source: draft-ietf-httpbis/latest/p2-semantics.xml @ 1440

Last change on this file since 1440 was 1440, checked in by julian.reschke@…, 8 years ago

Update org for Mark in references to P6 for consistency (doesn't affect generated docs) (see [1438])

  • Property svn:eol-style set to native
File size: 190.5 KB
Line 
1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD NOT</bcp14>">
14  <!ENTITY ID-VERSION "latest">
15  <!ENTITY ID-MONTH "September">
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-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
52  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
53  <!ENTITY header-fields              "<xref target='Part1' x:rel='#header.fields' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
54  <!ENTITY header-host                "<xref target='Part1' x:rel='#header.host' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
55  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
56  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
57  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
58  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
59  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
60  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
61  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
62  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
63  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
64  <!ENTITY header-upgrade             "<xref target='Part1' x:rel='#header.upgrade' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
65  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.te' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
66  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
67  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
68  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
69  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
70  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
71  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
72  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='#internet.media.type.message.http' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
73  <!ENTITY status-206                 "<xref target='Part5' x:rel='#status.206' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
74  <!ENTITY status-304                 "<xref target='Part4' x:rel='#status.304' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
75  <!ENTITY status-401                 "<xref target='Part7' x:rel='#status.401' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
76  <!ENTITY status-407                 "<xref target='Part7' x:rel='#status.407' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
77  <!ENTITY status-412                 "<xref target='Part4' x:rel='#status.412' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
78  <!ENTITY status-416                 "<xref target='Part5' x:rel='#status.416' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
79  <!ENTITY p3-header-fields           "<xref target='Part3' x:rel='#header.field.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
80  <!ENTITY p4-status-codes            "<xref target='Part4' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
81  <!ENTITY p5-status-codes            "<xref target='Part5' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
82  <!ENTITY p7-status-codes            "<xref target='Part7' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
83  <!ENTITY p6-heuristic               "<xref target='Part6' x:rel='#heuristic.freshness' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
84  <!ENTITY p6-explicit                "<xref target='Part6' x:rel='#calculating.freshness.lifetime' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
85  <!ENTITY p6-invalid                 "<xref target='Part6' x:rel='#invalidation.after.updates.or.deletions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
86]>
87<?rfc toc="yes" ?>
88<?rfc symrefs="yes" ?>
89<?rfc sortrefs="yes" ?>
90<?rfc compact="yes"?>
91<?rfc subcompact="no" ?>
92<?rfc linkmailto="no" ?>
93<?rfc editing="no" ?>
94<?rfc comments="yes"?>
95<?rfc inline="yes"?>
96<?rfc rfcedstyle="yes"?>
97<?rfc-ext allow-markup-in-artwork="yes" ?>
98<?rfc-ext include-references-in-index="yes" ?>
99<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
100     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
101     xmlns:x='http://purl.org/net/xml2rfc/ext'
102     xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
103<front>
104
105  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
106
107  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
108    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
109    <address>
110      <postal>
111        <street>345 Park Ave</street>
112        <city>San Jose</city>
113        <region>CA</region>
114        <code>95110</code>
115        <country>USA</country>
116      </postal>
117      <email>fielding@gbiv.com</email>
118      <uri>http://roy.gbiv.com/</uri>
119    </address>
120  </author>
121
122  <author initials="J." surname="Gettys" fullname="Jim Gettys">
123    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
124    <address>
125      <postal>
126        <street>21 Oak Knoll Road</street>
127        <city>Carlisle</city>
128        <region>MA</region>
129        <code>01741</code>
130        <country>USA</country>
131      </postal>
132      <email>jg@freedesktop.org</email>
133      <uri>http://gettys.wordpress.com/</uri>
134    </address>
135  </author>
136 
137  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
138    <organization abbrev="HP">Hewlett-Packard Company</organization>
139    <address>
140      <postal>
141        <street>HP Labs, Large Scale Systems Group</street>
142        <street>1501 Page Mill Road, MS 1177</street>
143        <city>Palo Alto</city>
144        <region>CA</region>
145        <code>94304</code>
146        <country>USA</country>
147      </postal>
148      <email>JeffMogul@acm.org</email>
149    </address>
150  </author>
151
152  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
153    <organization abbrev="Microsoft">Microsoft Corporation</organization>
154    <address>
155      <postal>
156        <street>1 Microsoft Way</street>
157        <city>Redmond</city>
158        <region>WA</region>
159        <code>98052</code>
160        <country>USA</country>
161      </postal>
162      <email>henrikn@microsoft.com</email>
163    </address>
164  </author>
165
166  <author initials="L." surname="Masinter" fullname="Larry Masinter">
167    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
168    <address>
169      <postal>
170        <street>345 Park Ave</street>
171        <city>San Jose</city>
172        <region>CA</region>
173        <code>95110</code>
174        <country>USA</country>
175      </postal>
176      <email>LMM@acm.org</email>
177      <uri>http://larry.masinter.net/</uri>
178    </address>
179  </author>
180 
181  <author initials="P." surname="Leach" fullname="Paul J. Leach">
182    <organization abbrev="Microsoft">Microsoft Corporation</organization>
183    <address>
184      <postal>
185        <street>1 Microsoft Way</street>
186        <city>Redmond</city>
187        <region>WA</region>
188        <code>98052</code>
189      </postal>
190      <email>paulle@microsoft.com</email>
191    </address>
192  </author>
193   
194  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
195    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
196    <address>
197      <postal>
198        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
199        <street>The Stata Center, Building 32</street>
200        <street>32 Vassar Street</street>
201        <city>Cambridge</city>
202        <region>MA</region>
203        <code>02139</code>
204        <country>USA</country>
205      </postal>
206      <email>timbl@w3.org</email>
207      <uri>http://www.w3.org/People/Berners-Lee/</uri>
208    </address>
209  </author>
210
211  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
212    <organization abbrev="W3C">World Wide Web Consortium</organization>
213    <address>
214      <postal>
215        <street>W3C / ERCIM</street>
216        <street>2004, rte des Lucioles</street>
217        <city>Sophia-Antipolis</city>
218        <region>AM</region>
219        <code>06902</code>
220        <country>France</country>
221      </postal>
222      <email>ylafon@w3.org</email>
223      <uri>http://www.raubacapeu.net/people/yves/</uri>
224    </address>
225  </author>
226
227  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
228    <organization abbrev="greenbytes">greenbytes GmbH</organization>
229    <address>
230      <postal>
231        <street>Hafenweg 16</street>
232        <city>Muenster</city><region>NW</region><code>48155</code>
233        <country>Germany</country>
234      </postal>
235      <phone>+49 251 2807760</phone>
236      <facsimile>+49 251 2807761</facsimile>
237      <email>julian.reschke@greenbytes.de</email>
238      <uri>http://greenbytes.de/tech/webdav/</uri>
239    </address>
240  </author>
241
242  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
243  <workgroup>HTTPbis Working Group</workgroup>
244
245<abstract>
246<t>
247   The Hypertext Transfer Protocol (HTTP) is an application-level protocol for
248   distributed, collaborative, hypertext information systems. HTTP has been in
249   use by the World Wide Web global information initiative since 1990. This
250   document is Part 2 of the seven-part specification that defines the protocol
251   referred to as "HTTP/1.1" and, taken together, obsoletes RFC 2616.
252</t>
253<t>
254   Part 2 defines the semantics of HTTP messages as expressed by request
255   methods, request header fields, response status codes, and response header
256   fields.
257</t>
258</abstract>
259
260<note title="Editorial Note (To be removed by RFC Editor)">
261  <t>
262    Discussion of this draft should take place on the HTTPBIS working group
263    mailing list (ietf-http-wg@w3.org), which is archived at
264    <eref target="http://lists.w3.org/Archives/Public/ietf-http-wg/"/>.
265  </t>
266  <t>
267    The current issues list is at
268    <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/> and related
269    documents (including fancy diffs) can be found at
270    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
271  </t>
272  <t>
273    The changes in this draft are summarized in <xref target="changes.since.16"/>.
274  </t>
275</note>
276</front>
277<middle>
278<section title="Introduction" anchor="introduction">
279<t>
280   This document defines HTTP/1.1 request and response semantics.  Each HTTP
281   message, as defined in &messaging;, is in the form of either a request or
282   a response.  An HTTP server listens on a connection for HTTP requests and
283   responds to each request, in the order received on that connection, with
284   one or more HTTP response messages.  This document defines the commonly
285   agreed upon semantics of the HTTP uniform interface, the intentions defined
286   by each request method, and the various response messages that might be
287   expected as a result of applying that method to the target resource.
288</t>
289<t>
290   This document is currently disorganized in order to minimize the changes
291   between drafts and enable reviewers to see the smaller errata changes.
292   A future draft will reorganize the sections to better reflect the content.
293   In particular, the sections will be ordered according to the typical
294   processing of an HTTP request message (after message parsing): resource
295   mapping, methods, request modifying header fields, response status,
296   status modifying header fields, and resource metadata.  The current mess
297   reflects how widely dispersed these topics and associated requirements
298   had become in <xref target="RFC2616"/>.
299</t>
300
301<section title="Requirements" anchor="intro.requirements">
302<t>
303   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
304   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
305   document are to be interpreted as described in <xref target="RFC2119"/>.
306</t>
307<t>
308   An implementation is not compliant if it fails to satisfy one or more
309   of the "MUST" or "REQUIRED" level requirements for the protocols it
310   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
311   level and all the "SHOULD" level requirements for its protocols is said
312   to be "unconditionally compliant"; one that satisfies all the "MUST"
313   level requirements but not all the "SHOULD" level requirements for its
314   protocols is said to be "conditionally compliant".
315</t>
316</section>
317
318<section title="Syntax Notation" anchor="notation">
319  <x:anchor-alias value="CR"/>
320  <x:anchor-alias value="DIGIT"/>
321  <x:anchor-alias value="LF"/>
322  <x:anchor-alias value="HTAB"/>
323  <x:anchor-alias value="VCHAR"/>
324  <x:anchor-alias value="SP"/>
325<t>
326  This specification uses the ABNF syntax defined in &notation; (which
327  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
328  <xref target="collected.abnf"/> shows the collected ABNF, with the list
329  rule expanded.
330</t>
331<t>
332  The following core rules are included by
333  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
334  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
335  DIGIT (decimal 0-9), DQUOTE (double quote),
336  HEXDIG (hexadecimal 0-9/A-F/a-f), HTAB (horizontal tab), LF (line feed),
337  OCTET (any 8-bit sequence of data), SP (space), and
338  VCHAR (any visible US-ASCII character).
339</t>
340
341<section title="Core Rules" anchor="core.rules">
342  <x:anchor-alias value="obs-text"/>
343  <x:anchor-alias value="quoted-string"/>
344  <x:anchor-alias value="token"/>
345  <x:anchor-alias value="OWS"/>
346  <x:anchor-alias value="RWS"/>
347<t>
348  The core rules below are defined in <xref target="Part1"/>:
349</t>
350<figure><artwork type="abnf2616">
351  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
352  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
353  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
354  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &field-rules;&gt;
355  <x:ref>token</x:ref>         = &lt;token, defined in &field-rules;&gt;
356</artwork></figure>
357</section>
358
359<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
360  <x:anchor-alias value="absolute-URI"/>
361  <x:anchor-alias value="comment"/>
362  <x:anchor-alias value="partial-URI"/>
363  <x:anchor-alias value="product"/>
364  <x:anchor-alias value="URI-reference"/>
365<t>
366  The ABNF rules below are defined in other parts:
367</t>
368<figure><!--Part1--><artwork type="abnf2616">
369  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
370  <x:ref>comment</x:ref>       = &lt;comment, defined in &header-fields;&gt;
371  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
372  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
373  <x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in &uri;&gt;
374</artwork></figure>
375</section>
376</section>
377</section>
378
379<section title="Method" anchor="method">
380  <x:anchor-alias value="Method"/>
381  <x:anchor-alias value="extension-method"/>
382<t>
383   The Method token indicates the request method to be performed on the target
384   resource (&effective-request-uri;). The method is case-sensitive.
385</t>
386<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/>
387  <x:ref>Method</x:ref>         = <x:ref>token</x:ref>
388</artwork></figure>
389<t>
390   The list of methods allowed by a resource can be specified in an
391   Allow header field (<xref target="header.allow"/>). The status code of the response
392   always notifies the client whether a method is currently allowed on a
393   resource, since the set of allowed methods can change dynamically. An
394   origin server &SHOULD; respond with the status code 405 (Method Not Allowed)
395   if the method is known by the origin server but not allowed for the
396   resource, and 501 (Not Implemented) if the method is
397   unrecognized or not implemented by the origin server. The methods GET
398   and HEAD &MUST; be supported by all general-purpose servers. All other
399   methods are &OPTIONAL;; however, if the above methods are implemented,
400   they &MUST; be implemented with the same semantics as those specified
401   in <xref target="method.definitions"/>.
402</t>
403
404<section title="Overview of Methods" anchor="overview.of.methods">
405<t>
406  The methods listed below are defined in <xref target="method.definitions"/>.
407</t>
408<texttable align="left">
409  <ttcol>Method Name</ttcol><ttcol>Defined in...</ttcol>
410 
411  <c>OPTIONS</c> <c><xref target="OPTIONS"/></c>
412  <c>GET</c> <c><xref target="GET"/></c>
413  <c>HEAD</c> <c><xref target="HEAD"/></c>
414  <c>POST</c> <c><xref target="POST"/></c>
415  <c>PUT</c> <c><xref target="PUT"/></c>
416  <c>DELETE</c> <c><xref target="DELETE"/></c>
417  <c>TRACE</c> <c><xref target="TRACE"/></c>
418  <c>CONNECT</c> <c><xref target="CONNECT"/></c>
419</texttable>
420<t>
421  Note that this list is not exhaustive &mdash; it does not include request methods defined
422  in other specifications.
423</t>
424</section>
425
426<section title="Method Registry" anchor="method.registry">
427<t>
428  The HTTP Method Registry defines the name space for the Method token in the
429  Request line of an HTTP request.
430</t>
431<t>
432  Registrations &MUST; include the following fields:
433  <list style="symbols">
434    <t>Method Name (see <xref target="method"/>)</t>
435    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
436    <t>Pointer to specification text</t>
437  </list>
438</t>
439<t>
440  Values to be added to this name space are subject to IETF review
441  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
442</t>
443<t>
444  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
445</t>
446
447<section title="Considerations for New Methods" anchor="considerations.for.new.methods">
448<t>
449   When it is necessary to express new semantics for a HTTP request that
450   aren't specific to a single application or media type, and currently defined
451   methods are inadequate, it may be appropriate to register a new method.
452</t>
453<t>
454   HTTP methods are generic; that is, they are potentially applicable to any
455   resource, not just one particular media type, "type" of resource, or
456   application. As such, it is preferred that new HTTP methods be registered
457   in a document that isn't specific to a single application, so that this is
458   clear.
459</t>
460<t>
461   Due to the parsing rules defined in &message-body;, definitions of HTTP
462   methods cannot prohibit the presence of a message-body on either the request
463   or the response message (with responses to HEAD requests being the single
464   exception). Definitions of new methods cannot change this rule, but they can
465   specify that only zero-length bodies (as opposed to absent bodies) are allowed.
466</t>
467<t>
468   New method definitions need to indicate whether they are safe (<xref
469   target="safe.methods"/>), what semantics (if any) the request body has,
470   and whether they are idempotent (<xref target="idempotent.methods"/>).
471   They also need to state whether they can be cached (&caching;); in
472   particular what conditions a cache may store the response, and under what
473   conditions such a stored response may be used to satisfy a subsequent
474   request.
475</t>
476</section>
477
478</section>
479</section>
480
481<section title="Header Fields" anchor="header.fields">
482<t>
483   Header fields are key value pairs that can be used to communicate data about
484   the message, its payload, the target resource, or about the connection
485   itself (i.e., control data).  See &header-fields; for a general definition
486   of their syntax.
487</t>
488
489<section title="Considerations for Creating Header Fields" anchor="considerations.for.creating.header.fields">
490<t>
491   New header fields are registered using the procedures described in
492   <xref target="RFC3864"/>.
493</t>
494<t>
495   The requirements for header field names are defined in
496   <xref target="RFC3864" x:fmt="of" x:sec="4.1"/>.  Authors of specifications
497   defining new fields are advised to keep the name as short as practical, and
498   not to prefix them with "X-" if they are to be registered (either
499   immediately or in the future).
500</t>
501<t>
502   New header field values typically have their syntax defined using ABNF
503   (<xref target="RFC5234"/>), using the extensions defined in &notation-abnf;
504   as necessary, and are usually constrained to the range of ASCII characters.
505   Header fields needing a greater range of characters can use an encoding
506   such as the one defined in <xref target="RFC5987"/>.
507</t>
508<t>
509   Because commas (",") are used as a generic delimiter between field-values,
510   they need to be treated with care if they are allowed in the field-value's
511   payload. Typically, components that might contain a comma are protected with
512   double-quotes using the quoted-string ABNF production (&field-rules;).
513</t>
514<t>
515   For example, a textual date and a URI (either of which might contain a comma)
516   could be safely carried in field-values like these:
517</t>
518<figure><artwork type="example">
519  Example-URI-Field: "http://example.com/a.html,foo",
520                     "http://without-a-comma.example.com/"
521  Example-Date-Field: "Sat, 04 May 1996", "Wed, 14 Sep 2005"
522</artwork></figure>
523<t>
524   Authors of specifications defining new header fields are advised to consider
525   documenting:
526  <list style="symbols">
527    <t>Whether the field is a single value, or whether it can be a list
528    (delimited by commas; see &header-fields;).</t>
529    <t>Under what conditions the header field can be used; e.g., only i
530    responses or requests, in all messages, only on responses to a particular
531    request method.</t>
532    <t>Whether it is appropriate to list the field-name in the Connection header
533    (i.e., if the header is to be hop-by-hop, see &header-connection;).</t>
534    <t>Under what conditions intermediaries are allowed to modify the header
535    field's value, insert or delete it.</t>
536    <t>How the header might interact with caching (see <xref target="Part6"/>).</t>
537    <t>Whether the header field is useful or allowable in trailers (see
538    &chunked-encoding;).</t>
539    <t>Whether the header field should be preserved across redirects.</t>
540  </list>
541</t>
542</section>
543
544<section title="Request Header Fields" anchor="request.header.fields">
545  <x:anchor-alias value="request-header"/>
546<t>
547   The request header fields allow the client to pass additional
548   information about the request, and about the client itself, to the
549   server. These fields act as request modifiers, with semantics
550   equivalent to the parameters on a programming language method
551   invocation.
552</t>
553<texttable align="left">
554  <ttcol>Header Field Name</ttcol>
555  <ttcol>Defined in...</ttcol>
556
557  <c>Accept</c> <c>&header-accept;</c>
558  <c>Accept-Charset</c> <c>&header-accept-charset;</c>
559  <c>Accept-Encoding</c> <c>&header-accept-encoding;</c>
560  <c>Accept-Language</c> <c>&header-accept-language;</c>
561  <c>Authorization</c> <c>&header-authorization;</c>
562  <c>Expect</c> <c><xref target="header.expect"/></c>
563  <c>From</c> <c><xref target="header.from"/></c>
564  <c>Host</c> <c>&header-host;</c>
565  <c>If-Match</c> <c>&header-if-match;</c>
566  <c>If-Modified-Since</c> <c>&header-if-modified-since;</c>
567  <c>If-None-Match</c> <c>&header-if-none-match;</c>
568  <c>If-Range</c> <c>&header-if-range;</c>
569  <c>If-Unmodified-Since</c> <c>&header-if-unmodified-since;</c>
570  <c>Max-Forwards</c> <c><xref target="header.max-forwards"/></c>
571  <c>Proxy-Authorization</c> <c>&header-proxy-authorization;</c>
572  <c>Range</c> <c>&header-range;</c>
573  <c>Referer</c> <c><xref target="header.referer"/></c>
574  <c>TE</c> <c>&header-te;</c>
575  <c>User-Agent</c> <c><xref target="header.user-agent"/></c>
576</texttable>
577</section>
578
579<section title="Response Header Fields" anchor="response.header.fields">
580  <x:anchor-alias value="response-header"/>
581<t>
582   The response header fields allow the server to pass additional
583   information about the response which cannot be placed in the Status-Line.
584   These header fields give information about the server and about
585   further access to the target resource (&effective-request-uri;).
586</t>
587<texttable align="left">
588  <ttcol>Header Field Name</ttcol><ttcol>Defined in...</ttcol>
589
590  <c>Accept-Ranges</c> <c>&header-accept-ranges;</c>
591  <c>Age</c> <c>&header-age;</c>
592  <c>Allow</c> <c><xref target="header.allow"/></c>
593  <c>Date</c> <c><xref target="header.date"/></c>
594  <c>ETag</c> <c>&header-etag;</c>
595  <c>Location</c> <c><xref target="header.location"/></c>
596  <c>Proxy-Authenticate</c> <c>&header-proxy-authenticate;</c>
597  <c>Retry-After</c> <c><xref target="header.retry-after"/></c>
598  <c>Server</c> <c><xref target="header.server"/></c>
599  <c>Vary</c> <c>&header-vary;</c>
600  <c>WWW-Authenticate</c> <c>&header-www-authenticate;</c>
601</texttable>
602</section>
603
604</section>
605
606<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
607  <x:anchor-alias value="Reason-Phrase"/>
608  <x:anchor-alias value="Status-Code"/>
609  <x:anchor-alias value="extension-code"/>
610<t>
611   The Status-Code element is a 3-digit integer result code of the attempt to
612   understand and satisfy the request.
613</t>
614<t>
615   The Reason-Phrase is intended to give a short textual description of the
616   Status-Code and is intended for a human user. The client does not need
617   to examine or display the Reason-Phrase.
618</t>
619<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"/>
620  <x:ref>Status-Code</x:ref>    = 3<x:ref>DIGIT</x:ref>
621  <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> )
622</artwork></figure>
623<t>
624   HTTP status codes are extensible. HTTP applications are not required
625   to understand the meaning of all registered status codes, though such
626   understanding is obviously desirable. However, applications &MUST;
627   understand the class of any status code, as indicated by the first
628   digit, and treat any unrecognized response as being equivalent to the
629   x00 status code of that class, with the exception that an
630   unrecognized response &MUST-NOT; be cached. For example, if an
631   unrecognized status code of 431 is received by the client, it can
632   safely assume that there was something wrong with its request and
633   treat the response as if it had received a 400 status code. In such
634   cases, user agents &SHOULD; present to the user the representation enclosed
635   with the response, since that representation is likely to include human-readable
636   information which will explain the unusual status.
637</t>
638
639<section title="Overview of Status Codes" anchor="overview.of.status.codes">
640<t> 
641   The status codes listed below are defined in <xref target="status.codes"/>
642   of this specification, &p4-status-codes;, &p5-status-codes;, and &p7-status-codes;.
643   The reason phrases listed here are only recommendations &mdash; they can be
644   replaced by local equivalents without affecting the protocol.
645</t>
646<texttable align="left">
647  <ttcol>Status-Code</ttcol>
648  <ttcol>Reason-Phrase</ttcol>
649  <ttcol>Defined in...</ttcol>
650 
651  <c>100</c> <c>Continue</c> <c><xref target="status.100"/></c>
652  <c>101</c> <c>Switching Protocols</c> <c><xref target="status.101"/></c>
653
654  <c>200</c> <c>OK</c> <c><xref target="status.200"/></c>
655  <c>201</c> <c>Created</c> <c><xref target="status.201"/></c>
656  <c>202</c> <c>Accepted</c> <c><xref target="status.202"/></c>
657  <c>203</c> <c>Non-Authoritative Information</c> <c><xref target="status.203"/></c>
658  <c>204</c> <c>No Content</c> <c><xref target="status.204"/></c>
659  <c>205</c> <c>Reset Content</c> <c><xref target="status.205"/></c>
660  <c>206</c> <c>Partial Content</c> <c>&status-206;</c>
661
662  <c>300</c> <c>Multiple Choices</c> <c><xref target="status.300"/></c>
663  <c>301</c> <c>Moved Permanently</c> <c><xref target="status.301"/></c>
664  <c>302</c> <c>Found</c> <c><xref target="status.302"/></c>
665  <c>303</c> <c>See Other</c> <c><xref target="status.303"/></c>
666  <c>304</c> <c>Not Modified</c> <c>&status-304;</c>
667  <c>305</c> <c>Use Proxy</c> <c><xref target="status.305"/></c>
668  <c>307</c> <c>Temporary Redirect</c> <c><xref target="status.307"/></c>
669
670  <c>400</c> <c>Bad Request</c> <c><xref target="status.400"/></c>
671  <c>401</c> <c>Unauthorized</c> <c>&status-401;</c>
672  <c>402</c> <c>Payment Required</c> <c><xref target="status.402"/></c>
673  <c>403</c> <c>Forbidden</c> <c><xref target="status.403"/></c>
674  <c>404</c> <c>Not Found</c> <c><xref target="status.404"/></c>
675  <c>405</c> <c>Method Not Allowed</c> <c><xref target="status.405"/></c>
676  <c>406</c> <c>Not Acceptable</c> <c><xref target="status.406"/></c>
677  <c>407</c> <c>Proxy Authentication Required</c> <c>&status-407;</c>
678  <c>408</c> <c>Request Time-out</c> <c><xref target="status.408"/></c>
679  <c>409</c> <c>Conflict</c> <c><xref target="status.409"/></c>
680  <c>410</c> <c>Gone</c> <c><xref target="status.410"/></c>
681  <c>411</c> <c>Length Required</c> <c><xref target="status.411"/></c>
682  <c>412</c> <c>Precondition Failed</c> <c>&status-412;</c>
683  <c>413</c> <c>Request Representation Too Large</c> <c><xref target="status.413"/></c>
684  <c>414</c> <c>URI Too Long</c> <c><xref target="status.414"/></c>
685  <c>415</c> <c>Unsupported Media Type</c> <c><xref target="status.415"/></c>
686  <c>416</c> <c>Requested range not satisfiable</c> <c>&status-416;</c>
687  <c>417</c> <c>Expectation Failed</c> <c><xref target="status.417"/></c>
688  <c>426</c> <c>Upgrade Required</c> <c><xref target="status.426"/></c>
689
690  <c>500</c> <c>Internal Server Error</c> <c><xref target="status.500"/></c>
691  <c>501</c> <c>Not Implemented</c> <c><xref target="status.501"/></c>
692  <c>502</c> <c>Bad Gateway</c> <c><xref target="status.502"/></c>
693  <c>503</c> <c>Service Unavailable</c> <c><xref target="status.503"/></c>
694  <c>504</c> <c>Gateway Time-out</c> <c><xref target="status.504"/></c>
695  <c>505</c> <c>HTTP Version not supported</c> <c><xref target="status.505"/></c>
696</texttable>
697<t>
698   Note that this list is not exhaustive &mdash; it does not include
699   extension status codes defined in other specifications.
700</t>
701</section>
702
703<section title="Status Code Registry" anchor="status.code.registry">
704<t>
705  The HTTP Status Code Registry defines the name space for the Status-Code
706  token in the Status-Line of an HTTP response.
707</t>
708<t>
709  Values to be added to this name space are subject to IETF review
710  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
711</t>
712<t>
713  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
714</t>
715
716<section title="Considerations for New Status Codes" anchor="considerations.for.new.status.codes">
717<t>
718   When it is necessary to express new semantics for a HTTP response that
719   aren't specific to a single application or media type, and currently defined
720   status codes are inadequate, a new status code can be registered.
721</t>
722<t>
723   HTTP status codes are generic; that is, they are potentially applicable to
724   any resource, not just one particular media type, "type" of resource, or
725   application. As such, it is preferred that new HTTP status codes be
726   registered in a document that isn't specific to a single application, so
727   that this is clear.
728</t>
729<t>
730   Definitions of new HTTP status codes typically explain the request
731   conditions that produce a response containing the status code (e.g.,
732   combinations of request headers and/or method(s)), along with any
733   interactions with response headers (e.g., those that are required, those
734   that modify the semantics of the response).
735</t>
736<t>
737   New HTTP status codes are required to fall under one of the categories
738   defined in <xref target="status.codes"/>. To allow existing parsers to
739   properly handle them, new status codes cannot disallow a response body,
740   although they can mandate a zero-length response body. They can require the
741   presence of one or more particular HTTP response header(s).
742</t>
743<t>
744   Likewise, their definitions can specify that caches are allowed to use
745   heuristics to determine their freshness (see &caching;; by default, it is
746   not allowed), and can define how to determine the resource which they
747   carry a representation for (see <xref
748   target="identifying.response.associated.with.representation"/>; by default,
749   it is anonymous).
750</t>
751</section>
752
753</section>
754
755</section>
756
757<section title="Representation" anchor="representation">
758<t>
759   Request and Response messages &MAY; transfer a representation if not otherwise
760   restricted by the request method or response status code. A representation
761   consists of metadata (representation header fields) and data (representation
762   body).  When a complete or partial representation is enclosed in an HTTP message,
763   it is referred to as the payload of the message. HTTP representations
764   are defined in &payload;.
765</t>
766<t>
767   A representation body is only present in a message when a message-body is
768   present, as described in &message-body;. The representation body is obtained
769   from the message-body by decoding any Transfer-Encoding that might
770   have been applied to ensure safe and proper transfer of the message.
771</t>
772
773<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
774<t>
775   It is sometimes necessary to determine an identifier for the resource
776   associated with a representation.
777</t>
778<t>
779   An HTTP request representation, when present, is always associated with an
780   anonymous (i.e., unidentified) resource.
781</t>
782<t>
783   In the common case, an HTTP response is a representation of the target
784   resource (see &effective-request-uri;). However, this is not always the
785   case. To determine the URI of the resource a response is associated with,
786   the following rules are used (with the first applicable one being selected):
787</t>
788<t><list style="numbers">
789   <t>If the response status code is 200 or 203 and the request method was GET,
790   the response payload is a representation of the target resource.</t>
791   <t>If the response status code is 204, 206, or 304 and the request method was GET
792   or HEAD, the response payload is a partial representation of the target
793   resource.</t>
794   <t>If the response has a Content-Location header field, and that URI is the same
795   as the effective request URI, the response payload is a representation of the
796   target resource.</t>
797   <t>If the response has a Content-Location header field, and that URI is not the
798   same as the effective request URI, then the response asserts that its
799   payload is a representation of the resource identified by the
800   Content-Location URI. However, such an assertion cannot be trusted unless
801   it can be verified by other means (not defined by HTTP).</t>
802   <t>Otherwise, the response is a representation of an anonymous (i.e.,
803   unidentified) resource.</t>
804</list></t>
805<t>
806  <cref anchor="TODO-req-uri">
807   The comparison function is going to have to be defined somewhere,
808   because we already need to compare URIs for things like cache invalidation.</cref>
809</t>
810</section>
811
812</section>
813
814
815<section title="Method Definitions" anchor="method.definitions">
816<t>
817   The set of common request methods for HTTP/1.1 is defined below. Although
818   this set can be expanded, additional methods cannot be assumed to
819   share the same semantics for separately extended clients and servers.
820</t>
821
822<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
823
824<section title="Safe Methods" anchor="safe.methods">
825<iref item="Safe Methods" primary="true"/>
826<t>
827   Implementors need to be aware that the software represents the user in
828   their interactions over the Internet, and need to allow
829   the user to be aware of any actions they take which might have an
830   unexpected significance to themselves or others.
831</t>
832<t>
833   In particular, the convention has been established that the GET, HEAD,
834   OPTIONS, and TRACE request methods &SHOULD-NOT; have the significance
835   of taking an action other than retrieval. These request methods ought
836   to be considered "<x:dfn anchor="safe">safe</x:dfn>".
837   This allows user agents to represent other methods, such as POST, PUT
838   and DELETE, in a special way, so that the user is made aware of the
839   fact that a possibly unsafe action is being requested.
840</t>
841<t>
842   Naturally, it is not possible to ensure that the server does not
843   generate side-effects as a result of performing a GET request; in
844   fact, some dynamic resources consider that a feature. The important
845   distinction here is that the user did not request the side-effects,
846   so therefore cannot be held accountable for them.
847</t>
848</section>
849
850<section title="Idempotent Methods" anchor="idempotent.methods">
851<iref item="Idempotent Methods" primary="true"/>
852<t>
853   Request methods can also have the property of "idempotence" in that,
854   aside from error or expiration issues, the intended effect of multiple
855   identical requests is the same as for a single request.
856   PUT, DELETE, and all safe request methods are idempotent.
857   It is important to note that idempotence refers only to changes
858   requested by the client: a server is free to change its state due
859   to multiple requests for the purpose of tracking those requests,
860   versioning of results, etc.
861</t>
862</section>
863</section>
864
865<section title="OPTIONS" anchor="OPTIONS">
866  <rdf:Description>
867    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
868  </rdf:Description>
869  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
870  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
871<t>
872   The OPTIONS method requests information about the
873   communication options available on the request/response chain
874   identified by the effective request URI. This method allows a client to
875   determine the options and/or requirements associated with a resource,
876   or the capabilities of a server, without implying a resource action
877   or initiating a resource retrieval.
878</t>
879<t>
880   Responses to the OPTIONS method are not cacheable.
881</t>
882<t>
883   If the OPTIONS request includes a message-body (as indicated by the
884   presence of Content-Length or Transfer-Encoding), then the media type
885   &MUST; be indicated by a Content-Type field. Although this
886   specification does not define any use for such a body, future
887   extensions to HTTP might use the OPTIONS body to make more detailed
888   queries on the server.
889</t>
890<t>
891   If the request-target is an asterisk ("*"), the OPTIONS request is
892   intended to apply to the server in general rather than to a specific
893   resource. Since a server's communication options typically depend on
894   the resource, the "*" request is only useful as a "ping" or "no-op"
895   type of method; it does nothing beyond allowing the client to test
896   the capabilities of the server. For example, this can be used to test
897   a proxy for HTTP/1.1 compliance (or lack thereof).
898</t>
899<t>
900   If the request-target is not an asterisk, the OPTIONS request applies
901   only to the options that are available when communicating with that
902   resource.
903</t>
904<t>
905   A 200 response &SHOULD; include any header fields that indicate
906   optional features implemented by the server and applicable to that
907   resource (e.g., Allow), possibly including extensions not defined by
908   this specification. The response body, if any, &SHOULD; also include
909   information about the communication options. The format for such a
910   body is not defined by this specification, but might be defined by
911   future extensions to HTTP. Content negotiation &MAY; be used to select
912   the appropriate response format. If no response body is included, the
913   response &MUST; include a Content-Length field with a field-value of
914   "0".
915</t>
916<t>
917   The Max-Forwards header field &MAY; be used to target a
918   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
919   If no Max-Forwards field is present in the request, then the forwarded
920   request &MUST-NOT; include a Max-Forwards field.
921</t>
922</section>
923
924<section title="GET" anchor="GET">
925  <rdf:Description>
926    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
927  </rdf:Description>
928  <iref primary="true" item="GET method" x:for-anchor=""/>
929  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
930<t>
931   The GET method requests transfer of a current representation of
932   the target resource.
933</t>
934<t>   
935   If the target resource is a data-producing process, it is the
936   produced data which shall be returned as the representation in the response and not
937   the source text of the process, unless that text happens to be the output of
938   the process.
939</t>
940<t>
941   The semantics of the GET method change to a "conditional GET" if the
942   request message includes an If-Modified-Since, If-Unmodified-Since,
943   If-Match, If-None-Match, or If-Range header field. A conditional GET
944   requests that the representation be transferred only under the
945   circumstances described by the conditional header field(s). The
946   conditional GET request is intended to reduce unnecessary network
947   usage by allowing cached representations to be refreshed without requiring
948   multiple requests or transferring data already held by the client.
949</t>
950<t>
951   The semantics of the GET method change to a "partial GET" if the
952   request message includes a Range header field. A partial GET requests
953   that only part of the representation be transferred, as described in &header-range;.
954   The partial GET request is intended to reduce unnecessary
955   network usage by allowing partially-retrieved representations to be
956   completed without transferring data already held by the client.
957</t>
958<t>
959   Bodies on GET requests have no defined semantics. Note that sending a body
960   on a GET request might cause some existing implementations to reject the
961   request.
962</t>
963<t>
964   The response to a GET request is cacheable and &MAY; be used to satisfy
965   subsequent GET and HEAD requests (see &caching;).
966</t>
967<t>
968   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
969</t>
970</section>
971
972<section title="HEAD" anchor="HEAD">
973  <rdf:Description>
974    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
975  </rdf:Description>
976  <iref primary="true" item="HEAD method" x:for-anchor=""/>
977  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
978<t>
979   The HEAD method is identical to GET except that the server &MUST-NOT;
980   return a message-body in the response. The metadata contained
981   in the HTTP header fields in response to a HEAD request &SHOULD; be identical
982   to the information sent in response to a GET request. This method can
983   be used for obtaining metadata about the representation implied by the
984   request without transferring the representation body. This method is
985   often used for testing hypertext links for validity, accessibility,
986   and recent modification.
987</t>
988<t>
989   The response to a HEAD request is cacheable and &MAY; be used to satisfy
990   a subsequent HEAD request; see &caching;. It also &MAY; be used to update a previously cached
991   representation from that resource; if the new field values
992   indicate that the cached representation differs from the current representation (as
993   would be indicated by a change in Content-Length, ETag
994   or Last-Modified), then the cache &MUST; treat the cache entry as
995   stale.
996</t>
997<t>
998   Bodies on HEAD requests have no defined semantics. Note that sending a body
999   on a HEAD request might cause some existing implementations to reject the
1000   request.
1001</t>
1002</section>
1003
1004<section title="POST" anchor="POST">
1005  <iref primary="true" item="POST method" x:for-anchor=""/>
1006  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
1007<t>
1008   The POST method requests that the origin server accept the
1009   representation enclosed in the request as data to be processed by the
1010   target resource. POST is designed to allow a uniform method to cover the
1011   following functions:
1012  <list style="symbols">
1013    <t>
1014      Annotation of existing resources;
1015    </t>
1016    <t>
1017        Posting a message to a bulletin board, newsgroup, mailing list,
1018        or similar group of articles;
1019    </t>
1020    <t>
1021        Providing a block of data, such as the result of submitting a
1022        form, to a data-handling process;
1023    </t>
1024    <t>
1025        Extending a database through an append operation.
1026    </t>
1027  </list>
1028</t>
1029<t>
1030   The actual function performed by the POST method is determined by the
1031   server and is usually dependent on the effective request URI.
1032</t>
1033<t>
1034   The action performed by the POST method might not result in a
1035   resource that can be identified by a URI. In this case, either 200
1036   (OK) or 204 (No Content) is the appropriate response status code,
1037   depending on whether or not the response includes a representation that
1038   describes the result.
1039</t>
1040<t>
1041   If a resource has been created on the origin server, the response
1042   &SHOULD; be 201 (Created) and contain a representation which describes the
1043   status of the request and refers to the new resource, and a Location
1044   header field (see <xref target="header.location"/>).
1045</t>
1046<t>
1047   Responses to POST requests are only cacheable when they
1048   include explicit freshness information (see &p6-explicit;). A
1049   cached POST response with a Content-Location header field
1050   (see &header-content-location;) whose value is the effective
1051   Request URI &MAY; be used to satisfy subsequent GET and HEAD requests.
1052</t>
1053<t>
1054   Note that POST caching is not widely implemented.
1055   However, the 303 (See Other) response can be used to direct the
1056   user agent to retrieve a cacheable resource.
1057</t>
1058</section>
1059
1060<section title="PUT" anchor="PUT">
1061  <iref primary="true" item="PUT method" x:for-anchor=""/>
1062  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
1063<t>
1064   The PUT method requests that the state of the target resource
1065   be created or replaced with the state defined by the representation
1066   enclosed in the request message payload.  A successful PUT of a given
1067   representation would suggest that a subsequent GET on that same target
1068   resource will result in an equivalent representation being returned in
1069   a 200 (OK) response.  However, there is no guarantee that such a state
1070   change will be observable, since the target resource might be acted
1071   upon by other user agents in parallel, or might be subject to dynamic
1072   processing by the origin server, before any subsequent GET is received.
1073   A successful response only implies that the user agent's intent was
1074   achieved at the time of its processing by the origin server.
1075</t>
1076<t>   
1077   If the target resource does not have a current representation and
1078   the PUT successfully creates one, then the origin server &MUST; inform
1079   the user agent by sending a 201 (Created) response.  If the target
1080   resource does have a current representation and that representation is
1081   successfully modified in accordance with the state of the enclosed
1082   representation, then either a 200 (OK) or 204 (No Content) response
1083   &SHOULD; be sent to indicate successful completion of the request.
1084</t>
1085<t>
1086   Unrecognized header fields &SHOULD; be ignored (i.e., not saved
1087   as part of the resource state).
1088</t>
1089<t>
1090   An origin server &SHOULD; verify that the PUT representation is
1091   consistent with any constraints which the server has for the target
1092   resource that cannot or will not be changed by the PUT.  This is
1093   particularly important when the origin server uses internal
1094   configuration information related to the URI in order to set the
1095   values for representation metadata on GET responses.  When a PUT
1096   representation is inconsistent with the target resource, the origin
1097   server &SHOULD; either make them consistent, by transforming the
1098   representation or changing the resource configuration, or respond
1099   with an appropriate error message containing sufficient information
1100   to explain why the representation is unsuitable.  The 409 (Conflict)
1101   or 415 (Unsupported Media Type) status codes are suggested, with the
1102   latter being specific to constraints on Content-Type values.
1103</t>
1104<t>
1105   For example, if the target resource is configured to always have a
1106   Content-Type of "text/html" and the representation being PUT has a
1107   Content-Type of "image/jpeg", then the origin server &SHOULD; do one of:
1108   (a) reconfigure the target resource to reflect the new media type;
1109   (b) transform the PUT representation to a format consistent with that
1110   of the resource before saving it as the new resource state; or,
1111   (c) reject the request with a 415 response indicating that the target
1112   resource is limited to "text/html", perhaps including a link to a
1113   different resource that would be a suitable target for the new
1114   representation.
1115</t>
1116<t>
1117   HTTP does not define exactly how a PUT method affects the state
1118   of an origin server beyond what can be expressed by the intent of
1119   the user agent request and the semantics of the origin server response.
1120   It does not define what a resource might be, in any sense of that
1121   word, beyond the interface provided via HTTP.  It does not define
1122   how resource state is "stored", nor how such storage might change
1123   as a result of a change in resource state, nor how the origin server
1124   translates resource state into representations.  Generally speaking,
1125   all implementation details behind the resource interface are
1126   intentionally hidden by the server.
1127</t>
1128<t>
1129   The fundamental difference between the POST and PUT methods is
1130   highlighted by the different intent for the target resource.
1131   The target resource in a POST request is intended to handle the
1132   enclosed representation as a data-accepting process, such as for
1133   a gateway to some other protocol or a document that accepts annotations.
1134   In contrast, the target resource in a PUT request is intended to
1135   take the enclosed representation as a new or replacement value.
1136   Hence, the intent of PUT is idempotent and visible to intermediaries,
1137   even though the exact effect is only known by the origin server.
1138</t>
1139<t>
1140   Proper interpretation of a PUT request presumes that the user agent
1141   knows what target resource is desired.  A service that is intended
1142   to select a proper URI on behalf of the client, after receiving
1143   a state-changing request, &SHOULD; be implemented using the POST
1144   method rather than PUT.  If the origin server will not make the
1145   requested PUT state change to the target resource and instead
1146   wishes to have it applied to a different resource, such as when the
1147   resource has been moved to a different URI, then the origin server
1148   &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
1149   then make its own decision regarding whether or not to redirect the
1150   request.
1151</t>
1152<t>
1153   A PUT request applied to the target resource &MAY; have side-effects
1154   on other resources.  For example, an article might have a URI for
1155   identifying "the current version" (a resource) which is separate
1156   from the URIs identifying each particular version (different
1157   resources that at one point shared the same state as the current version
1158   resource).  A successful PUT request on "the current version" URI might
1159   therefore create a new version resource in addition to changing the
1160   state of the target resource, and might also cause links to be added
1161   between the related resources.
1162</t>
1163<t>
1164   An origin server &SHOULD; reject any PUT request that contains a
1165   Content-Range header field, since it might be misinterpreted as
1166   partial content (or might be partial content that is being mistakenly
1167   PUT as a full representation).  Partial content updates are
1168   possible by targeting a separately identified resource with state
1169   that overlaps a portion of the larger resource, or by using a
1170   different method that has been specifically defined for partial
1171   updates (for example, the PATCH method defined in
1172   <xref target="RFC5789"/>).
1173</t>
1174<t>
1175   Responses to the PUT method are not cacheable. If a PUT request passes
1176   through a cache that has one or more stored responses for the effective
1177   request URI, those stored responses will be invalidated (see
1178   &p6-invalid;).
1179</t>
1180</section>
1181
1182<section title="DELETE" anchor="DELETE">
1183  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1184  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1185<t>
1186   The DELETE method requests that the origin server delete the target
1187   resource. This method &MAY; be overridden by
1188   human intervention (or other means) on the origin server. The client cannot
1189   be guaranteed that the operation has been carried out, even if the
1190   status code returned from the origin server indicates that the action
1191   has been completed successfully. However, the server &SHOULD-NOT; 
1192   indicate success unless, at the time the response is given, it
1193   intends to delete the resource or move it to an inaccessible
1194   location.
1195</t>
1196<t>
1197   A successful response &SHOULD; be 200 (OK) if the response includes an
1198   representation describing the status, 202 (Accepted) if the action has not
1199   yet been enacted, or 204 (No Content) if the action has been enacted
1200   but the response does not include a representation.
1201</t>
1202<t>
1203   Bodies on DELETE requests have no defined semantics. Note that sending a body
1204   on a DELETE request might cause some existing implementations to reject the
1205   request.
1206</t>
1207<t>
1208   Responses to the DELETE method are not cacheable. If a DELETE request
1209   passes through a cache that has one or more stored responses for the
1210   effective request URI, those stored responses will be invalidated (see
1211   &p6-invalid;).
1212</t>
1213</section>
1214
1215<section title="TRACE" anchor="TRACE">
1216  <rdf:Description>
1217    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1218  </rdf:Description>
1219  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1220  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1221<t>
1222   The TRACE method requests a remote, application-layer loop-back
1223   of the request message. The final recipient of the request
1224   &SHOULD; reflect the message received back to the client as the
1225   message-body of a 200 (OK) response. The final recipient is either the
1226   origin server or the first proxy to receive a Max-Forwards
1227   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1228   A TRACE request &MUST-NOT; include a message-body.
1229</t>
1230<t>
1231   TRACE allows the client to see what is being received at the other
1232   end of the request chain and use that data for testing or diagnostic
1233   information. The value of the Via header field (&header-via;) is of
1234   particular interest, since it acts as a trace of the request chain.
1235   Use of the Max-Forwards header field allows the client to limit the
1236   length of the request chain, which is useful for testing a chain of
1237   proxies forwarding messages in an infinite loop.
1238</t>
1239<t>
1240   If the request is valid, the response &SHOULD; have a Content-Type of
1241   "message/http" (see &media-type-message-http;) and contain a message-body
1242   that encloses a copy of the entire request message.
1243   Responses to the TRACE method are not cacheable.
1244</t>
1245</section>
1246
1247<section title="CONNECT" anchor="CONNECT">
1248  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1249  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1250<t>
1251   The CONNECT method requests that the proxy establish a tunnel
1252   to the request-target and then restrict its behavior to blind
1253   forwarding of packets until the connection is closed.
1254</t>
1255<t>
1256   When using CONNECT, the request-target &MUST; use the authority form
1257   (&request-target;); i.e., the request-target consists of only the
1258   host name and port number of the tunnel destination, separated by a colon.
1259   For example,
1260</t>
1261<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1262CONNECT server.example.com:80 HTTP/1.1
1263Host: server.example.com:80
1264
1265</artwork></figure>
1266<t>
1267   Other HTTP mechanisms can be used normally with the CONNECT method &mdash;
1268   except end-to-end protocol Upgrade requests, since the
1269   tunnel must be established first.
1270</t>
1271<t>
1272   For example, proxy authentication might be used to establish the
1273   authority to create a tunnel:
1274</t>
1275<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1276CONNECT server.example.com:80 HTTP/1.1
1277Host: server.example.com:80
1278Proxy-Authorization: basic aGVsbG86d29ybGQ=
1279
1280</artwork></figure>
1281<t>
1282   Bodies on CONNECT requests have no defined semantics. Note that sending a body
1283   on a CONNECT request might cause some existing implementations to reject the
1284   request.
1285</t>
1286<t>
1287   Like any other pipelined HTTP/1.1 request, data to be tunnel may be
1288   sent immediately after the blank line. The usual caveats also apply:
1289   data may be discarded if the eventual response is negative, and the
1290   connection may be reset with no response if more than one TCP segment
1291   is outstanding.
1292</t>
1293
1294<section title="Establishing a Tunnel with CONNECT">
1295<t>
1296   Any successful (2xx) response to a CONNECT request indicates that the
1297   proxy has established a connection to the requested host and port,
1298   and has switched to tunneling the current connection to that server
1299   connection.
1300</t>
1301<t>
1302   It may be the case that the proxy itself can only reach the requested
1303   origin server through another proxy.  In this case, the first proxy
1304   &SHOULD; make a CONNECT request of that next proxy, requesting a tunnel
1305   to the authority.  A proxy &MUST-NOT; respond with any 2xx status code
1306   unless it has either a direct or tunnel connection established to the
1307   authority.
1308</t>
1309<t>
1310   An origin server which receives a CONNECT request for itself &MAY;
1311   respond with a 2xx status code to indicate that a connection is
1312   established.
1313</t>
1314<t>
1315   If at any point either one of the peers gets disconnected, any
1316   outstanding data that came from that peer will be passed to the other
1317   one, and after that also the other connection will be terminated by
1318   the proxy. If there is outstanding data to that peer undelivered,
1319   that data will be discarded.
1320</t>
1321
1322</section>
1323</section>
1324</section>
1325
1326
1327<section title="Status Code Definitions" anchor="status.codes">
1328<t>
1329   The first digit of the Status-Code defines the class of response. The
1330   last two digits do not have any categorization role. There are 5
1331   values for the first digit:
1332  <list style="symbols">
1333    <t>
1334      1xx: Informational - Request received, continuing process
1335    </t>
1336    <t>
1337      2xx: Success - The action was successfully received,
1338        understood, and accepted
1339    </t>
1340    <t>
1341      3xx: Redirection - Further action must be taken in order to
1342        complete the request
1343    </t>
1344    <t>
1345      4xx: Client Error - The request contains bad syntax or cannot
1346        be fulfilled
1347    </t>
1348    <t>
1349      5xx: Server Error - The server failed to fulfill an apparently
1350        valid request
1351    </t>
1352  </list>
1353</t>
1354<t>
1355   Each Status-Code is described below, including any metadata required
1356   in the response.
1357</t>
1358
1359<section title="Informational 1xx" anchor="status.1xx">
1360<t>
1361   This class of status code indicates a provisional response,
1362   consisting only of the Status-Line and optional header fields, and is
1363   terminated by an empty line. There are no required header fields for this
1364   class of status code. Since HTTP/1.0 did not define any 1xx status
1365   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1366   except under experimental conditions.
1367</t>
1368<t>
1369   A client &MUST; be prepared to accept one or more 1xx status responses
1370   prior to a regular response, even if the client does not expect a 100
1371   (Continue) status message. Unexpected 1xx status responses &MAY; be
1372   ignored by a user agent.
1373</t>
1374<t>
1375   Proxies &MUST; forward 1xx responses, unless the connection between the
1376   proxy and its client has been closed, or unless the proxy itself
1377   requested the generation of the 1xx response. (For example, if a
1378   proxy adds a "Expect: 100-continue" field when it forwards a request,
1379   then it need not forward the corresponding 100 (Continue)
1380   response(s).)
1381</t>
1382
1383<section title="100 Continue" anchor="status.100">
1384  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1385  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1386<t>
1387   The client &SHOULD; continue with its request. This interim response is
1388   used to inform the client that the initial part of the request has
1389   been received and has not yet been rejected by the server. The client
1390   &SHOULD; continue by sending the remainder of the request or, if the
1391   request has already been completed, ignore this response. The server
1392   &MUST; send a final response after the request has been completed. See
1393   &use100; for detailed discussion of the use and handling of this
1394   status code.
1395</t>
1396</section>
1397
1398<section title="101 Switching Protocols" anchor="status.101">
1399  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1400  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1401<t>
1402   The server understands and is willing to comply with the client's
1403   request, via the Upgrade message header field (&header-upgrade;), for a
1404   change in the application protocol being used on this connection. The
1405   server will switch protocols to those defined by the response's
1406   Upgrade header field immediately after the empty line which
1407   terminates the 101 response.
1408</t>
1409<t>
1410   The protocol &SHOULD; be switched only when it is advantageous to do
1411   so. For example, switching to a newer version of HTTP is advantageous
1412   over older versions, and switching to a real-time, synchronous
1413   protocol might be advantageous when delivering resources that use
1414   such features.
1415</t>
1416</section>
1417</section>
1418
1419<section title="Successful 2xx" anchor="status.2xx">
1420<t>
1421   This class of status code indicates that the client's request was
1422   successfully received, understood, and accepted.
1423</t>
1424
1425<section title="200 OK" anchor="status.200">
1426  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1427  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1428<t>
1429   The request has succeeded. The payload returned with the response
1430   is dependent on the method used in the request, for example:
1431  <list style="hanging">
1432    <t hangText="GET">
1433      a representation of the target resource is sent in the response;
1434    </t>
1435    <t hangText="HEAD">
1436      the same representation as GET, except without the message-body;
1437    </t>
1438    <t hangText="POST">
1439      a representation describing or containing the result of the action;
1440    </t>
1441    <t hangText="TRACE">
1442      a representation containing the request message as received by the
1443      end server.
1444    </t>
1445  </list>
1446</t>
1447<t>
1448   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1449   freshness for 200 responses.
1450</t>
1451</section>
1452
1453<section title="201 Created" anchor="status.201">
1454  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1455  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1456<t>
1457   The request has been fulfilled and has resulted in a new resource being
1458   created. The newly created resource can be referenced by the URI(s)
1459   returned in the payload of the response, with the most specific URI
1460   for the resource given by a Location header field. The response
1461   &SHOULD; include a payload containing a list of resource
1462   characteristics and location(s) from which the user or user agent can
1463   choose the one most appropriate. The payload format is specified by
1464   the media type given in the Content-Type header field. The origin
1465   server &MUST; create the resource before returning the 201 status code.
1466   If the action cannot be carried out immediately, the server &SHOULD;
1467   respond with 202 (Accepted) response instead.
1468</t>
1469<t>
1470   A 201 response &MAY; contain an ETag response header field indicating
1471   the current value of the entity-tag for the representation of the resource
1472   just created (see &header-etag;).
1473</t>
1474</section>
1475
1476<section title="202 Accepted" anchor="status.202">
1477  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1478  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1479<t>
1480   The request has been accepted for processing, but the processing has
1481   not been completed.  The request might or might not eventually be
1482   acted upon, as it might be disallowed when processing actually takes
1483   place. There is no facility for re-sending a status code from an
1484   asynchronous operation such as this.
1485</t>
1486<t>
1487   The 202 response is intentionally non-committal. Its purpose is to
1488   allow a server to accept a request for some other process (perhaps a
1489   batch-oriented process that is only run once per day) without
1490   requiring that the user agent's connection to the server persist
1491   until the process is completed. The representation returned with this
1492   response &SHOULD; include an indication of the request's current status
1493   and either a pointer to a status monitor or some estimate of when the
1494   user can expect the request to be fulfilled.
1495</t>
1496</section>
1497
1498<section title="203 Non-Authoritative Information" anchor="status.203">
1499  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1500  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1501<t>
1502   The representation in the response has been transformed or otherwise
1503   modified by a transforming proxy (&intermediaries;).  Note that the
1504   behaviour of transforming intermediaries is controlled by the no-transform
1505   Cache-Control directive (&header-cache-control;).
1506</t>
1507<t>
1508   This status code is only appropriate when the response status code would
1509   have been 200 (OK) otherwise. When the status code before transformation
1510   would have been different, the 214 Transformation Applied warn-code
1511   (&header-warning;) is appropriate.
1512</t>
1513<t>
1514   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1515   freshness for 203 responses.
1516</t>
1517</section>
1518
1519<section title="204 No Content" anchor="status.204">
1520  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1521  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1522<t>
1523   The 204 (No Content) status code indicates that the server has
1524   successfully fulfilled the request and that there is no additional
1525   content to return in the response payload body.  Metadata in the
1526   response header fields refer to the target resource and its current
1527   representation after the requested action.
1528</t>
1529<t>
1530   For example, if a 204 status code is received in response to a PUT
1531   request and the response contains an ETag header field, then the PUT
1532   was successful and the ETag field-value contains the entity-tag for
1533   the new representation of that target resource.
1534</t>
1535<t>
1536   The 204 response allows a server to indicate that the action has been
1537   successfully applied to the target resource while implying that the
1538   user agent &SHOULD-NOT; traverse away from its current "document view"
1539   (if any).  The server assumes that the user agent will provide some
1540   indication of the success to its user, in accord with its own interface,
1541   and apply any new or updated metadata in the response to the active
1542   representation.
1543</t>
1544<t>
1545   For example, a 204 status code is commonly used with document editing
1546   interfaces corresponding to a "save" action, such that the document
1547   being saved remains available to the user for editing. It is also
1548   frequently used with interfaces that expect automated data transfers
1549   to be prevalent, such as within distributed version control systems.
1550</t>
1551<t>
1552   The 204 response &MUST-NOT; include a message-body, and thus is always
1553   terminated by the first empty line after the header fields.
1554</t>
1555</section>
1556
1557<section title="205 Reset Content" anchor="status.205">
1558  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1559  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1560<t>
1561   The server has fulfilled the request and the user agent &SHOULD; reset
1562   the document view which caused the request to be sent. This response
1563   is primarily intended to allow input for actions to take place via
1564   user input, followed by a clearing of the form in which the input is
1565   given so that the user can easily initiate another input action.
1566</t>
1567<t>   
1568   The message-body included with the response &MUST; be empty. Note that
1569   receivers still need to parse the response according to the algorithm defined
1570   in &message-body;.
1571</t>
1572</section>
1573
1574<section title="206 Partial Content" anchor="status.206">
1575  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1576  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1577  <rdf:Description>
1578    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1579  </rdf:Description>
1580<t>
1581   The server has fulfilled the partial GET request for the resource
1582   and the enclosed payload is a partial representation as defined in &status-206;.
1583</t>
1584<t>
1585   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1586   freshness for 206 responses.
1587</t>
1588</section>
1589</section>
1590
1591<section title="Redirection 3xx" anchor="status.3xx">
1592<t>
1593   This class of status code indicates that further action needs to be
1594   taken by the user agent in order to fulfill the request.  If the required
1595   action involves a subsequent HTTP request, it &MAY; be carried out by the
1596   user agent without interaction with the user if and only if the method used
1597   in the second request is known to be "safe", as defined in
1598   <xref target="safe.methods"/>.
1599</t>
1600<t>
1601   There are several types of redirects:
1602   <list style="numbers">
1603      <x:lt>
1604        <t>
1605          Redirects of the request to another URI, either temporarily or
1606          permanently. The new URI is specified in the Location header field.
1607          In this specification, the status codes 301 (Moved Permanently),
1608          302 (Found), and 307 (Temporary Redirect) fall under this category.
1609        </t>
1610      </x:lt>
1611      <x:lt>
1612        <t>
1613          Redirection to a new location that represents an indirect response to
1614          the request, such as the result of a POST operation to be retrieved
1615          with a subsequent GET request. This is status code 303 (See Other).
1616        </t>
1617      </x:lt>
1618      <x:lt>
1619        <t>
1620          Redirection offering a choice of matching resources for use by
1621          agent-driven content negotiation (&agent-driven-negotiation;). This
1622          is status code 300 (Multiple Choices).
1623        </t>
1624      </x:lt>
1625      <x:lt>
1626        <t>
1627          Other kinds of redirection, such as to a cached result (status code 304
1628          (Not Modified)).
1629        </t>
1630      </x:lt>
1631   </list>
1632</t>
1633<x:note>
1634  <t>
1635    <x:h>Note:</x:h> In HTTP/1.0, only the status codes 301 (Moved Permanently)
1636    and 302 (Found) were defined for the first type of redirect, and the second
1637    type did not exist at all (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>).
1638    However it turned out that web forms using POST expected redirects to change
1639    the operation for the subsequent request to retrieval (GET). To address this
1640    use case, HTTP/1.1 introduced the second type of redirect with the status
1641    code 303 (See Other) (<xref target="RFC2068" x:fmt="," x:sec="10.3.4"/>).
1642    As user agents did not change their behavior to maintain backwards
1643    compatibility, the first revision of HTTP/1.1 added yet another status code,
1644    307 (Temporary Redirect), for which the backwards compatibility problems did
1645    not apply (<xref target="RFC2616" x:fmt="," x:sec="10.3.8"/>).
1646    Over 10 years later, most user agents still do method rewriting for
1647    status codes 301 and 302, therefore this specification makes that behavior
1648    compliant in case the original request was POST.
1649  </t>
1650</x:note>
1651<t>
1652   Clients &SHOULD; detect and intervene in cyclical redirections (i.e.,
1653   "infinite" redirection loops).
1654</t>
1655<x:note>
1656  <t>
1657    <x:h>Note:</x:h> An earlier version of this specification recommended a
1658    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1659    Content developers need to be aware that some clients might
1660    implement such a fixed limitation.
1661  </t>
1662</x:note>
1663
1664<section title="300 Multiple Choices" anchor="status.300">
1665  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1666  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1667<t>
1668   The target resource has more than one
1669   representation, each with its own specific location, and agent-driven
1670   negotiation information (&content-negotiation;) is being provided so that
1671   the user (or user agent) can select a preferred representation by
1672   redirecting its request to that location.
1673</t>
1674<t>
1675   Unless it was a HEAD request, the response &SHOULD; include a representation
1676   containing a list of representation metadata and location(s) from
1677   which the user or user agent can choose the one most appropriate. The
1678   data format is specified by the media type given in the Content-Type
1679   header field. Depending upon the format and the capabilities of
1680   the user agent, selection of the most appropriate choice &MAY; be
1681   performed automatically. However, this specification does not define
1682   any standard for such automatic selection.
1683</t>
1684<t>
1685   If the server has a preferred choice of representation, it &SHOULD;
1686   include the specific URI for that representation in the Location
1687   field; user agents &MAY; use the Location field value for automatic
1688   redirection.
1689</t>
1690<t>
1691   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1692   freshness for 300 responses.
1693</t>
1694
1695</section>
1696
1697<section title="301 Moved Permanently" anchor="status.301">
1698  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1699  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1700<t>
1701   The target resource has been assigned a new permanent URI and any
1702   future references to this resource &SHOULD; use one of the returned
1703   URIs.  Clients with link editing capabilities ought to automatically
1704   re-link references to the effective request URI to one or more of the new
1705   references returned by the server, where possible.
1706</t>
1707<t>
1708   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1709   freshness for 301 responses.
1710</t>
1711<t>
1712   The new permanent URI &SHOULD; be given by the Location field in the
1713   response. Unless the request method was HEAD, the representation of the
1714   response &SHOULD; contain a short hypertext note with a hyperlink to
1715   the new URI(s).
1716</t>
1717<t>
1718   If the 301 status code is received in response to a request method
1719   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1720   then the request &MAY; be automatically redirected by the user agent without
1721   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1722   request unless it can be confirmed by the user, since this might
1723   change the conditions under which the request was issued.
1724</t>
1725<x:note>
1726  <t>
1727    <x:h>Note:</x:h> For historic reasons, user agents &MAY; change the
1728    request method from POST to GET for the subsequent request. If this
1729    behavior is undesired, status code 307 (Temporary Redirect) can be used
1730    instead.
1731  </t>
1732</x:note>
1733</section>
1734
1735<section title="302 Found" anchor="status.302">
1736  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1737  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1738<t>
1739   The target resource resides temporarily under a different URI.
1740   Since the redirection might be altered on occasion, the client &SHOULD;
1741   continue to use the effective request URI for future requests.
1742</t>
1743<t>
1744   The temporary URI &SHOULD; be given by the Location field in the
1745   response. Unless the request method was HEAD, the representation of the
1746   response &SHOULD; contain a short hypertext note with a hyperlink to
1747   the new URI(s).
1748</t>
1749<t>
1750   If the 302 status code is received in response to a request method
1751   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1752   then the request &MAY; be automatically redirected by the user agent without
1753   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1754   request unless it can be confirmed by the user, since this might
1755   change the conditions under which the request was issued.
1756</t>
1757<x:note>
1758  <t>
1759    <x:h>Note:</x:h> For historic reasons, user agents &MAY; change the
1760    request method from POST to GET for the subsequent request. If this
1761    behavior is undesired, status code 307 (Temporary Redirect) can be used
1762    instead.
1763    <cref anchor="issue312">but see <eref target="http://trac.tools.ietf.org/wg/httpbis/trac/ticket/312"/></cref>
1764  </t>
1765</x:note>
1766</section>
1767
1768<section title="303 See Other" anchor="status.303">
1769  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1770  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1771<t>
1772   The 303 status code indicates that the server is redirecting the
1773   user agent to a different resource, as indicated by a URI in the
1774   Location header field, that is intended to provide an indirect
1775   response to the original request.  In order to satisfy the original
1776   request, a user agent &SHOULD; perform a retrieval request using the
1777   Location URI (a GET or HEAD request if using HTTP), which
1778   may itself be redirected further, and present the eventual result as an
1779   answer to the original request.
1780   Note that the new URI in the Location header field is not considered
1781   equivalent to the effective request URI.
1782</t>
1783<t>
1784   This status code is generally applicable to any HTTP method.  It is
1785   primarily used to allow the output of a POST action to redirect
1786   the user agent to a selected resource, since doing so provides the
1787   information corresponding to the POST response in a form that
1788   can be separately identified, bookmarked, and cached independent
1789   of the original request.
1790</t>
1791<t>
1792   A 303 response to a GET request indicates that the requested
1793   resource does not have a representation of its own that can be
1794   transferred by the server over HTTP.  The Location URI indicates a
1795   resource that is descriptive of the target resource, such that the
1796   follow-on representation might be useful to recipients without
1797   implying that it adequately represents the target resource.
1798   Note that answers to the questions of what can be represented, what
1799   representations are adequate, and what might be a useful description
1800   are outside the scope of HTTP and thus entirely determined by the
1801   URI owner(s).
1802</t>
1803<t>
1804   Except for responses to a HEAD request, the representation of a 303
1805   response &SHOULD; contain a short hypertext note with a hyperlink
1806   to the Location URI.
1807</t>
1808</section>
1809
1810<section title="304 Not Modified" anchor="status.304">
1811  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1812  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1813  <rdf:Description>
1814    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1815  </rdf:Description>
1816<t>
1817   The response to the request has not been modified since the conditions
1818   indicated by the client's conditional GET request, as defined in &status-304;.
1819</t>
1820</section>
1821
1822<section title="305 Use Proxy" anchor="status.305">
1823  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1824  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1825<t>
1826   The 305 status code was defined in a previous version of this specification
1827   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1828</t>
1829</section>
1830
1831<section title="306 (Unused)" anchor="status.306">
1832  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1833  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1834<t>
1835   The 306 status code was used in a previous version of the
1836   specification, is no longer used, and the code is reserved.
1837</t>
1838</section>
1839
1840<section title="307 Temporary Redirect" anchor="status.307">
1841  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1842  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1843<t>
1844   The target resource resides temporarily under a different URI.
1845   Since the redirection can change over time, the client &SHOULD;
1846   continue to use the effective request URI for future requests.
1847</t>
1848<t>
1849   The temporary URI &SHOULD; be given by the Location field in the
1850   response. Unless the request method was HEAD, the representation of the
1851   response &SHOULD; contain a short hypertext note with a hyperlink to
1852   the new URI(s), since many pre-HTTP/1.1 user agents do not
1853   understand the 307 status code. Therefore, the note &SHOULD; contain the
1854   information necessary for a user to repeat the original request on
1855   the new URI.
1856</t>
1857<t>
1858   If the 307 status code is received in response to a request method
1859   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1860   then the request &MAY; be automatically redirected by the user agent without
1861   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1862   request unless it can be confirmed by the user, since this might
1863   change the conditions under which the request was issued.
1864</t>
1865</section>
1866</section>
1867
1868<section title="Client Error 4xx" anchor="status.4xx">
1869<t>
1870   The 4xx class of status code is intended for cases in which the
1871   client seems to have erred. Except when responding to a HEAD request,
1872   the server &SHOULD; include a representation containing an explanation of the
1873   error situation, and whether it is a temporary or permanent
1874   condition. These status codes are applicable to any request method.
1875   User agents &SHOULD; display any included representation to the user.
1876</t>
1877<t>
1878   If the client is sending data, a server implementation using TCP
1879   &SHOULD; be careful to ensure that the client acknowledges receipt of
1880   the packet(s) containing the response, before the server closes the
1881   input connection. If the client continues sending data to the server
1882   after the close, the server's TCP stack will send a reset packet to
1883   the client, which might erase the client's unacknowledged input buffers
1884   before they can be read and interpreted by the HTTP application.
1885</t>
1886
1887<section title="400 Bad Request" anchor="status.400">
1888  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1889  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1890<t>
1891   The server cannot or will not process the request, due to a client error (e.g.,
1892   malformed syntax).</t>
1893</section>
1894
1895<section title="401 Unauthorized" anchor="status.401">
1896  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1897  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1898  <rdf:Description>
1899    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1900  </rdf:Description>
1901<t>
1902   The request requires user authentication (see &status-401;).
1903</t>
1904</section>
1905
1906<section title="402 Payment Required" anchor="status.402">
1907  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1908  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1909<t>
1910   This code is reserved for future use.
1911</t>
1912</section>
1913
1914<section title="403 Forbidden" anchor="status.403">
1915  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1916  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1917<t>
1918   The server understood the request, but refuses to authorize it. Providing
1919   different user authentication credentials might be successful, but any
1920   credentials that were provided in the request are insufficient. The request
1921   &SHOULD-NOT; be repeated with the same credentials.
1922</t>
1923<t>
1924   If the request method was not HEAD and the server wishes to make
1925   public why the request has not been fulfilled, it &SHOULD; describe the
1926   reason for the refusal in the representation.  If the server does not wish to
1927   make this information available to the client, the status code 404
1928   (Not Found) &MAY; be used instead.
1929</t>
1930</section>
1931
1932<section title="404 Not Found" anchor="status.404">
1933  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1934  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1935<t>
1936   The server has not found anything matching the effective request URI. No
1937   indication is given of whether the condition is temporary or
1938   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1939   knows, through some internally configurable mechanism, that an old
1940   resource is permanently unavailable and has no forwarding address.
1941   This status code is commonly used when the server does not wish to
1942   reveal exactly why the request has been refused, or when no other
1943   response is applicable.
1944</t>
1945</section>
1946
1947<section title="405 Method Not Allowed" anchor="status.405">
1948  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1949  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1950<t>
1951   The method specified in the Request-Line is not allowed for the target
1952   resource. The response &MUST; include an Allow header field containing a
1953   list of valid methods for the requested resource.
1954</t>
1955</section>
1956
1957<section title="406 Not Acceptable" anchor="status.406">
1958  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1959  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1960<t>
1961   The resource identified by the request is only capable of generating
1962   response representations which have content characteristics not acceptable
1963   according to the Accept and Accept-* header fields sent in the request
1964   (see &p3-header-fields;).
1965</t>
1966<t>
1967   Unless it was a HEAD request, the response &SHOULD; include a representation
1968   containing a list of available representation characteristics and location(s)
1969   from which the user or user agent can choose the one most
1970   appropriate. The data format is specified by the media type given
1971   in the Content-Type header field. Depending upon the format and the
1972   capabilities of the user agent, selection of the most appropriate
1973   choice &MAY; be performed automatically. However, this specification
1974   does not define any standard for such automatic selection.
1975</t>
1976<x:note>
1977  <t>
1978    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1979    not acceptable according to the accept header fields sent in the
1980    request. In some cases, this might even be preferable to sending a
1981    406 response. User agents are encouraged to inspect the header fields of
1982    an incoming response to determine if it is acceptable.
1983  </t>
1984</x:note>
1985<t>
1986   If the response could be unacceptable, a user agent &SHOULD;
1987   temporarily stop receipt of more data and query the user for a
1988   decision on further actions.
1989</t>
1990</section>
1991
1992<section title="407 Proxy Authentication Required" anchor="status.407">
1993  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1994  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1995<t>
1996   This code is similar to 401 (Unauthorized), but indicates that the
1997   client must first authenticate itself with the proxy (see &status-407;).
1998</t>
1999</section>
2000
2001<section title="408 Request Timeout" anchor="status.408">
2002  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
2003  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
2004<t>
2005   The client did not produce a request within the time that the server
2006   was prepared to wait. The client &MAY; repeat the request without
2007   modifications at any later time.
2008</t>
2009</section>
2010
2011<section title="409 Conflict" anchor="status.409">
2012  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
2013  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
2014<t>
2015   The request could not be completed due to a conflict with the current
2016   state of the resource. This code is only allowed in situations where
2017   it is expected that the user might be able to resolve the conflict
2018   and resubmit the request. The response body &SHOULD; include enough
2019   information for the user to recognize the source of the conflict.
2020   Ideally, the response representation would include enough information for the
2021   user or user agent to fix the problem; however, that might not be
2022   possible and is not required.
2023</t>
2024<t>
2025   Conflicts are most likely to occur in response to a PUT request. For
2026   example, if versioning were being used and the representation being PUT
2027   included changes to a resource which conflict with those made by an
2028   earlier (third-party) request, the server might use the 409 response
2029   to indicate that it can't complete the request. In this case, the
2030   response representation would likely contain a list of the differences
2031   between the two versions in a format defined by the response
2032   Content-Type.
2033</t>
2034</section>
2035
2036<section title="410 Gone" anchor="status.410">
2037  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
2038  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
2039<t>
2040   The target resource is no longer available at the server and no
2041   forwarding address is known. This condition is expected to be
2042   considered permanent. Clients with link editing capabilities &SHOULD;
2043   delete references to the effective request URI after user approval. If the
2044   server does not know, or has no facility to determine, whether or not
2045   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
2046   used instead.
2047</t>
2048<t>
2049   The 410 response is primarily intended to assist the task of web
2050   maintenance by notifying the recipient that the resource is
2051   intentionally unavailable and that the server owners desire that
2052   remote links to that resource be removed. Such an event is common for
2053   limited-time, promotional services and for resources belonging to
2054   individuals no longer working at the server's site. It is not
2055   necessary to mark all permanently unavailable resources as "gone" or
2056   to keep the mark for any length of time &mdash; that is left to the
2057   discretion of the server owner.
2058</t>
2059<t>
2060   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine freshness
2061   for 410 responses.
2062</t>
2063
2064</section>
2065
2066<section title="411 Length Required" anchor="status.411">
2067  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
2068  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
2069<t>
2070   The server refuses to accept the request without a defined Content-Length.
2071   The client &MAY; repeat the request if it adds a valid
2072   Content-Length header field containing the length of the message-body
2073   in the request message.
2074</t>
2075</section>
2076
2077<section title="412 Precondition Failed" anchor="status.412">
2078  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
2079  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
2080  <rdf:Description>
2081    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
2082  </rdf:Description>
2083<t>
2084   The precondition given in one or more of the header fields
2085   evaluated to false when it was tested on the server, as defined in
2086   &status-412;.
2087</t>
2088</section>
2089
2090<section title="413 Request Representation Too Large" anchor="status.413">
2091  <iref primary="true" item="413 Request Representation Too Large (status code)" x:for-anchor=""/>
2092  <iref primary="true" item="Status Codes" subitem="413 Request Representation Too Large" x:for-anchor=""/>
2093<t>
2094   The server is refusing to process a request because the request
2095   representation is larger than the server is willing or able to process. The
2096   server &MAY; close the connection to prevent the client from continuing
2097   the request.
2098</t>
2099<t>
2100   If the condition is temporary, the server &SHOULD; include a Retry-After
2101   header field to indicate that it is temporary and after what
2102   time the client &MAY; try again.
2103</t>
2104</section>
2105
2106<section title="414 URI Too Long" anchor="status.414">
2107  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
2108  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
2109<t>
2110   The server is refusing to service the request because the effective request URI
2111   is longer than the server is willing to interpret. This rare
2112   condition is only likely to occur when a client has improperly
2113   converted a POST request to a GET request with long query
2114   information, when the client has descended into a URI "black hole" of
2115   redirection (e.g., a redirected URI prefix that points to a suffix of
2116   itself), or when the server is under attack by a client attempting to
2117   exploit security holes present in some servers using fixed-length
2118   buffers for reading or manipulating the effective request URI.
2119</t>
2120</section>
2121
2122<section title="415 Unsupported Media Type" anchor="status.415">
2123  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
2124  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
2125<t>
2126   The server is refusing to service the request because the request
2127   payload is in a format not supported by this request method on the
2128   target resource.
2129</t>
2130</section>
2131
2132<section title="416 Requested Range Not Satisfiable" anchor="status.416">
2133  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
2134  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
2135  <rdf:Description>
2136    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
2137  </rdf:Description>
2138<t>
2139   The request included a Range header field (&header-range;) and none of
2140   the range-specifier values in this field overlap the current extent
2141   of the selected resource. See &status-416;.
2142</t>
2143</section>
2144
2145<section title="417 Expectation Failed" anchor="status.417">
2146  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
2147  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
2148<t>
2149   The expectation given in an Expect header field (see <xref target="header.expect"/>)
2150   could not be met by this server, or, if the server is a proxy,
2151   the server has unambiguous evidence that the request could not be met
2152   by the next-hop server.
2153</t>
2154</section>
2155
2156<section title="426 Upgrade Required" anchor="status.426">
2157  <iref primary="true" item="426 Upgrade Required (status code)" x:for-anchor=""/>
2158  <iref primary="true" item="Status Codes" subitem="426 Upgrade Required" x:for-anchor=""/>
2159<t>
2160   The request can not be completed without a prior protocol upgrade. This
2161   response &MUST; include an Upgrade header field (&header-upgrade;)
2162   specifying the required protocols.
2163</t>
2164<figure>
2165<preamble>Example:</preamble>
2166<artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
2167HTTP/1.1 426 Upgrade Required
2168Upgrade: HTTP/2.0
2169Connection: Upgrade
2170
2171</artwork></figure>
2172<t>
2173   The server &SHOULD; include a message body in the 426 response which
2174   indicates in human readable form the reason for the error and describes any
2175   alternative courses which may be available to the user.
2176</t>
2177</section>
2178</section>
2179
2180<section title="Server Error 5xx" anchor="status.5xx">
2181<t>
2182   Response status codes beginning with the digit "5" indicate cases in
2183   which the server is aware that it has erred or is incapable of
2184   performing the request. Except when responding to a HEAD request, the
2185   server &SHOULD; include a representation containing an explanation of the
2186   error situation, and whether it is a temporary or permanent
2187   condition. User agents &SHOULD; display any included representation to the
2188   user. These response codes are applicable to any request method.
2189</t>
2190
2191<section title="500 Internal Server Error" anchor="status.500">
2192  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
2193  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
2194<t>
2195   The server encountered an unexpected condition which prevented it
2196   from fulfilling the request.
2197</t>
2198</section>
2199
2200<section title="501 Not Implemented" anchor="status.501">
2201  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
2202  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
2203<t>
2204   The server does not support the functionality required to fulfill the
2205   request. This is the appropriate response when the server does not
2206   recognize the request method and is not capable of supporting it for
2207   any resource.
2208</t>
2209</section>
2210
2211<section title="502 Bad Gateway" anchor="status.502">
2212  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
2213  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
2214<t>
2215   The server, while acting as a gateway or proxy, received an invalid
2216   response from the upstream server it accessed in attempting to
2217   fulfill the request.
2218</t>
2219</section>
2220
2221<section title="503 Service Unavailable" anchor="status.503">
2222  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
2223  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
2224<t>
2225   The server is currently unable or unwilling to handle the request due to
2226   reasons such as temporary overloading, maintenance of the server, or rate
2227   limiting of the client.
2228</t>
2229<t>
2230   The implication is that this is a temporary condition which will be
2231   alleviated after some delay. If known, the length of the delay &MAY; be
2232   indicated in a Retry-After header field (<xref target="header.retry-after"/>).
2233   If no Retry-After is given, the client &SHOULD; handle the response as it
2234   would for a 500 response.
2235</t>
2236<x:note>
2237  <t>
2238    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
2239    server must use it when becoming overloaded. Some servers might wish
2240    to simply refuse the connection.
2241  </t>
2242</x:note>
2243</section>
2244
2245<section title="504 Gateway Timeout" anchor="status.504">
2246  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
2247  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
2248<t>
2249   The server, while acting as a gateway or proxy, did not receive a
2250   timely response from the upstream server specified by the URI (e.g.,
2251   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
2252   to access in attempting to complete the request.
2253</t>
2254<x:note>
2255  <t>
2256    <x:h>Note</x:h> to implementors: some deployed proxies are known to
2257    return 400 or 500 when DNS lookups time out.
2258  </t>
2259</x:note>
2260</section>
2261
2262<section title="505 HTTP Version Not Supported" anchor="status.505">
2263  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
2264  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
2265<t>
2266   The server does not support, or refuses to support, the protocol
2267   version that was used in the request message. The server is
2268   indicating that it is unable or unwilling to complete the request
2269   using the same major version as the client, as described in &http-version;,
2270   other than with this error message. The response &SHOULD; contain
2271   a representation describing why that version is not supported and what other
2272   protocols are supported by that server.
2273</t>
2274
2275</section>
2276</section>
2277</section>
2278
2279
2280<section title="Date/Time Formats" anchor="http.date">
2281  <x:anchor-alias value="HTTP-date"/>
2282<t>
2283   HTTP applications have historically allowed three different formats
2284   for date/time stamps. However, the preferred format is a fixed-length subset
2285   of that defined by <xref target="RFC1123"/>:
2286</t>
2287<figure><artwork type="example" x:indent-with="  ">
2288Sun, 06 Nov 1994 08:49:37 GMT  ; RFC 1123
2289</artwork></figure>
2290<t>
2291   The other formats are described here only for compatibility with obsolete
2292   implementations.
2293</t>
2294<figure><artwork type="example" x:indent-with="  ">
2295Sunday, 06-Nov-94 08:49:37 GMT ; obsolete RFC 850 format
2296Sun Nov  6 08:49:37 1994       ; ANSI C's asctime() format
2297</artwork></figure>
2298<t>
2299   HTTP/1.1 clients and servers that parse a date value &MUST; accept
2300   all three formats (for compatibility with HTTP/1.0), though they &MUST;
2301   only generate the RFC 1123 format for representing HTTP-date values
2302   in header fields.
2303</t>
2304<t>
2305   All HTTP date/time stamps &MUST; be represented in Greenwich Mean Time
2306   (GMT), without exception. For the purposes of HTTP, GMT is exactly
2307   equal to UTC (Coordinated Universal Time). This is indicated in the
2308   first two formats by the inclusion of "GMT" as the three-letter
2309   abbreviation for time zone, and &MUST; be assumed when reading the
2310   asctime format. HTTP-date is case sensitive and &MUST-NOT; include
2311   additional whitespace beyond that specifically included as SP in the
2312   grammar.
2313</t>
2314<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="HTTP-date"/>
2315  <x:ref>HTTP-date</x:ref>    = <x:ref>rfc1123-date</x:ref> / <x:ref>obs-date</x:ref>
2316</artwork></figure>
2317<t anchor="preferred.date.format">
2318  <x:anchor-alias value="rfc1123-date"/>
2319  <x:anchor-alias value="time-of-day"/>
2320  <x:anchor-alias value="hour"/>
2321  <x:anchor-alias value="minute"/>
2322  <x:anchor-alias value="second"/>
2323  <x:anchor-alias value="day-name"/>
2324  <x:anchor-alias value="day"/>
2325  <x:anchor-alias value="month"/>
2326  <x:anchor-alias value="year"/>
2327  <x:anchor-alias value="GMT"/>
2328  Preferred format:
2329</t>
2330<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"/>
2331  <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>
2332  ; fixed length subset of the format defined in
2333  ; <xref target="RFC1123" x:fmt="of" x:sec="5.2.14"/>
2334 
2335  <x:ref>day-name</x:ref>     = <x:abnf-char-sequence>"Mon"</x:abnf-char-sequence> ; "Mon", case-sensitive
2336               / <x:abnf-char-sequence>"Tue"</x:abnf-char-sequence> ; "Tue", case-sensitive
2337               / <x:abnf-char-sequence>"Wed"</x:abnf-char-sequence> ; "Wed", case-sensitive
2338               / <x:abnf-char-sequence>"Thu"</x:abnf-char-sequence> ; "Thu", case-sensitive
2339               / <x:abnf-char-sequence>"Fri"</x:abnf-char-sequence> ; "Fri", case-sensitive
2340               / <x:abnf-char-sequence>"Sat"</x:abnf-char-sequence> ; "Sat", case-sensitive
2341               / <x:abnf-char-sequence>"Sun"</x:abnf-char-sequence> ; "Sun", case-sensitive
2342               
2343  <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>
2344               ; e.g., 02 Jun 1982
2345
2346  <x:ref>day</x:ref>          = 2<x:ref>DIGIT</x:ref>
2347  <x:ref>month</x:ref>        = <x:abnf-char-sequence>"Jan"</x:abnf-char-sequence> ; "Jan", case-sensitive
2348               / <x:abnf-char-sequence>"Feb"</x:abnf-char-sequence> ; "Feb", case-sensitive
2349               / <x:abnf-char-sequence>"Mar"</x:abnf-char-sequence> ; "Mar", case-sensitive
2350               / <x:abnf-char-sequence>"Apr"</x:abnf-char-sequence> ; "Apr", case-sensitive
2351               / <x:abnf-char-sequence>"May"</x:abnf-char-sequence> ; "May", case-sensitive
2352               / <x:abnf-char-sequence>"Jun"</x:abnf-char-sequence> ; "Jun", case-sensitive
2353               / <x:abnf-char-sequence>"Jul"</x:abnf-char-sequence> ; "Jul", case-sensitive
2354               / <x:abnf-char-sequence>"Aug"</x:abnf-char-sequence> ; "Aug", case-sensitive
2355               / <x:abnf-char-sequence>"Sep"</x:abnf-char-sequence> ; "Sep", case-sensitive
2356               / <x:abnf-char-sequence>"Oct"</x:abnf-char-sequence> ; "Oct", case-sensitive
2357               / <x:abnf-char-sequence>"Nov"</x:abnf-char-sequence> ; "Nov", case-sensitive
2358               / <x:abnf-char-sequence>"Dec"</x:abnf-char-sequence> ; "Dec", case-sensitive
2359  <x:ref>year</x:ref>         = 4<x:ref>DIGIT</x:ref>
2360
2361  <x:ref>GMT</x:ref>   = <x:abnf-char-sequence>"GMT"</x:abnf-char-sequence> ; "GMT", case-sensitive
2362
2363  <x:ref>time-of-day</x:ref>  = <x:ref>hour</x:ref> ":" <x:ref>minute</x:ref> ":" <x:ref>second</x:ref>
2364                 ; 00:00:00 - 23:59:59
2365                 
2366  <x:ref>hour</x:ref>         = 2<x:ref>DIGIT</x:ref>               
2367  <x:ref>minute</x:ref>       = 2<x:ref>DIGIT</x:ref>               
2368  <x:ref>second</x:ref>       = 2<x:ref>DIGIT</x:ref>               
2369</artwork></figure>
2370<t>
2371  The semantics of <x:ref>day-name</x:ref>, <x:ref>day</x:ref>,
2372  <x:ref>month</x:ref>, <x:ref>year</x:ref>, and <x:ref>time-of-day</x:ref> are the
2373  same as those defined for the RFC 5322 constructs
2374  with the corresponding name (<xref target="RFC5322" x:fmt="," x:sec="3.3"/>).
2375</t>
2376<t anchor="obsolete.date.formats">
2377  <x:anchor-alias value="obs-date"/>
2378  <x:anchor-alias value="rfc850-date"/>
2379  <x:anchor-alias value="asctime-date"/>
2380  <x:anchor-alias value="date1"/>
2381  <x:anchor-alias value="date2"/>
2382  <x:anchor-alias value="date3"/>
2383  <x:anchor-alias value="rfc1123-date"/>
2384  <x:anchor-alias value="day-name-l"/>
2385  Obsolete formats:
2386</t>
2387<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="obs-date"/>
2388  <x:ref>obs-date</x:ref>     = <x:ref>rfc850-date</x:ref> / <x:ref>asctime-date</x:ref> 
2389</artwork></figure>
2390<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="rfc850-date"/>
2391  <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>
2392  <x:ref>date2</x:ref>        = <x:ref>day</x:ref> "-" <x:ref>month</x:ref> "-" 2<x:ref>DIGIT</x:ref>
2393                 ; day-month-year (e.g., 02-Jun-82)
2394
2395  <x:ref>day-name-l</x:ref>   = <x:abnf-char-sequence>"Monday"</x:abnf-char-sequence> ; "Monday", case-sensitive
2396         / <x:abnf-char-sequence>"Tuesday"</x:abnf-char-sequence> ; "Tuesday", case-sensitive
2397         / <x:abnf-char-sequence>"Wednesday"</x:abnf-char-sequence> ; "Wednesday", case-sensitive
2398         / <x:abnf-char-sequence>"Thursday"</x:abnf-char-sequence> ; "Thursday", case-sensitive
2399         / <x:abnf-char-sequence>"Friday"</x:abnf-char-sequence> ; "Friday", case-sensitive
2400         / <x:abnf-char-sequence>"Saturday"</x:abnf-char-sequence> ; "Saturday", case-sensitive
2401         / <x:abnf-char-sequence>"Sunday"</x:abnf-char-sequence> ; "Sunday", case-sensitive
2402</artwork></figure>
2403<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="asctime-date"/>
2404  <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>
2405  <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> ))
2406                 ; month day (e.g., Jun  2)
2407</artwork></figure>
2408<x:note>
2409  <t>
2410    <x:h>Note:</x:h> Recipients of date values are encouraged to be robust in
2411    accepting date values that might have been sent by non-HTTP
2412    applications, as is sometimes the case when retrieving or posting
2413    messages via proxies/gateways to SMTP or NNTP.
2414  </t>
2415</x:note>
2416<x:note>
2417  <t>
2418    <x:h>Note:</x:h> HTTP requirements for the date/time stamp format apply only
2419    to their usage within the protocol stream. Clients and servers are
2420    not required to use these formats for user presentation, request
2421    logging, etc.
2422  </t>
2423</x:note>
2424</section>
2425
2426
2427<section title="Header Field Definitions" anchor="header.field.definitions">
2428<t>
2429   This section defines the syntax and semantics of HTTP/1.1 header fields
2430   related to request and response semantics.
2431</t>
2432
2433<section title="Allow" anchor="header.allow">
2434  <iref primary="true" item="Allow header field" x:for-anchor=""/>
2435  <iref primary="true" item="Header Fields" subitem="Allow" x:for-anchor=""/>
2436  <x:anchor-alias value="Allow"/>
2437<t>
2438   The "Allow" header field lists the set of methods advertised as
2439   supported by the target resource. The purpose of this field is strictly to
2440   inform the recipient of valid request methods associated with the resource.
2441</t>
2442<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/>
2443  <x:ref>Allow</x:ref> = #<x:ref>Method</x:ref>
2444</artwork></figure>
2445<t>
2446   Example of use:
2447</t>
2448<figure><artwork type="example">
2449  Allow: GET, HEAD, PUT
2450</artwork></figure>
2451<t>
2452   The actual set of allowed methods is defined by the origin server at the
2453   time of each request.
2454</t>
2455<t>
2456   A proxy &MUST-NOT; modify the Allow header field &mdash; it does not need to
2457   understand all the methods specified in order to handle them according to
2458   the generic message handling rules.
2459</t>
2460</section>
2461
2462<section title="Date" anchor="header.date">
2463  <iref primary="true" item="Date header field" x:for-anchor=""/>
2464  <iref primary="true" item="Header Fields" subitem="Date" x:for-anchor=""/>
2465  <x:anchor-alias value="Date"/>
2466<t>
2467   The "Date" header field represents the date and time at which
2468   the message was originated, having the same semantics as the Origination
2469   Date Field (orig-date) defined in <xref target="RFC5322" x:fmt="of" x:sec="3.6.1"/>.
2470   The field value is an HTTP-date, as defined in <xref target="http.date"/>;
2471   it &MUST; be sent in rfc1123-date format.
2472</t>
2473<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Date"/>
2474  <x:ref>Date</x:ref> = <x:ref>HTTP-date</x:ref>
2475</artwork></figure>
2476<t>
2477   An example is
2478</t>
2479<figure><artwork type="example">
2480  Date: Tue, 15 Nov 1994 08:12:31 GMT
2481</artwork></figure>
2482<t>
2483   Origin servers &MUST; include a Date header field in all responses,
2484   except in these cases:
2485  <list style="numbers">
2486      <t>If the response status code is 100 (Continue) or 101 (Switching
2487         Protocols), the response &MAY; include a Date header field, at
2488         the server's option.</t>
2489
2490      <t>If the response status code conveys a server error, e.g., 500
2491         (Internal Server Error) or 503 (Service Unavailable), and it is
2492         inconvenient or impossible to generate a valid Date.</t>
2493
2494      <t>If the server does not have a clock that can provide a
2495         reasonable approximation of the current time, its responses
2496         &MUST-NOT; include a Date header field.</t>
2497  </list>
2498</t>
2499<t>
2500   A received message that does not have a Date header field &MUST; be
2501   assigned one by the recipient if the message will be cached by that
2502   recipient.
2503</t>
2504<t>
2505   Clients can use the Date header field as well; in order to keep request
2506   messages small, they are advised not to include it when it doesn't convey
2507   any useful information (as it is usually the case for requests that do not
2508   contain a payload).
2509</t>
2510<t>
2511   The HTTP-date sent in a Date header field &SHOULD-NOT; represent a date and
2512   time subsequent to the generation of the message. It &SHOULD; represent
2513   the best available approximation of the date and time of message
2514   generation, unless the implementation has no means of generating a
2515   reasonably accurate date and time. In theory, the date ought to
2516   represent the moment just before the payload is generated. In
2517   practice, the date can be generated at any time during the message
2518   origination without affecting its semantic value.
2519</t>
2520</section>
2521
2522<section title="Expect" anchor="header.expect">
2523  <iref primary="true" item="Expect header field" x:for-anchor=""/>
2524  <iref primary="true" item="Header Fields" subitem="Expect" x:for-anchor=""/>
2525  <x:anchor-alias value="Expect"/>
2526  <x:anchor-alias value="expectation"/>
2527  <x:anchor-alias value="expectation-extension"/>
2528  <x:anchor-alias value="expect-params"/>
2529<t>
2530   The "Expect" header field is used to indicate that particular
2531   server behaviors are required by the client.
2532</t>
2533<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"/>
2534  <x:ref>Expect</x:ref>       = 1#<x:ref>expectation</x:ref>
2535 
2536  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
2537  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
2538                           *<x:ref>expect-params</x:ref> ]
2539  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
2540</artwork></figure>
2541<t>
2542   A server that does not understand or is unable to comply with any of
2543   the expectation values in the Expect field of a request &MUST; respond
2544   with appropriate error status code. The server &MUST; respond with a 417
2545   (Expectation Failed) status code if any of the expectations cannot be met
2546   or, if there are other problems with the request, some other 4xx
2547   status code.
2548</t>
2549<t>
2550   This header field is defined with extensible syntax to allow for
2551   future extensions. If a server receives a request containing an
2552   Expect field that includes an expectation-extension that it does not
2553   support, it &MUST; respond with a 417 (Expectation Failed) status code.
2554</t>
2555<t>
2556   Comparison of expectation values is case-insensitive for unquoted
2557   tokens (including the 100-continue token), and is case-sensitive for
2558   quoted-string expectation-extensions.
2559</t>
2560<t>
2561   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
2562   return a 417 (Expectation Failed) status code if it receives a request
2563   with an expectation that it cannot meet. However, the Expect
2564   header field itself is end-to-end; it &MUST; be forwarded if the
2565   request is forwarded.
2566</t>
2567<t>
2568   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
2569   Expect header field.
2570</t>
2571<t>
2572   See &use100; for the use of the 100 (Continue) status code.
2573</t>
2574</section>
2575
2576<section title="From" anchor="header.from">
2577  <iref primary="true" item="From header field" x:for-anchor=""/>
2578  <iref primary="true" item="Header Fields" subitem="From" x:for-anchor=""/>
2579  <x:anchor-alias value="From"/>
2580  <x:anchor-alias value="mailbox"/>
2581<t>
2582   The "From" header field, if given, &SHOULD; contain an Internet
2583   e-mail address for the human user who controls the requesting user
2584   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
2585   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
2586</t>
2587<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/>
2588  <x:ref>From</x:ref>    = <x:ref>mailbox</x:ref>
2589 
2590  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2591</artwork></figure>
2592<t>
2593   An example is:
2594</t>
2595<figure><artwork type="example">
2596  From: webmaster@example.org
2597</artwork></figure>
2598<t>
2599   This header field &MAY; be used for logging purposes and as a means for
2600   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2601   be used as an insecure form of access protection. The interpretation
2602   of this field is that the request is being performed on behalf of the
2603   person given, who accepts responsibility for the method performed. In
2604   particular, robot agents &SHOULD; include this header field so that the
2605   person responsible for running the robot can be contacted if problems
2606   occur on the receiving end.
2607</t>
2608<t>
2609   The Internet e-mail address in this field &MAY; be separate from the
2610   Internet host which issued the request. For example, when a request
2611   is passed through a proxy the original issuer's address &SHOULD; be
2612   used.
2613</t>
2614<t>
2615   The client &SHOULD-NOT;  send the From header field without the user's
2616   approval, as it might conflict with the user's privacy interests or
2617   their site's security policy. It is strongly recommended that the
2618   user be able to disable, enable, and modify the value of this field
2619   at any time prior to a request.
2620</t>
2621</section>
2622
2623<section title="Location" anchor="header.location">
2624  <iref primary="true" item="Location header field" x:for-anchor=""/>
2625  <iref primary="true" item="Header Fields" subitem="Location" x:for-anchor=""/>
2626  <x:anchor-alias value="Location"/>
2627<t>
2628   The "Location" header field is used to identify a newly created
2629   resource, or to redirect the recipient to a different location for
2630   completion of the request.
2631</t>
2632<t>
2633   For 201 (Created) responses, the Location is the URI of the new resource
2634   which was created by the request. For 3xx responses, the location &SHOULD;
2635   indicate the server's preferred URI for automatic redirection to the
2636   resource.
2637</t>
2638<t>
2639   The field value consists of a single URI-reference. When it has the form
2640   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2641   the final value is computed by resolving it against the effective request
2642   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
2643</t>
2644<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/>
2645  <x:ref>Location</x:ref> = <x:ref>URI-reference</x:ref>
2646</artwork></figure>
2647<figure>
2648<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical spacing below, it's necessary this way for xml2rfc-->
2649<artwork type="example">
2650  Location: http://www.example.org/pub/WWW/People.html#tim
2651</artwork></figure><figure><artwork type="example">  Location: /index.html
2652</artwork></figure>
2653<t>
2654   There are circumstances in which a fragment identifier in a Location URI
2655   would not be appropriate. For instance, when it appears in a 201 Created
2656   response, where the Location header field specifies the URI for the entire
2657   created resource.
2658</t>
2659<x:note>
2660  <t>
2661    <x:h>Note:</x:h> This specification does not define precedence rules
2662    for the case where the original URI, as navigated to by the user
2663    agent, and the Location header field value both contain fragment
2664    identifiers. Thus be aware that including fragment identifiers might
2665    inconvenience anyone relying on the semantics of the original URI's
2666    fragment identifier.
2667  </t>
2668</x:note>
2669<x:note>
2670  <t>
2671    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2672    from Location in that the Content-Location identifies the most specific
2673    resource corresponding to the enclosed representation.
2674    It is therefore possible for a response to contain header fields for
2675    both Location and Content-Location.
2676  </t>
2677</x:note>
2678</section>
2679
2680<section title="Max-Forwards" anchor="header.max-forwards">
2681  <iref primary="true" item="Max-Forwards header field" x:for-anchor=""/>
2682  <iref primary="true" item="Header Fields" subitem="Max-Forwards" x:for-anchor=""/>
2683  <x:anchor-alias value="Max-Forwards"/>
2684<t>
2685   The "Max-Forwards" header field provides a mechanism with the
2686   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2687   methods to limit the number of times that the request is forwarded by
2688   proxies. This can be useful when the client is attempting to
2689   trace a request which appears to be failing or looping in mid-chain.
2690</t>
2691<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/>
2692  <x:ref>Max-Forwards</x:ref> = 1*<x:ref>DIGIT</x:ref>
2693</artwork></figure>
2694<t>
2695   The Max-Forwards value is a decimal integer indicating the remaining
2696   number of times this request message can be forwarded.
2697</t>
2698<t>
2699   Each recipient of a TRACE or OPTIONS request
2700   containing a Max-Forwards header field &MUST; check and update its
2701   value prior to forwarding the request. If the received value is zero
2702   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2703   respond as the final recipient. If the received Max-Forwards value is
2704   greater than zero, then the forwarded message &MUST; contain an updated
2705   Max-Forwards field with a value decremented by one (1).
2706</t>
2707<t>
2708   The Max-Forwards header field &MAY; be ignored for all other request
2709   methods.
2710</t>
2711</section>
2712
2713<section title="Referer" anchor="header.referer">
2714  <iref primary="true" item="Referer header field" x:for-anchor=""/>
2715  <iref primary="true" item="Header Fields" subitem="Referer" x:for-anchor=""/>
2716  <x:anchor-alias value="Referer"/>
2717<t>
2718   The "Referer" [sic] header field allows the client to specify the
2719   URI of the resource from which the effective request URI was obtained (the
2720   "referrer", although the header field is misspelled.).
2721</t>
2722<t>
2723   The Referer header field allows servers to generate lists of back-links to
2724   resources for interest, logging, optimized caching, etc. It also allows
2725   obsolete or mistyped links to be traced for maintenance. Some servers use
2726   Referer as a means of controlling where they allow links from (so-called
2727   "deep linking"), but legitimate requests do not always
2728   contain a Referer header field.
2729</t>
2730<t>
2731   If the effective request URI was obtained from a source that does not have its own
2732   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
2733   sent with the value "about:blank", or not be sent at all. Note that this
2734   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2735</t>
2736<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/>
2737  <x:ref>Referer</x:ref> = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2738</artwork></figure>
2739<t>
2740   Example:
2741</t>
2742<figure><artwork type="example">
2743  Referer: http://www.example.org/hypertext/Overview.html
2744</artwork></figure>
2745<t>
2746   If the field value is a relative URI, it &SHOULD; be interpreted
2747   relative to the effective request URI. The URI &MUST-NOT; include a fragment. See
2748   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2749</t>
2750</section>
2751
2752<section title="Retry-After" anchor="header.retry-after">
2753  <iref primary="true" item="Retry-After header field" x:for-anchor=""/>
2754  <iref primary="true" item="Header Fields" subitem="Retry-After" x:for-anchor=""/>
2755  <x:anchor-alias value="Retry-After"/>
2756<t>
2757   The header "Retry-After" field can be used with a 503 (Service
2758   Unavailable) response to indicate how long the service is expected to
2759   be unavailable to the requesting client. This field &MAY; also be used
2760   with any 3xx (Redirection) response to indicate the minimum time the
2761   user-agent is asked wait before issuing the redirected request.
2762</t>
2763<t>
2764   The value of this field can be either an HTTP-date or an integer number
2765   of seconds (in decimal) after the time of the response.
2766</t>
2767<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/>
2768  <x:ref>Retry-After</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2769</artwork></figure>
2770<t anchor="rule.delta-seconds">
2771  <x:anchor-alias value="delta-seconds"/>
2772   Time spans are non-negative decimal integers, representing time in
2773   seconds.
2774</t>
2775<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2776  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2777</artwork></figure>
2778<t>
2779   Two examples of its use are
2780</t>
2781<figure><artwork type="example">
2782  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2783  Retry-After: 120
2784</artwork></figure>
2785<t>
2786   In the latter example, the delay is 2 minutes.
2787</t>
2788</section>
2789
2790<section title="Server" anchor="header.server">
2791  <iref primary="true" item="Server header field" x:for-anchor=""/>
2792  <iref primary="true" item="Header Fields" subitem="Server" x:for-anchor=""/>
2793  <x:anchor-alias value="Server"/>
2794<t>
2795   The "Server" header field contains information about the
2796   software used by the origin server to handle the request.
2797</t>
2798<t>
2799   The field can contain multiple product tokens (&product-tokens;) and
2800   comments (&header-fields;) identifying the server and any significant
2801   subproducts. The product tokens are listed in order of their significance
2802   for identifying the application.
2803</t>
2804<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/>
2805  <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> ) )
2806</artwork></figure>
2807<t>
2808   Example:
2809</t>
2810<figure><artwork type="example">
2811  Server: CERN/3.0 libwww/2.17
2812</artwork></figure>
2813<t>
2814   If the response is being forwarded through a proxy, the proxy
2815   application &MUST-NOT; modify the Server header field. Instead, it
2816   &MUST; include a Via field (as described in &header-via;).
2817</t>
2818<x:note>
2819  <t>
2820    <x:h>Note:</x:h> Revealing the specific software version of the server might
2821    allow the server machine to become more vulnerable to attacks
2822    against software that is known to contain security holes. Server
2823    implementors are encouraged to make this field a configurable
2824    option.
2825  </t>
2826</x:note>
2827</section>
2828
2829<section title="User-Agent" anchor="header.user-agent">
2830  <iref primary="true" item="User-Agent header field" x:for-anchor=""/>
2831  <iref primary="true" item="Header Fields" subitem="User-Agent" x:for-anchor=""/>
2832  <x:anchor-alias value="User-Agent"/>
2833<t>
2834   The "User-Agent" header field contains information about the user
2835   agent originating the request. User agents &SHOULD; include this field with
2836   requests.
2837</t>
2838<t>
2839   Typically, it is used for statistical purposes, the tracing of protocol
2840   violations, and tailoring responses to avoid particular user agent
2841   limitations.
2842</t>
2843<t>
2844   The field can contain multiple product tokens (&product-tokens;)
2845   and comments (&header-fields;) identifying the agent and its
2846   significant subproducts. By convention, the product tokens are listed in
2847   order of their significance for identifying the application.
2848</t>
2849<t>
2850   Because this field is usually sent on every request a user agent makes,
2851   implementations are encouraged not to include needlessly fine-grained
2852   detail, and to limit (or even prohibit) the addition of subproducts by third
2853   parties. Overly long and detailed User-Agent field values make requests
2854   larger and can also be used to identify ("fingerprint") the user against
2855   their wishes.
2856</t>
2857<t>
2858   Likewise, implementations are encouraged not to use the product tokens of
2859   other implementations in order to declare compatibility with them, as this
2860   circumvents the purpose of the field. Finally, they are encouraged not to
2861   use comments to identify products; doing so makes the field value more
2862   difficult to parse.
2863</t>
2864<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/>
2865  <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> ) )
2866</artwork></figure>
2867<t>
2868   Example:
2869</t>
2870<figure><artwork type="example">
2871  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2872</artwork></figure>
2873</section>
2874
2875</section>
2876
2877<section title="IANA Considerations" anchor="IANA.considerations">
2878
2879<section title="Method Registry" anchor="method.registration">
2880<t>
2881  The registration procedure for HTTP request methods is defined by
2882  <xref target="method.registry"/> of this document.
2883</t>
2884<t>
2885   The HTTP Method Registry shall be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2886   and be populated with the registrations below:
2887</t>
2888<?BEGININC p2-semantics.iana-methods ?>
2889<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2890<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2891   <ttcol>Method</ttcol>
2892   <ttcol>Safe</ttcol>
2893   <ttcol>Reference</ttcol>
2894   <c>CONNECT</c>
2895   <c>no</c>
2896   <c>
2897      <xref target="CONNECT"/>
2898   </c>
2899   <c>DELETE</c>
2900   <c>no</c>
2901   <c>
2902      <xref target="DELETE"/>
2903   </c>
2904   <c>GET</c>
2905   <c>yes</c>
2906   <c>
2907      <xref target="GET"/>
2908   </c>
2909   <c>HEAD</c>
2910   <c>yes</c>
2911   <c>
2912      <xref target="HEAD"/>
2913   </c>
2914   <c>OPTIONS</c>
2915   <c>yes</c>
2916   <c>
2917      <xref target="OPTIONS"/>
2918   </c>
2919   <c>POST</c>
2920   <c>no</c>
2921   <c>
2922      <xref target="POST"/>
2923   </c>
2924   <c>PUT</c>
2925   <c>no</c>
2926   <c>
2927      <xref target="PUT"/>
2928   </c>
2929   <c>TRACE</c>
2930   <c>yes</c>
2931   <c>
2932      <xref target="TRACE"/>
2933   </c>
2934</texttable>
2935<!--(END)-->
2936<?ENDINC p2-semantics.iana-methods ?>
2937</section>
2938
2939<section title="Status Code Registry" anchor="status.code.registration">
2940<t>
2941   The registration procedure for HTTP Status Codes &mdash; previously defined
2942   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> &mdash; is now defined
2943   by <xref target="status.code.registry"/> of this document.
2944</t>
2945<t>
2946   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2947   shall be updated with the registrations below:
2948</t>
2949<?BEGININC p2-semantics.iana-status-codes ?>
2950<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2951<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2952   <ttcol>Value</ttcol>
2953   <ttcol>Description</ttcol>
2954   <ttcol>Reference</ttcol>
2955   <c>100</c>
2956   <c>Continue</c>
2957   <c>
2958      <xref target="status.100"/>
2959   </c>
2960   <c>101</c>
2961   <c>Switching Protocols</c>
2962   <c>
2963      <xref target="status.101"/>
2964   </c>
2965   <c>200</c>
2966   <c>OK</c>
2967   <c>
2968      <xref target="status.200"/>
2969   </c>
2970   <c>201</c>
2971   <c>Created</c>
2972   <c>
2973      <xref target="status.201"/>
2974   </c>
2975   <c>202</c>
2976   <c>Accepted</c>
2977   <c>
2978      <xref target="status.202"/>
2979   </c>
2980   <c>203</c>
2981   <c>Non-Authoritative Information</c>
2982   <c>
2983      <xref target="status.203"/>
2984   </c>
2985   <c>204</c>
2986   <c>No Content</c>
2987   <c>
2988      <xref target="status.204"/>
2989   </c>
2990   <c>205</c>
2991   <c>Reset Content</c>
2992   <c>
2993      <xref target="status.205"/>
2994   </c>
2995   <c>300</c>
2996   <c>Multiple Choices</c>
2997   <c>
2998      <xref target="status.300"/>
2999   </c>
3000   <c>301</c>
3001   <c>Moved Permanently</c>
3002   <c>
3003      <xref target="status.301"/>
3004   </c>
3005   <c>302</c>
3006   <c>Found</c>
3007   <c>
3008      <xref target="status.302"/>
3009   </c>
3010   <c>303</c>
3011   <c>See Other</c>
3012   <c>
3013      <xref target="status.303"/>
3014   </c>
3015   <c>305</c>
3016   <c>Use Proxy</c>
3017   <c>
3018      <xref target="status.305"/>
3019   </c>
3020   <c>306</c>
3021   <c>(Unused)</c>
3022   <c>
3023      <xref target="status.306"/>
3024   </c>
3025   <c>307</c>
3026   <c>Temporary Redirect</c>
3027   <c>
3028      <xref target="status.307"/>
3029   </c>
3030   <c>400</c>
3031   <c>Bad Request</c>
3032   <c>
3033      <xref target="status.400"/>
3034   </c>
3035   <c>402</c>
3036   <c>Payment Required</c>
3037   <c>
3038      <xref target="status.402"/>
3039   </c>
3040   <c>403</c>
3041   <c>Forbidden</c>
3042   <c>
3043      <xref target="status.403"/>
3044   </c>
3045   <c>404</c>
3046   <c>Not Found</c>
3047   <c>
3048      <xref target="status.404"/>
3049   </c>
3050   <c>405</c>
3051   <c>Method Not Allowed</c>
3052   <c>
3053      <xref target="status.405"/>
3054   </c>
3055   <c>406</c>
3056   <c>Not Acceptable</c>
3057   <c>
3058      <xref target="status.406"/>
3059   </c>
3060   <c>407</c>
3061   <c>Proxy Authentication Required</c>
3062   <c>
3063      <xref target="status.407"/>
3064   </c>
3065   <c>408</c>
3066   <c>Request Timeout</c>
3067   <c>
3068      <xref target="status.408"/>
3069   </c>
3070   <c>409</c>
3071   <c>Conflict</c>
3072   <c>
3073      <xref target="status.409"/>
3074   </c>
3075   <c>410</c>
3076   <c>Gone</c>
3077   <c>
3078      <xref target="status.410"/>
3079   </c>
3080   <c>411</c>
3081   <c>Length Required</c>
3082   <c>
3083      <xref target="status.411"/>
3084   </c>
3085   <c>413</c>
3086   <c>Request Representation Too Large</c>
3087   <c>
3088      <xref target="status.413"/>
3089   </c>
3090   <c>414</c>
3091   <c>URI Too Long</c>
3092   <c>
3093      <xref target="status.414"/>
3094   </c>
3095   <c>415</c>
3096   <c>Unsupported Media Type</c>
3097   <c>
3098      <xref target="status.415"/>
3099   </c>
3100   <c>417</c>
3101   <c>Expectation Failed</c>
3102   <c>
3103      <xref target="status.417"/>
3104   </c>
3105   <c>426</c>
3106   <c>Upgrade Required</c>
3107   <c>
3108      <xref target="status.426"/>
3109   </c>
3110   <c>500</c>
3111   <c>Internal Server Error</c>
3112   <c>
3113      <xref target="status.500"/>
3114   </c>
3115   <c>501</c>
3116   <c>Not Implemented</c>
3117   <c>
3118      <xref target="status.501"/>
3119   </c>
3120   <c>502</c>
3121   <c>Bad Gateway</c>
3122   <c>
3123      <xref target="status.502"/>
3124   </c>
3125   <c>503</c>
3126   <c>Service Unavailable</c>
3127   <c>
3128      <xref target="status.503"/>
3129   </c>
3130   <c>504</c>
3131   <c>Gateway Timeout</c>
3132   <c>
3133      <xref target="status.504"/>
3134   </c>
3135   <c>505</c>
3136   <c>HTTP Version Not Supported</c>
3137   <c>
3138      <xref target="status.505"/>
3139   </c>
3140</texttable>
3141<!--(END)-->
3142<?ENDINC p2-semantics.iana-status-codes ?>
3143</section>
3144<section title="Header Field Registration" anchor="header.field.registration">
3145<t>
3146   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
3147   with the permanent registrations below (see <xref target="RFC3864"/>):
3148</t>
3149<?BEGININC p2-semantics.iana-headers ?>
3150<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
3151<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
3152   <ttcol>Header Field Name</ttcol>
3153   <ttcol>Protocol</ttcol>
3154   <ttcol>Status</ttcol>
3155   <ttcol>Reference</ttcol>
3156
3157   <c>Allow</c>
3158   <c>http</c>
3159   <c>standard</c>
3160   <c>
3161      <xref target="header.allow"/>
3162   </c>
3163   <c>Date</c>
3164   <c>http</c>
3165   <c>standard</c>
3166   <c>
3167      <xref target="header.date"/>
3168   </c>
3169   <c>Expect</c>
3170   <c>http</c>
3171   <c>standard</c>
3172   <c>
3173      <xref target="header.expect"/>
3174   </c>
3175   <c>From</c>
3176   <c>http</c>
3177   <c>standard</c>
3178   <c>
3179      <xref target="header.from"/>
3180   </c>
3181   <c>Location</c>
3182   <c>http</c>
3183   <c>standard</c>
3184   <c>
3185      <xref target="header.location"/>
3186   </c>
3187   <c>Max-Forwards</c>
3188   <c>http</c>
3189   <c>standard</c>
3190   <c>
3191      <xref target="header.max-forwards"/>
3192   </c>
3193   <c>Referer</c>
3194   <c>http</c>
3195   <c>standard</c>
3196   <c>
3197      <xref target="header.referer"/>
3198   </c>
3199   <c>Retry-After</c>
3200   <c>http</c>
3201   <c>standard</c>
3202   <c>
3203      <xref target="header.retry-after"/>
3204   </c>
3205   <c>Server</c>
3206   <c>http</c>
3207   <c>standard</c>
3208   <c>
3209      <xref target="header.server"/>
3210   </c>
3211   <c>User-Agent</c>
3212   <c>http</c>
3213   <c>standard</c>
3214   <c>
3215      <xref target="header.user-agent"/>
3216   </c>
3217</texttable>
3218<!--(END)-->
3219<?ENDINC p2-semantics.iana-headers ?>
3220<t>
3221   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
3222</t>
3223</section>
3224</section>
3225
3226<section title="Security Considerations" anchor="security.considerations">
3227<t>
3228   This section is meant to inform application developers, information
3229   providers, and users of the security limitations in HTTP/1.1 as
3230   described by this document. The discussion does not include
3231   definitive solutions to the problems revealed, though it does make
3232   some suggestions for reducing security risks.
3233</t>
3234
3235<section title="Transfer of Sensitive Information" anchor="security.sensitive">
3236<t>
3237   Like any generic data transfer protocol, HTTP cannot regulate the
3238   content of the data that is transferred, nor is there any a priori
3239   method of determining the sensitivity of any particular piece of
3240   information within the context of any given request. Therefore,
3241   applications &SHOULD; supply as much control over this information as
3242   possible to the provider of that information. Four header fields are
3243   worth special mention in this context: Server, Via, Referer and From.
3244</t>
3245<t>
3246   Revealing the specific software version of the server might allow the
3247   server machine to become more vulnerable to attacks against software
3248   that is known to contain security holes. Implementors &SHOULD; make the
3249   Server header field a configurable option.
3250</t>
3251<t>
3252   Proxies which serve as a portal through a network firewall &SHOULD;
3253   take special precautions regarding the transfer of header information
3254   that identifies the hosts behind the firewall. In particular, they
3255   &SHOULD; remove, or replace with sanitized versions, any Via fields
3256   generated behind the firewall.
3257</t>
3258<t>
3259   The Referer header field allows reading patterns to be studied and reverse
3260   links drawn. Although it can be very useful, its power can be abused
3261   if user details are not separated from the information contained in
3262   the Referer. Even when the personal information has been removed, the
3263   Referer header field might indicate a private document's URI whose
3264   publication would be inappropriate.
3265</t>
3266<t>
3267   The information sent in the From field might conflict with the user's
3268   privacy interests or their site's security policy, and hence it
3269   &SHOULD-NOT;  be transmitted without the user being able to disable,
3270   enable, and modify the contents of the field. The user &MUST; be able
3271   to set the contents of this field within a user preference or
3272   application defaults configuration.
3273</t>
3274<t>
3275   We suggest, though do not require, that a convenient toggle interface
3276   be provided for the user to enable or disable the sending of From and
3277   Referer information.
3278</t>
3279<t>
3280   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref
3281   target="header.server"/>) header fields can sometimes be used to determine
3282   that a specific client or server have a particular security hole which might
3283   be exploited. Unfortunately, this same information is often used for other
3284   valuable purposes for which HTTP currently has no better mechanism.
3285</t>
3286<t>
3287   Furthermore, the User-Agent header field may contain enough entropy to be
3288   used, possibly in conjunction with other material, to uniquely identify the
3289   user.
3290</t>
3291<t>
3292   Some request methods, like TRACE (<xref target="TRACE"/>), expose information
3293   that was sent in request header fields within the body of their response.
3294   Clients &SHOULD; be careful with sensitive information, like Cookies,
3295   Authorization credentials, and other header fields that might be used to
3296   collect data from the client.
3297</t> 
3298</section>
3299
3300<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
3301<t>
3302   Because the source of a link might be private information or might
3303   reveal an otherwise private information source, it is strongly
3304   recommended that the user be able to select whether or not the
3305   Referer field is sent. For example, a browser client could have a
3306   toggle switch for browsing openly/anonymously, which would
3307   respectively enable/disable the sending of Referer and From
3308   information.
3309</t>
3310<t>
3311   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
3312   HTTP request if the referring page was transferred with a secure
3313   protocol.
3314</t>
3315<t>
3316   Authors of services &SHOULD-NOT; use GET-based forms for the submission of
3317   sensitive data because that data will be placed in the request-target. Many
3318   existing servers, proxies, and user agents log or display the request-target
3319   in places where it might be visible to third parties. Such services can
3320   use POST-based form submission instead.
3321</t>
3322</section>
3323
3324<section title="Location Headers and Spoofing" anchor="location.spoofing">
3325<t>
3326   If a single server supports multiple organizations that do not trust
3327   one another, then it &MUST; check the values of Location and Content-Location
3328   header fields in responses that are generated under control of
3329   said organizations to make sure that they do not attempt to
3330   invalidate resources over which they have no authority.
3331</t>
3332</section>
3333
3334<section title="Security Considerations for CONNECT">
3335<t>
3336   Since tunneled data is opaque to the proxy, there are additional
3337   risks to tunneling to other well-known or reserved ports.
3338   A HTTP client CONNECTing to port 25 could relay spam
3339   via SMTP, for example. As such, proxies &SHOULD; restrict CONNECT
3340   access to a small number of known ports.
3341</t>
3342</section>
3343
3344</section>
3345
3346<section title="Acknowledgments" anchor="acks">
3347<t>
3348  See &acks;.
3349</t>
3350</section>
3351</middle>
3352<back>
3353
3354<references title="Normative References">
3355
3356<reference anchor="Part1">
3357  <front>
3358    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
3359    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3360      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3361      <address><email>fielding@gbiv.com</email></address>
3362    </author>
3363    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3364      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3365      <address><email>jg@freedesktop.org</email></address>
3366    </author>
3367    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3368      <organization abbrev="HP">Hewlett-Packard Company</organization>
3369      <address><email>JeffMogul@acm.org</email></address>
3370    </author>
3371    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3372      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3373      <address><email>henrikn@microsoft.com</email></address>
3374    </author>
3375    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3376      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3377      <address><email>LMM@acm.org</email></address>
3378    </author>
3379    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3380      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3381      <address><email>paulle@microsoft.com</email></address>
3382    </author>
3383    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3384      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3385      <address><email>timbl@w3.org</email></address>
3386    </author>
3387    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3388      <organization abbrev="W3C">World Wide Web Consortium</organization>
3389      <address><email>ylafon@w3.org</email></address>
3390    </author>
3391    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3392      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3393      <address><email>julian.reschke@greenbytes.de</email></address>
3394    </author>
3395    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3396  </front>
3397  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
3398  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
3399</reference>
3400
3401<reference anchor="Part3">
3402  <front>
3403    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
3404    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3405      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3406      <address><email>fielding@gbiv.com</email></address>
3407    </author>
3408    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3409      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3410      <address><email>jg@freedesktop.org</email></address>
3411    </author>
3412    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3413      <organization abbrev="HP">Hewlett-Packard Company</organization>
3414      <address><email>JeffMogul@acm.org</email></address>
3415    </author>
3416    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3417      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3418      <address><email>henrikn@microsoft.com</email></address>
3419    </author>
3420    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3421      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3422      <address><email>LMM@acm.org</email></address>
3423    </author>
3424    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3425      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3426      <address><email>paulle@microsoft.com</email></address>
3427    </author>
3428    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3429      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3430      <address><email>timbl@w3.org</email></address>
3431    </author>
3432    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3433      <organization abbrev="W3C">World Wide Web Consortium</organization>
3434      <address><email>ylafon@w3.org</email></address>
3435    </author>
3436    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3437      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3438      <address><email>julian.reschke@greenbytes.de</email></address>
3439    </author>
3440    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3441  </front>
3442  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
3443  <x:source href="p3-payload.xml" basename="p3-payload"/>
3444</reference>
3445
3446<reference anchor="Part4">
3447  <front>
3448    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
3449    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3450      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3451      <address><email>fielding@gbiv.com</email></address>
3452    </author>
3453    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3454      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3455      <address><email>jg@freedesktop.org</email></address>
3456    </author>
3457    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3458      <organization abbrev="HP">Hewlett-Packard Company</organization>
3459      <address><email>JeffMogul@acm.org</email></address>
3460    </author>
3461    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3462      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3463      <address><email>henrikn@microsoft.com</email></address>
3464    </author>
3465    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3466      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3467      <address><email>LMM@acm.org</email></address>
3468    </author>
3469    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3470      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3471      <address><email>paulle@microsoft.com</email></address>
3472    </author>
3473    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3474      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3475      <address><email>timbl@w3.org</email></address>
3476    </author>
3477    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3478      <organization abbrev="W3C">World Wide Web Consortium</organization>
3479      <address><email>ylafon@w3.org</email></address>
3480    </author>
3481    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3482      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3483      <address><email>julian.reschke@greenbytes.de</email></address>
3484    </author>
3485    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3486  </front>
3487  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
3488  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
3489</reference>
3490
3491<reference anchor="Part5">
3492  <front>
3493    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
3494    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3495      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3496      <address><email>fielding@gbiv.com</email></address>
3497    </author>
3498    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3499      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3500      <address><email>jg@freedesktop.org</email></address>
3501    </author>
3502    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3503      <organization abbrev="HP">Hewlett-Packard Company</organization>
3504      <address><email>JeffMogul@acm.org</email></address>
3505    </author>
3506    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3507      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3508      <address><email>henrikn@microsoft.com</email></address>
3509    </author>
3510    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3511      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3512      <address><email>LMM@acm.org</email></address>
3513    </author>
3514    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3515      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3516      <address><email>paulle@microsoft.com</email></address>
3517    </author>
3518    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3519      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3520      <address><email>timbl@w3.org</email></address>
3521    </author>
3522    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3523      <organization abbrev="W3C">World Wide Web Consortium</organization>
3524      <address><email>ylafon@w3.org</email></address>
3525    </author>
3526    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3527      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3528      <address><email>julian.reschke@greenbytes.de</email></address>
3529    </author>
3530    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3531  </front>
3532  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
3533  <x:source href="p5-range.xml" basename="p5-range"/>
3534</reference>
3535
3536<reference anchor="Part6">
3537  <front>
3538    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
3539    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3540      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3541      <address><email>fielding@gbiv.com</email></address>
3542    </author>
3543    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3544      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3545      <address><email>jg@freedesktop.org</email></address>
3546    </author>
3547    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3548      <organization abbrev="HP">Hewlett-Packard Company</organization>
3549      <address><email>JeffMogul@acm.org</email></address>
3550    </author>
3551    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3552      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3553      <address><email>henrikn@microsoft.com</email></address>
3554    </author>
3555    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3556      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3557      <address><email>LMM@acm.org</email></address>
3558    </author>
3559    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3560      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3561      <address><email>paulle@microsoft.com</email></address>
3562    </author>
3563    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3564      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3565      <address><email>timbl@w3.org</email></address>
3566    </author>
3567    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3568      <organization abbrev="W3C">World Wide Web Consortium</organization>
3569      <address><email>ylafon@w3.org</email></address>
3570    </author>
3571    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
3572      <organization>Rackspace</organization>
3573      <address><email>mnot@mnot.net</email></address>
3574    </author>
3575    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3576      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3577      <address><email>julian.reschke@greenbytes.de</email></address>
3578    </author>
3579    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3580  </front>
3581  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
3582  <x:source href="p6-cache.xml" basename="p6-cache"/>
3583</reference>
3584
3585<reference anchor="Part7">
3586  <front>
3587    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
3588    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3589      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3590      <address><email>fielding@gbiv.com</email></address>
3591    </author>
3592    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3593      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3594      <address><email>jg@freedesktop.org</email></address>
3595    </author>
3596    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3597      <organization abbrev="HP">Hewlett-Packard Company</organization>
3598      <address><email>JeffMogul@acm.org</email></address>
3599    </author>
3600    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3601      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3602      <address><email>henrikn@microsoft.com</email></address>
3603    </author>
3604    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3605      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3606      <address><email>LMM@acm.org</email></address>
3607    </author>
3608    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3609      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3610      <address><email>paulle@microsoft.com</email></address>
3611    </author>
3612    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3613      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3614      <address><email>timbl@w3.org</email></address>
3615    </author>
3616    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3617      <organization abbrev="W3C">World Wide Web Consortium</organization>
3618      <address><email>ylafon@w3.org</email></address>
3619    </author>
3620    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3621      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3622      <address><email>julian.reschke@greenbytes.de</email></address>
3623    </author>
3624    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3625  </front>
3626  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3627  <x:source href="p7-auth.xml" basename="p7-auth"/>
3628</reference>
3629
3630<reference anchor="RFC2119">
3631  <front>
3632    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3633    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3634      <organization>Harvard University</organization>
3635      <address><email>sob@harvard.edu</email></address>
3636    </author>
3637    <date month="March" year="1997"/>
3638  </front>
3639  <seriesInfo name="BCP" value="14"/>
3640  <seriesInfo name="RFC" value="2119"/>
3641</reference>
3642
3643<reference anchor="RFC3986">
3644 <front>
3645  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3646  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3647    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3648    <address>
3649       <email>timbl@w3.org</email>
3650       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3651    </address>
3652  </author>
3653  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3654    <organization abbrev="Day Software">Day Software</organization>
3655    <address>
3656      <email>fielding@gbiv.com</email>
3657      <uri>http://roy.gbiv.com/</uri>
3658    </address>
3659  </author>
3660  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3661    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3662    <address>
3663      <email>LMM@acm.org</email>
3664      <uri>http://larry.masinter.net/</uri>
3665    </address>
3666  </author>
3667  <date month='January' year='2005'></date>
3668 </front>
3669 <seriesInfo name="STD" value="66"/>
3670 <seriesInfo name="RFC" value="3986"/>
3671</reference>
3672
3673<reference anchor="RFC5234">
3674  <front>
3675    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3676    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3677      <organization>Brandenburg InternetWorking</organization>
3678      <address>
3679        <email>dcrocker@bbiw.net</email>
3680      </address> 
3681    </author>
3682    <author initials="P." surname="Overell" fullname="Paul Overell">
3683      <organization>THUS plc.</organization>
3684      <address>
3685        <email>paul.overell@thus.net</email>
3686      </address>
3687    </author>
3688    <date month="January" year="2008"/>
3689  </front>
3690  <seriesInfo name="STD" value="68"/>
3691  <seriesInfo name="RFC" value="5234"/>
3692</reference>
3693
3694</references>
3695
3696<references title="Informative References">
3697
3698<reference anchor="RFC1123">
3699  <front>
3700    <title>Requirements for Internet Hosts - Application and Support</title>
3701    <author initials="R." surname="Braden" fullname="Robert Braden">
3702      <organization>University of Southern California (USC), Information Sciences Institute</organization>
3703      <address><email>Braden@ISI.EDU</email></address>
3704    </author>
3705    <date month="October" year="1989"/>
3706  </front>
3707  <seriesInfo name="STD" value="3"/>
3708  <seriesInfo name="RFC" value="1123"/>
3709</reference>
3710
3711<reference anchor="RFC1945">
3712  <front>
3713    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3714    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3715      <organization>MIT, Laboratory for Computer Science</organization>
3716      <address><email>timbl@w3.org</email></address>
3717    </author>
3718    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3719      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3720      <address><email>fielding@ics.uci.edu</email></address>
3721    </author>
3722    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3723      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3724      <address><email>frystyk@w3.org</email></address>
3725    </author>
3726    <date month="May" year="1996"/>
3727  </front>
3728  <seriesInfo name="RFC" value="1945"/>
3729</reference>
3730
3731<reference anchor="RFC2068">
3732  <front>
3733    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3734    <author initials="R." 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="J." surname="Gettys" fullname="Jim Gettys">
3739      <organization>MIT Laboratory for Computer Science</organization>
3740      <address><email>jg@w3.org</email></address>
3741    </author>
3742    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3743      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3744      <address><email>mogul@wrl.dec.com</email></address>
3745    </author>
3746    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3747      <organization>MIT Laboratory for Computer Science</organization>
3748      <address><email>frystyk@w3.org</email></address>
3749    </author>
3750    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3751      <organization>MIT Laboratory for Computer Science</organization>
3752      <address><email>timbl@w3.org</email></address>
3753    </author>
3754    <date month="January" year="1997"/>
3755  </front>
3756  <seriesInfo name="RFC" value="2068"/>
3757</reference>
3758
3759<reference anchor="RFC2616">
3760  <front>
3761    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3762    <author initials="R." surname="Fielding" fullname="R. Fielding">
3763      <organization>University of California, Irvine</organization>
3764      <address><email>fielding@ics.uci.edu</email></address>
3765    </author>
3766    <author initials="J." surname="Gettys" fullname="J. Gettys">
3767      <organization>W3C</organization>
3768      <address><email>jg@w3.org</email></address>
3769    </author>
3770    <author initials="J." surname="Mogul" fullname="J. Mogul">
3771      <organization>Compaq Computer Corporation</organization>
3772      <address><email>mogul@wrl.dec.com</email></address>
3773    </author>
3774    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3775      <organization>MIT Laboratory for Computer Science</organization>
3776      <address><email>frystyk@w3.org</email></address>
3777    </author>
3778    <author initials="L." surname="Masinter" fullname="L. Masinter">
3779      <organization>Xerox Corporation</organization>
3780      <address><email>masinter@parc.xerox.com</email></address>
3781    </author>
3782    <author initials="P." surname="Leach" fullname="P. Leach">
3783      <organization>Microsoft Corporation</organization>
3784      <address><email>paulle@microsoft.com</email></address>
3785    </author>
3786    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3787      <organization>W3C</organization>
3788      <address><email>timbl@w3.org</email></address>
3789    </author>
3790    <date month="June" year="1999"/>
3791  </front>
3792  <seriesInfo name="RFC" value="2616"/>
3793</reference>
3794
3795<reference anchor='RFC2817'>
3796  <front>
3797    <title>Upgrading to TLS Within HTTP/1.1</title>
3798    <author initials='R.' surname='Khare' fullname='R. Khare'>
3799      <organization>4K Associates / UC Irvine</organization>
3800      <address><email>rohit@4K-associates.com</email></address>
3801    </author>
3802    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3803      <organization>Agranat Systems, Inc.</organization>
3804      <address><email>lawrence@agranat.com</email></address>
3805    </author>
3806    <date year='2000' month='May' />
3807  </front>
3808  <seriesInfo name='RFC' value='2817' />
3809</reference>
3810
3811<reference anchor='RFC3864'>
3812  <front>
3813    <title>Registration Procedures for Message Header Fields</title>
3814    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3815      <organization>Nine by Nine</organization>
3816      <address><email>GK-IETF@ninebynine.org</email></address>
3817    </author>
3818    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3819      <organization>BEA Systems</organization>
3820      <address><email>mnot@pobox.com</email></address>
3821    </author>
3822    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3823      <organization>HP Labs</organization>
3824      <address><email>JeffMogul@acm.org</email></address>
3825    </author>
3826    <date year='2004' month='September' />
3827  </front>
3828  <seriesInfo name='BCP' value='90' />
3829  <seriesInfo name='RFC' value='3864' />
3830</reference>
3831
3832<reference anchor='RFC5226'>
3833  <front>
3834    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3835    <author initials='T.' surname='Narten' fullname='T. Narten'>
3836      <organization>IBM</organization>
3837      <address><email>narten@us.ibm.com</email></address>
3838    </author>
3839    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3840      <organization>Google</organization>
3841      <address><email>Harald@Alvestrand.no</email></address>
3842    </author>
3843    <date year='2008' month='May' />
3844  </front>
3845  <seriesInfo name='BCP' value='26' />
3846  <seriesInfo name='RFC' value='5226' />
3847</reference>
3848
3849<reference anchor="RFC5322">
3850  <front>
3851    <title>Internet Message Format</title>
3852    <author initials="P." surname="Resnick" fullname="P. Resnick">
3853      <organization>Qualcomm Incorporated</organization>
3854    </author>
3855    <date year="2008" month="October"/>
3856  </front> 
3857  <seriesInfo name="RFC" value="5322"/>
3858</reference>
3859
3860<reference anchor='RFC5789'>
3861  <front>
3862    <title>PATCH Method for HTTP</title>
3863    <author initials='L.' surname='Dusseault' fullname='L. Dusseault'>
3864      <organization>Linden Lab</organization>
3865    </author>
3866    <author initials='J.' surname='Snell' fullname='J. Snell' />
3867    <date year='2010' month='March' />
3868  </front>
3869  <seriesInfo name='RFC' value='5789' />
3870</reference>
3871
3872<reference anchor="RFC5987">
3873        <front>
3874    <title>Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters</title>
3875    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke">
3876      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3877      <address>
3878        <postal>
3879          <street>Hafenweg 16</street>
3880          <city>Muenster</city><region>NW</region><code>48155</code>
3881          <country>Germany</country>
3882        </postal>
3883        <email>julian.reschke@greenbytes.de</email>     
3884        <uri>http://greenbytes.de/tech/webdav/</uri>   
3885      </address>
3886    </author>
3887    <date month="August" year="2010"/>
3888  </front>
3889  <seriesInfo name="RFC" value="5987"/>
3890</reference>
3891
3892</references>
3893
3894<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3895<t>
3896  This document takes over the Status Code Registry, previously defined
3897  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3898  (<xref target="status.code.registry"/>)
3899</t>
3900<t>
3901  Clarify definition of POST.
3902  (<xref target="POST"/>)
3903</t>
3904<t>
3905  Remove requirement to handle all Content-* header fields; ban use of
3906  Content-Range with PUT.
3907  (<xref target="PUT"/>)
3908</t>
3909<t>
3910  Take over definition of CONNECT method from <xref target="RFC2817"/>.
3911  (<xref target="CONNECT"/>)
3912</t>
3913<t>
3914  Broadened the definition of 203 (Non-Authoritative Information) to include
3915  cases of payload transformations as well.
3916  (<xref target="status.203"/>)
3917</t>
3918<t>
3919  Failed to consider that there are many other request methods that are safe
3920  to automatically redirect, and further that the user agent is able to make
3921  that determination based on the request method semantics.
3922  Furthermore, allow user agents to rewrite the method from POST to GET
3923  for status codes 301 and 302.
3924  (Sections <xref format="counter" target="status.301"/>,
3925  <xref format="counter" target="status.302"/> and
3926  <xref format="counter" target="status.307"/>)
3927</t>
3928<t>
3929  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3930  It used to indicate that the target resource must be accessed through the
3931  proxy given by the Location field. The Location field gave the URI of the
3932  proxy. The recipient was expected to repeat this single request via the proxy.
3933  (<xref target="status.305"/>)
3934</t>
3935<t>
3936  Define status 426 (Upgrade Required) (this was incorporated from
3937  <xref target="RFC2817"/>).
3938  (<xref target="status.426"/>)
3939</t>
3940<t>
3941  Change ABNF productions for header fields to only define the field value.
3942  (<xref target="header.field.definitions"/>)
3943</t>
3944<t>
3945  Reclassify "Allow" as response header field, removing the option to
3946  specify it in a PUT request.
3947  Relax the server requirement on the contents of the Allow header field and
3948  remove requirement on clients to always trust the header field value.
3949  (<xref target="header.allow"/>)
3950</t>
3951<t>
3952  Correct syntax of Location header field to allow URI references (including
3953  relative references and fragments), as referred symbol "absoluteURI" wasn't
3954  what was expected, and add some clarifications as to when use of fragments
3955  would not be appropriate.
3956  (<xref target="header.location"/>)
3957</t>
3958<t>
3959  Restrict Max-Forwards header field to OPTIONS and TRACE (previously,
3960  extension methods could have used it as well).
3961  (<xref target="header.max-forwards"/>)
3962</t>
3963<t>
3964  Allow Referer field value of "about:blank" as alternative to not specifying it.
3965  (<xref target="header.referer"/>)
3966</t>
3967<t>
3968  In the description of the Server header field, the Via field
3969  was described as a SHOULD. The requirement was and is stated
3970  correctly in the description of the Via header field in &header-via;.
3971  (<xref target="header.server"/>)
3972</t>
3973</section>
3974
3975<?BEGININC p2-semantics.abnf-appendix ?>
3976<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3977<figure>
3978<artwork type="abnf" name="p2-semantics.parsed-abnf">
3979<x:ref>Allow</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3980
3981<x:ref>Date</x:ref> = HTTP-date
3982
3983<x:ref>Expect</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3984
3985<x:ref>From</x:ref> = mailbox
3986
3987<x:ref>GMT</x:ref> = %x47.4D.54 ; GMT
3988
3989<x:ref>HTTP-date</x:ref> = rfc1123-date / obs-date
3990
3991<x:ref>Location</x:ref> = URI-reference
3992
3993<x:ref>Max-Forwards</x:ref> = 1*DIGIT
3994<x:ref>Method</x:ref> = token
3995
3996<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
3997
3998<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3999<x:ref>Reason-Phrase</x:ref> = *( HTAB / SP / VCHAR / obs-text )
4000<x:ref>Referer</x:ref> = absolute-URI / partial-URI
4001<x:ref>Retry-After</x:ref> = HTTP-date / delta-seconds
4002
4003<x:ref>Server</x:ref> = product *( RWS ( product / comment ) )
4004<x:ref>Status-Code</x:ref> = 3DIGIT
4005
4006<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.7&gt;
4007<x:ref>User-Agent</x:ref> = product *( RWS ( product / comment ) )
4008
4009<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.7&gt;
4010<x:ref>asctime-date</x:ref> = day-name SP date3 SP time-of-day SP year
4011
4012<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2&gt;
4013
4014<x:ref>date1</x:ref> = day SP month SP year
4015<x:ref>date2</x:ref> = day "-" month "-" 2DIGIT
4016<x:ref>date3</x:ref> = month SP ( 2DIGIT / ( SP DIGIT ) )
4017<x:ref>day</x:ref> = 2DIGIT
4018<x:ref>day-name</x:ref> = %x4D.6F.6E ; Mon
4019 / %x54.75.65 ; Tue
4020 / %x57.65.64 ; Wed
4021 / %x54.68.75 ; Thu
4022 / %x46.72.69 ; Fri
4023 / %x53.61.74 ; Sat
4024 / %x53.75.6E ; Sun
4025<x:ref>day-name-l</x:ref> = %x4D.6F.6E.64.61.79 ; Monday
4026 / %x54.75.65.73.64.61.79 ; Tuesday
4027 / %x57.65.64.6E.65.73.64.61.79 ; Wednesday
4028 / %x54.68.75.72.73.64.61.79 ; Thursday
4029 / %x46.72.69.64.61.79 ; Friday
4030 / %x53.61.74.75.72.64.61.79 ; Saturday
4031 / %x53.75.6E.64.61.79 ; Sunday
4032<x:ref>delta-seconds</x:ref> = 1*DIGIT
4033
4034<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
4035<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
4036<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
4037 *expect-params ]
4038
4039<x:ref>hour</x:ref> = 2DIGIT
4040
4041<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
4042<x:ref>minute</x:ref> = 2DIGIT
4043<x:ref>month</x:ref> = %x4A.61.6E ; Jan
4044 / %x46.65.62 ; Feb
4045 / %x4D.61.72 ; Mar
4046 / %x41.70.72 ; Apr
4047 / %x4D.61.79 ; May
4048 / %x4A.75.6E ; Jun
4049 / %x4A.75.6C ; Jul
4050 / %x41.75.67 ; Aug
4051 / %x53.65.70 ; Sep
4052 / %x4F.63.74 ; Oct
4053 / %x4E.6F.76 ; Nov
4054 / %x44.65.63 ; Dec
4055
4056<x:ref>obs-date</x:ref> = rfc850-date / asctime-date
4057<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
4058
4059<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.7&gt;
4060<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 5.2&gt;
4061
4062<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 3.2.3&gt;
4063
4064<x:ref>rfc1123-date</x:ref> = day-name "," SP date1 SP time-of-day SP GMT
4065<x:ref>rfc850-date</x:ref> = day-name-l "," SP date2 SP time-of-day SP GMT
4066
4067<x:ref>second</x:ref> = 2DIGIT
4068
4069<x:ref>time-of-day</x:ref> = hour ":" minute ":" second
4070<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 3.2.3&gt;
4071
4072<x:ref>year</x:ref> = 4DIGIT
4073</artwork>
4074</figure>
4075<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
4076; Allow defined but not used
4077; Date defined but not used
4078; Expect defined but not used
4079; From defined but not used
4080; Location defined but not used
4081; Max-Forwards defined but not used
4082; Reason-Phrase defined but not used
4083; Referer defined but not used
4084; Retry-After defined but not used
4085; Server defined but not used
4086; Status-Code defined but not used
4087; User-Agent defined but not used
4088</artwork></figure></section>
4089<?ENDINC p2-semantics.abnf-appendix ?>
4090
4091<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
4092
4093<section title="Since RFC 2616">
4094<t>
4095  Extracted relevant partitions from <xref target="RFC2616"/>.
4096</t>
4097</section>
4098
4099<section title="Since draft-ietf-httpbis-p2-semantics-00">
4100<t>
4101  Closed issues:
4102  <list style="symbols"> 
4103    <t>
4104      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
4105      "Via is a MUST"
4106      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
4107    </t>
4108    <t>
4109      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
4110      "Fragments allowed in Location"
4111      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
4112    </t>
4113    <t>
4114      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
4115      "Safe Methods vs Redirection"
4116      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
4117    </t>
4118    <t>
4119      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
4120      "Revise description of the POST method"
4121      (<eref target="http://purl.org/NET/http-errata#post"/>)
4122    </t>
4123    <t>
4124      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
4125      "Normative and Informative references"
4126    </t>
4127    <t>
4128      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
4129      "RFC2606 Compliance"
4130    </t>
4131    <t>
4132      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
4133      "Informative references"
4134    </t>
4135    <t>
4136      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
4137      "Redundant cross-references"
4138    </t>
4139  </list>
4140</t>
4141<t>
4142  Other changes:
4143  <list style="symbols"> 
4144    <t>
4145      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
4146    </t>
4147  </list>
4148</t>
4149</section>
4150
4151<section title="Since draft-ietf-httpbis-p2-semantics-01">
4152<t>
4153  Closed issues:
4154  <list style="symbols"> 
4155    <t>
4156      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
4157      "PUT side effects"
4158    </t>
4159    <t>
4160      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
4161      "Duplicate Host header requirements"
4162    </t>
4163  </list>
4164</t>
4165<t>
4166  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4167  <list style="symbols"> 
4168    <t>
4169      Move "Product Tokens" section (back) into Part 1, as "token" is used
4170      in the definition of the Upgrade header field.
4171    </t>
4172    <t>
4173      Add explicit references to BNF syntax and rules imported from other parts of the specification.
4174    </t>
4175    <t>
4176      Copy definition of delta-seconds from Part6 instead of referencing it.
4177    </t>
4178  </list>
4179</t>
4180</section>
4181
4182<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
4183<t>
4184  Closed issues:
4185  <list style="symbols"> 
4186    <t>
4187      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
4188      "Requiring Allow in 405 responses"
4189    </t>
4190    <t>
4191      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
4192      "Status Code Registry"
4193    </t>
4194    <t>
4195      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
4196      "Redirection vs. Location"
4197    </t>
4198    <t>
4199      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
4200      "Cacheability of 303 response"
4201    </t>
4202    <t>
4203      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
4204      "305 Use Proxy"
4205    </t>
4206    <t>
4207      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
4208      "Classification for Allow header"
4209    </t>
4210    <t>
4211      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
4212      "PUT - 'store under' vs 'store at'"
4213    </t>
4214  </list>
4215</t>
4216<t>
4217  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
4218  <list style="symbols"> 
4219    <t>
4220      Reference RFC 3984, and update header field registrations for headers defined
4221      in this document.
4222    </t>
4223  </list>
4224</t>
4225<t>
4226  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4227  <list style="symbols"> 
4228    <t>
4229      Replace string literals when the string really is case-sensitive (method).
4230    </t>
4231  </list>
4232</t>
4233</section>
4234
4235<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
4236<t>
4237  Closed issues:
4238  <list style="symbols"> 
4239    <t>
4240      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
4241      "OPTIONS request bodies"
4242    </t>
4243    <t>
4244      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
4245      "Description of CONNECT should refer to RFC2817"
4246    </t>
4247    <t>
4248      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
4249      "Location Content-Location reference request/response mixup"
4250    </t>
4251  </list>
4252</t>
4253<t>
4254  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
4255  <list style="symbols"> 
4256    <t>
4257      Added initial proposal for registration process, plus initial
4258      content (non-HTTP/1.1 methods to be added by a separate specification).
4259    </t>
4260  </list>
4261</t>
4262</section>
4263
4264<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
4265<t>
4266  Closed issues:
4267  <list style="symbols"> 
4268    <t>
4269      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
4270      "Content-*"
4271    </t>
4272    <t>
4273      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
4274      "RFC 2822 is updated by RFC 5322"
4275    </t>
4276  </list>
4277</t>
4278<t>
4279  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4280  <list style="symbols"> 
4281    <t>
4282      Use "/" instead of "|" for alternatives.
4283    </t>
4284    <t>
4285      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
4286      whitespace ("OWS") and required whitespace ("RWS").
4287    </t>
4288    <t>
4289      Rewrite ABNFs to spell out whitespace rules, factor out
4290      header field value format definitions.
4291    </t>
4292  </list>
4293</t>
4294</section>
4295
4296<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
4297<t>
4298  Closed issues:
4299  <list style="symbols"> 
4300    <t>
4301      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
4302      "Reason-Phrase BNF"
4303    </t>
4304  </list>
4305</t>
4306<t>
4307  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
4308  <list style="symbols"> 
4309    <t>
4310      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
4311    </t>
4312  </list>
4313</t>
4314</section>
4315
4316<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
4317<t>
4318  Closed issues:
4319  <list style="symbols"> 
4320    <t>
4321      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
4322      "Clarify when Referer is sent"
4323    </t>
4324    <t>
4325      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
4326      "status codes vs methods"
4327    </t>
4328    <t>
4329      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
4330      "Do not require "updates" relation for specs that register status codes or method names"
4331    </t>
4332  </list>
4333</t>
4334</section>
4335
4336<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
4337<t>
4338  Closed issues:
4339  <list style="symbols"> 
4340    <t>
4341      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
4342      "Idempotency"
4343    </t>
4344    <t>
4345      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
4346      "TRACE security considerations"
4347    </t>
4348    <t>
4349      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
4350      "Clarify rules for determining what entities a response carries"
4351    </t>
4352    <t>
4353      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
4354      "update note citing RFC 1945 and 2068"
4355    </t>
4356    <t>
4357      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
4358      "update note about redirect limit"
4359    </t>
4360    <t>
4361      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
4362      "Location header ABNF should use 'URI'"
4363    </t>
4364    <t>
4365      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
4366      "fragments in Location vs status 303"
4367    </t>
4368    <t>
4369      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
4370      "move IANA registrations for optional status codes"
4371    </t>
4372  </list>
4373</t>
4374<t>
4375  Partly resolved issues:
4376  <list style="symbols"> 
4377    <t>
4378      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
4379      "Are OPTIONS and TRACE safe?"
4380    </t>
4381  </list>
4382</t>
4383</section>
4384
4385<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
4386<t>
4387  Closed issues:
4388  <list style="symbols"> 
4389    <t>
4390      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
4391      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
4392      status codes when fixing this previously)
4393    </t>
4394  </list>
4395</t>
4396</section>
4397
4398<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
4399<t>
4400  Closed issues:
4401  <list style="symbols"> 
4402    <t>
4403      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4404      "Fragment combination / precedence during redirects"
4405    </t>
4406  </list>
4407</t>
4408<t>
4409  Partly resolved issues:
4410  <list style="symbols"> 
4411    <t>
4412      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
4413      "Location header payload handling"
4414    </t>
4415    <t>
4416      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
4417      "Term for the requested resource's URI"
4418    </t>
4419  </list>
4420</t>
4421</section>
4422
4423<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
4424<t>
4425  Closed issues:
4426  <list style="symbols"> 
4427    <t>
4428      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
4429      "Clarify 'Requested Variant'"
4430    </t>
4431    <t>
4432      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
4433      "Clarify entity / representation / variant terminology"
4434    </t>
4435    <t>
4436      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/139"/>:
4437      "Methods and Caching"
4438    </t>
4439    <t>
4440      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/190"/>:
4441      "OPTIONS vs Max-Forwards"
4442    </t>
4443    <t>
4444      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/199"/>:
4445      "Status codes and caching"
4446    </t>
4447    <t>
4448      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
4449      "consider removing the 'changes from 2068' sections"
4450    </t>
4451  </list>
4452</t>
4453</section>
4454
4455<section title="Since draft-ietf-httpbis-p2-semantics-11" anchor="changes.since.11">
4456<t>
4457  Closed issues:
4458  <list style="symbols"> 
4459    <t>
4460      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/229"/>:
4461      "Considerations for new status codes"
4462    </t>
4463    <t>
4464      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/230"/>:
4465      "Considerations for new methods"
4466    </t>
4467    <t>
4468      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/232"/>:
4469      "User-Agent guidelines" (relating to the 'User-Agent' header field)
4470    </t>
4471  </list>
4472</t>
4473</section>
4474
4475<section title="Since draft-ietf-httpbis-p2-semantics-12" anchor="changes.since.12">
4476<t>
4477  Closed issues:
4478  <list style="symbols"> 
4479    <t>
4480      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4481      "Fragment combination / precedence during redirects" (added warning
4482      about having a fragid on the redirect may cause inconvenience in
4483      some cases)
4484    </t>
4485    <t>
4486      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/79"/>:
4487      "Content-* vs. PUT"
4488    </t>
4489    <t>
4490      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/88"/>:
4491      "205 Bodies"
4492    </t>
4493    <t>
4494      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/102"/>:
4495      "Understanding Content-* on non-PUT requests"
4496    </t>
4497    <t>
4498      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
4499      "Content-*"
4500    </t>
4501    <t>
4502      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/104"/>:
4503      "Header type defaulting"
4504    </t>
4505    <t>
4506      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
4507      "PUT - 'store under' vs 'store at'"
4508    </t>
4509    <t>
4510      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/137"/>:
4511      "duplicate ABNF for Reason-Phrase"
4512    </t>
4513    <t>
4514      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/180"/>:
4515      "Note special status of Content-* prefix in header registration procedures"
4516    </t>
4517    <t>
4518      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/203"/>:
4519      "Max-Forwards vs extension methods"
4520    </t>
4521    <t>
4522      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/213"/>:
4523      "What is the value space of HTTP status codes?" (actually fixed in
4524      draft-ietf-httpbis-p2-semantics-11)
4525    </t>
4526    <t>
4527      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/224"/>:
4528      "Header Classification"
4529    </t>
4530    <t>
4531      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/225"/>:
4532      "PUT side effect: invalidation or just stale?"
4533    </t>
4534    <t>
4535      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/226"/>:
4536      "proxies not supporting certain methods"
4537    </t>
4538    <t>
4539      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/239"/>:
4540      "Migrate CONNECT from RFC2817 to p2"
4541    </t>
4542    <t>
4543      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/240"/>:
4544      "Migrate Upgrade details from RFC2817"
4545    </t>
4546    <t>
4547      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/267"/>:
4548      "clarify PUT semantics'"
4549    </t>
4550    <t>
4551      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/275"/>:
4552      "duplicate ABNF for 'Method'"
4553    </t>
4554    <t>
4555      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4556      "untangle ABNFs for header fields"
4557    </t>
4558  </list>
4559</t>
4560</section>
4561
4562<section title="Since draft-ietf-httpbis-p2-semantics-13" anchor="changes.since.13">
4563<t>
4564  Closed issues:
4565  <list style="symbols"> 
4566    <t>
4567      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4568      "untangle ABNFs for header fields"
4569    </t>
4570    <t>
4571      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/251"/>:
4572      "message-body in CONNECT request"
4573    </t>
4574  </list>
4575</t>
4576</section>
4577
4578<section title="Since draft-ietf-httpbis-p2-semantics-14" anchor="changes.since.14">
4579<t>
4580  Closed issues:
4581  <list style="symbols"> 
4582    <t>
4583      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/255"/>:
4584      "Clarify status code for rate limiting"
4585    </t>
4586    <t>
4587      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/294"/>:
4588      "clarify 403 forbidden"
4589    </t>
4590    <t>
4591      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/296"/>:
4592      "Clarify 203 Non-Authoritative Information"
4593    </t>
4594    <t>
4595      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/298"/>:
4596      "update default reason phrase for 413"
4597    </t>
4598  </list>
4599</t>
4600</section>
4601
4602<section title="Since draft-ietf-httpbis-p2-semantics-15" anchor="changes.since.15">
4603<t>
4604  Closed issues:
4605  <list style="symbols"> 
4606    <t>
4607      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/285"/>:
4608      "Strength of requirements on Accept re: 406"
4609    </t>
4610    <t>
4611      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/303"/>:
4612      "400 response isn't generic"
4613    </t>
4614  </list>
4615</t>
4616</section>
4617
4618<section title="Since draft-ietf-httpbis-p2-semantics-16" anchor="changes.since.16">
4619<t>
4620  Closed issues:
4621  <list style="symbols"> 
4622    <t>
4623      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/160"/>:
4624      "Redirects and non-GET methods"
4625    </t>
4626    <t>
4627      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/310"/>:
4628      "clarify 303 redirect on HEAD"
4629    </t>
4630  </list>
4631</t>
4632<t>
4633  Work-in-progress:
4634  <list style="symbols"> 
4635    <t>
4636      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/231"/>:
4637      "Considerations for new headers"
4638    </t>
4639  </list>
4640</t>
4641</section>
4642
4643</section>
4644
4645</back>
4646</rfc>
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