source: draft-ietf-httpbis/latest/p2-semantics.xml @ 1136

Last change on this file since 1136 was 1136, checked in by julian.reschke@…, 9 years ago

remove unneeded line break in ABNF

  • Property svn:eol-style set to native
File size: 170.0 KB
Line 
1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns='http://purl.org/net/xml2rfc/ext'>SHOULD NOT</bcp14>">
14  <!ENTITY ID-VERSION "latest">
15  <!ENTITY ID-MONTH "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"/>
436  <x:ref>Method</x:ref>         = <x:ref>token</x:ref>
437</artwork></figure>
438<t>
439   The list of methods allowed by a resource can be specified in an
440   Allow header field (<xref target="header.allow"/>). The status code of the response
441   always notifies the client whether a method is currently allowed on a
442   resource, since the set of allowed methods can change dynamically. An
443   origin server &SHOULD; respond with the status code 405 (Method Not Allowed)
444   if the method is known by the origin server but not allowed for the
445   resource, and 501 (Not Implemented) if the method is
446   unrecognized or not implemented by the origin server. The methods GET
447   and HEAD &MUST; be supported by all general-purpose servers. All other
448   methods are &OPTIONAL;; however, if the above methods are implemented,
449   they &MUST; be implemented with the same semantics as those specified
450   in <xref target="method.definitions"/>.
451</t>
452
453<section title="Overview of Methods" anchor="overview.of.methods">
454<t>
455  The methods listed below are defined in <xref target="method.definitions"/>.
456</t>
457<texttable align="left">
458  <ttcol>Method Name</ttcol><ttcol>Defined in...</ttcol>
459 
460  <c>OPTIONS</c> <c><xref target="OPTIONS"/></c>
461  <c>GET</c> <c><xref target="GET"/></c>
462  <c>HEAD</c> <c><xref target="HEAD"/></c>
463  <c>POST</c> <c><xref target="POST"/></c>
464  <c>PUT</c> <c><xref target="PUT"/></c>
465  <c>DELETE</c> <c><xref target="DELETE"/></c>
466  <c>TRACE</c> <c><xref target="TRACE"/></c>
467  <c>CONNECT</c> <c><xref target="CONNECT"/></c>
468</texttable>
469<t>
470  Note that this list is not exhaustive &mdash; it does not include methods defined
471  in other specifications.
472</t>
473</section>
474
475<section title="Method Registry" anchor="method.registry">
476<t>
477  The HTTP Method Registry defines the name space for the Method token in the
478  Request line of an HTTP request.
479</t>
480<t>
481  Registrations &MUST; include the following fields:
482  <list style="symbols">
483    <t>Method Name (see <xref target="method"/>)</t>
484    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
485    <t>Pointer to specification text</t>
486  </list>
487</t>
488<t>
489  Values to be added to this name space are subject to IETF review
490  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
491</t>
492<t>
493  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
494</t>
495
496<section title="Considerations for New Methods" anchor="considerations.for.new.methods">
497<t>
498   When it is necessary to express new semantics for a HTTP request that
499   aren't specific to a single application or media type, and currently defined
500   methods are inadequate, it may be appropriate to register a new method.
501</t>
502<t>
503   HTTP methods are generic; that is, they are potentially applicable to any
504   resource, not just one particular media type, "type" of resource, or
505   application. As such, it is preferred that new HTTP methods be registered
506   in a document that isn't specific to a single application, so that this is
507   clear.
508</t>
509<t>
510   Due to the parsing rules defined in &message-body;, definitions of HTTP
511   methods cannot prohibit the presence of a message-body on either the request
512   or the response message (with responses to HEAD requests being the single
513   exception). Definitions of new methods cannot change this rule, but they can
514   specify that only zero-length bodies (as opposed to absent bodies) are allowed.
515</t>
516<t>
517   New method definitions need to indicate whether they are safe (<xref
518   target="safe.methods"/>) and whether they are idempotent (<xref
519   target="idempotent.methods"/>). They also need to state whether they can be
520   cached (&caching;); in particular what conditions a cache may store the
521   response, and under what conditions such a stored response may be used to
522   satisfy a subsequent request.
523</t>
524</section>
525
526</section>
527</section>
528
529<section title="Request Header Fields" anchor="request.header.fields">
530  <x:anchor-alias value="request-header"/>
531<t>
532   The request-header fields allow the client to pass additional
533   information about the request, and about the client itself, to the
534   server. These fields act as request modifiers, with semantics
535   equivalent to the parameters on a programming language method
536   invocation.
537</t>
538<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
539  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
540                 / <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
541                 / <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
542                 / <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
543                 / <x:ref>Authorization</x:ref>            ; &header-authorization;
544                 / <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
545                 / <x:ref>From</x:ref>                     ; <xref target="header.from"/>
546                 / <x:ref>Host</x:ref>                     ; &header-host;
547                 / <x:ref>If-Match</x:ref>                 ; &header-if-match;
548                 / <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
549                 / <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
550                 / <x:ref>If-Range</x:ref>                 ; &header-if-range;
551                 / <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
552                 / <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
553                 / <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
554                 / <x:ref>Range</x:ref>                    ; &header-range;
555                 / <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
556                 / <x:ref>TE</x:ref>                       ; &header-te;
557                 / <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
558</artwork></figure>
559<t>
560   Request-header field names can be extended reliably only in
561   combination with a change in the protocol version. However, new or
562   experimental header fields &MAY; be given the semantics of request-header
563   fields if all parties in the communication recognize them to
564   be request-header fields.
565</t>
566</section>
567
568<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
569  <x:anchor-alias value="Reason-Phrase"/>
570  <x:anchor-alias value="Status-Code"/>
571  <x:anchor-alias value="extension-code"/>
572<t>
573   The Status-Code element is a 3-digit integer result code of the attempt to
574   understand and satisfy the request.
575</t>
576<t>
577   The Reason-Phrase is intended to give a short textual description of the
578   Status-Code and is intended for the human user. The client is not required
579   to examine or display the Reason-Phrase.
580</t>
581<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"/>
582  <x:ref>Status-Code</x:ref>    = 3<x:ref>DIGIT</x:ref>
583  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
584</artwork></figure>
585<t>
586   HTTP status codes are extensible. HTTP applications are not required
587   to understand the meaning of all registered status codes, though such
588   understanding is obviously desirable. However, applications &MUST;
589   understand the class of any status code, as indicated by the first
590   digit, and treat any unrecognized response as being equivalent to the
591   x00 status code of that class, with the exception that an
592   unrecognized response &MUST-NOT; be cached. For example, if an
593   unrecognized status code of 431 is received by the client, it can
594   safely assume that there was something wrong with its request and
595   treat the response as if it had received a 400 status code. In such
596   cases, user agents &SHOULD; present to the user the representation enclosed
597   with the response, since that representation is likely to include human-readable
598   information which will explain the unusual status.
599</t>
600
601<section title="Overview of Status Codes" anchor="overview.of.status.codes">
602<t> 
603   The status codes listed below are defined in <xref target="status.codes"/>,
604   &p4-status-codes;, &p5-status-codes;, and &p7-status-codes;. The reason
605   phrases listed here are only recommendations &mdash; they can be replaced
606   by local equivalents without affecting the protocol.
607</t>
608<texttable align="left">
609  <ttcol>Status-Code</ttcol>
610  <ttcol>Reason-Phrase</ttcol>
611  <ttcol>Defined in...</ttcol>
612 
613  <c>100</c> <c>Continue</c> <c><xref target="status.100"/></c>
614  <c>101</c> <c>Switching Protocols</c> <c><xref target="status.101"/></c>
615
616  <c>200</c> <c>OK</c> <c><xref target="status.200"/></c>
617  <c>201</c> <c>Created</c> <c><xref target="status.201"/></c>
618  <c>202</c> <c>Accepted</c> <c><xref target="status.202"/></c>
619  <c>203</c> <c>Non-Authoritative Information</c> <c><xref target="status.203"/></c>
620  <c>204</c> <c>No Content</c> <c><xref target="status.204"/></c>
621  <c>205</c> <c>Reset Content</c> <c><xref target="status.205"/></c>
622  <c>206</c> <c>Partial Content</c> <c>&status-206;</c>
623
624  <c>300</c> <c>Multiple Choices</c> <c><xref target="status.300"/></c>
625  <c>301</c> <c>Moved Permanently</c> <c><xref target="status.301"/></c>
626  <c>302</c> <c>Found</c> <c><xref target="status.302"/></c>
627  <c>303</c> <c>See Other</c> <c><xref target="status.303"/></c>
628  <c>304</c> <c>Not Modified</c> <c>&status-304;</c>
629  <c>305</c> <c>Use Proxy</c> <c><xref target="status.305"/></c>
630  <c>307</c> <c>Temporary Redirect</c> <c><xref target="status.307"/></c>
631
632  <c>400</c> <c>Bad Request</c> <c><xref target="status.400"/></c>
633  <c>401</c> <c>Unauthorized</c> <c>&status-401;</c>
634  <c>402</c> <c>Payment Required</c> <c><xref target="status.402"/></c>
635  <c>403</c> <c>Forbidden</c> <c><xref target="status.403"/></c>
636  <c>404</c> <c>Not Found</c> <c><xref target="status.404"/></c>
637  <c>405</c> <c>Method Not Allowed</c> <c><xref target="status.405"/></c>
638  <c>406</c> <c>Not Acceptable</c> <c><xref target="status.406"/></c>
639  <c>407</c> <c>Proxy Authentication Required</c> <c>&status-407;</c>
640  <c>408</c> <c>Request Time-out</c> <c><xref target="status.408"/></c>
641  <c>409</c> <c>Conflict</c> <c><xref target="status.409"/></c>
642  <c>410</c> <c>Gone</c> <c><xref target="status.410"/></c>
643  <c>411</c> <c>Length Required</c> <c><xref target="status.411"/></c>
644  <c>412</c> <c>Precondition Failed</c> <c>&status-412;</c>
645  <c>413</c> <c>Request Entity Too Large</c> <c><xref target="status.413"/></c>
646  <c>414</c> <c>URI Too Long</c> <c><xref target="status.414"/></c>
647  <c>415</c> <c>Unsupported Media Type</c> <c><xref target="status.415"/></c>
648  <c>416</c> <c>Requested range not satisfiable</c> <c>&status-416;</c>
649  <c>417</c> <c>Expectation Failed</c> <c><xref target="status.417"/></c>
650  <c>426</c> <c>Upgrade Required</c> <c><xref target="status.426"/></c>
651
652  <c>500</c> <c>Internal Server Error</c> <c><xref target="status.500"/></c>
653  <c>501</c> <c>Not Implemented</c> <c><xref target="status.501"/></c>
654  <c>502</c> <c>Bad Gateway</c> <c><xref target="status.502"/></c>
655  <c>503</c> <c>Service Unavailable</c> <c><xref target="status.503"/></c>
656  <c>504</c> <c>Gateway Time-out</c> <c><xref target="status.504"/></c>
657  <c>505</c> <c>HTTP Version not supported</c> <c><xref target="status.505"/></c>
658</texttable>
659<t>
660   Note that this list is not exhaustive &mdash; it does not include
661   extension status codes defined in other specifications.
662</t>
663</section>
664
665<section title="Status Code Registry" anchor="status.code.registry">
666<t>
667  The HTTP Status Code Registry defines the name space for the Status-Code
668  token in the Status-Line of an HTTP response.
669</t>
670<t>
671  Values to be added to this name space are subject to IETF review
672  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
673</t>
674<t>
675  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
676</t>
677
678<section title="Considerations for New Status Codes" anchor="considerations.for.new.status.codes">
679<t>
680   When it is necessary to express new semantics for a HTTP response that
681   aren't specific to a single application or media type, and currently defined
682   status codes are inadequate, a new status code can be registered.
683</t>
684<t>
685   HTTP status codes are generic; that is, they are potentially applicable to
686   any resource, not just one particular media type, "type" of resource, or
687   application. As such, it is preferred that new HTTP status codes be
688   registered in a document that isn't specific to a single application, so
689   that this is clear.
690</t>
691<t>
692   Definitions of new HTTP status codes typically explain the request
693   conditions that produce a response containing the status code (e.g.,
694   combinations of request headers and/or method(s)), along with any
695   interactions with response headers (e.g., those that are required, those
696   that modify the semantics of the response).
697</t>
698<t>
699   New HTTP status codes are required to fall under one of the categories
700   defined in <xref target="status.codes"/>. To allow existing parsers to
701   properly handle them, new status codes cannot disallow a response body,
702   although they can mandate a zero-length response body. They can require the
703   presence of one or more particular HTTP response header(s).
704</t>
705<t>
706   Likewise, their definitions can specify that caches are allowed to use
707   heuristics to determine their freshness (see &caching;; by default, it is
708   not allowed), and can define how to determine the resource which they
709   carry a representation for (see <xref
710   target="identifying.response.associated.with.representation"/>; by default,
711   it is anonymous).
712</t>
713</section>
714
715</section>
716
717</section>
718
719<section title="Response Header Fields" anchor="response.header.fields">
720  <x:anchor-alias value="response-header"/>
721<t>
722   The response-header fields allow the server to pass additional
723   information about the response which cannot be placed in the Status-Line.
724   These header fields give information about the server and about
725   further access to the target resource (&effective-request-uri;).
726</t>
727<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
728  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
729                  / <x:ref>Age</x:ref>                     ; &header-age;
730                  / <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
731                  / <x:ref>ETag</x:ref>                    ; &header-etag;
732                  / <x:ref>Location</x:ref>                ; <xref target="header.location"/>
733                  / <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
734                  / <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
735                  / <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
736                  / <x:ref>Vary</x:ref>                    ; &header-vary;
737                  / <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
738</artwork></figure>
739<t>
740   Response-header field names can be extended reliably only in
741   combination with a change in the protocol version. However, new or
742   experimental header fields &MAY; be given the semantics of response-header
743   fields if all parties in the communication recognize them to
744   be response-header fields.
745</t>
746</section>
747
748<section title="Representation" anchor="representation">
749<t>
750   Request and Response messages &MAY; transfer a representation if not otherwise
751   restricted by the request method or response status code. A representation
752   consists of metadata (representation header fields) and data (representation
753   body).  When a complete or partial representation is enclosed in an HTTP message,
754   it is referred to as the payload of the message. HTTP representations
755   are defined in &payload;.
756</t>
757<t>
758   A representation body is only present in a message when a message-body is
759   present, as described in &message-body;. The representation body is obtained
760   from the message-body by decoding any Transfer-Encoding that might
761   have been applied to ensure safe and proper transfer of the message.
762</t>
763
764<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
765<t>
766   It is sometimes necessary to determine an identifier for the resource
767   associated with a representation.
768</t>
769<t>
770   An HTTP request representation, when present, is always associated with an
771   anonymous (i.e., unidentified) resource.
772</t>
773<t>
774   In the common case, an HTTP response is a representation of the target
775   resource (see &effective-request-uri;). However, this is not always the
776   case. To determine the URI of the resource a response is associated with,
777   the following rules are used (with the first applicable one being selected):
778</t>
779<t><list style="numbers">
780   <t>If the response status code is 200 or 203 and the request method was GET,
781   the response payload is a representation of the target resource.</t>
782   <t>If the response status code is 204, 206, or 304 and the request method was GET
783   or HEAD, the response payload is a partial representation of the target
784   resource (see &combining-responses;).</t>
785   <t>If the response has a Content-Location header field, and that URI is the same
786   as the effective request URI, the response payload is a representation of the
787   target resource.</t>
788   <t>If the response has a Content-Location header field, and that URI is not the
789   same as the effective request URI, then the response asserts that its
790   payload is a representation of the resource identified by the
791   Content-Location URI. However, such an assertion cannot be trusted unless
792   it can be verified by other means (not defined by HTTP).</t>
793   <t>Otherwise, the response is a representation of an anonymous (i.e.,
794   unidentified) resource.</t>
795</list></t>
796<t>
797  <cref anchor="TODO-req-uri">
798   The comparison function is going to have to be defined somewhere,
799   because we already need to compare URIs for things like cache invalidation.</cref>
800</t>
801</section>
802
803</section>
804
805
806<section title="Method Definitions" anchor="method.definitions">
807<t>
808   The set of common methods for HTTP/1.1 is defined below. Although
809   this set can be expanded, additional methods cannot be assumed to
810   share the same semantics for separately extended clients and servers.
811</t>
812
813<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
814
815<section title="Safe Methods" anchor="safe.methods">
816<iref item="Safe Methods" primary="true"/>
817<t>
818   Implementors need to be aware that the software represents the user in
819   their interactions over the Internet, and need to allow
820   the user to be aware of any actions they take which might have an
821   unexpected significance to themselves or others.
822</t>
823<t>
824   In particular, the convention has been established that the GET, HEAD,
825   OPTIONS, and TRACE methods &SHOULD-NOT; have the significance of taking an action
826   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
827   This allows user agents to represent other methods, such as POST, PUT
828   and DELETE, in a special way, so that the user is made aware of the
829   fact that a possibly unsafe action is being requested.
830</t>
831<t>
832   Naturally, it is not possible to ensure that the server does not
833   generate side-effects as a result of performing a GET request; in
834   fact, some dynamic resources consider that a feature. The important
835   distinction here is that the user did not request the side-effects,
836   so therefore cannot be held accountable for them.
837</t>
838</section>
839
840<section title="Idempotent Methods" anchor="idempotent.methods">
841<iref item="Idempotent Methods" primary="true"/>
842<t>
843   Methods can also have the property of "idempotence" in that, aside
844   from error or expiration issues, the intended effect of multiple
845   identical requests is the same as for a single request.
846   The methods PUT, DELETE, and all safe methods are idempotent.
847   It is important to note that idempotence refers only to changes
848   requested by the client: a server is free to change its state due
849   to multiple requests for the purpose of tracking those requests,
850   versioning of results, etc.
851</t>
852</section>
853</section>
854
855<section title="OPTIONS" anchor="OPTIONS">
856  <rdf:Description>
857    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
858  </rdf:Description>
859  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
860  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
861<t>
862   The OPTIONS method represents a request for information about the
863   communication options available on the request/response chain
864   identified by the effective request URI. This method allows the client to
865   determine the options and/or requirements associated with a resource,
866   or the capabilities of a server, without implying a resource action
867   or initiating a resource retrieval.
868</t>
869<t>
870   Responses to this method are not cacheable.
871</t>
872<t>
873   If the OPTIONS request includes a message-body (as indicated by the
874   presence of Content-Length or Transfer-Encoding), then the media type
875   &MUST; be indicated by a Content-Type field. Although this
876   specification does not define any use for such a body, future
877   extensions to HTTP might use the OPTIONS body to make more detailed
878   queries on the server.
879</t>
880<t>
881   If the request-target is an asterisk ("*"), the OPTIONS request is
882   intended to apply to the server in general rather than to a specific
883   resource. Since a server's communication options typically depend on
884   the resource, the "*" request is only useful as a "ping" or "no-op"
885   type of method; it does nothing beyond allowing the client to test
886   the capabilities of the server. For example, this can be used to test
887   a proxy for HTTP/1.1 compliance (or lack thereof).
888</t>
889<t>
890   If the request-target is not an asterisk, the OPTIONS request applies
891   only to the options that are available when communicating with that
892   resource.
893</t>
894<t>
895   A 200 response &SHOULD; include any header fields that indicate
896   optional features implemented by the server and applicable to that
897   resource (e.g., Allow), possibly including extensions not defined by
898   this specification. The response body, if any, &SHOULD; also include
899   information about the communication options. The format for such a
900   body is not defined by this specification, but might be defined by
901   future extensions to HTTP. Content negotiation &MAY; be used to select
902   the appropriate response format. If no response body is included, the
903   response &MUST; include a Content-Length field with a field-value of
904   "0".
905</t>
906<t>
907   The Max-Forwards request-header field &MAY; be used to target a
908   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
909   If no Max-Forwards field is present in the request, then the forwarded
910   request &MUST-NOT; include a Max-Forwards field.
911</t>
912</section>
913
914<section title="GET" anchor="GET">
915  <rdf:Description>
916    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
917  </rdf:Description>
918  <iref primary="true" item="GET method" x:for-anchor=""/>
919  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
920<t>
921   The GET method means retrieve whatever information (in the form of a
922   representation) currently corresponds to the target resource.
923</t>
924<t>   
925   If the target resource is a data-producing process, it is the
926   produced data which shall be returned as the representation in the response and not
927   the source text of the process, unless that text happens to be the output of
928   the process.
929</t>
930<t>
931   The semantics of the GET method change to a "conditional GET" if the
932   request message includes an If-Modified-Since, If-Unmodified-Since,
933   If-Match, If-None-Match, or If-Range header field. A conditional GET
934   method requests that the representation be transferred only under the
935   circumstances described by the conditional header field(s). The
936   conditional GET method is intended to reduce unnecessary network
937   usage by allowing cached representations to be refreshed without requiring
938   multiple requests or transferring data already held by the client.
939</t>
940<t>
941   The semantics of the GET method change to a "partial GET" if the
942   request message includes a Range header field. A partial GET requests
943   that only part of the representation be transferred, as described in &header-range;.
944   The partial GET method is intended to reduce unnecessary
945   network usage by allowing partially-retrieved representations to be
946   completed without transferring data already held by the client.
947</t>
948<t>
949   The response to a GET request is cacheable and &MAY; be used to satisfy
950   subsequent GET and HEAD requests (see &caching;).
951</t>
952<t>
953   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
954</t>
955</section>
956
957<section title="HEAD" anchor="HEAD">
958  <rdf:Description>
959    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
960  </rdf:Description>
961  <iref primary="true" item="HEAD method" x:for-anchor=""/>
962  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
963<t>
964   The HEAD method is identical to GET except that the server &MUST-NOT;
965   return a message-body in the response. The metadata contained
966   in the HTTP header fields in response to a HEAD request &SHOULD; be identical
967   to the information sent in response to a GET request. This method can
968   be used for obtaining metadata about the representation implied by the
969   request without transferring the representation body. This method is
970   often used for testing hypertext links for validity, accessibility,
971   and recent modification.
972</t>
973<t>
974   The response to a HEAD request is cacheable and &MAY; be used to satisfy
975   a subsequent HEAD request; see &caching;. It also &MAY; be used to update a previously cached
976   representation from that resource; if the new field values
977   indicate that the cached representation differs from the current representation (as
978   would be indicated by a change in Content-Length, Content-MD5, ETag
979   or Last-Modified), then the cache &MUST; treat the cache entry as
980   stale.
981</t>
982</section>
983
984<section title="POST" anchor="POST">
985  <iref primary="true" item="POST method" x:for-anchor=""/>
986  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
987<t>
988   The POST method is used to request that the origin server accept the
989   representation enclosed in the request as data to be processed by the
990   target resource. POST is designed to allow a uniform method to cover the
991   following functions:
992  <list style="symbols">
993    <t>
994      Annotation of existing resources;
995    </t>
996    <t>
997        Posting a message to a bulletin board, newsgroup, mailing list,
998        or similar group of articles;
999    </t>
1000    <t>
1001        Providing a block of data, such as the result of submitting a
1002        form, to a data-handling process;
1003    </t>
1004    <t>
1005        Extending a database through an append operation.
1006    </t>
1007  </list>
1008</t>
1009<t>
1010   The actual function performed by the POST method is determined by the
1011   server and is usually dependent on the effective request URI.
1012</t>
1013<t>
1014   The action performed by the POST method might not result in a
1015   resource that can be identified by a URI. In this case, either 200
1016   (OK) or 204 (No Content) is the appropriate response status code,
1017   depending on whether or not the response includes a representation that
1018   describes the result.
1019</t>
1020<t>
1021   If a resource has been created on the origin server, the response
1022   &SHOULD; be 201 (Created) and contain a representation which describes the
1023   status of the request and refers to the new resource, and a Location
1024   header field (see <xref target="header.location"/>).
1025</t>
1026<t>
1027   Responses to POST requests are only cacheable when they
1028   include explicit freshness information (see &p6-explicit;). A
1029   cached POST response with a Content-Location header field
1030   (see &header-content-location;) whose value is the effective
1031   Request URI &MAY; be used to satisfy subsequent GET and HEAD requests.
1032</t>
1033<t>
1034   Note that POST caching is not widely implemented.
1035   However, the 303 (See Other) response can be used to direct the
1036   user agent to retrieve a cacheable resource.
1037</t>
1038</section>
1039
1040<section title="PUT" anchor="PUT">
1041  <iref primary="true" item="PUT method" x:for-anchor=""/>
1042  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
1043<t>
1044   The PUT method requests that the enclosed representation be stored at the
1045   effective request URI. If the effective request URI refers to an already
1046   existing resource, the enclosed representation &SHOULD; be considered a
1047   modified version of the one residing on the origin server. Otherwise, if the
1048   effective request URI does not point to an existing resource, and that URI is
1049   capable of being defined as a new resource by the requesting user
1050   agent, the origin server can create the resource with that URI.
1051</t>
1052<t>   
1053   If a new resource is created at the effective request URI, the origin
1054   server &MUST; inform the user agent
1055   via the 201 (Created) response. If an existing resource is modified,
1056   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
1057   to indicate successful completion of the request.
1058</t>
1059<t>   
1060   If the target resource could not be created or modified, an appropriate
1061   error response &SHOULD; be given that reflects the nature of the problem.
1062   The recipient of the representation &MUST-NOT; ignore any Content-*
1063   header fields (headers starting with the prefix "Content-") that it does
1064   not understand or implement
1065   and &MUST; return a 501 (Not Implemented) response in such cases.
1066</t>
1067<t>
1068   Responses to the PUT method are not cacheable. If a PUT request passes
1069   through a cache that has one or more stored responses for the effective
1070   request URI, those stored responses will be invalidated (see
1071   &p6-invalid;).
1072</t>
1073<t>
1074   The fundamental difference between the POST and PUT requests is
1075   reflected in the different meaning of the effective request URI. The URI in a
1076   POST request identifies the resource that will handle the enclosed
1077   representation. That resource might be a data-accepting process, a gateway to
1078   some other protocol, or a document that accepts annotations.
1079   In contrast, the URI in a PUT request identifies the resource for
1080   which enclosed representation is a new or replacement value; the
1081   user agent knows what URI is intended and the server &MUST-NOT; attempt
1082   to apply the request to some other resource.
1083   If the server desires that the request be applied to a different URI,
1084   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
1085   then make its own decision regarding whether or not to redirect the
1086   request.
1087</t>
1088<t>
1089   A single resource &MAY; be identified by many different URIs. For
1090   example, an article might have a URI for identifying "the current
1091   version" which is separate from the URI identifying each particular
1092   version. In this case, a PUT request on a general URI might result in
1093   several other URIs being defined by the origin server.
1094</t>
1095<t>
1096   HTTP/1.1 does not define how a PUT method affects the state of an
1097   origin server.
1098</t>
1099<t>
1100   Header fields in a PUT request that are recognized as representation
1101   metadata &SHOULD; be applied to the resource created or modified by
1102   the PUT.  Unrecognized header fields &SHOULD; be ignored.
1103</t>
1104</section>
1105
1106<section title="DELETE" anchor="DELETE">
1107  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1108  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1109<t>
1110   The DELETE method requests that the origin server delete the target
1111   resource. This method &MAY; be overridden by
1112   human intervention (or other means) on the origin server. The client cannot
1113   be guaranteed that the operation has been carried out, even if the
1114   status code returned from the origin server indicates that the action
1115   has been completed successfully. However, the server &SHOULD-NOT; 
1116   indicate success unless, at the time the response is given, it
1117   intends to delete the resource or move it to an inaccessible
1118   location.
1119</t>
1120<t>
1121   A successful response &SHOULD; be 200 (OK) if the response includes an
1122   representation describing the status, 202 (Accepted) if the action has not
1123   yet been enacted, or 204 (No Content) if the action has been enacted
1124   but the response does not include a representation.
1125</t>
1126<t>
1127   Responses to the DELETE method are not cacheable. If a DELETE request
1128   passes through a cache that has one or more stored responses for the
1129   effective request URI, those stored responses will be invalidated (see
1130   &p6-invalid;).
1131</t>
1132</section>
1133
1134<section title="TRACE" anchor="TRACE">
1135  <rdf:Description>
1136    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1137  </rdf:Description>
1138  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1139  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1140<t>
1141   The TRACE method is used to invoke a remote, application-layer loop-back
1142   of the request message. The final recipient of the request
1143   &SHOULD; reflect the message received back to the client as the
1144   message-body of a 200 (OK) response. The final recipient is either the
1145   origin server or the first proxy or gateway to receive a Max-Forwards
1146   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1147   A TRACE request &MUST-NOT; include a message-body.
1148</t>
1149<t>
1150   TRACE allows the client to see what is being received at the other
1151   end of the request chain and use that data for testing or diagnostic
1152   information. The value of the Via header field (&header-via;) is of
1153   particular interest, since it acts as a trace of the request chain.
1154   Use of the Max-Forwards header field allows the client to limit the
1155   length of the request chain, which is useful for testing a chain of
1156   proxies forwarding messages in an infinite loop.
1157</t>
1158<t>
1159   If the request is valid, the response &SHOULD; have a Content-Type of
1160   "message/http" (see &media-type-message-http;) and contain a message-body
1161   that encloses a copy of the entire request message.
1162   Responses to the TRACE method are not cacheable.
1163</t>
1164</section>
1165
1166<section title="CONNECT" anchor="CONNECT">
1167  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1168  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1169<t>
1170   The CONNECT method is used with a proxy to dynamically switch
1171   the connection to a tunnel.
1172</t>
1173<t>
1174   When using CONNECT, the request-target &MUST; be use the authority form
1175   (&request-target;); i.e., the host name and port number destination of the
1176   requested connection separated by a colon:
1177</t>
1178<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1179CONNECT server.example.com:80 HTTP/1.1
1180Host: server.example.com:80
1181
1182</artwork></figure>
1183<t>
1184   Other HTTP mechanisms can be used normally with the CONNECT method &mdash;
1185   except end-to-end protocol Upgrade requests, since the
1186   tunnel must be established first.
1187</t>
1188<t>
1189   For example, proxy authentication might be used to establish the
1190   authority to create a tunnel:
1191</t>
1192<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1193CONNECT server.example.com:80 HTTP/1.1
1194Host: server.example.com:80
1195Proxy-Authorization: basic aGVsbG86d29ybGQ=
1196
1197</artwork></figure>
1198<t>
1199   Like any other pipelined HTTP/1.1 request, data to be tunnel may be
1200   sent immediately after the blank line. The usual caveats also apply:
1201   data may be discarded if the eventual response is negative, and the
1202   connection may be reset with no response if more than one TCP segment
1203   is outstanding.
1204</t>
1205
1206<section title="Establishing a Tunnel with CONNECT">
1207<t>
1208   Any successful (2xx) response to a CONNECT request indicates that the
1209   proxy has established a connection to the requested host and port,
1210   and has switched to tunneling the current connection to that server
1211   connection.
1212</t>
1213<t>
1214   It may be the case that the proxy itself can only reach the requested
1215   origin server through another proxy.  In this case, the first proxy
1216   &SHOULD; make a CONNECT request of that next proxy, requesting a tunnel
1217   to the authority.  A proxy &MUST-NOT; respond with any 2xx status code
1218   unless it has either a direct or tunnel connection established to the
1219   authority.
1220</t>
1221<t>
1222   An origin server which receives a CONNECT request for itself &MAY;
1223   respond with a 2xx status code to indicate that a connection is
1224   established.
1225</t>
1226<t>
1227   If at any point either one of the peers gets disconnected, any
1228   outstanding data that came from that peer will be passed to the other
1229   one, and after that also the other connection will be terminated by
1230   the proxy. If there is outstanding data to that peer undelivered,
1231   that data will be discarded.
1232</t>
1233
1234</section>
1235</section>
1236</section>
1237
1238
1239<section title="Status Code Definitions" anchor="status.codes">
1240<t>
1241   Each Status-Code is described below, including any metadata required
1242   in the response.
1243</t>
1244
1245<section title="Informational 1xx" anchor="status.1xx">
1246<t>
1247   This class of status code indicates a provisional response,
1248   consisting only of the Status-Line and optional header fields, and is
1249   terminated by an empty line. There are no required header fields for this
1250   class of status code. Since HTTP/1.0 did not define any 1xx status
1251   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1252   except under experimental conditions.
1253</t>
1254<t>
1255   A client &MUST; be prepared to accept one or more 1xx status responses
1256   prior to a regular response, even if the client does not expect a 100
1257   (Continue) status message. Unexpected 1xx status responses &MAY; be
1258   ignored by a user agent.
1259</t>
1260<t>
1261   Proxies &MUST; forward 1xx responses, unless the connection between the
1262   proxy and its client has been closed, or unless the proxy itself
1263   requested the generation of the 1xx response. (For example, if a
1264   proxy adds a "Expect: 100-continue" field when it forwards a request,
1265   then it need not forward the corresponding 100 (Continue)
1266   response(s).)
1267</t>
1268
1269<section title="100 Continue" anchor="status.100">
1270  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1271  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1272<t>
1273   The client &SHOULD; continue with its request. This interim response is
1274   used to inform the client that the initial part of the request has
1275   been received and has not yet been rejected by the server. The client
1276   &SHOULD; continue by sending the remainder of the request or, if the
1277   request has already been completed, ignore this response. The server
1278   &MUST; send a final response after the request has been completed. See
1279   &use100; for detailed discussion of the use and handling of this
1280   status code.
1281</t>
1282</section>
1283
1284<section title="101 Switching Protocols" anchor="status.101">
1285  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1286  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1287<t>
1288   The server understands and is willing to comply with the client's
1289   request, via the Upgrade message header field (&header-upgrade;), for a
1290   change in the application protocol being used on this connection. The
1291   server will switch protocols to those defined by the response's
1292   Upgrade header field immediately after the empty line which
1293   terminates the 101 response.
1294</t>
1295<t>
1296   The protocol &SHOULD; be switched only when it is advantageous to do
1297   so. For example, switching to a newer version of HTTP is advantageous
1298   over older versions, and switching to a real-time, synchronous
1299   protocol might be advantageous when delivering resources that use
1300   such features.
1301</t>
1302</section>
1303</section>
1304
1305<section title="Successful 2xx" anchor="status.2xx">
1306<t>
1307   This class of status code indicates that the client's request was
1308   successfully received, understood, and accepted.
1309</t>
1310
1311<section title="200 OK" anchor="status.200">
1312  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1313  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1314<t>
1315   The request has succeeded. The payload returned with the response
1316   is dependent on the method used in the request, for example:
1317  <list style="hanging">
1318    <t hangText="GET">
1319          a representation of the target resource is sent in the response;
1320    </t>
1321    <t hangText="HEAD">
1322          the same representation as GET, except without the message-body;
1323    </t>
1324    <t hangText="POST">
1325      a representation describing or containing the result of the action;
1326    </t>
1327    <t hangText="TRACE">
1328      a representation containing the request message as received by the
1329      end server.
1330    </t>
1331  </list>
1332</t>
1333<t>
1334   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1335   freshness for 200 responses.
1336</t>
1337</section>
1338
1339<section title="201 Created" anchor="status.201">
1340  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1341  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1342<t>
1343   The request has been fulfilled and has resulted in a new resource being
1344   created. The newly created resource can be referenced by the URI(s)
1345   returned in the payload of the response, with the most specific URI
1346   for the resource given by a Location header field. The response
1347   &SHOULD; include a payload containing a list of resource
1348   characteristics and location(s) from which the user or user agent can
1349   choose the one most appropriate. The payload format is specified by
1350   the media type given in the Content-Type header field. The origin
1351   server &MUST; create the resource before returning the 201 status code.
1352   If the action cannot be carried out immediately, the server &SHOULD;
1353   respond with 202 (Accepted) response instead.
1354</t>
1355<t>
1356   A 201 response &MAY; contain an ETag response header field indicating
1357   the current value of the entity-tag for the representation of the resource
1358   just created (see &header-etag;).
1359</t>
1360</section>
1361
1362<section title="202 Accepted" anchor="status.202">
1363  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1364  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1365<t>
1366   The request has been accepted for processing, but the processing has
1367   not been completed.  The request might or might not eventually be
1368   acted upon, as it might be disallowed when processing actually takes
1369   place. There is no facility for re-sending a status code from an
1370   asynchronous operation such as this.
1371</t>
1372<t>
1373   The 202 response is intentionally non-committal. Its purpose is to
1374   allow a server to accept a request for some other process (perhaps a
1375   batch-oriented process that is only run once per day) without
1376   requiring that the user agent's connection to the server persist
1377   until the process is completed. The representation returned with this
1378   response &SHOULD; include an indication of the request's current status
1379   and either a pointer to a status monitor or some estimate of when the
1380   user can expect the request to be fulfilled.
1381</t>
1382</section>
1383
1384<section title="203 Non-Authoritative Information" anchor="status.203">
1385  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1386  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1387<t>
1388   The returned metadata in the header fields is not the
1389   definitive set as available from the origin server, but is gathered
1390   from a local or a third-party copy. The set presented &MAY; be a subset
1391   or superset of the original version. For example, including local
1392   annotation information about the resource might result in a superset
1393   of the metadata known by the origin server. Use of this
1394   response code is not required and is only appropriate when the
1395   response would otherwise be 200 (OK).
1396</t>
1397<t>
1398   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1399   freshness for 203 responses.
1400</t>
1401
1402</section>
1403
1404<section title="204 No Content" anchor="status.204">
1405  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1406  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1407<t>
1408   The server has successfully fulfilled the request, but there is no
1409   additional content to return in the response payload body.  The
1410   resource metadata and representation metadata in the response message's
1411   header fields refer to the target resource
1412   and its current representation, respectively, after the requested action.
1413   For example, if a 204 status code is received in response to a PUT
1414   and the response contains an ETag header field, then the value of
1415   that field is the current entity-tag for the representation that
1416   was successfully PUT.
1417</t>
1418<t>
1419   If the client is a user agent, it &SHOULD-NOT; change its document view
1420   from that which caused the request to be sent. This response is
1421   primarily intended to allow input for actions to take place without
1422   causing a change to the user agent's active document view, although
1423   any new or updated metadata &SHOULD; be applied to the document
1424   currently in the user agent's active view.
1425</t>
1426<t>
1427   The 204 response &MUST-NOT; include a message-body, and thus is always
1428   terminated by the first empty line after the header fields.
1429</t>
1430</section>
1431
1432<section title="205 Reset Content" anchor="status.205">
1433  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1434  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1435<t>
1436   The server has fulfilled the request and the user agent &SHOULD; reset
1437   the document view which caused the request to be sent. This response
1438   is primarily intended to allow input for actions to take place via
1439   user input, followed by a clearing of the form in which the input is
1440   given so that the user can easily initiate another input action.
1441</t>
1442<t>   
1443   The message-body included with the response &MUST; be empty. Note that
1444   receivers still need to parse the response according to the algorithm defined
1445   in &message-body;.
1446</t>
1447</section>
1448
1449<section title="206 Partial Content" anchor="status.206">
1450  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1451  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1452  <rdf:Description>
1453    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1454  </rdf:Description>
1455<t>
1456   The server has fulfilled the partial GET request for the resource
1457   and the enclosed payload is a partial representation as defined in &status-206;.
1458</t>
1459<t>
1460   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1461   freshness for 206 responses.
1462</t>
1463</section>
1464</section>
1465
1466<section title="Redirection 3xx" anchor="status.3xx">
1467<t>
1468   This class of status code indicates that further action needs to be
1469   taken by the user agent in order to fulfill the request.  The action
1470   required &MAY; be carried out by the user agent without interaction
1471   with the user if and only if the method used in the second request is
1472   known to be "safe", as defined in <xref target="safe.methods"/>.
1473   A client &SHOULD; detect infinite redirection loops, since such loops
1474   generate network traffic for each redirection.
1475</t>
1476<x:note>
1477  <t>
1478    <x:h>Note:</x:h> An earlier version of this specification recommended a
1479    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1480    Content developers need to be aware that some clients might
1481    implement such a fixed limitation.
1482  </t>
1483</x:note>
1484
1485<section title="300 Multiple Choices" anchor="status.300">
1486  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1487  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1488<t>
1489   The target resource has more than one
1490   representation, each with its own specific location, and agent-driven
1491   negotiation information (&content-negotiation;) is being provided so that
1492   the user (or user agent) can select a preferred representation by
1493   redirecting its request to that location.
1494</t>
1495<t>
1496   Unless it was a HEAD request, the response &SHOULD; include a representation
1497   containing a list of representation metadata and location(s) from
1498   which the user or user agent can choose the one most appropriate. The
1499   data format is specified by the media type given in the Content-Type
1500   header field. Depending upon the format and the capabilities of
1501   the user agent, selection of the most appropriate choice &MAY; be
1502   performed automatically. However, this specification does not define
1503   any standard for such automatic selection.
1504</t>
1505<t>
1506   If the server has a preferred choice of representation, it &SHOULD;
1507   include the specific URI for that representation in the Location
1508   field; user agents &MAY; use the Location field value for automatic
1509   redirection.
1510</t>
1511<t>
1512   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1513   freshness for 300 responses.
1514</t>
1515
1516</section>
1517
1518<section title="301 Moved Permanently" anchor="status.301">
1519  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1520  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1521<t>
1522   The target resource has been assigned a new permanent URI and any
1523   future references to this resource &SHOULD; use one of the returned
1524   URIs.  Clients with link editing capabilities ought to automatically
1525   re-link references to the effective request URI to one or more of the new
1526   references returned by the server, where possible.
1527</t>
1528<t>
1529   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1530   freshness for 301 responses.
1531</t>
1532<t>
1533   The new permanent URI &SHOULD; be given by the Location field in the
1534   response. Unless the request method was HEAD, the representation of the
1535   response &SHOULD; contain a short hypertext note with a hyperlink to
1536   the new URI(s).
1537</t>
1538<t>
1539   If the 301 status code is received in response to a request method
1540   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1541   then the request &MAY; be automatically redirected by the user agent without
1542   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1543   request unless it can be confirmed by the user, since this might
1544   change the conditions under which the request was issued.
1545</t>
1546<x:note>
1547  <t>
1548    <x:h>Note:</x:h> When automatically redirecting a POST request after
1549    receiving a 301 status code, some existing HTTP/1.0 user agents
1550    will erroneously change it into a GET request.
1551  </t>
1552</x:note>
1553</section>
1554
1555<section title="302 Found" anchor="status.302">
1556  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1557  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1558<t>
1559   The target resource resides temporarily under a different URI.
1560   Since the redirection might be altered on occasion, the client &SHOULD;
1561   continue to use the effective request URI for future requests.
1562</t>
1563<t>
1564   The temporary URI &SHOULD; be given by the Location field in the
1565   response. Unless the request method was HEAD, the representation of the
1566   response &SHOULD; contain a short hypertext note with a hyperlink to
1567   the new URI(s).
1568</t>
1569<t>
1570   If the 302 status code is received in response to a request method
1571   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1572   then the request &MAY; be automatically redirected by the user agent without
1573   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1574   request unless it can be confirmed by the user, since this might
1575   change the conditions under which the request was issued.
1576</t>
1577<x:note>
1578  <t>
1579    <x:h>Note:</x:h> HTTP/1.0 (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>)
1580    and the first version of HTTP/1.1 (<xref target="RFC2068" x:fmt="," x:sec ="10.3.3"/>)
1581    specify that the client is not allowed to change the method on the
1582    redirected request.  However, most existing user agent implementations
1583    treat 302 as if it were a 303 response, performing a GET on the Location
1584    field-value regardless of the original request method. Therefore, a
1585    previous version of this specification
1586    (<xref target="RFC2616" x:fmt="," x:sec="10.3.3"/>) has added the
1587    status codes
1588    <xref target="status.303" format="none">303</xref> and
1589    <xref target="status.307" format="none">307</xref> for servers that wish
1590    to make unambiguously clear which kind of reaction is expected of the
1591    client.
1592  </t>
1593</x:note>
1594</section>
1595
1596<section title="303 See Other" anchor="status.303">
1597  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1598  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1599<t>
1600   The server directs the user agent to a different resource, indicated
1601   by a URI in the Location header field, that provides an indirect
1602   response to the original request.  The user agent &MAY; perform a GET
1603   request on the URI in the Location field in order to obtain a
1604   representation corresponding to the response, be redirected again,
1605   or end with an error status.  The Location URI is not a substitute
1606   reference for the effective request URI.
1607</t>
1608<t>
1609   The 303 status code is generally applicable to any HTTP method.  It is
1610   primarily used to allow the output of a POST action to redirect
1611   the user agent to a selected resource, since doing so provides the
1612   information corresponding to the POST response in a form that
1613   can be separately identified, bookmarked, and cached independent
1614   of the original request.
1615</t>
1616<t>
1617   A 303 response to a GET request indicates that the requested
1618   resource does not have a representation of its own that can be
1619   transferred by the server over HTTP.  The Location URI indicates a
1620   resource that is descriptive of the target resource, such that the
1621   follow-on representation might be useful to recipients without
1622   implying that it adequately represents the target resource.
1623   Note that answers to the questions of what can be represented, what
1624   representations are adequate, and what might be a useful description
1625   are outside the scope of HTTP and thus entirely determined by the
1626   URI owner(s).
1627</t>
1628<t>
1629   Except for responses to a HEAD request, the representation of a 303
1630   response &SHOULD; contain a short hypertext note with a hyperlink
1631   to the Location URI.
1632</t>
1633</section>
1634
1635<section title="304 Not Modified" anchor="status.304">
1636  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1637  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1638  <rdf:Description>
1639    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1640  </rdf:Description>
1641<t>
1642   The response to the request has not been modified since the conditions
1643   indicated by the client's conditional GET request, as defined in &status-304;.
1644</t>
1645</section>
1646
1647<section title="305 Use Proxy" anchor="status.305">
1648  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1649  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1650<t>
1651   The 305 status code was defined in a previous version of this specification
1652   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1653</t>
1654</section>
1655
1656<section title="306 (Unused)" anchor="status.306">
1657  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1658  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1659<t>
1660   The 306 status code was used in a previous version of the
1661   specification, is no longer used, and the code is reserved.
1662</t>
1663</section>
1664
1665<section title="307 Temporary Redirect" anchor="status.307">
1666  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1667  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1668<t>
1669   The target resource resides temporarily under a different URI.
1670   Since the redirection can change over time, the client &SHOULD;
1671   continue to use the effective request URI for future requests.
1672</t>
1673<t>
1674   The temporary URI &SHOULD; be given by the Location field in the
1675   response. Unless the request method was HEAD, the representation of the
1676   response &SHOULD; contain a short hypertext note with a hyperlink to
1677   the new URI(s), since many pre-HTTP/1.1 user agents do not
1678   understand the 307 status code. Therefore, the note &SHOULD; contain the
1679   information necessary for a user to repeat the original request on
1680   the new URI.
1681</t>
1682<t>
1683   If the 307 status code is received in response to a request method
1684   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1685   then the request &MAY; be automatically redirected by the user agent without
1686   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1687   request unless it can be confirmed by the user, since this might
1688   change the conditions under which the request was issued.
1689</t>
1690</section>
1691</section>
1692
1693<section title="Client Error 4xx" anchor="status.4xx">
1694<t>
1695   The 4xx class of status code is intended for cases in which the
1696   client seems to have erred. Except when responding to a HEAD request,
1697   the server &SHOULD; include a representation containing an explanation of the
1698   error situation, and whether it is a temporary or permanent
1699   condition. These status codes are applicable to any request method.
1700   User agents &SHOULD; display any included representation to the user.
1701</t>
1702<t>
1703   If the client is sending data, a server implementation using TCP
1704   &SHOULD; be careful to ensure that the client acknowledges receipt of
1705   the packet(s) containing the response, before the server closes the
1706   input connection. If the client continues sending data to the server
1707   after the close, the server's TCP stack will send a reset packet to
1708   the client, which might erase the client's unacknowledged input buffers
1709   before they can be read and interpreted by the HTTP application.
1710</t>
1711
1712<section title="400 Bad Request" anchor="status.400">
1713  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1714  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1715<t>
1716   The request could not be understood by the server due to malformed
1717   syntax. The client &SHOULD-NOT; repeat the request without
1718   modifications.
1719</t>
1720</section>
1721
1722<section title="401 Unauthorized" anchor="status.401">
1723  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1724  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1725  <rdf:Description>
1726    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1727  </rdf:Description>
1728<t>
1729   The request requires user authentication (see &status-401;).
1730</t>
1731</section>
1732
1733<section title="402 Payment Required" anchor="status.402">
1734  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1735  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1736<t>
1737   This code is reserved for future use.
1738</t>
1739</section>
1740
1741<section title="403 Forbidden" anchor="status.403">
1742  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1743  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1744<t>
1745   The server understood the request, but is refusing to fulfill it.
1746   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1747   If the request method was not HEAD and the server wishes to make
1748   public why the request has not been fulfilled, it &SHOULD; describe the
1749   reason for the refusal in the representation.  If the server does not wish to
1750   make this information available to the client, the status code 404
1751   (Not Found) can be used instead.
1752</t>
1753</section>
1754
1755<section title="404 Not Found" anchor="status.404">
1756  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1757  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1758<t>
1759   The server has not found anything matching the effective request URI. No
1760   indication is given of whether the condition is temporary or
1761   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1762   knows, through some internally configurable mechanism, that an old
1763   resource is permanently unavailable and has no forwarding address.
1764   This status code is commonly used when the server does not wish to
1765   reveal exactly why the request has been refused, or when no other
1766   response is applicable.
1767</t>
1768</section>
1769
1770<section title="405 Method Not Allowed" anchor="status.405">
1771  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1772  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1773<t>
1774   The method specified in the Request-Line is not allowed for the target
1775   resource. The response &MUST; include an
1776   Allow header field containing a list of valid methods for the requested
1777   resource.
1778</t>
1779</section>
1780
1781<section title="406 Not Acceptable" anchor="status.406">
1782  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1783  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1784<t>
1785   The resource identified by the request is only capable of generating
1786   response representations which have content characteristics not acceptable
1787   according to the accept header fields sent in the request.
1788</t>
1789<t>
1790   Unless it was a HEAD request, the response &SHOULD; include a representation
1791   containing a list of available representation characteristics and location(s)
1792   from which the user or user agent can choose the one most
1793   appropriate. The data format is specified by the media type given
1794   in the Content-Type header field. Depending upon the format and the
1795   capabilities of the user agent, selection of the most appropriate
1796   choice &MAY; be performed automatically. However, this specification
1797   does not define any standard for such automatic selection.
1798</t>
1799<x:note>
1800  <t>
1801    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1802    not acceptable according to the accept header fields sent in the
1803    request. In some cases, this might even be preferable to sending a
1804    406 response. User agents are encouraged to inspect the header fields of
1805    an incoming response to determine if it is acceptable.
1806  </t>
1807</x:note>
1808<t>
1809   If the response could be unacceptable, a user agent &SHOULD;
1810   temporarily stop receipt of more data and query the user for a
1811   decision on further actions.
1812</t>
1813</section>
1814
1815<section title="407 Proxy Authentication Required" anchor="status.407">
1816  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1817  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1818<t>
1819   This code is similar to 401 (Unauthorized), but indicates that the
1820   client must first authenticate itself with the proxy (see &status-407;).
1821</t>
1822</section>
1823
1824<section title="408 Request Timeout" anchor="status.408">
1825  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1826  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1827<t>
1828   The client did not produce a request within the time that the server
1829   was prepared to wait. The client &MAY; repeat the request without
1830   modifications at any later time.
1831</t>
1832</section>
1833
1834<section title="409 Conflict" anchor="status.409">
1835  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1836  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1837<t>
1838   The request could not be completed due to a conflict with the current
1839   state of the resource. This code is only allowed in situations where
1840   it is expected that the user might be able to resolve the conflict
1841   and resubmit the request. The response body &SHOULD; include enough
1842   information for the user to recognize the source of the conflict.
1843   Ideally, the response representation would include enough information for the
1844   user or user agent to fix the problem; however, that might not be
1845   possible and is not required.
1846</t>
1847<t>
1848   Conflicts are most likely to occur in response to a PUT request. For
1849   example, if versioning were being used and the representation being PUT
1850   included changes to a resource which conflict with those made by an
1851   earlier (third-party) request, the server might use the 409 response
1852   to indicate that it can't complete the request. In this case, the
1853   response representation would likely contain a list of the differences
1854   between the two versions in a format defined by the response
1855   Content-Type.
1856</t>
1857</section>
1858
1859<section title="410 Gone" anchor="status.410">
1860  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1861  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1862<t>
1863   The target resource is no longer available at the server and no
1864   forwarding address is known. This condition is expected to be
1865   considered permanent. Clients with link editing capabilities &SHOULD;
1866   delete references to the effective request URI after user approval. If the
1867   server does not know, or has no facility to determine, whether or not
1868   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1869   used instead.
1870</t>
1871<t>
1872   The 410 response is primarily intended to assist the task of web
1873   maintenance by notifying the recipient that the resource is
1874   intentionally unavailable and that the server owners desire that
1875   remote links to that resource be removed. Such an event is common for
1876   limited-time, promotional services and for resources belonging to
1877   individuals no longer working at the server's site. It is not
1878   necessary to mark all permanently unavailable resources as "gone" or
1879   to keep the mark for any length of time &mdash; that is left to the
1880   discretion of the server owner.
1881</t>
1882<t>
1883   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine freshness
1884   for 410 responses.
1885</t>
1886
1887</section>
1888
1889<section title="411 Length Required" anchor="status.411">
1890  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1891  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1892<t>
1893   The server refuses to accept the request without a defined Content-Length.
1894   The client &MAY; repeat the request if it adds a valid
1895   Content-Length header field containing the length of the message-body
1896   in the request message.
1897</t>
1898</section>
1899
1900<section title="412 Precondition Failed" anchor="status.412">
1901  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1902  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1903  <rdf:Description>
1904    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1905  </rdf:Description>
1906<t>
1907   The precondition given in one or more of the request-header fields
1908   evaluated to false when it was tested on the server, as defined in
1909   &status-412;.
1910</t>
1911</section>
1912
1913<section title="413 Request Entity Too Large" anchor="status.413">
1914  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1915  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1916<t>
1917   The server is refusing to process a request because the request
1918   representation is larger than the server is willing or able to process. The
1919   server &MAY; close the connection to prevent the client from continuing
1920   the request.
1921</t>
1922<t>
1923   If the condition is temporary, the server &SHOULD; include a Retry-After
1924   header field to indicate that it is temporary and after what
1925   time the client &MAY; try again.
1926</t>
1927</section>
1928
1929<section title="414 URI Too Long" anchor="status.414">
1930  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
1931  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
1932<t>
1933   The server is refusing to service the request because the effective request URI
1934   is longer than the server is willing to interpret. This rare
1935   condition is only likely to occur when a client has improperly
1936   converted a POST request to a GET request with long query
1937   information, when the client has descended into a URI "black hole" of
1938   redirection (e.g., a redirected URI prefix that points to a suffix of
1939   itself), or when the server is under attack by a client attempting to
1940   exploit security holes present in some servers using fixed-length
1941   buffers for reading or manipulating the effective request URI.
1942</t>
1943</section>
1944
1945<section title="415 Unsupported Media Type" anchor="status.415">
1946  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1947  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1948<t>
1949   The server is refusing to service the request because the representation of
1950   the request is in a format not supported by the target resource
1951   for the requested method.
1952</t>
1953</section>
1954
1955<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1956  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1957  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1958  <rdf:Description>
1959    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1960  </rdf:Description>
1961<t>
1962   The request included a Range request-header field (&header-range;) and none of
1963   the range-specifier values in this field overlap the current extent
1964   of the selected resource. See &status-416;.
1965</t>
1966</section>
1967
1968<section title="417 Expectation Failed" anchor="status.417">
1969  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1970  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1971<t>
1972   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1973   could not be met by this server, or, if the server is a proxy,
1974   the server has unambiguous evidence that the request could not be met
1975   by the next-hop server.
1976</t>
1977</section>
1978
1979<section title="426 Upgrade Required" anchor="status.426">
1980  <iref primary="true" item="426 Upgrade Required (status code)" x:for-anchor=""/>
1981  <iref primary="true" item="Status Codes" subitem="426 Upgrade Required" x:for-anchor=""/>
1982<t>
1983   The request can not be completed without a prior protocol upgrade. This
1984   response &MUST; include an Upgrade header field (&header-upgrade;)
1985   specifying the required protocols.
1986</t>
1987<figure>
1988<preamble>Example:</preamble>
1989<artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1990HTTP/1.1 426 Upgrade Required
1991Upgrade: HTTP/2.0
1992Connection: Upgrade
1993
1994</artwork></figure>
1995<t>
1996   The server &SHOULD; include a message body in the 426 response which
1997   indicates in human readable form the reason for the error and describes any
1998   alternative courses which may be available to the user.
1999</t>
2000</section>
2001</section>
2002
2003<section title="Server Error 5xx" anchor="status.5xx">
2004<t>
2005   Response status codes beginning with the digit "5" indicate cases in
2006   which the server is aware that it has erred or is incapable of
2007   performing the request. Except when responding to a HEAD request, the
2008   server &SHOULD; include a representation containing an explanation of the
2009   error situation, and whether it is a temporary or permanent
2010   condition. User agents &SHOULD; display any included representation to the
2011   user. These response codes are applicable to any request method.
2012</t>
2013
2014<section title="500 Internal Server Error" anchor="status.500">
2015  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
2016  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
2017<t>
2018   The server encountered an unexpected condition which prevented it
2019   from fulfilling the request.
2020</t>
2021</section>
2022
2023<section title="501 Not Implemented" anchor="status.501">
2024  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
2025  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
2026<t>
2027   The server does not support the functionality required to fulfill the
2028   request. This is the appropriate response when the server does not
2029   recognize the request method and is not capable of supporting it for
2030   any resource.
2031</t>
2032</section>
2033
2034<section title="502 Bad Gateway" anchor="status.502">
2035  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
2036  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
2037<t>
2038   The server, while acting as a gateway or proxy, received an invalid
2039   response from the upstream server it accessed in attempting to
2040   fulfill the request.
2041</t>
2042</section>
2043
2044<section title="503 Service Unavailable" anchor="status.503">
2045  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
2046  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
2047<t>
2048   The server is currently unable to handle the request due to a
2049   temporary overloading or maintenance of the server. The implication
2050   is that this is a temporary condition which will be alleviated after
2051   some delay. If known, the length of the delay &MAY; be indicated in a
2052   Retry-After header field. If no Retry-After is given, the client &SHOULD;
2053   handle the response as it would for a 500 response.
2054</t>
2055<x:note>
2056  <t>
2057    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
2058    server must use it when becoming overloaded. Some servers might wish
2059    to simply refuse the connection.
2060  </t>
2061</x:note>
2062</section>
2063
2064<section title="504 Gateway Timeout" anchor="status.504">
2065  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
2066  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
2067<t>
2068   The server, while acting as a gateway or proxy, did not receive a
2069   timely response from the upstream server specified by the URI (e.g.,
2070   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
2071   to access in attempting to complete the request.
2072</t>
2073<x:note>
2074  <t>
2075    <x:h>Note</x:h> to implementors: some deployed proxies are known to
2076    return 400 or 500 when DNS lookups time out.
2077  </t>
2078</x:note>
2079</section>
2080
2081<section title="505 HTTP Version Not Supported" anchor="status.505">
2082  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
2083  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
2084<t>
2085   The server does not support, or refuses to support, the protocol
2086   version that was used in the request message. The server is
2087   indicating that it is unable or unwilling to complete the request
2088   using the same major version as the client, as described in &http-version;,
2089   other than with this error message. The response &SHOULD; contain
2090   a representation describing why that version is not supported and what other
2091   protocols are supported by that server.
2092</t>
2093
2094</section>
2095</section>
2096</section>
2097
2098
2099<section title="Header Field Definitions" anchor="header.fields">
2100<t>
2101   This section defines the syntax and semantics of HTTP/1.1 header fields
2102   related to request and response semantics.
2103</t>
2104
2105<section title="Allow" anchor="header.allow">
2106  <iref primary="true" item="Allow header field" x:for-anchor=""/>
2107  <iref primary="true" item="Header Fields" subitem="Allow" x:for-anchor=""/>
2108  <x:anchor-alias value="Allow"/>
2109  <x:anchor-alias value="Allow-v"/>
2110<t>
2111   The "Allow" response-header field lists the set of methods advertised as
2112   supported by the target resource. The purpose of this field is strictly to
2113   inform the recipient of valid methods associated with the resource.
2114</t>
2115<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
2116  <x:ref>Allow</x:ref>   = "Allow" ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
2117  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
2118</artwork></figure>
2119<t>
2120   Example of use:
2121</t>
2122<figure><artwork type="example">
2123  Allow: GET, HEAD, PUT
2124</artwork></figure>
2125<t>
2126   The actual set of allowed methods is defined by the origin server at the
2127   time of each request.
2128</t>
2129<t>
2130   A proxy &MUST-NOT; modify the Allow header field &mdash; it does not need to
2131   understand all the methods specified in order to handle them according to
2132   the generic message handling rules.
2133</t>
2134</section>
2135
2136<section title="Expect" anchor="header.expect">
2137  <iref primary="true" item="Expect header field" x:for-anchor=""/>
2138  <iref primary="true" item="Header Fields" subitem="Expect" x:for-anchor=""/>
2139  <x:anchor-alias value="Expect"/>
2140  <x:anchor-alias value="Expect-v"/>
2141  <x:anchor-alias value="expectation"/>
2142  <x:anchor-alias value="expectation-extension"/>
2143  <x:anchor-alias value="expect-params"/>
2144<t>
2145   The "Expect" request-header field is used to indicate that particular
2146   server behaviors are required by the client.
2147</t>
2148<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"/>
2149  <x:ref>Expect</x:ref>       = "Expect" ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
2150  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
2151 
2152  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
2153  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
2154                           *<x:ref>expect-params</x:ref> ]
2155  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
2156</artwork></figure>
2157<t>
2158   A server that does not understand or is unable to comply with any of
2159   the expectation values in the Expect field of a request &MUST; respond
2160   with appropriate error status code. The server &MUST; respond with a 417
2161   (Expectation Failed) status code if any of the expectations cannot be met
2162   or, if there are other problems with the request, some other 4xx
2163   status code.
2164</t>
2165<t>
2166   This header field is defined with extensible syntax to allow for
2167   future extensions. If a server receives a request containing an
2168   Expect field that includes an expectation-extension that it does not
2169   support, it &MUST; respond with a 417 (Expectation Failed) status code.
2170</t>
2171<t>
2172   Comparison of expectation values is case-insensitive for unquoted
2173   tokens (including the 100-continue token), and is case-sensitive for
2174   quoted-string expectation-extensions.
2175</t>
2176<t>
2177   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
2178   return a 417 (Expectation Failed) status code if it receives a request
2179   with an expectation that it cannot meet. However, the Expect
2180   request-header field itself is end-to-end; it &MUST; be forwarded if the
2181   request is forwarded.
2182</t>
2183<t>
2184   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
2185   Expect header field.
2186</t>
2187<t>
2188   See &use100; for the use of the 100 (Continue) status code.
2189</t>
2190</section>
2191
2192<section title="From" anchor="header.from">
2193  <iref primary="true" item="From header field" x:for-anchor=""/>
2194  <iref primary="true" item="Header Fields" subitem="From" x:for-anchor=""/>
2195  <x:anchor-alias value="From"/>
2196  <x:anchor-alias value="From-v"/>
2197  <x:anchor-alias value="mailbox"/>
2198<t>
2199   The "From" request-header field, if given, &SHOULD; contain an Internet
2200   e-mail address for the human user who controls the requesting user
2201   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
2202   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
2203</t>
2204<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
2205  <x:ref>From</x:ref>    = "From" ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
2206  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
2207 
2208  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2209</artwork></figure>
2210<t>
2211   An example is:
2212</t>
2213<figure><artwork type="example">
2214  From: webmaster@example.org
2215</artwork></figure>
2216<t>
2217   This header field &MAY; be used for logging purposes and as a means for
2218   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2219   be used as an insecure form of access protection. The interpretation
2220   of this field is that the request is being performed on behalf of the
2221   person given, who accepts responsibility for the method performed. In
2222   particular, robot agents &SHOULD; include this header field so that the
2223   person responsible for running the robot can be contacted if problems
2224   occur on the receiving end.
2225</t>
2226<t>
2227   The Internet e-mail address in this field &MAY; be separate from the
2228   Internet host which issued the request. For example, when a request
2229   is passed through a proxy the original issuer's address &SHOULD; be
2230   used.
2231</t>
2232<t>
2233   The client &SHOULD-NOT;  send the From header field without the user's
2234   approval, as it might conflict with the user's privacy interests or
2235   their site's security policy. It is strongly recommended that the
2236   user be able to disable, enable, and modify the value of this field
2237   at any time prior to a request.
2238</t>
2239</section>
2240
2241<section title="Location" anchor="header.location">
2242  <iref primary="true" item="Location header field" x:for-anchor=""/>
2243  <iref primary="true" item="Header Fields" subitem="Location" x:for-anchor=""/>
2244  <x:anchor-alias value="Location"/>
2245  <x:anchor-alias value="Location-v"/>
2246<t>
2247   The "Location" response-header field is used to identify a newly created
2248   resource, or to redirect the recipient to a different location for
2249   completion of the request.
2250</t>
2251<t>
2252   For 201 (Created) responses, the Location is the URI of the new resource
2253   which was created by the request. For 3xx responses, the location &SHOULD;
2254   indicate the server's preferred URI for automatic redirection to the
2255   resource.
2256</t>
2257<t>
2258   The field value consists of a single URI-reference. When it has the form
2259   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2260   the final value is computed by resolving it against the effective request
2261   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
2262</t>
2263<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
2264  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
2265  <x:ref>Location-v</x:ref>     = <x:ref>URI-reference</x:ref>
2266</artwork></figure>
2267<figure>
2268<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical WSP below, it's necessary this way for xml2rfc-->
2269<artwork type="example">
2270  Location: http://www.example.org/pub/WWW/People.html#tim
2271</artwork></figure><figure><artwork type="example">  Location: /index.html
2272</artwork></figure>
2273<t>
2274   There are circumstances in which a fragment identifier in a Location URI
2275   would not be appropriate:
2276   <list style="symbols">
2277      <t>With a 201 Created response, because in this usage the Location header
2278      field specifies the URI for the entire created resource.</t>
2279      <t>With 305 Use Proxy.</t>
2280   </list>
2281</t>
2282<x:note>
2283  <t>
2284    <x:h>Note:</x:h> This specification does not define precedence rules
2285    for the case where the original URI, as navigated to by the user
2286    agent, and the Location header field value both contain fragment
2287    identifiers. Thus be aware that including fragment identifiers might
2288    inconvenience anyone relying on the semantics of the original URI's
2289    fragment identifier.
2290  </t>
2291</x:note>
2292<x:note>
2293  <t>
2294    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2295    from Location in that the Content-Location identifies the most specific
2296    resource corresponding to the enclosed representation.
2297    It is therefore possible for a response to contain header fields for
2298    both Location and Content-Location.
2299  </t>
2300</x:note>
2301</section>
2302
2303<section title="Max-Forwards" anchor="header.max-forwards">
2304  <iref primary="true" item="Max-Forwards header field" x:for-anchor=""/>
2305  <iref primary="true" item="Header Fields" subitem="Max-Forwards" x:for-anchor=""/>
2306  <x:anchor-alias value="Max-Forwards"/>
2307  <x:anchor-alias value="Max-Forwards-v"/>
2308<t>
2309   The "Max-Forwards" request-header field provides a mechanism with the
2310   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2311   methods to limit the number of times that the request is forwarded by
2312   proxies or gateways. This can be useful when the client is attempting to
2313   trace a request which appears to be failing or looping in mid-chain.
2314</t>
2315<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
2316  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
2317  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
2318</artwork></figure>
2319<t>
2320   The Max-Forwards value is a decimal integer indicating the remaining
2321   number of times this request message can be forwarded.
2322</t>
2323<t>
2324   Each proxy or gateway recipient of a TRACE or OPTIONS request
2325   containing a Max-Forwards header field &MUST; check and update its
2326   value prior to forwarding the request. If the received value is zero
2327   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2328   respond as the final recipient. If the received Max-Forwards value is
2329   greater than zero, then the forwarded message &MUST; contain an updated
2330   Max-Forwards field with a value decremented by one (1).
2331</t>
2332<t>
2333   The Max-Forwards header field &MAY; be ignored for all other methods.
2334</t>
2335</section>
2336
2337<section title="Referer" anchor="header.referer">
2338  <iref primary="true" item="Referer header field" x:for-anchor=""/>
2339  <iref primary="true" item="Header Fields" subitem="Referer" x:for-anchor=""/>
2340  <x:anchor-alias value="Referer"/>
2341  <x:anchor-alias value="Referer-v"/>
2342<t>
2343   The "Referer" [sic] request-header field allows the client to specify the
2344   URI of the resource from which the effective request URI was obtained (the
2345   "referrer", although the header field is misspelled.).
2346</t>
2347<t>
2348   The Referer header field allows servers to generate lists of back-links to
2349   resources for interest, logging, optimized caching, etc. It also allows
2350   obsolete or mistyped links to be traced for maintenance. Some servers use
2351   Referer as a means of controlling where they allow links from (so-called
2352   "deep linking"), but legitimate requests do not always
2353   contain a Referer header field.
2354</t>
2355<t>
2356   If the effective request URI was obtained from a source that does not have its own
2357   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
2358   sent with the value "about:blank", or not be sent at all. Note that this
2359   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2360</t>
2361<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
2362  <x:ref>Referer</x:ref>        = "Referer" ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
2363  <x:ref>Referer-v</x:ref>      = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2364</artwork></figure>
2365<t>
2366   Example:
2367</t>
2368<figure><artwork type="example">
2369  Referer: http://www.example.org/hypertext/Overview.html
2370</artwork></figure>
2371<t>
2372   If the field value is a relative URI, it &SHOULD; be interpreted
2373   relative to the effective request URI. The URI &MUST-NOT; include a fragment. See
2374   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2375</t>
2376</section>
2377
2378<section title="Retry-After" anchor="header.retry-after">
2379  <iref primary="true" item="Retry-After header field" x:for-anchor=""/>
2380  <iref primary="true" item="Header Fields" subitem="Retry-After" x:for-anchor=""/>
2381  <x:anchor-alias value="Retry-After"/>
2382  <x:anchor-alias value="Retry-After-v"/>
2383<t>
2384   The response-header "Retry-After" field can be used with a 503 (Service
2385   Unavailable) response to indicate how long the service is expected to
2386   be unavailable to the requesting client. This field &MAY; also be used
2387   with any 3xx (Redirection) response to indicate the minimum time the
2388   user-agent is asked wait before issuing the redirected request.
2389</t>
2390<t>
2391   The value of this field can be either an HTTP-date or an integer number
2392   of seconds (in decimal) after the time of the response.
2393</t>
2394<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
2395  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
2396  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2397</artwork></figure>
2398<t anchor="rule.delta-seconds">
2399  <x:anchor-alias value="delta-seconds"/>
2400   Time spans are non-negative decimal integers, representing time in
2401   seconds.
2402</t>
2403<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2404  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2405</artwork></figure>
2406<t>
2407   Two examples of its use are
2408</t>
2409<figure><artwork type="example">
2410  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2411  Retry-After: 120
2412</artwork></figure>
2413<t>
2414   In the latter example, the delay is 2 minutes.
2415</t>
2416</section>
2417
2418<section title="Server" anchor="header.server">
2419  <iref primary="true" item="Server header field" x:for-anchor=""/>
2420  <iref primary="true" item="Header Fields" subitem="Server" x:for-anchor=""/>
2421  <x:anchor-alias value="Server"/>
2422  <x:anchor-alias value="Server-v"/>
2423<t>
2424   The "Server" response-header field contains information about the
2425   software used by the origin server to handle the request.
2426</t>
2427<t>
2428   The field can contain multiple product tokens (&product-tokens;) and
2429   comments (&header-fields;) identifying the server and any significant
2430   subproducts. The product tokens are listed in order of their significance
2431   for identifying the application.
2432</t>
2433<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
2434  <x:ref>Server</x:ref>         = "Server" ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
2435  <x:ref>Server-v</x:ref>       = <x:ref>product</x:ref>
2436                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2437</artwork></figure>
2438<t>
2439   Example:
2440</t>
2441<figure><artwork type="example">
2442  Server: CERN/3.0 libwww/2.17
2443</artwork></figure>
2444<t>
2445   If the response is being forwarded through a proxy, the proxy
2446   application &MUST-NOT; modify the Server response-header field. Instead, it
2447   &MUST; include a Via field (as described in &header-via;).
2448</t>
2449<x:note>
2450  <t>
2451    <x:h>Note:</x:h> Revealing the specific software version of the server might
2452    allow the server machine to become more vulnerable to attacks
2453    against software that is known to contain security holes. Server
2454    implementors are encouraged to make this field a configurable
2455    option.
2456  </t>
2457</x:note>
2458</section>
2459
2460<section title="User-Agent" anchor="header.user-agent">
2461  <iref primary="true" item="User-Agent header field" x:for-anchor=""/>
2462  <iref primary="true" item="Header Fields" subitem="User-Agent" x:for-anchor=""/>
2463  <x:anchor-alias value="User-Agent"/>
2464  <x:anchor-alias value="User-Agent-v"/>
2465<t>
2466   The "User-Agent" request-header field contains information about the user
2467   agent originating the request. User agents &SHOULD; include this field with
2468   requests.
2469</t>
2470<t>
2471   Typically, it is used for statistical purposes, the tracing of protocol
2472   violations, and tailoring responses to avoid particular user agent
2473   limitations.
2474</t>
2475<t>
2476   The field can contain multiple product tokens (&product-tokens;)
2477   and comments (&header-fields;) identifying the agent and its
2478   significant subproducts. By convention, the product tokens are listed in
2479   order of their significance for identifying the application.
2480</t>
2481<t>
2482   Because this field is usually sent on every request a user agent makes,
2483   implementations are encouraged not to include needlessly fine-grained
2484   detail, and to limit (or even prohibit) the addition of subproducts by third
2485   parties. Overly long and detailed User-Agent field values make requests
2486   larger and can also be used to identify ("fingerprint") the user against
2487   their wishes.
2488</t>
2489<t>
2490   Likewise, implementations are encouraged not to use the product tokens of
2491   other implementations in order to declare compatibility with them, as this
2492   circumvents the purpose of the field. Finally, they are encouraged not to
2493   use comments to identify products; doing so makes the field value more
2494   difficult to parse.
2495</t>
2496<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
2497  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
2498  <x:ref>User-Agent-v</x:ref>   = <x:ref>product</x:ref> *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2499</artwork></figure>
2500<t>
2501   Example:
2502</t>
2503<figure><artwork type="example">
2504  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2505</artwork></figure>
2506</section>
2507
2508</section>
2509
2510<section title="IANA Considerations" anchor="IANA.considerations">
2511
2512<section title="Method Registry" anchor="method.registration">
2513<t>
2514  The registration procedure for HTTP Methods is defined by
2515  <xref target="method.registry"/> of this document.
2516</t>
2517<t>
2518   The HTTP Method Registry shall be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2519   and be populated with the registrations below:
2520</t>
2521<?BEGININC p2-semantics.iana-methods ?>
2522<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2523<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2524   <ttcol>Method</ttcol>
2525   <ttcol>Safe</ttcol>
2526   <ttcol>Reference</ttcol>
2527   <c>CONNECT</c>
2528   <c>no</c>
2529   <c>
2530      <xref target="CONNECT"/>
2531   </c>
2532   <c>DELETE</c>
2533   <c>no</c>
2534   <c>
2535      <xref target="DELETE"/>
2536   </c>
2537   <c>GET</c>
2538   <c>yes</c>
2539   <c>
2540      <xref target="GET"/>
2541   </c>
2542   <c>HEAD</c>
2543   <c>yes</c>
2544   <c>
2545      <xref target="HEAD"/>
2546   </c>
2547   <c>OPTIONS</c>
2548   <c>yes</c>
2549   <c>
2550      <xref target="OPTIONS"/>
2551   </c>
2552   <c>POST</c>
2553   <c>no</c>
2554   <c>
2555      <xref target="POST"/>
2556   </c>
2557   <c>PUT</c>
2558   <c>no</c>
2559   <c>
2560      <xref target="PUT"/>
2561   </c>
2562   <c>TRACE</c>
2563   <c>yes</c>
2564   <c>
2565      <xref target="TRACE"/>
2566   </c>
2567</texttable>
2568<!--(END)-->
2569<?ENDINC p2-semantics.iana-methods ?>
2570</section>
2571
2572<section title="Status Code Registry" anchor="status.code.registration">
2573<t>
2574   The registration procedure for HTTP Status Codes &mdash; previously defined
2575   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> &mdash; is now defined
2576   by <xref target="status.code.registry"/> of this document.
2577</t>
2578<t>
2579   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2580   shall be updated with the registrations below:
2581</t>
2582<?BEGININC p2-semantics.iana-status-codes ?>
2583<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2584<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2585   <ttcol>Value</ttcol>
2586   <ttcol>Description</ttcol>
2587   <ttcol>Reference</ttcol>
2588   <c>100</c>
2589   <c>Continue</c>
2590   <c>
2591      <xref target="status.100"/>
2592   </c>
2593   <c>101</c>
2594   <c>Switching Protocols</c>
2595   <c>
2596      <xref target="status.101"/>
2597   </c>
2598   <c>200</c>
2599   <c>OK</c>
2600   <c>
2601      <xref target="status.200"/>
2602   </c>
2603   <c>201</c>
2604   <c>Created</c>
2605   <c>
2606      <xref target="status.201"/>
2607   </c>
2608   <c>202</c>
2609   <c>Accepted</c>
2610   <c>
2611      <xref target="status.202"/>
2612   </c>
2613   <c>203</c>
2614   <c>Non-Authoritative Information</c>
2615   <c>
2616      <xref target="status.203"/>
2617   </c>
2618   <c>204</c>
2619   <c>No Content</c>
2620   <c>
2621      <xref target="status.204"/>
2622   </c>
2623   <c>205</c>
2624   <c>Reset Content</c>
2625   <c>
2626      <xref target="status.205"/>
2627   </c>
2628   <c>300</c>
2629   <c>Multiple Choices</c>
2630   <c>
2631      <xref target="status.300"/>
2632   </c>
2633   <c>301</c>
2634   <c>Moved Permanently</c>
2635   <c>
2636      <xref target="status.301"/>
2637   </c>
2638   <c>302</c>
2639   <c>Found</c>
2640   <c>
2641      <xref target="status.302"/>
2642   </c>
2643   <c>303</c>
2644   <c>See Other</c>
2645   <c>
2646      <xref target="status.303"/>
2647   </c>
2648   <c>305</c>
2649   <c>Use Proxy</c>
2650   <c>
2651      <xref target="status.305"/>
2652   </c>
2653   <c>306</c>
2654   <c>(Unused)</c>
2655   <c>
2656      <xref target="status.306"/>
2657   </c>
2658   <c>307</c>
2659   <c>Temporary Redirect</c>
2660   <c>
2661      <xref target="status.307"/>
2662   </c>
2663   <c>400</c>
2664   <c>Bad Request</c>
2665   <c>
2666      <xref target="status.400"/>
2667   </c>
2668   <c>402</c>
2669   <c>Payment Required</c>
2670   <c>
2671      <xref target="status.402"/>
2672   </c>
2673   <c>403</c>
2674   <c>Forbidden</c>
2675   <c>
2676      <xref target="status.403"/>
2677   </c>
2678   <c>404</c>
2679   <c>Not Found</c>
2680   <c>
2681      <xref target="status.404"/>
2682   </c>
2683   <c>405</c>
2684   <c>Method Not Allowed</c>
2685   <c>
2686      <xref target="status.405"/>
2687   </c>
2688   <c>406</c>
2689   <c>Not Acceptable</c>
2690   <c>
2691      <xref target="status.406"/>
2692   </c>
2693   <c>407</c>
2694   <c>Proxy Authentication Required</c>
2695   <c>
2696      <xref target="status.407"/>
2697   </c>
2698   <c>408</c>
2699   <c>Request Timeout</c>
2700   <c>
2701      <xref target="status.408"/>
2702   </c>
2703   <c>409</c>
2704   <c>Conflict</c>
2705   <c>
2706      <xref target="status.409"/>
2707   </c>
2708   <c>410</c>
2709   <c>Gone</c>
2710   <c>
2711      <xref target="status.410"/>
2712   </c>
2713   <c>411</c>
2714   <c>Length Required</c>
2715   <c>
2716      <xref target="status.411"/>
2717   </c>
2718   <c>413</c>
2719   <c>Request Entity Too Large</c>
2720   <c>
2721      <xref target="status.413"/>
2722   </c>
2723   <c>414</c>
2724   <c>URI Too Long</c>
2725   <c>
2726      <xref target="status.414"/>
2727   </c>
2728   <c>415</c>
2729   <c>Unsupported Media Type</c>
2730   <c>
2731      <xref target="status.415"/>
2732   </c>
2733   <c>417</c>
2734   <c>Expectation Failed</c>
2735   <c>
2736      <xref target="status.417"/>
2737   </c>
2738   <c>426</c>
2739   <c>Upgrade Required</c>
2740   <c>
2741      <xref target="status.426"/>
2742   </c>
2743   <c>500</c>
2744   <c>Internal Server Error</c>
2745   <c>
2746      <xref target="status.500"/>
2747   </c>
2748   <c>501</c>
2749   <c>Not Implemented</c>
2750   <c>
2751      <xref target="status.501"/>
2752   </c>
2753   <c>502</c>
2754   <c>Bad Gateway</c>
2755   <c>
2756      <xref target="status.502"/>
2757   </c>
2758   <c>503</c>
2759   <c>Service Unavailable</c>
2760   <c>
2761      <xref target="status.503"/>
2762   </c>
2763   <c>504</c>
2764   <c>Gateway Timeout</c>
2765   <c>
2766      <xref target="status.504"/>
2767   </c>
2768   <c>505</c>
2769   <c>HTTP Version Not Supported</c>
2770   <c>
2771      <xref target="status.505"/>
2772   </c>
2773</texttable>
2774<!--(END)-->
2775<?ENDINC p2-semantics.iana-status-codes ?>
2776</section>
2777<section title="Header Field Registration" anchor="header.field.registration">
2778<t>
2779   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
2780   with the permanent registrations below (see <xref target="RFC3864"/>):
2781</t>
2782<?BEGININC p2-semantics.iana-headers ?>
2783<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2784<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2785   <ttcol>Header Field Name</ttcol>
2786   <ttcol>Protocol</ttcol>
2787   <ttcol>Status</ttcol>
2788   <ttcol>Reference</ttcol>
2789
2790   <c>Allow</c>
2791   <c>http</c>
2792   <c>standard</c>
2793   <c>
2794      <xref target="header.allow"/>
2795   </c>
2796   <c>Expect</c>
2797   <c>http</c>
2798   <c>standard</c>
2799   <c>
2800      <xref target="header.expect"/>
2801   </c>
2802   <c>From</c>
2803   <c>http</c>
2804   <c>standard</c>
2805   <c>
2806      <xref target="header.from"/>
2807   </c>
2808   <c>Location</c>
2809   <c>http</c>
2810   <c>standard</c>
2811   <c>
2812      <xref target="header.location"/>
2813   </c>
2814   <c>Max-Forwards</c>
2815   <c>http</c>
2816   <c>standard</c>
2817   <c>
2818      <xref target="header.max-forwards"/>
2819   </c>
2820   <c>Referer</c>
2821   <c>http</c>
2822   <c>standard</c>
2823   <c>
2824      <xref target="header.referer"/>
2825   </c>
2826   <c>Retry-After</c>
2827   <c>http</c>
2828   <c>standard</c>
2829   <c>
2830      <xref target="header.retry-after"/>
2831   </c>
2832   <c>Server</c>
2833   <c>http</c>
2834   <c>standard</c>
2835   <c>
2836      <xref target="header.server"/>
2837   </c>
2838   <c>User-Agent</c>
2839   <c>http</c>
2840   <c>standard</c>
2841   <c>
2842      <xref target="header.user-agent"/>
2843   </c>
2844</texttable>
2845<!--(END)-->
2846<?ENDINC p2-semantics.iana-headers ?>
2847<t>
2848   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2849</t>
2850</section>
2851</section>
2852
2853<section title="Security Considerations" anchor="security.considerations">
2854<t>
2855   This section is meant to inform application developers, information
2856   providers, and users of the security limitations in HTTP/1.1 as
2857   described by this document. The discussion does not include
2858   definitive solutions to the problems revealed, though it does make
2859   some suggestions for reducing security risks.
2860</t>
2861
2862<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2863<t>
2864   Like any generic data transfer protocol, HTTP cannot regulate the
2865   content of the data that is transferred, nor is there any a priori
2866   method of determining the sensitivity of any particular piece of
2867   information within the context of any given request. Therefore,
2868   applications &SHOULD; supply as much control over this information as
2869   possible to the provider of that information. Four header fields are
2870   worth special mention in this context: Server, Via, Referer and From.
2871</t>
2872<t>
2873   Revealing the specific software version of the server might allow the
2874   server machine to become more vulnerable to attacks against software
2875   that is known to contain security holes. Implementors &SHOULD; make the
2876   Server header field a configurable option.
2877</t>
2878<t>
2879   Proxies which serve as a portal through a network firewall &SHOULD;
2880   take special precautions regarding the transfer of header information
2881   that identifies the hosts behind the firewall. In particular, they
2882   &SHOULD; remove, or replace with sanitized versions, any Via fields
2883   generated behind the firewall.
2884</t>
2885<t>
2886   The Referer header field allows reading patterns to be studied and reverse
2887   links drawn. Although it can be very useful, its power can be abused
2888   if user details are not separated from the information contained in
2889   the Referer. Even when the personal information has been removed, the
2890   Referer header field might indicate a private document's URI whose
2891   publication would be inappropriate.
2892</t>
2893<t>
2894   The information sent in the From field might conflict with the user's
2895   privacy interests or their site's security policy, and hence it
2896   &SHOULD-NOT;  be transmitted without the user being able to disable,
2897   enable, and modify the contents of the field. The user &MUST; be able
2898   to set the contents of this field within a user preference or
2899   application defaults configuration.
2900</t>
2901<t>
2902   We suggest, though do not require, that a convenient toggle interface
2903   be provided for the user to enable or disable the sending of From and
2904   Referer information.
2905</t>
2906<t>
2907   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref
2908   target="header.server"/>) header fields can sometimes be used to determine
2909   that a specific client or server have a particular security hole which might
2910   be exploited. Unfortunately, this same information is often used for other
2911   valuable purposes for which HTTP currently has no better mechanism.
2912</t>
2913<t>
2914   Furthermore, the User-Agent header field may contain enough entropy to be
2915   used, possibly in conjunction with other material, to uniquely identify the
2916   user.
2917</t>
2918<t>
2919   Some methods, like TRACE (<xref target="TRACE"/>), expose information
2920   that was sent in request header fields within the body of their response.
2921   Clients &SHOULD; be careful with sensitive information, like Cookies,
2922   Authorization credentials and other header fields that might be used to
2923   collect data from the client.
2924</t> 
2925</section>
2926
2927<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2928<t>
2929   Because the source of a link might be private information or might
2930   reveal an otherwise private information source, it is strongly
2931   recommended that the user be able to select whether or not the
2932   Referer field is sent. For example, a browser client could have a
2933   toggle switch for browsing openly/anonymously, which would
2934   respectively enable/disable the sending of Referer and From
2935   information.
2936</t>
2937<t>
2938   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2939   HTTP request if the referring page was transferred with a secure
2940   protocol.
2941</t>
2942<t>
2943   Authors of services &SHOULD-NOT; use GET-based forms for the submission of
2944   sensitive data because that data will be placed in the request-target. Many
2945   existing servers, proxies, and user agents log or display the request-target
2946   in places where it might be visible to third parties. Such services can
2947   use POST-based form submission instead.
2948</t>
2949</section>
2950
2951<section title="Location Headers and Spoofing" anchor="location.spoofing">
2952<t>
2953   If a single server supports multiple organizations that do not trust
2954   one another, then it &MUST; check the values of Location and Content-Location
2955   header fields in responses that are generated under control of
2956   said organizations to make sure that they do not attempt to
2957   invalidate resources over which they have no authority.
2958</t>
2959</section>
2960
2961<section title="Security Considerations for CONNECT">
2962<t>
2963   Since tunneled data is opaque to the proxy, there are additional
2964   risks to tunneling to other well-known or reserved ports.
2965   A HTTP client CONNECTing to port 25 could relay spam
2966   via SMTP, for example. As such, proxies &SHOULD; restrict CONNECT
2967   access to a small number of known ports.
2968</t>
2969</section>
2970
2971</section>
2972
2973<section title="Acknowledgments" anchor="ack">
2974</section>
2975</middle>
2976<back>
2977
2978<references title="Normative References">
2979
2980<reference anchor="Part1">
2981  <front>
2982    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2983    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2984      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
2985      <address><email>fielding@gbiv.com</email></address>
2986    </author>
2987    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2988      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2989      <address><email>jg@freedesktop.org</email></address>
2990    </author>
2991    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2992      <organization abbrev="HP">Hewlett-Packard Company</organization>
2993      <address><email>JeffMogul@acm.org</email></address>
2994    </author>
2995    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2996      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2997      <address><email>henrikn@microsoft.com</email></address>
2998    </author>
2999    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3000      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3001      <address><email>LMM@acm.org</email></address>
3002    </author>
3003    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3004      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3005      <address><email>paulle@microsoft.com</email></address>
3006    </author>
3007    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3008      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3009      <address><email>timbl@w3.org</email></address>
3010    </author>
3011    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3012      <organization abbrev="W3C">World Wide Web Consortium</organization>
3013      <address><email>ylafon@w3.org</email></address>
3014    </author>
3015    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3016      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3017      <address><email>julian.reschke@greenbytes.de</email></address>
3018    </author>
3019    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3020  </front>
3021  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
3022  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
3023</reference>
3024
3025<reference anchor="Part3">
3026  <front>
3027    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
3028    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3029      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3030      <address><email>fielding@gbiv.com</email></address>
3031    </author>
3032    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3033      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3034      <address><email>jg@freedesktop.org</email></address>
3035    </author>
3036    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3037      <organization abbrev="HP">Hewlett-Packard Company</organization>
3038      <address><email>JeffMogul@acm.org</email></address>
3039    </author>
3040    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3041      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3042      <address><email>henrikn@microsoft.com</email></address>
3043    </author>
3044    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3045      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3046      <address><email>LMM@acm.org</email></address>
3047    </author>
3048    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3049      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3050      <address><email>paulle@microsoft.com</email></address>
3051    </author>
3052    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3053      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3054      <address><email>timbl@w3.org</email></address>
3055    </author>
3056    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3057      <organization abbrev="W3C">World Wide Web Consortium</organization>
3058      <address><email>ylafon@w3.org</email></address>
3059    </author>
3060    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3061      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3062      <address><email>julian.reschke@greenbytes.de</email></address>
3063    </author>
3064    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3065  </front>
3066  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
3067  <x:source href="p3-payload.xml" basename="p3-payload"/>
3068</reference>
3069
3070<reference anchor="Part4">
3071  <front>
3072    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
3073    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3074      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3075      <address><email>fielding@gbiv.com</email></address>
3076    </author>
3077    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3078      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3079      <address><email>jg@freedesktop.org</email></address>
3080    </author>
3081    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3082      <organization abbrev="HP">Hewlett-Packard Company</organization>
3083      <address><email>JeffMogul@acm.org</email></address>
3084    </author>
3085    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3086      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3087      <address><email>henrikn@microsoft.com</email></address>
3088    </author>
3089    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3090      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3091      <address><email>LMM@acm.org</email></address>
3092    </author>
3093    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3094      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3095      <address><email>paulle@microsoft.com</email></address>
3096    </author>
3097    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3098      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3099      <address><email>timbl@w3.org</email></address>
3100    </author>
3101    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3102      <organization abbrev="W3C">World Wide Web Consortium</organization>
3103      <address><email>ylafon@w3.org</email></address>
3104    </author>
3105    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3106      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3107      <address><email>julian.reschke@greenbytes.de</email></address>
3108    </author>
3109    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3110  </front>
3111  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
3112  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
3113</reference>
3114
3115<reference anchor="Part5">
3116  <front>
3117    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
3118    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3119      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3120      <address><email>fielding@gbiv.com</email></address>
3121    </author>
3122    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3123      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3124      <address><email>jg@freedesktop.org</email></address>
3125    </author>
3126    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3127      <organization abbrev="HP">Hewlett-Packard Company</organization>
3128      <address><email>JeffMogul@acm.org</email></address>
3129    </author>
3130    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3131      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3132      <address><email>henrikn@microsoft.com</email></address>
3133    </author>
3134    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3135      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3136      <address><email>LMM@acm.org</email></address>
3137    </author>
3138    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3139      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3140      <address><email>paulle@microsoft.com</email></address>
3141    </author>
3142    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3143      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3144      <address><email>timbl@w3.org</email></address>
3145    </author>
3146    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3147      <organization abbrev="W3C">World Wide Web Consortium</organization>
3148      <address><email>ylafon@w3.org</email></address>
3149    </author>
3150    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3151      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3152      <address><email>julian.reschke@greenbytes.de</email></address>
3153    </author>
3154    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3155  </front>
3156  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
3157  <x:source href="p5-range.xml" basename="p5-range"/>
3158</reference>
3159
3160<reference anchor="Part6">
3161  <front>
3162    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
3163    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3164      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3165      <address><email>fielding@gbiv.com</email></address>
3166    </author>
3167    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3168      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3169      <address><email>jg@freedesktop.org</email></address>
3170    </author>
3171    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3172      <organization abbrev="HP">Hewlett-Packard Company</organization>
3173      <address><email>JeffMogul@acm.org</email></address>
3174    </author>
3175    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3176      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3177      <address><email>henrikn@microsoft.com</email></address>
3178    </author>
3179    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3180      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3181      <address><email>LMM@acm.org</email></address>
3182    </author>
3183    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3184      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3185      <address><email>paulle@microsoft.com</email></address>
3186    </author>
3187    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3188      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3189      <address><email>timbl@w3.org</email></address>
3190    </author>
3191    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3192      <organization abbrev="W3C">World Wide Web Consortium</organization>
3193      <address><email>ylafon@w3.org</email></address>
3194    </author>
3195    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
3196      <address><email>mnot@mnot.net</email></address>
3197    </author>
3198    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3199      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3200      <address><email>julian.reschke@greenbytes.de</email></address>
3201    </author>
3202    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3203  </front>
3204  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
3205  <x:source href="p6-cache.xml" basename="p6-cache"/>
3206</reference>
3207
3208<reference anchor="Part7">
3209  <front>
3210    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
3211    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3212      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3213      <address><email>fielding@gbiv.com</email></address>
3214    </author>
3215    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3216      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3217      <address><email>jg@freedesktop.org</email></address>
3218    </author>
3219    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3220      <organization abbrev="HP">Hewlett-Packard Company</organization>
3221      <address><email>JeffMogul@acm.org</email></address>
3222    </author>
3223    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3224      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3225      <address><email>henrikn@microsoft.com</email></address>
3226    </author>
3227    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3228      <organization abbrev="Adobe">Adobe Systems Incorporated</organization>
3229      <address><email>LMM@acm.org</email></address>
3230    </author>
3231    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3232      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3233      <address><email>paulle@microsoft.com</email></address>
3234    </author>
3235    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3236      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3237      <address><email>timbl@w3.org</email></address>
3238    </author>
3239    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3240      <organization abbrev="W3C">World Wide Web Consortium</organization>
3241      <address><email>ylafon@w3.org</email></address>
3242    </author>
3243    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3244      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3245      <address><email>julian.reschke@greenbytes.de</email></address>
3246    </author>
3247    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3248  </front>
3249  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3250  <x:source href="p7-auth.xml" basename="p7-auth"/>
3251</reference>
3252
3253<reference anchor="RFC2119">
3254  <front>
3255    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3256    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3257      <organization>Harvard University</organization>
3258      <address><email>sob@harvard.edu</email></address>
3259    </author>
3260    <date month="March" year="1997"/>
3261  </front>
3262  <seriesInfo name="BCP" value="14"/>
3263  <seriesInfo name="RFC" value="2119"/>
3264</reference>
3265
3266<reference anchor="RFC3986">
3267 <front>
3268  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3269  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3270    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3271    <address>
3272       <email>timbl@w3.org</email>
3273       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3274    </address>
3275  </author>
3276  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3277    <organization abbrev="Day Software">Day Software</organization>
3278    <address>
3279      <email>fielding@gbiv.com</email>
3280      <uri>http://roy.gbiv.com/</uri>
3281    </address>
3282  </author>
3283  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3284    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3285    <address>
3286      <email>LMM@acm.org</email>
3287      <uri>http://larry.masinter.net/</uri>
3288    </address>
3289  </author>
3290  <date month='January' year='2005'></date>
3291 </front>
3292 <seriesInfo name="STD" value="66"/>
3293 <seriesInfo name="RFC" value="3986"/>
3294</reference>
3295
3296<reference anchor="RFC5234">
3297  <front>
3298    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3299    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3300      <organization>Brandenburg InternetWorking</organization>
3301      <address>
3302        <email>dcrocker@bbiw.net</email>
3303      </address> 
3304    </author>
3305    <author initials="P." surname="Overell" fullname="Paul Overell">
3306      <organization>THUS plc.</organization>
3307      <address>
3308        <email>paul.overell@thus.net</email>
3309      </address>
3310    </author>
3311    <date month="January" year="2008"/>
3312  </front>
3313  <seriesInfo name="STD" value="68"/>
3314  <seriesInfo name="RFC" value="5234"/>
3315</reference>
3316
3317</references>
3318
3319<references title="Informative References">
3320
3321<reference anchor="RFC1945">
3322  <front>
3323    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3324    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3325      <organization>MIT, Laboratory for Computer Science</organization>
3326      <address><email>timbl@w3.org</email></address>
3327    </author>
3328    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3329      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3330      <address><email>fielding@ics.uci.edu</email></address>
3331    </author>
3332    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3333      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3334      <address><email>frystyk@w3.org</email></address>
3335    </author>
3336    <date month="May" year="1996"/>
3337  </front>
3338  <seriesInfo name="RFC" value="1945"/>
3339</reference>
3340
3341<reference anchor="RFC2068">
3342  <front>
3343    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3344    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3345      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3346      <address><email>fielding@ics.uci.edu</email></address>
3347    </author>
3348    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3349      <organization>MIT Laboratory for Computer Science</organization>
3350      <address><email>jg@w3.org</email></address>
3351    </author>
3352    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3353      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3354      <address><email>mogul@wrl.dec.com</email></address>
3355    </author>
3356    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3357      <organization>MIT Laboratory for Computer Science</organization>
3358      <address><email>frystyk@w3.org</email></address>
3359    </author>
3360    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3361      <organization>MIT Laboratory for Computer Science</organization>
3362      <address><email>timbl@w3.org</email></address>
3363    </author>
3364    <date month="January" year="1997"/>
3365  </front>
3366  <seriesInfo name="RFC" value="2068"/>
3367</reference>
3368
3369<reference anchor="RFC2616">
3370  <front>
3371    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3372    <author initials="R." surname="Fielding" fullname="R. Fielding">
3373      <organization>University of California, Irvine</organization>
3374      <address><email>fielding@ics.uci.edu</email></address>
3375    </author>
3376    <author initials="J." surname="Gettys" fullname="J. Gettys">
3377      <organization>W3C</organization>
3378      <address><email>jg@w3.org</email></address>
3379    </author>
3380    <author initials="J." surname="Mogul" fullname="J. Mogul">
3381      <organization>Compaq Computer Corporation</organization>
3382      <address><email>mogul@wrl.dec.com</email></address>
3383    </author>
3384    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3385      <organization>MIT Laboratory for Computer Science</organization>
3386      <address><email>frystyk@w3.org</email></address>
3387    </author>
3388    <author initials="L." surname="Masinter" fullname="L. Masinter">
3389      <organization>Xerox Corporation</organization>
3390      <address><email>masinter@parc.xerox.com</email></address>
3391    </author>
3392    <author initials="P." surname="Leach" fullname="P. Leach">
3393      <organization>Microsoft Corporation</organization>
3394      <address><email>paulle@microsoft.com</email></address>
3395    </author>
3396    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3397      <organization>W3C</organization>
3398      <address><email>timbl@w3.org</email></address>
3399    </author>
3400    <date month="June" year="1999"/>
3401  </front>
3402  <seriesInfo name="RFC" value="2616"/>
3403</reference>
3404
3405<reference anchor='RFC2817'>
3406  <front>
3407    <title>Upgrading to TLS Within HTTP/1.1</title>
3408    <author initials='R.' surname='Khare' fullname='R. Khare'>
3409      <organization>4K Associates / UC Irvine</organization>
3410      <address><email>rohit@4K-associates.com</email></address>
3411    </author>
3412    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3413      <organization>Agranat Systems, Inc.</organization>
3414      <address><email>lawrence@agranat.com</email></address>
3415    </author>
3416    <date year='2000' month='May' />
3417  </front>
3418  <seriesInfo name='RFC' value='2817' />
3419</reference>
3420
3421<reference anchor='RFC3864'>
3422  <front>
3423    <title>Registration Procedures for Message Header Fields</title>
3424    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3425      <organization>Nine by Nine</organization>
3426      <address><email>GK-IETF@ninebynine.org</email></address>
3427    </author>
3428    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3429      <organization>BEA Systems</organization>
3430      <address><email>mnot@pobox.com</email></address>
3431    </author>
3432    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3433      <organization>HP Labs</organization>
3434      <address><email>JeffMogul@acm.org</email></address>
3435    </author>
3436    <date year='2004' month='September' />
3437  </front>
3438  <seriesInfo name='BCP' value='90' />
3439  <seriesInfo name='RFC' value='3864' />
3440</reference>
3441
3442<reference anchor='RFC5226'>
3443  <front>
3444    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3445    <author initials='T.' surname='Narten' fullname='T. Narten'>
3446      <organization>IBM</organization>
3447      <address><email>narten@us.ibm.com</email></address>
3448    </author>
3449    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3450      <organization>Google</organization>
3451      <address><email>Harald@Alvestrand.no</email></address>
3452    </author>
3453    <date year='2008' month='May' />
3454  </front>
3455  <seriesInfo name='BCP' value='26' />
3456  <seriesInfo name='RFC' value='5226' />
3457</reference>
3458
3459<reference anchor="RFC5322">
3460  <front>
3461    <title>Internet Message Format</title>
3462    <author initials="P." surname="Resnick" fullname="P. Resnick">
3463      <organization>Qualcomm Incorporated</organization>
3464    </author>
3465    <date year="2008" month="October"/>
3466  </front> 
3467  <seriesInfo name="RFC" value="5322"/>
3468</reference>
3469
3470</references>
3471
3472<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3473<t>
3474  This document takes over the Status Code Registry, previously defined
3475  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3476  (<xref target="status.code.registry"/>)
3477</t>
3478<t>
3479  Clarify definition of POST.
3480  (<xref target="POST"/>)
3481</t>
3482<t>
3483  Take over definition of CONNECT method from <xref target="RFC2817"/>.
3484  (<xref target="CONNECT"/>)
3485</t>
3486<t>
3487  Failed to consider that there are
3488  many other request methods that are safe to automatically redirect,
3489  and further that the user agent is able to make that determination
3490  based on the request method semantics.
3491  (Sections <xref format="counter" target="status.301"/>,
3492  <xref format="counter" target="status.302"/> and
3493  <xref format="counter" target="status.307"/>)
3494</t>
3495<t>
3496  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3497  It used to indicate that the target resource must be accessed through the
3498  proxy given by the Location field. The Location field gave the URI of the
3499  proxy. The recipient was expected to repeat this single request via the proxy.
3500  (<xref target="status.305"/>)
3501</t>
3502<t>
3503  Define status 426 (Upgrade Required) (this was incorporated from
3504  <xref target="RFC2817"/>).
3505  (<xref target="status.426"/>)
3506</t>
3507<t>
3508  Reclassify "Allow" as response header field, removing the option to
3509  specify it in a PUT request.
3510  Relax the server requirement on the contents of the Allow header field and
3511  remove requirement on clients to always trust the header field value.
3512  (<xref target="header.allow"/>)
3513</t>
3514<t>
3515  Correct syntax of Location header field to allow URI references (including
3516  relative references and fragments), as referred symbol "absoluteURI" wasn't
3517  what was expected, and add some clarifications as to when use of fragments
3518  would not be appropriate.
3519  (<xref target="header.location"/>)
3520</t>
3521<t>
3522  Restrict Max-Forwards header field to OPTIONS and TRACE (previously,
3523  extension methods could have used it as well).
3524  (<xref target="header.max-forwards"/>)
3525</t>
3526<t>
3527  Allow Referer field value of "about:blank" as alternative to not specifying it.
3528  (<xref target="header.referer"/>)
3529</t>
3530<t>
3531  In the description of the Server header field, the Via field
3532  was described as a SHOULD. The requirement was and is stated
3533  correctly in the description of the Via header field in &header-via;.
3534  (<xref target="header.server"/>)
3535</t>
3536</section>
3537
3538<?BEGININC p2-semantics.abnf-appendix ?>
3539<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3540<figure>
3541<artwork type="abnf" name="p2-semantics.parsed-abnf">
3542<x:ref>Accept</x:ref> = &lt;Accept, defined in [Part3], Section 6.1&gt;
3543<x:ref>Accept-Charset</x:ref> = &lt;Accept-Charset, defined in [Part3], Section 6.2&gt;
3544<x:ref>Accept-Encoding</x:ref> = &lt;Accept-Encoding, defined in [Part3], Section 6.3&gt;
3545<x:ref>Accept-Language</x:ref> = &lt;Accept-Language, defined in [Part3], Section 6.4&gt;
3546<x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in [Part5], Section 5.1&gt;
3547<x:ref>Age</x:ref> = &lt;Age, defined in [Part6], Section 3.1&gt;
3548<x:ref>Allow</x:ref> = "Allow:" OWS Allow-v
3549<x:ref>Allow-v</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3550<x:ref>Authorization</x:ref> = &lt;Authorization, defined in [Part7], Section 4.1&gt;
3551
3552<x:ref>ETag</x:ref> = &lt;ETag, defined in [Part4], Section 6.1&gt;
3553<x:ref>Expect</x:ref> = "Expect:" OWS Expect-v
3554<x:ref>Expect-v</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3555
3556<x:ref>From</x:ref> = "From:" OWS From-v
3557<x:ref>From-v</x:ref> = mailbox
3558
3559<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 6.1&gt;
3560<x:ref>Host</x:ref> = &lt;Host, defined in [Part1], Section 2.6&gt;
3561
3562<x:ref>If-Match</x:ref> = &lt;If-Match, defined in [Part4], Section 6.2&gt;
3563If-Modified-Since =
3564 &lt;If-Modified-Since, defined in [Part4], Section 6.3&gt;
3565<x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in [Part4], Section 6.4&gt;
3566<x:ref>If-Range</x:ref> = &lt;If-Range, defined in [Part5], Section 5.3&gt;
3567If-Unmodified-Since =
3568 &lt;If-Unmodified-Since, defined in [Part4], Section 6.5&gt;
3569
3570<x:ref>Location</x:ref> = "Location:" OWS Location-v
3571<x:ref>Location-v</x:ref> = URI-reference
3572
3573<x:ref>Max-Forwards</x:ref> = "Max-Forwards:" OWS Max-Forwards-v
3574<x:ref>Max-Forwards-v</x:ref> = 1*DIGIT
3575<x:ref>Method</x:ref> = token
3576
3577<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
3578
3579Proxy-Authenticate =
3580 &lt;Proxy-Authenticate, defined in [Part7], Section 4.2&gt;
3581Proxy-Authorization =
3582 &lt;Proxy-Authorization, defined in [Part7], Section 4.3&gt;
3583
3584<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3585<x:ref>Range</x:ref> = &lt;Range, defined in [Part5], Section 5.4&gt;
3586<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
3587<x:ref>Referer</x:ref> = "Referer:" OWS Referer-v
3588<x:ref>Referer-v</x:ref> = absolute-URI / partial-URI
3589<x:ref>Retry-After</x:ref> = "Retry-After:" OWS Retry-After-v
3590<x:ref>Retry-After-v</x:ref> = HTTP-date / delta-seconds
3591
3592<x:ref>Server</x:ref> = "Server:" OWS Server-v
3593<x:ref>Server-v</x:ref> = product *( RWS ( product / comment ) )
3594<x:ref>Status-Code</x:ref> = 3DIGIT
3595
3596<x:ref>TE</x:ref> = &lt;TE, defined in [Part1], Section 9.5&gt;
3597
3598<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.6&gt;
3599<x:ref>User-Agent</x:ref> = "User-Agent:" OWS User-Agent-v
3600<x:ref>User-Agent-v</x:ref> = product *( RWS ( product / comment ) )
3601
3602<x:ref>Vary</x:ref> = &lt;Vary, defined in [Part6], Section 3.5&gt;
3603
3604WWW-Authenticate =
3605 &lt;WWW-Authenticate, defined in [Part7], Section 4.4&gt;
3606
3607<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.6&gt;
3608
3609<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2&gt;
3610
3611<x:ref>delta-seconds</x:ref> = 1*DIGIT
3612
3613<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
3614<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
3615<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
3616 *expect-params ]
3617
3618<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
3619
3620<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
3621
3622<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.6&gt;
3623<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 6.3&gt;
3624
3625<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
3626
3627<x:ref>request-header</x:ref> = Accept / Accept-Charset / Accept-Encoding /
3628 Accept-Language / Authorization / Expect / From / Host / If-Match /
3629 If-Modified-Since / If-None-Match / If-Range / If-Unmodified-Since /
3630 Max-Forwards / Proxy-Authorization / Range / Referer / TE /
3631 User-Agent
3632<x:ref>response-header</x:ref> = Accept-Ranges / Age / Allow / ETag / Location /
3633 Proxy-Authenticate / Retry-After / Server / Vary / WWW-Authenticate
3634
3635<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
3636</artwork>
3637</figure>
3638<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
3639; Reason-Phrase defined but not used
3640; Status-Code defined but not used
3641; request-header defined but not used
3642; response-header defined but not used
3643</artwork></figure></section>
3644<?ENDINC p2-semantics.abnf-appendix ?>
3645
3646<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3647
3648<section title="Since RFC 2616">
3649<t>
3650  Extracted relevant partitions from <xref target="RFC2616"/>.
3651</t>
3652</section>
3653
3654<section title="Since draft-ietf-httpbis-p2-semantics-00">
3655<t>
3656  Closed issues:
3657  <list style="symbols"> 
3658    <t>
3659      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3660      "Via is a MUST"
3661      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3662    </t>
3663    <t>
3664      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3665      "Fragments allowed in Location"
3666      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3667    </t>
3668    <t>
3669      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3670      "Safe Methods vs Redirection"
3671      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3672    </t>
3673    <t>
3674      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3675      "Revise description of the POST method"
3676      (<eref target="http://purl.org/NET/http-errata#post"/>)
3677    </t>
3678    <t>
3679      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3680      "Normative and Informative references"
3681    </t>
3682    <t>
3683      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3684      "RFC2606 Compliance"
3685    </t>
3686    <t>
3687      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3688      "Informative references"
3689    </t>
3690    <t>
3691      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3692      "Redundant cross-references"
3693    </t>
3694  </list>
3695</t>
3696<t>
3697  Other changes:
3698  <list style="symbols"> 
3699    <t>
3700      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3701    </t>
3702  </list>
3703</t>
3704</section>
3705
3706<section title="Since draft-ietf-httpbis-p2-semantics-01">
3707<t>
3708  Closed issues:
3709  <list style="symbols"> 
3710    <t>
3711      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3712      "PUT side effects"
3713    </t>
3714    <t>
3715      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3716      "Duplicate Host header requirements"
3717    </t>
3718  </list>
3719</t>
3720<t>
3721  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3722  <list style="symbols"> 
3723    <t>
3724      Move "Product Tokens" section (back) into Part 1, as "token" is used
3725      in the definition of the Upgrade header field.
3726    </t>
3727    <t>
3728      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3729    </t>
3730    <t>
3731      Copy definition of delta-seconds from Part6 instead of referencing it.
3732    </t>
3733  </list>
3734</t>
3735</section>
3736
3737<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3738<t>
3739  Closed issues:
3740  <list style="symbols"> 
3741    <t>
3742      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3743      "Requiring Allow in 405 responses"
3744    </t>
3745    <t>
3746      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3747      "Status Code Registry"
3748    </t>
3749    <t>
3750      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3751      "Redirection vs. Location"
3752    </t>
3753    <t>
3754      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3755      "Cacheability of 303 response"
3756    </t>
3757    <t>
3758      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3759      "305 Use Proxy"
3760    </t>
3761    <t>
3762      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3763      "Classification for Allow header"
3764    </t>
3765    <t>
3766      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3767      "PUT - 'store under' vs 'store at'"
3768    </t>
3769  </list>
3770</t>
3771<t>
3772  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3773  <list style="symbols"> 
3774    <t>
3775      Reference RFC 3984, and update header field registrations for headers defined
3776      in this document.
3777    </t>
3778  </list>
3779</t>
3780<t>
3781  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3782  <list style="symbols"> 
3783    <t>
3784      Replace string literals when the string really is case-sensitive (method).
3785    </t>
3786  </list>
3787</t>
3788</section>
3789
3790<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3791<t>
3792  Closed issues:
3793  <list style="symbols"> 
3794    <t>
3795      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
3796      "OPTIONS request bodies"
3797    </t>
3798    <t>
3799      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
3800      "Description of CONNECT should refer to RFC2817"
3801    </t>
3802    <t>
3803      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
3804      "Location Content-Location reference request/response mixup"
3805    </t>
3806  </list>
3807</t>
3808<t>
3809  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
3810  <list style="symbols"> 
3811    <t>
3812      Added initial proposal for registration process, plus initial
3813      content (non-HTTP/1.1 methods to be added by a separate specification).
3814    </t>
3815  </list>
3816</t>
3817</section>
3818
3819<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3820<t>
3821  Closed issues:
3822  <list style="symbols"> 
3823    <t>
3824      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3825      "Content-*"
3826    </t>
3827    <t>
3828      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3829      "RFC 2822 is updated by RFC 5322"
3830    </t>
3831  </list>
3832</t>
3833<t>
3834  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3835  <list style="symbols"> 
3836    <t>
3837      Use "/" instead of "|" for alternatives.
3838    </t>
3839    <t>
3840      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3841      whitespace ("OWS") and required whitespace ("RWS").
3842    </t>
3843    <t>
3844      Rewrite ABNFs to spell out whitespace rules, factor out
3845      header field value format definitions.
3846    </t>
3847  </list>
3848</t>
3849</section>
3850
3851<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3852<t>
3853  Closed issues:
3854  <list style="symbols"> 
3855    <t>
3856      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
3857      "Reason-Phrase BNF"
3858    </t>
3859  </list>
3860</t>
3861<t>
3862  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3863  <list style="symbols"> 
3864    <t>
3865      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3866    </t>
3867  </list>
3868</t>
3869</section>
3870
3871<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
3872<t>
3873  Closed issues:
3874  <list style="symbols"> 
3875    <t>
3876      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
3877      "Clarify when Referer is sent"
3878    </t>
3879    <t>
3880      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
3881      "status codes vs methods"
3882    </t>
3883    <t>
3884      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
3885      "Do not require "updates" relation for specs that register status codes or method names"
3886    </t>
3887  </list>
3888</t>
3889</section>
3890
3891<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
3892<t>
3893  Closed issues:
3894  <list style="symbols"> 
3895    <t>
3896      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
3897      "Idempotency"
3898    </t>
3899    <t>
3900      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
3901      "TRACE security considerations"
3902    </t>
3903    <t>
3904      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
3905      "Clarify rules for determining what entities a response carries"
3906    </t>
3907    <t>
3908      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
3909      "update note citing RFC 1945 and 2068"
3910    </t>
3911    <t>
3912      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
3913      "update note about redirect limit"
3914    </t>
3915    <t>
3916      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
3917      "Location header ABNF should use 'URI'"
3918    </t>
3919    <t>
3920      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
3921      "fragments in Location vs status 303"
3922    </t>
3923    <t>
3924      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
3925      "move IANA registrations for optional status codes"
3926    </t>
3927  </list>
3928</t>
3929<t>
3930  Partly resolved issues:
3931  <list style="symbols"> 
3932    <t>
3933      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
3934      "Are OPTIONS and TRACE safe?"
3935    </t>
3936  </list>
3937</t>
3938</section>
3939
3940<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
3941<t>
3942  Closed issues:
3943  <list style="symbols"> 
3944    <t>
3945      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3946      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
3947      status codes when fixing this previously)
3948    </t>
3949  </list>
3950</t>
3951</section>
3952
3953<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
3954<t>
3955  Closed issues:
3956  <list style="symbols"> 
3957    <t>
3958      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
3959      "Fragment combination / precedence during redirects"
3960    </t>
3961  </list>
3962</t>
3963<t>
3964  Partly resolved issues:
3965  <list style="symbols"> 
3966    <t>
3967      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
3968      "Location header payload handling"
3969    </t>
3970    <t>
3971      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
3972      "Term for the requested resource's URI"
3973    </t>
3974  </list>
3975</t>
3976</section>
3977
3978<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
3979<t>
3980  Closed issues:
3981  <list style="symbols"> 
3982    <t>
3983      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
3984      "Clarify 'Requested Variant'"
3985    </t>
3986    <t>
3987      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
3988      "Clarify entity / representation / variant terminology"
3989    </t>
3990    <t>
3991      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/139"/>:
3992      "Methods and Caching"
3993    </t>
3994    <t>
3995      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/190"/>:
3996      "OPTIONS vs Max-Forwards"
3997    </t>
3998    <t>
3999      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/199"/>:
4000      "Status codes and caching"
4001    </t>
4002    <t>
4003      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
4004      "consider removing the 'changes from 2068' sections"
4005    </t>
4006  </list>
4007</t>
4008</section>
4009
4010<section title="Since draft-ietf-httpbis-p2-semantics-11" anchor="changes.since.11">
4011<t>
4012  Closed issues:
4013  <list style="symbols"> 
4014    <t>
4015      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/229"/>:
4016      "Considerations for new status codes"
4017    </t>
4018    <t>
4019      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/230"/>:
4020      "Considerations for new methods"
4021    </t>
4022    <t>
4023      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/232"/>:
4024      "User-Agent guidelines" (relating to the 'User-Agent' header field)
4025    </t>
4026  </list>
4027</t>
4028</section>
4029
4030<section title="Since draft-ietf-httpbis-p2-semantics-12" anchor="changes.since.12">
4031<t>
4032  Closed issues:
4033  <list style="symbols"> 
4034    <t>
4035      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4036      "Fragment combination / precedence during redirects" (added warning
4037      about having a fragid on the redirect may cause inconvenience in
4038      some cases)
4039    </t>
4040    <t>
4041      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/88"/>:
4042      "205 Bodies"
4043    </t>
4044    <t>
4045      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/203"/>:
4046      "Max-Forwards vs extension methods"
4047    </t>
4048    <t>
4049      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/137"/>:
4050      "duplicate ABNF for Reason-Phrase"
4051    </t>
4052    <t>
4053      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/226"/>:
4054      "proxies not supporting certain methods"
4055    </t>
4056    <t>
4057      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/239"/>:
4058      "Migrate CONNECT from RFC2817 to p2"
4059    </t>
4060    <t>
4061      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/240"/>:
4062      "Migrate Upgrade details from RFC2817"
4063    </t>
4064    <t>
4065      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/225"/>:
4066      "PUT side effect: invalidation or just stale?"
4067    </t>
4068    <t>
4069      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/275"/>:
4070      "duplicate ABNF for 'Method'"
4071    </t>
4072  </list>
4073</t>
4074</section>
4075
4076</section>
4077
4078</back>
4079</rfc>
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