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3482      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3483      <address><email>LMM@acm.org</email></address>
3484    </author>
3485    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3486      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3487      <address><email>paulle@microsoft.com</email></address>
3488    </author>
3489    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3490      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3491      <address><email>timbl@w3.org</email></address>
3492    </author>
3493    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3494      <organization abbrev="W3C">World Wide Web Consortium</organization>
3495      <address><email>ylafon@w3.org</email></address>
3496    </author>
3497    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3498      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3499      <address><email>julian.reschke@greenbytes.de</email></address>
3500    </author>
3501    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3502  </front>
3503  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
3504  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
3505</reference>
3506
3507<reference anchor="Part5">
3508  <front>
3509    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
3510    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3511      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3512      <address><email>fielding@gbiv.com</email></address>
3513    </author>
3514    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3515      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3516      <address><email>jg@freedesktop.org</email></address>
3517    </author>
3518    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3519      <organization abbrev="HP">Hewlett-Packard Company</organization>
3520      <address><email>JeffMogul@acm.org</email></address>
3521    </author>
3522    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3523      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3524      <address><email>henrikn@microsoft.com</email></address>
3525    </author>
3526    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3527      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3528      <address><email>LMM@acm.org</email></address>
3529    </author>
3530    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3531      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3532      <address><email>paulle@microsoft.com</email></address>
3533    </author>
3534    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3535      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3536      <address><email>timbl@w3.org</email></address>
3537    </author>
3538    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3539      <organization abbrev="W3C">World Wide Web Consortium</organization>
3540      <address><email>ylafon@w3.org</email></address>
3541    </author>
3542    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3543      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3544      <address><email>julian.reschke@greenbytes.de</email></address>
3545    </author>
3546    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3547  </front>
3548  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
3549  <x:source href="p5-range.xml" basename="p5-range"/>
3550</reference>
3551
3552<reference anchor="Part6">
3553  <front>
3554    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
3555    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3556      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3557      <address><email>fielding@gbiv.com</email></address>
3558    </author>
3559    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3560      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3561      <address><email>jg@freedesktop.org</email></address>
3562    </author>
3563    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3564      <organization abbrev="HP">Hewlett-Packard Company</organization>
3565      <address><email>JeffMogul@acm.org</email></address>
3566    </author>
3567    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3568      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3569      <address><email>henrikn@microsoft.com</email></address>
3570    </author>
3571    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3572      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3573      <address><email>LMM@acm.org</email></address>
3574    </author>
3575    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3576      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3577      <address><email>paulle@microsoft.com</email></address>
3578    </author>
3579    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3580      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3581      <address><email>timbl@w3.org</email></address>
3582    </author>
3583    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3584      <organization abbrev="W3C">World Wide Web Consortium</organization>
3585      <address><email>ylafon@w3.org</email></address>
3586    </author>
3587    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
3588      <organization>Rackspace</organization>
3589      <address><email>mnot@mnot.net</email></address>
3590    </author>
3591    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3592      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3593      <address><email>julian.reschke@greenbytes.de</email></address>
3594    </author>
3595    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3596  </front>
3597  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
3598  <x:source href="p6-cache.xml" basename="p6-cache"/>
3599</reference>
3600
3601<reference anchor="Part7">
3602  <front>
3603    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
3604    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3605      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3606      <address><email>fielding@gbiv.com</email></address>
3607    </author>
3608    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3609      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3610      <address><email>jg@freedesktop.org</email></address>
3611    </author>
3612    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3613      <organization abbrev="HP">Hewlett-Packard Company</organization>
3614      <address><email>JeffMogul@acm.org</email></address>
3615    </author>
3616    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3617      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3618      <address><email>henrikn@microsoft.com</email></address>
3619    </author>
3620    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3621      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3622      <address><email>LMM@acm.org</email></address>
3623    </author>
3624    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3625      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3626      <address><email>paulle@microsoft.com</email></address>
3627    </author>
3628    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3629      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3630      <address><email>timbl@w3.org</email></address>
3631    </author>
3632    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3633      <organization abbrev="W3C">World Wide Web Consortium</organization>
3634      <address><email>ylafon@w3.org</email></address>
3635    </author>
3636    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3637      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3638      <address><email>julian.reschke@greenbytes.de</email></address>
3639    </author>
3640    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3641  </front>
3642  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3643  <x:source href="p7-auth.xml" basename="p7-auth"/>
3644</reference>
3645
3646<reference anchor="RFC2119">
3647  <front>
3648    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3649    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3650      <organization>Harvard University</organization>
3651      <address><email>sob@harvard.edu</email></address>
3652    </author>
3653    <date month="March" year="1997"/>
3654  </front>
3655  <seriesInfo name="BCP" value="14"/>
3656  <seriesInfo name="RFC" value="2119"/>
3657</reference>
3658
3659<reference anchor="RFC3986">
3660 <front>
3661  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3662  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3663    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3664    <address>
3665       <email>timbl@w3.org</email>
3666       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3667    </address>
3668  </author>
3669  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3670    <organization abbrev="Day Software">Day Software</organization>
3671    <address>
3672      <email>fielding@gbiv.com</email>
3673      <uri>http://roy.gbiv.com/</uri>
3674    </address>
3675  </author>
3676  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3677    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3678    <address>
3679      <email>LMM@acm.org</email>
3680      <uri>http://larry.masinter.net/</uri>
3681    </address>
3682  </author>
3683  <date month='January' year='2005'></date>
3684 </front>
3685 <seriesInfo name="STD" value="66"/>
3686 <seriesInfo name="RFC" value="3986"/>
3687</reference>
3688
3689<reference anchor="RFC5234">
3690  <front>
3691    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3692    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3693      <organization>Brandenburg InternetWorking</organization>
3694      <address>
3695        <email>dcrocker@bbiw.net</email>
3696      </address> 
3697    </author>
3698    <author initials="P." surname="Overell" fullname="Paul Overell">
3699      <organization>THUS plc.</organization>
3700      <address>
3701        <email>paul.overell@thus.net</email>
3702      </address>
3703    </author>
3704    <date month="January" year="2008"/>
3705  </front>
3706  <seriesInfo name="STD" value="68"/>
3707  <seriesInfo name="RFC" value="5234"/>
3708</reference>
3709
3710</references>
3711
3712<references title="Informative References">
3713
3714<reference anchor="RFC1123">
3715  <front>
3716    <title>Requirements for Internet Hosts - Application and Support</title>
3717    <author initials="R." surname="Braden" fullname="Robert Braden">
3718      <organization>University of Southern California (USC), Information Sciences Institute</organization>
3719      <address><email>Braden@ISI.EDU</email></address>
3720    </author>
3721    <date month="October" year="1989"/>
3722  </front>
3723  <seriesInfo name="STD" value="3"/>
3724  <seriesInfo name="RFC" value="1123"/>
3725</reference>
3726
3727<reference anchor="RFC1945">
3728  <front>
3729    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3730    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3731      <organization>MIT, Laboratory for Computer Science</organization>
3732      <address><email>timbl@w3.org</email></address>
3733    </author>
3734    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3735      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3736      <address><email>fielding@ics.uci.edu</email></address>
3737    </author>
3738    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3739      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3740      <address><email>frystyk@w3.org</email></address>
3741    </author>
3742    <date month="May" year="1996"/>
3743  </front>
3744  <seriesInfo name="RFC" value="1945"/>
3745</reference>
3746
3747<reference anchor="RFC2068">
3748  <front>
3749    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3750    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3751      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3752      <address><email>fielding@ics.uci.edu</email></address>
3753    </author>
3754    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3755      <organization>MIT Laboratory for Computer Science</organization>
3756      <address><email>jg@w3.org</email></address>
3757    </author>
3758    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3759      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3760      <address><email>mogul@wrl.dec.com</email></address>
3761    </author>
3762    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3763      <organization>MIT Laboratory for Computer Science</organization>
3764      <address><email>frystyk@w3.org</email></address>
3765    </author>
3766    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3767      <organization>MIT Laboratory for Computer Science</organization>
3768      <address><email>timbl@w3.org</email></address>
3769    </author>
3770    <date month="January" year="1997"/>
3771  </front>
3772  <seriesInfo name="RFC" value="2068"/>
3773</reference>
3774
3775<reference anchor="RFC2616">
3776  <front>
3777    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3778    <author initials="R." surname="Fielding" fullname="R. Fielding">
3779      <organization>University of California, Irvine</organization>
3780      <address><email>fielding@ics.uci.edu</email></address>
3781    </author>
3782    <author initials="J." surname="Gettys" fullname="J. Gettys">
3783      <organization>W3C</organization>
3784      <address><email>jg@w3.org</email></address>
3785    </author>
3786    <author initials="J." surname="Mogul" fullname="J. Mogul">
3787      <organization>Compaq Computer Corporation</organization>
3788      <address><email>mogul@wrl.dec.com</email></address>
3789    </author>
3790    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3791      <organization>MIT Laboratory for Computer Science</organization>
3792      <address><email>frystyk@w3.org</email></address>
3793    </author>
3794    <author initials="L." surname="Masinter" fullname="L. Masinter">
3795      <organization>Xerox Corporation</organization>
3796      <address><email>masinter@parc.xerox.com</email></address>
3797    </author>
3798    <author initials="P." surname="Leach" fullname="P. Leach">
3799      <organization>Microsoft Corporation</organization>
3800      <address><email>paulle@microsoft.com</email></address>
3801    </author>
3802    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3803      <organization>W3C</organization>
3804      <address><email>timbl@w3.org</email></address>
3805    </author>
3806    <date month="June" year="1999"/>
3807  </front>
3808  <seriesInfo name="RFC" value="2616"/>
3809</reference>
3810
3811<reference anchor='RFC2817'>
3812  <front>
3813    <title>Upgrading to TLS Within HTTP/1.1</title>
3814    <author initials='R.' surname='Khare' fullname='R. Khare'>
3815      <organization>4K Associates / UC Irvine</organization>
3816      <address><email>rohit@4K-associates.com</email></address>
3817    </author>
3818    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3819      <organization>Agranat Systems, Inc.</organization>
3820      <address><email>lawrence@agranat.com</email></address>
3821    </author>
3822    <date year='2000' month='May' />
3823  </front>
3824  <seriesInfo name='RFC' value='2817' />
3825</reference>
3826
3827<reference anchor='RFC3864'>
3828  <front>
3829    <title>Registration Procedures for Message Header Fields</title>
3830    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3831      <organization>Nine by Nine</organization>
3832      <address><email>GK-IETF@ninebynine.org</email></address>
3833    </author>
3834    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3835      <organization>BEA Systems</organization>
3836      <address><email>mnot@pobox.com</email></address>
3837    </author>
3838    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3839      <organization>HP Labs</organization>
3840      <address><email>JeffMogul@acm.org</email></address>
3841    </author>
3842    <date year='2004' month='September' />
3843  </front>
3844  <seriesInfo name='BCP' value='90' />
3845  <seriesInfo name='RFC' value='3864' />
3846</reference>
3847
3848<reference anchor='RFC5226'>
3849  <front>
3850    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3851    <author initials='T.' surname='Narten' fullname='T. Narten'>
3852      <organization>IBM</organization>
3853      <address><email>narten@us.ibm.com</email></address>
3854    </author>
3855    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3856      <organization>Google</organization>
3857      <address><email>Harald@Alvestrand.no</email></address>
3858    </author>
3859    <date year='2008' month='May' />
3860  </front>
3861  <seriesInfo name='BCP' value='26' />
3862  <seriesInfo name='RFC' value='5226' />
3863</reference>
3864
3865<reference anchor="RFC5322">
3866  <front>
3867    <title>Internet Message Format</title>
3868    <author initials="P." surname="Resnick" fullname="P. Resnick">
3869      <organization>Qualcomm Incorporated</organization>
3870    </author>
3871    <date year="2008" month="October"/>
3872  </front> 
3873  <seriesInfo name="RFC" value="5322"/>
3874</reference>
3875
3876<reference anchor='RFC5789'>
3877  <front>
3878    <title>PATCH Method for HTTP</title>
3879    <author initials='L.' surname='Dusseault' fullname='L. Dusseault'>
3880      <organization>Linden Lab</organization>
3881    </author>
3882    <author initials='J.' surname='Snell' fullname='J. Snell' />
3883    <date year='2010' month='March' />
3884  </front>
3885  <seriesInfo name='RFC' value='5789' />
3886</reference>
3887
3888<reference anchor="RFC5987">
3889        <front>
3890    <title>Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters</title>
3891    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke">
3892      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3893      <address>
3894        <postal>
3895          <street>Hafenweg 16</street>
3896          <city>Muenster</city><region>NW</region><code>48155</code>
3897          <country>Germany</country>
3898        </postal>
3899        <email>julian.reschke@greenbytes.de</email>     
3900        <uri>http://greenbytes.de/tech/webdav/</uri>   
3901      </address>
3902    </author>
3903    <date month="August" year="2010"/>
3904  </front>
3905  <seriesInfo name="RFC" value="5987"/>
3906</reference>
3907
3908</references>
3909
3910<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3911<t>
3912  This document takes over the Status Code Registry, previously defined
3913  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3914  (<xref target="status.code.registry"/>)
3915</t>
3916<t>
3917  Clarify definition of POST.
3918  (<xref target="POST"/>)
3919</t>
3920<t>
3921  Remove requirement to handle all Content-* header fields; ban use of
3922  Content-Range with PUT.
3923  (<xref target="PUT"/>)
3924</t>
3925<t>
3926  Take over definition of CONNECT method from <xref target="RFC2817"/>.
3927  (<xref target="CONNECT"/>)
3928</t>
3929<t>
3930  Broadened the definition of 203 (Non-Authoritative Information) to include
3931  cases of payload transformations as well.
3932  (<xref target="status.203"/>)
3933</t>
3934<t>
3935  Failed to consider that there are many other request methods that are safe
3936  to automatically redirect, and further that the user agent is able to make
3937  that determination based on the request method semantics.
3938  Furthermore, allow user agents to rewrite the method from POST to GET
3939  for status codes 301 and 302.
3940  (Sections <xref format="counter" target="status.301"/>,
3941  <xref format="counter" target="status.302"/> and
3942  <xref format="counter" target="status.307"/>)
3943</t>
3944<t>
3945  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3946  It used to indicate that the target resource must be accessed through the
3947  proxy given by the Location field. The Location field gave the URI of the
3948  proxy. The recipient was expected to repeat this single request via the proxy.
3949  (<xref target="status.305"/>)
3950</t>
3951<t>
3952  Define status 426 (Upgrade Required) (this was incorporated from
3953  <xref target="RFC2817"/>).
3954  (<xref target="status.426"/>)
3955</t>
3956<t>
3957  Change ABNF productions for header fields to only define the field value.
3958  (<xref target="header.field.definitions"/>)
3959</t>
3960<t>
3961  Reclassify "Allow" as response header field, removing the option to
3962  specify it in a PUT request.
3963  Relax the server requirement on the contents of the Allow header field and
3964  remove requirement on clients to always trust the header field value.
3965  (<xref target="header.allow"/>)
3966</t>
3967<t>
3968  Correct syntax of Location header field to allow URI references (including
3969  relative references and fragments), as referred symbol "absoluteURI" wasn't
3970  what was expected, and add some clarifications as to when use of fragments
3971  would not be appropriate.
3972  (<xref target="header.location"/>)
3973</t>
3974<t>
3975  Restrict Max-Forwards header field to OPTIONS and TRACE (previously,
3976  extension methods could have used it as well).
3977  (<xref target="header.max-forwards"/>)
3978</t>
3979<t>
3980  Allow Referer field value of "about:blank" as alternative to not specifying it.
3981  (<xref target="header.referer"/>)
3982</t>
3983<t>
3984  In the description of the Server header field, the Via field
3985  was described as a SHOULD. The requirement was and is stated
3986  correctly in the description of the Via header field in &header-via;.
3987  (<xref target="header.server"/>)
3988</t>
3989</section>
3990
3991<?BEGININC p2-semantics.abnf-appendix ?>
3992<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3993<figure>
3994<artwork type="abnf" name="p2-semantics.parsed-abnf">
3995<x:ref>Allow</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3996
3997<x:ref>Date</x:ref> = HTTP-date
3998
3999<x:ref>Expect</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
4000
4001<x:ref>From</x:ref> = mailbox
4002
4003<x:ref>GMT</x:ref> = %x47.4D.54 ; GMT
4004
4005<x:ref>HTTP-date</x:ref> = rfc1123-date / obs-date
4006
4007<x:ref>Location</x:ref> = URI-reference
4008
4009<x:ref>Max-Forwards</x:ref> = 1*DIGIT
4010<x:ref>Method</x:ref> = token
4011
4012<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
4013
4014<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
4015<x:ref>Reason-Phrase</x:ref> = *( HTAB / SP / VCHAR / obs-text )
4016<x:ref>Referer</x:ref> = absolute-URI / partial-URI
4017<x:ref>Retry-After</x:ref> = HTTP-date / delta-seconds
4018
4019<x:ref>Server</x:ref> = product *( RWS ( product / comment ) )
4020<x:ref>Status-Code</x:ref> = 3DIGIT
4021
4022<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.7&gt;
4023<x:ref>User-Agent</x:ref> = product *( RWS ( product / comment ) )
4024
4025<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.7&gt;
4026<x:ref>asctime-date</x:ref> = day-name SP date3 SP time-of-day SP year
4027
4028<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2&gt;
4029
4030<x:ref>date1</x:ref> = day SP month SP year
4031<x:ref>date2</x:ref> = day "-" month "-" 2DIGIT
4032<x:ref>date3</x:ref> = month SP ( 2DIGIT / ( SP DIGIT ) )
4033<x:ref>day</x:ref> = 2DIGIT
4034<x:ref>day-name</x:ref> = %x4D.6F.6E ; Mon
4035 / %x54.75.65 ; Tue
4036 / %x57.65.64 ; Wed
4037 / %x54.68.75 ; Thu
4038 / %x46.72.69 ; Fri
4039 / %x53.61.74 ; Sat
4040 / %x53.75.6E ; Sun
4041<x:ref>day-name-l</x:ref> = %x4D.6F.6E.64.61.79 ; Monday
4042 / %x54.75.65.73.64.61.79 ; Tuesday
4043 / %x57.65.64.6E.65.73.64.61.79 ; Wednesday
4044 / %x54.68.75.72.73.64.61.79 ; Thursday
4045 / %x46.72.69.64.61.79 ; Friday
4046 / %x53.61.74.75.72.64.61.79 ; Saturday
4047 / %x53.75.6E.64.61.79 ; Sunday
4048<x:ref>delta-seconds</x:ref> = 1*DIGIT
4049
4050<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
4051<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
4052<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
4053 *expect-params ]
4054
4055<x:ref>hour</x:ref> = 2DIGIT
4056
4057<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
4058<x:ref>minute</x:ref> = 2DIGIT
4059<x:ref>month</x:ref> = %x4A.61.6E ; Jan
4060 / %x46.65.62 ; Feb
4061 / %x4D.61.72 ; Mar
4062 / %x41.70.72 ; Apr
4063 / %x4D.61.79 ; May
4064 / %x4A.75.6E ; Jun
4065 / %x4A.75.6C ; Jul
4066 / %x41.75.67 ; Aug
4067 / %x53.65.70 ; Sep
4068 / %x4F.63.74 ; Oct
4069 / %x4E.6F.76 ; Nov
4070 / %x44.65.63 ; Dec
4071
4072<x:ref>obs-date</x:ref> = rfc850-date / asctime-date
4073<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
4074
4075<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.7&gt;
4076<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 5.2&gt;
4077
4078<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 3.2.3&gt;
4079
4080<x:ref>rfc1123-date</x:ref> = day-name "," SP date1 SP time-of-day SP GMT
4081<x:ref>rfc850-date</x:ref> = day-name-l "," SP date2 SP time-of-day SP GMT
4082
4083<x:ref>second</x:ref> = 2DIGIT
4084
4085<x:ref>time-of-day</x:ref> = hour ":" minute ":" second
4086<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 3.2.3&gt;
4087
4088<x:ref>year</x:ref> = 4DIGIT
4089</artwork>
4090</figure>
4091<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
4092; Allow defined but not used
4093; Date defined but not used
4094; Expect defined but not used
4095; From defined but not used
4096; Location defined but not used
4097; Max-Forwards defined but not used
4098; Reason-Phrase defined but not used
4099; Referer defined but not used
4100; Retry-After defined but not used
4101; Server defined but not used
4102; Status-Code defined but not used
4103; User-Agent defined but not used
4104</artwork></figure></section>
4105<?ENDINC p2-semantics.abnf-appendix ?>
4106
4107<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
4108
4109<section title="Since RFC 2616">
4110<t>
4111  Extracted relevant partitions from <xref target="RFC2616"/>.
4112</t>
4113</section>
4114
4115<section title="Since draft-ietf-httpbis-p2-semantics-00">
4116<t>
4117  Closed issues:
4118  <list style="symbols"> 
4119    <t>
4120      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
4121      "Via is a MUST"
4122      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
4123    </t>
4124    <t>
4125      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
4126      "Fragments allowed in Location"
4127      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
4128    </t>
4129    <t>
4130      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
4131      "Safe Methods vs Redirection"
4132      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
4133    </t>
4134    <t>
4135      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
4136      "Revise description of the POST method"
4137      (<eref target="http://purl.org/NET/http-errata#post"/>)
4138    </t>
4139    <t>
4140      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
4141      "Normative and Informative references"
4142    </t>
4143    <t>
4144      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
4145      "RFC2606 Compliance"
4146    </t>
4147    <t>
4148      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
4149      "Informative references"
4150    </t>
4151    <t>
4152      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
4153      "Redundant cross-references"
4154    </t>
4155  </list>
4156</t>
4157<t>
4158  Other changes:
4159  <list style="symbols"> 
4160    <t>
4161      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
4162    </t>
4163  </list>
4164</t>
4165</section>
4166
4167<section title="Since draft-ietf-httpbis-p2-semantics-01">
4168<t>
4169  Closed issues:
4170  <list style="symbols"> 
4171    <t>
4172      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
4173      "PUT side effects"
4174    </t>
4175    <t>
4176      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
4177      "Duplicate Host header requirements"
4178    </t>
4179  </list>
4180</t>
4181<t>
4182  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4183  <list style="symbols"> 
4184    <t>
4185      Move "Product Tokens" section (back) into Part 1, as "token" is used
4186      in the definition of the Upgrade header field.
4187    </t>
4188    <t>
4189      Add explicit references to BNF syntax and rules imported from other parts of the specification.
4190    </t>
4191    <t>
4192      Copy definition of delta-seconds from Part6 instead of referencing it.
4193    </t>
4194  </list>
4195</t>
4196</section>
4197
4198<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
4199<t>
4200  Closed issues:
4201  <list style="symbols"> 
4202    <t>
4203      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
4204      "Requiring Allow in 405 responses"
4205    </t>
4206    <t>
4207      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
4208      "Status Code Registry"
4209    </t>
4210    <t>
4211      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
4212      "Redirection vs. Location"
4213    </t>
4214    <t>
4215      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
4216      "Cacheability of 303 response"
4217    </t>
4218    <t>
4219      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
4220      "305 Use Proxy"
4221    </t>
4222    <t>
4223      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
4224      "Classification for Allow header"
4225    </t>
4226    <t>
4227      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
4228      "PUT - 'store under' vs 'store at'"
4229    </t>
4230  </list>
4231</t>
4232<t>
4233  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
4234  <list style="symbols"> 
4235    <t>
4236      Reference RFC 3984, and update header field registrations for headers defined
4237      in this document.
4238    </t>
4239  </list>
4240</t>
4241<t>
4242  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4243  <list style="symbols"> 
4244    <t>
4245      Replace string literals when the string really is case-sensitive (method).
4246    </t>
4247  </list>
4248</t>
4249</section>
4250
4251<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
4252<t>
4253  Closed issues:
4254  <list style="symbols"> 
4255    <t>
4256      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
4257      "OPTIONS request bodies"
4258    </t>
4259    <t>
4260      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
4261      "Description of CONNECT should refer to RFC2817"
4262    </t>
4263    <t>
4264      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
4265      "Location Content-Location reference request/response mixup"
4266    </t>
4267  </list>
4268</t>
4269<t>
4270  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
4271  <list style="symbols"> 
4272    <t>
4273      Added initial proposal for registration process, plus initial
4274      content (non-HTTP/1.1 methods to be added by a separate specification).
4275    </t>
4276  </list>
4277</t>
4278</section>
4279
4280<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
4281<t>
4282  Closed issues:
4283  <list style="symbols"> 
4284    <t>
4285      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
4286      "Content-*"
4287    </t>
4288    <t>
4289      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
4290      "RFC 2822 is updated by RFC 5322"
4291    </t>
4292  </list>
4293</t>
4294<t>
4295  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4296  <list style="symbols"> 
4297    <t>
4298      Use "/" instead of "|" for alternatives.
4299    </t>
4300    <t>
4301      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
4302      whitespace ("OWS") and required whitespace ("RWS").
4303    </t>
4304    <t>
4305      Rewrite ABNFs to spell out whitespace rules, factor out
4306      header field value format definitions.
4307    </t>
4308  </list>
4309</t>
4310</section>
4311
4312<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
4313<t>
4314  Closed issues:
4315  <list style="symbols"> 
4316    <t>
4317      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
4318      "Reason-Phrase BNF"
4319    </t>
4320  </list>
4321</t>
4322<t>
4323  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4324  <list style="symbols"> 
4325    <t>
4326      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
4327    </t>
4328  </list>
4329</t>
4330</section>
4331
4332<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
4333<t>
4334  Closed issues:
4335  <list style="symbols"> 
4336    <t>
4337      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
4338      "Clarify when Referer is sent"
4339    </t>
4340    <t>
4341      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
4342      "status codes vs methods"
4343    </t>
4344    <t>
4345      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
4346      "Do not require "updates" relation for specs that register status codes or method names"
4347    </t>
4348  </list>
4349</t>
4350</section>
4351
4352<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
4353<t>
4354  Closed issues:
4355  <list style="symbols"> 
4356    <t>
4357      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
4358      "Idempotency"
4359    </t>
4360    <t>
4361      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
4362      "TRACE security considerations"
4363    </t>
4364    <t>
4365      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
4366      "Clarify rules for determining what entities a response carries"
4367    </t>
4368    <t>
4369      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
4370      "update note citing RFC 1945 and 2068"
4371    </t>
4372    <t>
4373      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
4374      "update note about redirect limit"
4375    </t>
4376    <t>
4377      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
4378      "Location header ABNF should use 'URI'"
4379    </t>
4380    <t>
4381      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
4382      "fragments in Location vs status 303"
4383    </t>
4384    <t>
4385      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
4386      "move IANA registrations for optional status codes"
4387    </t>
4388  </list>
4389</t>
4390<t>
4391  Partly resolved issues:
4392  <list style="symbols"> 
4393    <t>
4394      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
4395      "Are OPTIONS and TRACE safe?"
4396    </t>
4397  </list>
4398</t>
4399</section>
4400
4401<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
4402<t>
4403  Closed issues:
4404  <list style="symbols"> 
4405    <t>
4406      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
4407      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
4408      status codes when fixing this previously)
4409    </t>
4410  </list>
4411</t>
4412</section>
4413
4414<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
4415<t>
4416  Closed issues:
4417  <list style="symbols"> 
4418    <t>
4419      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4420      "Fragment combination / precedence during redirects"
4421    </t>
4422  </list>
4423</t>
4424<t>
4425  Partly resolved issues:
4426  <list style="symbols"> 
4427    <t>
4428      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
4429      "Location header payload handling"
4430    </t>
4431    <t>
4432      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
4433      "Term for the requested resource's URI"
4434    </t>
4435  </list>
4436</t>
4437</section>
4438
4439<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
4440<t>
4441  Closed issues:
4442  <list style="symbols"> 
4443    <t>
4444      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
4445      "Clarify 'Requested Variant'"
4446    </t>
4447    <t>
4448      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
4449      "Clarify entity / representation / variant terminology"
4450    </t>
4451    <t>
4452      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/139"/>:
4453      "Methods and Caching"
4454    </t>
4455    <t>
4456      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/190"/>:
4457      "OPTIONS vs Max-Forwards"
4458    </t>
4459    <t>
4460      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/199"/>:
4461      "Status codes and caching"
4462    </t>
4463    <t>
4464      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
4465      "consider removing the 'changes from 2068' sections"
4466    </t>
4467  </list>
4468</t>
4469</section>
4470
4471<section title="Since draft-ietf-httpbis-p2-semantics-11" anchor="changes.since.11">
4472<t>
4473  Closed issues:
4474  <list style="symbols"> 
4475    <t>
4476      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/229"/>:
4477      "Considerations for new status codes"
4478    </t>
4479    <t>
4480      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/230"/>:
4481      "Considerations for new methods"
4482    </t>
4483    <t>
4484      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/232"/>:
4485      "User-Agent guidelines" (relating to the 'User-Agent' header field)
4486    </t>
4487  </list>
4488</t>
4489</section>
4490
4491<section title="Since draft-ietf-httpbis-p2-semantics-12" anchor="changes.since.12">
4492<t>
4493  Closed issues:
4494  <list style="symbols"> 
4495    <t>
4496      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4497      "Fragment combination / precedence during redirects" (added warning
4498      about having a fragid on the redirect may cause inconvenience in
4499      some cases)
4500    </t>
4501    <t>
4502      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/79"/>:
4503      "Content-* vs. PUT"
4504    </t>
4505    <t>
4506      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/88"/>:
4507      "205 Bodies"
4508    </t>
4509    <t>
4510      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/102"/>:
4511      "Understanding Content-* on non-PUT requests"
4512    </t>
4513    <t>
4514      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
4515      "Content-*"
4516    </t>
4517    <t>
4518      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/104"/>:
4519      "Header type defaulting"
4520    </t>
4521    <t>
4522      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
4523      "PUT - 'store under' vs 'store at'"
4524    </t>
4525    <t>
4526      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/137"/>:
4527      "duplicate ABNF for Reason-Phrase"
4528    </t>
4529    <t>
4530      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/180"/>:
4531      "Note special status of Content-* prefix in header registration procedures"
4532    </t>
4533    <t>
4534      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/203"/>:
4535      "Max-Forwards vs extension methods"
4536    </t>
4537    <t>
4538      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/213"/>:
4539      "What is the value space of HTTP status codes?" (actually fixed in
4540      draft-ietf-httpbis-p2-semantics-11)
4541    </t>
4542    <t>
4543      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/224"/>:
4544      "Header Classification"
4545    </t>
4546    <t>
4547      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/225"/>:
4548      "PUT side effect: invalidation or just stale?"
4549    </t>
4550    <t>
4551      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/226"/>:
4552      "proxies not supporting certain methods"
4553    </t>
4554    <t>
4555      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/239"/>:
4556      "Migrate CONNECT from RFC2817 to p2"
4557    </t>
4558    <t>
4559      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/240"/>:
4560      "Migrate Upgrade details from RFC2817"
4561    </t>
4562    <t>
4563      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/267"/>:
4564      "clarify PUT semantics'"
4565    </t>
4566    <t>
4567      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/275"/>:
4568      "duplicate ABNF for 'Method'"
4569    </t>
4570    <t>
4571      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4572      "untangle ABNFs for header fields"
4573    </t>
4574  </list>
4575</t>
4576</section>
4577
4578<section title="Since draft-ietf-httpbis-p2-semantics-13" anchor="changes.since.13">
4579<t>
4580  Closed issues:
4581  <list style="symbols"> 
4582    <t>
4583      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4584      "untangle ABNFs for header fields"
4585    </t>
4586    <t>
4587      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/251"/>:
4588      "message-body in CONNECT request"
4589    </t>
4590  </list>
4591</t>
4592</section>
4593
4594<section title="Since draft-ietf-httpbis-p2-semantics-14" anchor="changes.since.14">
4595<t>
4596  Closed issues:
4597  <list style="symbols"> 
4598    <t>
4599      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/255"/>:
4600      "Clarify status code for rate limiting"
4601    </t>
4602    <t>
4603      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/294"/>:
4604      "clarify 403 forbidden"
4605    </t>
4606    <t>
4607      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/296"/>:
4608      "Clarify 203 Non-Authoritative Information"
4609    </t>
4610    <t>
4611      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/298"/>:
4612      "update default reason phrase for 413"
4613    </t>
4614  </list>
4615</t>
4616</section>
4617
4618<section title="Since draft-ietf-httpbis-p2-semantics-15" anchor="changes.since.15">
4619<t>
4620  Closed issues:
4621  <list style="symbols"> 
4622    <t>
4623      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/285"/>:
4624      "Strength of requirements on Accept re: 406"
4625    </t>
4626    <t>
4627      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/303"/>:
4628      "400 response isn't generic"
4629    </t>
4630  </list>
4631</t>
4632</section>
4633
4634<section title="Since draft-ietf-httpbis-p2-semantics-16" anchor="changes.since.16">
4635<t>
4636  Closed issues:
4637  <list style="symbols"> 
4638    <t>
4639      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/160"/>:
4640      "Redirects and non-GET methods"
4641    </t>
4642    <t>
4643      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/310"/>:
4644      "clarify 303 redirect on HEAD"
4645    </t>
4646  </list>
4647</t>
4648<t>
4649  Work-in-progress:
4650  <list style="symbols"> 
4651    <t>
4652      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/231"/>:
4653      "Considerations for new headers"
4654    </t>
4655  </list>
4656</t>
4657</section>
4658
4659</section>
4660
4661</back>
4662</rfc>
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