source: draft-ietf-httpbis/latest/p2-semantics.xml @ 1417

Last change on this file since 1417 was 1417, checked in by julian.reschke@…, 8 years ago

add considerations for new header fields (see #231)

  • Property svn:eol-style set to native
File size: 174.4 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 "August">
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 notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
28  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
29  <!ENTITY field-rules                "<xref target='Part1' x:rel='#field.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY uri                        "<xref target='Part1' x:rel='#uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY effective-request-uri      "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY intermediaries             "<xref target='Part1' x:rel='#intermediaries' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY chunked-encoding           "<xref target='Part1' x:rel='#chunked.encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY full-date                  "<xref target='Part1' x:rel='#date.time.formats.full.date' 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="VCHAR"/>
323  <x:anchor-alias value="WSP"/>
324<t>
325  This specification uses the ABNF syntax defined in &notation; (which
326  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
327  <xref target="collected.abnf"/> shows the collected ABNF, with the list
328  rule expanded.
329</t>
330<t>
331  The following core rules are included by
332  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
333  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
334  DIGIT (decimal 0-9), DQUOTE (double quote),
335  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
336  OCTET (any 8-bit sequence of data), SP (space),
337  VCHAR (any visible USASCII character),
338  and WSP (whitespace).
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="HTTP-date"/>
363  <x:anchor-alias value="partial-URI"/>
364  <x:anchor-alias value="product"/>
365  <x:anchor-alias value="URI-reference"/>
366<t>
367  The ABNF rules below are defined in other parts:
368</t>
369<figure><!--Part1--><artwork type="abnf2616">
370  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
371  <x:ref>comment</x:ref>       = &lt;comment, defined in &header-fields;&gt;
372  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
373  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
374  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
375  <x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in &uri;&gt;
376</artwork></figure>
377</section>
378</section>
379</section>
380
381<section title="Method" anchor="method">
382  <x:anchor-alias value="Method"/>
383  <x:anchor-alias value="extension-method"/>
384<t>
385   The Method token indicates the request method to be performed on the target
386   resource (&effective-request-uri;). The method is case-sensitive.
387</t>
388<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/>
389  <x:ref>Method</x:ref>         = <x:ref>token</x:ref>
390</artwork></figure>
391<t>
392   The list of methods allowed by a resource can be specified in an
393   Allow header field (<xref target="header.allow"/>). The status code of the response
394   always notifies the client whether a method is currently allowed on a
395   resource, since the set of allowed methods can change dynamically. An
396   origin server &SHOULD; respond with the status code 405 (Method Not Allowed)
397   if the method is known by the origin server but not allowed for the
398   resource, and 501 (Not Implemented) if the method is
399   unrecognized or not implemented by the origin server. The methods GET
400   and HEAD &MUST; be supported by all general-purpose servers. All other
401   methods are &OPTIONAL;; however, if the above methods are implemented,
402   they &MUST; be implemented with the same semantics as those specified
403   in <xref target="method.definitions"/>.
404</t>
405
406<section title="Overview of Methods" anchor="overview.of.methods">
407<t>
408  The methods listed below are defined in <xref target="method.definitions"/>.
409</t>
410<texttable align="left">
411  <ttcol>Method Name</ttcol><ttcol>Defined in...</ttcol>
412 
413  <c>OPTIONS</c> <c><xref target="OPTIONS"/></c>
414  <c>GET</c> <c><xref target="GET"/></c>
415  <c>HEAD</c> <c><xref target="HEAD"/></c>
416  <c>POST</c> <c><xref target="POST"/></c>
417  <c>PUT</c> <c><xref target="PUT"/></c>
418  <c>DELETE</c> <c><xref target="DELETE"/></c>
419  <c>TRACE</c> <c><xref target="TRACE"/></c>
420  <c>CONNECT</c> <c><xref target="CONNECT"/></c>
421</texttable>
422<t>
423  Note that this list is not exhaustive &mdash; it does not include request methods defined
424  in other specifications.
425</t>
426</section>
427
428<section title="Method Registry" anchor="method.registry">
429<t>
430  The HTTP Method Registry defines the name space for the Method token in the
431  Request line of an HTTP request.
432</t>
433<t>
434  Registrations &MUST; include the following fields:
435  <list style="symbols">
436    <t>Method Name (see <xref target="method"/>)</t>
437    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
438    <t>Pointer to specification text</t>
439  </list>
440</t>
441<t>
442  Values to be added to this name space are subject to IETF review
443  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
444</t>
445<t>
446  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
447</t>
448
449<section title="Considerations for New Methods" anchor="considerations.for.new.methods">
450<t>
451   When it is necessary to express new semantics for a HTTP request that
452   aren't specific to a single application or media type, and currently defined
453   methods are inadequate, it may be appropriate to register a new method.
454</t>
455<t>
456   HTTP methods are generic; that is, they are potentially applicable to any
457   resource, not just one particular media type, "type" of resource, or
458   application. As such, it is preferred that new HTTP methods be registered
459   in a document that isn't specific to a single application, so that this is
460   clear.
461</t>
462<t>
463   Due to the parsing rules defined in &message-body;, definitions of HTTP
464   methods cannot prohibit the presence of a message-body on either the request
465   or the response message (with responses to HEAD requests being the single
466   exception). Definitions of new methods cannot change this rule, but they can
467   specify that only zero-length bodies (as opposed to absent bodies) are allowed.
468</t>
469<t>
470   New method definitions need to indicate whether they are safe (<xref
471   target="safe.methods"/>), what semantics (if any) the request body has,
472   and whether they are idempotent (<xref target="idempotent.methods"/>).
473   They also need to state whether they can be cached (&caching;); in
474   particular what conditions a cache may store the response, and under what
475   conditions such a stored response may be used to satisfy a subsequent
476   request.
477</t>
478</section>
479
480</section>
481</section>
482
483<section title="Header Fields" anchor="header.fields">
484<t>
485   Header fields are key value pairs that can be used to communicate data about
486   the message, its payload, the target resource, or about the connection
487   itself (i.e., control data).  See &header-fields; for a general definition
488   of their syntax.
489</t>
490
491<section title="Considerations for Creating Header Fields" anchor="considerations.for.creating.header.fields">
492<t>
493   New header fields are registered using the procedures described in
494   <xref target="RFC3864"/>.
495</t>
496<t>
497   The requirements for header field names are defined in
498   <xref target="RFC3864" x:fmt="of" x:sec="4.1"/>.  Authors of specifications
499   defining new fields are advised to keep the name as short as practical, and
500   not to prefix them with "X-" if they are to be registered (either
501   immediately or in the future).
502</t>
503<t>
504   New header field values typically have their syntax defined using ABNF
505   (<xref target="RFC5234"/>), using the extensions defined in &notation-abnf;
506   as necessary, and are usually constrained to the range of ASCII characters.
507   Header fields needing a greater range of characters can use an encoding
508   such as the one defined in <xref target="RFC5987"/>.
509</t>
510<t>
511   Because commas (",") are used as a generic delimiter between field-values,
512   they need to be treated with care if they are allowed in the field-value's
513   payload. Typically, components that might contain a comma are protected with
514   double-quotes using the quoted-string ABNF production (&field-rules;).
515</t>
516<t>
517   For example, a textual date and a URI (either of which might contain a comma)
518   could be safely carried in field-values like these:
519</t>
520<figure><artwork type="example">
521  Example-URI-Field: "http://example.com/a.html,foo",
522                     "http://without-a-comma.example.com/"
523  Example-Date-Field: "Sat, 04 May 1996", "Wed, 14 Sep 2005"
524</artwork></figure>
525<t>
526   Authors of specifications defining new header fields are advised to consider
527   documenting:
528  <list style="symbols">
529    <t>Whether the field is a single value, or whether it can be a list
530    (delimited by commas; see &header-fields;).</t>
531    <t>Under what conditions the header field can be used; e.g., only i
532    responses or requests, in all messages, only on responses to a particular
533    request method.</t>
534    <t>Whether it is appropriate to list the field-name in the Connection header
535    (i.e., if the header is to be hop-by-hop, see &header-connection;).</t>
536    <t>Under what conditions intermediaries are allowed to modify the header
537    field's value, insert or delete it.</t>
538    <t>How the header might interact with caching (see <xref target="Part6"/>).</t>
539    <t>Whether the header field is useful or allowable in trailers (see
540    &chunked-encoding;).</t>
541    <t>Whether the header field should be preserved across redirects.</t>
542  </list>
543</t>
544</section>
545
546<section title="Request Header Fields" anchor="request.header.fields">
547  <x:anchor-alias value="request-header"/>
548<t>
549   The request header fields allow the client to pass additional
550   information about the request, and about the client itself, to the
551   server. These fields act as request modifiers, with semantics
552   equivalent to the parameters on a programming language method
553   invocation.
554</t>
555<texttable align="left">
556  <ttcol>Header Field Name</ttcol>
557  <ttcol>Defined in...</ttcol>
558
559  <c>Accept</c> <c>&header-accept;</c>
560  <c>Accept-Charset</c> <c>&header-accept-charset;</c>
561  <c>Accept-Encoding</c> <c>&header-accept-encoding;</c>
562  <c>Accept-Language</c> <c>&header-accept-language;</c>
563  <c>Authorization</c> <c>&header-authorization;</c>
564  <c>Expect</c> <c><xref target="header.expect"/></c>
565  <c>From</c> <c><xref target="header.from"/></c>
566  <c>Host</c> <c>&header-host;</c>
567  <c>If-Match</c> <c>&header-if-match;</c>
568  <c>If-Modified-Since</c> <c>&header-if-modified-since;</c>
569  <c>If-None-Match</c> <c>&header-if-none-match;</c>
570  <c>If-Range</c> <c>&header-if-range;</c>
571  <c>If-Unmodified-Since</c> <c>&header-if-unmodified-since;</c>
572  <c>Max-Forwards</c> <c><xref target="header.max-forwards"/></c>
573  <c>Proxy-Authorization</c> <c>&header-proxy-authorization;</c>
574  <c>Range</c> <c>&header-range;</c>
575  <c>Referer</c> <c><xref target="header.referer"/></c>
576  <c>TE</c> <c>&header-te;</c>
577  <c>User-Agent</c> <c><xref target="header.user-agent"/></c>
578</texttable>
579</section>
580
581<section title="Response Header Fields" anchor="response.header.fields">
582  <x:anchor-alias value="response-header"/>
583<t>
584   The response header fields allow the server to pass additional
585   information about the response which cannot be placed in the Status-Line.
586   These header fields give information about the server and about
587   further access to the target resource (&effective-request-uri;).
588</t>
589<texttable align="left">
590  <ttcol>Header Field Name</ttcol><ttcol>Defined in...</ttcol>
591
592  <c>Accept-Ranges</c> <c>&header-accept-ranges;</c>
593  <c>Age</c> <c>&header-age;</c>
594  <c>Allow</c> <c><xref target="header.allow"/></c>
595  <c>ETag</c> <c>&header-etag;</c>
596  <c>Location</c> <c><xref target="header.location"/></c>
597  <c>Proxy-Authenticate</c> <c>&header-proxy-authenticate;</c>
598  <c>Retry-After</c> <c><xref target="header.retry-after"/></c>
599  <c>Server</c> <c><xref target="header.server"/></c>
600  <c>Vary</c> <c>&header-vary;</c>
601  <c>WWW-Authenticate</c> <c>&header-www-authenticate;</c>
602</texttable>
603</section>
604
605</section>
606
607<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
608  <x:anchor-alias value="Reason-Phrase"/>
609  <x:anchor-alias value="Status-Code"/>
610  <x:anchor-alias value="extension-code"/>
611<t>
612   The Status-Code element is a 3-digit integer result code of the attempt to
613   understand and satisfy the request.
614</t>
615<t>
616   The Reason-Phrase is intended to give a short textual description of the
617   Status-Code and is intended for a human user. The client does not need
618   to examine or display the Reason-Phrase.
619</t>
620<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"/>
621  <x:ref>Status-Code</x:ref>    = 3<x:ref>DIGIT</x:ref>
622  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
623</artwork></figure>
624<t>
625   HTTP status codes are extensible. HTTP applications are not required
626   to understand the meaning of all registered status codes, though such
627   understanding is obviously desirable. However, applications &MUST;
628   understand the class of any status code, as indicated by the first
629   digit, and treat any unrecognized response as being equivalent to the
630   x00 status code of that class, with the exception that an
631   unrecognized response &MUST-NOT; be cached. For example, if an
632   unrecognized status code of 431 is received by the client, it can
633   safely assume that there was something wrong with its request and
634   treat the response as if it had received a 400 status code. In such
635   cases, user agents &SHOULD; present to the user the representation enclosed
636   with the response, since that representation is likely to include human-readable
637   information which will explain the unusual status.
638</t>
639
640<section title="Overview of Status Codes" anchor="overview.of.status.codes">
641<t> 
642   The status codes listed below are defined in <xref target="status.codes"/>
643   of this specification, &p4-status-codes;, &p5-status-codes;, and &p7-status-codes;.
644   The reason phrases listed here are only recommendations &mdash; they can be
645   replaced by local equivalents without affecting the protocol.
646</t>
647<texttable align="left">
648  <ttcol>Status-Code</ttcol>
649  <ttcol>Reason-Phrase</ttcol>
650  <ttcol>Defined in...</ttcol>
651 
652  <c>100</c> <c>Continue</c> <c><xref target="status.100"/></c>
653  <c>101</c> <c>Switching Protocols</c> <c><xref target="status.101"/></c>
654
655  <c>200</c> <c>OK</c> <c><xref target="status.200"/></c>
656  <c>201</c> <c>Created</c> <c><xref target="status.201"/></c>
657  <c>202</c> <c>Accepted</c> <c><xref target="status.202"/></c>
658  <c>203</c> <c>Non-Authoritative Information</c> <c><xref target="status.203"/></c>
659  <c>204</c> <c>No Content</c> <c><xref target="status.204"/></c>
660  <c>205</c> <c>Reset Content</c> <c><xref target="status.205"/></c>
661  <c>206</c> <c>Partial Content</c> <c>&status-206;</c>
662
663  <c>300</c> <c>Multiple Choices</c> <c><xref target="status.300"/></c>
664  <c>301</c> <c>Moved Permanently</c> <c><xref target="status.301"/></c>
665  <c>302</c> <c>Found</c> <c><xref target="status.302"/></c>
666  <c>303</c> <c>See Other</c> <c><xref target="status.303"/></c>
667  <c>304</c> <c>Not Modified</c> <c>&status-304;</c>
668  <c>305</c> <c>Use Proxy</c> <c><xref target="status.305"/></c>
669  <c>307</c> <c>Temporary Redirect</c> <c><xref target="status.307"/></c>
670
671  <c>400</c> <c>Bad Request</c> <c><xref target="status.400"/></c>
672  <c>401</c> <c>Unauthorized</c> <c>&status-401;</c>
673  <c>402</c> <c>Payment Required</c> <c><xref target="status.402"/></c>
674  <c>403</c> <c>Forbidden</c> <c><xref target="status.403"/></c>
675  <c>404</c> <c>Not Found</c> <c><xref target="status.404"/></c>
676  <c>405</c> <c>Method Not Allowed</c> <c><xref target="status.405"/></c>
677  <c>406</c> <c>Not Acceptable</c> <c><xref target="status.406"/></c>
678  <c>407</c> <c>Proxy Authentication Required</c> <c>&status-407;</c>
679  <c>408</c> <c>Request Time-out</c> <c><xref target="status.408"/></c>
680  <c>409</c> <c>Conflict</c> <c><xref target="status.409"/></c>
681  <c>410</c> <c>Gone</c> <c><xref target="status.410"/></c>
682  <c>411</c> <c>Length Required</c> <c><xref target="status.411"/></c>
683  <c>412</c> <c>Precondition Failed</c> <c>&status-412;</c>
684  <c>413</c> <c>Request Representation Too Large</c> <c><xref target="status.413"/></c>
685  <c>414</c> <c>URI Too Long</c> <c><xref target="status.414"/></c>
686  <c>415</c> <c>Unsupported Media Type</c> <c><xref target="status.415"/></c>
687  <c>416</c> <c>Requested range not satisfiable</c> <c>&status-416;</c>
688  <c>417</c> <c>Expectation Failed</c> <c><xref target="status.417"/></c>
689  <c>426</c> <c>Upgrade Required</c> <c><xref target="status.426"/></c>
690
691  <c>500</c> <c>Internal Server Error</c> <c><xref target="status.500"/></c>
692  <c>501</c> <c>Not Implemented</c> <c><xref target="status.501"/></c>
693  <c>502</c> <c>Bad Gateway</c> <c><xref target="status.502"/></c>
694  <c>503</c> <c>Service Unavailable</c> <c><xref target="status.503"/></c>
695  <c>504</c> <c>Gateway Time-out</c> <c><xref target="status.504"/></c>
696  <c>505</c> <c>HTTP Version not supported</c> <c><xref target="status.505"/></c>
697</texttable>
698<t>
699   Note that this list is not exhaustive &mdash; it does not include
700   extension status codes defined in other specifications.
701</t>
702</section>
703
704<section title="Status Code Registry" anchor="status.code.registry">
705<t>
706  The HTTP Status Code Registry defines the name space for the Status-Code
707  token in the Status-Line of an HTTP response.
708</t>
709<t>
710  Values to be added to this name space are subject to IETF review
711  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
712</t>
713<t>
714  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
715</t>
716
717<section title="Considerations for New Status Codes" anchor="considerations.for.new.status.codes">
718<t>
719   When it is necessary to express new semantics for a HTTP response that
720   aren't specific to a single application or media type, and currently defined
721   status codes are inadequate, a new status code can be registered.
722</t>
723<t>
724   HTTP status codes are generic; that is, they are potentially applicable to
725   any resource, not just one particular media type, "type" of resource, or
726   application. As such, it is preferred that new HTTP status codes be
727   registered in a document that isn't specific to a single application, so
728   that this is clear.
729</t>
730<t>
731   Definitions of new HTTP status codes typically explain the request
732   conditions that produce a response containing the status code (e.g.,
733   combinations of request headers and/or method(s)), along with any
734   interactions with response headers (e.g., those that are required, those
735   that modify the semantics of the response).
736</t>
737<t>
738   New HTTP status codes are required to fall under one of the categories
739   defined in <xref target="status.codes"/>. To allow existing parsers to
740   properly handle them, new status codes cannot disallow a response body,
741   although they can mandate a zero-length response body. They can require the
742   presence of one or more particular HTTP response header(s).
743</t>
744<t>
745   Likewise, their definitions can specify that caches are allowed to use
746   heuristics to determine their freshness (see &caching;; by default, it is
747   not allowed), and can define how to determine the resource which they
748   carry a representation for (see <xref
749   target="identifying.response.associated.with.representation"/>; by default,
750   it is anonymous).
751</t>
752</section>
753
754</section>
755
756</section>
757
758<section title="Representation" anchor="representation">
759<t>
760   Request and Response messages &MAY; transfer a representation if not otherwise
761   restricted by the request method or response status code. A representation
762   consists of metadata (representation header fields) and data (representation
763   body).  When a complete or partial representation is enclosed in an HTTP message,
764   it is referred to as the payload of the message. HTTP representations
765   are defined in &payload;.
766</t>
767<t>
768   A representation body is only present in a message when a message-body is
769   present, as described in &message-body;. The representation body is obtained
770   from the message-body by decoding any Transfer-Encoding that might
771   have been applied to ensure safe and proper transfer of the message.
772</t>
773
774<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
775<t>
776   It is sometimes necessary to determine an identifier for the resource
777   associated with a representation.
778</t>
779<t>
780   An HTTP request representation, when present, is always associated with an
781   anonymous (i.e., unidentified) resource.
782</t>
783<t>
784   In the common case, an HTTP response is a representation of the target
785   resource (see &effective-request-uri;). However, this is not always the
786   case. To determine the URI of the resource a response is associated with,
787   the following rules are used (with the first applicable one being selected):
788</t>
789<t><list style="numbers">
790   <t>If the response status code is 200 or 203 and the request method was GET,
791   the response payload is a representation of the target resource.</t>
792   <t>If the response status code is 204, 206, or 304 and the request method was GET
793   or HEAD, the response payload is a partial representation of the target
794   resource.</t>
795   <t>If the response has a Content-Location header field, and that URI is the same
796   as the effective request URI, the response payload is a representation of the
797   target resource.</t>
798   <t>If the response has a Content-Location header field, and that URI is not the
799   same as the effective request URI, then the response asserts that its
800   payload is a representation of the resource identified by the
801   Content-Location URI. However, such an assertion cannot be trusted unless
802   it can be verified by other means (not defined by HTTP).</t>
803   <t>Otherwise, the response is a representation of an anonymous (i.e.,
804   unidentified) resource.</t>
805</list></t>
806<t>
807  <cref anchor="TODO-req-uri">
808   The comparison function is going to have to be defined somewhere,
809   because we already need to compare URIs for things like cache invalidation.</cref>
810</t>
811</section>
812
813</section>
814
815
816<section title="Method Definitions" anchor="method.definitions">
817<t>
818   The set of common request methods for HTTP/1.1 is defined below. Although
819   this set can be expanded, additional methods cannot be assumed to
820   share the same semantics for separately extended clients and servers.
821</t>
822
823<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
824
825<section title="Safe Methods" anchor="safe.methods">
826<iref item="Safe Methods" primary="true"/>
827<t>
828   Implementors need to be aware that the software represents the user in
829   their interactions over the Internet, and need to allow
830   the user to be aware of any actions they take which might have an
831   unexpected significance to themselves or others.
832</t>
833<t>
834   In particular, the convention has been established that the GET, HEAD,
835   OPTIONS, and TRACE request methods &SHOULD-NOT; have the significance
836   of taking an action other than retrieval. These request methods ought
837   to be considered "<x:dfn anchor="safe">safe</x:dfn>".
838   This allows user agents to represent other methods, such as POST, PUT
839   and DELETE, in a special way, so that the user is made aware of the
840   fact that a possibly unsafe action is being requested.
841</t>
842<t>
843   Naturally, it is not possible to ensure that the server does not
844   generate side-effects as a result of performing a GET request; in
845   fact, some dynamic resources consider that a feature. The important
846   distinction here is that the user did not request the side-effects,
847   so therefore cannot be held accountable for them.
848</t>
849</section>
850
851<section title="Idempotent Methods" anchor="idempotent.methods">
852<iref item="Idempotent Methods" primary="true"/>
853<t>
854   Request methods can also have the property of "idempotence" in that,
855   aside from error or expiration issues, the intended effect of multiple
856   identical requests is the same as for a single request.
857   PUT, DELETE, and all safe request methods are idempotent.
858   It is important to note that idempotence refers only to changes
859   requested by the client: a server is free to change its state due
860   to multiple requests for the purpose of tracking those requests,
861   versioning of results, etc.
862</t>
863</section>
864</section>
865
866<section title="OPTIONS" anchor="OPTIONS">
867  <rdf:Description>
868    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
869  </rdf:Description>
870  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
871  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
872<t>
873   The OPTIONS method requests information about the
874   communication options available on the request/response chain
875   identified by the effective request URI. This method allows a client to
876   determine the options and/or requirements associated with a resource,
877   or the capabilities of a server, without implying a resource action
878   or initiating a resource retrieval.
879</t>
880<t>
881   Responses to the OPTIONS method are not cacheable.
882</t>
883<t>
884   If the OPTIONS request includes a message-body (as indicated by the
885   presence of Content-Length or Transfer-Encoding), then the media type
886   &MUST; be indicated by a Content-Type field. Although this
887   specification does not define any use for such a body, future
888   extensions to HTTP might use the OPTIONS body to make more detailed
889   queries on the server.
890</t>
891<t>
892   If the request-target is an asterisk ("*"), the OPTIONS request is
893   intended to apply to the server in general rather than to a specific
894   resource. Since a server's communication options typically depend on
895   the resource, the "*" request is only useful as a "ping" or "no-op"
896   type of method; it does nothing beyond allowing the client to test
897   the capabilities of the server. For example, this can be used to test
898   a proxy for HTTP/1.1 compliance (or lack thereof).
899</t>
900<t>
901   If the request-target is not an asterisk, the OPTIONS request applies
902   only to the options that are available when communicating with that
903   resource.
904</t>
905<t>
906   A 200 response &SHOULD; include any header fields that indicate
907   optional features implemented by the server and applicable to that
908   resource (e.g., Allow), possibly including extensions not defined by
909   this specification. The response body, if any, &SHOULD; also include
910   information about the communication options. The format for such a
911   body is not defined by this specification, but might be defined by
912   future extensions to HTTP. Content negotiation &MAY; be used to select
913   the appropriate response format. If no response body is included, the
914   response &MUST; include a Content-Length field with a field-value of
915   "0".
916</t>
917<t>
918   The Max-Forwards header field &MAY; be used to target a
919   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
920   If no Max-Forwards field is present in the request, then the forwarded
921   request &MUST-NOT; include a Max-Forwards field.
922</t>
923</section>
924
925<section title="GET" anchor="GET">
926  <rdf:Description>
927    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
928  </rdf:Description>
929  <iref primary="true" item="GET method" x:for-anchor=""/>
930  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
931<t>
932   The GET method requests transfer of a current representation of
933   the target resource.
934</t>
935<t>   
936   If the target resource is a data-producing process, it is the
937   produced data which shall be returned as the representation in the response and not
938   the source text of the process, unless that text happens to be the output of
939   the process.
940</t>
941<t>
942   The semantics of the GET method change to a "conditional GET" if the
943   request message includes an If-Modified-Since, If-Unmodified-Since,
944   If-Match, If-None-Match, or If-Range header field. A conditional GET
945   requests that the representation be transferred only under the
946   circumstances described by the conditional header field(s). The
947   conditional GET request is intended to reduce unnecessary network
948   usage by allowing cached representations to be refreshed without requiring
949   multiple requests or transferring data already held by the client.
950</t>
951<t>
952   The semantics of the GET method change to a "partial GET" if the
953   request message includes a Range header field. A partial GET requests
954   that only part of the representation be transferred, as described in &header-range;.
955   The partial GET request is intended to reduce unnecessary
956   network usage by allowing partially-retrieved representations to be
957   completed without transferring data already held by the client.
958</t>
959<t>
960   Bodies on GET requests have no defined semantics. Note that sending a body
961   on a GET request might cause some existing implementations to reject the
962   request.
963</t>
964<t>
965   The response to a GET request is cacheable and &MAY; be used to satisfy
966   subsequent GET and HEAD requests (see &caching;).
967</t>
968<t>
969   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
970</t>
971</section>
972
973<section title="HEAD" anchor="HEAD">
974  <rdf:Description>
975    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
976  </rdf:Description>
977  <iref primary="true" item="HEAD method" x:for-anchor=""/>
978  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
979<t>
980   The HEAD method is identical to GET except that the server &MUST-NOT;
981   return a message-body in the response. The metadata contained
982   in the HTTP header fields in response to a HEAD request &SHOULD; be identical
983   to the information sent in response to a GET request. This method can
984   be used for obtaining metadata about the representation implied by the
985   request without transferring the representation body. This method is
986   often used for testing hypertext links for validity, accessibility,
987   and recent modification.
988</t>
989<t>
990   The response to a HEAD request is cacheable and &MAY; be used to satisfy
991   a subsequent HEAD request; see &caching;. It also &MAY; be used to update a previously cached
992   representation from that resource; if the new field values
993   indicate that the cached representation differs from the current representation (as
994   would be indicated by a change in Content-Length, ETag
995   or Last-Modified), then the cache &MUST; treat the cache entry as
996   stale.
997</t>
998<t>
999   Bodies on HEAD requests have no defined semantics. Note that sending a body
1000   on a HEAD request might cause some existing implementations to reject the
1001   request.
1002</t>
1003</section>
1004
1005<section title="POST" anchor="POST">
1006  <iref primary="true" item="POST method" x:for-anchor=""/>
1007  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
1008<t>
1009   The POST method requests that the origin server accept the
1010   representation enclosed in the request as data to be processed by the
1011   target resource. POST is designed to allow a uniform method to cover the
1012   following functions:
1013  <list style="symbols">
1014    <t>
1015      Annotation of existing resources;
1016    </t>
1017    <t>
1018        Posting a message to a bulletin board, newsgroup, mailing list,
1019        or similar group of articles;
1020    </t>
1021    <t>
1022        Providing a block of data, such as the result of submitting a
1023        form, to a data-handling process;
1024    </t>
1025    <t>
1026        Extending a database through an append operation.
1027    </t>
1028  </list>
1029</t>
1030<t>
1031   The actual function performed by the POST method is determined by the
1032   server and is usually dependent on the effective request URI.
1033</t>
1034<t>
1035   The action performed by the POST method might not result in a
1036   resource that can be identified by a URI. In this case, either 200
1037   (OK) or 204 (No Content) is the appropriate response status code,
1038   depending on whether or not the response includes a representation that
1039   describes the result.
1040</t>
1041<t>
1042   If a resource has been created on the origin server, the response
1043   &SHOULD; be 201 (Created) and contain a representation which describes the
1044   status of the request and refers to the new resource, and a Location
1045   header field (see <xref target="header.location"/>).
1046</t>
1047<t>
1048   Responses to POST requests are only cacheable when they
1049   include explicit freshness information (see &p6-explicit;). A
1050   cached POST response with a Content-Location header field
1051   (see &header-content-location;) whose value is the effective
1052   Request URI &MAY; be used to satisfy subsequent GET and HEAD requests.
1053</t>
1054<t>
1055   Note that POST caching is not widely implemented.
1056   However, the 303 (See Other) response can be used to direct the
1057   user agent to retrieve a cacheable resource.
1058</t>
1059</section>
1060
1061<section title="PUT" anchor="PUT">
1062  <iref primary="true" item="PUT method" x:for-anchor=""/>
1063  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
1064<t>
1065   The PUT method requests that the state of the target resource
1066   be created or replaced with the state defined by the representation
1067   enclosed in the request message payload.  A successful PUT of a given
1068   representation would suggest that a subsequent GET on that same target
1069   resource will result in an equivalent representation being returned in
1070   a 200 (OK) response.  However, there is no guarantee that such a state
1071   change will be observable, since the target resource might be acted
1072   upon by other user agents in parallel, or might be subject to dynamic
1073   processing by the origin server, before any subsequent GET is received.
1074   A successful response only implies that the user agent's intent was
1075   achieved at the time of its processing by the origin server.
1076</t>
1077<t>   
1078   If the target resource does not have a current representation and
1079   the PUT successfully creates one, then the origin server &MUST; inform
1080   the user agent by sending a 201 (Created) response.  If the target
1081   resource does have a current representation and that representation is
1082   successfully modified in accordance with the state of the enclosed
1083   representation, then either a 200 (OK) or 204 (No Content) response
1084   &SHOULD; be sent to indicate successful completion of the request.
1085</t>
1086<t>
1087   Unrecognized header fields &SHOULD; be ignored (i.e., not saved
1088   as part of the resource state).
1089</t>
1090<t>
1091   An origin server &SHOULD; verify that the PUT representation is
1092   consistent with any constraints which the server has for the target
1093   resource that cannot or will not be changed by the PUT.  This is
1094   particularly important when the origin server uses internal
1095   configuration information related to the URI in order to set the
1096   values for representation metadata on GET responses.  When a PUT
1097   representation is inconsistent with the target resource, the origin
1098   server &SHOULD; either make them consistent, by transforming the
1099   representation or changing the resource configuration, or respond
1100   with an appropriate error message containing sufficient information
1101   to explain why the representation is unsuitable.  The 409 (Conflict)
1102   or 415 (Unsupported Media Type) status codes are suggested, with the
1103   latter being specific to constraints on Content-Type values.
1104</t>
1105<t>
1106   For example, if the target resource is configured to always have a
1107   Content-Type of "text/html" and the representation being PUT has a
1108   Content-Type of "image/jpeg", then the origin server &SHOULD; do one of:
1109   (a) reconfigure the target resource to reflect the new media type;
1110   (b) transform the PUT representation to a format consistent with that
1111   of the resource before saving it as the new resource state; or,
1112   (c) reject the request with a 415 response indicating that the target
1113   resource is limited to "text/html", perhaps including a link to a
1114   different resource that would be a suitable target for the new
1115   representation.
1116</t>
1117<t>
1118   HTTP does not define exactly how a PUT method affects the state
1119   of an origin server beyond what can be expressed by the intent of
1120   the user agent request and the semantics of the origin server response.
1121   It does not define what a resource might be, in any sense of that
1122   word, beyond the interface provided via HTTP.  It does not define
1123   how resource state is "stored", nor how such storage might change
1124   as a result of a change in resource state, nor how the origin server
1125   translates resource state into representations.  Generally speaking,
1126   all implementation details behind the resource interface are
1127   intentionally hidden by the server.
1128</t>
1129<t>
1130   The fundamental difference between the POST and PUT methods is
1131   highlighted by the different intent for the target resource.
1132   The target resource in a POST request is intended to handle the
1133   enclosed representation as a data-accepting process, such as for
1134   a gateway to some other protocol or a document that accepts annotations.
1135   In contrast, the target resource in a PUT request is intended to
1136   take the enclosed representation as a new or replacement value.
1137   Hence, the intent of PUT is idempotent and visible to intermediaries,
1138   even though the exact effect is only known by the origin server.
1139</t>
1140<t>
1141   Proper interpretation of a PUT request presumes that the user agent
1142   knows what target resource is desired.  A service that is intended
1143   to select a proper URI on behalf of the client, after receiving
1144   a state-changing request, &SHOULD; be implemented using the POST
1145   method rather than PUT.  If the origin server will not make the
1146   requested PUT state change to the target resource and instead
1147   wishes to have it applied to a different resource, such as when the
1148   resource has been moved to a different URI, then the origin server
1149   &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
1150   then make its own decision regarding whether or not to redirect the
1151   request.
1152</t>
1153<t>
1154   A PUT request applied to the target resource &MAY; have side-effects
1155   on other resources.  For example, an article might have a URI for
1156   identifying "the current version" (a resource) which is separate
1157   from the URIs identifying each particular version (different
1158   resources that at one point shared the same state as the current version
1159   resource).  A successful PUT request on "the current version" URI might
1160   therefore create a new version resource in addition to changing the
1161   state of the target resource, and might also cause links to be added
1162   between the related resources.
1163</t>
1164<t>
1165   An origin server &SHOULD; reject any PUT request that contains a
1166   Content-Range header field, since it might be misinterpreted as
1167   partial content (or might be partial content that is being mistakenly
1168   PUT as a full representation).  Partial content updates are
1169   possible by targeting a separately identified resource with state
1170   that overlaps a portion of the larger resource, or by using a
1171   different method that has been specifically defined for partial
1172   updates (for example, the PATCH method defined in
1173   <xref target="RFC5789"/>).
1174</t>
1175<t>
1176   Responses to the PUT method are not cacheable. If a PUT request passes
1177   through a cache that has one or more stored responses for the effective
1178   request URI, those stored responses will be invalidated (see
1179   &p6-invalid;).
1180</t>
1181</section>
1182
1183<section title="DELETE" anchor="DELETE">
1184  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1185  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1186<t>
1187   The DELETE method requests that the origin server delete the target
1188   resource. This method &MAY; be overridden by
1189   human intervention (or other means) on the origin server. The client cannot
1190   be guaranteed that the operation has been carried out, even if the
1191   status code returned from the origin server indicates that the action
1192   has been completed successfully. However, the server &SHOULD-NOT; 
1193   indicate success unless, at the time the response is given, it
1194   intends to delete the resource or move it to an inaccessible
1195   location.
1196</t>
1197<t>
1198   A successful response &SHOULD; be 200 (OK) if the response includes an
1199   representation describing the status, 202 (Accepted) if the action has not
1200   yet been enacted, or 204 (No Content) if the action has been enacted
1201   but the response does not include a representation.
1202</t>
1203<t>
1204   Bodies on DELETE requests have no defined semantics. Note that sending a body
1205   on a DELETE request might cause some existing implementations to reject the
1206   request.
1207</t>
1208<t>
1209   Responses to the DELETE method are not cacheable. If a DELETE request
1210   passes through a cache that has one or more stored responses for the
1211   effective request URI, those stored responses will be invalidated (see
1212   &p6-invalid;).
1213</t>
1214</section>
1215
1216<section title="TRACE" anchor="TRACE">
1217  <rdf:Description>
1218    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1219  </rdf:Description>
1220  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1221  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1222<t>
1223   The TRACE method requests a remote, application-layer loop-back
1224   of the request message. The final recipient of the request
1225   &SHOULD; reflect the message received back to the client as the
1226   message-body of a 200 (OK) response. The final recipient is either the
1227   origin server or the first proxy to receive a Max-Forwards
1228   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1229   A TRACE request &MUST-NOT; include a message-body.
1230</t>
1231<t>
1232   TRACE allows the client to see what is being received at the other
1233   end of the request chain and use that data for testing or diagnostic
1234   information. The value of the Via header field (&header-via;) is of
1235   particular interest, since it acts as a trace of the request chain.
1236   Use of the Max-Forwards header field allows the client to limit the
1237   length of the request chain, which is useful for testing a chain of
1238   proxies forwarding messages in an infinite loop.
1239</t>
1240<t>
1241   If the request is valid, the response &SHOULD; have a Content-Type of
1242   "message/http" (see &media-type-message-http;) and contain a message-body
1243   that encloses a copy of the entire request message.
1244   Responses to the TRACE method are not cacheable.
1245</t>
1246</section>
1247
1248<section title="CONNECT" anchor="CONNECT">
1249  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1250  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1251<t>
1252   The CONNECT method requests that the proxy establish a tunnel
1253   to the request-target and then restrict its behavior to blind
1254   forwarding of packets until the connection is closed.
1255</t>
1256<t>
1257   When using CONNECT, the request-target &MUST; use the authority form
1258   (&request-target;); i.e., the request-target consists of only the
1259   host name and port number of the tunnel destination, separated by a colon.
1260   For example,
1261</t>
1262<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1263CONNECT server.example.com:80 HTTP/1.1
1264Host: server.example.com:80
1265
1266</artwork></figure>
1267<t>
1268   Other HTTP mechanisms can be used normally with the CONNECT method &mdash;
1269   except end-to-end protocol Upgrade requests, since the
1270   tunnel must be established first.
1271</t>
1272<t>
1273   For example, proxy authentication might be used to establish the
1274   authority to create a tunnel:
1275</t>
1276<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1277CONNECT server.example.com:80 HTTP/1.1
1278Host: server.example.com:80
1279Proxy-Authorization: basic aGVsbG86d29ybGQ=
1280
1281</artwork></figure>
1282<t>
1283   Bodies on CONNECT requests have no defined semantics. Note that sending a body
1284   on a CONNECT request might cause some existing implementations to reject the
1285   request.
1286</t>
1287<t>
1288   Like any other pipelined HTTP/1.1 request, data to be tunnel may be
1289   sent immediately after the blank line. The usual caveats also apply:
1290   data may be discarded if the eventual response is negative, and the
1291   connection may be reset with no response if more than one TCP segment
1292   is outstanding.
1293</t>
1294
1295<section title="Establishing a Tunnel with CONNECT">
1296<t>
1297   Any successful (2xx) response to a CONNECT request indicates that the
1298   proxy has established a connection to the requested host and port,
1299   and has switched to tunneling the current connection to that server
1300   connection.
1301</t>
1302<t>
1303   It may be the case that the proxy itself can only reach the requested
1304   origin server through another proxy.  In this case, the first proxy
1305   &SHOULD; make a CONNECT request of that next proxy, requesting a tunnel
1306   to the authority.  A proxy &MUST-NOT; respond with any 2xx status code
1307   unless it has either a direct or tunnel connection established to the
1308   authority.
1309</t>
1310<t>
1311   An origin server which receives a CONNECT request for itself &MAY;
1312   respond with a 2xx status code to indicate that a connection is
1313   established.
1314</t>
1315<t>
1316   If at any point either one of the peers gets disconnected, any
1317   outstanding data that came from that peer will be passed to the other
1318   one, and after that also the other connection will be terminated by
1319   the proxy. If there is outstanding data to that peer undelivered,
1320   that data will be discarded.
1321</t>
1322
1323</section>
1324</section>
1325</section>
1326
1327
1328<section title="Status Code Definitions" anchor="status.codes">
1329<t>
1330   Each Status-Code is described below, including any metadata required
1331   in the response.
1332</t>
1333
1334<section title="Informational 1xx" anchor="status.1xx">
1335<t>
1336   This class of status code indicates a provisional response,
1337   consisting only of the Status-Line and optional header fields, and is
1338   terminated by an empty line. There are no required header fields for this
1339   class of status code. Since HTTP/1.0 did not define any 1xx status
1340   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1341   except under experimental conditions.
1342</t>
1343<t>
1344   A client &MUST; be prepared to accept one or more 1xx status responses
1345   prior to a regular response, even if the client does not expect a 100
1346   (Continue) status message. Unexpected 1xx status responses &MAY; be
1347   ignored by a user agent.
1348</t>
1349<t>
1350   Proxies &MUST; forward 1xx responses, unless the connection between the
1351   proxy and its client has been closed, or unless the proxy itself
1352   requested the generation of the 1xx response. (For example, if a
1353   proxy adds a "Expect: 100-continue" field when it forwards a request,
1354   then it need not forward the corresponding 100 (Continue)
1355   response(s).)
1356</t>
1357
1358<section title="100 Continue" anchor="status.100">
1359  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1360  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1361<t>
1362   The client &SHOULD; continue with its request. This interim response is
1363   used to inform the client that the initial part of the request has
1364   been received and has not yet been rejected by the server. The client
1365   &SHOULD; continue by sending the remainder of the request or, if the
1366   request has already been completed, ignore this response. The server
1367   &MUST; send a final response after the request has been completed. See
1368   &use100; for detailed discussion of the use and handling of this
1369   status code.
1370</t>
1371</section>
1372
1373<section title="101 Switching Protocols" anchor="status.101">
1374  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1375  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1376<t>
1377   The server understands and is willing to comply with the client's
1378   request, via the Upgrade message header field (&header-upgrade;), for a
1379   change in the application protocol being used on this connection. The
1380   server will switch protocols to those defined by the response's
1381   Upgrade header field immediately after the empty line which
1382   terminates the 101 response.
1383</t>
1384<t>
1385   The protocol &SHOULD; be switched only when it is advantageous to do
1386   so. For example, switching to a newer version of HTTP is advantageous
1387   over older versions, and switching to a real-time, synchronous
1388   protocol might be advantageous when delivering resources that use
1389   such features.
1390</t>
1391</section>
1392</section>
1393
1394<section title="Successful 2xx" anchor="status.2xx">
1395<t>
1396   This class of status code indicates that the client's request was
1397   successfully received, understood, and accepted.
1398</t>
1399
1400<section title="200 OK" anchor="status.200">
1401  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1402  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1403<t>
1404   The request has succeeded. The payload returned with the response
1405   is dependent on the method used in the request, for example:
1406  <list style="hanging">
1407    <t hangText="GET">
1408      a representation of the target resource is sent in the response;
1409    </t>
1410    <t hangText="HEAD">
1411      the same representation as GET, except without the message-body;
1412    </t>
1413    <t hangText="POST">
1414      a representation describing or containing the result of the action;
1415    </t>
1416    <t hangText="TRACE">
1417      a representation containing the request message as received by the
1418      end server.
1419    </t>
1420  </list>
1421</t>
1422<t>
1423   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1424   freshness for 200 responses.
1425</t>
1426</section>
1427
1428<section title="201 Created" anchor="status.201">
1429  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1430  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1431<t>
1432   The request has been fulfilled and has resulted in a new resource being
1433   created. The newly created resource can be referenced by the URI(s)
1434   returned in the payload of the response, with the most specific URI
1435   for the resource given by a Location header field. The response
1436   &SHOULD; include a payload containing a list of resource
1437   characteristics and location(s) from which the user or user agent can
1438   choose the one most appropriate. The payload format is specified by
1439   the media type given in the Content-Type header field. The origin
1440   server &MUST; create the resource before returning the 201 status code.
1441   If the action cannot be carried out immediately, the server &SHOULD;
1442   respond with 202 (Accepted) response instead.
1443</t>
1444<t>
1445   A 201 response &MAY; contain an ETag response header field indicating
1446   the current value of the entity-tag for the representation of the resource
1447   just created (see &header-etag;).
1448</t>
1449</section>
1450
1451<section title="202 Accepted" anchor="status.202">
1452  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1453  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1454<t>
1455   The request has been accepted for processing, but the processing has
1456   not been completed.  The request might or might not eventually be
1457   acted upon, as it might be disallowed when processing actually takes
1458   place. There is no facility for re-sending a status code from an
1459   asynchronous operation such as this.
1460</t>
1461<t>
1462   The 202 response is intentionally non-committal. Its purpose is to
1463   allow a server to accept a request for some other process (perhaps a
1464   batch-oriented process that is only run once per day) without
1465   requiring that the user agent's connection to the server persist
1466   until the process is completed. The representation returned with this
1467   response &SHOULD; include an indication of the request's current status
1468   and either a pointer to a status monitor or some estimate of when the
1469   user can expect the request to be fulfilled.
1470</t>
1471</section>
1472
1473<section title="203 Non-Authoritative Information" anchor="status.203">
1474  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1475  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1476<t>
1477   The representation in the response has been transformed or otherwise
1478   modified by a transforming proxy (&intermediaries;).  Note that the
1479   behaviour of transforming intermediaries is controlled by the no-transform
1480   Cache-Control directive (&header-cache-control;).
1481</t>
1482<t>
1483   This status code is only appropriate when the response status code would
1484   have been 200 (OK) otherwise. When the status code before transformation
1485   would have been different, the 214 Transformation Applied warn-code
1486   (&header-warning;) is appropriate.
1487</t>
1488<t>
1489   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1490   freshness for 203 responses.
1491</t>
1492</section>
1493
1494<section title="204 No Content" anchor="status.204">
1495  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1496  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1497<t>
1498   The 204 (No Content) status code indicates that the server has
1499   successfully fulfilled the request and that there is no additional
1500   content to return in the response payload body.  Metadata in the
1501   response header fields refer to the target resource and its current
1502   representation after the requested action.
1503</t>
1504<t>
1505   For example, if a 204 status code is received in response to a PUT
1506   request and the response contains an ETag header field, then the PUT
1507   was successful and the ETag field-value contains the entity-tag for
1508   the new representation of that target resource.
1509</t>
1510<t>
1511   The 204 response allows a server to indicate that the action has been
1512   successfully applied to the target resource while implying that the
1513   user agent &SHOULD-NOT; traverse away from its current "document view"
1514   (if any).  The server assumes that the user agent will provide some
1515   indication of the success to its user, in accord with its own interface,
1516   and apply any new or updated metadata in the response to the active
1517   representation.
1518</t>
1519<t>
1520   For example, a 204 status code is commonly used with document editing
1521   interfaces corresponding to a "save" action, such that the document
1522   being saved remains available to the user for editing. It is also
1523   frequently used with interfaces that expect automated data transfers
1524   to be prevalent, such as within distributed version control systems.
1525</t>
1526<t>
1527   The 204 response &MUST-NOT; include a message-body, and thus is always
1528   terminated by the first empty line after the header fields.
1529</t>
1530</section>
1531
1532<section title="205 Reset Content" anchor="status.205">
1533  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1534  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1535<t>
1536   The server has fulfilled the request and the user agent &SHOULD; reset
1537   the document view which caused the request to be sent. This response
1538   is primarily intended to allow input for actions to take place via
1539   user input, followed by a clearing of the form in which the input is
1540   given so that the user can easily initiate another input action.
1541</t>
1542<t>   
1543   The message-body included with the response &MUST; be empty. Note that
1544   receivers still need to parse the response according to the algorithm defined
1545   in &message-body;.
1546</t>
1547</section>
1548
1549<section title="206 Partial Content" anchor="status.206">
1550  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1551  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1552  <rdf:Description>
1553    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1554  </rdf:Description>
1555<t>
1556   The server has fulfilled the partial GET request for the resource
1557   and the enclosed payload is a partial representation as defined in &status-206;.
1558</t>
1559<t>
1560   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1561   freshness for 206 responses.
1562</t>
1563</section>
1564</section>
1565
1566<section title="Redirection 3xx" anchor="status.3xx">
1567<t>
1568   This class of status code indicates that further action needs to be
1569   taken by the user agent in order to fulfill the request.  The action
1570   required &MAY; be carried out by the user agent without interaction
1571   with the user if and only if the method used in the second request is
1572   known to be "safe", as defined in <xref target="safe.methods"/>.
1573   A client &SHOULD; detect infinite redirection loops, since such loops
1574   generate network traffic for each redirection.
1575</t>
1576<x:note>
1577  <t>
1578    <x:h>Note:</x:h> An earlier version of this specification recommended a
1579    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1580    Content developers need to be aware that some clients might
1581    implement such a fixed limitation.
1582  </t>
1583</x:note>
1584
1585<section title="300 Multiple Choices" anchor="status.300">
1586  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1587  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1588<t>
1589   The target resource has more than one
1590   representation, each with its own specific location, and agent-driven
1591   negotiation information (&content-negotiation;) is being provided so that
1592   the user (or user agent) can select a preferred representation by
1593   redirecting its request to that location.
1594</t>
1595<t>
1596   Unless it was a HEAD request, the response &SHOULD; include a representation
1597   containing a list of representation metadata and location(s) from
1598   which the user or user agent can choose the one most appropriate. The
1599   data format is specified by the media type given in the Content-Type
1600   header field. Depending upon the format and the capabilities of
1601   the user agent, selection of the most appropriate choice &MAY; be
1602   performed automatically. However, this specification does not define
1603   any standard for such automatic selection.
1604</t>
1605<t>
1606   If the server has a preferred choice of representation, it &SHOULD;
1607   include the specific URI for that representation in the Location
1608   field; user agents &MAY; use the Location field value for automatic
1609   redirection.
1610</t>
1611<t>
1612   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1613   freshness for 300 responses.
1614</t>
1615
1616</section>
1617
1618<section title="301 Moved Permanently" anchor="status.301">
1619  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1620  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1621<t>
1622   The target resource has been assigned a new permanent URI and any
1623   future references to this resource &SHOULD; use one of the returned
1624   URIs.  Clients with link editing capabilities ought to automatically
1625   re-link references to the effective request URI to one or more of the new
1626   references returned by the server, where possible.
1627</t>
1628<t>
1629   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1630   freshness for 301 responses.
1631</t>
1632<t>
1633   The new permanent URI &SHOULD; be given by the Location field in the
1634   response. Unless the request method was HEAD, the representation of the
1635   response &SHOULD; contain a short hypertext note with a hyperlink to
1636   the new URI(s).
1637</t>
1638<t>
1639   If the 301 status code is received in response to a request method
1640   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1641   then the request &MAY; be automatically redirected by the user agent without
1642   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1643   request unless it can be confirmed by the user, since this might
1644   change the conditions under which the request was issued.
1645</t>
1646<x:note>
1647  <t>
1648    <x:h>Note:</x:h> When automatically redirecting a POST request after
1649    receiving a 301 status code, some existing HTTP/1.0 user agents
1650    will erroneously change it into a GET request.
1651  </t>
1652</x:note>
1653</section>
1654
1655<section title="302 Found" anchor="status.302">
1656  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1657  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1658<t>
1659   The target resource resides temporarily under a different URI.
1660   Since the redirection might be altered on occasion, the client &SHOULD;
1661   continue to use the effective request URI for future requests.
1662</t>
1663<t>
1664   The temporary URI &SHOULD; be given by the Location field in the
1665   response. Unless the request method was HEAD, the representation of the
1666   response &SHOULD; contain a short hypertext note with a hyperlink to
1667   the new URI(s).
1668</t>
1669<t>
1670   If the 302 status code is received in response to a request method
1671   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1672   then the request &MAY; be automatically redirected by the user agent without
1673   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1674   request unless it can be confirmed by the user, since this might
1675   change the conditions under which the request was issued.
1676</t>
1677<x:note>
1678  <t>
1679    <x:h>Note:</x:h> HTTP/1.0 (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>)
1680    and the first version of HTTP/1.1 (<xref target="RFC2068" x:fmt="," x:sec ="10.3.3"/>)
1681    specify that the client is not allowed to change the method on the
1682    redirected request.  However, most existing user agent implementations
1683    treat 302 as if it were a 303 response, performing a GET on the Location
1684    field-value regardless of the original request method. Therefore, a
1685    previous version of this specification
1686    (<xref target="RFC2616" x:fmt="," x:sec="10.3.3"/>) has added the
1687    status codes
1688    <xref target="status.303" format="none">303</xref> and
1689    <xref target="status.307" format="none">307</xref> for servers that wish
1690    to make unambiguously clear which kind of reaction is expected of the
1691    client.
1692  </t>
1693</x:note>
1694</section>
1695
1696<section title="303 See Other" anchor="status.303">
1697  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1698  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1699<t>
1700   The server directs the user agent to a different resource, indicated
1701   by a URI in the Location header field, that provides an indirect
1702   response to the original request.  The user agent &MAY; perform a GET
1703   request on the URI in the Location field in order to obtain a
1704   representation corresponding to the response, be redirected again,
1705   or end with an error status.  The Location URI is not a substitute
1706   reference for the effective request URI.
1707</t>
1708<t>
1709   The 303 status code is generally applicable to any HTTP method.  It is
1710   primarily used to allow the output of a POST action to redirect
1711   the user agent to a selected resource, since doing so provides the
1712   information corresponding to the POST response in a form that
1713   can be separately identified, bookmarked, and cached independent
1714   of the original request.
1715</t>
1716<t>
1717   A 303 response to a GET request indicates that the requested
1718   resource does not have a representation of its own that can be
1719   transferred by the server over HTTP.  The Location URI indicates a
1720   resource that is descriptive of the target resource, such that the
1721   follow-on representation might be useful to recipients without
1722   implying that it adequately represents the target resource.
1723   Note that answers to the questions of what can be represented, what
1724   representations are adequate, and what might be a useful description
1725   are outside the scope of HTTP and thus entirely determined by the
1726   URI owner(s).
1727</t>
1728<t>
1729   Except for responses to a HEAD request, the representation of a 303
1730   response &SHOULD; contain a short hypertext note with a hyperlink
1731   to the Location URI.
1732</t>
1733</section>
1734
1735<section title="304 Not Modified" anchor="status.304">
1736  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1737  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1738  <rdf:Description>
1739    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1740  </rdf:Description>
1741<t>
1742   The response to the request has not been modified since the conditions
1743   indicated by the client's conditional GET request, as defined in &status-304;.
1744</t>
1745</section>
1746
1747<section title="305 Use Proxy" anchor="status.305">
1748  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1749  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1750<t>
1751   The 305 status code was defined in a previous version of this specification
1752   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1753</t>
1754</section>
1755
1756<section title="306 (Unused)" anchor="status.306">
1757  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1758  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1759<t>
1760   The 306 status code was used in a previous version of the
1761   specification, is no longer used, and the code is reserved.
1762</t>
1763</section>
1764
1765<section title="307 Temporary Redirect" anchor="status.307">
1766  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1767  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1768<t>
1769   The target resource resides temporarily under a different URI.
1770   Since the redirection can change over time, the client &SHOULD;
1771   continue to use the effective request URI for future requests.
1772</t>
1773<t>
1774   The temporary URI &SHOULD; be given by the Location field in the
1775   response. Unless the request method was HEAD, the representation of the
1776   response &SHOULD; contain a short hypertext note with a hyperlink to
1777   the new URI(s), since many pre-HTTP/1.1 user agents do not
1778   understand the 307 status code. Therefore, the note &SHOULD; contain the
1779   information necessary for a user to repeat the original request on
1780   the new URI.
1781</t>
1782<t>
1783   If the 307 status code is received in response to a request method
1784   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1785   then the request &MAY; be automatically redirected by the user agent without
1786   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1787   request unless it can be confirmed by the user, since this might
1788   change the conditions under which the request was issued.
1789</t>
1790</section>
1791</section>
1792
1793<section title="Client Error 4xx" anchor="status.4xx">
1794<t>
1795   The 4xx class of status code is intended for cases in which the
1796   client seems to have erred. Except when responding to a HEAD request,
1797   the server &SHOULD; include a representation containing an explanation of the
1798   error situation, and whether it is a temporary or permanent
1799   condition. These status codes are applicable to any request method.
1800   User agents &SHOULD; display any included representation to the user.
1801</t>
1802<t>
1803   If the client is sending data, a server implementation using TCP
1804   &SHOULD; be careful to ensure that the client acknowledges receipt of
1805   the packet(s) containing the response, before the server closes the
1806   input connection. If the client continues sending data to the server
1807   after the close, the server's TCP stack will send a reset packet to
1808   the client, which might erase the client's unacknowledged input buffers
1809   before they can be read and interpreted by the HTTP application.
1810</t>
1811
1812<section title="400 Bad Request" anchor="status.400">
1813  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1814  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1815<t>
1816   The server cannot or will not process the request, due to a client error (e.g.,
1817   malformed syntax).</t>
1818</section>
1819
1820<section title="401 Unauthorized" anchor="status.401">
1821  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1822  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1823  <rdf:Description>
1824    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1825  </rdf:Description>
1826<t>
1827   The request requires user authentication (see &status-401;).
1828</t>
1829</section>
1830
1831<section title="402 Payment Required" anchor="status.402">
1832  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1833  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1834<t>
1835   This code is reserved for future use.
1836</t>
1837</section>
1838
1839<section title="403 Forbidden" anchor="status.403">
1840  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1841  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1842<t>
1843   The server understood the request, but refuses to authorize it. Providing
1844   different user authentication credentials might be successful, but any
1845   credentials that were provided in the request are insufficient. The request
1846   &SHOULD-NOT; be repeated with the same credentials.
1847</t>
1848<t>
1849   If the request method was not HEAD and the server wishes to make
1850   public why the request has not been fulfilled, it &SHOULD; describe the
1851   reason for the refusal in the representation.  If the server does not wish to
1852   make this information available to the client, the status code 404
1853   (Not Found) &MAY; be used instead.
1854</t>
1855</section>
1856
1857<section title="404 Not Found" anchor="status.404">
1858  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1859  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1860<t>
1861   The server has not found anything matching the effective request URI. No
1862   indication is given of whether the condition is temporary or
1863   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1864   knows, through some internally configurable mechanism, that an old
1865   resource is permanently unavailable and has no forwarding address.
1866   This status code is commonly used when the server does not wish to
1867   reveal exactly why the request has been refused, or when no other
1868   response is applicable.
1869</t>
1870</section>
1871
1872<section title="405 Method Not Allowed" anchor="status.405">
1873  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1874  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1875<t>
1876   The method specified in the Request-Line is not allowed for the target
1877   resource. The response &MUST; include an Allow header field containing a
1878   list of valid methods for the requested resource.
1879</t>
1880</section>
1881
1882<section title="406 Not Acceptable" anchor="status.406">
1883  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1884  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1885<t>
1886   The resource identified by the request is only capable of generating
1887   response representations which have content characteristics not acceptable
1888   according to the Accept and Accept-* header fields sent in the request
1889   (see &p3-header-fields;).
1890</t>
1891<t>
1892   Unless it was a HEAD request, the response &SHOULD; include a representation
1893   containing a list of available representation characteristics and location(s)
1894   from which the user or user agent can choose the one most
1895   appropriate. The data format is specified by the media type given
1896   in the Content-Type header field. Depending upon the format and the
1897   capabilities of the user agent, selection of the most appropriate
1898   choice &MAY; be performed automatically. However, this specification
1899   does not define any standard for such automatic selection.
1900</t>
1901<x:note>
1902  <t>
1903    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1904    not acceptable according to the accept header fields sent in the
1905    request. In some cases, this might even be preferable to sending a
1906    406 response. User agents are encouraged to inspect the header fields of
1907    an incoming response to determine if it is acceptable.
1908  </t>
1909</x:note>
1910<t>
1911   If the response could be unacceptable, a user agent &SHOULD;
1912   temporarily stop receipt of more data and query the user for a
1913   decision on further actions.
1914</t>
1915</section>
1916
1917<section title="407 Proxy Authentication Required" anchor="status.407">
1918  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1919  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1920<t>
1921   This code is similar to 401 (Unauthorized), but indicates that the
1922   client must first authenticate itself with the proxy (see &status-407;).
1923</t>
1924</section>
1925
1926<section title="408 Request Timeout" anchor="status.408">
1927  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1928  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1929<t>
1930   The client did not produce a request within the time that the server
1931   was prepared to wait. The client &MAY; repeat the request without
1932   modifications at any later time.
1933</t>
1934</section>
1935
1936<section title="409 Conflict" anchor="status.409">
1937  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1938  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1939<t>
1940   The request could not be completed due to a conflict with the current
1941   state of the resource. This code is only allowed in situations where
1942   it is expected that the user might be able to resolve the conflict
1943   and resubmit the request. The response body &SHOULD; include enough
1944   information for the user to recognize the source of the conflict.
1945   Ideally, the response representation would include enough information for the
1946   user or user agent to fix the problem; however, that might not be
1947   possible and is not required.
1948</t>
1949<t>
1950   Conflicts are most likely to occur in response to a PUT request. For
1951   example, if versioning were being used and the representation being PUT
1952   included changes to a resource which conflict with those made by an
1953   earlier (third-party) request, the server might use the 409 response
1954   to indicate that it can't complete the request. In this case, the
1955   response representation would likely contain a list of the differences
1956   between the two versions in a format defined by the response
1957   Content-Type.
1958</t>
1959</section>
1960
1961<section title="410 Gone" anchor="status.410">
1962  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1963  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1964<t>
1965   The target resource is no longer available at the server and no
1966   forwarding address is known. This condition is expected to be
1967   considered permanent. Clients with link editing capabilities &SHOULD;
1968   delete references to the effective request URI after user approval. If the
1969   server does not know, or has no facility to determine, whether or not
1970   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1971   used instead.
1972</t>
1973<t>
1974   The 410 response is primarily intended to assist the task of web
1975   maintenance by notifying the recipient that the resource is
1976   intentionally unavailable and that the server owners desire that
1977   remote links to that resource be removed. Such an event is common for
1978   limited-time, promotional services and for resources belonging to
1979   individuals no longer working at the server's site. It is not
1980   necessary to mark all permanently unavailable resources as "gone" or
1981   to keep the mark for any length of time &mdash; that is left to the
1982   discretion of the server owner.
1983</t>
1984<t>
1985   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine freshness
1986   for 410 responses.
1987</t>
1988
1989</section>
1990
1991<section title="411 Length Required" anchor="status.411">
1992  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1993  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1994<t>
1995   The server refuses to accept the request without a defined Content-Length.
1996   The client &MAY; repeat the request if it adds a valid
1997   Content-Length header field containing the length of the message-body
1998   in the request message.
1999</t>
2000</section>
2001
2002<section title="412 Precondition Failed" anchor="status.412">
2003  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
2004  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
2005  <rdf:Description>
2006    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
2007  </rdf:Description>
2008<t>
2009   The precondition given in one or more of the header fields
2010   evaluated to false when it was tested on the server, as defined in
2011   &status-412;.
2012</t>
2013</section>
2014
2015<section title="413 Request Representation Too Large" anchor="status.413">
2016  <iref primary="true" item="413 Request Representation Too Large (status code)" x:for-anchor=""/>
2017  <iref primary="true" item="Status Codes" subitem="413 Request Representation Too Large" x:for-anchor=""/>
2018<t>
2019   The server is refusing to process a request because the request
2020   representation is larger than the server is willing or able to process. The
2021   server &MAY; close the connection to prevent the client from continuing
2022   the request.
2023</t>
2024<t>
2025   If the condition is temporary, the server &SHOULD; include a Retry-After
2026   header field to indicate that it is temporary and after what
2027   time the client &MAY; try again.
2028</t>
2029</section>
2030
2031<section title="414 URI Too Long" anchor="status.414">
2032  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
2033  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
2034<t>
2035   The server is refusing to service the request because the effective request URI
2036   is longer than the server is willing to interpret. This rare
2037   condition is only likely to occur when a client has improperly
2038   converted a POST request to a GET request with long query
2039   information, when the client has descended into a URI "black hole" of
2040   redirection (e.g., a redirected URI prefix that points to a suffix of
2041   itself), or when the server is under attack by a client attempting to
2042   exploit security holes present in some servers using fixed-length
2043   buffers for reading or manipulating the effective request URI.
2044</t>
2045</section>
2046
2047<section title="415 Unsupported Media Type" anchor="status.415">
2048  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
2049  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
2050<t>
2051   The server is refusing to service the request because the request
2052   payload is in a format not supported by this request method on the
2053   target resource.
2054</t>
2055</section>
2056
2057<section title="416 Requested Range Not Satisfiable" anchor="status.416">
2058  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
2059  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
2060  <rdf:Description>
2061    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
2062  </rdf:Description>
2063<t>
2064   The request included a Range header field (&header-range;) and none of
2065   the range-specifier values in this field overlap the current extent
2066   of the selected resource. See &status-416;.
2067</t>
2068</section>
2069
2070<section title="417 Expectation Failed" anchor="status.417">
2071  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
2072  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
2073<t>
2074   The expectation given in an Expect header field (see <xref target="header.expect"/>)
2075   could not be met by this server, or, if the server is a proxy,
2076   the server has unambiguous evidence that the request could not be met
2077   by the next-hop server.
2078</t>
2079</section>
2080
2081<section title="426 Upgrade Required" anchor="status.426">
2082  <iref primary="true" item="426 Upgrade Required (status code)" x:for-anchor=""/>
2083  <iref primary="true" item="Status Codes" subitem="426 Upgrade Required" x:for-anchor=""/>
2084<t>
2085   The request can not be completed without a prior protocol upgrade. This
2086   response &MUST; include an Upgrade header field (&header-upgrade;)
2087   specifying the required protocols.
2088</t>
2089<figure>
2090<preamble>Example:</preamble>
2091<artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
2092HTTP/1.1 426 Upgrade Required
2093Upgrade: HTTP/2.0
2094Connection: Upgrade
2095
2096</artwork></figure>
2097<t>
2098   The server &SHOULD; include a message body in the 426 response which
2099   indicates in human readable form the reason for the error and describes any
2100   alternative courses which may be available to the user.
2101</t>
2102</section>
2103</section>
2104
2105<section title="Server Error 5xx" anchor="status.5xx">
2106<t>
2107   Response status codes beginning with the digit "5" indicate cases in
2108   which the server is aware that it has erred or is incapable of
2109   performing the request. Except when responding to a HEAD request, the
2110   server &SHOULD; include a representation containing an explanation of the
2111   error situation, and whether it is a temporary or permanent
2112   condition. User agents &SHOULD; display any included representation to the
2113   user. These response codes are applicable to any request method.
2114</t>
2115
2116<section title="500 Internal Server Error" anchor="status.500">
2117  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
2118  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
2119<t>
2120   The server encountered an unexpected condition which prevented it
2121   from fulfilling the request.
2122</t>
2123</section>
2124
2125<section title="501 Not Implemented" anchor="status.501">
2126  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
2127  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
2128<t>
2129   The server does not support the functionality required to fulfill the
2130   request. This is the appropriate response when the server does not
2131   recognize the request method and is not capable of supporting it for
2132   any resource.
2133</t>
2134</section>
2135
2136<section title="502 Bad Gateway" anchor="status.502">
2137  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
2138  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
2139<t>
2140   The server, while acting as a gateway or proxy, received an invalid
2141   response from the upstream server it accessed in attempting to
2142   fulfill the request.
2143</t>
2144</section>
2145
2146<section title="503 Service Unavailable" anchor="status.503">
2147  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
2148  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
2149<t>
2150   The server is currently unable or unwilling to handle the request due to
2151   reasons such as temporary overloading, maintenance of the server, or rate
2152   limiting of the client.
2153</t>
2154<t>
2155   The implication is that this is a temporary condition which will be
2156   alleviated after some delay. If known, the length of the delay &MAY; be
2157   indicated in a Retry-After header field (<xref target="header.retry-after"/>).
2158   If no Retry-After is given, the client &SHOULD; handle the response as it
2159   would for a 500 response.
2160</t>
2161<x:note>
2162  <t>
2163    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
2164    server must use it when becoming overloaded. Some servers might wish
2165    to simply refuse the connection.
2166  </t>
2167</x:note>
2168</section>
2169
2170<section title="504 Gateway Timeout" anchor="status.504">
2171  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
2172  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
2173<t>
2174   The server, while acting as a gateway or proxy, did not receive a
2175   timely response from the upstream server specified by the URI (e.g.,
2176   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
2177   to access in attempting to complete the request.
2178</t>
2179<x:note>
2180  <t>
2181    <x:h>Note</x:h> to implementors: some deployed proxies are known to
2182    return 400 or 500 when DNS lookups time out.
2183  </t>
2184</x:note>
2185</section>
2186
2187<section title="505 HTTP Version Not Supported" anchor="status.505">
2188  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
2189  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
2190<t>
2191   The server does not support, or refuses to support, the protocol
2192   version that was used in the request message. The server is
2193   indicating that it is unable or unwilling to complete the request
2194   using the same major version as the client, as described in &http-version;,
2195   other than with this error message. The response &SHOULD; contain
2196   a representation describing why that version is not supported and what other
2197   protocols are supported by that server.
2198</t>
2199
2200</section>
2201</section>
2202</section>
2203
2204
2205<section title="Header Field Definitions" anchor="header.field.definitions">
2206<t>
2207   This section defines the syntax and semantics of HTTP/1.1 header fields
2208   related to request and response semantics.
2209</t>
2210
2211<section title="Allow" anchor="header.allow">
2212  <iref primary="true" item="Allow header field" x:for-anchor=""/>
2213  <iref primary="true" item="Header Fields" subitem="Allow" x:for-anchor=""/>
2214  <x:anchor-alias value="Allow"/>
2215<t>
2216   The "Allow" header field lists the set of methods advertised as
2217   supported by the target resource. The purpose of this field is strictly to
2218   inform the recipient of valid request methods associated with the resource.
2219</t>
2220<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/>
2221  <x:ref>Allow</x:ref> = #<x:ref>Method</x:ref>
2222</artwork></figure>
2223<t>
2224   Example of use:
2225</t>
2226<figure><artwork type="example">
2227  Allow: GET, HEAD, PUT
2228</artwork></figure>
2229<t>
2230   The actual set of allowed methods is defined by the origin server at the
2231   time of each request.
2232</t>
2233<t>
2234   A proxy &MUST-NOT; modify the Allow header field &mdash; it does not need to
2235   understand all the methods specified in order to handle them according to
2236   the generic message handling rules.
2237</t>
2238</section>
2239
2240<section title="Expect" anchor="header.expect">
2241  <iref primary="true" item="Expect header field" x:for-anchor=""/>
2242  <iref primary="true" item="Header Fields" subitem="Expect" x:for-anchor=""/>
2243  <x:anchor-alias value="Expect"/>
2244  <x:anchor-alias value="expectation"/>
2245  <x:anchor-alias value="expectation-extension"/>
2246  <x:anchor-alias value="expect-params"/>
2247<t>
2248   The "Expect" header field is used to indicate that particular
2249   server behaviors are required by the client.
2250</t>
2251<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"/>
2252  <x:ref>Expect</x:ref>       = 1#<x:ref>expectation</x:ref>
2253 
2254  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
2255  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
2256                           *<x:ref>expect-params</x:ref> ]
2257  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
2258</artwork></figure>
2259<t>
2260   A server that does not understand or is unable to comply with any of
2261   the expectation values in the Expect field of a request &MUST; respond
2262   with appropriate error status code. The server &MUST; respond with a 417
2263   (Expectation Failed) status code if any of the expectations cannot be met
2264   or, if there are other problems with the request, some other 4xx
2265   status code.
2266</t>
2267<t>
2268   This header field is defined with extensible syntax to allow for
2269   future extensions. If a server receives a request containing an
2270   Expect field that includes an expectation-extension that it does not
2271   support, it &MUST; respond with a 417 (Expectation Failed) status code.
2272</t>
2273<t>
2274   Comparison of expectation values is case-insensitive for unquoted
2275   tokens (including the 100-continue token), and is case-sensitive for
2276   quoted-string expectation-extensions.
2277</t>
2278<t>
2279   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
2280   return a 417 (Expectation Failed) status code if it receives a request
2281   with an expectation that it cannot meet. However, the Expect
2282   header field itself is end-to-end; it &MUST; be forwarded if the
2283   request is forwarded.
2284</t>
2285<t>
2286   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
2287   Expect header field.
2288</t>
2289<t>
2290   See &use100; for the use of the 100 (Continue) status code.
2291</t>
2292</section>
2293
2294<section title="From" anchor="header.from">
2295  <iref primary="true" item="From header field" x:for-anchor=""/>
2296  <iref primary="true" item="Header Fields" subitem="From" x:for-anchor=""/>
2297  <x:anchor-alias value="From"/>
2298  <x:anchor-alias value="mailbox"/>
2299<t>
2300   The "From" header field, if given, &SHOULD; contain an Internet
2301   e-mail address for the human user who controls the requesting user
2302   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
2303   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
2304</t>
2305<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/>
2306  <x:ref>From</x:ref>    = <x:ref>mailbox</x:ref>
2307 
2308  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2309</artwork></figure>
2310<t>
2311   An example is:
2312</t>
2313<figure><artwork type="example">
2314  From: webmaster@example.org
2315</artwork></figure>
2316<t>
2317   This header field &MAY; be used for logging purposes and as a means for
2318   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2319   be used as an insecure form of access protection. The interpretation
2320   of this field is that the request is being performed on behalf of the
2321   person given, who accepts responsibility for the method performed. In
2322   particular, robot agents &SHOULD; include this header field so that the
2323   person responsible for running the robot can be contacted if problems
2324   occur on the receiving end.
2325</t>
2326<t>
2327   The Internet e-mail address in this field &MAY; be separate from the
2328   Internet host which issued the request. For example, when a request
2329   is passed through a proxy the original issuer's address &SHOULD; be
2330   used.
2331</t>
2332<t>
2333   The client &SHOULD-NOT;  send the From header field without the user's
2334   approval, as it might conflict with the user's privacy interests or
2335   their site's security policy. It is strongly recommended that the
2336   user be able to disable, enable, and modify the value of this field
2337   at any time prior to a request.
2338</t>
2339</section>
2340
2341<section title="Location" anchor="header.location">
2342  <iref primary="true" item="Location header field" x:for-anchor=""/>
2343  <iref primary="true" item="Header Fields" subitem="Location" x:for-anchor=""/>
2344  <x:anchor-alias value="Location"/>
2345<t>
2346   The "Location" header field is used to identify a newly created
2347   resource, or to redirect the recipient to a different location for
2348   completion of the request.
2349</t>
2350<t>
2351   For 201 (Created) responses, the Location is the URI of the new resource
2352   which was created by the request. For 3xx responses, the location &SHOULD;
2353   indicate the server's preferred URI for automatic redirection to the
2354   resource.
2355</t>
2356<t>
2357   The field value consists of a single URI-reference. When it has the form
2358   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2359   the final value is computed by resolving it against the effective request
2360   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
2361</t>
2362<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/>
2363  <x:ref>Location</x:ref> = <x:ref>URI-reference</x:ref>
2364</artwork></figure>
2365<figure>
2366<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical WSP below, it's necessary this way for xml2rfc-->
2367<artwork type="example">
2368  Location: http://www.example.org/pub/WWW/People.html#tim
2369</artwork></figure><figure><artwork type="example">  Location: /index.html
2370</artwork></figure>
2371<t>
2372   There are circumstances in which a fragment identifier in a Location URI
2373   would not be appropriate. For instance, when it appears in a 201 Created
2374   response, where the Location header field specifies the URI for the entire
2375   created resource.
2376</t>
2377<x:note>
2378  <t>
2379    <x:h>Note:</x:h> This specification does not define precedence rules
2380    for the case where the original URI, as navigated to by the user
2381    agent, and the Location header field value both contain fragment
2382    identifiers. Thus be aware that including fragment identifiers might
2383    inconvenience anyone relying on the semantics of the original URI's
2384    fragment identifier.
2385  </t>
2386</x:note>
2387<x:note>
2388  <t>
2389    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2390    from Location in that the Content-Location identifies the most specific
2391    resource corresponding to the enclosed representation.
2392    It is therefore possible for a response to contain header fields for
2393    both Location and Content-Location.
2394  </t>
2395</x:note>
2396</section>
2397
2398<section title="Max-Forwards" anchor="header.max-forwards">
2399  <iref primary="true" item="Max-Forwards header field" x:for-anchor=""/>
2400  <iref primary="true" item="Header Fields" subitem="Max-Forwards" x:for-anchor=""/>
2401  <x:anchor-alias value="Max-Forwards"/>
2402<t>
2403   The "Max-Forwards" header field provides a mechanism with the
2404   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2405   methods to limit the number of times that the request is forwarded by
2406   proxies. This can be useful when the client is attempting to
2407   trace a request which appears to be failing or looping in mid-chain.
2408</t>
2409<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/>
2410  <x:ref>Max-Forwards</x:ref> = 1*<x:ref>DIGIT</x:ref>
2411</artwork></figure>
2412<t>
2413   The Max-Forwards value is a decimal integer indicating the remaining
2414   number of times this request message can be forwarded.
2415</t>
2416<t>
2417   Each recipient of a TRACE or OPTIONS request
2418   containing a Max-Forwards header field &MUST; check and update its
2419   value prior to forwarding the request. If the received value is zero
2420   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2421   respond as the final recipient. If the received Max-Forwards value is
2422   greater than zero, then the forwarded message &MUST; contain an updated
2423   Max-Forwards field with a value decremented by one (1).
2424</t>
2425<t>
2426   The Max-Forwards header field &MAY; be ignored for all other request
2427   methods.
2428</t>
2429</section>
2430
2431<section title="Referer" anchor="header.referer">
2432  <iref primary="true" item="Referer header field" x:for-anchor=""/>
2433  <iref primary="true" item="Header Fields" subitem="Referer" x:for-anchor=""/>
2434  <x:anchor-alias value="Referer"/>
2435<t>
2436   The "Referer" [sic] header field allows the client to specify the
2437   URI of the resource from which the effective request URI was obtained (the
2438   "referrer", although the header field is misspelled.).
2439</t>
2440<t>
2441   The Referer header field allows servers to generate lists of back-links to
2442   resources for interest, logging, optimized caching, etc. It also allows
2443   obsolete or mistyped links to be traced for maintenance. Some servers use
2444   Referer as a means of controlling where they allow links from (so-called
2445   "deep linking"), but legitimate requests do not always
2446   contain a Referer header field.
2447</t>
2448<t>
2449   If the effective request URI was obtained from a source that does not have its own
2450   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
2451   sent with the value "about:blank", or not be sent at all. Note that this
2452   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2453</t>
2454<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/>
2455  <x:ref>Referer</x:ref> = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2456</artwork></figure>
2457<t>
2458   Example:
2459</t>
2460<figure><artwork type="example">
2461  Referer: http://www.example.org/hypertext/Overview.html
2462</artwork></figure>
2463<t>
2464   If the field value is a relative URI, it &SHOULD; be interpreted
2465   relative to the effective request URI. The URI &MUST-NOT; include a fragment. See
2466   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2467</t>
2468</section>
2469
2470<section title="Retry-After" anchor="header.retry-after">
2471  <iref primary="true" item="Retry-After header field" x:for-anchor=""/>
2472  <iref primary="true" item="Header Fields" subitem="Retry-After" x:for-anchor=""/>
2473  <x:anchor-alias value="Retry-After"/>
2474<t>
2475   The header "Retry-After" field can be used with a 503 (Service
2476   Unavailable) response to indicate how long the service is expected to
2477   be unavailable to the requesting client. This field &MAY; also be used
2478   with any 3xx (Redirection) response to indicate the minimum time the
2479   user-agent is asked wait before issuing the redirected request.
2480</t>
2481<t>
2482   The value of this field can be either an HTTP-date or an integer number
2483   of seconds (in decimal) after the time of the response.
2484</t>
2485<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/>
2486  <x:ref>Retry-After</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2487</artwork></figure>
2488<t anchor="rule.delta-seconds">
2489  <x:anchor-alias value="delta-seconds"/>
2490   Time spans are non-negative decimal integers, representing time in
2491   seconds.
2492</t>
2493<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2494  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2495</artwork></figure>
2496<t>
2497   Two examples of its use are
2498</t>
2499<figure><artwork type="example">
2500  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2501  Retry-After: 120
2502</artwork></figure>
2503<t>
2504   In the latter example, the delay is 2 minutes.
2505</t>
2506</section>
2507
2508<section title="Server" anchor="header.server">
2509  <iref primary="true" item="Server header field" x:for-anchor=""/>
2510  <iref primary="true" item="Header Fields" subitem="Server" x:for-anchor=""/>
2511  <x:anchor-alias value="Server"/>
2512<t>
2513   The "Server" header field contains information about the
2514   software used by the origin server to handle the request.
2515</t>
2516<t>
2517   The field can contain multiple product tokens (&product-tokens;) and
2518   comments (&header-fields;) identifying the server and any significant
2519   subproducts. The product tokens are listed in order of their significance
2520   for identifying the application.
2521</t>
2522<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/>
2523  <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> ) )
2524</artwork></figure>
2525<t>
2526   Example:
2527</t>
2528<figure><artwork type="example">
2529  Server: CERN/3.0 libwww/2.17
2530</artwork></figure>
2531<t>
2532   If the response is being forwarded through a proxy, the proxy
2533   application &MUST-NOT; modify the Server header field. Instead, it
2534   &MUST; include a Via field (as described in &header-via;).
2535</t>
2536<x:note>
2537  <t>
2538    <x:h>Note:</x:h> Revealing the specific software version of the server might
2539    allow the server machine to become more vulnerable to attacks
2540    against software that is known to contain security holes. Server
2541    implementors are encouraged to make this field a configurable
2542    option.
2543  </t>
2544</x:note>
2545</section>
2546
2547<section title="User-Agent" anchor="header.user-agent">
2548  <iref primary="true" item="User-Agent header field" x:for-anchor=""/>
2549  <iref primary="true" item="Header Fields" subitem="User-Agent" x:for-anchor=""/>
2550  <x:anchor-alias value="User-Agent"/>
2551<t>
2552   The "User-Agent" header field contains information about the user
2553   agent originating the request. User agents &SHOULD; include this field with
2554   requests.
2555</t>
2556<t>
2557   Typically, it is used for statistical purposes, the tracing of protocol
2558   violations, and tailoring responses to avoid particular user agent
2559   limitations.
2560</t>
2561<t>
2562   The field can contain multiple product tokens (&product-tokens;)
2563   and comments (&header-fields;) identifying the agent and its
2564   significant subproducts. By convention, the product tokens are listed in
2565   order of their significance for identifying the application.
2566</t>
2567<t>
2568   Because this field is usually sent on every request a user agent makes,
2569   implementations are encouraged not to include needlessly fine-grained
2570   detail, and to limit (or even prohibit) the addition of subproducts by third
2571   parties. Overly long and detailed User-Agent field values make requests
2572   larger and can also be used to identify ("fingerprint") the user against
2573   their wishes.
2574</t>
2575<t>
2576   Likewise, implementations are encouraged not to use the product tokens of
2577   other implementations in order to declare compatibility with them, as this
2578   circumvents the purpose of the field. Finally, they are encouraged not to
2579   use comments to identify products; doing so makes the field value more
2580   difficult to parse.
2581</t>
2582<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/>
2583  <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> ) )
2584</artwork></figure>
2585<t>
2586   Example:
2587</t>
2588<figure><artwork type="example">
2589  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2590</artwork></figure>
2591</section>
2592
2593</section>
2594
2595<section title="IANA Considerations" anchor="IANA.considerations">
2596
2597<section title="Method Registry" anchor="method.registration">
2598<t>
2599  The registration procedure for HTTP request methods is defined by
2600  <xref target="method.registry"/> of this document.
2601</t>
2602<t>
2603   The HTTP Method Registry shall be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2604   and be populated with the registrations below:
2605</t>
2606<?BEGININC p2-semantics.iana-methods ?>
2607<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2608<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2609   <ttcol>Method</ttcol>
2610   <ttcol>Safe</ttcol>
2611   <ttcol>Reference</ttcol>
2612   <c>CONNECT</c>
2613   <c>no</c>
2614   <c>
2615      <xref target="CONNECT"/>
2616   </c>
2617   <c>DELETE</c>
2618   <c>no</c>
2619   <c>
2620      <xref target="DELETE"/>
2621   </c>
2622   <c>GET</c>
2623   <c>yes</c>
2624   <c>
2625      <xref target="GET"/>
2626   </c>
2627   <c>HEAD</c>
2628   <c>yes</c>
2629   <c>
2630      <xref target="HEAD"/>
2631   </c>
2632   <c>OPTIONS</c>
2633   <c>yes</c>
2634   <c>
2635      <xref target="OPTIONS"/>
2636   </c>
2637   <c>POST</c>
2638   <c>no</c>
2639   <c>
2640      <xref target="POST"/>
2641   </c>
2642   <c>PUT</c>
2643   <c>no</c>
2644   <c>
2645      <xref target="PUT"/>
2646   </c>
2647   <c>TRACE</c>
2648   <c>yes</c>
2649   <c>
2650      <xref target="TRACE"/>
2651   </c>
2652</texttable>
2653<!--(END)-->
2654<?ENDINC p2-semantics.iana-methods ?>
2655</section>
2656
2657<section title="Status Code Registry" anchor="status.code.registration">
2658<t>
2659   The registration procedure for HTTP Status Codes &mdash; previously defined
2660   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> &mdash; is now defined
2661   by <xref target="status.code.registry"/> of this document.
2662</t>
2663<t>
2664   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2665   shall be updated with the registrations below:
2666</t>
2667<?BEGININC p2-semantics.iana-status-codes ?>
2668<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2669<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2670   <ttcol>Value</ttcol>
2671   <ttcol>Description</ttcol>
2672   <ttcol>Reference</ttcol>
2673   <c>100</c>
2674   <c>Continue</c>
2675   <c>
2676      <xref target="status.100"/>
2677   </c>
2678   <c>101</c>
2679   <c>Switching Protocols</c>
2680   <c>
2681      <xref target="status.101"/>
2682   </c>
2683   <c>200</c>
2684   <c>OK</c>
2685   <c>
2686      <xref target="status.200"/>
2687   </c>
2688   <c>201</c>
2689   <c>Created</c>
2690   <c>
2691      <xref target="status.201"/>
2692   </c>
2693   <c>202</c>
2694   <c>Accepted</c>
2695   <c>
2696      <xref target="status.202"/>
2697   </c>
2698   <c>203</c>
2699   <c>Non-Authoritative Information</c>
2700   <c>
2701      <xref target="status.203"/>
2702   </c>
2703   <c>204</c>
2704   <c>No Content</c>
2705   <c>
2706      <xref target="status.204"/>
2707   </c>
2708   <c>205</c>
2709   <c>Reset Content</c>
2710   <c>
2711      <xref target="status.205"/>
2712   </c>
2713   <c>300</c>
2714   <c>Multiple Choices</c>
2715   <c>
2716      <xref target="status.300"/>
2717   </c>
2718   <c>301</c>
2719   <c>Moved Permanently</c>
2720   <c>
2721      <xref target="status.301"/>
2722   </c>
2723   <c>302</c>
2724   <c>Found</c>
2725   <c>
2726      <xref target="status.302"/>
2727   </c>
2728   <c>303</c>
2729   <c>See Other</c>
2730   <c>
2731      <xref target="status.303"/>
2732   </c>
2733   <c>305</c>
2734   <c>Use Proxy</c>
2735   <c>
2736      <xref target="status.305"/>
2737   </c>
2738   <c>306</c>
2739   <c>(Unused)</c>
2740   <c>
2741      <xref target="status.306"/>
2742   </c>
2743   <c>307</c>
2744   <c>Temporary Redirect</c>
2745   <c>
2746      <xref target="status.307"/>
2747   </c>
2748   <c>400</c>
2749   <c>Bad Request</c>
2750   <c>
2751      <xref target="status.400"/>
2752   </c>
2753   <c>402</c>
2754   <c>Payment Required</c>
2755   <c>
2756      <xref target="status.402"/>
2757   </c>
2758   <c>403</c>
2759   <c>Forbidden</c>
2760   <c>
2761      <xref target="status.403"/>
2762   </c>
2763   <c>404</c>
2764   <c>Not Found</c>
2765   <c>
2766      <xref target="status.404"/>
2767   </c>
2768   <c>405</c>
2769   <c>Method Not Allowed</c>
2770   <c>
2771      <xref target="status.405"/>
2772   </c>
2773   <c>406</c>
2774   <c>Not Acceptable</c>
2775   <c>
2776      <xref target="status.406"/>
2777   </c>
2778   <c>407</c>
2779   <c>Proxy Authentication Required</c>
2780   <c>
2781      <xref target="status.407"/>
2782   </c>
2783   <c>408</c>
2784   <c>Request Timeout</c>
2785   <c>
2786      <xref target="status.408"/>
2787   </c>
2788   <c>409</c>
2789   <c>Conflict</c>
2790   <c>
2791      <xref target="status.409"/>
2792   </c>
2793   <c>410</c>
2794   <c>Gone</c>
2795   <c>
2796      <xref target="status.410"/>
2797   </c>
2798   <c>411</c>
2799   <c>Length Required</c>
2800   <c>
2801      <xref target="status.411"/>
2802   </c>
2803   <c>413</c>
2804   <c>Request Representation Too Large</c>
2805   <c>
2806      <xref target="status.413"/>
2807   </c>
2808   <c>414</c>
2809   <c>URI Too Long</c>
2810   <c>
2811      <xref target="status.414"/>
2812   </c>
2813   <c>415</c>
2814   <c>Unsupported Media Type</c>
2815   <c>
2816      <xref target="status.415"/>
2817   </c>
2818   <c>417</c>
2819   <c>Expectation Failed</c>
2820   <c>
2821      <xref target="status.417"/>
2822   </c>
2823   <c>426</c>
2824   <c>Upgrade Required</c>
2825   <c>
2826      <xref target="status.426"/>
2827   </c>
2828   <c>500</c>
2829   <c>Internal Server Error</c>
2830   <c>
2831      <xref target="status.500"/>
2832   </c>
2833   <c>501</c>
2834   <c>Not Implemented</c>
2835   <c>
2836      <xref target="status.501"/>
2837   </c>
2838   <c>502</c>
2839   <c>Bad Gateway</c>
2840   <c>
2841      <xref target="status.502"/>
2842   </c>
2843   <c>503</c>
2844   <c>Service Unavailable</c>
2845   <c>
2846      <xref target="status.503"/>
2847   </c>
2848   <c>504</c>
2849   <c>Gateway Timeout</c>
2850   <c>
2851      <xref target="status.504"/>
2852   </c>
2853   <c>505</c>
2854   <c>HTTP Version Not Supported</c>
2855   <c>
2856      <xref target="status.505"/>
2857   </c>
2858</texttable>
2859<!--(END)-->
2860<?ENDINC p2-semantics.iana-status-codes ?>
2861</section>
2862<section title="Header Field Registration" anchor="header.field.registration">
2863<t>
2864   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
2865   with the permanent registrations below (see <xref target="RFC3864"/>):
2866</t>
2867<?BEGININC p2-semantics.iana-headers ?>
2868<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2869<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2870   <ttcol>Header Field Name</ttcol>
2871   <ttcol>Protocol</ttcol>
2872   <ttcol>Status</ttcol>
2873   <ttcol>Reference</ttcol>
2874
2875   <c>Allow</c>
2876   <c>http</c>
2877   <c>standard</c>
2878   <c>
2879      <xref target="header.allow"/>
2880   </c>
2881   <c>Expect</c>
2882   <c>http</c>
2883   <c>standard</c>
2884   <c>
2885      <xref target="header.expect"/>
2886   </c>
2887   <c>From</c>
2888   <c>http</c>
2889   <c>standard</c>
2890   <c>
2891      <xref target="header.from"/>
2892   </c>
2893   <c>Location</c>
2894   <c>http</c>
2895   <c>standard</c>
2896   <c>
2897      <xref target="header.location"/>
2898   </c>
2899   <c>Max-Forwards</c>
2900   <c>http</c>
2901   <c>standard</c>
2902   <c>
2903      <xref target="header.max-forwards"/>
2904   </c>
2905   <c>Referer</c>
2906   <c>http</c>
2907   <c>standard</c>
2908   <c>
2909      <xref target="header.referer"/>
2910   </c>
2911   <c>Retry-After</c>
2912   <c>http</c>
2913   <c>standard</c>
2914   <c>
2915      <xref target="header.retry-after"/>
2916   </c>
2917   <c>Server</c>
2918   <c>http</c>
2919   <c>standard</c>
2920   <c>
2921      <xref target="header.server"/>
2922   </c>
2923   <c>User-Agent</c>
2924   <c>http</c>
2925   <c>standard</c>
2926   <c>
2927      <xref target="header.user-agent"/>
2928   </c>
2929</texttable>
2930<!--(END)-->
2931<?ENDINC p2-semantics.iana-headers ?>
2932<t>
2933   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2934</t>
2935</section>
2936</section>
2937
2938<section title="Security Considerations" anchor="security.considerations">
2939<t>
2940   This section is meant to inform application developers, information
2941   providers, and users of the security limitations in HTTP/1.1 as
2942   described by this document. The discussion does not include
2943   definitive solutions to the problems revealed, though it does make
2944   some suggestions for reducing security risks.
2945</t>
2946
2947<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2948<t>
2949   Like any generic data transfer protocol, HTTP cannot regulate the
2950   content of the data that is transferred, nor is there any a priori
2951   method of determining the sensitivity of any particular piece of
2952   information within the context of any given request. Therefore,
2953   applications &SHOULD; supply as much control over this information as
2954   possible to the provider of that information. Four header fields are
2955   worth special mention in this context: Server, Via, Referer and From.
2956</t>
2957<t>
2958   Revealing the specific software version of the server might allow the
2959   server machine to become more vulnerable to attacks against software
2960   that is known to contain security holes. Implementors &SHOULD; make the
2961   Server header field a configurable option.
2962</t>
2963<t>
2964   Proxies which serve as a portal through a network firewall &SHOULD;
2965   take special precautions regarding the transfer of header information
2966   that identifies the hosts behind the firewall. In particular, they
2967   &SHOULD; remove, or replace with sanitized versions, any Via fields
2968   generated behind the firewall.
2969</t>
2970<t>
2971   The Referer header field allows reading patterns to be studied and reverse
2972   links drawn. Although it can be very useful, its power can be abused
2973   if user details are not separated from the information contained in
2974   the Referer. Even when the personal information has been removed, the
2975   Referer header field might indicate a private document's URI whose
2976   publication would be inappropriate.
2977</t>
2978<t>
2979   The information sent in the From field might conflict with the user's
2980   privacy interests or their site's security policy, and hence it
2981   &SHOULD-NOT;  be transmitted without the user being able to disable,
2982   enable, and modify the contents of the field. The user &MUST; be able
2983   to set the contents of this field within a user preference or
2984   application defaults configuration.
2985</t>
2986<t>
2987   We suggest, though do not require, that a convenient toggle interface
2988   be provided for the user to enable or disable the sending of From and
2989   Referer information.
2990</t>
2991<t>
2992   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref
2993   target="header.server"/>) header fields can sometimes be used to determine
2994   that a specific client or server have a particular security hole which might
2995   be exploited. Unfortunately, this same information is often used for other
2996   valuable purposes for which HTTP currently has no better mechanism.
2997</t>
2998<t>
2999   Furthermore, the User-Agent header field may contain enough entropy to be
3000   used, possibly in conjunction with other material, to uniquely identify the
3001   user.
3002</t>
3003<t>
3004   Some request methods, like TRACE (<xref target="TRACE"/>), expose information
3005   that was sent in request header fields within the body of their response.
3006   Clients &SHOULD; be careful with sensitive information, like Cookies,
3007   Authorization credentials, and other header fields that might be used to
3008   collect data from the client.
3009</t> 
3010</section>
3011
3012<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
3013<t>
3014   Because the source of a link might be private information or might
3015   reveal an otherwise private information source, it is strongly
3016   recommended that the user be able to select whether or not the
3017   Referer field is sent. For example, a browser client could have a
3018   toggle switch for browsing openly/anonymously, which would
3019   respectively enable/disable the sending of Referer and From
3020   information.
3021</t>
3022<t>
3023   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
3024   HTTP request if the referring page was transferred with a secure
3025   protocol.
3026</t>
3027<t>
3028   Authors of services &SHOULD-NOT; use GET-based forms for the submission of
3029   sensitive data because that data will be placed in the request-target. Many
3030   existing servers, proxies, and user agents log or display the request-target
3031   in places where it might be visible to third parties. Such services can
3032   use POST-based form submission instead.
3033</t>
3034</section>
3035
3036<section title="Location Headers and Spoofing" anchor="location.spoofing">
3037<t>
3038   If a single server supports multiple organizations that do not trust
3039   one another, then it &MUST; check the values of Location and Content-Location
3040   header fields in responses that are generated under control of
3041   said organizations to make sure that they do not attempt to
3042   invalidate resources over which they have no authority.
3043</t>
3044</section>
3045
3046<section title="Security Considerations for CONNECT">
3047<t>
3048   Since tunneled data is opaque to the proxy, there are additional
3049   risks to tunneling to other well-known or reserved ports.
3050   A HTTP client CONNECTing to port 25 could relay spam
3051   via SMTP, for example. As such, proxies &SHOULD; restrict CONNECT
3052   access to a small number of known ports.
3053</t>
3054</section>
3055
3056</section>
3057
3058<section title="Acknowledgments" anchor="acks">
3059<t>
3060  See &acks;.
3061</t>
3062</section>
3063</middle>
3064<back>
3065
3066<references title="Normative References">
3067
3068<reference anchor="Part1">
3069  <front>
3070    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
3071    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3072      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3073      <address><email>fielding@gbiv.com</email></address>
3074    </author>
3075    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3076      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3077      <address><email>jg@freedesktop.org</email></address>
3078    </author>
3079    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3080      <organization abbrev="HP">Hewlett-Packard Company</organization>
3081      <address><email>JeffMogul@acm.org</email></address>
3082    </author>
3083    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3084      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3085      <address><email>henrikn@microsoft.com</email></address>
3086    </author>
3087    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3088      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3089      <address><email>LMM@acm.org</email></address>
3090    </author>
3091    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3092      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3093      <address><email>paulle@microsoft.com</email></address>
3094    </author>
3095    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3096      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3097      <address><email>timbl@w3.org</email></address>
3098    </author>
3099    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3100      <organization abbrev="W3C">World Wide Web Consortium</organization>
3101      <address><email>ylafon@w3.org</email></address>
3102    </author>
3103    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3104      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3105      <address><email>julian.reschke@greenbytes.de</email></address>
3106    </author>
3107    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3108  </front>
3109  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
3110  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
3111</reference>
3112
3113<reference anchor="Part3">
3114  <front>
3115    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
3116    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3117      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3118      <address><email>fielding@gbiv.com</email></address>
3119    </author>
3120    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3121      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3122      <address><email>jg@freedesktop.org</email></address>
3123    </author>
3124    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3125      <organization abbrev="HP">Hewlett-Packard Company</organization>
3126      <address><email>JeffMogul@acm.org</email></address>
3127    </author>
3128    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3129      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3130      <address><email>henrikn@microsoft.com</email></address>
3131    </author>
3132    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3133      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3134      <address><email>LMM@acm.org</email></address>
3135    </author>
3136    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3137      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3138      <address><email>paulle@microsoft.com</email></address>
3139    </author>
3140    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3141      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3142      <address><email>timbl@w3.org</email></address>
3143    </author>
3144    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3145      <organization abbrev="W3C">World Wide Web Consortium</organization>
3146      <address><email>ylafon@w3.org</email></address>
3147    </author>
3148    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3149      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3150      <address><email>julian.reschke@greenbytes.de</email></address>
3151    </author>
3152    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3153  </front>
3154  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
3155  <x:source href="p3-payload.xml" basename="p3-payload"/>
3156</reference>
3157
3158<reference anchor="Part4">
3159  <front>
3160    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
3161    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3162      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3163      <address><email>fielding@gbiv.com</email></address>
3164    </author>
3165    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3166      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3167      <address><email>jg@freedesktop.org</email></address>
3168    </author>
3169    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3170      <organization abbrev="HP">Hewlett-Packard Company</organization>
3171      <address><email>JeffMogul@acm.org</email></address>
3172    </author>
3173    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3174      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3175      <address><email>henrikn@microsoft.com</email></address>
3176    </author>
3177    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3178      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3179      <address><email>LMM@acm.org</email></address>
3180    </author>
3181    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3182      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3183      <address><email>paulle@microsoft.com</email></address>
3184    </author>
3185    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3186      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3187      <address><email>timbl@w3.org</email></address>
3188    </author>
3189    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3190      <organization abbrev="W3C">World Wide Web Consortium</organization>
3191      <address><email>ylafon@w3.org</email></address>
3192    </author>
3193    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3194      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3195      <address><email>julian.reschke@greenbytes.de</email></address>
3196    </author>
3197    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3198  </front>
3199  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
3200  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
3201</reference>
3202
3203<reference anchor="Part5">
3204  <front>
3205    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
3206    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3207      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3208      <address><email>fielding@gbiv.com</email></address>
3209    </author>
3210    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3211      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3212      <address><email>jg@freedesktop.org</email></address>
3213    </author>
3214    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3215      <organization abbrev="HP">Hewlett-Packard Company</organization>
3216      <address><email>JeffMogul@acm.org</email></address>
3217    </author>
3218    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3219      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3220      <address><email>henrikn@microsoft.com</email></address>
3221    </author>
3222    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3223      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3224      <address><email>LMM@acm.org</email></address>
3225    </author>
3226    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3227      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3228      <address><email>paulle@microsoft.com</email></address>
3229    </author>
3230    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3231      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3232      <address><email>timbl@w3.org</email></address>
3233    </author>
3234    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3235      <organization abbrev="W3C">World Wide Web Consortium</organization>
3236      <address><email>ylafon@w3.org</email></address>
3237    </author>
3238    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3239      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3240      <address><email>julian.reschke@greenbytes.de</email></address>
3241    </author>
3242    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3243  </front>
3244  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
3245  <x:source href="p5-range.xml" basename="p5-range"/>
3246</reference>
3247
3248<reference anchor="Part6">
3249  <front>
3250    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
3251    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3252      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3253      <address><email>fielding@gbiv.com</email></address>
3254    </author>
3255    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3256      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3257      <address><email>jg@freedesktop.org</email></address>
3258    </author>
3259    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3260      <organization abbrev="HP">Hewlett-Packard Company</organization>
3261      <address><email>JeffMogul@acm.org</email></address>
3262    </author>
3263    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3264      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3265      <address><email>henrikn@microsoft.com</email></address>
3266    </author>
3267    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3268      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3269      <address><email>LMM@acm.org</email></address>
3270    </author>
3271    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3272      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3273      <address><email>paulle@microsoft.com</email></address>
3274    </author>
3275    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3276      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3277      <address><email>timbl@w3.org</email></address>
3278    </author>
3279    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3280      <organization abbrev="W3C">World Wide Web Consortium</organization>
3281      <address><email>ylafon@w3.org</email></address>
3282    </author>
3283    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
3284      <address><email>mnot@mnot.net</email></address>
3285    </author>
3286    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3287      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3288      <address><email>julian.reschke@greenbytes.de</email></address>
3289    </author>
3290    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3291  </front>
3292  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
3293  <x:source href="p6-cache.xml" basename="p6-cache"/>
3294</reference>
3295
3296<reference anchor="Part7">
3297  <front>
3298    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
3299    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3300      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3301      <address><email>fielding@gbiv.com</email></address>
3302    </author>
3303    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3304      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3305      <address><email>jg@freedesktop.org</email></address>
3306    </author>
3307    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3308      <organization abbrev="HP">Hewlett-Packard Company</organization>
3309      <address><email>JeffMogul@acm.org</email></address>
3310    </author>
3311    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3312      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3313      <address><email>henrikn@microsoft.com</email></address>
3314    </author>
3315    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3316      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3317      <address><email>LMM@acm.org</email></address>
3318    </author>
3319    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3320      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3321      <address><email>paulle@microsoft.com</email></address>
3322    </author>
3323    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3324      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3325      <address><email>timbl@w3.org</email></address>
3326    </author>
3327    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3328      <organization abbrev="W3C">World Wide Web Consortium</organization>
3329      <address><email>ylafon@w3.org</email></address>
3330    </author>
3331    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3332      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3333      <address><email>julian.reschke@greenbytes.de</email></address>
3334    </author>
3335    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3336  </front>
3337  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3338  <x:source href="p7-auth.xml" basename="p7-auth"/>
3339</reference>
3340
3341<reference anchor="RFC2119">
3342  <front>
3343    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3344    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3345      <organization>Harvard University</organization>
3346      <address><email>sob@harvard.edu</email></address>
3347    </author>
3348    <date month="March" year="1997"/>
3349  </front>
3350  <seriesInfo name="BCP" value="14"/>
3351  <seriesInfo name="RFC" value="2119"/>
3352</reference>
3353
3354<reference anchor="RFC3986">
3355 <front>
3356  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3357  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3358    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3359    <address>
3360       <email>timbl@w3.org</email>
3361       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3362    </address>
3363  </author>
3364  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3365    <organization abbrev="Day Software">Day Software</organization>
3366    <address>
3367      <email>fielding@gbiv.com</email>
3368      <uri>http://roy.gbiv.com/</uri>
3369    </address>
3370  </author>
3371  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3372    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3373    <address>
3374      <email>LMM@acm.org</email>
3375      <uri>http://larry.masinter.net/</uri>
3376    </address>
3377  </author>
3378  <date month='January' year='2005'></date>
3379 </front>
3380 <seriesInfo name="STD" value="66"/>
3381 <seriesInfo name="RFC" value="3986"/>
3382</reference>
3383
3384<reference anchor="RFC5234">
3385  <front>
3386    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3387    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3388      <organization>Brandenburg InternetWorking</organization>
3389      <address>
3390        <email>dcrocker@bbiw.net</email>
3391      </address> 
3392    </author>
3393    <author initials="P." surname="Overell" fullname="Paul Overell">
3394      <organization>THUS plc.</organization>
3395      <address>
3396        <email>paul.overell@thus.net</email>
3397      </address>
3398    </author>
3399    <date month="January" year="2008"/>
3400  </front>
3401  <seriesInfo name="STD" value="68"/>
3402  <seriesInfo name="RFC" value="5234"/>
3403</reference>
3404
3405</references>
3406
3407<references title="Informative References">
3408
3409<reference anchor="RFC1945">
3410  <front>
3411    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3412    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3413      <organization>MIT, Laboratory for Computer Science</organization>
3414      <address><email>timbl@w3.org</email></address>
3415    </author>
3416    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3417      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3418      <address><email>fielding@ics.uci.edu</email></address>
3419    </author>
3420    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3421      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3422      <address><email>frystyk@w3.org</email></address>
3423    </author>
3424    <date month="May" year="1996"/>
3425  </front>
3426  <seriesInfo name="RFC" value="1945"/>
3427</reference>
3428
3429<reference anchor="RFC2068">
3430  <front>
3431    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3432    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3433      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3434      <address><email>fielding@ics.uci.edu</email></address>
3435    </author>
3436    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3437      <organization>MIT Laboratory for Computer Science</organization>
3438      <address><email>jg@w3.org</email></address>
3439    </author>
3440    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3441      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3442      <address><email>mogul@wrl.dec.com</email></address>
3443    </author>
3444    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3445      <organization>MIT Laboratory for Computer Science</organization>
3446      <address><email>frystyk@w3.org</email></address>
3447    </author>
3448    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3449      <organization>MIT Laboratory for Computer Science</organization>
3450      <address><email>timbl@w3.org</email></address>
3451    </author>
3452    <date month="January" year="1997"/>
3453  </front>
3454  <seriesInfo name="RFC" value="2068"/>
3455</reference>
3456
3457<reference anchor="RFC2616">
3458  <front>
3459    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3460    <author initials="R." surname="Fielding" fullname="R. Fielding">
3461      <organization>University of California, Irvine</organization>
3462      <address><email>fielding@ics.uci.edu</email></address>
3463    </author>
3464    <author initials="J." surname="Gettys" fullname="J. Gettys">
3465      <organization>W3C</organization>
3466      <address><email>jg@w3.org</email></address>
3467    </author>
3468    <author initials="J." surname="Mogul" fullname="J. Mogul">
3469      <organization>Compaq Computer Corporation</organization>
3470      <address><email>mogul@wrl.dec.com</email></address>
3471    </author>
3472    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3473      <organization>MIT Laboratory for Computer Science</organization>
3474      <address><email>frystyk@w3.org</email></address>
3475    </author>
3476    <author initials="L." surname="Masinter" fullname="L. Masinter">
3477      <organization>Xerox Corporation</organization>
3478      <address><email>masinter@parc.xerox.com</email></address>
3479    </author>
3480    <author initials="P." surname="Leach" fullname="P. Leach">
3481      <organization>Microsoft Corporation</organization>
3482      <address><email>paulle@microsoft.com</email></address>
3483    </author>
3484    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3485      <organization>W3C</organization>
3486      <address><email>timbl@w3.org</email></address>
3487    </author>
3488    <date month="June" year="1999"/>
3489  </front>
3490  <seriesInfo name="RFC" value="2616"/>
3491</reference>
3492
3493<reference anchor='RFC2817'>
3494  <front>
3495    <title>Upgrading to TLS Within HTTP/1.1</title>
3496    <author initials='R.' surname='Khare' fullname='R. Khare'>
3497      <organization>4K Associates / UC Irvine</organization>
3498      <address><email>rohit@4K-associates.com</email></address>
3499    </author>
3500    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3501      <organization>Agranat Systems, Inc.</organization>
3502      <address><email>lawrence@agranat.com</email></address>
3503    </author>
3504    <date year='2000' month='May' />
3505  </front>
3506  <seriesInfo name='RFC' value='2817' />
3507</reference>
3508
3509<reference anchor='RFC3864'>
3510  <front>
3511    <title>Registration Procedures for Message Header Fields</title>
3512    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3513      <organization>Nine by Nine</organization>
3514      <address><email>GK-IETF@ninebynine.org</email></address>
3515    </author>
3516    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3517      <organization>BEA Systems</organization>
3518      <address><email>mnot@pobox.com</email></address>
3519    </author>
3520    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3521      <organization>HP Labs</organization>
3522      <address><email>JeffMogul@acm.org</email></address>
3523    </author>
3524    <date year='2004' month='September' />
3525  </front>
3526  <seriesInfo name='BCP' value='90' />
3527  <seriesInfo name='RFC' value='3864' />
3528</reference>
3529
3530<reference anchor='RFC5226'>
3531  <front>
3532    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3533    <author initials='T.' surname='Narten' fullname='T. Narten'>
3534      <organization>IBM</organization>
3535      <address><email>narten@us.ibm.com</email></address>
3536    </author>
3537    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3538      <organization>Google</organization>
3539      <address><email>Harald@Alvestrand.no</email></address>
3540    </author>
3541    <date year='2008' month='May' />
3542  </front>
3543  <seriesInfo name='BCP' value='26' />
3544  <seriesInfo name='RFC' value='5226' />
3545</reference>
3546
3547<reference anchor="RFC5322">
3548  <front>
3549    <title>Internet Message Format</title>
3550    <author initials="P." surname="Resnick" fullname="P. Resnick">
3551      <organization>Qualcomm Incorporated</organization>
3552    </author>
3553    <date year="2008" month="October"/>
3554  </front> 
3555  <seriesInfo name="RFC" value="5322"/>
3556</reference>
3557
3558<reference anchor='RFC5789'>
3559  <front>
3560    <title>PATCH Method for HTTP</title>
3561    <author initials='L.' surname='Dusseault' fullname='L. Dusseault'>
3562      <organization>Linden Lab</organization>
3563    </author>
3564    <author initials='J.' surname='Snell' fullname='J. Snell' />
3565    <date year='2010' month='March' />
3566  </front>
3567  <seriesInfo name='RFC' value='5789' />
3568</reference>
3569
3570<reference anchor="RFC5987">
3571        <front>
3572    <title>Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters</title>
3573    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke">
3574      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3575      <address>
3576        <postal>
3577          <street>Hafenweg 16</street>
3578          <city>Muenster</city><region>NW</region><code>48155</code>
3579          <country>Germany</country>
3580        </postal>
3581        <email>julian.reschke@greenbytes.de</email>     
3582        <uri>http://greenbytes.de/tech/webdav/</uri>   
3583      </address>
3584    </author>
3585    <date month="August" year="2010"/>
3586  </front>
3587  <seriesInfo name="RFC" value="5987"/>
3588</reference>
3589
3590</references>
3591
3592<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3593<t>
3594  This document takes over the Status Code Registry, previously defined
3595  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3596  (<xref target="status.code.registry"/>)
3597</t>
3598<t>
3599  Clarify definition of POST.
3600  (<xref target="POST"/>)
3601</t>
3602<t>
3603  Remove requirement to handle all Content-* header fields; ban use of
3604  Content-Range with PUT.
3605  (<xref target="PUT"/>)
3606</t>
3607<t>
3608  Take over definition of CONNECT method from <xref target="RFC2817"/>.
3609  (<xref target="CONNECT"/>)
3610</t>
3611<t>
3612  Broadened the definition of 203 (Non-Authoritative Information) to include
3613  cases of payload transformations as well.
3614  (<xref target="status.203"/>)
3615</t>
3616<t>
3617  Failed to consider that there are
3618  many other request methods that are safe to automatically redirect,
3619  and further that the user agent is able to make that determination
3620  based on the request method semantics.
3621  (Sections <xref format="counter" target="status.301"/>,
3622  <xref format="counter" target="status.302"/> and
3623  <xref format="counter" target="status.307"/>)
3624</t>
3625<t>
3626  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3627  It used to indicate that the target resource must be accessed through the
3628  proxy given by the Location field. The Location field gave the URI of the
3629  proxy. The recipient was expected to repeat this single request via the proxy.
3630  (<xref target="status.305"/>)
3631</t>
3632<t>
3633  Define status 426 (Upgrade Required) (this was incorporated from
3634  <xref target="RFC2817"/>).
3635  (<xref target="status.426"/>)
3636</t>
3637<t>
3638  Change ABNF productions for header fields to only define the field value.
3639  (<xref target="header.field.definitions"/>)
3640</t>
3641<t>
3642  Reclassify "Allow" as response header field, removing the option to
3643  specify it in a PUT request.
3644  Relax the server requirement on the contents of the Allow header field and
3645  remove requirement on clients to always trust the header field value.
3646  (<xref target="header.allow"/>)
3647</t>
3648<t>
3649  Correct syntax of Location header field to allow URI references (including
3650  relative references and fragments), as referred symbol "absoluteURI" wasn't
3651  what was expected, and add some clarifications as to when use of fragments
3652  would not be appropriate.
3653  (<xref target="header.location"/>)
3654</t>
3655<t>
3656  Restrict Max-Forwards header field to OPTIONS and TRACE (previously,
3657  extension methods could have used it as well).
3658  (<xref target="header.max-forwards"/>)
3659</t>
3660<t>
3661  Allow Referer field value of "about:blank" as alternative to not specifying it.
3662  (<xref target="header.referer"/>)
3663</t>
3664<t>
3665  In the description of the Server header field, the Via field
3666  was described as a SHOULD. The requirement was and is stated
3667  correctly in the description of the Via header field in &header-via;.
3668  (<xref target="header.server"/>)
3669</t>
3670</section>
3671
3672<?BEGININC p2-semantics.abnf-appendix ?>
3673<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3674<figure>
3675<artwork type="abnf" name="p2-semantics.parsed-abnf">
3676<x:ref>Allow</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3677
3678<x:ref>Expect</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3679
3680<x:ref>From</x:ref> = mailbox
3681
3682<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 6.1&gt;
3683
3684<x:ref>Location</x:ref> = URI-reference
3685
3686<x:ref>Max-Forwards</x:ref> = 1*DIGIT
3687<x:ref>Method</x:ref> = token
3688
3689<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
3690
3691<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3692<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
3693<x:ref>Referer</x:ref> = absolute-URI / partial-URI
3694<x:ref>Retry-After</x:ref> = HTTP-date / delta-seconds
3695
3696<x:ref>Server</x:ref> = product *( RWS ( product / comment ) )
3697<x:ref>Status-Code</x:ref> = 3DIGIT
3698
3699<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.7&gt;
3700<x:ref>User-Agent</x:ref> = product *( RWS ( product / comment ) )
3701
3702<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.7&gt;
3703
3704<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2&gt;
3705
3706<x:ref>delta-seconds</x:ref> = 1*DIGIT
3707
3708<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
3709<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
3710<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
3711 *expect-params ]
3712
3713<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
3714
3715<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
3716
3717<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.7&gt;
3718<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 6.3&gt;
3719
3720<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 3.2.3&gt;
3721
3722<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 3.2.3&gt;
3723</artwork>
3724</figure>
3725<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
3726; Allow defined but not used
3727; Expect defined but not used
3728; From defined but not used
3729; Location defined but not used
3730; Max-Forwards defined but not used
3731; Reason-Phrase defined but not used
3732; Referer defined but not used
3733; Retry-After defined but not used
3734; Server defined but not used
3735; Status-Code defined but not used
3736; User-Agent defined but not used
3737</artwork></figure></section>
3738<?ENDINC p2-semantics.abnf-appendix ?>
3739
3740<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3741
3742<section title="Since RFC 2616">
3743<t>
3744  Extracted relevant partitions from <xref target="RFC2616"/>.
3745</t>
3746</section>
3747
3748<section title="Since draft-ietf-httpbis-p2-semantics-00">
3749<t>
3750  Closed issues:
3751  <list style="symbols"> 
3752    <t>
3753      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3754      "Via is a MUST"
3755      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3756    </t>
3757    <t>
3758      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3759      "Fragments allowed in Location"
3760      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3761    </t>
3762    <t>
3763      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3764      "Safe Methods vs Redirection"
3765      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3766    </t>
3767    <t>
3768      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3769      "Revise description of the POST method"
3770      (<eref target="http://purl.org/NET/http-errata#post"/>)
3771    </t>
3772    <t>
3773      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3774      "Normative and Informative references"
3775    </t>
3776    <t>
3777      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3778      "RFC2606 Compliance"
3779    </t>
3780    <t>
3781      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3782      "Informative references"
3783    </t>
3784    <t>
3785      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3786      "Redundant cross-references"
3787    </t>
3788  </list>
3789</t>
3790<t>
3791  Other changes:
3792  <list style="symbols"> 
3793    <t>
3794      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3795    </t>
3796  </list>
3797</t>
3798</section>
3799
3800<section title="Since draft-ietf-httpbis-p2-semantics-01">
3801<t>
3802  Closed issues:
3803  <list style="symbols"> 
3804    <t>
3805      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3806      "PUT side effects"
3807    </t>
3808    <t>
3809      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3810      "Duplicate Host header requirements"
3811    </t>
3812  </list>
3813</t>
3814<t>
3815  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3816  <list style="symbols"> 
3817    <t>
3818      Move "Product Tokens" section (back) into Part 1, as "token" is used
3819      in the definition of the Upgrade header field.
3820    </t>
3821    <t>
3822      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3823    </t>
3824    <t>
3825      Copy definition of delta-seconds from Part6 instead of referencing it.
3826    </t>
3827  </list>
3828</t>
3829</section>
3830
3831<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3832<t>
3833  Closed issues:
3834  <list style="symbols"> 
3835    <t>
3836      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3837      "Requiring Allow in 405 responses"
3838    </t>
3839    <t>
3840      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3841      "Status Code Registry"
3842    </t>
3843    <t>
3844      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3845      "Redirection vs. Location"
3846    </t>
3847    <t>
3848      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3849      "Cacheability of 303 response"
3850    </t>
3851    <t>
3852      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3853      "305 Use Proxy"
3854    </t>
3855    <t>
3856      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3857      "Classification for Allow header"
3858    </t>
3859    <t>
3860      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3861      "PUT - 'store under' vs 'store at'"
3862    </t>
3863  </list>
3864</t>
3865<t>
3866  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3867  <list style="symbols"> 
3868    <t>
3869      Reference RFC 3984, and update header field registrations for headers defined
3870      in this document.
3871    </t>
3872  </list>
3873</t>
3874<t>
3875  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3876  <list style="symbols"> 
3877    <t>
3878      Replace string literals when the string really is case-sensitive (method).
3879    </t>
3880  </list>
3881</t>
3882</section>
3883
3884<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3885<t>
3886  Closed issues:
3887  <list style="symbols"> 
3888    <t>
3889      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
3890      "OPTIONS request bodies"
3891    </t>
3892    <t>
3893      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
3894      "Description of CONNECT should refer to RFC2817"
3895    </t>
3896    <t>
3897      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
3898      "Location Content-Location reference request/response mixup"
3899    </t>
3900  </list>
3901</t>
3902<t>
3903  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
3904  <list style="symbols"> 
3905    <t>
3906      Added initial proposal for registration process, plus initial
3907      content (non-HTTP/1.1 methods to be added by a separate specification).
3908    </t>
3909  </list>
3910</t>
3911</section>
3912
3913<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3914<t>
3915  Closed issues:
3916  <list style="symbols"> 
3917    <t>
3918      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3919      "Content-*"
3920    </t>
3921    <t>
3922      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3923      "RFC 2822 is updated by RFC 5322"
3924    </t>
3925  </list>
3926</t>
3927<t>
3928  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3929  <list style="symbols"> 
3930    <t>
3931      Use "/" instead of "|" for alternatives.
3932    </t>
3933    <t>
3934      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3935      whitespace ("OWS") and required whitespace ("RWS").
3936    </t>
3937    <t>
3938      Rewrite ABNFs to spell out whitespace rules, factor out
3939      header field value format definitions.
3940    </t>
3941  </list>
3942</t>
3943</section>
3944
3945<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3946<t>
3947  Closed issues:
3948  <list style="symbols"> 
3949    <t>
3950      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
3951      "Reason-Phrase BNF"
3952    </t>
3953  </list>
3954</t>
3955<t>
3956  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3957  <list style="symbols"> 
3958    <t>
3959      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3960    </t>
3961  </list>
3962</t>
3963</section>
3964
3965<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
3966<t>
3967  Closed issues:
3968  <list style="symbols"> 
3969    <t>
3970      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
3971      "Clarify when Referer is sent"
3972    </t>
3973    <t>
3974      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
3975      "status codes vs methods"
3976    </t>
3977    <t>
3978      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
3979      "Do not require "updates" relation for specs that register status codes or method names"
3980    </t>
3981  </list>
3982</t>
3983</section>
3984
3985<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
3986<t>
3987  Closed issues:
3988  <list style="symbols"> 
3989    <t>
3990      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
3991      "Idempotency"
3992    </t>
3993    <t>
3994      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
3995      "TRACE security considerations"
3996    </t>
3997    <t>
3998      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
3999      "Clarify rules for determining what entities a response carries"
4000    </t>
4001    <t>
4002      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
4003      "update note citing RFC 1945 and 2068"
4004    </t>
4005    <t>
4006      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
4007      "update note about redirect limit"
4008    </t>
4009    <t>
4010      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
4011      "Location header ABNF should use 'URI'"
4012    </t>
4013    <t>
4014      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
4015      "fragments in Location vs status 303"
4016    </t>
4017    <t>
4018      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
4019      "move IANA registrations for optional status codes"
4020    </t>
4021  </list>
4022</t>
4023<t>
4024  Partly resolved issues:
4025  <list style="symbols"> 
4026    <t>
4027      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
4028      "Are OPTIONS and TRACE safe?"
4029    </t>
4030  </list>
4031</t>
4032</section>
4033
4034<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
4035<t>
4036  Closed issues:
4037  <list style="symbols"> 
4038    <t>
4039      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
4040      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
4041      status codes when fixing this previously)
4042    </t>
4043  </list>
4044</t>
4045</section>
4046
4047<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
4048<t>
4049  Closed issues:
4050  <list style="symbols"> 
4051    <t>
4052      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4053      "Fragment combination / precedence during redirects"
4054    </t>
4055  </list>
4056</t>
4057<t>
4058  Partly resolved issues:
4059  <list style="symbols"> 
4060    <t>
4061      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
4062      "Location header payload handling"
4063    </t>
4064    <t>
4065      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
4066      "Term for the requested resource's URI"
4067    </t>
4068  </list>
4069</t>
4070</section>
4071
4072<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
4073<t>
4074  Closed issues:
4075  <list style="symbols"> 
4076    <t>
4077      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
4078      "Clarify 'Requested Variant'"
4079    </t>
4080    <t>
4081      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
4082      "Clarify entity / representation / variant terminology"
4083    </t>
4084    <t>
4085      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/139"/>:
4086      "Methods and Caching"
4087    </t>
4088    <t>
4089      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/190"/>:
4090      "OPTIONS vs Max-Forwards"
4091    </t>
4092    <t>
4093      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/199"/>:
4094      "Status codes and caching"
4095    </t>
4096    <t>
4097      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
4098      "consider removing the 'changes from 2068' sections"
4099    </t>
4100  </list>
4101</t>
4102</section>
4103
4104<section title="Since draft-ietf-httpbis-p2-semantics-11" anchor="changes.since.11">
4105<t>
4106  Closed issues:
4107  <list style="symbols"> 
4108    <t>
4109      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/229"/>:
4110      "Considerations for new status codes"
4111    </t>
4112    <t>
4113      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/230"/>:
4114      "Considerations for new methods"
4115    </t>
4116    <t>
4117      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/232"/>:
4118      "User-Agent guidelines" (relating to the 'User-Agent' header field)
4119    </t>
4120  </list>
4121</t>
4122</section>
4123
4124<section title="Since draft-ietf-httpbis-p2-semantics-12" anchor="changes.since.12">
4125<t>
4126  Closed issues:
4127  <list style="symbols"> 
4128    <t>
4129      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4130      "Fragment combination / precedence during redirects" (added warning
4131      about having a fragid on the redirect may cause inconvenience in
4132      some cases)
4133    </t>
4134    <t>
4135      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/79"/>:
4136      "Content-* vs. PUT"
4137    </t>
4138    <t>
4139      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/88"/>:
4140      "205 Bodies"
4141    </t>
4142    <t>
4143      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/102"/>:
4144      "Understanding Content-* on non-PUT requests"
4145    </t>
4146    <t>
4147      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
4148      "Content-*"
4149    </t>
4150    <t>
4151      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/104"/>:
4152      "Header type defaulting"
4153    </t>
4154    <t>
4155      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
4156      "PUT - 'store under' vs 'store at'"
4157    </t>
4158    <t>
4159      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/137"/>:
4160      "duplicate ABNF for Reason-Phrase"
4161    </t>
4162    <t>
4163      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/180"/>:
4164      "Note special status of Content-* prefix in header registration procedures"
4165    </t>
4166    <t>
4167      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/203"/>:
4168      "Max-Forwards vs extension methods"
4169    </t>
4170    <t>
4171      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/213"/>:
4172      "What is the value space of HTTP status codes?" (actually fixed in
4173      draft-ietf-httpbis-p2-semantics-11)
4174    </t>
4175    <t>
4176      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/224"/>:
4177      "Header Classification"
4178    </t>
4179    <t>
4180      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/225"/>:
4181      "PUT side effect: invalidation or just stale?"
4182    </t>
4183    <t>
4184      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/226"/>:
4185      "proxies not supporting certain methods"
4186    </t>
4187    <t>
4188      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/239"/>:
4189      "Migrate CONNECT from RFC2817 to p2"
4190    </t>
4191    <t>
4192      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/240"/>:
4193      "Migrate Upgrade details from RFC2817"
4194    </t>
4195    <t>
4196      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/267"/>:
4197      "clarify PUT semantics'"
4198    </t>
4199    <t>
4200      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/275"/>:
4201      "duplicate ABNF for 'Method'"
4202    </t>
4203    <t>
4204      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4205      "untangle ABNFs for header fields"
4206    </t>
4207  </list>
4208</t>
4209</section>
4210
4211<section title="Since draft-ietf-httpbis-p2-semantics-13" anchor="changes.since.13">
4212<t>
4213  Closed issues:
4214  <list style="symbols"> 
4215    <t>
4216      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4217      "untangle ABNFs for header fields"
4218    </t>
4219    <t>
4220      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/251"/>:
4221      "message-body in CONNECT request"
4222    </t>
4223  </list>
4224</t>
4225</section>
4226
4227<section title="Since draft-ietf-httpbis-p2-semantics-14" anchor="changes.since.14">
4228<t>
4229  Closed issues:
4230  <list style="symbols"> 
4231    <t>
4232      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/255"/>:
4233      "Clarify status code for rate limiting"
4234    </t>
4235    <t>
4236      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/294"/>:
4237      "clarify 403 forbidden"
4238    </t>
4239    <t>
4240      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/296"/>:
4241      "Clarify 203 Non-Authoritative Information"
4242    </t>
4243    <t>
4244      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/298"/>:
4245      "update default reason phrase for 413"
4246    </t>
4247  </list>
4248</t>
4249</section>
4250
4251<section title="Since draft-ietf-httpbis-p2-semantics-15" anchor="changes.since.15">
4252<t>
4253  Closed issues:
4254  <list style="symbols"> 
4255    <t>
4256      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/285"/>:
4257      "Strength of requirements on Accept re: 406"
4258    </t>
4259    <t>
4260      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/303"/>:
4261      "400 response isn't generic"
4262    </t>
4263  </list>
4264</t>
4265</section>
4266
4267<section title="Since draft-ietf-httpbis-p2-semantics-16" anchor="changes.since.16">
4268<t>
4269  Work-in-progress:
4270  <list style="symbols"> 
4271    <t>
4272      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/231"/>:
4273      "Considerations for new headers"
4274    </t>
4275  </list>
4276</t>
4277</section>
4278
4279</section>
4280
4281</back>
4282</rfc>
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