source: draft-ietf-httpbis/latest/p2-semantics.xml @ 1124

Last change on this file since 1124 was 1124, checked in by julian.reschke@…, 9 years ago

Restructure 'Status Code and Reason Phrase', replace ABNF listing all HTTP/1.1 status codes with an Overview table, remove some redundant text (see #137)

  • Property svn:eol-style set to native
File size: 170.4 KB
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1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD NOT</bcp14>">
14  <!ENTITY ID-VERSION "latest">
15  <!ENTITY ID-MONTH "February">
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, general header fields, methods, request modifiers, response
285   status, and resource metadata.  The current mess reflects how widely
286   dispersed these topics and associated requirements had become in
287   <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 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"/><iref primary="true" item="Grammar" subitem="extension-method"/>
436  <x:ref>Method</x:ref>         = <x:abnf-char-sequence>"OPTIONS"</x:abnf-char-sequence>   ; "OPTIONS", <xref target="OPTIONS"/>
437                 / <x:abnf-char-sequence>"GET"</x:abnf-char-sequence>               ; "GET", <xref target="GET"/>
438                 / <x:abnf-char-sequence>"HEAD"</x:abnf-char-sequence>            ; "HEAD", <xref target="HEAD"/>
439                 / <x:abnf-char-sequence>"POST"</x:abnf-char-sequence>            ; "POST", <xref target="POST"/>
440                 / <x:abnf-char-sequence>"PUT"</x:abnf-char-sequence>               ; "PUT", <xref target="PUT"/>
441                 / <x:abnf-char-sequence>"DELETE"</x:abnf-char-sequence>      ; "DELETE", <xref target="DELETE"/>
442                 / <x:abnf-char-sequence>"TRACE"</x:abnf-char-sequence>         ; "TRACE", <xref target="TRACE"/>
443                 / <x:abnf-char-sequence>"CONNECT"</x:abnf-char-sequence>   ; "CONNECT", <xref target="CONNECT"/>
444                 / <x:ref>extension-method</x:ref>
445  <x:ref>extension-method</x:ref> = <x:ref>token</x:ref>
446</artwork></figure>
447<t>
448   The list of methods allowed by a resource can be specified in an
449   Allow header field (<xref target="header.allow"/>). The status code of the response
450   always notifies the client whether a method is currently allowed on a
451   resource, since the set of allowed methods can change dynamically. An
452   origin server &SHOULD; respond with the status code 405 (Method Not Allowed)
453   if the method is known by the origin server but not allowed for the
454   resource, and 501 (Not Implemented) if the method is
455   unrecognized or not implemented by the origin server. The methods GET
456   and HEAD &MUST; be supported by all general-purpose servers. All other
457   methods are &OPTIONAL;; however, if the above methods are implemented,
458   they &MUST; be implemented with the same semantics as those specified
459   in <xref target="method.definitions"/>.
460</t>
461
462<section title="Method Registry" anchor="method.registry">
463<t>
464  The HTTP Method Registry defines the name space for the Method token in the
465  Request line of an HTTP request.
466</t>
467<t>
468  Registrations &MUST; include the following fields:
469  <list style="symbols">
470    <t>Method Name (see <xref target="method"/>)</t>
471    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
472    <t>Pointer to specification text</t>
473  </list>
474</t>
475<t>
476  Values to be added to this name space are subject to IETF review
477  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
478</t>
479<t>
480  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
481</t>
482
483<section title="Considerations for New Methods" anchor="considerations.for.new.methods">
484<t>
485   When it is necessary to express new semantics for a HTTP request that
486   aren't specific to a single application or media type, and currently defined
487   methods are inadequate, it may be appropriate to register a new method.
488</t>
489<t>
490   HTTP methods are generic; that is, they are potentially applicable to any
491   resource, not just one particular media type, "type" of resource, or
492   application. As such, it is preferred that new HTTP methods be registered
493   in a document that isn't specific to a single application, so that this is
494   clear.
495</t>
496<t>
497   Due to the parsing rules defined in &message-body;, definitions of HTTP
498   methods cannot prohibit the presence of a message-body on either the request
499   or the response message (with responses to HEAD requests being the single
500   exception). Definitions of new methods cannot change this rule, but they can
501   specify that only zero-length bodies (as opposed to absent bodies) are allowed.
502</t>
503<t>
504   New method definitions need to indicate whether they are safe (<xref
505   target="safe.methods"/>) and whether they are idempotent (<xref
506   target="idempotent.methods"/>). They also need to state whether they can be
507   cached (&caching;); in particular what conditions a cache may store the
508   response, and under what conditions such a stored response may be used to
509   satisfy a subsequent request.
510</t>
511</section>
512
513</section>
514</section>
515
516<section title="Request Header Fields" anchor="request.header.fields">
517  <x:anchor-alias value="request-header"/>
518<t>
519   The request-header fields allow the client to pass additional
520   information about the request, and about the client itself, to the
521   server. These fields act as request modifiers, with semantics
522   equivalent to the parameters on a programming language method
523   invocation.
524</t>
525<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
526  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
527                 / <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
528                 / <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
529                 / <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
530                 / <x:ref>Authorization</x:ref>            ; &header-authorization;
531                 / <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
532                 / <x:ref>From</x:ref>                     ; <xref target="header.from"/>
533                 / <x:ref>Host</x:ref>                     ; &header-host;
534                 / <x:ref>If-Match</x:ref>                 ; &header-if-match;
535                 / <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
536                 / <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
537                 / <x:ref>If-Range</x:ref>                 ; &header-if-range;
538                 / <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
539                 / <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
540                 / <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
541                 / <x:ref>Range</x:ref>                    ; &header-range;
542                 / <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
543                 / <x:ref>TE</x:ref>                       ; &header-te;
544                 / <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
545</artwork></figure>
546<t>
547   Request-header field names can be extended reliably only in
548   combination with a change in the protocol version. However, new or
549   experimental header fields &MAY; be given the semantics of request-header
550   fields if all parties in the communication recognize them to
551   be request-header fields.
552</t>
553</section>
554
555<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
556  <x:anchor-alias value="Reason-Phrase"/>
557  <x:anchor-alias value="Status-Code"/>
558  <x:anchor-alias value="extension-code"/>
559<t>
560   The Status-Code element is a 3-digit integer result code of the attempt to
561   understand and satisfy the request.
562</t>
563<t>
564   The Reason-Phrase is intended to give a short textual description of the
565   Status-Code and is intended for the human user. The client is not required
566   to examine or display the Reason-Phrase.
567</t>
568<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"/>
569  <x:ref>Status-Code</x:ref>    = 3<x:ref>DIGIT</x:ref>
570  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
571</artwork></figure>
572<t>
573   HTTP status codes are extensible. HTTP applications are not required
574   to understand the meaning of all registered status codes, though such
575   understanding is obviously desirable. However, applications &MUST;
576   understand the class of any status code, as indicated by the first
577   digit, and treat any unrecognized response as being equivalent to the
578   x00 status code of that class, with the exception that an
579   unrecognized response &MUST-NOT; be cached. For example, if an
580   unrecognized status code of 431 is received by the client, it can
581   safely assume that there was something wrong with its request and
582   treat the response as if it had received a 400 status code. In such
583   cases, user agents &SHOULD; present to the user the representation enclosed
584   with the response, since that representation is likely to include human-readable
585   information which will explain the unusual status.
586</t>
587
588<section title="Overview of Status Codes" anchor="overview.of.status.codes">
589<t> 
590   The status codes listed below are defined in <xref target="status.codes"/>,
591   &p4-status-codes;, &p5-status-codes;, and &p7-status-codes;. The reason
592   phrases listed here are only recommendations &mdash; they can be replaced
593   by local equivalents without affecting the protocol.
594</t>
595<texttable align="left">
596  <ttcol>Status-Code</ttcol>
597  <ttcol>Reason-Phrase</ttcol>
598  <ttcol>Defined in...</ttcol>
599 
600  <c>100</c> <c>Continue</c> <c><xref target="status.100"/></c>
601  <c>101</c> <c>Switching Protocols</c> <c><xref target="status.101"/></c>
602
603  <c>200</c> <c>OK</c> <c><xref target="status.200"/></c>
604  <c>201</c> <c>Created</c> <c><xref target="status.201"/></c>
605  <c>202</c> <c>Accepted</c> <c><xref target="status.202"/></c>
606  <c>203</c> <c>Non-Authoritative Information</c> <c><xref target="status.203"/></c>
607  <c>204</c> <c>No Content</c> <c><xref target="status.204"/></c>
608  <c>205</c> <c>Reset Content</c> <c><xref target="status.205"/></c>
609  <c>206</c> <c>Partial Content</c> <c>&status-206;</c>
610
611  <c>300</c> <c>Multiple Choices</c> <c><xref target="status.300"/></c>
612  <c>301</c> <c>Moved Permanently</c> <c><xref target="status.301"/></c>
613  <c>302</c> <c>Found</c> <c><xref target="status.302"/></c>
614  <c>303</c> <c>See Other</c> <c><xref target="status.303"/></c>
615  <c>304</c> <c>Not Modified</c> <c>&status-304;</c>
616  <c>305</c> <c>Use Proxy</c> <c><xref target="status.305"/></c>
617  <c>307</c> <c>Temporary Redirect</c> <c><xref target="status.307"/></c>
618
619  <c>400</c> <c>Bad Request</c> <c><xref target="status.400"/></c>
620  <c>401</c> <c>Unauthorized</c> <c>&status-401;</c>
621  <c>402</c> <c>Payment Required</c> <c><xref target="status.402"/></c>
622  <c>403</c> <c>Forbidden</c> <c><xref target="status.403"/></c>
623  <c>404</c> <c>Not Found</c> <c><xref target="status.404"/></c>
624  <c>405</c> <c>Method Not Allowed</c> <c><xref target="status.405"/></c>
625  <c>406</c> <c>Not Acceptable</c> <c><xref target="status.406"/></c>
626  <c>407</c> <c>Proxy Authentication Required</c> <c>&status-407;</c>
627  <c>408</c> <c>Request Time-out</c> <c><xref target="status.408"/></c>
628  <c>409</c> <c>Conflict</c> <c><xref target="status.409"/></c>
629  <c>410</c> <c>Gone</c> <c><xref target="status.410"/></c>
630  <c>411</c> <c>Length Required</c> <c><xref target="status.411"/></c>
631  <c>412</c> <c>Precondition Failed</c> <c>&status-412;</c>
632  <c>413</c> <c>Request Entity Too Large</c> <c><xref target="status.413"/></c>
633  <c>414</c> <c>URI Too Long</c> <c><xref target="status.414"/></c>
634  <c>415</c> <c>Unsupported Media Type</c> <c><xref target="status.415"/></c>
635  <c>416</c> <c>Requested range not satisfiable</c> <c>&status-416;</c>
636  <c>417</c> <c>Expectation Failed</c> <c><xref target="status.417"/></c>
637  <c>426</c> <c>Upgrade Required</c> <c><xref target="status.426"/></c>
638
639  <c>500</c> <c>Internal Server Error</c> <c><xref target="status.500"/></c>
640  <c>501</c> <c>Not Implemented</c> <c><xref target="status.501"/></c>
641  <c>502</c> <c>Bad Gateway</c> <c><xref target="status.502"/></c>
642  <c>503</c> <c>Service Unavailable</c> <c><xref target="status.503"/></c>
643  <c>504</c> <c>Gateway Time-out</c> <c><xref target="status.504"/></c>
644  <c>505</c> <c>HTTP Version not supported</c> <c><xref target="status.505"/></c>
645</texttable>
646<t>
647   Note that this list is not exhaustive &mdash; it does not include
648   extension status codes defined in other specifications.
649</t>
650</section>
651
652<section title="Status Code Registry" anchor="status.code.registry">
653<t>
654  The HTTP Status Code Registry defines the name space for the Status-Code
655  token in the Status-Line of an HTTP response.
656</t>
657<t>
658  Values to be added to this name space are subject to IETF review
659  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
660</t>
661<t>
662  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
663</t>
664
665<section title="Considerations for New Status Codes" anchor="considerations.for.new.status.codes">
666<t>
667   When it is necessary to express new semantics for a HTTP response that
668   aren't specific to a single application or media type, and currently defined
669   status codes are inadequate, a new status code can be registered.
670</t>
671<t>
672   HTTP status codes are generic; that is, they are potentially applicable to
673   any resource, not just one particular media type, "type" of resource, or
674   application. As such, it is preferred that new HTTP status codes be
675   registered in a document that isn't specific to a single application, so
676   that this is clear.
677</t>
678<t>
679   Definitions of new HTTP status codes typically explain the request
680   conditions that produce a response containing the status code (e.g.,
681   combinations of request headers and/or method(s)), along with any
682   interactions with response headers (e.g., those that are required, those
683   that modify the semantics of the response).
684</t>
685<t>
686   New HTTP status codes are required to fall under one of the categories
687   defined in <xref target="status.codes"/>. To allow existing parsers to
688   properly handle them, new status codes cannot disallow a response body,
689   although they can mandate a zero-length response body. They can require the
690   presence of one or more particular HTTP response header(s).
691</t>
692<t>
693   Likewise, their definitions can specify that caches are allowed to use
694   heuristics to determine their freshness (see &caching;; by default, it is
695   not allowed), and can define how to determine the resource which they
696   carry a representation for (see <xref
697   target="identifying.response.associated.with.representation"/>; by default,
698   it is anonymous).
699</t>
700</section>
701
702</section>
703
704</section>
705
706<section title="Response Header Fields" anchor="response.header.fields">
707  <x:anchor-alias value="response-header"/>
708<t>
709   The response-header fields allow the server to pass additional
710   information about the response which cannot be placed in the Status-Line.
711   These header fields give information about the server and about
712   further access to the target resource (&effective-request-uri;).
713</t>
714<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
715  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
716                  / <x:ref>Age</x:ref>                     ; &header-age;
717                  / <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
718                  / <x:ref>ETag</x:ref>                    ; &header-etag;
719                  / <x:ref>Location</x:ref>                ; <xref target="header.location"/>
720                  / <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
721                  / <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
722                  / <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
723                  / <x:ref>Vary</x:ref>                    ; &header-vary;
724                  / <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
725</artwork></figure>
726<t>
727   Response-header field names can be extended reliably only in
728   combination with a change in the protocol version. However, new or
729   experimental header fields &MAY; be given the semantics of response-header
730   fields if all parties in the communication recognize them to
731   be response-header fields.
732</t>
733</section>
734
735<section title="Representation" anchor="representation">
736<t>
737   Request and Response messages &MAY; transfer a representation if not otherwise
738   restricted by the request method or response status code. A representation
739   consists of metadata (representation header fields) and data (representation
740   body).  When a complete or partial representation is enclosed in an HTTP message,
741   it is referred to as the payload of the message. HTTP representations
742   are defined in &payload;.
743</t>
744<t>
745   A representation body is only present in a message when a message-body is
746   present, as described in &message-body;. The representation body is obtained
747   from the message-body by decoding any Transfer-Encoding that might
748   have been applied to ensure safe and proper transfer of the message.
749</t>
750
751<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
752<t>
753   It is sometimes necessary to determine an identifier for the resource
754   associated with a representation.
755</t>
756<t>
757   An HTTP request representation, when present, is always associated with an
758   anonymous (i.e., unidentified) resource.
759</t>
760<t>
761   In the common case, an HTTP response is a representation of the target
762   resource (see &effective-request-uri;). However, this is not always the
763   case. To determine the URI of the resource a response is associated with,
764   the following rules are used (with the first applicable one being selected):
765</t>
766<t><list style="numbers">
767   <t>If the response status code is 200 or 203 and the request method was GET,
768   the response payload is a representation of the target resource.</t>
769   <t>If the response status code is 204, 206, or 304 and the request method was GET
770   or HEAD, the response payload is a partial representation of the target
771   resource (see &combining-responses;).</t>
772   <t>If the response has a Content-Location header field, and that URI is the same
773   as the effective request URI, the response payload is a representation of the
774   target resource.</t>
775   <t>If the response has a Content-Location header field, and that URI is not the
776   same as the effective request URI, then the response asserts that its
777   payload is a representation of the resource identified by the
778   Content-Location URI. However, such an assertion cannot be trusted unless
779   it can be verified by other means (not defined by HTTP).</t>
780   <t>Otherwise, the response is a representation of an anonymous (i.e.,
781   unidentified) resource.</t>
782</list></t>
783<t>
784  <cref anchor="TODO-req-uri">
785   The comparison function is going to have to be defined somewhere,
786   because we already need to compare URIs for things like cache invalidation.</cref>
787</t>
788</section>
789
790</section>
791
792
793<section title="Method Definitions" anchor="method.definitions">
794<t>
795   The set of common methods for HTTP/1.1 is defined below. Although
796   this set can be expanded, additional methods cannot be assumed to
797   share the same semantics for separately extended clients and servers.
798</t>
799
800<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
801
802<section title="Safe Methods" anchor="safe.methods">
803<iref item="Safe Methods" primary="true"/>
804<t>
805   Implementors need to be aware that the software represents the user in
806   their interactions over the Internet, and need to allow
807   the user to be aware of any actions they take which might have an
808   unexpected significance to themselves or others.
809</t>
810<t>
811   In particular, the convention has been established that the GET, HEAD,
812   OPTIONS, and TRACE methods &SHOULD-NOT; have the significance of taking an action
813   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
814   This allows user agents to represent other methods, such as POST, PUT
815   and DELETE, in a special way, so that the user is made aware of the
816   fact that a possibly unsafe action is being requested.
817</t>
818<t>
819   Naturally, it is not possible to ensure that the server does not
820   generate side-effects as a result of performing a GET request; in
821   fact, some dynamic resources consider that a feature. The important
822   distinction here is that the user did not request the side-effects,
823   so therefore cannot be held accountable for them.
824</t>
825</section>
826
827<section title="Idempotent Methods" anchor="idempotent.methods">
828<iref item="Idempotent Methods" primary="true"/>
829<t>
830   Methods can also have the property of "idempotence" in that, aside
831   from error or expiration issues, the intended effect of multiple
832   identical requests is the same as for a single request.
833   The methods PUT, DELETE, and all safe methods are idempotent.
834   It is important to note that idempotence refers only to changes
835   requested by the client: a server is free to change its state due
836   to multiple requests for the purpose of tracking those requests,
837   versioning of results, etc.
838</t>
839</section>
840</section>
841
842<section title="OPTIONS" anchor="OPTIONS">
843  <rdf:Description>
844    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
845  </rdf:Description>
846  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
847  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
848<t>
849   The OPTIONS method represents a request for information about the
850   communication options available on the request/response chain
851   identified by the effective request URI. This method allows the client to
852   determine the options and/or requirements associated with a resource,
853   or the capabilities of a server, without implying a resource action
854   or initiating a resource retrieval.
855</t>
856<t>
857   Responses to this method are not cacheable.
858</t>
859<t>
860   If the OPTIONS request includes a message-body (as indicated by the
861   presence of Content-Length or Transfer-Encoding), then the media type
862   &MUST; be indicated by a Content-Type field. Although this
863   specification does not define any use for such a body, future
864   extensions to HTTP might use the OPTIONS body to make more detailed
865   queries on the server.
866</t>
867<t>
868   If the request-target is an asterisk ("*"), the OPTIONS request is
869   intended to apply to the server in general rather than to a specific
870   resource. Since a server's communication options typically depend on
871   the resource, the "*" request is only useful as a "ping" or "no-op"
872   type of method; it does nothing beyond allowing the client to test
873   the capabilities of the server. For example, this can be used to test
874   a proxy for HTTP/1.1 compliance (or lack thereof).
875</t>
876<t>
877   If the request-target is not an asterisk, the OPTIONS request applies
878   only to the options that are available when communicating with that
879   resource.
880</t>
881<t>
882   A 200 response &SHOULD; include any header fields that indicate
883   optional features implemented by the server and applicable to that
884   resource (e.g., Allow), possibly including extensions not defined by
885   this specification. The response body, if any, &SHOULD; also include
886   information about the communication options. The format for such a
887   body is not defined by this specification, but might be defined by
888   future extensions to HTTP. Content negotiation &MAY; be used to select
889   the appropriate response format. If no response body is included, the
890   response &MUST; include a Content-Length field with a field-value of
891   "0".
892</t>
893<t>
894   The Max-Forwards request-header field &MAY; be used to target a
895   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
896   If no Max-Forwards field is present in the request, then the forwarded
897   request &MUST-NOT; include a Max-Forwards field.
898</t>
899</section>
900
901<section title="GET" anchor="GET">
902  <rdf:Description>
903    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
904  </rdf:Description>
905  <iref primary="true" item="GET method" x:for-anchor=""/>
906  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
907<t>
908   The GET method means retrieve whatever information (in the form of a
909   representation) currently corresponds to the target resource.
910</t>
911<t>   
912   If the target resource is a data-producing process, it is the
913   produced data which shall be returned as the representation in the response and not
914   the source text of the process, unless that text happens to be the output of
915   the process.
916</t>
917<t>
918   The semantics of the GET method change to a "conditional GET" if the
919   request message includes an If-Modified-Since, If-Unmodified-Since,
920   If-Match, If-None-Match, or If-Range header field. A conditional GET
921   method requests that the representation be transferred only under the
922   circumstances described by the conditional header field(s). The
923   conditional GET method is intended to reduce unnecessary network
924   usage by allowing cached representations to be refreshed without requiring
925   multiple requests or transferring data already held by the client.
926</t>
927<t>
928   The semantics of the GET method change to a "partial GET" if the
929   request message includes a Range header field. A partial GET requests
930   that only part of the representation be transferred, as described in &header-range;.
931   The partial GET method is intended to reduce unnecessary
932   network usage by allowing partially-retrieved representations to be
933   completed without transferring data already held by the client.
934</t>
935<t>
936   The response to a GET request is cacheable and &MAY; be used to satisfy
937   subsequent GET and HEAD requests (see &caching;).
938</t>
939<t>
940   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
941</t>
942</section>
943
944<section title="HEAD" anchor="HEAD">
945  <rdf:Description>
946    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
947  </rdf:Description>
948  <iref primary="true" item="HEAD method" x:for-anchor=""/>
949  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
950<t>
951   The HEAD method is identical to GET except that the server &MUST-NOT;
952   return a message-body in the response. The metadata contained
953   in the HTTP header fields in response to a HEAD request &SHOULD; be identical
954   to the information sent in response to a GET request. This method can
955   be used for obtaining metadata about the representation implied by the
956   request without transferring the representation body. This method is
957   often used for testing hypertext links for validity, accessibility,
958   and recent modification.
959</t>
960<t>
961   The response to a HEAD request is cacheable and &MAY; be used to satisfy
962   a subsequent HEAD request; see &caching;. It also &MAY; be used to update a previously cached
963   representation from that resource; if the new field values
964   indicate that the cached representation differs from the current representation (as
965   would be indicated by a change in Content-Length, Content-MD5, ETag
966   or Last-Modified), then the cache &MUST; treat the cache entry as
967   stale.
968</t>
969</section>
970
971<section title="POST" anchor="POST">
972  <iref primary="true" item="POST method" x:for-anchor=""/>
973  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
974<t>
975   The POST method is used to request that the origin server accept the
976   representation enclosed in the request as data to be processed by the
977   target resource. POST is designed to allow a uniform method to cover the
978   following functions:
979  <list style="symbols">
980    <t>
981      Annotation of existing resources;
982    </t>
983    <t>
984        Posting a message to a bulletin board, newsgroup, mailing list,
985        or similar group of articles;
986    </t>
987    <t>
988        Providing a block of data, such as the result of submitting a
989        form, to a data-handling process;
990    </t>
991    <t>
992        Extending a database through an append operation.
993    </t>
994  </list>
995</t>
996<t>
997   The actual function performed by the POST method is determined by the
998   server and is usually dependent on the effective request URI.
999</t>
1000<t>
1001   The action performed by the POST method might not result in a
1002   resource that can be identified by a URI. In this case, either 200
1003   (OK) or 204 (No Content) is the appropriate response status code,
1004   depending on whether or not the response includes a representation that
1005   describes the result.
1006</t>
1007<t>
1008   If a resource has been created on the origin server, the response
1009   &SHOULD; be 201 (Created) and contain a representation which describes the
1010   status of the request and refers to the new resource, and a Location
1011   header field (see <xref target="header.location"/>).
1012</t>
1013<t>
1014   Responses to POST requests are only cacheable when they
1015   include explicit freshness information (see &p6-explicit;). A
1016   cached POST response with a Content-Location header field
1017   (see &header-content-location;) whose value is the effective
1018   Request URI &MAY; be used to satisfy subsequent GET and HEAD requests.
1019</t>
1020<t>
1021   Note that POST caching is not widely implemented.
1022   However, the 303 (See Other) response can be used to direct the
1023   user agent to retrieve a cacheable resource.
1024</t>
1025</section>
1026
1027<section title="PUT" anchor="PUT">
1028  <iref primary="true" item="PUT method" x:for-anchor=""/>
1029  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
1030<t>
1031   The PUT method requests that the enclosed representation be stored at the
1032   effective request URI. If the effective request URI refers to an already
1033   existing resource, the enclosed representation &SHOULD; be considered a
1034   modified version of the one residing on the origin server. Otherwise, if the
1035   effective request URI does not point to an existing resource, and that URI is
1036   capable of being defined as a new resource by the requesting user
1037   agent, the origin server can create the resource with that URI.
1038</t>
1039<t>   
1040   If a new resource is created at the effective request URI, the origin
1041   server &MUST; inform the user agent
1042   via the 201 (Created) response. If an existing resource is modified,
1043   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
1044   to indicate successful completion of the request.
1045</t>
1046<t>   
1047   If the target resource could not be created or modified, an appropriate
1048   error response &SHOULD; be given that reflects the nature of the problem.
1049   The recipient of the representation &MUST-NOT; ignore any Content-*
1050   header fields (headers starting with the prefix "Content-") that it does
1051   not understand or implement
1052   and &MUST; return a 501 (Not Implemented) response in such cases.
1053</t>
1054<t>
1055   Responses to the PUT method are not cacheable. If a PUT request passes
1056   through a cache that has one or more stored responses for the effective
1057   request URI, those stored responses will be invalidated (see
1058   &p6-invalid;).
1059</t>
1060<t>
1061   The fundamental difference between the POST and PUT requests is
1062   reflected in the different meaning of the effective request URI. The URI in a
1063   POST request identifies the resource that will handle the enclosed
1064   representation. That resource might be a data-accepting process, a gateway to
1065   some other protocol, or a document that accepts annotations.
1066   In contrast, the URI in a PUT request identifies the resource for
1067   which enclosed representation is a new or replacement value; the
1068   user agent knows what URI is intended and the server &MUST-NOT; attempt
1069   to apply the request to some other resource.
1070   If the server desires that the request be applied to a different URI,
1071   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
1072   then make its own decision regarding whether or not to redirect the
1073   request.
1074</t>
1075<t>
1076   A single resource &MAY; be identified by many different URIs. For
1077   example, an article might have a URI for identifying "the current
1078   version" which is separate from the URI identifying each particular
1079   version. In this case, a PUT request on a general URI might result in
1080   several other URIs being defined by the origin server.
1081</t>
1082<t>
1083   HTTP/1.1 does not define how a PUT method affects the state of an
1084   origin server.
1085</t>
1086<t>
1087   Header fields in a PUT request that are recognized as representation
1088   metadata &SHOULD; be applied to the resource created or modified by
1089   the PUT.  Unrecognized header fields &SHOULD; be ignored.
1090</t>
1091</section>
1092
1093<section title="DELETE" anchor="DELETE">
1094  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1095  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1096<t>
1097   The DELETE method requests that the origin server delete the target
1098   resource. This method &MAY; be overridden by
1099   human intervention (or other means) on the origin server. The client cannot
1100   be guaranteed that the operation has been carried out, even if the
1101   status code returned from the origin server indicates that the action
1102   has been completed successfully. However, the server &SHOULD-NOT; 
1103   indicate success unless, at the time the response is given, it
1104   intends to delete the resource or move it to an inaccessible
1105   location.
1106</t>
1107<t>
1108   A successful response &SHOULD; be 200 (OK) if the response includes an
1109   representation describing the status, 202 (Accepted) if the action has not
1110   yet been enacted, or 204 (No Content) if the action has been enacted
1111   but the response does not include a representation.
1112</t>
1113<t>
1114   Responses to the DELETE method are not cacheable. If a DELETE request
1115   passes through a cache that has one or more stored responses for the
1116   effective request URI, those stored responses will be invalidated (see
1117   &p6-invalid;).
1118</t>
1119</section>
1120
1121<section title="TRACE" anchor="TRACE">
1122  <rdf:Description>
1123    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1124  </rdf:Description>
1125  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1126  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1127<t>
1128   The TRACE method is used to invoke a remote, application-layer loop-back
1129   of the request message. The final recipient of the request
1130   &SHOULD; reflect the message received back to the client as the
1131   message-body of a 200 (OK) response. The final recipient is either the
1132   origin server or the first proxy or gateway to receive a Max-Forwards
1133   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1134   A TRACE request &MUST-NOT; include a message-body.
1135</t>
1136<t>
1137   TRACE allows the client to see what is being received at the other
1138   end of the request chain and use that data for testing or diagnostic
1139   information. The value of the Via header field (&header-via;) is of
1140   particular interest, since it acts as a trace of the request chain.
1141   Use of the Max-Forwards header field allows the client to limit the
1142   length of the request chain, which is useful for testing a chain of
1143   proxies forwarding messages in an infinite loop.
1144</t>
1145<t>
1146   If the request is valid, the response &SHOULD; have a Content-Type of
1147   "message/http" (see &media-type-message-http;) and contain a message-body
1148   that encloses a copy of the entire request message.
1149   Responses to the TRACE method are not cacheable.
1150</t>
1151</section>
1152
1153<section title="CONNECT" anchor="CONNECT">
1154  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1155  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1156<t>
1157   The CONNECT method is used with a proxy to dynamically switch
1158   the connection to a tunnel.
1159</t>
1160<t>
1161   When using CONNECT, the request-target &MUST; be use the authority form
1162   (&request-target;); i.e., the host name and port number destination of the
1163   requested connection separated by a colon:
1164</t>
1165<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1166CONNECT server.example.com:80 HTTP/1.1
1167Host: server.example.com:80
1168
1169</artwork></figure>
1170<t>
1171   Other HTTP mechanisms can be used normally with the CONNECT method &mdash;
1172   except end-to-end protocol Upgrade requests, since the
1173   tunnel must be established first.
1174</t>
1175<t>
1176   For example, proxy authentication might be used to establish the
1177   authority to create a tunnel:
1178</t>
1179<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1180CONNECT server.example.com:80 HTTP/1.1
1181Host: server.example.com:80
1182Proxy-Authorization: basic aGVsbG86d29ybGQ=
1183
1184</artwork></figure>
1185<t>
1186   Like any other pipelined HTTP/1.1 request, data to be tunnel may be
1187   sent immediately after the blank line. The usual caveats also apply:
1188   data may be discarded if the eventual response is negative, and the
1189   connection may be reset with no response if more than one TCP segment
1190   is outstanding.
1191</t>
1192
1193<section title="Establishing a Tunnel with CONNECT">
1194<t>
1195   Any successful (2xx) response to a CONNECT request indicates that the
1196   proxy has established a connection to the requested host and port,
1197   and has switched to tunneling the current connection to that server
1198   connection.
1199</t>
1200<t>
1201   It may be the case that the proxy itself can only reach the requested
1202   origin server through another proxy.  In this case, the first proxy
1203   &SHOULD; make a CONNECT request of that next proxy, requesting a tunnel
1204   to the authority.  A proxy &MUST-NOT; respond with any 2xx status code
1205   unless it has either a direct or tunnel connection established to the
1206   authority.
1207</t>
1208<t>
1209   An origin server which receives a CONNECT request for itself &MAY;
1210   respond with a 2xx status code to indicate that a connection is
1211   established.
1212</t>
1213<t>
1214   If at any point either one of the peers gets disconnected, any
1215   outstanding data that came from that peer will be passed to the other
1216   one, and after that also the other connection will be terminated by
1217   the proxy. If there is outstanding data to that peer undelivered,
1218   that data will be discarded.
1219</t>
1220
1221</section>
1222</section>
1223</section>
1224
1225
1226<section title="Status Code Definitions" anchor="status.codes">
1227<t>
1228   Each Status-Code is described below, including any metadata required
1229   in the response.
1230</t>
1231
1232<section title="Informational 1xx" anchor="status.1xx">
1233<t>
1234   This class of status code indicates a provisional response,
1235   consisting only of the Status-Line and optional header fields, and is
1236   terminated by an empty line. There are no required header fields for this
1237   class of status code. Since HTTP/1.0 did not define any 1xx status
1238   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1239   except under experimental conditions.
1240</t>
1241<t>
1242   A client &MUST; be prepared to accept one or more 1xx status responses
1243   prior to a regular response, even if the client does not expect a 100
1244   (Continue) status message. Unexpected 1xx status responses &MAY; be
1245   ignored by a user agent.
1246</t>
1247<t>
1248   Proxies &MUST; forward 1xx responses, unless the connection between the
1249   proxy and its client has been closed, or unless the proxy itself
1250   requested the generation of the 1xx response. (For example, if a
1251   proxy adds a "Expect: 100-continue" field when it forwards a request,
1252   then it need not forward the corresponding 100 (Continue)
1253   response(s).)
1254</t>
1255
1256<section title="100 Continue" anchor="status.100">
1257  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1258  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1259<t>
1260   The client &SHOULD; continue with its request. This interim response is
1261   used to inform the client that the initial part of the request has
1262   been received and has not yet been rejected by the server. The client
1263   &SHOULD; continue by sending the remainder of the request or, if the
1264   request has already been completed, ignore this response. The server
1265   &MUST; send a final response after the request has been completed. See
1266   &use100; for detailed discussion of the use and handling of this
1267   status code.
1268</t>
1269</section>
1270
1271<section title="101 Switching Protocols" anchor="status.101">
1272  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1273  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1274<t>
1275   The server understands and is willing to comply with the client's
1276   request, via the Upgrade message header field (&header-upgrade;), for a
1277   change in the application protocol being used on this connection. The
1278   server will switch protocols to those defined by the response's
1279   Upgrade header field immediately after the empty line which
1280   terminates the 101 response.
1281</t>
1282<t>
1283   The protocol &SHOULD; be switched only when it is advantageous to do
1284   so. For example, switching to a newer version of HTTP is advantageous
1285   over older versions, and switching to a real-time, synchronous
1286   protocol might be advantageous when delivering resources that use
1287   such features.
1288</t>
1289</section>
1290</section>
1291
1292<section title="Successful 2xx" anchor="status.2xx">
1293<t>
1294   This class of status code indicates that the client's request was
1295   successfully received, understood, and accepted.
1296</t>
1297
1298<section title="200 OK" anchor="status.200">
1299  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1300  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1301<t>
1302   The request has succeeded. The payload returned with the response
1303   is dependent on the method used in the request, for example:
1304  <list style="hanging">
1305    <t hangText="GET">
1306          a representation of the target resource is sent in the response;
1307    </t>
1308    <t hangText="HEAD">
1309          the same representation as GET, except without the message-body;
1310    </t>
1311    <t hangText="POST">
1312      a representation describing or containing the result of the action;
1313    </t>
1314    <t hangText="TRACE">
1315      a representation containing the request message as received by the
1316      end server.
1317    </t>
1318  </list>
1319</t>
1320<t>
1321   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1322   freshness for 200 responses.
1323</t>
1324</section>
1325
1326<section title="201 Created" anchor="status.201">
1327  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1328  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1329<t>
1330   The request has been fulfilled and has resulted in a new resource being
1331   created. The newly created resource can be referenced by the URI(s)
1332   returned in the payload of the response, with the most specific URI
1333   for the resource given by a Location header field. The response
1334   &SHOULD; include a payload containing a list of resource
1335   characteristics and location(s) from which the user or user agent can
1336   choose the one most appropriate. The payload format is specified by
1337   the media type given in the Content-Type header field. The origin
1338   server &MUST; create the resource before returning the 201 status code.
1339   If the action cannot be carried out immediately, the server &SHOULD;
1340   respond with 202 (Accepted) response instead.
1341</t>
1342<t>
1343   A 201 response &MAY; contain an ETag response header field indicating
1344   the current value of the entity-tag for the representation of the resource
1345   just created (see &header-etag;).
1346</t>
1347</section>
1348
1349<section title="202 Accepted" anchor="status.202">
1350  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1351  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1352<t>
1353   The request has been accepted for processing, but the processing has
1354   not been completed.  The request might or might not eventually be
1355   acted upon, as it might be disallowed when processing actually takes
1356   place. There is no facility for re-sending a status code from an
1357   asynchronous operation such as this.
1358</t>
1359<t>
1360   The 202 response is intentionally non-committal. Its purpose is to
1361   allow a server to accept a request for some other process (perhaps a
1362   batch-oriented process that is only run once per day) without
1363   requiring that the user agent's connection to the server persist
1364   until the process is completed. The representation returned with this
1365   response &SHOULD; include an indication of the request's current status
1366   and either a pointer to a status monitor or some estimate of when the
1367   user can expect the request to be fulfilled.
1368</t>
1369</section>
1370
1371<section title="203 Non-Authoritative Information" anchor="status.203">
1372  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1373  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1374<t>
1375   The returned metadata in the header fields is not the
1376   definitive set as available from the origin server, but is gathered
1377   from a local or a third-party copy. The set presented &MAY; be a subset
1378   or superset of the original version. For example, including local
1379   annotation information about the resource might result in a superset
1380   of the metadata known by the origin server. Use of this
1381   response code is not required and is only appropriate when the
1382   response would otherwise be 200 (OK).
1383</t>
1384<t>
1385   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1386   freshness for 203 responses.
1387</t>
1388
1389</section>
1390
1391<section title="204 No Content" anchor="status.204">
1392  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1393  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1394<t>
1395   The server has successfully fulfilled the request, but there is no
1396   additional content to return in the response payload body.  The
1397   resource metadata and representation metadata in the response message's
1398   header fields refer to the target resource
1399   and its current representation, respectively, after the requested action.
1400   For example, if a 204 status code is received in response to a PUT
1401   and the response contains an ETag header field, then the value of
1402   that field is the current entity-tag for the representation that
1403   was successfully PUT.
1404</t>
1405<t>
1406   If the client is a user agent, it &SHOULD-NOT; change its document view
1407   from that which caused the request to be sent. This response is
1408   primarily intended to allow input for actions to take place without
1409   causing a change to the user agent's active document view, although
1410   any new or updated metadata &SHOULD; be applied to the document
1411   currently in the user agent's active view.
1412</t>
1413<t>
1414   The 204 response &MUST-NOT; include a message-body, and thus is always
1415   terminated by the first empty line after the header fields.
1416</t>
1417</section>
1418
1419<section title="205 Reset Content" anchor="status.205">
1420  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1421  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1422<t>
1423   The server has fulfilled the request and the user agent &SHOULD; reset
1424   the document view which caused the request to be sent. This response
1425   is primarily intended to allow input for actions to take place via
1426   user input, followed by a clearing of the form in which the input is
1427   given so that the user can easily initiate another input action.
1428</t>
1429<t>   
1430   The message-body included with the response &MUST; be empty. Note that
1431   receivers still need to parse the response according to the algorithm defined
1432   in &message-body;.
1433</t>
1434</section>
1435
1436<section title="206 Partial Content" anchor="status.206">
1437  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1438  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1439  <rdf:Description>
1440    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1441  </rdf:Description>
1442<t>
1443   The server has fulfilled the partial GET request for the resource
1444   and the enclosed payload is a partial representation as defined in &status-206;.
1445</t>
1446<t>
1447   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1448   freshness for 206 responses.
1449</t>
1450</section>
1451</section>
1452
1453<section title="Redirection 3xx" anchor="status.3xx">
1454<t>
1455   This class of status code indicates that further action needs to be
1456   taken by the user agent in order to fulfill the request.  The action
1457   required &MAY; be carried out by the user agent without interaction
1458   with the user if and only if the method used in the second request is
1459   known to be "safe", as defined in <xref target="safe.methods"/>.
1460   A client &SHOULD; detect infinite redirection loops, since such loops
1461   generate network traffic for each redirection.
1462</t>
1463<x:note>
1464  <t>
1465    <x:h>Note:</x:h> An earlier version of this specification recommended a
1466    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1467    Content developers need to be aware that some clients might
1468    implement such a fixed limitation.
1469  </t>
1470</x:note>
1471
1472<section title="300 Multiple Choices" anchor="status.300">
1473  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1474  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1475<t>
1476   The target resource has more than one
1477   representation, each with its own specific location, and agent-driven
1478   negotiation information (&content-negotiation;) is being provided so that
1479   the user (or user agent) can select a preferred representation by
1480   redirecting its request to that location.
1481</t>
1482<t>
1483   Unless it was a HEAD request, the response &SHOULD; include a representation
1484   containing a list of representation metadata and location(s) from
1485   which the user or user agent can choose the one most appropriate. The
1486   data format is specified by the media type given in the Content-Type
1487   header field. Depending upon the format and the capabilities of
1488   the user agent, selection of the most appropriate choice &MAY; be
1489   performed automatically. However, this specification does not define
1490   any standard for such automatic selection.
1491</t>
1492<t>
1493   If the server has a preferred choice of representation, it &SHOULD;
1494   include the specific URI for that representation in the Location
1495   field; user agents &MAY; use the Location field value for automatic
1496   redirection.
1497</t>
1498<t>
1499   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1500   freshness for 300 responses.
1501</t>
1502
1503</section>
1504
1505<section title="301 Moved Permanently" anchor="status.301">
1506  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1507  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1508<t>
1509   The target resource has been assigned a new permanent URI and any
1510   future references to this resource &SHOULD; use one of the returned
1511   URIs.  Clients with link editing capabilities ought to automatically
1512   re-link references to the effective request URI to one or more of the new
1513   references returned by the server, where possible.
1514</t>
1515<t>
1516   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1517   freshness for 301 responses.
1518</t>
1519<t>
1520   The new permanent URI &SHOULD; be given by the Location field in the
1521   response. Unless the request method was HEAD, the representation of the
1522   response &SHOULD; contain a short hypertext note with a hyperlink to
1523   the new URI(s).
1524</t>
1525<t>
1526   If the 301 status code is received in response to a request method
1527   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1528   then the request &MAY; be automatically redirected by the user agent without
1529   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1530   request unless it can be confirmed by the user, since this might
1531   change the conditions under which the request was issued.
1532</t>
1533<x:note>
1534  <t>
1535    <x:h>Note:</x:h> When automatically redirecting a POST request after
1536    receiving a 301 status code, some existing HTTP/1.0 user agents
1537    will erroneously change it into a GET request.
1538  </t>
1539</x:note>
1540</section>
1541
1542<section title="302 Found" anchor="status.302">
1543  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1544  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1545<t>
1546   The target resource resides temporarily under a different URI.
1547   Since the redirection might be altered on occasion, the client &SHOULD;
1548   continue to use the effective request URI for future requests.
1549</t>
1550<t>
1551   The temporary URI &SHOULD; be given by the Location field in the
1552   response. Unless the request method was HEAD, the representation of the
1553   response &SHOULD; contain a short hypertext note with a hyperlink to
1554   the new URI(s).
1555</t>
1556<t>
1557   If the 302 status code is received in response to a request method
1558   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1559   then the request &MAY; be automatically redirected by the user agent without
1560   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1561   request unless it can be confirmed by the user, since this might
1562   change the conditions under which the request was issued.
1563</t>
1564<x:note>
1565  <t>
1566    <x:h>Note:</x:h> HTTP/1.0 (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>)
1567    and the first version of HTTP/1.1 (<xref target="RFC2068" x:fmt="," x:sec ="10.3.3"/>)
1568    specify that the client is not allowed to change the method on the
1569    redirected request.  However, most existing user agent implementations
1570    treat 302 as if it were a 303 response, performing a GET on the Location
1571    field-value regardless of the original request method. Therefore, a
1572    previous version of this specification
1573    (<xref target="RFC2616" x:fmt="," x:sec="10.3.3"/>) has added the
1574    status codes
1575    <xref target="status.303" format="none">303</xref> and
1576    <xref target="status.307" format="none">307</xref> for servers that wish
1577    to make unambiguously clear which kind of reaction is expected of the
1578    client.
1579  </t>
1580</x:note>
1581</section>
1582
1583<section title="303 See Other" anchor="status.303">
1584  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1585  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1586<t>
1587   The server directs the user agent to a different resource, indicated
1588   by a URI in the Location header field, that provides an indirect
1589   response to the original request.  The user agent &MAY; perform a GET
1590   request on the URI in the Location field in order to obtain a
1591   representation corresponding to the response, be redirected again,
1592   or end with an error status.  The Location URI is not a substitute
1593   reference for the effective request URI.
1594</t>
1595<t>
1596   The 303 status code is generally applicable to any HTTP method.  It is
1597   primarily used to allow the output of a POST action to redirect
1598   the user agent to a selected resource, since doing so provides the
1599   information corresponding to the POST response in a form that
1600   can be separately identified, bookmarked, and cached independent
1601   of the original request.
1602</t>
1603<t>
1604   A 303 response to a GET request indicates that the requested
1605   resource does not have a representation of its own that can be
1606   transferred by the server over HTTP.  The Location URI indicates a
1607   resource that is descriptive of the target resource, such that the
1608   follow-on representation might be useful to recipients without
1609   implying that it adequately represents the target resource.
1610   Note that answers to the questions of what can be represented, what
1611   representations are adequate, and what might be a useful description
1612   are outside the scope of HTTP and thus entirely determined by the
1613   URI owner(s).
1614</t>
1615<t>
1616   Except for responses to a HEAD request, the representation of a 303
1617   response &SHOULD; contain a short hypertext note with a hyperlink
1618   to the Location URI.
1619</t>
1620</section>
1621
1622<section title="304 Not Modified" anchor="status.304">
1623  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1624  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1625  <rdf:Description>
1626    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1627  </rdf:Description>
1628<t>
1629   The response to the request has not been modified since the conditions
1630   indicated by the client's conditional GET request, as defined in &status-304;.
1631</t>
1632</section>
1633
1634<section title="305 Use Proxy" anchor="status.305">
1635  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1636  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1637<t>
1638   The 305 status code was defined in a previous version of this specification
1639   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1640</t>
1641</section>
1642
1643<section title="306 (Unused)" anchor="status.306">
1644  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1645  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1646<t>
1647   The 306 status code was used in a previous version of the
1648   specification, is no longer used, and the code is reserved.
1649</t>
1650</section>
1651
1652<section title="307 Temporary Redirect" anchor="status.307">
1653  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1654  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1655<t>
1656   The target resource resides temporarily under a different URI.
1657   Since the redirection can change over time, the client &SHOULD;
1658   continue to use the effective request URI for future requests.
1659</t>
1660<t>
1661   The temporary URI &SHOULD; be given by the Location field in the
1662   response. Unless the request method was HEAD, the representation of the
1663   response &SHOULD; contain a short hypertext note with a hyperlink to
1664   the new URI(s), since many pre-HTTP/1.1 user agents do not
1665   understand the 307 status code. Therefore, the note &SHOULD; contain the
1666   information necessary for a user to repeat the original request on
1667   the new URI.
1668</t>
1669<t>
1670   If the 307 status code is received in response to a request method
1671   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1672   then the request &MAY; be automatically redirected by the user agent without
1673   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1674   request unless it can be confirmed by the user, since this might
1675   change the conditions under which the request was issued.
1676</t>
1677</section>
1678</section>
1679
1680<section title="Client Error 4xx" anchor="status.4xx">
1681<t>
1682   The 4xx class of status code is intended for cases in which the
1683   client seems to have erred. Except when responding to a HEAD request,
1684   the server &SHOULD; include a representation containing an explanation of the
1685   error situation, and whether it is a temporary or permanent
1686   condition. These status codes are applicable to any request method.
1687   User agents &SHOULD; display any included representation to the user.
1688</t>
1689<t>
1690   If the client is sending data, a server implementation using TCP
1691   &SHOULD; be careful to ensure that the client acknowledges receipt of
1692   the packet(s) containing the response, before the server closes the
1693   input connection. If the client continues sending data to the server
1694   after the close, the server's TCP stack will send a reset packet to
1695   the client, which might erase the client's unacknowledged input buffers
1696   before they can be read and interpreted by the HTTP application.
1697</t>
1698
1699<section title="400 Bad Request" anchor="status.400">
1700  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1701  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1702<t>
1703   The request could not be understood by the server due to malformed
1704   syntax. The client &SHOULD-NOT; repeat the request without
1705   modifications.
1706</t>
1707</section>
1708
1709<section title="401 Unauthorized" anchor="status.401">
1710  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1711  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1712  <rdf:Description>
1713    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1714  </rdf:Description>
1715<t>
1716   The request requires user authentication (see &status-401;).
1717</t>
1718</section>
1719
1720<section title="402 Payment Required" anchor="status.402">
1721  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1722  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1723<t>
1724   This code is reserved for future use.
1725</t>
1726</section>
1727
1728<section title="403 Forbidden" anchor="status.403">
1729  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1730  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1731<t>
1732   The server understood the request, but is refusing to fulfill it.
1733   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1734   If the request method was not HEAD and the server wishes to make
1735   public why the request has not been fulfilled, it &SHOULD; describe the
1736   reason for the refusal in the representation.  If the server does not wish to
1737   make this information available to the client, the status code 404
1738   (Not Found) can be used instead.
1739</t>
1740</section>
1741
1742<section title="404 Not Found" anchor="status.404">
1743  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1744  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1745<t>
1746   The server has not found anything matching the effective request URI. No
1747   indication is given of whether the condition is temporary or
1748   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1749   knows, through some internally configurable mechanism, that an old
1750   resource is permanently unavailable and has no forwarding address.
1751   This status code is commonly used when the server does not wish to
1752   reveal exactly why the request has been refused, or when no other
1753   response is applicable.
1754</t>
1755</section>
1756
1757<section title="405 Method Not Allowed" anchor="status.405">
1758  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1759  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1760<t>
1761   The method specified in the Request-Line is not allowed for the target
1762   resource. The response &MUST; include an
1763   Allow header field containing a list of valid methods for the requested
1764   resource.
1765</t>
1766</section>
1767
1768<section title="406 Not Acceptable" anchor="status.406">
1769  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1770  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1771<t>
1772   The resource identified by the request is only capable of generating
1773   response representations which have content characteristics not acceptable
1774   according to the accept header fields sent in the request.
1775</t>
1776<t>
1777   Unless it was a HEAD request, the response &SHOULD; include a representation
1778   containing a list of available representation characteristics and location(s)
1779   from which the user or user agent can choose the one most
1780   appropriate. The data format is specified by the media type given
1781   in the Content-Type header field. Depending upon the format and the
1782   capabilities of the user agent, selection of the most appropriate
1783   choice &MAY; be performed automatically. However, this specification
1784   does not define any standard for such automatic selection.
1785</t>
1786<x:note>
1787  <t>
1788    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1789    not acceptable according to the accept header fields sent in the
1790    request. In some cases, this might even be preferable to sending a
1791    406 response. User agents are encouraged to inspect the header fields of
1792    an incoming response to determine if it is acceptable.
1793  </t>
1794</x:note>
1795<t>
1796   If the response could be unacceptable, a user agent &SHOULD;
1797   temporarily stop receipt of more data and query the user for a
1798   decision on further actions.
1799</t>
1800</section>
1801
1802<section title="407 Proxy Authentication Required" anchor="status.407">
1803  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1804  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1805<t>
1806   This code is similar to 401 (Unauthorized), but indicates that the
1807   client must first authenticate itself with the proxy (see &status-407;).
1808</t>
1809</section>
1810
1811<section title="408 Request Timeout" anchor="status.408">
1812  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1813  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1814<t>
1815   The client did not produce a request within the time that the server
1816   was prepared to wait. The client &MAY; repeat the request without
1817   modifications at any later time.
1818</t>
1819</section>
1820
1821<section title="409 Conflict" anchor="status.409">
1822  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1823  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1824<t>
1825   The request could not be completed due to a conflict with the current
1826   state of the resource. This code is only allowed in situations where
1827   it is expected that the user might be able to resolve the conflict
1828   and resubmit the request. The response body &SHOULD; include enough
1829   information for the user to recognize the source of the conflict.
1830   Ideally, the response representation would include enough information for the
1831   user or user agent to fix the problem; however, that might not be
1832   possible and is not required.
1833</t>
1834<t>
1835   Conflicts are most likely to occur in response to a PUT request. For
1836   example, if versioning were being used and the representation being PUT
1837   included changes to a resource which conflict with those made by an
1838   earlier (third-party) request, the server might use the 409 response
1839   to indicate that it can't complete the request. In this case, the
1840   response representation would likely contain a list of the differences
1841   between the two versions in a format defined by the response
1842   Content-Type.
1843</t>
1844</section>
1845
1846<section title="410 Gone" anchor="status.410">
1847  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1848  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1849<t>
1850   The target resource is no longer available at the server and no
1851   forwarding address is known. This condition is expected to be
1852   considered permanent. Clients with link editing capabilities &SHOULD;
1853   delete references to the effective request URI after user approval. If the
1854   server does not know, or has no facility to determine, whether or not
1855   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1856   used instead.
1857</t>
1858<t>
1859   The 410 response is primarily intended to assist the task of web
1860   maintenance by notifying the recipient that the resource is
1861   intentionally unavailable and that the server owners desire that
1862   remote links to that resource be removed. Such an event is common for
1863   limited-time, promotional services and for resources belonging to
1864   individuals no longer working at the server's site. It is not
1865   necessary to mark all permanently unavailable resources as "gone" or
1866   to keep the mark for any length of time &mdash; that is left to the
1867   discretion of the server owner.
1868</t>
1869<t>
1870   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine freshness
1871   for 410 responses.
1872</t>
1873
1874</section>
1875
1876<section title="411 Length Required" anchor="status.411">
1877  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1878  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1879<t>
1880   The server refuses to accept the request without a defined Content-Length.
1881   The client &MAY; repeat the request if it adds a valid
1882   Content-Length header field containing the length of the message-body
1883   in the request message.
1884</t>
1885</section>
1886
1887<section title="412 Precondition Failed" anchor="status.412">
1888  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1889  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1890  <rdf:Description>
1891    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1892  </rdf:Description>
1893<t>
1894   The precondition given in one or more of the request-header fields
1895   evaluated to false when it was tested on the server, as defined in
1896   &status-412;.
1897</t>
1898</section>
1899
1900<section title="413 Request Entity Too Large" anchor="status.413">
1901  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1902  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1903<t>
1904   The server is refusing to process a request because the request
1905   representation is larger than the server is willing or able to process. The
1906   server &MAY; close the connection to prevent the client from continuing
1907   the request.
1908</t>
1909<t>
1910   If the condition is temporary, the server &SHOULD; include a Retry-After
1911   header field to indicate that it is temporary and after what
1912   time the client &MAY; try again.
1913</t>
1914</section>
1915
1916<section title="414 URI Too Long" anchor="status.414">
1917  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
1918  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
1919<t>
1920   The server is refusing to service the request because the effective request URI
1921   is longer than the server is willing to interpret. This rare
1922   condition is only likely to occur when a client has improperly
1923   converted a POST request to a GET request with long query
1924   information, when the client has descended into a URI "black hole" of
1925   redirection (e.g., a redirected URI prefix that points to a suffix of
1926   itself), or when the server is under attack by a client attempting to
1927   exploit security holes present in some servers using fixed-length
1928   buffers for reading or manipulating the effective request URI.
1929</t>
1930</section>
1931
1932<section title="415 Unsupported Media Type" anchor="status.415">
1933  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1934  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1935<t>
1936   The server is refusing to service the request because the representation of
1937   the request is in a format not supported by the target resource
1938   for the requested method.
1939</t>
1940</section>
1941
1942<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1943  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1944  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1945  <rdf:Description>
1946    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1947  </rdf:Description>
1948<t>
1949   The request included a Range request-header field (&header-range;) and none of
1950   the range-specifier values in this field overlap the current extent
1951   of the selected resource. See &status-416;.
1952</t>
1953</section>
1954
1955<section title="417 Expectation Failed" anchor="status.417">
1956  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1957  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1958<t>
1959   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1960   could not be met by this server, or, if the server is a proxy,
1961   the server has unambiguous evidence that the request could not be met
1962   by the next-hop server.
1963</t>
1964</section>
1965
1966<section title="426 Upgrade Required" anchor="status.426">
1967  <iref primary="true" item="426 Upgrade Required (status code)" x:for-anchor=""/>
1968  <iref primary="true" item="Status Codes" subitem="426 Upgrade Required" x:for-anchor=""/>
1969<t>
1970   The request can not be completed without a prior protocol upgrade. This
1971   response &MUST; include an Upgrade header field (&header-upgrade;)
1972   specifying the required protocols.
1973</t>
1974<figure>
1975<preamble>Example:</preamble>
1976<artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1977HTTP/1.1 426 Upgrade Required
1978Upgrade: HTTP/2.0
1979Connection: Upgrade
1980
1981</artwork></figure>
1982<t>
1983   The server &SHOULD; include a message body in the 426 response which
1984   indicates in human readable form the reason for the error and describes any
1985   alternative courses which may be available to the user.
1986</t>
1987</section>
1988</section>
1989
1990<section title="Server Error 5xx" anchor="status.5xx">
1991<t>
1992   Response status codes beginning with the digit "5" indicate cases in
1993   which the server is aware that it has erred or is incapable of
1994   performing the request. Except when responding to a HEAD request, the
1995   server &SHOULD; include a representation containing an explanation of the
1996   error situation, and whether it is a temporary or permanent
1997   condition. User agents &SHOULD; display any included representation to the
1998   user. These response codes are applicable to any request method.
1999</t>
2000
2001<section title="500 Internal Server Error" anchor="status.500">
2002  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
2003  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
2004<t>
2005   The server encountered an unexpected condition which prevented it
2006   from fulfilling the request.
2007</t>
2008</section>
2009
2010<section title="501 Not Implemented" anchor="status.501">
2011  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
2012  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
2013<t>
2014   The server does not support the functionality required to fulfill the
2015   request. This is the appropriate response when the server does not
2016   recognize the request method and is not capable of supporting it for
2017   any resource.
2018</t>
2019</section>
2020
2021<section title="502 Bad Gateway" anchor="status.502">
2022  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
2023  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
2024<t>
2025   The server, while acting as a gateway or proxy, received an invalid
2026   response from the upstream server it accessed in attempting to
2027   fulfill the request.
2028</t>
2029</section>
2030
2031<section title="503 Service Unavailable" anchor="status.503">
2032  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
2033  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
2034<t>
2035   The server is currently unable to handle the request due to a
2036   temporary overloading or maintenance of the server. The implication
2037   is that this is a temporary condition which will be alleviated after
2038   some delay. If known, the length of the delay &MAY; be indicated in a
2039   Retry-After header field. If no Retry-After is given, the client &SHOULD;
2040   handle the response as it would for a 500 response.
2041</t>
2042<x:note>
2043  <t>
2044    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
2045    server must use it when becoming overloaded. Some servers might wish
2046    to simply refuse the connection.
2047  </t>
2048</x:note>
2049</section>
2050
2051<section title="504 Gateway Timeout" anchor="status.504">
2052  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
2053  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
2054<t>
2055   The server, while acting as a gateway or proxy, did not receive a
2056   timely response from the upstream server specified by the URI (e.g.,
2057   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
2058   to access in attempting to complete the request.
2059</t>
2060<x:note>
2061  <t>
2062    <x:h>Note</x:h> to implementors: some deployed proxies are known to
2063    return 400 or 500 when DNS lookups time out.
2064  </t>
2065</x:note>
2066</section>
2067
2068<section title="505 HTTP Version Not Supported" anchor="status.505">
2069  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
2070  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
2071<t>
2072   The server does not support, or refuses to support, the protocol
2073   version that was used in the request message. The server is
2074   indicating that it is unable or unwilling to complete the request
2075   using the same major version as the client, as described in &http-version;,
2076   other than with this error message. The response &SHOULD; contain
2077   a representation describing why that version is not supported and what other
2078   protocols are supported by that server.
2079</t>
2080
2081</section>
2082</section>
2083</section>
2084
2085
2086<section title="Header Field Definitions" anchor="header.fields">
2087<t>
2088   This section defines the syntax and semantics of HTTP/1.1 header fields
2089   related to request and response semantics.
2090</t>
2091
2092<section title="Allow" anchor="header.allow">
2093  <iref primary="true" item="Allow header field" x:for-anchor=""/>
2094  <iref primary="true" item="Header Fields" subitem="Allow" x:for-anchor=""/>
2095  <x:anchor-alias value="Allow"/>
2096  <x:anchor-alias value="Allow-v"/>
2097<t>
2098   The "Allow" response-header field lists the set of methods advertised as
2099   supported by the target resource. The purpose of this field is strictly to
2100   inform the recipient of valid methods associated with the resource.
2101</t>
2102<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
2103  <x:ref>Allow</x:ref>   = "Allow" ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
2104  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
2105</artwork></figure>
2106<t>
2107   Example of use:
2108</t>
2109<figure><artwork type="example">
2110  Allow: GET, HEAD, PUT
2111</artwork></figure>
2112<t>
2113   The actual set of allowed methods is defined by the origin server at the
2114   time of each request.
2115</t>
2116<t>
2117   A proxy &MUST-NOT; modify the Allow header field &mdash; it does not need to
2118   understand all the methods specified in order to handle them according to
2119   the generic message handling rules.
2120</t>
2121</section>
2122
2123<section title="Expect" anchor="header.expect">
2124  <iref primary="true" item="Expect header field" x:for-anchor=""/>
2125  <iref primary="true" item="Header Fields" subitem="Expect" x:for-anchor=""/>
2126  <x:anchor-alias value="Expect"/>
2127  <x:anchor-alias value="Expect-v"/>
2128  <x:anchor-alias value="expectation"/>
2129  <x:anchor-alias value="expectation-extension"/>
2130  <x:anchor-alias value="expect-params"/>
2131<t>
2132   The "Expect" request-header field is used to indicate that particular
2133   server behaviors are required by the client.
2134</t>
2135<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"/>
2136  <x:ref>Expect</x:ref>       = "Expect" ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
2137  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
2138 
2139  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
2140  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
2141                           *<x:ref>expect-params</x:ref> ]
2142  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
2143</artwork></figure>
2144<t>
2145   A server that does not understand or is unable to comply with any of
2146   the expectation values in the Expect field of a request &MUST; respond
2147   with appropriate error status code. The server &MUST; respond with a 417
2148   (Expectation Failed) status code if any of the expectations cannot be met
2149   or, if there are other problems with the request, some other 4xx
2150   status code.
2151</t>
2152<t>
2153   This header field is defined with extensible syntax to allow for
2154   future extensions. If a server receives a request containing an
2155   Expect field that includes an expectation-extension that it does not
2156   support, it &MUST; respond with a 417 (Expectation Failed) status code.
2157</t>
2158<t>
2159   Comparison of expectation values is case-insensitive for unquoted
2160   tokens (including the 100-continue token), and is case-sensitive for
2161   quoted-string expectation-extensions.
2162</t>
2163<t>
2164   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
2165   return a 417 (Expectation Failed) status code if it receives a request
2166   with an expectation that it cannot meet. However, the Expect
2167   request-header field itself is end-to-end; it &MUST; be forwarded if the
2168   request is forwarded.
2169</t>
2170<t>
2171   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
2172   Expect header field.
2173</t>
2174<t>
2175   See &use100; for the use of the 100 (Continue) status code.
2176</t>
2177</section>
2178
2179<section title="From" anchor="header.from">
2180  <iref primary="true" item="From header field" x:for-anchor=""/>
2181  <iref primary="true" item="Header Fields" subitem="From" x:for-anchor=""/>
2182  <x:anchor-alias value="From"/>
2183  <x:anchor-alias value="From-v"/>
2184  <x:anchor-alias value="mailbox"/>
2185<t>
2186   The "From" request-header field, if given, &SHOULD; contain an Internet
2187   e-mail address for the human user who controls the requesting user
2188   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
2189   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
2190</t>
2191<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
2192  <x:ref>From</x:ref>    = "From" ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
2193  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
2194 
2195  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2196</artwork></figure>
2197<t>
2198   An example is:
2199</t>
2200<figure><artwork type="example">
2201  From: webmaster@example.org
2202</artwork></figure>
2203<t>
2204   This header field &MAY; be used for logging purposes and as a means for
2205   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2206   be used as an insecure form of access protection. The interpretation
2207   of this field is that the request is being performed on behalf of the
2208   person given, who accepts responsibility for the method performed. In
2209   particular, robot agents &SHOULD; include this header field so that the
2210   person responsible for running the robot can be contacted if problems
2211   occur on the receiving end.
2212</t>
2213<t>
2214   The Internet e-mail address in this field &MAY; be separate from the
2215   Internet host which issued the request. For example, when a request
2216   is passed through a proxy the original issuer's address &SHOULD; be
2217   used.
2218</t>
2219<t>
2220   The client &SHOULD-NOT;  send the From header field without the user's
2221   approval, as it might conflict with the user's privacy interests or
2222   their site's security policy. It is strongly recommended that the
2223   user be able to disable, enable, and modify the value of this field
2224   at any time prior to a request.
2225</t>
2226</section>
2227
2228<section title="Location" anchor="header.location">
2229  <iref primary="true" item="Location header field" x:for-anchor=""/>
2230  <iref primary="true" item="Header Fields" subitem="Location" x:for-anchor=""/>
2231  <x:anchor-alias value="Location"/>
2232  <x:anchor-alias value="Location-v"/>
2233<t>
2234   The "Location" response-header field is used to identify a newly created
2235   resource, or to redirect the recipient to a different location for
2236   completion of the request.
2237</t>
2238<t>
2239   For 201 (Created) responses, the Location is the URI of the new resource
2240   which was created by the request. For 3xx responses, the location &SHOULD;
2241   indicate the server's preferred URI for automatic redirection to the
2242   resource.
2243</t>
2244<t>
2245   The field value consists of a single URI-reference. When it has the form
2246   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2247   the final value is computed by resolving it against the effective request
2248   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
2249</t>
2250<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
2251  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
2252  <x:ref>Location-v</x:ref>     = <x:ref>URI-reference</x:ref>
2253</artwork></figure>
2254<figure>
2255<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical WSP below, it's necessary this way for xml2rfc-->
2256<artwork type="example">
2257  Location: http://www.example.org/pub/WWW/People.html#tim
2258</artwork></figure><figure><artwork type="example">  Location: /index.html
2259</artwork></figure>
2260<t>
2261   There are circumstances in which a fragment identifier in a Location URI
2262   would not be appropriate:
2263   <list style="symbols">
2264      <t>With a 201 Created response, because in this usage the Location header
2265      field specifies the URI for the entire created resource.</t>
2266      <t>With 305 Use Proxy.</t>
2267   </list>
2268</t>
2269<x:note>
2270  <t>
2271    <x:h>Note:</x:h> This specification does not define precedence rules
2272    for the case where the original URI, as navigated to by the user
2273    agent, and the Location header field value both contain fragment
2274    identifiers. Thus be aware that including fragment identifiers might
2275    inconvenience anyone relying on the semantics of the original URI's
2276    fragment identifier.
2277  </t>
2278</x:note>
2279<x:note>
2280  <t>
2281    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2282    from Location in that the Content-Location identifies the most specific
2283    resource corresponding to the enclosed representation.
2284    It is therefore possible for a response to contain header fields for
2285    both Location and Content-Location.
2286  </t>
2287</x:note>
2288</section>
2289
2290<section title="Max-Forwards" anchor="header.max-forwards">
2291  <iref primary="true" item="Max-Forwards header field" x:for-anchor=""/>
2292  <iref primary="true" item="Header Fields" subitem="Max-Forwards" x:for-anchor=""/>
2293  <x:anchor-alias value="Max-Forwards"/>
2294  <x:anchor-alias value="Max-Forwards-v"/>
2295<t>
2296   The "Max-Forwards" request-header field provides a mechanism with the
2297   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2298   methods to limit the number of times that the request is forwarded by
2299   proxies or gateways. This can be useful when the client is attempting to
2300   trace a request which appears to be failing or looping in mid-chain.
2301</t>
2302<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
2303  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
2304  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
2305</artwork></figure>
2306<t>
2307   The Max-Forwards value is a decimal integer indicating the remaining
2308   number of times this request message can be forwarded.
2309</t>
2310<t>
2311   Each proxy or gateway recipient of a TRACE or OPTIONS request
2312   containing a Max-Forwards header field &MUST; check and update its
2313   value prior to forwarding the request. If the received value is zero
2314   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2315   respond as the final recipient. If the received Max-Forwards value is
2316   greater than zero, then the forwarded message &MUST; contain an updated
2317   Max-Forwards field with a value decremented by one (1).
2318</t>
2319<t>
2320   The Max-Forwards header field &MAY; be ignored for all other methods.
2321</t>
2322</section>
2323
2324<section title="Referer" anchor="header.referer">
2325  <iref primary="true" item="Referer header field" x:for-anchor=""/>
2326  <iref primary="true" item="Header Fields" subitem="Referer" x:for-anchor=""/>
2327  <x:anchor-alias value="Referer"/>
2328  <x:anchor-alias value="Referer-v"/>
2329<t>
2330   The "Referer" [sic] request-header field allows the client to specify the
2331   URI of the resource from which the effective request URI was obtained (the
2332   "referrer", although the header field is misspelled.).
2333</t>
2334<t>
2335   The Referer header field allows servers to generate lists of back-links to
2336   resources for interest, logging, optimized caching, etc. It also allows
2337   obsolete or mistyped links to be traced for maintenance. Some servers use
2338   Referer as a means of controlling where they allow links from (so-called
2339   "deep linking"), but legitimate requests do not always
2340   contain a Referer header field.
2341</t>
2342<t>
2343   If the effective request URI was obtained from a source that does not have its own
2344   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
2345   sent with the value "about:blank", or not be sent at all. Note that this
2346   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2347</t>
2348<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
2349  <x:ref>Referer</x:ref>        = "Referer" ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
2350  <x:ref>Referer-v</x:ref>      = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2351</artwork></figure>
2352<t>
2353   Example:
2354</t>
2355<figure><artwork type="example">
2356  Referer: http://www.example.org/hypertext/Overview.html
2357</artwork></figure>
2358<t>
2359   If the field value is a relative URI, it &SHOULD; be interpreted
2360   relative to the effective request URI. The URI &MUST-NOT; include a fragment. See
2361   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2362</t>
2363</section>
2364
2365<section title="Retry-After" anchor="header.retry-after">
2366  <iref primary="true" item="Retry-After header field" x:for-anchor=""/>
2367  <iref primary="true" item="Header Fields" subitem="Retry-After" x:for-anchor=""/>
2368  <x:anchor-alias value="Retry-After"/>
2369  <x:anchor-alias value="Retry-After-v"/>
2370<t>
2371   The response-header "Retry-After" field can be used with a 503 (Service
2372   Unavailable) response to indicate how long the service is expected to
2373   be unavailable to the requesting client. This field &MAY; also be used
2374   with any 3xx (Redirection) response to indicate the minimum time the
2375   user-agent is asked wait before issuing the redirected request.
2376</t>
2377<t>
2378   The value of this field can be either an HTTP-date or an integer number
2379   of seconds (in decimal) after the time of the response.
2380</t>
2381<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
2382  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
2383  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2384</artwork></figure>
2385<t anchor="rule.delta-seconds">
2386  <x:anchor-alias value="delta-seconds"/>
2387   Time spans are non-negative decimal integers, representing time in
2388   seconds.
2389</t>
2390<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2391  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2392</artwork></figure>
2393<t>
2394   Two examples of its use are
2395</t>
2396<figure><artwork type="example">
2397  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2398  Retry-After: 120
2399</artwork></figure>
2400<t>
2401   In the latter example, the delay is 2 minutes.
2402</t>
2403</section>
2404
2405<section title="Server" anchor="header.server">
2406  <iref primary="true" item="Server header field" x:for-anchor=""/>
2407  <iref primary="true" item="Header Fields" subitem="Server" x:for-anchor=""/>
2408  <x:anchor-alias value="Server"/>
2409  <x:anchor-alias value="Server-v"/>
2410<t>
2411   The "Server" response-header field contains information about the
2412   software used by the origin server to handle the request.
2413</t>
2414<t>
2415   The field can contain multiple product tokens (&product-tokens;) and
2416   comments (&header-fields;) identifying the server and any significant
2417   subproducts. The product tokens are listed in order of their significance
2418   for identifying the application.
2419</t>
2420<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
2421  <x:ref>Server</x:ref>         = "Server" ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
2422  <x:ref>Server-v</x:ref>       = <x:ref>product</x:ref>
2423                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2424</artwork></figure>
2425<t>
2426   Example:
2427</t>
2428<figure><artwork type="example">
2429  Server: CERN/3.0 libwww/2.17
2430</artwork></figure>
2431<t>
2432   If the response is being forwarded through a proxy, the proxy
2433   application &MUST-NOT; modify the Server response-header field. Instead, it
2434   &MUST; include a Via field (as described in &header-via;).
2435</t>
2436<x:note>
2437  <t>
2438    <x:h>Note:</x:h> Revealing the specific software version of the server might
2439    allow the server machine to become more vulnerable to attacks
2440    against software that is known to contain security holes. Server
2441    implementors are encouraged to make this field a configurable
2442    option.
2443  </t>
2444</x:note>
2445</section>
2446
2447<section title="User-Agent" anchor="header.user-agent">
2448  <iref primary="true" item="User-Agent header field" x:for-anchor=""/>
2449  <iref primary="true" item="Header Fields" subitem="User-Agent" x:for-anchor=""/>
2450  <x:anchor-alias value="User-Agent"/>
2451  <x:anchor-alias value="User-Agent-v"/>
2452<t>
2453   The "User-Agent" request-header field contains information about the user
2454   agent originating the request. User agents &SHOULD; include this field with
2455   requests.
2456</t>
2457<t>
2458   Typically, it is used for statistical purposes, the tracing of protocol
2459   violations, and tailoring responses to avoid particular user agent
2460   limitations.
2461</t>
2462<t>
2463   The field can contain multiple product tokens (&product-tokens;)
2464   and comments (&header-fields;) identifying the agent and its
2465   significant subproducts. By convention, the product tokens are listed in
2466   order of their significance for identifying the application.
2467</t>
2468<t>
2469   Because this field is usually sent on every request a user agent makes,
2470   implementations are encouraged not to include needlessly fine-grained
2471   detail, and to limit (or even prohibit) the addition of subproducts by third
2472   parties. Overly long and detailed User-Agent field values make requests
2473   larger and can also be used to identify ("fingerprint") the user against
2474   their wishes.
2475</t>
2476<t>
2477   Likewise, implementations are encouraged not to use the product tokens of
2478   other implementations in order to declare compatibility with them, as this
2479   circumvents the purpose of the field. Finally, they are encouraged not to
2480   use comments to identify products; doing so makes the field value more
2481   difficult to parse.
2482</t>
2483<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
2484  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
2485  <x:ref>User-Agent-v</x:ref>   = <x:ref>product</x:ref>
2486                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2487</artwork></figure>
2488<t>
2489   Example:
2490</t>
2491<figure><artwork type="example">
2492  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2493</artwork></figure>
2494</section>
2495
2496</section>
2497
2498<section title="IANA Considerations" anchor="IANA.considerations">
2499
2500<section title="Method Registry" anchor="method.registration">
2501<t>
2502  The registration procedure for HTTP Methods is defined by
2503  <xref target="method.registry"/> of this document.
2504</t>
2505<t>
2506   The HTTP Method Registry shall be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2507   and be populated with the registrations below:
2508</t>
2509<?BEGININC p2-semantics.iana-methods ?>
2510<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2511<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2512   <ttcol>Method</ttcol>
2513   <ttcol>Safe</ttcol>
2514   <ttcol>Reference</ttcol>
2515   <c>CONNECT</c>
2516   <c>no</c>
2517   <c>
2518      <xref target="CONNECT"/>
2519   </c>
2520   <c>DELETE</c>
2521   <c>no</c>
2522   <c>
2523      <xref target="DELETE"/>
2524   </c>
2525   <c>GET</c>
2526   <c>yes</c>
2527   <c>
2528      <xref target="GET"/>
2529   </c>
2530   <c>HEAD</c>
2531   <c>yes</c>
2532   <c>
2533      <xref target="HEAD"/>
2534   </c>
2535   <c>OPTIONS</c>
2536   <c>yes</c>
2537   <c>
2538      <xref target="OPTIONS"/>
2539   </c>
2540   <c>POST</c>
2541   <c>no</c>
2542   <c>
2543      <xref target="POST"/>
2544   </c>
2545   <c>PUT</c>
2546   <c>no</c>
2547   <c>
2548      <xref target="PUT"/>
2549   </c>
2550   <c>TRACE</c>
2551   <c>yes</c>
2552   <c>
2553      <xref target="TRACE"/>
2554   </c>
2555</texttable>
2556<!--(END)-->
2557<?ENDINC p2-semantics.iana-methods ?>
2558</section>
2559
2560<section title="Status Code Registry" anchor="status.code.registration">
2561<t>
2562   The registration procedure for HTTP Status Codes &mdash; previously defined
2563   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> &mdash; is now defined
2564   by <xref target="status.code.registry"/> of this document.
2565</t>
2566<t>
2567   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2568   shall be updated with the registrations below:
2569</t>
2570<?BEGININC p2-semantics.iana-status-codes ?>
2571<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2572<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2573   <ttcol>Value</ttcol>
2574   <ttcol>Description</ttcol>
2575   <ttcol>Reference</ttcol>
2576   <c>100</c>
2577   <c>Continue</c>
2578   <c>
2579      <xref target="status.100"/>
2580   </c>
2581   <c>101</c>
2582   <c>Switching Protocols</c>
2583   <c>
2584      <xref target="status.101"/>
2585   </c>
2586   <c>200</c>
2587   <c>OK</c>
2588   <c>
2589      <xref target="status.200"/>
2590   </c>
2591   <c>201</c>
2592   <c>Created</c>
2593   <c>
2594      <xref target="status.201"/>
2595   </c>
2596   <c>202</c>
2597   <c>Accepted</c>
2598   <c>
2599      <xref target="status.202"/>
2600   </c>
2601   <c>203</c>
2602   <c>Non-Authoritative Information</c>
2603   <c>
2604      <xref target="status.203"/>
2605   </c>
2606   <c>204</c>
2607   <c>No Content</c>
2608   <c>
2609      <xref target="status.204"/>
2610   </c>
2611   <c>205</c>
2612   <c>Reset Content</c>
2613   <c>
2614      <xref target="status.205"/>
2615   </c>
2616   <c>300</c>
2617   <c>Multiple Choices</c>
2618   <c>
2619      <xref target="status.300"/>
2620   </c>
2621   <c>301</c>
2622   <c>Moved Permanently</c>
2623   <c>
2624      <xref target="status.301"/>
2625   </c>
2626   <c>302</c>
2627   <c>Found</c>
2628   <c>
2629      <xref target="status.302"/>
2630   </c>
2631   <c>303</c>
2632   <c>See Other</c>
2633   <c>
2634      <xref target="status.303"/>
2635   </c>
2636   <c>305</c>
2637   <c>Use Proxy</c>
2638   <c>
2639      <xref target="status.305"/>
2640   </c>
2641   <c>306</c>
2642   <c>(Unused)</c>
2643   <c>
2644      <xref target="status.306"/>
2645   </c>
2646   <c>307</c>
2647   <c>Temporary Redirect</c>
2648   <c>
2649      <xref target="status.307"/>
2650   </c>
2651   <c>400</c>
2652   <c>Bad Request</c>
2653   <c>
2654      <xref target="status.400"/>
2655   </c>
2656   <c>402</c>
2657   <c>Payment Required</c>
2658   <c>
2659      <xref target="status.402"/>
2660   </c>
2661   <c>403</c>
2662   <c>Forbidden</c>
2663   <c>
2664      <xref target="status.403"/>
2665   </c>
2666   <c>404</c>
2667   <c>Not Found</c>
2668   <c>
2669      <xref target="status.404"/>
2670   </c>
2671   <c>405</c>
2672   <c>Method Not Allowed</c>
2673   <c>
2674      <xref target="status.405"/>
2675   </c>
2676   <c>406</c>
2677   <c>Not Acceptable</c>
2678   <c>
2679      <xref target="status.406"/>
2680   </c>
2681   <c>407</c>
2682   <c>Proxy Authentication Required</c>
2683   <c>
2684      <xref target="status.407"/>
2685   </c>
2686   <c>408</c>
2687   <c>Request Timeout</c>
2688   <c>
2689      <xref target="status.408"/>
2690   </c>
2691   <c>409</c>
2692   <c>Conflict</c>
2693   <c>
2694      <xref target="status.409"/>
2695   </c>
2696   <c>410</c>
2697   <c>Gone</c>
2698   <c>
2699      <xref target="status.410"/>
2700   </c>
2701   <c>411</c>
2702   <c>Length Required</c>
2703   <c>
2704      <xref target="status.411"/>
2705   </c>
2706   <c>413</c>
2707   <c>Request Entity Too Large</c>
2708   <c>
2709      <xref target="status.413"/>
2710   </c>
2711   <c>414</c>
2712   <c>URI Too Long</c>
2713   <c>
2714      <xref target="status.414"/>
2715   </c>
2716   <c>415</c>
2717   <c>Unsupported Media Type</c>
2718   <c>
2719      <xref target="status.415"/>
2720   </c>
2721   <c>417</c>
2722   <c>Expectation Failed</c>
2723   <c>
2724      <xref target="status.417"/>
2725   </c>
2726   <c>426</c>
2727   <c>Upgrade Required</c>
2728   <c>
2729      <xref target="status.426"/>
2730   </c>
2731   <c>500</c>
2732   <c>Internal Server Error</c>
2733   <c>
2734      <xref target="status.500"/>
2735   </c>
2736   <c>501</c>
2737   <c>Not Implemented</c>
2738   <c>
2739      <xref target="status.501"/>
2740   </c>
2741   <c>502</c>
2742   <c>Bad Gateway</c>
2743   <c>
2744      <xref target="status.502"/>
2745   </c>
2746   <c>503</c>
2747   <c>Service Unavailable</c>
2748   <c>
2749      <xref target="status.503"/>
2750   </c>
2751   <c>504</c>
2752   <c>Gateway Timeout</c>
2753   <c>
2754      <xref target="status.504"/>
2755   </c>
2756   <c>505</c>
2757   <c>HTTP Version Not Supported</c>
2758   <c>
2759      <xref target="status.505"/>
2760   </c>
2761</texttable>
2762<!--(END)-->
2763<?ENDINC p2-semantics.iana-status-codes ?>
2764</section>
2765<section title="Header Field Registration" anchor="header.field.registration">
2766<t>
2767   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
2768   with the permanent registrations below (see <xref target="RFC3864"/>):
2769</t>
2770<?BEGININC p2-semantics.iana-headers ?>
2771<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2772<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2773   <ttcol>Header Field Name</ttcol>
2774   <ttcol>Protocol</ttcol>
2775   <ttcol>Status</ttcol>
2776   <ttcol>Reference</ttcol>
2777
2778   <c>Allow</c>
2779   <c>http</c>
2780   <c>standard</c>
2781   <c>
2782      <xref target="header.allow"/>
2783   </c>
2784   <c>Expect</c>
2785   <c>http</c>
2786   <c>standard</c>
2787   <c>
2788      <xref target="header.expect"/>
2789   </c>
2790   <c>From</c>
2791   <c>http</c>
2792   <c>standard</c>
2793   <c>
2794      <xref target="header.from"/>
2795   </c>
2796   <c>Location</c>
2797   <c>http</c>
2798   <c>standard</c>
2799   <c>
2800      <xref target="header.location"/>
2801   </c>
2802   <c>Max-Forwards</c>
2803   <c>http</c>
2804   <c>standard</c>
2805   <c>
2806      <xref target="header.max-forwards"/>
2807   </c>
2808   <c>Referer</c>
2809   <c>http</c>
2810   <c>standard</c>
2811   <c>
2812      <xref target="header.referer"/>
2813   </c>
2814   <c>Retry-After</c>
2815   <c>http</c>
2816   <c>standard</c>
2817   <c>
2818      <xref target="header.retry-after"/>
2819   </c>
2820   <c>Server</c>
2821   <c>http</c>
2822   <c>standard</c>
2823   <c>
2824      <xref target="header.server"/>
2825   </c>
2826   <c>User-Agent</c>
2827   <c>http</c>
2828   <c>standard</c>
2829   <c>
2830      <xref target="header.user-agent"/>
2831   </c>
2832</texttable>
2833<!--(END)-->
2834<?ENDINC p2-semantics.iana-headers ?>
2835<t>
2836   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2837</t>
2838</section>
2839</section>
2840
2841<section title="Security Considerations" anchor="security.considerations">
2842<t>
2843   This section is meant to inform application developers, information
2844   providers, and users of the security limitations in HTTP/1.1 as
2845   described by this document. The discussion does not include
2846   definitive solutions to the problems revealed, though it does make
2847   some suggestions for reducing security risks.
2848</t>
2849
2850<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2851<t>
2852   Like any generic data transfer protocol, HTTP cannot regulate the
2853   content of the data that is transferred, nor is there any a priori
2854   method of determining the sensitivity of any particular piece of
2855   information within the context of any given request. Therefore,
2856   applications &SHOULD; supply as much control over this information as
2857   possible to the provider of that information. Four header fields are
2858   worth special mention in this context: Server, Via, Referer and From.
2859</t>
2860<t>
2861   Revealing the specific software version of the server might allow the
2862   server machine to become more vulnerable to attacks against software
2863   that is known to contain security holes. Implementors &SHOULD; make the
2864   Server header field a configurable option.
2865</t>
2866<t>
2867   Proxies which serve as a portal through a network firewall &SHOULD;
2868   take special precautions regarding the transfer of header information
2869   that identifies the hosts behind the firewall. In particular, they
2870   &SHOULD; remove, or replace with sanitized versions, any Via fields
2871   generated behind the firewall.
2872</t>
2873<t>
2874   The Referer header field allows reading patterns to be studied and reverse
2875   links drawn. Although it can be very useful, its power can be abused
2876   if user details are not separated from the information contained in
2877   the Referer. Even when the personal information has been removed, the
2878   Referer header field might indicate a private document's URI whose
2879   publication would be inappropriate.
2880</t>
2881<t>
2882   The information sent in the From field might conflict with the user's
2883   privacy interests or their site's security policy, and hence it
2884   &SHOULD-NOT;  be transmitted without the user being able to disable,
2885   enable, and modify the contents of the field. The user &MUST; be able
2886   to set the contents of this field within a user preference or
2887   application defaults configuration.
2888</t>
2889<t>
2890   We suggest, though do not require, that a convenient toggle interface
2891   be provided for the user to enable or disable the sending of From and
2892   Referer information.
2893</t>
2894<t>
2895   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref
2896   target="header.server"/>) header fields can sometimes be used to determine
2897   that a specific client or server have a particular security hole which might
2898   be exploited. Unfortunately, this same information is often used for other
2899   valuable purposes for which HTTP currently has no better mechanism.
2900</t>
2901<t>
2902   Furthermore, the User-Agent header field may contain enough entropy to be
2903   used, possibly in conjunction with other material, to uniquely identify the
2904   user.
2905</t>
2906<t>
2907   Some methods, like TRACE (<xref target="TRACE"/>), expose information
2908   that was sent in request header fields within the body of their response.
2909   Clients &SHOULD; be careful with sensitive information, like Cookies,
2910   Authorization credentials and other header fields that might be used to
2911   collect data from the client.
2912</t> 
2913</section>
2914
2915<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2916<t>
2917   Because the source of a link might be private information or might
2918   reveal an otherwise private information source, it is strongly
2919   recommended that the user be able to select whether or not the
2920   Referer field is sent. For example, a browser client could have a
2921   toggle switch for browsing openly/anonymously, which would
2922   respectively enable/disable the sending of Referer and From
2923   information.
2924</t>
2925<t>
2926   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2927   HTTP request if the referring page was transferred with a secure
2928   protocol.
2929</t>
2930<t>
2931   Authors of services &SHOULD-NOT; use GET-based forms for the submission of
2932   sensitive data because that data will be placed in the request-target. Many
2933   existing servers, proxies, and user agents log or display the request-target
2934   in places where it might be visible to third parties. Such services can
2935   use POST-based form submission instead.
2936</t>
2937</section>
2938
2939<section title="Location Headers and Spoofing" anchor="location.spoofing">
2940<t>
2941   If a single server supports multiple organizations that do not trust
2942   one another, then it &MUST; check the values of Location and Content-Location
2943   header fields in responses that are generated under control of
2944   said organizations to make sure that they do not attempt to
2945   invalidate resources over which they have no authority.
2946</t>
2947</section>
2948
2949<section title="Security Considerations for CONNECT">
2950<t>
2951   Since tunneled data is opaque to the proxy, there are additional
2952   risks to tunneling to other well-known or reserved ports.
2953   A HTTP client CONNECTing to port 25 could relay spam
2954   via SMTP, for example. As such, proxies &SHOULD; restrict CONNECT
2955   access to a small number of known ports.
2956</t>
2957</section>
2958
2959</section>
2960
2961<section title="Acknowledgments" anchor="ack">
2962</section>
2963</middle>
2964<back>
2965
2966<references title="Normative References">
2967
2968<reference anchor="Part1">
2969  <front>
2970    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2971    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2972      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
2973      <address><email>fielding@gbiv.com</email></address>
2974    </author>
2975    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2976      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2977      <address><email>jg@freedesktop.org</email></address>
2978    </author>
2979    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2980      <organization abbrev="HP">Hewlett-Packard Company</organization>
2981      <address><email>JeffMogul@acm.org</email></address>
2982    </author>
2983    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2984      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2985      <address><email>henrikn@microsoft.com</email></address>
2986    </author>
2987    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2988      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
2989      <address><email>LMM@acm.org</email></address>
2990    </author>
2991    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2992      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2993      <address><email>paulle@microsoft.com</email></address>
2994    </author>
2995    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2996      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2997      <address><email>timbl@w3.org</email></address>
2998    </author>
2999    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3000      <organization abbrev="W3C">World Wide Web Consortium</organization>
3001      <address><email>ylafon@w3.org</email></address>
3002    </author>
3003    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3004      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3005      <address><email>julian.reschke@greenbytes.de</email></address>
3006    </author>
3007    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3008  </front>
3009  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
3010  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
3011</reference>
3012
3013<reference anchor="Part3">
3014  <front>
3015    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
3016    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3017      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3018      <address><email>fielding@gbiv.com</email></address>
3019    </author>
3020    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3021      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3022      <address><email>jg@freedesktop.org</email></address>
3023    </author>
3024    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3025      <organization abbrev="HP">Hewlett-Packard Company</organization>
3026      <address><email>JeffMogul@acm.org</email></address>
3027    </author>
3028    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3029      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3030      <address><email>henrikn@microsoft.com</email></address>
3031    </author>
3032    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3033      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3034      <address><email>LMM@acm.org</email></address>
3035    </author>
3036    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3037      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3038      <address><email>paulle@microsoft.com</email></address>
3039    </author>
3040    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3041      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3042      <address><email>timbl@w3.org</email></address>
3043    </author>
3044    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3045      <organization abbrev="W3C">World Wide Web Consortium</organization>
3046      <address><email>ylafon@w3.org</email></address>
3047    </author>
3048    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3049      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3050      <address><email>julian.reschke@greenbytes.de</email></address>
3051    </author>
3052    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3053  </front>
3054  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
3055  <x:source href="p3-payload.xml" basename="p3-payload"/>
3056</reference>
3057
3058<reference anchor="Part4">
3059  <front>
3060    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
3061    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3062      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3063      <address><email>fielding@gbiv.com</email></address>
3064    </author>
3065    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3066      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3067      <address><email>jg@freedesktop.org</email></address>
3068    </author>
3069    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3070      <organization abbrev="HP">Hewlett-Packard Company</organization>
3071      <address><email>JeffMogul@acm.org</email></address>
3072    </author>
3073    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3074      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3075      <address><email>henrikn@microsoft.com</email></address>
3076    </author>
3077    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3078      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3079      <address><email>LMM@acm.org</email></address>
3080    </author>
3081    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3082      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3083      <address><email>paulle@microsoft.com</email></address>
3084    </author>
3085    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3086      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3087      <address><email>timbl@w3.org</email></address>
3088    </author>
3089    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3090      <organization abbrev="W3C">World Wide Web Consortium</organization>
3091      <address><email>ylafon@w3.org</email></address>
3092    </author>
3093    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3094      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3095      <address><email>julian.reschke@greenbytes.de</email></address>
3096    </author>
3097    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3098  </front>
3099  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
3100  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
3101</reference>
3102
3103<reference anchor="Part5">
3104  <front>
3105    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
3106    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3107      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3108      <address><email>fielding@gbiv.com</email></address>
3109    </author>
3110    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3111      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3112      <address><email>jg@freedesktop.org</email></address>
3113    </author>
3114    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3115      <organization abbrev="HP">Hewlett-Packard Company</organization>
3116      <address><email>JeffMogul@acm.org</email></address>
3117    </author>
3118    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3119      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3120      <address><email>henrikn@microsoft.com</email></address>
3121    </author>
3122    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3123      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3124      <address><email>LMM@acm.org</email></address>
3125    </author>
3126    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3127      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3128      <address><email>paulle@microsoft.com</email></address>
3129    </author>
3130    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3131      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3132      <address><email>timbl@w3.org</email></address>
3133    </author>
3134    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3135      <organization abbrev="W3C">World Wide Web Consortium</organization>
3136      <address><email>ylafon@w3.org</email></address>
3137    </author>
3138    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3139      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3140      <address><email>julian.reschke@greenbytes.de</email></address>
3141    </author>
3142    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3143  </front>
3144  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
3145  <x:source href="p5-range.xml" basename="p5-range"/>
3146</reference>
3147
3148<reference anchor="Part6">
3149  <front>
3150    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
3151    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3152      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3153      <address><email>fielding@gbiv.com</email></address>
3154    </author>
3155    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3156      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3157      <address><email>jg@freedesktop.org</email></address>
3158    </author>
3159    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3160      <organization abbrev="HP">Hewlett-Packard Company</organization>
3161      <address><email>JeffMogul@acm.org</email></address>
3162    </author>
3163    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3164      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3165      <address><email>henrikn@microsoft.com</email></address>
3166    </author>
3167    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3168      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3169      <address><email>LMM@acm.org</email></address>
3170    </author>
3171    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3172      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3173      <address><email>paulle@microsoft.com</email></address>
3174    </author>
3175    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3176      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3177      <address><email>timbl@w3.org</email></address>
3178    </author>
3179    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3180      <organization abbrev="W3C">World Wide Web Consortium</organization>
3181      <address><email>ylafon@w3.org</email></address>
3182    </author>
3183    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
3184      <address><email>mnot@mnot.net</email></address>
3185    </author>
3186    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3187      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3188      <address><email>julian.reschke@greenbytes.de</email></address>
3189    </author>
3190    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3191  </front>
3192  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
3193  <x:source href="p6-cache.xml" basename="p6-cache"/>
3194</reference>
3195
3196<reference anchor="Part7">
3197  <front>
3198    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
3199    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3200      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3201      <address><email>fielding@gbiv.com</email></address>
3202    </author>
3203    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3204      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3205      <address><email>jg@freedesktop.org</email></address>
3206    </author>
3207    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3208      <organization abbrev="HP">Hewlett-Packard Company</organization>
3209      <address><email>JeffMogul@acm.org</email></address>
3210    </author>
3211    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3212      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3213      <address><email>henrikn@microsoft.com</email></address>
3214    </author>
3215    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3216      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3217      <address><email>LMM@acm.org</email></address>
3218    </author>
3219    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3220      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3221      <address><email>paulle@microsoft.com</email></address>
3222    </author>
3223    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3224      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3225      <address><email>timbl@w3.org</email></address>
3226    </author>
3227    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3228      <organization abbrev="W3C">World Wide Web Consortium</organization>
3229      <address><email>ylafon@w3.org</email></address>
3230    </author>
3231    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3232      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3233      <address><email>julian.reschke@greenbytes.de</email></address>
3234    </author>
3235    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3236  </front>
3237  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3238  <x:source href="p7-auth.xml" basename="p7-auth"/>
3239</reference>
3240
3241<reference anchor="RFC2119">
3242  <front>
3243    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3244    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3245      <organization>Harvard University</organization>
3246      <address><email>sob@harvard.edu</email></address>
3247    </author>
3248    <date month="March" year="1997"/>
3249  </front>
3250  <seriesInfo name="BCP" value="14"/>
3251  <seriesInfo name="RFC" value="2119"/>
3252</reference>
3253
3254<reference anchor="RFC3986">
3255 <front>
3256  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3257  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3258    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3259    <address>
3260       <email>timbl@w3.org</email>
3261       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3262    </address>
3263  </author>
3264  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3265    <organization abbrev="Day Software">Day Software</organization>
3266    <address>
3267      <email>fielding@gbiv.com</email>
3268      <uri>http://roy.gbiv.com/</uri>
3269    </address>
3270  </author>
3271  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3272    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3273    <address>
3274      <email>LMM@acm.org</email>
3275      <uri>http://larry.masinter.net/</uri>
3276    </address>
3277  </author>
3278  <date month='January' year='2005'></date>
3279 </front>
3280 <seriesInfo name="STD" value="66"/>
3281 <seriesInfo name="RFC" value="3986"/>
3282</reference>
3283
3284<reference anchor="RFC5234">
3285  <front>
3286    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3287    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3288      <organization>Brandenburg InternetWorking</organization>
3289      <address>
3290        <email>dcrocker@bbiw.net</email>
3291      </address> 
3292    </author>
3293    <author initials="P." surname="Overell" fullname="Paul Overell">
3294      <organization>THUS plc.</organization>
3295      <address>
3296        <email>paul.overell@thus.net</email>
3297      </address>
3298    </author>
3299    <date month="January" year="2008"/>
3300  </front>
3301  <seriesInfo name="STD" value="68"/>
3302  <seriesInfo name="RFC" value="5234"/>
3303</reference>
3304
3305</references>
3306
3307<references title="Informative References">
3308
3309<reference anchor="RFC1945">
3310  <front>
3311    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3312    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3313      <organization>MIT, Laboratory for Computer Science</organization>
3314      <address><email>timbl@w3.org</email></address>
3315    </author>
3316    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3317      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3318      <address><email>fielding@ics.uci.edu</email></address>
3319    </author>
3320    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3321      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3322      <address><email>frystyk@w3.org</email></address>
3323    </author>
3324    <date month="May" year="1996"/>
3325  </front>
3326  <seriesInfo name="RFC" value="1945"/>
3327</reference>
3328
3329<reference anchor="RFC2068">
3330  <front>
3331    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3332    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3333      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3334      <address><email>fielding@ics.uci.edu</email></address>
3335    </author>
3336    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3337      <organization>MIT Laboratory for Computer Science</organization>
3338      <address><email>jg@w3.org</email></address>
3339    </author>
3340    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3341      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3342      <address><email>mogul@wrl.dec.com</email></address>
3343    </author>
3344    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3345      <organization>MIT Laboratory for Computer Science</organization>
3346      <address><email>frystyk@w3.org</email></address>
3347    </author>
3348    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3349      <organization>MIT Laboratory for Computer Science</organization>
3350      <address><email>timbl@w3.org</email></address>
3351    </author>
3352    <date month="January" year="1997"/>
3353  </front>
3354  <seriesInfo name="RFC" value="2068"/>
3355</reference>
3356
3357<reference anchor="RFC2616">
3358  <front>
3359    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3360    <author initials="R." surname="Fielding" fullname="R. Fielding">
3361      <organization>University of California, Irvine</organization>
3362      <address><email>fielding@ics.uci.edu</email></address>
3363    </author>
3364    <author initials="J." surname="Gettys" fullname="J. Gettys">
3365      <organization>W3C</organization>
3366      <address><email>jg@w3.org</email></address>
3367    </author>
3368    <author initials="J." surname="Mogul" fullname="J. Mogul">
3369      <organization>Compaq Computer Corporation</organization>
3370      <address><email>mogul@wrl.dec.com</email></address>
3371    </author>
3372    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3373      <organization>MIT Laboratory for Computer Science</organization>
3374      <address><email>frystyk@w3.org</email></address>
3375    </author>
3376    <author initials="L." surname="Masinter" fullname="L. Masinter">
3377      <organization>Xerox Corporation</organization>
3378      <address><email>masinter@parc.xerox.com</email></address>
3379    </author>
3380    <author initials="P." surname="Leach" fullname="P. Leach">
3381      <organization>Microsoft Corporation</organization>
3382      <address><email>paulle@microsoft.com</email></address>
3383    </author>
3384    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3385      <organization>W3C</organization>
3386      <address><email>timbl@w3.org</email></address>
3387    </author>
3388    <date month="June" year="1999"/>
3389  </front>
3390  <seriesInfo name="RFC" value="2616"/>
3391</reference>
3392
3393<reference anchor='RFC2817'>
3394  <front>
3395    <title>Upgrading to TLS Within HTTP/1.1</title>
3396    <author initials='R.' surname='Khare' fullname='R. Khare'>
3397      <organization>4K Associates / UC Irvine</organization>
3398      <address><email>rohit@4K-associates.com</email></address>
3399    </author>
3400    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3401      <organization>Agranat Systems, Inc.</organization>
3402      <address><email>lawrence@agranat.com</email></address>
3403    </author>
3404    <date year='2000' month='May' />
3405  </front>
3406  <seriesInfo name='RFC' value='2817' />
3407</reference>
3408
3409<reference anchor='RFC3864'>
3410  <front>
3411    <title>Registration Procedures for Message Header Fields</title>
3412    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3413      <organization>Nine by Nine</organization>
3414      <address><email>GK-IETF@ninebynine.org</email></address>
3415    </author>
3416    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3417      <organization>BEA Systems</organization>
3418      <address><email>mnot@pobox.com</email></address>
3419    </author>
3420    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3421      <organization>HP Labs</organization>
3422      <address><email>JeffMogul@acm.org</email></address>
3423    </author>
3424    <date year='2004' month='September' />
3425  </front>
3426  <seriesInfo name='BCP' value='90' />
3427  <seriesInfo name='RFC' value='3864' />
3428</reference>
3429
3430<reference anchor='RFC5226'>
3431  <front>
3432    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3433    <author initials='T.' surname='Narten' fullname='T. Narten'>
3434      <organization>IBM</organization>
3435      <address><email>narten@us.ibm.com</email></address>
3436    </author>
3437    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3438      <organization>Google</organization>
3439      <address><email>Harald@Alvestrand.no</email></address>
3440    </author>
3441    <date year='2008' month='May' />
3442  </front>
3443  <seriesInfo name='BCP' value='26' />
3444  <seriesInfo name='RFC' value='5226' />
3445</reference>
3446
3447<reference anchor="RFC5322">
3448  <front>
3449    <title>Internet Message Format</title>
3450    <author initials="P." surname="Resnick" fullname="P. Resnick">
3451      <organization>Qualcomm Incorporated</organization>
3452    </author>
3453    <date year="2008" month="October"/>
3454  </front> 
3455  <seriesInfo name="RFC" value="5322"/>
3456</reference>
3457
3458</references>
3459
3460<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3461<t>
3462  This document takes over the Status Code Registry, previously defined
3463  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3464  (<xref target="status.code.registry"/>)
3465</t>
3466<t>
3467  Clarify definition of POST.
3468  (<xref target="POST"/>)
3469</t>
3470<t>
3471  Take over definition of CONNECT method from <xref target="RFC2817"/>.
3472  (<xref target="CONNECT"/>)
3473</t>
3474<t>
3475  Failed to consider that there are
3476  many other request methods that are safe to automatically redirect,
3477  and further that the user agent is able to make that determination
3478  based on the request method semantics.
3479  (Sections <xref format="counter" target="status.301"/>,
3480  <xref format="counter" target="status.302"/> and
3481  <xref format="counter" target="status.307"/>)
3482</t>
3483<t>
3484  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3485  It used to indicate that the target resource must be accessed through the
3486  proxy given by the Location field. The Location field gave the URI of the
3487  proxy. The recipient was expected to repeat this single request via the proxy.
3488  (<xref target="status.305"/>)
3489</t>
3490<t>
3491  Define status 426 (Upgrade Required) (this was incorporated from
3492  <xref target="RFC2817"/>).
3493  (<xref target="status.426"/>)
3494</t>
3495<t>
3496  Reclassify "Allow" as response header field, removing the option to
3497  specify it in a PUT request.
3498  Relax the server requirement on the contents of the Allow header field and
3499  remove requirement on clients to always trust the header field value.
3500  (<xref target="header.allow"/>)
3501</t>
3502<t>
3503  Correct syntax of Location header field to allow URI references (including
3504  relative references and fragments), as referred symbol "absoluteURI" wasn't
3505  what was expected, and add some clarifications as to when use of fragments
3506  would not be appropriate.
3507  (<xref target="header.location"/>)
3508</t>
3509<t>
3510  Restrict Max-Forwards header field to OPTIONS and TRACE (previously,
3511  extension methods could have used it as well).
3512  (<xref target="header.max-forwards"/>)
3513</t>
3514<t>
3515  Allow Referer field value of "about:blank" as alternative to not specifying it.
3516  (<xref target="header.referer"/>)
3517</t>
3518<t>
3519  In the description of the Server header field, the Via field
3520  was described as a SHOULD. The requirement was and is stated
3521  correctly in the description of the Via header field in &header-via;.
3522  (<xref target="header.server"/>)
3523</t>
3524</section>
3525
3526<?BEGININC p2-semantics.abnf-appendix ?>
3527<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3528<figure>
3529<artwork type="abnf" name="p2-semantics.parsed-abnf">
3530<x:ref>Accept</x:ref> = &lt;Accept, defined in [Part3], Section 6.1&gt;
3531<x:ref>Accept-Charset</x:ref> = &lt;Accept-Charset, defined in [Part3], Section 6.2&gt;
3532<x:ref>Accept-Encoding</x:ref> = &lt;Accept-Encoding, defined in [Part3], Section 6.3&gt;
3533<x:ref>Accept-Language</x:ref> = &lt;Accept-Language, defined in [Part3], Section 6.4&gt;
3534<x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in [Part5], Section 5.1&gt;
3535<x:ref>Age</x:ref> = &lt;Age, defined in [Part6], Section 3.1&gt;
3536<x:ref>Allow</x:ref> = "Allow:" OWS Allow-v
3537<x:ref>Allow-v</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3538<x:ref>Authorization</x:ref> = &lt;Authorization, defined in [Part7], Section 4.1&gt;
3539
3540<x:ref>ETag</x:ref> = &lt;ETag, defined in [Part4], Section 6.1&gt;
3541<x:ref>Expect</x:ref> = "Expect:" OWS Expect-v
3542<x:ref>Expect-v</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3543
3544<x:ref>From</x:ref> = "From:" OWS From-v
3545<x:ref>From-v</x:ref> = mailbox
3546
3547<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 6.1&gt;
3548<x:ref>Host</x:ref> = &lt;Host, defined in [Part1], Section 2.6&gt;
3549
3550<x:ref>If-Match</x:ref> = &lt;If-Match, defined in [Part4], Section 6.2&gt;
3551If-Modified-Since =
3552 &lt;If-Modified-Since, defined in [Part4], Section 6.3&gt;
3553<x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in [Part4], Section 6.4&gt;
3554<x:ref>If-Range</x:ref> = &lt;If-Range, defined in [Part5], Section 5.3&gt;
3555If-Unmodified-Since =
3556 &lt;If-Unmodified-Since, defined in [Part4], Section 6.5&gt;
3557
3558<x:ref>Location</x:ref> = "Location:" OWS Location-v
3559<x:ref>Location-v</x:ref> = URI-reference
3560
3561<x:ref>Max-Forwards</x:ref> = "Max-Forwards:" OWS Max-Forwards-v
3562<x:ref>Max-Forwards-v</x:ref> = 1*DIGIT
3563<x:ref>Method</x:ref> = %x4F.50.54.49.4F.4E.53 ; OPTIONS
3564 / %x47.45.54 ; GET
3565 / %x48.45.41.44 ; HEAD
3566 / %x50.4F.53.54 ; POST
3567 / %x50.55.54 ; PUT
3568 / %x44.45.4C.45.54.45 ; DELETE
3569 / %x54.52.41.43.45 ; TRACE
3570 / %x43.4F.4E.4E.45.43.54 ; CONNECT
3571 / extension-method
3572
3573<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
3574
3575Proxy-Authenticate =
3576 &lt;Proxy-Authenticate, defined in [Part7], Section 4.2&gt;
3577Proxy-Authorization =
3578 &lt;Proxy-Authorization, defined in [Part7], Section 4.3&gt;
3579
3580<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3581<x:ref>Range</x:ref> = &lt;Range, defined in [Part5], Section 5.4&gt;
3582<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
3583<x:ref>Referer</x:ref> = "Referer:" OWS Referer-v
3584<x:ref>Referer-v</x:ref> = absolute-URI / partial-URI
3585<x:ref>Retry-After</x:ref> = "Retry-After:" OWS Retry-After-v
3586<x:ref>Retry-After-v</x:ref> = HTTP-date / delta-seconds
3587
3588<x:ref>Server</x:ref> = "Server:" OWS Server-v
3589<x:ref>Server-v</x:ref> = product *( RWS ( product / comment ) )
3590<x:ref>Status-Code</x:ref> = 3DIGIT
3591
3592<x:ref>TE</x:ref> = &lt;TE, defined in [Part1], Section 9.5&gt;
3593
3594<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.6&gt;
3595<x:ref>User-Agent</x:ref> = "User-Agent:" OWS User-Agent-v
3596<x:ref>User-Agent-v</x:ref> = product *( RWS ( product / comment ) )
3597
3598<x:ref>Vary</x:ref> = &lt;Vary, defined in [Part6], Section 3.5&gt;
3599
3600WWW-Authenticate =
3601 &lt;WWW-Authenticate, defined in [Part7], Section 4.4&gt;
3602
3603<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.6&gt;
3604
3605<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2&gt;
3606
3607<x:ref>delta-seconds</x:ref> = 1*DIGIT
3608
3609<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
3610<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
3611<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
3612 *expect-params ]
3613<x:ref>extension-method</x:ref> = token
3614
3615<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
3616
3617<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
3618
3619<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.6&gt;
3620<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 6.3&gt;
3621
3622<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
3623
3624<x:ref>request-header</x:ref> = Accept / Accept-Charset / Accept-Encoding /
3625 Accept-Language / Authorization / Expect / From / Host / If-Match /
3626 If-Modified-Since / If-None-Match / If-Range / If-Unmodified-Since /
3627 Max-Forwards / Proxy-Authorization / Range / Referer / TE /
3628 User-Agent
3629<x:ref>response-header</x:ref> = Accept-Ranges / Age / Allow / ETag / Location /
3630 Proxy-Authenticate / Retry-After / Server / Vary / WWW-Authenticate
3631
3632<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
3633</artwork>
3634</figure>
3635<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
3636; Reason-Phrase defined but not used
3637; Status-Code defined but not used
3638; request-header defined but not used
3639; response-header defined but not used
3640</artwork></figure></section>
3641<?ENDINC p2-semantics.abnf-appendix ?>
3642
3643<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3644
3645<section title="Since RFC 2616">
3646<t>
3647  Extracted relevant partitions from <xref target="RFC2616"/>.
3648</t>
3649</section>
3650
3651<section title="Since draft-ietf-httpbis-p2-semantics-00">
3652<t>
3653  Closed issues:
3654  <list style="symbols"> 
3655    <t>
3656      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3657      "Via is a MUST"
3658      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3659    </t>
3660    <t>
3661      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3662      "Fragments allowed in Location"
3663      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3664    </t>
3665    <t>
3666      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3667      "Safe Methods vs Redirection"
3668      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3669    </t>
3670    <t>
3671      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3672      "Revise description of the POST method"
3673      (<eref target="http://purl.org/NET/http-errata#post"/>)
3674    </t>
3675    <t>
3676      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3677      "Normative and Informative references"
3678    </t>
3679    <t>
3680      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3681      "RFC2606 Compliance"
3682    </t>
3683    <t>
3684      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3685      "Informative references"
3686    </t>
3687    <t>
3688      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3689      "Redundant cross-references"
3690    </t>
3691  </list>
3692</t>
3693<t>
3694  Other changes:
3695  <list style="symbols"> 
3696    <t>
3697      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3698    </t>
3699  </list>
3700</t>
3701</section>
3702
3703<section title="Since draft-ietf-httpbis-p2-semantics-01">
3704<t>
3705  Closed issues:
3706  <list style="symbols"> 
3707    <t>
3708      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3709      "PUT side effects"
3710    </t>
3711    <t>
3712      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3713      "Duplicate Host header requirements"
3714    </t>
3715  </list>
3716</t>
3717<t>
3718  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3719  <list style="symbols"> 
3720    <t>
3721      Move "Product Tokens" section (back) into Part 1, as "token" is used
3722      in the definition of the Upgrade header field.
3723    </t>
3724    <t>
3725      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3726    </t>
3727    <t>
3728      Copy definition of delta-seconds from Part6 instead of referencing it.
3729    </t>
3730  </list>
3731</t>
3732</section>
3733
3734<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3735<t>
3736  Closed issues:
3737  <list style="symbols"> 
3738    <t>
3739      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3740      "Requiring Allow in 405 responses"
3741    </t>
3742    <t>
3743      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3744      "Status Code Registry"
3745    </t>
3746    <t>
3747      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3748      "Redirection vs. Location"
3749    </t>
3750    <t>
3751      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3752      "Cacheability of 303 response"
3753    </t>
3754    <t>
3755      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3756      "305 Use Proxy"
3757    </t>
3758    <t>
3759      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3760      "Classification for Allow header"
3761    </t>
3762    <t>
3763      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3764      "PUT - 'store under' vs 'store at'"
3765    </t>
3766  </list>
3767</t>
3768<t>
3769  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3770  <list style="symbols"> 
3771    <t>
3772      Reference RFC 3984, and update header field registrations for headers defined
3773      in this document.
3774    </t>
3775  </list>
3776</t>
3777<t>
3778  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3779  <list style="symbols"> 
3780    <t>
3781      Replace string literals when the string really is case-sensitive (method).
3782    </t>
3783  </list>
3784</t>
3785</section>
3786
3787<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3788<t>
3789  Closed issues:
3790  <list style="symbols"> 
3791    <t>
3792      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
3793      "OPTIONS request bodies"
3794    </t>
3795    <t>
3796      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
3797      "Description of CONNECT should refer to RFC2817"
3798    </t>
3799    <t>
3800      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
3801      "Location Content-Location reference request/response mixup"
3802    </t>
3803  </list>
3804</t>
3805<t>
3806  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
3807  <list style="symbols"> 
3808    <t>
3809      Added initial proposal for registration process, plus initial
3810      content (non-HTTP/1.1 methods to be added by a separate specification).
3811    </t>
3812  </list>
3813</t>
3814</section>
3815
3816<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3817<t>
3818  Closed issues:
3819  <list style="symbols"> 
3820    <t>
3821      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3822      "Content-*"
3823    </t>
3824    <t>
3825      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3826      "RFC 2822 is updated by RFC 5322"
3827    </t>
3828  </list>
3829</t>
3830<t>
3831  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3832  <list style="symbols"> 
3833    <t>
3834      Use "/" instead of "|" for alternatives.
3835    </t>
3836    <t>
3837      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3838      whitespace ("OWS") and required whitespace ("RWS").
3839    </t>
3840    <t>
3841      Rewrite ABNFs to spell out whitespace rules, factor out
3842      header field value format definitions.
3843    </t>
3844  </list>
3845</t>
3846</section>
3847
3848<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3849<t>
3850  Closed issues:
3851  <list style="symbols"> 
3852    <t>
3853      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
3854      "Reason-Phrase BNF"
3855    </t>
3856  </list>
3857</t>
3858<t>
3859  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3860  <list style="symbols"> 
3861    <t>
3862      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3863    </t>
3864  </list>
3865</t>
3866</section>
3867
3868<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
3869<t>
3870  Closed issues:
3871  <list style="symbols"> 
3872    <t>
3873      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
3874      "Clarify when Referer is sent"
3875    </t>
3876    <t>
3877      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
3878      "status codes vs methods"
3879    </t>
3880    <t>
3881      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
3882      "Do not require "updates" relation for specs that register status codes or method names"
3883    </t>
3884  </list>
3885</t>
3886</section>
3887
3888<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
3889<t>
3890  Closed issues:
3891  <list style="symbols"> 
3892    <t>
3893      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
3894      "Idempotency"
3895    </t>
3896    <t>
3897      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
3898      "TRACE security considerations"
3899    </t>
3900    <t>
3901      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
3902      "Clarify rules for determining what entities a response carries"
3903    </t>
3904    <t>
3905      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
3906      "update note citing RFC 1945 and 2068"
3907    </t>
3908    <t>
3909      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
3910      "update note about redirect limit"
3911    </t>
3912    <t>
3913      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
3914      "Location header ABNF should use 'URI'"
3915    </t>
3916    <t>
3917      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
3918      "fragments in Location vs status 303"
3919    </t>
3920    <t>
3921      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
3922      "move IANA registrations for optional status codes"
3923    </t>
3924  </list>
3925</t>
3926<t>
3927  Partly resolved issues:
3928  <list style="symbols"> 
3929    <t>
3930      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
3931      "Are OPTIONS and TRACE safe?"
3932    </t>
3933  </list>
3934</t>
3935</section>
3936
3937<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
3938<t>
3939  Closed issues:
3940  <list style="symbols"> 
3941    <t>
3942      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3943      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
3944      status codes when fixing this previously)
3945    </t>
3946  </list>
3947</t>
3948</section>
3949
3950<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
3951<t>
3952  Closed issues:
3953  <list style="symbols"> 
3954    <t>
3955      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
3956      "Fragment combination / precedence during redirects"
3957    </t>
3958  </list>
3959</t>
3960<t>
3961  Partly resolved issues:
3962  <list style="symbols"> 
3963    <t>
3964      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
3965      "Location header payload handling"
3966    </t>
3967    <t>
3968      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
3969      "Term for the requested resource's URI"
3970    </t>
3971  </list>
3972</t>
3973</section>
3974
3975<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
3976<t>
3977  Closed issues:
3978  <list style="symbols"> 
3979    <t>
3980      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
3981      "Clarify 'Requested Variant'"
3982    </t>
3983    <t>
3984      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
3985      "Clarify entity / representation / variant terminology"
3986    </t>
3987    <t>
3988      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/139"/>:
3989      "Methods and Caching"
3990    </t>
3991    <t>
3992      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/190"/>:
3993      "OPTIONS vs Max-Forwards"
3994    </t>
3995    <t>
3996      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/199"/>:
3997      "Status codes and caching"
3998    </t>
3999    <t>
4000      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
4001      "consider removing the 'changes from 2068' sections"
4002    </t>
4003  </list>
4004</t>
4005</section>
4006
4007<section title="Since draft-ietf-httpbis-p2-semantics-11" anchor="changes.since.11">
4008<t>
4009  Closed issues:
4010  <list style="symbols"> 
4011    <t>
4012      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/229"/>:
4013      "Considerations for new status codes"
4014    </t>
4015    <t>
4016      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/230"/>:
4017      "Considerations for new methods"
4018    </t>
4019    <t>
4020      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/232"/>:
4021      "User-Agent guidelines" (relating to the 'User-Agent' header field)
4022    </t>
4023  </list>
4024</t>
4025</section>
4026
4027<section title="Since draft-ietf-httpbis-p2-semantics-12" anchor="changes.since.12">
4028<t>
4029  Closed issues:
4030  <list style="symbols"> 
4031    <t>
4032      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4033      "Fragment combination / precedence during redirects" (added warning
4034      about having a fragid on the redirect may cause inconvenience in
4035      some cases)
4036    </t>
4037    <t>
4038      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/88"/>:
4039      "205 Bodies"
4040    </t>
4041    <t>
4042      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/203"/>:
4043      "Max-Forwards vs extension methods"
4044    </t>
4045    <t>
4046      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/137"/>:
4047      "duplicate ABNF for Reason-Phrase"
4048    </t>
4049    <t>
4050      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/226"/>:
4051      "proxies not supporting certain methods"
4052    </t>
4053    <t>
4054      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/239"/>:
4055      "Migrate CONNECT from RFC2817 to p2"
4056    </t>
4057    <t>
4058      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/240"/>:
4059      "Migrate Upgrade details from RFC2817"
4060    </t>
4061    <t>
4062      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/225"/>:
4063      "PUT side effect: invalidation or just stale?"
4064    </t>
4065  </list>
4066</t>
4067</section>
4068
4069</section>
4070
4071</back>
4072</rfc>
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