source: draft-ietf-httpbis/latest/p2-semantics.xml @ 1163

Last change on this file since 1163 was 1163, checked in by fielding@…, 9 years ago

Remove header field classifications.

Addresses #224 and #104

  • Property svn:eol-style set to native
File size: 173.7 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 "March">
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 messaging                  "<xref target='Part1' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY payload                    "<xref target='Part3' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY conditional                "<xref target='Part4' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY range                      "<xref target='Part5' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23  <!ENTITY caching                    "<xref target='Part6' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
24  <!ENTITY auth                       "<xref target='Part7' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
25  <!ENTITY combining-responses        "<xref target='Part6' x:rel='#combining.responses' 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 uri                        "<xref target='Part1' x:rel='#uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY effective-request-uri      "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY full-date                  "<xref target='Part1' x:rel='#date.time.formats.full.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY request-target             "<xref target='Part1' x:rel='#request-target' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
42  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
43  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
44  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
45  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
46  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
47  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
48  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
49  <!ENTITY header-fields              "<xref target='Part1' x:rel='#header.fields' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
50  <!ENTITY header-host                "<xref target='Part1' x:rel='#header.host' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
51  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
52  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
53  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
54  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
55  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
56  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
57  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
58  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
59  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
60  <!ENTITY header-upgrade             "<xref target='Part1' x:rel='#header.upgrade' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
61  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.te' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
62  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
63  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
64  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
65  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
66  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
67  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
68  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='#internet.media.type.message.http' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
69  <!ENTITY status-206                 "<xref target='Part5' x:rel='#status.206' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
70  <!ENTITY status-304                 "<xref target='Part4' x:rel='#status.304' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
71  <!ENTITY status-401                 "<xref target='Part7' x:rel='#status.401' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
72  <!ENTITY status-407                 "<xref target='Part7' x:rel='#status.407' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
73  <!ENTITY status-412                 "<xref target='Part4' x:rel='#status.412' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
74  <!ENTITY status-416                 "<xref target='Part5' x:rel='#status.416' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
75  <!ENTITY p4-status-codes            "<xref target='Part4' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
76  <!ENTITY p5-status-codes            "<xref target='Part5' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
77  <!ENTITY p7-status-codes            "<xref target='Part7' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
78  <!ENTITY p6-heuristic               "<xref target='Part6' x:rel='#heuristic.freshness' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
79  <!ENTITY p6-explicit                "<xref target='Part6' x:rel='#calculating.freshness.lifetime' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
80  <!ENTITY p6-invalid                 "<xref target='Part6' x:rel='#invalidation.after.updates.or.deletions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
81]>
82<?rfc toc="yes" ?>
83<?rfc symrefs="yes" ?>
84<?rfc sortrefs="yes" ?>
85<?rfc compact="yes"?>
86<?rfc subcompact="no" ?>
87<?rfc linkmailto="no" ?>
88<?rfc editing="no" ?>
89<?rfc comments="yes"?>
90<?rfc inline="yes"?>
91<?rfc rfcedstyle="yes"?>
92<?rfc-ext allow-markup-in-artwork="yes" ?>
93<?rfc-ext include-references-in-index="yes" ?>
94<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
95     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
96     xmlns:x='http://purl.org/net/xml2rfc/ext'
97     xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
98<front>
99
100  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
101
102  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
103    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
104    <address>
105      <postal>
106        <street>345 Park Ave</street>
107        <city>San Jose</city>
108        <region>CA</region>
109        <code>95110</code>
110        <country>USA</country>
111      </postal>
112      <email>fielding@gbiv.com</email>
113      <uri>http://roy.gbiv.com/</uri>
114    </address>
115  </author>
116
117  <author initials="J." surname="Gettys" fullname="Jim Gettys">
118    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
119    <address>
120      <postal>
121        <street>21 Oak Knoll Road</street>
122        <city>Carlisle</city>
123        <region>MA</region>
124        <code>01741</code>
125        <country>USA</country>
126      </postal>
127      <email>jg@freedesktop.org</email>
128      <uri>http://gettys.wordpress.com/</uri>
129    </address>
130  </author>
131 
132  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
133    <organization abbrev="HP">Hewlett-Packard Company</organization>
134    <address>
135      <postal>
136        <street>HP Labs, Large Scale Systems Group</street>
137        <street>1501 Page Mill Road, MS 1177</street>
138        <city>Palo Alto</city>
139        <region>CA</region>
140        <code>94304</code>
141        <country>USA</country>
142      </postal>
143      <email>JeffMogul@acm.org</email>
144    </address>
145  </author>
146
147  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
148    <organization abbrev="Microsoft">Microsoft Corporation</organization>
149    <address>
150      <postal>
151        <street>1 Microsoft Way</street>
152        <city>Redmond</city>
153        <region>WA</region>
154        <code>98052</code>
155        <country>USA</country>
156      </postal>
157      <email>henrikn@microsoft.com</email>
158    </address>
159  </author>
160
161  <author initials="L." surname="Masinter" fullname="Larry Masinter">
162    <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
163    <address>
164      <postal>
165        <street>345 Park Ave</street>
166        <city>San Jose</city>
167        <region>CA</region>
168        <code>95110</code>
169        <country>USA</country>
170      </postal>
171      <email>LMM@acm.org</email>
172      <uri>http://larry.masinter.net/</uri>
173    </address>
174  </author>
175 
176  <author initials="P." surname="Leach" fullname="Paul J. Leach">
177    <organization abbrev="Microsoft">Microsoft Corporation</organization>
178    <address>
179      <postal>
180        <street>1 Microsoft Way</street>
181        <city>Redmond</city>
182        <region>WA</region>
183        <code>98052</code>
184      </postal>
185      <email>paulle@microsoft.com</email>
186    </address>
187  </author>
188   
189  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
190    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
191    <address>
192      <postal>
193        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
194        <street>The Stata Center, Building 32</street>
195        <street>32 Vassar Street</street>
196        <city>Cambridge</city>
197        <region>MA</region>
198        <code>02139</code>
199        <country>USA</country>
200      </postal>
201      <email>timbl@w3.org</email>
202      <uri>http://www.w3.org/People/Berners-Lee/</uri>
203    </address>
204  </author>
205
206  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
207    <organization abbrev="W3C">World Wide Web Consortium</organization>
208    <address>
209      <postal>
210        <street>W3C / ERCIM</street>
211        <street>2004, rte des Lucioles</street>
212        <city>Sophia-Antipolis</city>
213        <region>AM</region>
214        <code>06902</code>
215        <country>France</country>
216      </postal>
217      <email>ylafon@w3.org</email>
218      <uri>http://www.raubacapeu.net/people/yves/</uri>
219    </address>
220  </author>
221
222  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
223    <organization abbrev="greenbytes">greenbytes GmbH</organization>
224    <address>
225      <postal>
226        <street>Hafenweg 16</street>
227        <city>Muenster</city><region>NW</region><code>48155</code>
228        <country>Germany</country>
229      </postal>
230      <phone>+49 251 2807760</phone>
231      <facsimile>+49 251 2807761</facsimile>
232      <email>julian.reschke@greenbytes.de</email>
233      <uri>http://greenbytes.de/tech/webdav/</uri>
234    </address>
235  </author>
236
237  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
238  <workgroup>HTTPbis Working Group</workgroup>
239
240<abstract>
241<t>
242   The Hypertext Transfer Protocol (HTTP) is an application-level
243   protocol for distributed, collaborative, hypermedia information
244   systems. HTTP has been in use by the World Wide Web global information
245   initiative since 1990. This document is Part 2 of the seven-part specification
246   that defines the protocol referred to as "HTTP/1.1" and, taken together,
247   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
248   as expressed by request methods, request header fields, response status codes,
249   and response header fields.
250</t>
251</abstract>
252
253<note title="Editorial Note (To be removed by RFC Editor)">
254  <t>
255    Discussion of this draft should take place on the HTTPBIS working group
256    mailing list (ietf-http-wg@w3.org). The current issues list is
257    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/>
258    and related documents (including fancy diffs) can be found at
259    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
260  </t>
261  <t>
262    The changes in this draft are summarized in <xref target="changes.since.12"/>.
263  </t>
264</note>
265</front>
266<middle>
267<section title="Introduction" anchor="introduction">
268<t>
269   This document defines HTTP/1.1 request and response semantics.  Each HTTP
270   message, as defined in &messaging;, is in the form of either a request or
271   a response.  An HTTP server listens on a connection for HTTP requests and
272   responds to each request, in the order received on that connection, with
273   one or more HTTP response messages.  This document defines the commonly
274   agreed upon semantics of the HTTP uniform interface, the intentions defined
275   by each request method, and the various response messages that might be
276   expected as a result of applying that method to the target resource.
277</t>
278<t>
279   This document is currently disorganized in order to minimize the changes
280   between drafts and enable reviewers to see the smaller errata changes.
281   A future draft will reorganize the sections to better reflect the content.
282   In particular, the sections will be ordered according to the typical
283   processing of an HTTP request message (after message parsing): resource
284   mapping, methods, request modifying header fields, response status,
285   status modifying header fields, and resource metadata.  The current mess
286   reflects how widely dispersed these topics and associated requirements
287   had become in <xref target="RFC2616"/>.
288</t>
289
290<section title="Requirements" anchor="intro.requirements">
291<t>
292   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
293   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
294   document are to be interpreted as described in <xref target="RFC2119"/>.
295</t>
296<t>
297   An implementation is not compliant if it fails to satisfy one or more
298   of the "MUST" or "REQUIRED" level requirements for the protocols it
299   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
300   level and all the "SHOULD" level requirements for its protocols is said
301   to be "unconditionally compliant"; one that satisfies all the "MUST"
302   level requirements but not all the "SHOULD" level requirements for its
303   protocols is said to be "conditionally compliant".
304</t>
305</section>
306
307<section title="Syntax Notation" anchor="notation">
308  <x:anchor-alias value="CR"/>
309  <x:anchor-alias value="DIGIT"/>
310  <x:anchor-alias value="LF"/>
311  <x:anchor-alias value="VCHAR"/>
312  <x:anchor-alias value="WSP"/>
313<t>
314  This specification uses the ABNF syntax defined in &notation; (which
315  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
316  <xref target="collected.abnf"/> shows the collected ABNF, with the list
317  rule expanded.
318</t>
319<t>
320  The following core rules are included by
321  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
322  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
323  DIGIT (decimal 0-9), DQUOTE (double quote),
324  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
325  OCTET (any 8-bit sequence of data), SP (space),
326  VCHAR (any visible USASCII character),
327  and WSP (whitespace).
328</t>
329
330<section title="Core Rules" anchor="core.rules">
331  <x:anchor-alias value="obs-text"/>
332  <x:anchor-alias value="quoted-string"/>
333  <x:anchor-alias value="token"/>
334  <x:anchor-alias value="OWS"/>
335  <x:anchor-alias value="RWS"/>
336<t>
337  The core rules below are defined in &basic-rules;:
338</t>
339<figure><artwork type="abnf2616">
340  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
341  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
342  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
343  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
344  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
345</artwork></figure>
346</section>
347
348<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
349  <x:anchor-alias value="absolute-URI"/>
350  <x:anchor-alias value="Accept"/>
351  <x:anchor-alias value="Accept-Charset"/>
352  <x:anchor-alias value="Accept-Encoding"/>
353  <x:anchor-alias value="Accept-Language"/>
354  <x:anchor-alias value="Accept-Ranges"/>
355  <x:anchor-alias value="Age"/>
356  <x:anchor-alias value="Authorization"/>
357  <x:anchor-alias value="comment"/>
358  <x:anchor-alias value="ETag"/>
359  <x:anchor-alias value="Host"/>
360  <x:anchor-alias value="HTTP-date"/>
361  <x:anchor-alias value="If-Match"/>
362  <x:anchor-alias value="If-Modified-Since"/>
363  <x:anchor-alias value="If-None-Match"/>
364  <x:anchor-alias value="If-Range"/>
365  <x:anchor-alias value="If-Unmodified-Since"/>
366  <x:anchor-alias value="partial-URI"/>
367  <x:anchor-alias value="product"/>
368  <x:anchor-alias value="Proxy-Authenticate"/>
369  <x:anchor-alias value="Proxy-Authorization"/>
370  <x:anchor-alias value="Range"/>
371  <x:anchor-alias value="TE"/>
372  <x:anchor-alias value="URI-reference"/>
373  <x:anchor-alias value="Vary"/>
374  <x:anchor-alias value="WWW-Authenticate"/>
375<t>
376  The ABNF rules below are defined in other parts:
377</t>
378<figure><!--Part1--><artwork type="abnf2616">
379  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
380  <x:ref>comment</x:ref>       = &lt;comment, defined in &header-fields;&gt;
381  <x:ref>Host</x:ref>          = &lt;Host, defined in &uri;&gt;
382  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
383  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
384  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
385  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
386  <x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in &uri;&gt;
387</artwork></figure>
388<figure><!--Part3--><artwork type="abnf2616">
389  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
390  <x:ref>Accept-Charset</x:ref> =
391             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
392  <x:ref>Accept-Encoding</x:ref> =
393             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
394  <x:ref>Accept-Language</x:ref> =
395             &lt;Accept-Language, defined in &header-accept-language;&gt;
396</artwork></figure>
397<figure><!--Part4--><artwork type="abnf2616">
398  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
399  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
400  <x:ref>If-Modified-Since</x:ref> =
401             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
402  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
403  <x:ref>If-Unmodified-Since</x:ref> =
404             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
405</artwork></figure>
406<figure><!--Part5--><artwork type="abnf2616">
407  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
408  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
409  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
410</artwork></figure>
411<figure><!--Part6--><artwork type="abnf2616">
412  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
413  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
414</artwork><!--Part7--></figure>
415<figure><artwork type="abnf2616">
416  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
417  <x:ref>Proxy-Authenticate</x:ref> =
418             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
419  <x:ref>Proxy-Authorization</x:ref> =
420             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
421  <x:ref>WWW-Authenticate</x:ref> =
422             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
423</artwork></figure>
424</section>
425</section>
426</section>
427
428<section title="Method" anchor="method">
429  <x:anchor-alias value="Method"/>
430  <x:anchor-alias value="extension-method"/>
431<t>
432   The Method token indicates the request method to be performed on the target
433   resource (&effective-request-uri;). The method is case-sensitive.
434</t>
435<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/>
436  <x:ref>Method</x:ref>         = <x:ref>token</x:ref>
437</artwork></figure>
438<t>
439   The list of methods allowed by a resource can be specified in an
440   Allow header field (<xref target="header.allow"/>). The status code of the response
441   always notifies the client whether a method is currently allowed on a
442   resource, since the set of allowed methods can change dynamically. An
443   origin server &SHOULD; respond with the status code 405 (Method Not Allowed)
444   if the method is known by the origin server but not allowed for the
445   resource, and 501 (Not Implemented) if the method is
446   unrecognized or not implemented by the origin server. The methods GET
447   and HEAD &MUST; be supported by all general-purpose servers. All other
448   methods are &OPTIONAL;; however, if the above methods are implemented,
449   they &MUST; be implemented with the same semantics as those specified
450   in <xref target="method.definitions"/>.
451</t>
452
453<section title="Overview of Methods" anchor="overview.of.methods">
454<t>
455  The methods listed below are defined in <xref target="method.definitions"/>.
456</t>
457<texttable align="left">
458  <ttcol>Method Name</ttcol><ttcol>Defined in...</ttcol>
459 
460  <c>OPTIONS</c> <c><xref target="OPTIONS"/></c>
461  <c>GET</c> <c><xref target="GET"/></c>
462  <c>HEAD</c> <c><xref target="HEAD"/></c>
463  <c>POST</c> <c><xref target="POST"/></c>
464  <c>PUT</c> <c><xref target="PUT"/></c>
465  <c>DELETE</c> <c><xref target="DELETE"/></c>
466  <c>TRACE</c> <c><xref target="TRACE"/></c>
467  <c>CONNECT</c> <c><xref target="CONNECT"/></c>
468</texttable>
469<t>
470  Note that this list is not exhaustive &mdash; it does not include request methods defined
471  in other specifications.
472</t>
473</section>
474
475<section title="Method Registry" anchor="method.registry">
476<t>
477  The HTTP Method Registry defines the name space for the Method token in the
478  Request line of an HTTP request.
479</t>
480<t>
481  Registrations &MUST; include the following fields:
482  <list style="symbols">
483    <t>Method Name (see <xref target="method"/>)</t>
484    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
485    <t>Pointer to specification text</t>
486  </list>
487</t>
488<t>
489  Values to be added to this name space are subject to IETF review
490  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
491</t>
492<t>
493  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
494</t>
495
496<section title="Considerations for New Methods" anchor="considerations.for.new.methods">
497<t>
498   When it is necessary to express new semantics for a HTTP request that
499   aren't specific to a single application or media type, and currently defined
500   methods are inadequate, it may be appropriate to register a new method.
501</t>
502<t>
503   HTTP methods are generic; that is, they are potentially applicable to any
504   resource, not just one particular media type, "type" of resource, or
505   application. As such, it is preferred that new HTTP methods be registered
506   in a document that isn't specific to a single application, so that this is
507   clear.
508</t>
509<t>
510   Due to the parsing rules defined in &message-body;, definitions of HTTP
511   methods cannot prohibit the presence of a message-body on either the request
512   or the response message (with responses to HEAD requests being the single
513   exception). Definitions of new methods cannot change this rule, but they can
514   specify that only zero-length bodies (as opposed to absent bodies) are allowed.
515</t>
516<t>
517   New method definitions need to indicate whether they are safe (<xref
518   target="safe.methods"/>) and whether they are idempotent (<xref
519   target="idempotent.methods"/>). They also need to state whether they can be
520   cached (&caching;); in particular what conditions a cache may store the
521   response, and under what conditions such a stored response may be used to
522   satisfy a subsequent request.
523</t>
524</section>
525
526</section>
527</section>
528
529<section title="Request Header Fields" anchor="request.header.fields">
530  <x:anchor-alias value="request-header"/>
531<t>
532   The request header fields allow the client to pass additional
533   information about the request, and about the client itself, to the
534   server. These fields act as request modifiers, with semantics
535   equivalent to the parameters on a programming language method
536   invocation.
537</t>
538<texttable align="left">
539  <ttcol>Header Field Name</ttcol>
540  <ttcol>Defined in...</ttcol>
541
542  <c>Accept</c> <c>&header-accept;</c>
543  <c>Accept-Charset</c> <c>&header-accept-charset;</c>
544  <c>Accept-Encoding</c> <c>&header-accept-encoding;</c>
545  <c>Accept-Language</c> <c>&header-accept-language;</c>
546  <c>Authorization</c> <c>&header-authorization;</c>
547  <c>Expect</c> <c><xref target="header.expect"/></c>
548  <c>From</c> <c><xref target="header.from"/></c>
549  <c>Host</c> <c>&header-host;</c>
550  <c>If-Match</c> <c>&header-if-match;</c>
551  <c>If-Modified-Since</c> <c>&header-if-modified-since;</c>
552  <c>If-None-Match</c> <c>&header-if-none-match;</c>
553  <c>If-Range</c> <c>&header-if-range;</c>
554  <c>If-Unmodified-Since</c> <c>&header-if-unmodified-since;</c>
555  <c>Max-Forwards</c> <c><xref target="header.max-forwards"/></c>
556  <c>Proxy-Authorization</c> <c>&header-proxy-authorization;</c>
557  <c>Range</c> <c>&header-range;</c>
558  <c>Referer</c> <c><xref target="header.referer"/></c>
559  <c>TE</c> <c>&header-te;</c>
560  <c>User-Agent</c> <c><xref target="header.user-agent"/></c>
561</texttable>
562</section>
563
564<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
565  <x:anchor-alias value="Reason-Phrase"/>
566  <x:anchor-alias value="Status-Code"/>
567  <x:anchor-alias value="extension-code"/>
568<t>
569   The Status-Code element is a 3-digit integer result code of the attempt to
570   understand and satisfy the request.
571</t>
572<t>
573   The Reason-Phrase is intended to give a short textual description of the
574   Status-Code and is intended for a human user. The client does not need
575   to examine or display the Reason-Phrase.
576</t>
577<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"/>
578  <x:ref>Status-Code</x:ref>    = 3<x:ref>DIGIT</x:ref>
579  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
580</artwork></figure>
581<t>
582   HTTP status codes are extensible. HTTP applications are not required
583   to understand the meaning of all registered status codes, though such
584   understanding is obviously desirable. However, applications &MUST;
585   understand the class of any status code, as indicated by the first
586   digit, and treat any unrecognized response as being equivalent to the
587   x00 status code of that class, with the exception that an
588   unrecognized response &MUST-NOT; be cached. For example, if an
589   unrecognized status code of 431 is received by the client, it can
590   safely assume that there was something wrong with its request and
591   treat the response as if it had received a 400 status code. In such
592   cases, user agents &SHOULD; present to the user the representation enclosed
593   with the response, since that representation is likely to include human-readable
594   information which will explain the unusual status.
595</t>
596
597<section title="Overview of Status Codes" anchor="overview.of.status.codes">
598<t> 
599   The status codes listed below are defined in <xref target="status.codes"/>
600   of this specification, &p4-status-codes;, &p5-status-codes;, and &p7-status-codes;.
601   The reason phrases listed here are only recommendations &mdash; they can be
602   replaced by local equivalents without affecting the protocol.
603</t>
604<texttable align="left">
605  <ttcol>Status-Code</ttcol>
606  <ttcol>Reason-Phrase</ttcol>
607  <ttcol>Defined in...</ttcol>
608 
609  <c>100</c> <c>Continue</c> <c><xref target="status.100"/></c>
610  <c>101</c> <c>Switching Protocols</c> <c><xref target="status.101"/></c>
611
612  <c>200</c> <c>OK</c> <c><xref target="status.200"/></c>
613  <c>201</c> <c>Created</c> <c><xref target="status.201"/></c>
614  <c>202</c> <c>Accepted</c> <c><xref target="status.202"/></c>
615  <c>203</c> <c>Non-Authoritative Information</c> <c><xref target="status.203"/></c>
616  <c>204</c> <c>No Content</c> <c><xref target="status.204"/></c>
617  <c>205</c> <c>Reset Content</c> <c><xref target="status.205"/></c>
618  <c>206</c> <c>Partial Content</c> <c>&status-206;</c>
619
620  <c>300</c> <c>Multiple Choices</c> <c><xref target="status.300"/></c>
621  <c>301</c> <c>Moved Permanently</c> <c><xref target="status.301"/></c>
622  <c>302</c> <c>Found</c> <c><xref target="status.302"/></c>
623  <c>303</c> <c>See Other</c> <c><xref target="status.303"/></c>
624  <c>304</c> <c>Not Modified</c> <c>&status-304;</c>
625  <c>305</c> <c>Use Proxy</c> <c><xref target="status.305"/></c>
626  <c>307</c> <c>Temporary Redirect</c> <c><xref target="status.307"/></c>
627
628  <c>400</c> <c>Bad Request</c> <c><xref target="status.400"/></c>
629  <c>401</c> <c>Unauthorized</c> <c>&status-401;</c>
630  <c>402</c> <c>Payment Required</c> <c><xref target="status.402"/></c>
631  <c>403</c> <c>Forbidden</c> <c><xref target="status.403"/></c>
632  <c>404</c> <c>Not Found</c> <c><xref target="status.404"/></c>
633  <c>405</c> <c>Method Not Allowed</c> <c><xref target="status.405"/></c>
634  <c>406</c> <c>Not Acceptable</c> <c><xref target="status.406"/></c>
635  <c>407</c> <c>Proxy Authentication Required</c> <c>&status-407;</c>
636  <c>408</c> <c>Request Time-out</c> <c><xref target="status.408"/></c>
637  <c>409</c> <c>Conflict</c> <c><xref target="status.409"/></c>
638  <c>410</c> <c>Gone</c> <c><xref target="status.410"/></c>
639  <c>411</c> <c>Length Required</c> <c><xref target="status.411"/></c>
640  <c>412</c> <c>Precondition Failed</c> <c>&status-412;</c>
641  <c>413</c> <c>Request Entity Too Large</c> <c><xref target="status.413"/></c>
642  <c>414</c> <c>URI Too Long</c> <c><xref target="status.414"/></c>
643  <c>415</c> <c>Unsupported Media Type</c> <c><xref target="status.415"/></c>
644  <c>416</c> <c>Requested range not satisfiable</c> <c>&status-416;</c>
645  <c>417</c> <c>Expectation Failed</c> <c><xref target="status.417"/></c>
646  <c>426</c> <c>Upgrade Required</c> <c><xref target="status.426"/></c>
647
648  <c>500</c> <c>Internal Server Error</c> <c><xref target="status.500"/></c>
649  <c>501</c> <c>Not Implemented</c> <c><xref target="status.501"/></c>
650  <c>502</c> <c>Bad Gateway</c> <c><xref target="status.502"/></c>
651  <c>503</c> <c>Service Unavailable</c> <c><xref target="status.503"/></c>
652  <c>504</c> <c>Gateway Time-out</c> <c><xref target="status.504"/></c>
653  <c>505</c> <c>HTTP Version not supported</c> <c><xref target="status.505"/></c>
654</texttable>
655<t>
656   Note that this list is not exhaustive &mdash; it does not include
657   extension status codes defined in other specifications.
658</t>
659</section>
660
661<section title="Status Code Registry" anchor="status.code.registry">
662<t>
663  The HTTP Status Code Registry defines the name space for the Status-Code
664  token in the Status-Line of an HTTP response.
665</t>
666<t>
667  Values to be added to this name space are subject to IETF review
668  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
669</t>
670<t>
671  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
672</t>
673
674<section title="Considerations for New Status Codes" anchor="considerations.for.new.status.codes">
675<t>
676   When it is necessary to express new semantics for a HTTP response that
677   aren't specific to a single application or media type, and currently defined
678   status codes are inadequate, a new status code can be registered.
679</t>
680<t>
681   HTTP status codes are generic; that is, they are potentially applicable to
682   any resource, not just one particular media type, "type" of resource, or
683   application. As such, it is preferred that new HTTP status codes be
684   registered in a document that isn't specific to a single application, so
685   that this is clear.
686</t>
687<t>
688   Definitions of new HTTP status codes typically explain the request
689   conditions that produce a response containing the status code (e.g.,
690   combinations of request headers and/or method(s)), along with any
691   interactions with response headers (e.g., those that are required, those
692   that modify the semantics of the response).
693</t>
694<t>
695   New HTTP status codes are required to fall under one of the categories
696   defined in <xref target="status.codes"/>. To allow existing parsers to
697   properly handle them, new status codes cannot disallow a response body,
698   although they can mandate a zero-length response body. They can require the
699   presence of one or more particular HTTP response header(s).
700</t>
701<t>
702   Likewise, their definitions can specify that caches are allowed to use
703   heuristics to determine their freshness (see &caching;; by default, it is
704   not allowed), and can define how to determine the resource which they
705   carry a representation for (see <xref
706   target="identifying.response.associated.with.representation"/>; by default,
707   it is anonymous).
708</t>
709</section>
710
711</section>
712
713</section>
714
715<section title="Response Header Fields" anchor="response.header.fields">
716  <x:anchor-alias value="response-header"/>
717<t>
718   The response header fields allow the server to pass additional
719   information about the response which cannot be placed in the Status-Line.
720   These header fields give information about the server and about
721   further access to the target resource (&effective-request-uri;).
722</t>
723<texttable align="left">
724  <ttcol>Header Field Name</ttcol><ttcol>Defined in...</ttcol>
725
726  <c>Accept-Ranges</c> <c>&header-accept-ranges;</c>
727  <c>Age</c> <c>&header-age;</c>
728  <c>Allow</c> <c><xref target="header.allow"/></c>
729  <c>ETag</c> <c>&header-etag;</c>
730  <c>Location</c> <c><xref target="header.location"/></c>
731  <c>Proxy-Authenticate</c> <c>&header-proxy-authenticate;</c>
732  <c>Retry-After</c> <c><xref target="header.retry-after"/></c>
733  <c>Server</c> <c><xref target="header.server"/></c>
734  <c>Vary</c> <c>&header-vary;</c>
735  <c>WWW-Authenticate</c> <c>&header-www-authenticate;</c>
736</texttable>
737</section>
738
739<section title="Representation" anchor="representation">
740<t>
741   Request and Response messages &MAY; transfer a representation if not otherwise
742   restricted by the request method or response status code. A representation
743   consists of metadata (representation header fields) and data (representation
744   body).  When a complete or partial representation is enclosed in an HTTP message,
745   it is referred to as the payload of the message. HTTP representations
746   are defined in &payload;.
747</t>
748<t>
749   A representation body is only present in a message when a message-body is
750   present, as described in &message-body;. The representation body is obtained
751   from the message-body by decoding any Transfer-Encoding that might
752   have been applied to ensure safe and proper transfer of the message.
753</t>
754
755<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
756<t>
757   It is sometimes necessary to determine an identifier for the resource
758   associated with a representation.
759</t>
760<t>
761   An HTTP request representation, when present, is always associated with an
762   anonymous (i.e., unidentified) resource.
763</t>
764<t>
765   In the common case, an HTTP response is a representation of the target
766   resource (see &effective-request-uri;). However, this is not always the
767   case. To determine the URI of the resource a response is associated with,
768   the following rules are used (with the first applicable one being selected):
769</t>
770<t><list style="numbers">
771   <t>If the response status code is 200 or 203 and the request method was GET,
772   the response payload is a representation of the target resource.</t>
773   <t>If the response status code is 204, 206, or 304 and the request method was GET
774   or HEAD, the response payload is a partial representation of the target
775   resource (see &combining-responses;).</t>
776   <t>If the response has a Content-Location header field, and that URI is the same
777   as the effective request URI, the response payload is a representation of the
778   target resource.</t>
779   <t>If the response has a Content-Location header field, and that URI is not the
780   same as the effective request URI, then the response asserts that its
781   payload is a representation of the resource identified by the
782   Content-Location URI. However, such an assertion cannot be trusted unless
783   it can be verified by other means (not defined by HTTP).</t>
784   <t>Otherwise, the response is a representation of an anonymous (i.e.,
785   unidentified) resource.</t>
786</list></t>
787<t>
788  <cref anchor="TODO-req-uri">
789   The comparison function is going to have to be defined somewhere,
790   because we already need to compare URIs for things like cache invalidation.</cref>
791</t>
792</section>
793
794</section>
795
796
797<section title="Method Definitions" anchor="method.definitions">
798<t>
799   The set of common request methods for HTTP/1.1 is defined below. Although
800   this set can be expanded, additional methods cannot be assumed to
801   share the same semantics for separately extended clients and servers.
802</t>
803
804<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
805
806<section title="Safe Methods" anchor="safe.methods">
807<iref item="Safe Methods" primary="true"/>
808<t>
809   Implementors need to be aware that the software represents the user in
810   their interactions over the Internet, and need to allow
811   the user to be aware of any actions they take which might have an
812   unexpected significance to themselves or others.
813</t>
814<t>
815   In particular, the convention has been established that the GET, HEAD,
816   OPTIONS, and TRACE request methods &SHOULD-NOT; have the significance
817   of taking an action other than retrieval. These request methods ought
818   to be considered "<x:dfn anchor="safe">safe</x:dfn>".
819   This allows user agents to represent other methods, such as POST, PUT
820   and DELETE, in a special way, so that the user is made aware of the
821   fact that a possibly unsafe action is being requested.
822</t>
823<t>
824   Naturally, it is not possible to ensure that the server does not
825   generate side-effects as a result of performing a GET request; in
826   fact, some dynamic resources consider that a feature. The important
827   distinction here is that the user did not request the side-effects,
828   so therefore cannot be held accountable for them.
829</t>
830</section>
831
832<section title="Idempotent Methods" anchor="idempotent.methods">
833<iref item="Idempotent Methods" primary="true"/>
834<t>
835   Request methods can also have the property of "idempotence" in that,
836   aside from error or expiration issues, the intended effect of multiple
837   identical requests is the same as for a single request.
838   PUT, DELETE, and all safe request methods are idempotent.
839   It is important to note that idempotence refers only to changes
840   requested by the client: a server is free to change its state due
841   to multiple requests for the purpose of tracking those requests,
842   versioning of results, etc.
843</t>
844</section>
845</section>
846
847<section title="OPTIONS" anchor="OPTIONS">
848  <rdf:Description>
849    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
850  </rdf:Description>
851  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
852  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
853<t>
854   The OPTIONS method requests information about the
855   communication options available on the request/response chain
856   identified by the effective request URI. This method allows a client to
857   determine the options and/or requirements associated with a resource,
858   or the capabilities of a server, without implying a resource action
859   or initiating a resource retrieval.
860</t>
861<t>
862   Responses to the OPTIONS method are not cacheable.
863</t>
864<t>
865   If the OPTIONS request includes a message-body (as indicated by the
866   presence of Content-Length or Transfer-Encoding), then the media type
867   &MUST; be indicated by a Content-Type field. Although this
868   specification does not define any use for such a body, future
869   extensions to HTTP might use the OPTIONS body to make more detailed
870   queries on the server.
871</t>
872<t>
873   If the request-target is an asterisk ("*"), the OPTIONS request is
874   intended to apply to the server in general rather than to a specific
875   resource. Since a server's communication options typically depend on
876   the resource, the "*" request is only useful as a "ping" or "no-op"
877   type of method; it does nothing beyond allowing the client to test
878   the capabilities of the server. For example, this can be used to test
879   a proxy for HTTP/1.1 compliance (or lack thereof).
880</t>
881<t>
882   If the request-target is not an asterisk, the OPTIONS request applies
883   only to the options that are available when communicating with that
884   resource.
885</t>
886<t>
887   A 200 response &SHOULD; include any header fields that indicate
888   optional features implemented by the server and applicable to that
889   resource (e.g., Allow), possibly including extensions not defined by
890   this specification. The response body, if any, &SHOULD; also include
891   information about the communication options. The format for such a
892   body is not defined by this specification, but might be defined by
893   future extensions to HTTP. Content negotiation &MAY; be used to select
894   the appropriate response format. If no response body is included, the
895   response &MUST; include a Content-Length field with a field-value of
896   "0".
897</t>
898<t>
899   The Max-Forwards header field &MAY; be used to target a
900   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
901   If no Max-Forwards field is present in the request, then the forwarded
902   request &MUST-NOT; include a Max-Forwards field.
903</t>
904</section>
905
906<section title="GET" anchor="GET">
907  <rdf:Description>
908    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
909  </rdf:Description>
910  <iref primary="true" item="GET method" x:for-anchor=""/>
911  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
912<t>
913   The GET method requests transfer of a current representation of
914   the target resource.
915</t>
916<t>   
917   If the target resource is a data-producing process, it is the
918   produced data which shall be returned as the representation in the response and not
919   the source text of the process, unless that text happens to be the output of
920   the process.
921</t>
922<t>
923   The semantics of the GET method change to a "conditional GET" if the
924   request message includes an If-Modified-Since, If-Unmodified-Since,
925   If-Match, If-None-Match, or If-Range header field. A conditional GET
926   requests that the representation be transferred only under the
927   circumstances described by the conditional header field(s). The
928   conditional GET request is intended to reduce unnecessary network
929   usage by allowing cached representations to be refreshed without requiring
930   multiple requests or transferring data already held by the client.
931</t>
932<t>
933   The semantics of the GET method change to a "partial GET" if the
934   request message includes a Range header field. A partial GET requests
935   that only part of the representation be transferred, as described in &header-range;.
936   The partial GET request is intended to reduce unnecessary
937   network usage by allowing partially-retrieved representations to be
938   completed without transferring data already held by the client.
939</t>
940<t>
941   The response to a GET request is cacheable and &MAY; be used to satisfy
942   subsequent GET and HEAD requests (see &caching;).
943</t>
944<t>
945   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
946</t>
947</section>
948
949<section title="HEAD" anchor="HEAD">
950  <rdf:Description>
951    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
952  </rdf:Description>
953  <iref primary="true" item="HEAD method" x:for-anchor=""/>
954  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
955<t>
956   The HEAD method is identical to GET except that the server &MUST-NOT;
957   return a message-body in the response. The metadata contained
958   in the HTTP header fields in response to a HEAD request &SHOULD; be identical
959   to the information sent in response to a GET request. This method can
960   be used for obtaining metadata about the representation implied by the
961   request without transferring the representation body. This method is
962   often used for testing hypertext links for validity, accessibility,
963   and recent modification.
964</t>
965<t>
966   The response to a HEAD request is cacheable and &MAY; be used to satisfy
967   a subsequent HEAD request; see &caching;. It also &MAY; be used to update a previously cached
968   representation from that resource; if the new field values
969   indicate that the cached representation differs from the current representation (as
970   would be indicated by a change in Content-Length, Content-MD5, ETag
971   or Last-Modified), then the cache &MUST; treat the cache entry as
972   stale.
973</t>
974</section>
975
976<section title="POST" anchor="POST">
977  <iref primary="true" item="POST method" x:for-anchor=""/>
978  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
979<t>
980   The POST method requests that the origin server accept the
981   representation enclosed in the request as data to be processed by the
982   target resource. POST is designed to allow a uniform method to cover the
983   following functions:
984  <list style="symbols">
985    <t>
986      Annotation of existing resources;
987    </t>
988    <t>
989        Posting a message to a bulletin board, newsgroup, mailing list,
990        or similar group of articles;
991    </t>
992    <t>
993        Providing a block of data, such as the result of submitting a
994        form, to a data-handling process;
995    </t>
996    <t>
997        Extending a database through an append operation.
998    </t>
999  </list>
1000</t>
1001<t>
1002   The actual function performed by the POST method is determined by the
1003   server and is usually dependent on the effective request URI.
1004</t>
1005<t>
1006   The action performed by the POST method might not result in a
1007   resource that can be identified by a URI. In this case, either 200
1008   (OK) or 204 (No Content) is the appropriate response status code,
1009   depending on whether or not the response includes a representation that
1010   describes the result.
1011</t>
1012<t>
1013   If a resource has been created on the origin server, the response
1014   &SHOULD; be 201 (Created) and contain a representation which describes the
1015   status of the request and refers to the new resource, and a Location
1016   header field (see <xref target="header.location"/>).
1017</t>
1018<t>
1019   Responses to POST requests are only cacheable when they
1020   include explicit freshness information (see &p6-explicit;). A
1021   cached POST response with a Content-Location header field
1022   (see &header-content-location;) whose value is the effective
1023   Request URI &MAY; be used to satisfy subsequent GET and HEAD requests.
1024</t>
1025<t>
1026   Note that POST caching is not widely implemented.
1027   However, the 303 (See Other) response can be used to direct the
1028   user agent to retrieve a cacheable resource.
1029</t>
1030</section>
1031
1032<section title="PUT" anchor="PUT">
1033  <iref primary="true" item="PUT method" x:for-anchor=""/>
1034  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
1035<t>
1036   The PUT method requests that the state of the target resource
1037   be created or replaced with the state defined by the representation
1038   enclosed in the request message payload.  A successful PUT of a given
1039   representation would suggest that a subsequent GET on that same target
1040   resource will result in an equivalent representation being returned in
1041   a 200 (OK) response.  However, there is no guarantee that such a state
1042   change will be observable, since the target resource might be acted
1043   upon by other user agents in parallel, or might be subject to dynamic
1044   processing by the origin server, before any subsequent GET is received.
1045   A successful response only implies that the user agent's intent was
1046   achieved at the time of its processing by the origin server.
1047</t>
1048<t>   
1049   If the target resource does not have a current representation and
1050   the PUT successfully creates one, then the origin server &MUST; inform
1051   the user agent by sending a 201 (Created) response.  If the target
1052   resource does have a current representation and that representation is
1053   successfully modified in accordance with the state of the enclosed
1054   representation, then either a 200 (OK) or 204 (No Content) response
1055   &SHOULD; be sent to indicate successful completion of the request.
1056</t>
1057<t>
1058   Unrecognized header fields &SHOULD; be ignored (i.e., not saved
1059   as part of the resource state).
1060</t>
1061<t>
1062   An origin server &SHOULD; verify that the PUT representation is
1063   consistent with any constraints which the server has for the target
1064   resource that cannot or will not be changed by the PUT.  This is
1065   particularly important when the origin server uses internal
1066   configuration information related to the URI in order to set the
1067   values for representation metadata on GET responses.  When a PUT
1068   representation is inconsistent with the target resource, the origin
1069   server &SHOULD; either make them consistent, by transforming the
1070   representation or changing the resource configuration, or respond
1071   with a 409 (Conflict) status code and sufficient information
1072   to explain why the representation is unsuitable.
1073</t>
1074<t>
1075   For example, if the target resource is configured to always have a
1076   Content-Type of "text/html" and the representation being PUT has a
1077   Content-Type of "image/jpeg", then the origin server &SHOULD; do one of:
1078   (a) reconfigure the target resource to reflect the new media type;
1079   (b) transform the PUT representation to a format consistent with that
1080   of the resource before saving it as the new resource state; or,
1081   (c) reject the request with a 409 response indicating that the target
1082   resource is limited to "text/html", perhaps including a link to a
1083   different resource that would be a suitable target for the new
1084   representation.
1085</t>
1086<t>
1087   HTTP does not define exactly how a PUT method affects the state
1088   of an origin server beyond what can be expressed by the intent of
1089   the user agent request and the semantics of the origin server response.
1090   It does not define what a resource might be, in any sense of that
1091   word, beyond the interface provided via HTTP.  It does not define
1092   how resource state is "stored", nor how such storage might change
1093   as a result of a change in resource state, nor how the origin server
1094   translates resource state into representations.  Generally speaking,
1095   all implementation details behind the resource interface are
1096   intentionally hidden by the server.
1097</t>
1098<t>
1099   The fundamental difference between the POST and PUT methods is
1100   highlighted by the different intent for the target resource.
1101   The target resource in a POST request is intended to handle the
1102   enclosed representation as a data-accepting process, such as for
1103   a gateway to some other protocol or a document that accepts annotations.
1104   In contrast, the target resource in a PUT request is intended to
1105   take the enclosed representation as a new or replacement value.
1106   Hence, the intent of PUT is idempotent and visible to intermediaries,
1107   even though the exact effect is only known by the origin server.
1108</t>
1109<t>
1110   Proper interpretation of a PUT request presumes that the user agent
1111   knows what target resource is desired.  A service that is intended
1112   to select a proper URI on behalf of the client, after receiving
1113   a state-changing request, &SHOULD; be implemented using the POST
1114   method rather than PUT.  If the origin server will not make the
1115   requested PUT state change to the target resource and instead
1116   wishes to have it applied to a different resource, such as when the
1117   resource has been moved to a different URI, then the origin server
1118   &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
1119   then make its own decision regarding whether or not to redirect the
1120   request.
1121</t>
1122<t>
1123   A PUT request applied to the target resource &MAY; have side-effects
1124   on other resources.  For example, an article might have a URI for
1125   identifying "the current version" (a resource) which is separate
1126   from the URIs identifying each particular version (different
1127   resources that at one point shared the same state as the current version
1128   resource).  A successful PUT request on "the current version" URI might
1129   therefore create a new version resource in addition to changing the
1130   state of the target resource, and might also cause links to be added
1131   between the related resources.
1132</t>
1133<t>
1134   An origin server &SHOULD; reject any PUT request that contains a
1135   Content-Range header field, since it might be misinterpreted as
1136   partial content (or might be partial content that is being mistakenly
1137   PUT as a full representation).  Partial content updates are
1138   possible by targeting a separately identified resource with state
1139   that overlaps a portion of the larger resource, or by using a
1140   different method that has been specifically defined for partial
1141   updates (for example, the PATCH method defined in
1142   <xref target="RFC5789"/>).
1143</t>
1144<t>
1145   Responses to the PUT method are not cacheable. If a PUT request passes
1146   through a cache that has one or more stored responses for the effective
1147   request URI, those stored responses will be invalidated (see
1148   &p6-invalid;).
1149</t>
1150</section>
1151
1152<section title="DELETE" anchor="DELETE">
1153  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1154  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1155<t>
1156   The DELETE method requests that the origin server delete the target
1157   resource. This method &MAY; be overridden by
1158   human intervention (or other means) on the origin server. The client cannot
1159   be guaranteed that the operation has been carried out, even if the
1160   status code returned from the origin server indicates that the action
1161   has been completed successfully. However, the server &SHOULD-NOT; 
1162   indicate success unless, at the time the response is given, it
1163   intends to delete the resource or move it to an inaccessible
1164   location.
1165</t>
1166<t>
1167   A successful response &SHOULD; be 200 (OK) if the response includes an
1168   representation describing the status, 202 (Accepted) if the action has not
1169   yet been enacted, or 204 (No Content) if the action has been enacted
1170   but the response does not include a representation.
1171</t>
1172<t>
1173   Responses to the DELETE method are not cacheable. If a DELETE request
1174   passes through a cache that has one or more stored responses for the
1175   effective request URI, those stored responses will be invalidated (see
1176   &p6-invalid;).
1177</t>
1178</section>
1179
1180<section title="TRACE" anchor="TRACE">
1181  <rdf:Description>
1182    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1183  </rdf:Description>
1184  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1185  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1186<t>
1187   The TRACE method requests a remote, application-layer loop-back
1188   of the request message. The final recipient of the request
1189   &SHOULD; reflect the message received back to the client as the
1190   message-body of a 200 (OK) response. The final recipient is either the
1191   origin server or the first proxy or gateway to receive a Max-Forwards
1192   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1193   A TRACE request &MUST-NOT; include a message-body.
1194</t>
1195<t>
1196   TRACE allows the client to see what is being received at the other
1197   end of the request chain and use that data for testing or diagnostic
1198   information. The value of the Via header field (&header-via;) is of
1199   particular interest, since it acts as a trace of the request chain.
1200   Use of the Max-Forwards header field allows the client to limit the
1201   length of the request chain, which is useful for testing a chain of
1202   proxies forwarding messages in an infinite loop.
1203</t>
1204<t>
1205   If the request is valid, the response &SHOULD; have a Content-Type of
1206   "message/http" (see &media-type-message-http;) and contain a message-body
1207   that encloses a copy of the entire request message.
1208   Responses to the TRACE method are not cacheable.
1209</t>
1210</section>
1211
1212<section title="CONNECT" anchor="CONNECT">
1213  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1214  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1215<t>
1216   The CONNECT method requests that the proxy establish a tunnel
1217   to the request-target and then restrict its behavior to blind
1218   forwarding of packets until the connection is closed.
1219</t>
1220<t>
1221   When using CONNECT, the request-target &MUST; use the authority form
1222   (&request-target;); i.e., the request-target consists of only the
1223   host name and port number of the tunnel destination, separated by a colon.
1224   For example,
1225</t>
1226<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1227CONNECT server.example.com:80 HTTP/1.1
1228Host: server.example.com:80
1229
1230</artwork></figure>
1231<t>
1232   Other HTTP mechanisms can be used normally with the CONNECT method &mdash;
1233   except end-to-end protocol Upgrade requests, since the
1234   tunnel must be established first.
1235</t>
1236<t>
1237   For example, proxy authentication might be used to establish the
1238   authority to create a tunnel:
1239</t>
1240<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1241CONNECT server.example.com:80 HTTP/1.1
1242Host: server.example.com:80
1243Proxy-Authorization: basic aGVsbG86d29ybGQ=
1244
1245</artwork></figure>
1246<t>
1247   Like any other pipelined HTTP/1.1 request, data to be tunnel may be
1248   sent immediately after the blank line. The usual caveats also apply:
1249   data may be discarded if the eventual response is negative, and the
1250   connection may be reset with no response if more than one TCP segment
1251   is outstanding.
1252</t>
1253
1254<section title="Establishing a Tunnel with CONNECT">
1255<t>
1256   Any successful (2xx) response to a CONNECT request indicates that the
1257   proxy has established a connection to the requested host and port,
1258   and has switched to tunneling the current connection to that server
1259   connection.
1260</t>
1261<t>
1262   It may be the case that the proxy itself can only reach the requested
1263   origin server through another proxy.  In this case, the first proxy
1264   &SHOULD; make a CONNECT request of that next proxy, requesting a tunnel
1265   to the authority.  A proxy &MUST-NOT; respond with any 2xx status code
1266   unless it has either a direct or tunnel connection established to the
1267   authority.
1268</t>
1269<t>
1270   An origin server which receives a CONNECT request for itself &MAY;
1271   respond with a 2xx status code to indicate that a connection is
1272   established.
1273</t>
1274<t>
1275   If at any point either one of the peers gets disconnected, any
1276   outstanding data that came from that peer will be passed to the other
1277   one, and after that also the other connection will be terminated by
1278   the proxy. If there is outstanding data to that peer undelivered,
1279   that data will be discarded.
1280</t>
1281
1282</section>
1283</section>
1284</section>
1285
1286
1287<section title="Status Code Definitions" anchor="status.codes">
1288<t>
1289   Each Status-Code is described below, including any metadata required
1290   in the response.
1291</t>
1292
1293<section title="Informational 1xx" anchor="status.1xx">
1294<t>
1295   This class of status code indicates a provisional response,
1296   consisting only of the Status-Line and optional header fields, and is
1297   terminated by an empty line. There are no required header fields for this
1298   class of status code. Since HTTP/1.0 did not define any 1xx status
1299   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1300   except under experimental conditions.
1301</t>
1302<t>
1303   A client &MUST; be prepared to accept one or more 1xx status responses
1304   prior to a regular response, even if the client does not expect a 100
1305   (Continue) status message. Unexpected 1xx status responses &MAY; be
1306   ignored by a user agent.
1307</t>
1308<t>
1309   Proxies &MUST; forward 1xx responses, unless the connection between the
1310   proxy and its client has been closed, or unless the proxy itself
1311   requested the generation of the 1xx response. (For example, if a
1312   proxy adds a "Expect: 100-continue" field when it forwards a request,
1313   then it need not forward the corresponding 100 (Continue)
1314   response(s).)
1315</t>
1316
1317<section title="100 Continue" anchor="status.100">
1318  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1319  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1320<t>
1321   The client &SHOULD; continue with its request. This interim response is
1322   used to inform the client that the initial part of the request has
1323   been received and has not yet been rejected by the server. The client
1324   &SHOULD; continue by sending the remainder of the request or, if the
1325   request has already been completed, ignore this response. The server
1326   &MUST; send a final response after the request has been completed. See
1327   &use100; for detailed discussion of the use and handling of this
1328   status code.
1329</t>
1330</section>
1331
1332<section title="101 Switching Protocols" anchor="status.101">
1333  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1334  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1335<t>
1336   The server understands and is willing to comply with the client's
1337   request, via the Upgrade message header field (&header-upgrade;), for a
1338   change in the application protocol being used on this connection. The
1339   server will switch protocols to those defined by the response's
1340   Upgrade header field immediately after the empty line which
1341   terminates the 101 response.
1342</t>
1343<t>
1344   The protocol &SHOULD; be switched only when it is advantageous to do
1345   so. For example, switching to a newer version of HTTP is advantageous
1346   over older versions, and switching to a real-time, synchronous
1347   protocol might be advantageous when delivering resources that use
1348   such features.
1349</t>
1350</section>
1351</section>
1352
1353<section title="Successful 2xx" anchor="status.2xx">
1354<t>
1355   This class of status code indicates that the client's request was
1356   successfully received, understood, and accepted.
1357</t>
1358
1359<section title="200 OK" anchor="status.200">
1360  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1361  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1362<t>
1363   The request has succeeded. The payload returned with the response
1364   is dependent on the method used in the request, for example:
1365  <list style="hanging">
1366    <t hangText="GET">
1367          a representation of the target resource is sent in the response;
1368    </t>
1369    <t hangText="HEAD">
1370          the same representation as GET, except without the message-body;
1371    </t>
1372    <t hangText="POST">
1373      a representation describing or containing the result of the action;
1374    </t>
1375    <t hangText="TRACE">
1376      a representation containing the request message as received by the
1377      end server.
1378    </t>
1379  </list>
1380</t>
1381<t>
1382   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1383   freshness for 200 responses.
1384</t>
1385</section>
1386
1387<section title="201 Created" anchor="status.201">
1388  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1389  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1390<t>
1391   The request has been fulfilled and has resulted in a new resource being
1392   created. The newly created resource can be referenced by the URI(s)
1393   returned in the payload of the response, with the most specific URI
1394   for the resource given by a Location header field. The response
1395   &SHOULD; include a payload containing a list of resource
1396   characteristics and location(s) from which the user or user agent can
1397   choose the one most appropriate. The payload format is specified by
1398   the media type given in the Content-Type header field. The origin
1399   server &MUST; create the resource before returning the 201 status code.
1400   If the action cannot be carried out immediately, the server &SHOULD;
1401   respond with 202 (Accepted) response instead.
1402</t>
1403<t>
1404   A 201 response &MAY; contain an ETag response header field indicating
1405   the current value of the entity-tag for the representation of the resource
1406   just created (see &header-etag;).
1407</t>
1408</section>
1409
1410<section title="202 Accepted" anchor="status.202">
1411  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1412  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1413<t>
1414   The request has been accepted for processing, but the processing has
1415   not been completed.  The request might or might not eventually be
1416   acted upon, as it might be disallowed when processing actually takes
1417   place. There is no facility for re-sending a status code from an
1418   asynchronous operation such as this.
1419</t>
1420<t>
1421   The 202 response is intentionally non-committal. Its purpose is to
1422   allow a server to accept a request for some other process (perhaps a
1423   batch-oriented process that is only run once per day) without
1424   requiring that the user agent's connection to the server persist
1425   until the process is completed. The representation returned with this
1426   response &SHOULD; include an indication of the request's current status
1427   and either a pointer to a status monitor or some estimate of when the
1428   user can expect the request to be fulfilled.
1429</t>
1430</section>
1431
1432<section title="203 Non-Authoritative Information" anchor="status.203">
1433  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1434  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1435<t>
1436   The returned metadata in the header fields is not the
1437   definitive set as available from the origin server, but is gathered
1438   from a local or a third-party copy. The set presented &MAY; be a subset
1439   or superset of the original version. For example, including local
1440   annotation information about the resource might result in a superset
1441   of the metadata known by the origin server. Use of this
1442   response code is not required and is only appropriate when the
1443   response would otherwise be 200 (OK).
1444</t>
1445<t>
1446   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1447   freshness for 203 responses.
1448</t>
1449
1450</section>
1451
1452<section title="204 No Content" anchor="status.204">
1453  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1454  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1455<t>
1456   The server has successfully fulfilled the request, but there is no
1457   additional content to return in the response payload body.  The
1458   resource metadata and representation metadata in the response message's
1459   header fields refer to the target resource
1460   and its current representation, respectively, after the requested action.
1461   For example, if a 204 status code is received in response to a PUT
1462   and the response contains an ETag header field, then the value of
1463   that field is the current entity-tag for the representation that
1464   was successfully PUT.
1465</t>
1466<t>
1467   If the client is a user agent, it &SHOULD-NOT; change its document view
1468   from that which caused the request to be sent. This response is
1469   primarily intended to allow input for actions to take place without
1470   causing a change to the user agent's active document view, although
1471   any new or updated metadata &SHOULD; be applied to the document
1472   currently in the user agent's active view.
1473</t>
1474<t>
1475   The 204 response &MUST-NOT; include a message-body, and thus is always
1476   terminated by the first empty line after the header fields.
1477</t>
1478</section>
1479
1480<section title="205 Reset Content" anchor="status.205">
1481  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1482  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1483<t>
1484   The server has fulfilled the request and the user agent &SHOULD; reset
1485   the document view which caused the request to be sent. This response
1486   is primarily intended to allow input for actions to take place via
1487   user input, followed by a clearing of the form in which the input is
1488   given so that the user can easily initiate another input action.
1489</t>
1490<t>   
1491   The message-body included with the response &MUST; be empty. Note that
1492   receivers still need to parse the response according to the algorithm defined
1493   in &message-body;.
1494</t>
1495</section>
1496
1497<section title="206 Partial Content" anchor="status.206">
1498  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1499  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1500  <rdf:Description>
1501    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1502  </rdf:Description>
1503<t>
1504   The server has fulfilled the partial GET request for the resource
1505   and the enclosed payload is a partial representation as defined in &status-206;.
1506</t>
1507<t>
1508   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1509   freshness for 206 responses.
1510</t>
1511</section>
1512</section>
1513
1514<section title="Redirection 3xx" anchor="status.3xx">
1515<t>
1516   This class of status code indicates that further action needs to be
1517   taken by the user agent in order to fulfill the request.  The action
1518   required &MAY; be carried out by the user agent without interaction
1519   with the user if and only if the method used in the second request is
1520   known to be "safe", as defined in <xref target="safe.methods"/>.
1521   A client &SHOULD; detect infinite redirection loops, since such loops
1522   generate network traffic for each redirection.
1523</t>
1524<x:note>
1525  <t>
1526    <x:h>Note:</x:h> An earlier version of this specification recommended a
1527    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1528    Content developers need to be aware that some clients might
1529    implement such a fixed limitation.
1530  </t>
1531</x:note>
1532
1533<section title="300 Multiple Choices" anchor="status.300">
1534  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1535  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1536<t>
1537   The target resource has more than one
1538   representation, each with its own specific location, and agent-driven
1539   negotiation information (&content-negotiation;) is being provided so that
1540   the user (or user agent) can select a preferred representation by
1541   redirecting its request to that location.
1542</t>
1543<t>
1544   Unless it was a HEAD request, the response &SHOULD; include a representation
1545   containing a list of representation metadata and location(s) from
1546   which the user or user agent can choose the one most appropriate. The
1547   data format is specified by the media type given in the Content-Type
1548   header field. Depending upon the format and the capabilities of
1549   the user agent, selection of the most appropriate choice &MAY; be
1550   performed automatically. However, this specification does not define
1551   any standard for such automatic selection.
1552</t>
1553<t>
1554   If the server has a preferred choice of representation, it &SHOULD;
1555   include the specific URI for that representation in the Location
1556   field; user agents &MAY; use the Location field value for automatic
1557   redirection.
1558</t>
1559<t>
1560   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1561   freshness for 300 responses.
1562</t>
1563
1564</section>
1565
1566<section title="301 Moved Permanently" anchor="status.301">
1567  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1568  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1569<t>
1570   The target resource has been assigned a new permanent URI and any
1571   future references to this resource &SHOULD; use one of the returned
1572   URIs.  Clients with link editing capabilities ought to automatically
1573   re-link references to the effective request URI to one or more of the new
1574   references returned by the server, where possible.
1575</t>
1576<t>
1577   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1578   freshness for 301 responses.
1579</t>
1580<t>
1581   The new permanent URI &SHOULD; be given by the Location field in the
1582   response. Unless the request method was HEAD, the representation of the
1583   response &SHOULD; contain a short hypertext note with a hyperlink to
1584   the new URI(s).
1585</t>
1586<t>
1587   If the 301 status code is received in response to a request method
1588   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1589   then the request &MAY; be automatically redirected by the user agent without
1590   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1591   request unless it can be confirmed by the user, since this might
1592   change the conditions under which the request was issued.
1593</t>
1594<x:note>
1595  <t>
1596    <x:h>Note:</x:h> When automatically redirecting a POST request after
1597    receiving a 301 status code, some existing HTTP/1.0 user agents
1598    will erroneously change it into a GET request.
1599  </t>
1600</x:note>
1601</section>
1602
1603<section title="302 Found" anchor="status.302">
1604  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1605  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1606<t>
1607   The target resource resides temporarily under a different URI.
1608   Since the redirection might be altered on occasion, the client &SHOULD;
1609   continue to use the effective request URI for future requests.
1610</t>
1611<t>
1612   The temporary URI &SHOULD; be given by the Location field in the
1613   response. Unless the request method was HEAD, the representation of the
1614   response &SHOULD; contain a short hypertext note with a hyperlink to
1615   the new URI(s).
1616</t>
1617<t>
1618   If the 302 status code is received in response to a request method
1619   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1620   then the request &MAY; be automatically redirected by the user agent without
1621   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1622   request unless it can be confirmed by the user, since this might
1623   change the conditions under which the request was issued.
1624</t>
1625<x:note>
1626  <t>
1627    <x:h>Note:</x:h> HTTP/1.0 (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>)
1628    and the first version of HTTP/1.1 (<xref target="RFC2068" x:fmt="," x:sec ="10.3.3"/>)
1629    specify that the client is not allowed to change the method on the
1630    redirected request.  However, most existing user agent implementations
1631    treat 302 as if it were a 303 response, performing a GET on the Location
1632    field-value regardless of the original request method. Therefore, a
1633    previous version of this specification
1634    (<xref target="RFC2616" x:fmt="," x:sec="10.3.3"/>) has added the
1635    status codes
1636    <xref target="status.303" format="none">303</xref> and
1637    <xref target="status.307" format="none">307</xref> for servers that wish
1638    to make unambiguously clear which kind of reaction is expected of the
1639    client.
1640  </t>
1641</x:note>
1642</section>
1643
1644<section title="303 See Other" anchor="status.303">
1645  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1646  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1647<t>
1648   The server directs the user agent to a different resource, indicated
1649   by a URI in the Location header field, that provides an indirect
1650   response to the original request.  The user agent &MAY; perform a GET
1651   request on the URI in the Location field in order to obtain a
1652   representation corresponding to the response, be redirected again,
1653   or end with an error status.  The Location URI is not a substitute
1654   reference for the effective request URI.
1655</t>
1656<t>
1657   The 303 status code is generally applicable to any HTTP method.  It is
1658   primarily used to allow the output of a POST action to redirect
1659   the user agent to a selected resource, since doing so provides the
1660   information corresponding to the POST response in a form that
1661   can be separately identified, bookmarked, and cached independent
1662   of the original request.
1663</t>
1664<t>
1665   A 303 response to a GET request indicates that the requested
1666   resource does not have a representation of its own that can be
1667   transferred by the server over HTTP.  The Location URI indicates a
1668   resource that is descriptive of the target resource, such that the
1669   follow-on representation might be useful to recipients without
1670   implying that it adequately represents the target resource.
1671   Note that answers to the questions of what can be represented, what
1672   representations are adequate, and what might be a useful description
1673   are outside the scope of HTTP and thus entirely determined by the
1674   URI owner(s).
1675</t>
1676<t>
1677   Except for responses to a HEAD request, the representation of a 303
1678   response &SHOULD; contain a short hypertext note with a hyperlink
1679   to the Location URI.
1680</t>
1681</section>
1682
1683<section title="304 Not Modified" anchor="status.304">
1684  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1685  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1686  <rdf:Description>
1687    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1688  </rdf:Description>
1689<t>
1690   The response to the request has not been modified since the conditions
1691   indicated by the client's conditional GET request, as defined in &status-304;.
1692</t>
1693</section>
1694
1695<section title="305 Use Proxy" anchor="status.305">
1696  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1697  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1698<t>
1699   The 305 status code was defined in a previous version of this specification
1700   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1701</t>
1702</section>
1703
1704<section title="306 (Unused)" anchor="status.306">
1705  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1706  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1707<t>
1708   The 306 status code was used in a previous version of the
1709   specification, is no longer used, and the code is reserved.
1710</t>
1711</section>
1712
1713<section title="307 Temporary Redirect" anchor="status.307">
1714  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1715  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1716<t>
1717   The target resource resides temporarily under a different URI.
1718   Since the redirection can change over time, the client &SHOULD;
1719   continue to use the effective request URI for future requests.
1720</t>
1721<t>
1722   The temporary URI &SHOULD; be given by the Location field in the
1723   response. Unless the request method was HEAD, the representation of the
1724   response &SHOULD; contain a short hypertext note with a hyperlink to
1725   the new URI(s), since many pre-HTTP/1.1 user agents do not
1726   understand the 307 status code. Therefore, the note &SHOULD; contain the
1727   information necessary for a user to repeat the original request on
1728   the new URI.
1729</t>
1730<t>
1731   If the 307 status code is received in response to a request method
1732   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1733   then the request &MAY; be automatically redirected by the user agent without
1734   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1735   request unless it can be confirmed by the user, since this might
1736   change the conditions under which the request was issued.
1737</t>
1738</section>
1739</section>
1740
1741<section title="Client Error 4xx" anchor="status.4xx">
1742<t>
1743   The 4xx class of status code is intended for cases in which the
1744   client seems to have erred. Except when responding to a HEAD request,
1745   the server &SHOULD; include a representation containing an explanation of the
1746   error situation, and whether it is a temporary or permanent
1747   condition. These status codes are applicable to any request method.
1748   User agents &SHOULD; display any included representation to the user.
1749</t>
1750<t>
1751   If the client is sending data, a server implementation using TCP
1752   &SHOULD; be careful to ensure that the client acknowledges receipt of
1753   the packet(s) containing the response, before the server closes the
1754   input connection. If the client continues sending data to the server
1755   after the close, the server's TCP stack will send a reset packet to
1756   the client, which might erase the client's unacknowledged input buffers
1757   before they can be read and interpreted by the HTTP application.
1758</t>
1759
1760<section title="400 Bad Request" anchor="status.400">
1761  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1762  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1763<t>
1764   The request could not be understood by the server due to malformed
1765   syntax. The client &SHOULD-NOT; repeat the request without
1766   modifications.
1767</t>
1768</section>
1769
1770<section title="401 Unauthorized" anchor="status.401">
1771  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1772  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1773  <rdf:Description>
1774    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1775  </rdf:Description>
1776<t>
1777   The request requires user authentication (see &status-401;).
1778</t>
1779</section>
1780
1781<section title="402 Payment Required" anchor="status.402">
1782  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1783  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1784<t>
1785   This code is reserved for future use.
1786</t>
1787</section>
1788
1789<section title="403 Forbidden" anchor="status.403">
1790  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1791  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1792<t>
1793   The server understood the request, but is refusing to fulfill it.
1794   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1795   If the request method was not HEAD and the server wishes to make
1796   public why the request has not been fulfilled, it &SHOULD; describe the
1797   reason for the refusal in the representation.  If the server does not wish to
1798   make this information available to the client, the status code 404
1799   (Not Found) can be used instead.
1800</t>
1801</section>
1802
1803<section title="404 Not Found" anchor="status.404">
1804  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1805  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1806<t>
1807   The server has not found anything matching the effective request URI. No
1808   indication is given of whether the condition is temporary or
1809   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1810   knows, through some internally configurable mechanism, that an old
1811   resource is permanently unavailable and has no forwarding address.
1812   This status code is commonly used when the server does not wish to
1813   reveal exactly why the request has been refused, or when no other
1814   response is applicable.
1815</t>
1816</section>
1817
1818<section title="405 Method Not Allowed" anchor="status.405">
1819  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1820  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1821<t>
1822   The method specified in the Request-Line is not allowed for the target
1823   resource. The response &MUST; include an
1824   Allow header field containing a list of valid methods for the requested
1825   resource.
1826</t>
1827</section>
1828
1829<section title="406 Not Acceptable" anchor="status.406">
1830  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1831  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1832<t>
1833   The resource identified by the request is only capable of generating
1834   response representations which have content characteristics not acceptable
1835   according to the accept header fields sent in the request.
1836</t>
1837<t>
1838   Unless it was a HEAD request, the response &SHOULD; include a representation
1839   containing a list of available representation characteristics and location(s)
1840   from which the user or user agent can choose the one most
1841   appropriate. The data format is specified by the media type given
1842   in the Content-Type header field. Depending upon the format and the
1843   capabilities of the user agent, selection of the most appropriate
1844   choice &MAY; be performed automatically. However, this specification
1845   does not define any standard for such automatic selection.
1846</t>
1847<x:note>
1848  <t>
1849    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1850    not acceptable according to the accept header fields sent in the
1851    request. In some cases, this might even be preferable to sending a
1852    406 response. User agents are encouraged to inspect the header fields of
1853    an incoming response to determine if it is acceptable.
1854  </t>
1855</x:note>
1856<t>
1857   If the response could be unacceptable, a user agent &SHOULD;
1858   temporarily stop receipt of more data and query the user for a
1859   decision on further actions.
1860</t>
1861</section>
1862
1863<section title="407 Proxy Authentication Required" anchor="status.407">
1864  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1865  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1866<t>
1867   This code is similar to 401 (Unauthorized), but indicates that the
1868   client must first authenticate itself with the proxy (see &status-407;).
1869</t>
1870</section>
1871
1872<section title="408 Request Timeout" anchor="status.408">
1873  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1874  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1875<t>
1876   The client did not produce a request within the time that the server
1877   was prepared to wait. The client &MAY; repeat the request without
1878   modifications at any later time.
1879</t>
1880</section>
1881
1882<section title="409 Conflict" anchor="status.409">
1883  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1884  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1885<t>
1886   The request could not be completed due to a conflict with the current
1887   state of the resource. This code is only allowed in situations where
1888   it is expected that the user might be able to resolve the conflict
1889   and resubmit the request. The response body &SHOULD; include enough
1890   information for the user to recognize the source of the conflict.
1891   Ideally, the response representation would include enough information for the
1892   user or user agent to fix the problem; however, that might not be
1893   possible and is not required.
1894</t>
1895<t>
1896   Conflicts are most likely to occur in response to a PUT request. For
1897   example, if versioning were being used and the representation being PUT
1898   included changes to a resource which conflict with those made by an
1899   earlier (third-party) request, the server might use the 409 response
1900   to indicate that it can't complete the request. In this case, the
1901   response representation would likely contain a list of the differences
1902   between the two versions in a format defined by the response
1903   Content-Type.
1904</t>
1905</section>
1906
1907<section title="410 Gone" anchor="status.410">
1908  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1909  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1910<t>
1911   The target resource is no longer available at the server and no
1912   forwarding address is known. This condition is expected to be
1913   considered permanent. Clients with link editing capabilities &SHOULD;
1914   delete references to the effective request URI after user approval. If the
1915   server does not know, or has no facility to determine, whether or not
1916   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1917   used instead.
1918</t>
1919<t>
1920   The 410 response is primarily intended to assist the task of web
1921   maintenance by notifying the recipient that the resource is
1922   intentionally unavailable and that the server owners desire that
1923   remote links to that resource be removed. Such an event is common for
1924   limited-time, promotional services and for resources belonging to
1925   individuals no longer working at the server's site. It is not
1926   necessary to mark all permanently unavailable resources as "gone" or
1927   to keep the mark for any length of time &mdash; that is left to the
1928   discretion of the server owner.
1929</t>
1930<t>
1931   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine freshness
1932   for 410 responses.
1933</t>
1934
1935</section>
1936
1937<section title="411 Length Required" anchor="status.411">
1938  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1939  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1940<t>
1941   The server refuses to accept the request without a defined Content-Length.
1942   The client &MAY; repeat the request if it adds a valid
1943   Content-Length header field containing the length of the message-body
1944   in the request message.
1945</t>
1946</section>
1947
1948<section title="412 Precondition Failed" anchor="status.412">
1949  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1950  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1951  <rdf:Description>
1952    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1953  </rdf:Description>
1954<t>
1955   The precondition given in one or more of the header fields
1956   evaluated to false when it was tested on the server, as defined in
1957   &status-412;.
1958</t>
1959</section>
1960
1961<section title="413 Request Entity Too Large" anchor="status.413">
1962  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1963  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1964<t>
1965   The server is refusing to process a request because the request
1966   representation is larger than the server is willing or able to process. The
1967   server &MAY; close the connection to prevent the client from continuing
1968   the request.
1969</t>
1970<t>
1971   If the condition is temporary, the server &SHOULD; include a Retry-After
1972   header field to indicate that it is temporary and after what
1973   time the client &MAY; try again.
1974</t>
1975</section>
1976
1977<section title="414 URI Too Long" anchor="status.414">
1978  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
1979  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
1980<t>
1981   The server is refusing to service the request because the effective request URI
1982   is longer than the server is willing to interpret. This rare
1983   condition is only likely to occur when a client has improperly
1984   converted a POST request to a GET request with long query
1985   information, when the client has descended into a URI "black hole" of
1986   redirection (e.g., a redirected URI prefix that points to a suffix of
1987   itself), or when the server is under attack by a client attempting to
1988   exploit security holes present in some servers using fixed-length
1989   buffers for reading or manipulating the effective request URI.
1990</t>
1991</section>
1992
1993<section title="415 Unsupported Media Type" anchor="status.415">
1994  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1995  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1996<t>
1997   The server is refusing to service the request because the request
1998   payload is in a format not supported by this request method on the
1999   target resource.
2000</t>
2001</section>
2002
2003<section title="416 Requested Range Not Satisfiable" anchor="status.416">
2004  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
2005  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
2006  <rdf:Description>
2007    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
2008  </rdf:Description>
2009<t>
2010   The request included a Range header field (&header-range;) and none of
2011   the range-specifier values in this field overlap the current extent
2012   of the selected resource. See &status-416;.
2013</t>
2014</section>
2015
2016<section title="417 Expectation Failed" anchor="status.417">
2017  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
2018  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
2019<t>
2020   The expectation given in an Expect header field (see <xref target="header.expect"/>)
2021   could not be met by this server, or, if the server is a proxy,
2022   the server has unambiguous evidence that the request could not be met
2023   by the next-hop server.
2024</t>
2025</section>
2026
2027<section title="426 Upgrade Required" anchor="status.426">
2028  <iref primary="true" item="426 Upgrade Required (status code)" x:for-anchor=""/>
2029  <iref primary="true" item="Status Codes" subitem="426 Upgrade Required" x:for-anchor=""/>
2030<t>
2031   The request can not be completed without a prior protocol upgrade. This
2032   response &MUST; include an Upgrade header field (&header-upgrade;)
2033   specifying the required protocols.
2034</t>
2035<figure>
2036<preamble>Example:</preamble>
2037<artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
2038HTTP/1.1 426 Upgrade Required
2039Upgrade: HTTP/2.0
2040Connection: Upgrade
2041
2042</artwork></figure>
2043<t>
2044   The server &SHOULD; include a message body in the 426 response which
2045   indicates in human readable form the reason for the error and describes any
2046   alternative courses which may be available to the user.
2047</t>
2048</section>
2049</section>
2050
2051<section title="Server Error 5xx" anchor="status.5xx">
2052<t>
2053   Response status codes beginning with the digit "5" indicate cases in
2054   which the server is aware that it has erred or is incapable of
2055   performing the request. Except when responding to a HEAD request, the
2056   server &SHOULD; include a representation containing an explanation of the
2057   error situation, and whether it is a temporary or permanent
2058   condition. User agents &SHOULD; display any included representation to the
2059   user. These response codes are applicable to any request method.
2060</t>
2061
2062<section title="500 Internal Server Error" anchor="status.500">
2063  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
2064  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
2065<t>
2066   The server encountered an unexpected condition which prevented it
2067   from fulfilling the request.
2068</t>
2069</section>
2070
2071<section title="501 Not Implemented" anchor="status.501">
2072  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
2073  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
2074<t>
2075   The server does not support the functionality required to fulfill the
2076   request. This is the appropriate response when the server does not
2077   recognize the request method and is not capable of supporting it for
2078   any resource.
2079</t>
2080</section>
2081
2082<section title="502 Bad Gateway" anchor="status.502">
2083  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
2084  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
2085<t>
2086   The server, while acting as a gateway or proxy, received an invalid
2087   response from the upstream server it accessed in attempting to
2088   fulfill the request.
2089</t>
2090</section>
2091
2092<section title="503 Service Unavailable" anchor="status.503">
2093  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
2094  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
2095<t>
2096   The server is currently unable to handle the request due to a
2097   temporary overloading or maintenance of the server. The implication
2098   is that this is a temporary condition which will be alleviated after
2099   some delay. If known, the length of the delay &MAY; be indicated in a
2100   Retry-After header field. If no Retry-After is given, the client &SHOULD;
2101   handle the response as it would for a 500 response.
2102</t>
2103<x:note>
2104  <t>
2105    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
2106    server must use it when becoming overloaded. Some servers might wish
2107    to simply refuse the connection.
2108  </t>
2109</x:note>
2110</section>
2111
2112<section title="504 Gateway Timeout" anchor="status.504">
2113  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
2114  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
2115<t>
2116   The server, while acting as a gateway or proxy, did not receive a
2117   timely response from the upstream server specified by the URI (e.g.,
2118   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
2119   to access in attempting to complete the request.
2120</t>
2121<x:note>
2122  <t>
2123    <x:h>Note</x:h> to implementors: some deployed proxies are known to
2124    return 400 or 500 when DNS lookups time out.
2125  </t>
2126</x:note>
2127</section>
2128
2129<section title="505 HTTP Version Not Supported" anchor="status.505">
2130  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
2131  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
2132<t>
2133   The server does not support, or refuses to support, the protocol
2134   version that was used in the request message. The server is
2135   indicating that it is unable or unwilling to complete the request
2136   using the same major version as the client, as described in &http-version;,
2137   other than with this error message. The response &SHOULD; contain
2138   a representation describing why that version is not supported and what other
2139   protocols are supported by that server.
2140</t>
2141
2142</section>
2143</section>
2144</section>
2145
2146
2147<section title="Header Field Definitions" anchor="header.fields">
2148<t>
2149   This section defines the syntax and semantics of HTTP/1.1 header fields
2150   related to request and response semantics.
2151</t>
2152
2153<section title="Allow" anchor="header.allow">
2154  <iref primary="true" item="Allow header field" x:for-anchor=""/>
2155  <iref primary="true" item="Header Fields" subitem="Allow" x:for-anchor=""/>
2156  <x:anchor-alias value="Allow"/>
2157  <x:anchor-alias value="Allow-v"/>
2158<t>
2159   The "Allow" header field lists the set of methods advertised as
2160   supported by the target resource. The purpose of this field is strictly to
2161   inform the recipient of valid request methods associated with the resource.
2162</t>
2163<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
2164  <x:ref>Allow</x:ref>   = "Allow" ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
2165  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
2166</artwork></figure>
2167<t>
2168   Example of use:
2169</t>
2170<figure><artwork type="example">
2171  Allow: GET, HEAD, PUT
2172</artwork></figure>
2173<t>
2174   The actual set of allowed methods is defined by the origin server at the
2175   time of each request.
2176</t>
2177<t>
2178   A proxy &MUST-NOT; modify the Allow header field &mdash; it does not need to
2179   understand all the methods specified in order to handle them according to
2180   the generic message handling rules.
2181</t>
2182</section>
2183
2184<section title="Expect" anchor="header.expect">
2185  <iref primary="true" item="Expect header field" x:for-anchor=""/>
2186  <iref primary="true" item="Header Fields" subitem="Expect" x:for-anchor=""/>
2187  <x:anchor-alias value="Expect"/>
2188  <x:anchor-alias value="Expect-v"/>
2189  <x:anchor-alias value="expectation"/>
2190  <x:anchor-alias value="expectation-extension"/>
2191  <x:anchor-alias value="expect-params"/>
2192<t>
2193   The "Expect" header field is used to indicate that particular
2194   server behaviors are required by the client.
2195</t>
2196<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Expect"/><iref primary="true" item="Grammar" subitem="Expect-v"/><iref primary="true" item="Grammar" subitem="expectation"/><iref primary="true" item="Grammar" subitem="expectation-extension"/><iref primary="true" item="Grammar" subitem="expect-params"/>
2197  <x:ref>Expect</x:ref>       = "Expect" ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
2198  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
2199 
2200  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
2201  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
2202                           *<x:ref>expect-params</x:ref> ]
2203  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
2204</artwork></figure>
2205<t>
2206   A server that does not understand or is unable to comply with any of
2207   the expectation values in the Expect field of a request &MUST; respond
2208   with appropriate error status code. The server &MUST; respond with a 417
2209   (Expectation Failed) status code if any of the expectations cannot be met
2210   or, if there are other problems with the request, some other 4xx
2211   status code.
2212</t>
2213<t>
2214   This header field is defined with extensible syntax to allow for
2215   future extensions. If a server receives a request containing an
2216   Expect field that includes an expectation-extension that it does not
2217   support, it &MUST; respond with a 417 (Expectation Failed) status code.
2218</t>
2219<t>
2220   Comparison of expectation values is case-insensitive for unquoted
2221   tokens (including the 100-continue token), and is case-sensitive for
2222   quoted-string expectation-extensions.
2223</t>
2224<t>
2225   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
2226   return a 417 (Expectation Failed) status code if it receives a request
2227   with an expectation that it cannot meet. However, the Expect
2228   header field itself is end-to-end; it &MUST; be forwarded if the
2229   request is forwarded.
2230</t>
2231<t>
2232   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
2233   Expect header field.
2234</t>
2235<t>
2236   See &use100; for the use of the 100 (Continue) status code.
2237</t>
2238</section>
2239
2240<section title="From" anchor="header.from">
2241  <iref primary="true" item="From header field" x:for-anchor=""/>
2242  <iref primary="true" item="Header Fields" subitem="From" x:for-anchor=""/>
2243  <x:anchor-alias value="From"/>
2244  <x:anchor-alias value="From-v"/>
2245  <x:anchor-alias value="mailbox"/>
2246<t>
2247   The "From" header field, if given, &SHOULD; contain an Internet
2248   e-mail address for the human user who controls the requesting user
2249   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
2250   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
2251</t>
2252<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
2253  <x:ref>From</x:ref>    = "From" ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
2254  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
2255 
2256  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2257</artwork></figure>
2258<t>
2259   An example is:
2260</t>
2261<figure><artwork type="example">
2262  From: webmaster@example.org
2263</artwork></figure>
2264<t>
2265   This header field &MAY; be used for logging purposes and as a means for
2266   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2267   be used as an insecure form of access protection. The interpretation
2268   of this field is that the request is being performed on behalf of the
2269   person given, who accepts responsibility for the method performed. In
2270   particular, robot agents &SHOULD; include this header field so that the
2271   person responsible for running the robot can be contacted if problems
2272   occur on the receiving end.
2273</t>
2274<t>
2275   The Internet e-mail address in this field &MAY; be separate from the
2276   Internet host which issued the request. For example, when a request
2277   is passed through a proxy the original issuer's address &SHOULD; be
2278   used.
2279</t>
2280<t>
2281   The client &SHOULD-NOT;  send the From header field without the user's
2282   approval, as it might conflict with the user's privacy interests or
2283   their site's security policy. It is strongly recommended that the
2284   user be able to disable, enable, and modify the value of this field
2285   at any time prior to a request.
2286</t>
2287</section>
2288
2289<section title="Location" anchor="header.location">
2290  <iref primary="true" item="Location header field" x:for-anchor=""/>
2291  <iref primary="true" item="Header Fields" subitem="Location" x:for-anchor=""/>
2292  <x:anchor-alias value="Location"/>
2293  <x:anchor-alias value="Location-v"/>
2294<t>
2295   The "Location" header field is used to identify a newly created
2296   resource, or to redirect the recipient to a different location for
2297   completion of the request.
2298</t>
2299<t>
2300   For 201 (Created) responses, the Location is the URI of the new resource
2301   which was created by the request. For 3xx responses, the location &SHOULD;
2302   indicate the server's preferred URI for automatic redirection to the
2303   resource.
2304</t>
2305<t>
2306   The field value consists of a single URI-reference. When it has the form
2307   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2308   the final value is computed by resolving it against the effective request
2309   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
2310</t>
2311<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
2312  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
2313  <x:ref>Location-v</x:ref>     = <x:ref>URI-reference</x:ref>
2314</artwork></figure>
2315<figure>
2316<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical WSP below, it's necessary this way for xml2rfc-->
2317<artwork type="example">
2318  Location: http://www.example.org/pub/WWW/People.html#tim
2319</artwork></figure><figure><artwork type="example">  Location: /index.html
2320</artwork></figure>
2321<t>
2322   There are circumstances in which a fragment identifier in a Location URI
2323   would not be appropriate:
2324   <list style="symbols">
2325      <t>With a 201 Created response, because in this usage the Location header
2326      field specifies the URI for the entire created resource.</t>
2327      <t>With 305 Use Proxy.</t>
2328   </list>
2329</t>
2330<x:note>
2331  <t>
2332    <x:h>Note:</x:h> This specification does not define precedence rules
2333    for the case where the original URI, as navigated to by the user
2334    agent, and the Location header field value both contain fragment
2335    identifiers. Thus be aware that including fragment identifiers might
2336    inconvenience anyone relying on the semantics of the original URI's
2337    fragment identifier.
2338  </t>
2339</x:note>
2340<x:note>
2341  <t>
2342    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2343    from Location in that the Content-Location identifies the most specific
2344    resource corresponding to the enclosed representation.
2345    It is therefore possible for a response to contain header fields for
2346    both Location and Content-Location.
2347  </t>
2348</x:note>
2349</section>
2350
2351<section title="Max-Forwards" anchor="header.max-forwards">
2352  <iref primary="true" item="Max-Forwards header field" x:for-anchor=""/>
2353  <iref primary="true" item="Header Fields" subitem="Max-Forwards" x:for-anchor=""/>
2354  <x:anchor-alias value="Max-Forwards"/>
2355  <x:anchor-alias value="Max-Forwards-v"/>
2356<t>
2357   The "Max-Forwards" header field provides a mechanism with the
2358   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2359   methods to limit the number of times that the request is forwarded by
2360   proxies or gateways. This can be useful when the client is attempting to
2361   trace a request which appears to be failing or looping in mid-chain.
2362</t>
2363<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
2364  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
2365  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
2366</artwork></figure>
2367<t>
2368   The Max-Forwards value is a decimal integer indicating the remaining
2369   number of times this request message can be forwarded.
2370</t>
2371<t>
2372   Each proxy or gateway recipient of a TRACE or OPTIONS request
2373   containing a Max-Forwards header field &MUST; check and update its
2374   value prior to forwarding the request. If the received value is zero
2375   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2376   respond as the final recipient. If the received Max-Forwards value is
2377   greater than zero, then the forwarded message &MUST; contain an updated
2378   Max-Forwards field with a value decremented by one (1).
2379</t>
2380<t>
2381   The Max-Forwards header field &MAY; be ignored for all other request
2382   methods.
2383</t>
2384</section>
2385
2386<section title="Referer" anchor="header.referer">
2387  <iref primary="true" item="Referer header field" x:for-anchor=""/>
2388  <iref primary="true" item="Header Fields" subitem="Referer" x:for-anchor=""/>
2389  <x:anchor-alias value="Referer"/>
2390  <x:anchor-alias value="Referer-v"/>
2391<t>
2392   The "Referer" [sic] header field allows the client to specify the
2393   URI of the resource from which the effective request URI was obtained (the
2394   "referrer", although the header field is misspelled.).
2395</t>
2396<t>
2397   The Referer header field allows servers to generate lists of back-links to
2398   resources for interest, logging, optimized caching, etc. It also allows
2399   obsolete or mistyped links to be traced for maintenance. Some servers use
2400   Referer as a means of controlling where they allow links from (so-called
2401   "deep linking"), but legitimate requests do not always
2402   contain a Referer header field.
2403</t>
2404<t>
2405   If the effective request URI was obtained from a source that does not have its own
2406   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
2407   sent with the value "about:blank", or not be sent at all. Note that this
2408   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2409</t>
2410<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
2411  <x:ref>Referer</x:ref>        = "Referer" ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
2412  <x:ref>Referer-v</x:ref>      = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2413</artwork></figure>
2414<t>
2415   Example:
2416</t>
2417<figure><artwork type="example">
2418  Referer: http://www.example.org/hypertext/Overview.html
2419</artwork></figure>
2420<t>
2421   If the field value is a relative URI, it &SHOULD; be interpreted
2422   relative to the effective request URI. The URI &MUST-NOT; include a fragment. See
2423   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2424</t>
2425</section>
2426
2427<section title="Retry-After" anchor="header.retry-after">
2428  <iref primary="true" item="Retry-After header field" x:for-anchor=""/>
2429  <iref primary="true" item="Header Fields" subitem="Retry-After" x:for-anchor=""/>
2430  <x:anchor-alias value="Retry-After"/>
2431  <x:anchor-alias value="Retry-After-v"/>
2432<t>
2433   The header "Retry-After" field can be used with a 503 (Service
2434   Unavailable) response to indicate how long the service is expected to
2435   be unavailable to the requesting client. This field &MAY; also be used
2436   with any 3xx (Redirection) response to indicate the minimum time the
2437   user-agent is asked wait before issuing the redirected request.
2438</t>
2439<t>
2440   The value of this field can be either an HTTP-date or an integer number
2441   of seconds (in decimal) after the time of the response.
2442</t>
2443<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
2444  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
2445  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2446</artwork></figure>
2447<t anchor="rule.delta-seconds">
2448  <x:anchor-alias value="delta-seconds"/>
2449   Time spans are non-negative decimal integers, representing time in
2450   seconds.
2451</t>
2452<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2453  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2454</artwork></figure>
2455<t>
2456   Two examples of its use are
2457</t>
2458<figure><artwork type="example">
2459  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2460  Retry-After: 120
2461</artwork></figure>
2462<t>
2463   In the latter example, the delay is 2 minutes.
2464</t>
2465</section>
2466
2467<section title="Server" anchor="header.server">
2468  <iref primary="true" item="Server header field" x:for-anchor=""/>
2469  <iref primary="true" item="Header Fields" subitem="Server" x:for-anchor=""/>
2470  <x:anchor-alias value="Server"/>
2471  <x:anchor-alias value="Server-v"/>
2472<t>
2473   The "Server" header field contains information about the
2474   software used by the origin server to handle the request.
2475</t>
2476<t>
2477   The field can contain multiple product tokens (&product-tokens;) and
2478   comments (&header-fields;) identifying the server and any significant
2479   subproducts. The product tokens are listed in order of their significance
2480   for identifying the application.
2481</t>
2482<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
2483  <x:ref>Server</x:ref>         = "Server" ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
2484  <x:ref>Server-v</x:ref>       = <x:ref>product</x:ref>
2485                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2486</artwork></figure>
2487<t>
2488   Example:
2489</t>
2490<figure><artwork type="example">
2491  Server: CERN/3.0 libwww/2.17
2492</artwork></figure>
2493<t>
2494   If the response is being forwarded through a proxy, the proxy
2495   application &MUST-NOT; modify the Server header field. Instead, it
2496   &MUST; include a Via field (as described in &header-via;).
2497</t>
2498<x:note>
2499  <t>
2500    <x:h>Note:</x:h> Revealing the specific software version of the server might
2501    allow the server machine to become more vulnerable to attacks
2502    against software that is known to contain security holes. Server
2503    implementors are encouraged to make this field a configurable
2504    option.
2505  </t>
2506</x:note>
2507</section>
2508
2509<section title="User-Agent" anchor="header.user-agent">
2510  <iref primary="true" item="User-Agent header field" x:for-anchor=""/>
2511  <iref primary="true" item="Header Fields" subitem="User-Agent" x:for-anchor=""/>
2512  <x:anchor-alias value="User-Agent"/>
2513  <x:anchor-alias value="User-Agent-v"/>
2514<t>
2515   The "User-Agent" header field contains information about the user
2516   agent originating the request. User agents &SHOULD; include this field with
2517   requests.
2518</t>
2519<t>
2520   Typically, it is used for statistical purposes, the tracing of protocol
2521   violations, and tailoring responses to avoid particular user agent
2522   limitations.
2523</t>
2524<t>
2525   The field can contain multiple product tokens (&product-tokens;)
2526   and comments (&header-fields;) identifying the agent and its
2527   significant subproducts. By convention, the product tokens are listed in
2528   order of their significance for identifying the application.
2529</t>
2530<t>
2531   Because this field is usually sent on every request a user agent makes,
2532   implementations are encouraged not to include needlessly fine-grained
2533   detail, and to limit (or even prohibit) the addition of subproducts by third
2534   parties. Overly long and detailed User-Agent field values make requests
2535   larger and can also be used to identify ("fingerprint") the user against
2536   their wishes.
2537</t>
2538<t>
2539   Likewise, implementations are encouraged not to use the product tokens of
2540   other implementations in order to declare compatibility with them, as this
2541   circumvents the purpose of the field. Finally, they are encouraged not to
2542   use comments to identify products; doing so makes the field value more
2543   difficult to parse.
2544</t>
2545<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
2546  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
2547  <x:ref>User-Agent-v</x:ref>   = <x:ref>product</x:ref> *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2548</artwork></figure>
2549<t>
2550   Example:
2551</t>
2552<figure><artwork type="example">
2553  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2554</artwork></figure>
2555</section>
2556
2557</section>
2558
2559<section title="IANA Considerations" anchor="IANA.considerations">
2560
2561<section title="Method Registry" anchor="method.registration">
2562<t>
2563  The registration procedure for HTTP request methods is defined by
2564  <xref target="method.registry"/> of this document.
2565</t>
2566<t>
2567   The HTTP Method Registry shall be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2568   and be populated with the registrations below:
2569</t>
2570<?BEGININC p2-semantics.iana-methods ?>
2571<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2572<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2573   <ttcol>Method</ttcol>
2574   <ttcol>Safe</ttcol>
2575   <ttcol>Reference</ttcol>
2576   <c>CONNECT</c>
2577   <c>no</c>
2578   <c>
2579      <xref target="CONNECT"/>
2580   </c>
2581   <c>DELETE</c>
2582   <c>no</c>
2583   <c>
2584      <xref target="DELETE"/>
2585   </c>
2586   <c>GET</c>
2587   <c>yes</c>
2588   <c>
2589      <xref target="GET"/>
2590   </c>
2591   <c>HEAD</c>
2592   <c>yes</c>
2593   <c>
2594      <xref target="HEAD"/>
2595   </c>
2596   <c>OPTIONS</c>
2597   <c>yes</c>
2598   <c>
2599      <xref target="OPTIONS"/>
2600   </c>
2601   <c>POST</c>
2602   <c>no</c>
2603   <c>
2604      <xref target="POST"/>
2605   </c>
2606   <c>PUT</c>
2607   <c>no</c>
2608   <c>
2609      <xref target="PUT"/>
2610   </c>
2611   <c>TRACE</c>
2612   <c>yes</c>
2613   <c>
2614      <xref target="TRACE"/>
2615   </c>
2616</texttable>
2617<!--(END)-->
2618<?ENDINC p2-semantics.iana-methods ?>
2619</section>
2620
2621<section title="Status Code Registry" anchor="status.code.registration">
2622<t>
2623   The registration procedure for HTTP Status Codes &mdash; previously defined
2624   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> &mdash; is now defined
2625   by <xref target="status.code.registry"/> of this document.
2626</t>
2627<t>
2628   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2629   shall be updated with the registrations below:
2630</t>
2631<?BEGININC p2-semantics.iana-status-codes ?>
2632<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2633<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2634   <ttcol>Value</ttcol>
2635   <ttcol>Description</ttcol>
2636   <ttcol>Reference</ttcol>
2637   <c>100</c>
2638   <c>Continue</c>
2639   <c>
2640      <xref target="status.100"/>
2641   </c>
2642   <c>101</c>
2643   <c>Switching Protocols</c>
2644   <c>
2645      <xref target="status.101"/>
2646   </c>
2647   <c>200</c>
2648   <c>OK</c>
2649   <c>
2650      <xref target="status.200"/>
2651   </c>
2652   <c>201</c>
2653   <c>Created</c>
2654   <c>
2655      <xref target="status.201"/>
2656   </c>
2657   <c>202</c>
2658   <c>Accepted</c>
2659   <c>
2660      <xref target="status.202"/>
2661   </c>
2662   <c>203</c>
2663   <c>Non-Authoritative Information</c>
2664   <c>
2665      <xref target="status.203"/>
2666   </c>
2667   <c>204</c>
2668   <c>No Content</c>
2669   <c>
2670      <xref target="status.204"/>
2671   </c>
2672   <c>205</c>
2673   <c>Reset Content</c>
2674   <c>
2675      <xref target="status.205"/>
2676   </c>
2677   <c>300</c>
2678   <c>Multiple Choices</c>
2679   <c>
2680      <xref target="status.300"/>
2681   </c>
2682   <c>301</c>
2683   <c>Moved Permanently</c>
2684   <c>
2685      <xref target="status.301"/>
2686   </c>
2687   <c>302</c>
2688   <c>Found</c>
2689   <c>
2690      <xref target="status.302"/>
2691   </c>
2692   <c>303</c>
2693   <c>See Other</c>
2694   <c>
2695      <xref target="status.303"/>
2696   </c>
2697   <c>305</c>
2698   <c>Use Proxy</c>
2699   <c>
2700      <xref target="status.305"/>
2701   </c>
2702   <c>306</c>
2703   <c>(Unused)</c>
2704   <c>
2705      <xref target="status.306"/>
2706   </c>
2707   <c>307</c>
2708   <c>Temporary Redirect</c>
2709   <c>
2710      <xref target="status.307"/>
2711   </c>
2712   <c>400</c>
2713   <c>Bad Request</c>
2714   <c>
2715      <xref target="status.400"/>
2716   </c>
2717   <c>402</c>
2718   <c>Payment Required</c>
2719   <c>
2720      <xref target="status.402"/>
2721   </c>
2722   <c>403</c>
2723   <c>Forbidden</c>
2724   <c>
2725      <xref target="status.403"/>
2726   </c>
2727   <c>404</c>
2728   <c>Not Found</c>
2729   <c>
2730      <xref target="status.404"/>
2731   </c>
2732   <c>405</c>
2733   <c>Method Not Allowed</c>
2734   <c>
2735      <xref target="status.405"/>
2736   </c>
2737   <c>406</c>
2738   <c>Not Acceptable</c>
2739   <c>
2740      <xref target="status.406"/>
2741   </c>
2742   <c>407</c>
2743   <c>Proxy Authentication Required</c>
2744   <c>
2745      <xref target="status.407"/>
2746   </c>
2747   <c>408</c>
2748   <c>Request Timeout</c>
2749   <c>
2750      <xref target="status.408"/>
2751   </c>
2752   <c>409</c>
2753   <c>Conflict</c>
2754   <c>
2755      <xref target="status.409"/>
2756   </c>
2757   <c>410</c>
2758   <c>Gone</c>
2759   <c>
2760      <xref target="status.410"/>
2761   </c>
2762   <c>411</c>
2763   <c>Length Required</c>
2764   <c>
2765      <xref target="status.411"/>
2766   </c>
2767   <c>413</c>
2768   <c>Request Entity Too Large</c>
2769   <c>
2770      <xref target="status.413"/>
2771   </c>
2772   <c>414</c>
2773   <c>URI Too Long</c>
2774   <c>
2775      <xref target="status.414"/>
2776   </c>
2777   <c>415</c>
2778   <c>Unsupported Media Type</c>
2779   <c>
2780      <xref target="status.415"/>
2781   </c>
2782   <c>417</c>
2783   <c>Expectation Failed</c>
2784   <c>
2785      <xref target="status.417"/>
2786   </c>
2787   <c>426</c>
2788   <c>Upgrade Required</c>
2789   <c>
2790      <xref target="status.426"/>
2791   </c>
2792   <c>500</c>
2793   <c>Internal Server Error</c>
2794   <c>
2795      <xref target="status.500"/>
2796   </c>
2797   <c>501</c>
2798   <c>Not Implemented</c>
2799   <c>
2800      <xref target="status.501"/>
2801   </c>
2802   <c>502</c>
2803   <c>Bad Gateway</c>
2804   <c>
2805      <xref target="status.502"/>
2806   </c>
2807   <c>503</c>
2808   <c>Service Unavailable</c>
2809   <c>
2810      <xref target="status.503"/>
2811   </c>
2812   <c>504</c>
2813   <c>Gateway Timeout</c>
2814   <c>
2815      <xref target="status.504"/>
2816   </c>
2817   <c>505</c>
2818   <c>HTTP Version Not Supported</c>
2819   <c>
2820      <xref target="status.505"/>
2821   </c>
2822</texttable>
2823<!--(END)-->
2824<?ENDINC p2-semantics.iana-status-codes ?>
2825</section>
2826<section title="Header Field Registration" anchor="header.field.registration">
2827<t>
2828   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
2829   with the permanent registrations below (see <xref target="RFC3864"/>):
2830</t>
2831<?BEGININC p2-semantics.iana-headers ?>
2832<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2833<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2834   <ttcol>Header Field Name</ttcol>
2835   <ttcol>Protocol</ttcol>
2836   <ttcol>Status</ttcol>
2837   <ttcol>Reference</ttcol>
2838
2839   <c>Allow</c>
2840   <c>http</c>
2841   <c>standard</c>
2842   <c>
2843      <xref target="header.allow"/>
2844   </c>
2845   <c>Expect</c>
2846   <c>http</c>
2847   <c>standard</c>
2848   <c>
2849      <xref target="header.expect"/>
2850   </c>
2851   <c>From</c>
2852   <c>http</c>
2853   <c>standard</c>
2854   <c>
2855      <xref target="header.from"/>
2856   </c>
2857   <c>Location</c>
2858   <c>http</c>
2859   <c>standard</c>
2860   <c>
2861      <xref target="header.location"/>
2862   </c>
2863   <c>Max-Forwards</c>
2864   <c>http</c>
2865   <c>standard</c>
2866   <c>
2867      <xref target="header.max-forwards"/>
2868   </c>
2869   <c>Referer</c>
2870   <c>http</c>
2871   <c>standard</c>
2872   <c>
2873      <xref target="header.referer"/>
2874   </c>
2875   <c>Retry-After</c>
2876   <c>http</c>
2877   <c>standard</c>
2878   <c>
2879      <xref target="header.retry-after"/>
2880   </c>
2881   <c>Server</c>
2882   <c>http</c>
2883   <c>standard</c>
2884   <c>
2885      <xref target="header.server"/>
2886   </c>
2887   <c>User-Agent</c>
2888   <c>http</c>
2889   <c>standard</c>
2890   <c>
2891      <xref target="header.user-agent"/>
2892   </c>
2893</texttable>
2894<!--(END)-->
2895<?ENDINC p2-semantics.iana-headers ?>
2896<t>
2897   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2898</t>
2899</section>
2900</section>
2901
2902<section title="Security Considerations" anchor="security.considerations">
2903<t>
2904   This section is meant to inform application developers, information
2905   providers, and users of the security limitations in HTTP/1.1 as
2906   described by this document. The discussion does not include
2907   definitive solutions to the problems revealed, though it does make
2908   some suggestions for reducing security risks.
2909</t>
2910
2911<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2912<t>
2913   Like any generic data transfer protocol, HTTP cannot regulate the
2914   content of the data that is transferred, nor is there any a priori
2915   method of determining the sensitivity of any particular piece of
2916   information within the context of any given request. Therefore,
2917   applications &SHOULD; supply as much control over this information as
2918   possible to the provider of that information. Four header fields are
2919   worth special mention in this context: Server, Via, Referer and From.
2920</t>
2921<t>
2922   Revealing the specific software version of the server might allow the
2923   server machine to become more vulnerable to attacks against software
2924   that is known to contain security holes. Implementors &SHOULD; make the
2925   Server header field a configurable option.
2926</t>
2927<t>
2928   Proxies which serve as a portal through a network firewall &SHOULD;
2929   take special precautions regarding the transfer of header information
2930   that identifies the hosts behind the firewall. In particular, they
2931   &SHOULD; remove, or replace with sanitized versions, any Via fields
2932   generated behind the firewall.
2933</t>
2934<t>
2935   The Referer header field allows reading patterns to be studied and reverse
2936   links drawn. Although it can be very useful, its power can be abused
2937   if user details are not separated from the information contained in
2938   the Referer. Even when the personal information has been removed, the
2939   Referer header field might indicate a private document's URI whose
2940   publication would be inappropriate.
2941</t>
2942<t>
2943   The information sent in the From field might conflict with the user's
2944   privacy interests or their site's security policy, and hence it
2945   &SHOULD-NOT;  be transmitted without the user being able to disable,
2946   enable, and modify the contents of the field. The user &MUST; be able
2947   to set the contents of this field within a user preference or
2948   application defaults configuration.
2949</t>
2950<t>
2951   We suggest, though do not require, that a convenient toggle interface
2952   be provided for the user to enable or disable the sending of From and
2953   Referer information.
2954</t>
2955<t>
2956   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref
2957   target="header.server"/>) header fields can sometimes be used to determine
2958   that a specific client or server have a particular security hole which might
2959   be exploited. Unfortunately, this same information is often used for other
2960   valuable purposes for which HTTP currently has no better mechanism.
2961</t>
2962<t>
2963   Furthermore, the User-Agent header field may contain enough entropy to be
2964   used, possibly in conjunction with other material, to uniquely identify the
2965   user.
2966</t>
2967<t>
2968   Some request methods, like TRACE (<xref target="TRACE"/>), expose information
2969   that was sent in request header fields within the body of their response.
2970   Clients &SHOULD; be careful with sensitive information, like Cookies,
2971   Authorization credentials, and other header fields that might be used to
2972   collect data from the client.
2973</t> 
2974</section>
2975
2976<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2977<t>
2978   Because the source of a link might be private information or might
2979   reveal an otherwise private information source, it is strongly
2980   recommended that the user be able to select whether or not the
2981   Referer field is sent. For example, a browser client could have a
2982   toggle switch for browsing openly/anonymously, which would
2983   respectively enable/disable the sending of Referer and From
2984   information.
2985</t>
2986<t>
2987   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2988   HTTP request if the referring page was transferred with a secure
2989   protocol.
2990</t>
2991<t>
2992   Authors of services &SHOULD-NOT; use GET-based forms for the submission of
2993   sensitive data because that data will be placed in the request-target. Many
2994   existing servers, proxies, and user agents log or display the request-target
2995   in places where it might be visible to third parties. Such services can
2996   use POST-based form submission instead.
2997</t>
2998</section>
2999
3000<section title="Location Headers and Spoofing" anchor="location.spoofing">
3001<t>
3002   If a single server supports multiple organizations that do not trust
3003   one another, then it &MUST; check the values of Location and Content-Location
3004   header fields in responses that are generated under control of
3005   said organizations to make sure that they do not attempt to
3006   invalidate resources over which they have no authority.
3007</t>
3008</section>
3009
3010<section title="Security Considerations for CONNECT">
3011<t>
3012   Since tunneled data is opaque to the proxy, there are additional
3013   risks to tunneling to other well-known or reserved ports.
3014   A HTTP client CONNECTing to port 25 could relay spam
3015   via SMTP, for example. As such, proxies &SHOULD; restrict CONNECT
3016   access to a small number of known ports.
3017</t>
3018</section>
3019
3020</section>
3021
3022<section title="Acknowledgments" anchor="ack">
3023</section>
3024</middle>
3025<back>
3026
3027<references title="Normative References">
3028
3029<reference anchor="Part1">
3030  <front>
3031    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
3032    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3033      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3034      <address><email>fielding@gbiv.com</email></address>
3035    </author>
3036    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3037      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3038      <address><email>jg@freedesktop.org</email></address>
3039    </author>
3040    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3041      <organization abbrev="HP">Hewlett-Packard Company</organization>
3042      <address><email>JeffMogul@acm.org</email></address>
3043    </author>
3044    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3045      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3046      <address><email>henrikn@microsoft.com</email></address>
3047    </author>
3048    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3049      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3050      <address><email>LMM@acm.org</email></address>
3051    </author>
3052    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3053      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3054      <address><email>paulle@microsoft.com</email></address>
3055    </author>
3056    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3057      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3058      <address><email>timbl@w3.org</email></address>
3059    </author>
3060    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3061      <organization abbrev="W3C">World Wide Web Consortium</organization>
3062      <address><email>ylafon@w3.org</email></address>
3063    </author>
3064    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3065      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3066      <address><email>julian.reschke@greenbytes.de</email></address>
3067    </author>
3068    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3069  </front>
3070  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
3071  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
3072</reference>
3073
3074<reference anchor="Part3">
3075  <front>
3076    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
3077    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3078      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3079      <address><email>fielding@gbiv.com</email></address>
3080    </author>
3081    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3082      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3083      <address><email>jg@freedesktop.org</email></address>
3084    </author>
3085    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3086      <organization abbrev="HP">Hewlett-Packard Company</organization>
3087      <address><email>JeffMogul@acm.org</email></address>
3088    </author>
3089    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3090      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3091      <address><email>henrikn@microsoft.com</email></address>
3092    </author>
3093    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3094      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3095      <address><email>LMM@acm.org</email></address>
3096    </author>
3097    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3098      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3099      <address><email>paulle@microsoft.com</email></address>
3100    </author>
3101    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3102      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3103      <address><email>timbl@w3.org</email></address>
3104    </author>
3105    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3106      <organization abbrev="W3C">World Wide Web Consortium</organization>
3107      <address><email>ylafon@w3.org</email></address>
3108    </author>
3109    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3110      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3111      <address><email>julian.reschke@greenbytes.de</email></address>
3112    </author>
3113    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3114  </front>
3115  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
3116  <x:source href="p3-payload.xml" basename="p3-payload"/>
3117</reference>
3118
3119<reference anchor="Part4">
3120  <front>
3121    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
3122    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3123      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3124      <address><email>fielding@gbiv.com</email></address>
3125    </author>
3126    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3127      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3128      <address><email>jg@freedesktop.org</email></address>
3129    </author>
3130    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3131      <organization abbrev="HP">Hewlett-Packard Company</organization>
3132      <address><email>JeffMogul@acm.org</email></address>
3133    </author>
3134    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3135      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3136      <address><email>henrikn@microsoft.com</email></address>
3137    </author>
3138    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3139      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3140      <address><email>LMM@acm.org</email></address>
3141    </author>
3142    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3143      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3144      <address><email>paulle@microsoft.com</email></address>
3145    </author>
3146    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3147      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3148      <address><email>timbl@w3.org</email></address>
3149    </author>
3150    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3151      <organization abbrev="W3C">World Wide Web Consortium</organization>
3152      <address><email>ylafon@w3.org</email></address>
3153    </author>
3154    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3155      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3156      <address><email>julian.reschke@greenbytes.de</email></address>
3157    </author>
3158    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3159  </front>
3160  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
3161  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
3162</reference>
3163
3164<reference anchor="Part5">
3165  <front>
3166    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
3167    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3168      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3169      <address><email>fielding@gbiv.com</email></address>
3170    </author>
3171    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3172      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3173      <address><email>jg@freedesktop.org</email></address>
3174    </author>
3175    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3176      <organization abbrev="HP">Hewlett-Packard Company</organization>
3177      <address><email>JeffMogul@acm.org</email></address>
3178    </author>
3179    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3180      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3181      <address><email>henrikn@microsoft.com</email></address>
3182    </author>
3183    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3184      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3185      <address><email>LMM@acm.org</email></address>
3186    </author>
3187    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3188      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3189      <address><email>paulle@microsoft.com</email></address>
3190    </author>
3191    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3192      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3193      <address><email>timbl@w3.org</email></address>
3194    </author>
3195    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3196      <organization abbrev="W3C">World Wide Web Consortium</organization>
3197      <address><email>ylafon@w3.org</email></address>
3198    </author>
3199    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3200      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3201      <address><email>julian.reschke@greenbytes.de</email></address>
3202    </author>
3203    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3204  </front>
3205  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
3206  <x:source href="p5-range.xml" basename="p5-range"/>
3207</reference>
3208
3209<reference anchor="Part6">
3210  <front>
3211    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
3212    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3213      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3214      <address><email>fielding@gbiv.com</email></address>
3215    </author>
3216    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3217      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3218      <address><email>jg@freedesktop.org</email></address>
3219    </author>
3220    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3221      <organization abbrev="HP">Hewlett-Packard Company</organization>
3222      <address><email>JeffMogul@acm.org</email></address>
3223    </author>
3224    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3225      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3226      <address><email>henrikn@microsoft.com</email></address>
3227    </author>
3228    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3229      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3230      <address><email>LMM@acm.org</email></address>
3231    </author>
3232    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3233      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3234      <address><email>paulle@microsoft.com</email></address>
3235    </author>
3236    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3237      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3238      <address><email>timbl@w3.org</email></address>
3239    </author>
3240    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3241      <organization abbrev="W3C">World Wide Web Consortium</organization>
3242      <address><email>ylafon@w3.org</email></address>
3243    </author>
3244    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
3245      <address><email>mnot@mnot.net</email></address>
3246    </author>
3247    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3248      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3249      <address><email>julian.reschke@greenbytes.de</email></address>
3250    </author>
3251    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3252  </front>
3253  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
3254  <x:source href="p6-cache.xml" basename="p6-cache"/>
3255</reference>
3256
3257<reference anchor="Part7">
3258  <front>
3259    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
3260    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3261      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3262      <address><email>fielding@gbiv.com</email></address>
3263    </author>
3264    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3265      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3266      <address><email>jg@freedesktop.org</email></address>
3267    </author>
3268    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3269      <organization abbrev="HP">Hewlett-Packard Company</organization>
3270      <address><email>JeffMogul@acm.org</email></address>
3271    </author>
3272    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3273      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3274      <address><email>henrikn@microsoft.com</email></address>
3275    </author>
3276    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3277      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3278      <address><email>LMM@acm.org</email></address>
3279    </author>
3280    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3281      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3282      <address><email>paulle@microsoft.com</email></address>
3283    </author>
3284    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3285      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3286      <address><email>timbl@w3.org</email></address>
3287    </author>
3288    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3289      <organization abbrev="W3C">World Wide Web Consortium</organization>
3290      <address><email>ylafon@w3.org</email></address>
3291    </author>
3292    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3293      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3294      <address><email>julian.reschke@greenbytes.de</email></address>
3295    </author>
3296    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3297  </front>
3298  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3299  <x:source href="p7-auth.xml" basename="p7-auth"/>
3300</reference>
3301
3302<reference anchor="RFC2119">
3303  <front>
3304    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3305    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3306      <organization>Harvard University</organization>
3307      <address><email>sob@harvard.edu</email></address>
3308    </author>
3309    <date month="March" year="1997"/>
3310  </front>
3311  <seriesInfo name="BCP" value="14"/>
3312  <seriesInfo name="RFC" value="2119"/>
3313</reference>
3314
3315<reference anchor="RFC3986">
3316 <front>
3317  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3318  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3319    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3320    <address>
3321       <email>timbl@w3.org</email>
3322       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3323    </address>
3324  </author>
3325  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3326    <organization abbrev="Day Software">Day Software</organization>
3327    <address>
3328      <email>fielding@gbiv.com</email>
3329      <uri>http://roy.gbiv.com/</uri>
3330    </address>
3331  </author>
3332  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3333    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3334    <address>
3335      <email>LMM@acm.org</email>
3336      <uri>http://larry.masinter.net/</uri>
3337    </address>
3338  </author>
3339  <date month='January' year='2005'></date>
3340 </front>
3341 <seriesInfo name="STD" value="66"/>
3342 <seriesInfo name="RFC" value="3986"/>
3343</reference>
3344
3345<reference anchor="RFC5234">
3346  <front>
3347    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3348    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3349      <organization>Brandenburg InternetWorking</organization>
3350      <address>
3351        <email>dcrocker@bbiw.net</email>
3352      </address> 
3353    </author>
3354    <author initials="P." surname="Overell" fullname="Paul Overell">
3355      <organization>THUS plc.</organization>
3356      <address>
3357        <email>paul.overell@thus.net</email>
3358      </address>
3359    </author>
3360    <date month="January" year="2008"/>
3361  </front>
3362  <seriesInfo name="STD" value="68"/>
3363  <seriesInfo name="RFC" value="5234"/>
3364</reference>
3365
3366</references>
3367
3368<references title="Informative References">
3369
3370<reference anchor="RFC1945">
3371  <front>
3372    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3373    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3374      <organization>MIT, Laboratory for Computer Science</organization>
3375      <address><email>timbl@w3.org</email></address>
3376    </author>
3377    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3378      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3379      <address><email>fielding@ics.uci.edu</email></address>
3380    </author>
3381    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3382      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3383      <address><email>frystyk@w3.org</email></address>
3384    </author>
3385    <date month="May" year="1996"/>
3386  </front>
3387  <seriesInfo name="RFC" value="1945"/>
3388</reference>
3389
3390<reference anchor="RFC2068">
3391  <front>
3392    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3393    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3394      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3395      <address><email>fielding@ics.uci.edu</email></address>
3396    </author>
3397    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3398      <organization>MIT Laboratory for Computer Science</organization>
3399      <address><email>jg@w3.org</email></address>
3400    </author>
3401    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3402      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3403      <address><email>mogul@wrl.dec.com</email></address>
3404    </author>
3405    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3406      <organization>MIT Laboratory for Computer Science</organization>
3407      <address><email>frystyk@w3.org</email></address>
3408    </author>
3409    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3410      <organization>MIT Laboratory for Computer Science</organization>
3411      <address><email>timbl@w3.org</email></address>
3412    </author>
3413    <date month="January" year="1997"/>
3414  </front>
3415  <seriesInfo name="RFC" value="2068"/>
3416</reference>
3417
3418<reference anchor="RFC2616">
3419  <front>
3420    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3421    <author initials="R." surname="Fielding" fullname="R. Fielding">
3422      <organization>University of California, Irvine</organization>
3423      <address><email>fielding@ics.uci.edu</email></address>
3424    </author>
3425    <author initials="J." surname="Gettys" fullname="J. Gettys">
3426      <organization>W3C</organization>
3427      <address><email>jg@w3.org</email></address>
3428    </author>
3429    <author initials="J." surname="Mogul" fullname="J. Mogul">
3430      <organization>Compaq Computer Corporation</organization>
3431      <address><email>mogul@wrl.dec.com</email></address>
3432    </author>
3433    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3434      <organization>MIT Laboratory for Computer Science</organization>
3435      <address><email>frystyk@w3.org</email></address>
3436    </author>
3437    <author initials="L." surname="Masinter" fullname="L. Masinter">
3438      <organization>Xerox Corporation</organization>
3439      <address><email>masinter@parc.xerox.com</email></address>
3440    </author>
3441    <author initials="P." surname="Leach" fullname="P. Leach">
3442      <organization>Microsoft Corporation</organization>
3443      <address><email>paulle@microsoft.com</email></address>
3444    </author>
3445    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3446      <organization>W3C</organization>
3447      <address><email>timbl@w3.org</email></address>
3448    </author>
3449    <date month="June" year="1999"/>
3450  </front>
3451  <seriesInfo name="RFC" value="2616"/>
3452</reference>
3453
3454<reference anchor='RFC2817'>
3455  <front>
3456    <title>Upgrading to TLS Within HTTP/1.1</title>
3457    <author initials='R.' surname='Khare' fullname='R. Khare'>
3458      <organization>4K Associates / UC Irvine</organization>
3459      <address><email>rohit@4K-associates.com</email></address>
3460    </author>
3461    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3462      <organization>Agranat Systems, Inc.</organization>
3463      <address><email>lawrence@agranat.com</email></address>
3464    </author>
3465    <date year='2000' month='May' />
3466  </front>
3467  <seriesInfo name='RFC' value='2817' />
3468</reference>
3469
3470<reference anchor='RFC3864'>
3471  <front>
3472    <title>Registration Procedures for Message Header Fields</title>
3473    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3474      <organization>Nine by Nine</organization>
3475      <address><email>GK-IETF@ninebynine.org</email></address>
3476    </author>
3477    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3478      <organization>BEA Systems</organization>
3479      <address><email>mnot@pobox.com</email></address>
3480    </author>
3481    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3482      <organization>HP Labs</organization>
3483      <address><email>JeffMogul@acm.org</email></address>
3484    </author>
3485    <date year='2004' month='September' />
3486  </front>
3487  <seriesInfo name='BCP' value='90' />
3488  <seriesInfo name='RFC' value='3864' />
3489</reference>
3490
3491<reference anchor='RFC5226'>
3492  <front>
3493    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3494    <author initials='T.' surname='Narten' fullname='T. Narten'>
3495      <organization>IBM</organization>
3496      <address><email>narten@us.ibm.com</email></address>
3497    </author>
3498    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3499      <organization>Google</organization>
3500      <address><email>Harald@Alvestrand.no</email></address>
3501    </author>
3502    <date year='2008' month='May' />
3503  </front>
3504  <seriesInfo name='BCP' value='26' />
3505  <seriesInfo name='RFC' value='5226' />
3506</reference>
3507
3508<reference anchor="RFC5322">
3509  <front>
3510    <title>Internet Message Format</title>
3511    <author initials="P." surname="Resnick" fullname="P. Resnick">
3512      <organization>Qualcomm Incorporated</organization>
3513    </author>
3514    <date year="2008" month="October"/>
3515  </front> 
3516  <seriesInfo name="RFC" value="5322"/>
3517</reference>
3518
3519<reference anchor='RFC5789'>
3520  <front>
3521    <title>PATCH Method for HTTP</title>
3522    <author initials='L.' surname='Dusseault' fullname='L. Dusseault'>
3523      <organization>Linden Lab</organization>
3524    </author>
3525    <author initials='J.' surname='Snell' fullname='J. Snell' />
3526    <date year='2010' month='March' />
3527  </front>
3528  <seriesInfo name='RFC' value='5789' />
3529</reference>
3530
3531</references>
3532
3533<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3534<t>
3535  This document takes over the Status Code Registry, previously defined
3536  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3537  (<xref target="status.code.registry"/>)
3538</t>
3539<t>
3540  Clarify definition of POST.
3541  (<xref target="POST"/>)
3542</t>
3543<t>
3544  Remove requirement to handle all Content-* header fields; ban use of
3545  Content-Range with PUT.
3546  (<xref target="PUT"/>)
3547</t>
3548<t>
3549  Take over definition of CONNECT method from <xref target="RFC2817"/>.
3550  (<xref target="CONNECT"/>)
3551</t>
3552<t>
3553  Failed to consider that there are
3554  many other request methods that are safe to automatically redirect,
3555  and further that the user agent is able to make that determination
3556  based on the request method semantics.
3557  (Sections <xref format="counter" target="status.301"/>,
3558  <xref format="counter" target="status.302"/> and
3559  <xref format="counter" target="status.307"/>)
3560</t>
3561<t>
3562  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3563  It used to indicate that the target resource must be accessed through the
3564  proxy given by the Location field. The Location field gave the URI of the
3565  proxy. The recipient was expected to repeat this single request via the proxy.
3566  (<xref target="status.305"/>)
3567</t>
3568<t>
3569  Define status 426 (Upgrade Required) (this was incorporated from
3570  <xref target="RFC2817"/>).
3571  (<xref target="status.426"/>)
3572</t>
3573<t>
3574  Reclassify "Allow" as response header field, removing the option to
3575  specify it in a PUT request.
3576  Relax the server requirement on the contents of the Allow header field and
3577  remove requirement on clients to always trust the header field value.
3578  (<xref target="header.allow"/>)
3579</t>
3580<t>
3581  Correct syntax of Location header field to allow URI references (including
3582  relative references and fragments), as referred symbol "absoluteURI" wasn't
3583  what was expected, and add some clarifications as to when use of fragments
3584  would not be appropriate.
3585  (<xref target="header.location"/>)
3586</t>
3587<t>
3588  Restrict Max-Forwards header field to OPTIONS and TRACE (previously,
3589  extension methods could have used it as well).
3590  (<xref target="header.max-forwards"/>)
3591</t>
3592<t>
3593  Allow Referer field value of "about:blank" as alternative to not specifying it.
3594  (<xref target="header.referer"/>)
3595</t>
3596<t>
3597  In the description of the Server header field, the Via field
3598  was described as a SHOULD. The requirement was and is stated
3599  correctly in the description of the Via header field in &header-via;.
3600  (<xref target="header.server"/>)
3601</t>
3602</section>
3603
3604<?BEGININC p2-semantics.abnf-appendix ?>
3605<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3606<figure>
3607<artwork type="abnf" name="p2-semantics.parsed-abnf">
3608<x:ref>Accept</x:ref> = &lt;Accept, defined in [Part3], Section 6.1&gt;
3609<x:ref>Accept-Charset</x:ref> = &lt;Accept-Charset, defined in [Part3], Section 6.2&gt;
3610<x:ref>Accept-Encoding</x:ref> = &lt;Accept-Encoding, defined in [Part3], Section 6.3&gt;
3611<x:ref>Accept-Language</x:ref> = &lt;Accept-Language, defined in [Part3], Section 6.4&gt;
3612<x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in [Part5], Section 5.1&gt;
3613<x:ref>Age</x:ref> = &lt;Age, defined in [Part6], Section 3.1&gt;
3614<x:ref>Allow</x:ref> = "Allow:" OWS Allow-v
3615<x:ref>Allow-v</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3616<x:ref>Authorization</x:ref> = &lt;Authorization, defined in [Part7], Section 4.1&gt;
3617
3618<x:ref>ETag</x:ref> = &lt;ETag, defined in [Part4], Section 6.1&gt;
3619<x:ref>Expect</x:ref> = "Expect:" OWS Expect-v
3620<x:ref>Expect-v</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3621
3622<x:ref>From</x:ref> = "From:" OWS From-v
3623<x:ref>From-v</x:ref> = mailbox
3624
3625<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 6.1&gt;
3626<x:ref>Host</x:ref> = &lt;Host, defined in [Part1], Section 2.6&gt;
3627
3628<x:ref>If-Match</x:ref> = &lt;If-Match, defined in [Part4], Section 6.2&gt;
3629If-Modified-Since =
3630 &lt;If-Modified-Since, defined in [Part4], Section 6.3&gt;
3631<x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in [Part4], Section 6.4&gt;
3632<x:ref>If-Range</x:ref> = &lt;If-Range, defined in [Part5], Section 5.3&gt;
3633If-Unmodified-Since =
3634 &lt;If-Unmodified-Since, defined in [Part4], Section 6.5&gt;
3635
3636<x:ref>Location</x:ref> = "Location:" OWS Location-v
3637<x:ref>Location-v</x:ref> = URI-reference
3638
3639<x:ref>Max-Forwards</x:ref> = "Max-Forwards:" OWS Max-Forwards-v
3640<x:ref>Max-Forwards-v</x:ref> = 1*DIGIT
3641<x:ref>Method</x:ref> = token
3642
3643<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
3644
3645Proxy-Authenticate =
3646 &lt;Proxy-Authenticate, defined in [Part7], Section 4.2&gt;
3647Proxy-Authorization =
3648 &lt;Proxy-Authorization, defined in [Part7], Section 4.3&gt;
3649
3650<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3651<x:ref>Range</x:ref> = &lt;Range, defined in [Part5], Section 5.4&gt;
3652<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
3653<x:ref>Referer</x:ref> = "Referer:" OWS Referer-v
3654<x:ref>Referer-v</x:ref> = absolute-URI / partial-URI
3655<x:ref>Retry-After</x:ref> = "Retry-After:" OWS Retry-After-v
3656<x:ref>Retry-After-v</x:ref> = HTTP-date / delta-seconds
3657
3658<x:ref>Server</x:ref> = "Server:" OWS Server-v
3659<x:ref>Server-v</x:ref> = product *( RWS ( product / comment ) )
3660<x:ref>Status-Code</x:ref> = 3DIGIT
3661
3662<x:ref>TE</x:ref> = &lt;TE, defined in [Part1], Section 9.5&gt;
3663
3664<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.6&gt;
3665<x:ref>User-Agent</x:ref> = "User-Agent:" OWS User-Agent-v
3666<x:ref>User-Agent-v</x:ref> = product *( RWS ( product / comment ) )
3667
3668<x:ref>Vary</x:ref> = &lt;Vary, defined in [Part6], Section 3.5&gt;
3669
3670WWW-Authenticate =
3671 &lt;WWW-Authenticate, defined in [Part7], Section 4.4&gt;
3672
3673<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.6&gt;
3674
3675<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2&gt;
3676
3677<x:ref>delta-seconds</x:ref> = 1*DIGIT
3678
3679<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
3680<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
3681<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
3682 *expect-params ]
3683
3684<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
3685
3686<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
3687
3688<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.6&gt;
3689<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 6.3&gt;
3690
3691<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
3692
3693<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
3694</artwork>
3695</figure>
3696<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
3697; Accept defined but not used
3698; Accept-Charset defined but not used
3699; Accept-Encoding defined but not used
3700; Accept-Language defined but not used
3701; Accept-Ranges defined but not used
3702; Age defined but not used
3703; Allow defined but not used
3704; Authorization defined but not used
3705; ETag defined but not used
3706; Expect defined but not used
3707; From defined but not used
3708; Host defined but not used
3709; If-Match defined but not used
3710; If-Modified-Since defined but not used
3711; If-None-Match defined but not used
3712; If-Range defined but not used
3713; If-Unmodified-Since defined but not used
3714; Location defined but not used
3715; Max-Forwards defined but not used
3716; Proxy-Authenticate defined but not used
3717; Proxy-Authorization defined but not used
3718; Range defined but not used
3719; Reason-Phrase defined but not used
3720; Referer defined but not used
3721; Retry-After defined but not used
3722; Server defined but not used
3723; Status-Code defined but not used
3724; TE defined but not used
3725; User-Agent defined but not used
3726; Vary defined but not used
3727; WWW-Authenticate defined but not used
3728</artwork></figure></section>
3729<?ENDINC p2-semantics.abnf-appendix ?>
3730
3731<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3732
3733<section title="Since RFC 2616">
3734<t>
3735  Extracted relevant partitions from <xref target="RFC2616"/>.
3736</t>
3737</section>
3738
3739<section title="Since draft-ietf-httpbis-p2-semantics-00">
3740<t>
3741  Closed issues:
3742  <list style="symbols"> 
3743    <t>
3744      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3745      "Via is a MUST"
3746      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3747    </t>
3748    <t>
3749      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3750      "Fragments allowed in Location"
3751      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3752    </t>
3753    <t>
3754      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3755      "Safe Methods vs Redirection"
3756      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3757    </t>
3758    <t>
3759      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3760      "Revise description of the POST method"
3761      (<eref target="http://purl.org/NET/http-errata#post"/>)
3762    </t>
3763    <t>
3764      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3765      "Normative and Informative references"
3766    </t>
3767    <t>
3768      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3769      "RFC2606 Compliance"
3770    </t>
3771    <t>
3772      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3773      "Informative references"
3774    </t>
3775    <t>
3776      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3777      "Redundant cross-references"
3778    </t>
3779  </list>
3780</t>
3781<t>
3782  Other changes:
3783  <list style="symbols"> 
3784    <t>
3785      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3786    </t>
3787  </list>
3788</t>
3789</section>
3790
3791<section title="Since draft-ietf-httpbis-p2-semantics-01">
3792<t>
3793  Closed issues:
3794  <list style="symbols"> 
3795    <t>
3796      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3797      "PUT side effects"
3798    </t>
3799    <t>
3800      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3801      "Duplicate Host header requirements"
3802    </t>
3803  </list>
3804</t>
3805<t>
3806  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3807  <list style="symbols"> 
3808    <t>
3809      Move "Product Tokens" section (back) into Part 1, as "token" is used
3810      in the definition of the Upgrade header field.
3811    </t>
3812    <t>
3813      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3814    </t>
3815    <t>
3816      Copy definition of delta-seconds from Part6 instead of referencing it.
3817    </t>
3818  </list>
3819</t>
3820</section>
3821
3822<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3823<t>
3824  Closed issues:
3825  <list style="symbols"> 
3826    <t>
3827      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3828      "Requiring Allow in 405 responses"
3829    </t>
3830    <t>
3831      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3832      "Status Code Registry"
3833    </t>
3834    <t>
3835      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3836      "Redirection vs. Location"
3837    </t>
3838    <t>
3839      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3840      "Cacheability of 303 response"
3841    </t>
3842    <t>
3843      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3844      "305 Use Proxy"
3845    </t>
3846    <t>
3847      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3848      "Classification for Allow header"
3849    </t>
3850    <t>
3851      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3852      "PUT - 'store under' vs 'store at'"
3853    </t>
3854  </list>
3855</t>
3856<t>
3857  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3858  <list style="symbols"> 
3859    <t>
3860      Reference RFC 3984, and update header field registrations for headers defined
3861      in this document.
3862    </t>
3863  </list>
3864</t>
3865<t>
3866  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3867  <list style="symbols"> 
3868    <t>
3869      Replace string literals when the string really is case-sensitive (method).
3870    </t>
3871  </list>
3872</t>
3873</section>
3874
3875<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3876<t>
3877  Closed issues:
3878  <list style="symbols"> 
3879    <t>
3880      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
3881      "OPTIONS request bodies"
3882    </t>
3883    <t>
3884      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
3885      "Description of CONNECT should refer to RFC2817"
3886    </t>
3887    <t>
3888      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
3889      "Location Content-Location reference request/response mixup"
3890    </t>
3891  </list>
3892</t>
3893<t>
3894  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
3895  <list style="symbols"> 
3896    <t>
3897      Added initial proposal for registration process, plus initial
3898      content (non-HTTP/1.1 methods to be added by a separate specification).
3899    </t>
3900  </list>
3901</t>
3902</section>
3903
3904<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3905<t>
3906  Closed issues:
3907  <list style="symbols"> 
3908    <t>
3909      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3910      "Content-*"
3911    </t>
3912    <t>
3913      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3914      "RFC 2822 is updated by RFC 5322"
3915    </t>
3916  </list>
3917</t>
3918<t>
3919  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3920  <list style="symbols"> 
3921    <t>
3922      Use "/" instead of "|" for alternatives.
3923    </t>
3924    <t>
3925      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3926      whitespace ("OWS") and required whitespace ("RWS").
3927    </t>
3928    <t>
3929      Rewrite ABNFs to spell out whitespace rules, factor out
3930      header field value format definitions.
3931    </t>
3932  </list>
3933</t>
3934</section>
3935
3936<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3937<t>
3938  Closed issues:
3939  <list style="symbols"> 
3940    <t>
3941      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
3942      "Reason-Phrase BNF"
3943    </t>
3944  </list>
3945</t>
3946<t>
3947  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3948  <list style="symbols"> 
3949    <t>
3950      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3951    </t>
3952  </list>
3953</t>
3954</section>
3955
3956<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
3957<t>
3958  Closed issues:
3959  <list style="symbols"> 
3960    <t>
3961      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
3962      "Clarify when Referer is sent"
3963    </t>
3964    <t>
3965      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
3966      "status codes vs methods"
3967    </t>
3968    <t>
3969      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
3970      "Do not require "updates" relation for specs that register status codes or method names"
3971    </t>
3972  </list>
3973</t>
3974</section>
3975
3976<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
3977<t>
3978  Closed issues:
3979  <list style="symbols"> 
3980    <t>
3981      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
3982      "Idempotency"
3983    </t>
3984    <t>
3985      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
3986      "TRACE security considerations"
3987    </t>
3988    <t>
3989      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
3990      "Clarify rules for determining what entities a response carries"
3991    </t>
3992    <t>
3993      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
3994      "update note citing RFC 1945 and 2068"
3995    </t>
3996    <t>
3997      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
3998      "update note about redirect limit"
3999    </t>
4000    <t>
4001      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
4002      "Location header ABNF should use 'URI'"
4003    </t>
4004    <t>
4005      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
4006      "fragments in Location vs status 303"
4007    </t>
4008    <t>
4009      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
4010      "move IANA registrations for optional status codes"
4011    </t>
4012  </list>
4013</t>
4014<t>
4015  Partly resolved issues:
4016  <list style="symbols"> 
4017    <t>
4018      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
4019      "Are OPTIONS and TRACE safe?"
4020    </t>
4021  </list>
4022</t>
4023</section>
4024
4025<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
4026<t>
4027  Closed issues:
4028  <list style="symbols"> 
4029    <t>
4030      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
4031      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
4032      status codes when fixing this previously)
4033    </t>
4034  </list>
4035</t>
4036</section>
4037
4038<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
4039<t>
4040  Closed issues:
4041  <list style="symbols"> 
4042    <t>
4043      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4044      "Fragment combination / precedence during redirects"
4045    </t>
4046  </list>
4047</t>
4048<t>
4049  Partly resolved issues:
4050  <list style="symbols"> 
4051    <t>
4052      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
4053      "Location header payload handling"
4054    </t>
4055    <t>
4056      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
4057      "Term for the requested resource's URI"
4058    </t>
4059  </list>
4060</t>
4061</section>
4062
4063<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
4064<t>
4065  Closed issues:
4066  <list style="symbols"> 
4067    <t>
4068      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
4069      "Clarify 'Requested Variant'"
4070    </t>
4071    <t>
4072      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
4073      "Clarify entity / representation / variant terminology"
4074    </t>
4075    <t>
4076      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/139"/>:
4077      "Methods and Caching"
4078    </t>
4079    <t>
4080      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/190"/>:
4081      "OPTIONS vs Max-Forwards"
4082    </t>
4083    <t>
4084      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/199"/>:
4085      "Status codes and caching"
4086    </t>
4087    <t>
4088      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
4089      "consider removing the 'changes from 2068' sections"
4090    </t>
4091  </list>
4092</t>
4093</section>
4094
4095<section title="Since draft-ietf-httpbis-p2-semantics-11" anchor="changes.since.11">
4096<t>
4097  Closed issues:
4098  <list style="symbols"> 
4099    <t>
4100      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/229"/>:
4101      "Considerations for new status codes"
4102    </t>
4103    <t>
4104      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/230"/>:
4105      "Considerations for new methods"
4106    </t>
4107    <t>
4108      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/232"/>:
4109      "User-Agent guidelines" (relating to the 'User-Agent' header field)
4110    </t>
4111  </list>
4112</t>
4113</section>
4114
4115<section title="Since draft-ietf-httpbis-p2-semantics-12" anchor="changes.since.12">
4116<t>
4117  Closed issues:
4118  <list style="symbols"> 
4119    <t>
4120      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4121      "Fragment combination / precedence during redirects" (added warning
4122      about having a fragid on the redirect may cause inconvenience in
4123      some cases)
4124    </t>
4125    <t>
4126      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/79"/>:
4127      "Content-* vs. PUT"
4128    </t>
4129    <t>
4130      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/88"/>:
4131      "205 Bodies"
4132    </t>
4133    <t>
4134      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/102"/>:
4135      "Understanding Content-* on non-PUT requests"
4136    </t>
4137    <t>
4138      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
4139      "Content-*"
4140    </t>
4141    <t>
4142      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/104"/>:
4143      "Header type defaulting"
4144    </t>
4145    <t>
4146      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
4147      "PUT - 'store under' vs 'store at'"
4148    </t>
4149    <t>
4150      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/137"/>:
4151      "duplicate ABNF for Reason-Phrase"
4152    </t>
4153    <t>
4154      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/180"/>:
4155      "Note special status of Content-* prefix in header registration procedures"
4156    </t>
4157    <t>
4158      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/203"/>:
4159      "Max-Forwards vs extension methods"
4160    </t>
4161    <t>
4162      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/213"/>:
4163      "What is the value space of HTTP status codes?" (actually fixed in
4164      draft-ietf-httpbis-p2-semantics-11)
4165    </t>
4166    <t>
4167      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/226"/>:
4168      "proxies not supporting certain methods"
4169    </t>
4170    <t>
4171      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/239"/>:
4172      "Migrate CONNECT from RFC2817 to p2"
4173    </t>
4174    <t>
4175      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/240"/>:
4176      "Migrate Upgrade details from RFC2817"
4177    </t>
4178    <t>
4179      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/225"/>:
4180      "PUT side effect: invalidation or just stale?"
4181    </t>
4182    <t>
4183      <eref target="http://trac.tools.ietf.org/wg/httpbis/trac/ticket/267"/>:
4184      "clarify PUT semantics'"
4185    </t>
4186    <t>
4187      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/275"/>:
4188      "duplicate ABNF for 'Method'"
4189    </t>
4190    <t>
4191      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/276"/>:
4192      "untangle ABNFs for header fields"
4193    </t>
4194  </list>
4195</t>
4196</section>
4197
4198</section>
4199
4200</back>
4201</rfc>
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