source: draft-ietf-httpbis/latest/p2-semantics.xml @ 1097

Last change on this file since 1097 was 1097, checked in by julian.reschke@…, 9 years ago

Add additional warning on fragids on redirects potentially causing inconvenience (as requested by the TAG) (see #43)

  • Property svn:eol-style set to native
File size: 169.9 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 "December">
16  <!ENTITY ID-YEAR "2010">
17  <!ENTITY notation                   "<xref target='Part1' x:rel='#notation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
18  <!ENTITY messaging                  "<xref target='Part1' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
19  <!ENTITY payload                    "<xref target='Part3' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
20  <!ENTITY conditional                "<xref target='Part4' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
21  <!ENTITY range                      "<xref target='Part5' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
22  <!ENTITY caching                    "<xref target='Part6' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
23  <!ENTITY auth                       "<xref target='Part7' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
24  <!ENTITY combining-responses        "<xref target='Part6' x:rel='#combining.responses' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
25  <!ENTITY content-negotiation        "<xref target='Part3' x:rel='#content.negotiation' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
26  <!ENTITY notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
27  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
28  <!ENTITY uri                        "<xref target='Part1' x:rel='#uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
29  <!ENTITY effective-request-uri      "<xref target='Part1' x:rel='#effective.request.uri' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
30  <!ENTITY full-date                  "<xref target='Part1' x:rel='#date.time.formats.full.date' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
31  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
32  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
33  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
34  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
35  <!ENTITY request-target             "<xref target='Part1' x:rel='#request-target' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
42  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
43  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
44  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
45  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
46  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
47  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
48  <!ENTITY header-fields              "<xref target='Part1' x:rel='#header.fields' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
49  <!ENTITY header-host                "<xref target='Part1' x:rel='#header.host' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
50  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
51  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
52  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
53  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
54  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
55  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
56  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
57  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
58  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
59  <!ENTITY header-upgrade             "<xref target='Part1' x:rel='#header.upgrade' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
60  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.te' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
61  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
62  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
63  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
64  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
65  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
66  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
67  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='#internet.media.type.message.http' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
68  <!ENTITY status-206                 "<xref target='Part5' x:rel='#status.206' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
69  <!ENTITY status-304                 "<xref target='Part4' x:rel='#status.304' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
70  <!ENTITY status-401                 "<xref target='Part7' x:rel='#status.401' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
71  <!ENTITY status-407                 "<xref target='Part7' x:rel='#status.407' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
72  <!ENTITY status-412                 "<xref target='Part4' x:rel='#status.412' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
73  <!ENTITY status-416                 "<xref target='Part5' x:rel='#status.416' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
74  <!ENTITY p4-status-codes            "<xref target='Part4' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
75  <!ENTITY p5-status-codes            "<xref target='Part5' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
76  <!ENTITY p7-status-codes            "<xref target='Part7' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
77  <!ENTITY p6-heuristic               "<xref target='Part6' x:rel='#heuristic.freshness' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
78  <!ENTITY p6-explicit               "<xref target='Part6' x:rel='#calculating.freshness.lifetime' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
79]>
80<?rfc toc="yes" ?>
81<?rfc symrefs="yes" ?>
82<?rfc sortrefs="yes" ?>
83<?rfc compact="yes"?>
84<?rfc subcompact="no" ?>
85<?rfc linkmailto="no" ?>
86<?rfc editing="no" ?>
87<?rfc comments="yes"?>
88<?rfc inline="yes"?>
89<?rfc rfcedstyle="yes"?>
90<?rfc-ext allow-markup-in-artwork="yes" ?>
91<?rfc-ext include-references-in-index="yes" ?>
92<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
93     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
94     xmlns:x='http://purl.org/net/xml2rfc/ext'
95     xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
96<front>
97
98  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
99
100  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
101    <organization abbrev="Day Software">Day Software</organization>
102    <address>
103      <postal>
104        <street>23 Corporate Plaza DR, Suite 280</street>
105        <city>Newport Beach</city>
106        <region>CA</region>
107        <code>92660</code>
108        <country>USA</country>
109      </postal>
110      <phone>+1-949-706-5300</phone>
111      <facsimile>+1-949-706-5305</facsimile>
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 Systems">Adobe Systems, Incorporated</organization>
163    <address>
164      <postal>
165        <street>345 Park Ave</street>
166        <city>San Jose</city>
167        <region>CA</region>
168        <code>95110</code>
169        <country>USA</country>
170      </postal>
171      <email>LMM@acm.org</email>
172      <uri>http://larry.masinter.net/</uri>
173    </address>
174  </author>
175 
176  <author initials="P." surname="Leach" fullname="Paul J. Leach">
177    <organization abbrev="Microsoft">Microsoft Corporation</organization>
178    <address>
179      <postal>
180        <street>1 Microsoft Way</street>
181        <city>Redmond</city>
182        <region>WA</region>
183        <code>98052</code>
184      </postal>
185      <email>paulle@microsoft.com</email>
186    </address>
187  </author>
188   
189  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
190    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
191    <address>
192      <postal>
193        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
194        <street>The Stata Center, Building 32</street>
195        <street>32 Vassar Street</street>
196        <city>Cambridge</city>
197        <region>MA</region>
198        <code>02139</code>
199        <country>USA</country>
200      </postal>
201      <email>timbl@w3.org</email>
202      <uri>http://www.w3.org/People/Berners-Lee/</uri>
203    </address>
204  </author>
205
206  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
207    <organization abbrev="W3C">World Wide Web Consortium</organization>
208    <address>
209      <postal>
210        <street>W3C / ERCIM</street>
211        <street>2004, rte des Lucioles</street>
212        <city>Sophia-Antipolis</city>
213        <region>AM</region>
214        <code>06902</code>
215        <country>France</country>
216      </postal>
217      <email>ylafon@w3.org</email>
218      <uri>http://www.raubacapeu.net/people/yves/</uri>
219    </address>
220  </author>
221
222  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
223    <organization abbrev="greenbytes">greenbytes GmbH</organization>
224    <address>
225      <postal>
226        <street>Hafenweg 16</street>
227        <city>Muenster</city><region>NW</region><code>48155</code>
228        <country>Germany</country>
229      </postal>
230      <phone>+49 251 2807760</phone>
231      <facsimile>+49 251 2807761</facsimile>
232      <email>julian.reschke@greenbytes.de</email>
233      <uri>http://greenbytes.de/tech/webdav/</uri>
234    </address>
235  </author>
236
237  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
238  <workgroup>HTTPbis Working Group</workgroup>
239
240<abstract>
241<t>
242   The Hypertext Transfer Protocol (HTTP) is an application-level
243   protocol for distributed, collaborative, hypermedia information
244   systems. HTTP has been in use by the World Wide Web global information
245   initiative since 1990. This document is Part 2 of the seven-part specification
246   that defines the protocol referred to as "HTTP/1.1" and, taken together,
247   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
248   as expressed by request methods, request-header fields, response status codes,
249   and response-header fields.
250</t>
251</abstract>
252
253<note title="Editorial Note (To be removed by RFC Editor)">
254  <t>
255    Discussion of this draft should take place on the HTTPBIS working group
256    mailing list (ietf-http-wg@w3.org). The current issues list is
257    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/>
258    and related documents (including fancy diffs) can be found at
259    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
260  </t>
261  <t>
262    The changes in this draft are summarized in <xref target="changes.since.12"/>.
263  </t>
264</note>
265</front>
266<middle>
267<section title="Introduction" anchor="introduction">
268<t>
269   This document defines HTTP/1.1 request and response semantics.  Each HTTP
270   message, as defined in &messaging;, is in the form of either a request or
271   a response.  An HTTP server listens on a connection for HTTP requests and
272   responds to each request, in the order received on that connection, with
273   one or more HTTP response messages.  This document defines the commonly
274   agreed upon semantics of the HTTP uniform interface, the intentions defined
275   by each request method, and the various response messages that might be
276   expected as a result of applying that method to the target resource.
277</t>
278<t>
279   This document is currently disorganized in order to minimize the changes
280   between drafts and enable reviewers to see the smaller errata changes.
281   A future draft will reorganize the sections to better reflect the content.
282   In particular, the sections will be ordered according to the typical
283   processing of an HTTP request message (after message parsing): resource
284   mapping, general header fields, methods, request modifiers, response
285   status, and resource metadata.  The current mess reflects how widely
286   dispersed these topics and associated requirements had become in
287   <xref target="RFC2616"/>.
288</t>
289
290<section title="Requirements" anchor="intro.requirements">
291<t>
292   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
293   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
294   document are to be interpreted as described in <xref target="RFC2119"/>.
295</t>
296<t>
297   An implementation is not compliant if it fails to satisfy one or more
298   of the "MUST" or "REQUIRED" level requirements for the protocols it
299   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
300   level and all the "SHOULD" level requirements for its protocols is said
301   to be "unconditionally compliant"; one that satisfies all the "MUST"
302   level requirements but not all the "SHOULD" level requirements for its
303   protocols is said to be "conditionally compliant".
304</t>
305</section>
306
307<section title="Syntax Notation" anchor="notation">
308  <x:anchor-alias value="CR"/>
309  <x:anchor-alias value="DIGIT"/>
310  <x:anchor-alias value="LF"/>
311  <x:anchor-alias value="VCHAR"/>
312  <x:anchor-alias value="WSP"/>
313<t>
314  This specification uses the ABNF syntax defined in &notation; (which
315  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
316  <xref target="collected.abnf"/> shows the collected ABNF, with the list
317  rule expanded.
318</t>
319<t>
320  The following core rules are included by
321  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
322  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
323  DIGIT (decimal 0-9), DQUOTE (double quote),
324  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
325  OCTET (any 8-bit sequence of data), SP (space),
326  VCHAR (any visible USASCII character),
327  and WSP (whitespace).
328</t>
329
330<section title="Core Rules" anchor="core.rules">
331  <x:anchor-alias value="obs-text"/>
332  <x:anchor-alias value="quoted-string"/>
333  <x:anchor-alias value="token"/>
334  <x:anchor-alias value="OWS"/>
335  <x:anchor-alias value="RWS"/>
336<t>
337  The core rules below are defined in &basic-rules;:
338</t>
339<figure><artwork type="abnf2616">
340  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
341  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
342  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
343  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
344  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
345</artwork></figure>
346</section>
347
348<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
349  <x:anchor-alias value="absolute-URI"/>
350  <x:anchor-alias value="Accept"/>
351  <x:anchor-alias value="Accept-Charset"/>
352  <x:anchor-alias value="Accept-Encoding"/>
353  <x:anchor-alias value="Accept-Language"/>
354  <x:anchor-alias value="Accept-Ranges"/>
355  <x:anchor-alias value="Age"/>
356  <x:anchor-alias value="Authorization"/>
357  <x:anchor-alias value="comment"/>
358  <x:anchor-alias value="ETag"/>
359  <x:anchor-alias value="Host"/>
360  <x:anchor-alias value="HTTP-date"/>
361  <x:anchor-alias value="If-Match"/>
362  <x:anchor-alias value="If-Modified-Since"/>
363  <x:anchor-alias value="If-None-Match"/>
364  <x:anchor-alias value="If-Range"/>
365  <x:anchor-alias value="If-Unmodified-Since"/>
366  <x:anchor-alias value="partial-URI"/>
367  <x:anchor-alias value="product"/>
368  <x:anchor-alias value="Proxy-Authenticate"/>
369  <x:anchor-alias value="Proxy-Authorization"/>
370  <x:anchor-alias value="Range"/>
371  <x:anchor-alias value="TE"/>
372  <x:anchor-alias value="URI-reference"/>
373  <x:anchor-alias value="Vary"/>
374  <x:anchor-alias value="WWW-Authenticate"/>
375<t>
376  The ABNF rules below are defined in other parts:
377</t>
378<figure><!--Part1--><artwork type="abnf2616">
379  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
380  <x:ref>comment</x:ref>       = &lt;comment, defined in &header-fields;&gt;
381  <x:ref>Host</x:ref>          = &lt;Host, defined in &uri;&gt;
382  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
383  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
384  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
385  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
386  <x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in &uri;&gt;
387</artwork></figure>
388<figure><!--Part3--><artwork type="abnf2616">
389  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
390  <x:ref>Accept-Charset</x:ref> =
391             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
392  <x:ref>Accept-Encoding</x:ref> =
393             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
394  <x:ref>Accept-Language</x:ref> =
395             &lt;Accept-Language, defined in &header-accept-language;&gt;
396</artwork></figure>
397<figure><!--Part4--><artwork type="abnf2616">
398  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
399  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
400  <x:ref>If-Modified-Since</x:ref> =
401             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
402  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
403  <x:ref>If-Unmodified-Since</x:ref> =
404             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
405</artwork></figure>
406<figure><!--Part5--><artwork type="abnf2616">
407  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
408  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
409  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
410</artwork></figure>
411<figure><!--Part6--><artwork type="abnf2616">
412  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
413  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
414</artwork><!--Part7--></figure>
415<figure><artwork type="abnf2616">
416  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
417  <x:ref>Proxy-Authenticate</x:ref> =
418             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
419  <x:ref>Proxy-Authorization</x:ref> =
420             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
421  <x:ref>WWW-Authenticate</x:ref> =
422             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
423</artwork></figure>
424</section>
425</section>
426</section>
427
428<section title="Method" anchor="method">
429  <x:anchor-alias value="Method"/>
430  <x:anchor-alias value="extension-method"/>
431<t>
432   The Method token indicates the method to be performed on the target
433   resource (&effective-request-uri;). The method is case-sensitive.
434</t>
435<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
436  <x:ref>Method</x:ref>         = <x:abnf-char-sequence>"OPTIONS"</x:abnf-char-sequence>   ; "OPTIONS", <xref target="OPTIONS"/>
437                 / <x:abnf-char-sequence>"GET"</x:abnf-char-sequence>               ; "GET", <xref target="GET"/>
438                 / <x:abnf-char-sequence>"HEAD"</x:abnf-char-sequence>            ; "HEAD", <xref target="HEAD"/>
439                 / <x:abnf-char-sequence>"POST"</x:abnf-char-sequence>            ; "POST", <xref target="POST"/>
440                 / <x:abnf-char-sequence>"PUT"</x:abnf-char-sequence>               ; "PUT", <xref target="PUT"/>
441                 / <x:abnf-char-sequence>"DELETE"</x:abnf-char-sequence>      ; "DELETE", <xref target="DELETE"/>
442                 / <x:abnf-char-sequence>"TRACE"</x:abnf-char-sequence>         ; "TRACE", <xref target="TRACE"/>
443                 / <x:abnf-char-sequence>"CONNECT"</x:abnf-char-sequence>   ; "CONNECT", <xref target="CONNECT"/>
444                 / <x:ref>extension-method</x:ref>
445  <x:ref>extension-method</x:ref> = <x:ref>token</x:ref>
446</artwork></figure>
447<t>
448   The list of methods allowed by a resource can be specified in an
449   Allow header field (<xref target="header.allow"/>). The status code of the response
450   always notifies the client whether a method is currently allowed on a
451   resource, since the set of allowed methods can change dynamically. An
452   origin server &SHOULD; respond with the status code 405 (Method Not Allowed)
453   if the method is known by the origin server but not allowed for the
454   resource, and 501 (Not Implemented) if the method is
455   unrecognized or not implemented by the origin server. The methods GET
456   and HEAD &MUST; be supported by all general-purpose servers. All other
457   methods are &OPTIONAL;; however, if the above methods are implemented,
458   they &MUST; be implemented with the same semantics as those specified
459   in <xref target="method.definitions"/>.
460</t>
461
462<section title="Method Registry" anchor="method.registry">
463<t>
464  The HTTP Method Registry defines the name space for the Method token in the
465  Request line of an HTTP request.
466</t>
467<t>
468  Registrations &MUST; include the following fields:
469  <list style="symbols">
470    <t>Method Name (see <xref target="method"/>)</t>
471    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
472    <t>Pointer to specification text</t>
473  </list>
474</t>
475<t>
476  Values to be added to this name space are subject to IETF review
477  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
478</t>
479<t>
480  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
481</t>
482
483<section title="Considerations for New Methods" anchor="considerations.for.new.methods">
484<t>
485   When it is necessary to express new semantics for a HTTP request that
486   aren't specific to a single application or media type, and currently defined
487   methods are inadequate, it may be appropriate to register a new method.
488</t>
489<t>
490   HTTP methods are generic; that is, they are potentially applicable to any
491   resource, not just one particular media type, "type" of resource, or
492   application. As such, it is preferred that new HTTP methods be registered
493   in a document that isn't specific to a single application, so that this is
494   clear.
495</t>
496<t>
497   Due to the parsing rules defined in &message-body;, definitions of HTTP
498   methods cannot prohibit the presence of a message-body on either the request
499   or the response message (with responses to HEAD requests being the single
500   exception). Definitions of new methods cannot change this rule, but they can
501   specify that only zero-length bodies (as opposed to absent bodies) are allowed.
502</t>
503<t>
504   New method definitions need to indicate whether they are safe (<xref
505   target="safe.methods"/>) and whether they are idempotent (<xref
506   target="idempotent.methods"/>). They also need to state whether they can be
507   cached (&caching;); in particular what conditions a cache may store the
508   response, and under what conditions such a stored response may be used to
509   satisfy a subsequent request.
510</t>
511</section>
512
513</section>
514</section>
515
516<section title="Request Header Fields" anchor="request.header.fields">
517  <x:anchor-alias value="request-header"/>
518<t>
519   The request-header fields allow the client to pass additional
520   information about the request, and about the client itself, to the
521   server. These fields act as request modifiers, with semantics
522   equivalent to the parameters on a programming language method
523   invocation.
524</t>
525<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
526  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
527                 / <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
528                 / <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
529                 / <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
530                 / <x:ref>Authorization</x:ref>            ; &header-authorization;
531                 / <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
532                 / <x:ref>From</x:ref>                     ; <xref target="header.from"/>
533                 / <x:ref>Host</x:ref>                     ; &header-host;
534                 / <x:ref>If-Match</x:ref>                 ; &header-if-match;
535                 / <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
536                 / <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
537                 / <x:ref>If-Range</x:ref>                 ; &header-if-range;
538                 / <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
539                 / <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
540                 / <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
541                 / <x:ref>Range</x:ref>                    ; &header-range;
542                 / <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
543                 / <x:ref>TE</x:ref>                       ; &header-te;
544                 / <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
545</artwork></figure>
546<t>
547   Request-header field names can be extended reliably only in
548   combination with a change in the protocol version. However, new or
549   experimental header fields &MAY; be given the semantics of request-header
550   fields if all parties in the communication recognize them to
551   be request-header fields.
552</t>
553</section>
554
555<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
556  <x:anchor-alias value="Reason-Phrase"/>
557  <x:anchor-alias value="Status-Code"/>
558  <x:anchor-alias value="extension-code"/>
559<t>
560   The Status-Code element is a 3-digit integer result code of the
561   attempt to understand and satisfy the request. The status codes listed
562   below are defined in <xref target="status.codes"/>, &p4-status-codes;,
563   &p5-status-codes;, and &p7-status-codes;.
564</t>
565<t>
566   The Reason-Phrase is intended to give a short
567   textual description of the Status-Code. The Status-Code is intended
568   for use by automata and the Reason-Phrase is intended for the human
569   user. The client is not required to examine or display the Reason-Phrase.
570</t>
571<t> 
572   The individual values of the numeric status codes defined for
573   HTTP/1.1, and an example set of corresponding Reason-Phrase values, are
574   presented below. The reason phrases listed here are only
575   recommendations -- they &MAY; be replaced by local equivalents without
576   affecting the protocol.
577</t>
578<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"/>
579  <x:ref>Status-Code</x:ref> =
580       "100"  ; <xref target="status.100"/>: Continue
581     / "101"  ; <xref target="status.101"/>: Switching Protocols
582     / "200"  ; <xref target="status.200"/>: OK
583     / "201"  ; <xref target="status.201"/>: Created
584     / "202"  ; <xref target="status.202"/>: Accepted
585     / "203"  ; <xref target="status.203"/>: Non-Authoritative Information
586     / "204"  ; <xref target="status.204"/>: No Content
587     / "205"  ; <xref target="status.205"/>: Reset Content
588     / "206"  ; &status-206;: Partial Content
589     / "300"  ; <xref target="status.300"/>: Multiple Choices
590     / "301"  ; <xref target="status.301"/>: Moved Permanently
591     / "302"  ; <xref target="status.302"/>: Found
592     / "303"  ; <xref target="status.303"/>: See Other
593     / "304"  ; &status-304;: Not Modified
594     / "305"  ; <xref target="status.305"/>: Use Proxy
595     / "307"  ; <xref target="status.307"/>: Temporary Redirect
596     / "400"  ; <xref target="status.400"/>: Bad Request
597     / "401"  ; &status-401;: Unauthorized
598     / "402"  ; <xref target="status.402"/>: Payment Required
599     / "403"  ; <xref target="status.403"/>: Forbidden
600     / "404"  ; <xref target="status.404"/>: Not Found
601     / "405"  ; <xref target="status.405"/>: Method Not Allowed
602     / "406"  ; <xref target="status.406"/>: Not Acceptable
603     / "407"  ; &status-407;: Proxy Authentication Required
604     / "408"  ; <xref target="status.408"/>: Request Time-out
605     / "409"  ; <xref target="status.409"/>: Conflict
606     / "410"  ; <xref target="status.410"/>: Gone
607     / "411"  ; <xref target="status.411"/>: Length Required
608     / "412"  ; &status-412;: Precondition Failed
609     / "413"  ; <xref target="status.413"/>: Request Entity Too Large
610     / "414"  ; <xref target="status.414"/>: URI Too Long
611     / "415"  ; <xref target="status.415"/>: Unsupported Media Type
612     / "416"  ; &status-416;: Requested range not satisfiable
613     / "417"  ; <xref target="status.417"/>: Expectation Failed
614     / "426"  ; <xref target="status.426"/>: Upgrade Required
615     / "500"  ; <xref target="status.500"/>: Internal Server Error
616     / "501"  ; <xref target="status.501"/>: Not Implemented
617     / "502"  ; <xref target="status.502"/>: Bad Gateway
618     / "503"  ; <xref target="status.503"/>: Service Unavailable
619     / "504"  ; <xref target="status.504"/>: Gateway Time-out
620     / "505"  ; <xref target="status.505"/>: HTTP Version not supported
621     / <x:ref>extension-code</x:ref>
622
623  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
624  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
625</artwork></figure>
626<t>
627   HTTP status codes are extensible. HTTP applications are not required
628   to understand the meaning of all registered status codes, though such
629   understanding is obviously desirable. However, applications &MUST;
630   understand the class of any status code, as indicated by the first
631   digit, and treat any unrecognized response as being equivalent to the
632   x00 status code of that class, with the exception that an
633   unrecognized response &MUST-NOT; be cached. For example, if an
634   unrecognized status code of 431 is received by the client, it can
635   safely assume that there was something wrong with its request and
636   treat the response as if it had received a 400 status code. In such
637   cases, user agents &SHOULD; present to the user the representation enclosed
638   with the response, since that representation is likely to include human-readable
639   information which will explain the unusual status.
640</t>
641
642<section title="Status Code Registry" anchor="status.code.registry">
643<t>
644  The HTTP Status Code Registry defines the name space for the Status-Code
645  token in the Status-Line of an HTTP response.
646</t>
647<t>
648  Values to be added to this name space are subject to IETF review
649  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
650</t>
651<t>
652  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
653</t>
654
655<section title="Considerations for New Status Codes" anchor="considerations.for.new.status.codes">
656<t>
657   When it is necessary to express new semantics for a HTTP response that
658   aren't specific to a single application or media type, and currently defined
659   status codes are inadequate, a new status code can be registered.
660</t>
661<t>
662   HTTP status codes are generic; that is, they are potentially applicable to
663   any resource, not just one particular media type, "type" of resource, or
664   application. As such, it is preferred that new HTTP status codes be
665   registered in a document that isn't specific to a single application, so
666   that this is clear.
667</t>
668<t>
669   Definitions of new HTTP status codes typically explain the request
670   conditions that produce a response containing the status code (e.g.,
671   combinations of request headers and/or method(s)), along with any
672   interactions with response headers (e.g., those that are required, those
673   that modify the semantics of the response).
674</t>
675<t>
676   New HTTP status codes are required to fall under one of the categories
677   defined in <xref target="status.codes"/>. To allow existing parsers to
678   properly handle them, new status codes cannot disallow a response body,
679   although they can mandate a zero-length response body. They can require the
680   presence of one or more particular HTTP response header(s).
681</t>
682<t>
683   Likewise, their definitions can specify that caches are allowed to use
684   heuristics to determine their freshness (see &caching;; by default, it is
685   not allowed), and can define how to determine the resource which they
686   carry a representation for (see <xref
687   target="identifying.response.associated.with.representation"/>; by default,
688   it is anonymous).
689</t>
690</section>
691
692</section>
693
694</section>
695
696<section title="Response Header Fields" anchor="response.header.fields">
697  <x:anchor-alias value="response-header"/>
698<t>
699   The response-header fields allow the server to pass additional
700   information about the response which cannot be placed in the Status-Line.
701   These header fields give information about the server and about
702   further access to the target resource (&effective-request-uri;).
703</t>
704<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
705  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
706                  / <x:ref>Age</x:ref>                     ; &header-age;
707                  / <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
708                  / <x:ref>ETag</x:ref>                    ; &header-etag;
709                  / <x:ref>Location</x:ref>                ; <xref target="header.location"/>
710                  / <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
711                  / <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
712                  / <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
713                  / <x:ref>Vary</x:ref>                    ; &header-vary;
714                  / <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
715</artwork></figure>
716<t>
717   Response-header field names can be extended reliably only in
718   combination with a change in the protocol version. However, new or
719   experimental header fields &MAY; be given the semantics of response-header
720   fields if all parties in the communication recognize them to
721   be response-header fields.
722</t>
723</section>
724
725<section title="Representation" anchor="representation">
726<t>
727   Request and Response messages &MAY; transfer a representation if not otherwise
728   restricted by the request method or response status code. A representation
729   consists of metadata (representation header fields) and data (representation
730   body).  When a complete or partial representation is enclosed in an HTTP message,
731   it is referred to as the payload of the message. HTTP representations
732   are defined in &payload;.
733</t>
734<t>
735   A representation body is only present in a message when a message-body is
736   present, as described in &message-body;. The representation body is obtained
737   from the message-body by decoding any Transfer-Encoding that might
738   have been applied to ensure safe and proper transfer of the message.
739</t>
740
741<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
742<t>
743   It is sometimes necessary to determine an identifier for the resource
744   associated with a representation.
745</t>
746<t>
747   An HTTP request representation, when present, is always associated with an
748   anonymous (i.e., unidentified) resource.
749</t>
750<t>
751   In the common case, an HTTP response is a representation of the target
752   resource (see &effective-request-uri;). However, this is not always the
753   case. To determine the URI of the resource a response is associated with,
754   the following rules are used (with the first applicable one being selected):
755</t>
756<t><list style="numbers">
757   <t>If the response status code is 200 or 203 and the request method was GET,
758   the response payload is a representation of the target resource.</t>
759   <t>If the response status code is 204, 206, or 304 and the request method was GET
760   or HEAD, the response payload is a partial representation of the target
761   resource (see &combining-responses;).</t>
762   <t>If the response has a Content-Location header field, and that URI is the same
763   as the effective request URI, the response payload is a representation of the
764   target resource.</t>
765   <t>If the response has a Content-Location header field, and that URI is not the
766   same as the effective request URI, then the response asserts that its
767   payload is a representation of the resource identified by the
768   Content-Location URI. However, such an assertion cannot be trusted unless
769   it can be verified by other means (not defined by HTTP).</t>
770   <t>Otherwise, the response is a representation of an anonymous (i.e.,
771   unidentified) resource.</t>
772</list></t>
773<t>
774  <cref anchor="TODO-req-uri">
775   The comparison function is going to have to be defined somewhere,
776   because we already need to compare URIs for things like cache invalidation.</cref>
777</t>
778</section>
779
780</section>
781
782
783<section title="Method Definitions" anchor="method.definitions">
784<t>
785   The set of common methods for HTTP/1.1 is defined below. Although
786   this set can be expanded, additional methods cannot be assumed to
787   share the same semantics for separately extended clients and servers.
788</t>
789
790<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
791
792<section title="Safe Methods" anchor="safe.methods">
793<iref item="Safe Methods" primary="true"/>
794<t>
795   Implementors need to be aware that the software represents the user in
796   their interactions over the Internet, and need to allow
797   the user to be aware of any actions they take which might have an
798   unexpected significance to themselves or others.
799</t>
800<t>
801   In particular, the convention has been established that the GET, HEAD,
802   OPTIONS, and TRACE methods &SHOULD-NOT; have the significance of taking an action
803   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
804   This allows user agents to represent other methods, such as POST, PUT
805   and DELETE, in a special way, so that the user is made aware of the
806   fact that a possibly unsafe action is being requested.
807</t>
808<t>
809   Naturally, it is not possible to ensure that the server does not
810   generate side-effects as a result of performing a GET request; in
811   fact, some dynamic resources consider that a feature. The important
812   distinction here is that the user did not request the side-effects,
813   so therefore cannot be held accountable for them.
814</t>
815</section>
816
817<section title="Idempotent Methods" anchor="idempotent.methods">
818<iref item="Idempotent Methods" primary="true"/>
819<t>
820   Methods can also have the property of "idempotence" in that, aside
821   from error or expiration issues, the intended effect of multiple
822   identical requests is the same as for a single request.
823   The methods PUT, DELETE, and all safe methods are idempotent.
824   It is important to note that idempotence refers only to changes
825   requested by the client: a server is free to change its state due
826   to multiple requests for the purpose of tracking those requests,
827   versioning of results, etc.
828</t>
829</section>
830</section>
831
832<section title="OPTIONS" anchor="OPTIONS">
833  <rdf:Description>
834    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
835  </rdf:Description>
836  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
837  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
838<t>
839   The OPTIONS method represents a request for information about the
840   communication options available on the request/response chain
841   identified by the effective request URI. This method allows the client to
842   determine the options and/or requirements associated with a resource,
843   or the capabilities of a server, without implying a resource action
844   or initiating a resource retrieval.
845</t>
846<t>
847   Responses to this method are not cacheable.
848</t>
849<t>
850   If the OPTIONS request includes a message-body (as indicated by the
851   presence of Content-Length or Transfer-Encoding), then the media type
852   &MUST; be indicated by a Content-Type field. Although this
853   specification does not define any use for such a body, future
854   extensions to HTTP might use the OPTIONS body to make more detailed
855   queries on the server.
856</t>
857<t>
858   If the request-target is an asterisk ("*"), the OPTIONS request is
859   intended to apply to the server in general rather than to a specific
860   resource. Since a server's communication options typically depend on
861   the resource, the "*" request is only useful as a "ping" or "no-op"
862   type of method; it does nothing beyond allowing the client to test
863   the capabilities of the server. For example, this can be used to test
864   a proxy for HTTP/1.1 compliance (or lack thereof).
865</t>
866<t>
867   If the request-target is not an asterisk, the OPTIONS request applies
868   only to the options that are available when communicating with that
869   resource.
870</t>
871<t>
872   A 200 response &SHOULD; include any header fields that indicate
873   optional features implemented by the server and applicable to that
874   resource (e.g., Allow), possibly including extensions not defined by
875   this specification. The response body, if any, &SHOULD; also include
876   information about the communication options. The format for such a
877   body is not defined by this specification, but might be defined by
878   future extensions to HTTP. Content negotiation &MAY; be used to select
879   the appropriate response format. If no response body is included, the
880   response &MUST; include a Content-Length field with a field-value of
881   "0".
882</t>
883<t>
884   The Max-Forwards request-header field &MAY; be used to target a
885   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
886   If no Max-Forwards field is present in the request, then the forwarded
887   request &MUST-NOT; include a Max-Forwards field.
888</t>
889</section>
890
891<section title="GET" anchor="GET">
892  <rdf:Description>
893    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
894  </rdf:Description>
895  <iref primary="true" item="GET method" x:for-anchor=""/>
896  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
897<t>
898   The GET method means retrieve whatever information (in the form of a
899   representation) currently corresponds to the target resource.
900</t>
901<t>   
902   If the target resource is a data-producing process, it is the
903   produced data which shall be returned as the representation in the response and not
904   the source text of the process, unless that text happens to be the output of
905   the process.
906</t>
907<t>
908   The semantics of the GET method change to a "conditional GET" if the
909   request message includes an If-Modified-Since, If-Unmodified-Since,
910   If-Match, If-None-Match, or If-Range header field. A conditional GET
911   method requests that the representation be transferred only under the
912   circumstances described by the conditional header field(s). The
913   conditional GET method is intended to reduce unnecessary network
914   usage by allowing cached representations to be refreshed without requiring
915   multiple requests or transferring data already held by the client.
916</t>
917<t>
918   The semantics of the GET method change to a "partial GET" if the
919   request message includes a Range header field. A partial GET requests
920   that only part of the representation be transferred, as described in &header-range;.
921   The partial GET method is intended to reduce unnecessary
922   network usage by allowing partially-retrieved representations to be
923   completed without transferring data already held by the client.
924</t>
925<t>
926   The response to a GET request is cacheable and &MAY; be used to satisfy
927   subsequent GET and HEAD requests (see &caching;).
928</t>
929<t>
930   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
931</t>
932</section>
933
934<section title="HEAD" anchor="HEAD">
935  <rdf:Description>
936    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
937  </rdf:Description>
938  <iref primary="true" item="HEAD method" x:for-anchor=""/>
939  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
940<t>
941   The HEAD method is identical to GET except that the server &MUST-NOT;
942   return a message-body in the response. The metadata contained
943   in the HTTP header fields in response to a HEAD request &SHOULD; be identical
944   to the information sent in response to a GET request. This method can
945   be used for obtaining metadata about the representation implied by the
946   request without transferring the representation body. This method is
947   often used for testing hypertext links for validity, accessibility,
948   and recent modification.
949</t>
950<t>
951   The response to a HEAD request is cacheable and &MAY; be used to satisfy
952   a subsequent HEAD request; see &caching;. It also &MAY; be used to update a previously cached
953   representation from that resource; if the new field values
954   indicate that the cached representation differs from the current representation (as
955   would be indicated by a change in Content-Length, Content-MD5, ETag
956   or Last-Modified), then the cache &MUST; treat the cache entry as
957   stale.
958</t>
959</section>
960
961<section title="POST" anchor="POST">
962  <iref primary="true" item="POST method" x:for-anchor=""/>
963  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
964<t>
965   The POST method is used to request that the origin server accept the
966   representation enclosed in the request as data to be processed by the
967   target resource. POST is designed to allow a uniform method to cover the
968   following functions:
969  <list style="symbols">
970    <t>
971      Annotation of existing resources;
972    </t>
973    <t>
974        Posting a message to a bulletin board, newsgroup, mailing list,
975        or similar group of articles;
976    </t>
977    <t>
978        Providing a block of data, such as the result of submitting a
979        form, to a data-handling process;
980    </t>
981    <t>
982        Extending a database through an append operation.
983    </t>
984  </list>
985</t>
986<t>
987   The actual function performed by the POST method is determined by the
988   server and is usually dependent on the effective request URI.
989</t>
990<t>
991   The action performed by the POST method might not result in a
992   resource that can be identified by a URI. In this case, either 200
993   (OK) or 204 (No Content) is the appropriate response status code,
994   depending on whether or not the response includes a representation that
995   describes the result.
996</t>
997<t>
998   If a resource has been created on the origin server, the response
999   &SHOULD; be 201 (Created) and contain a representation which describes the
1000   status of the request and refers to the new resource, and a Location
1001   header field (see <xref target="header.location"/>).
1002</t>
1003<t>
1004   Responses to POST requests are only cacheable when they
1005   include explicit freshness information (see &p6-explicit;). A
1006   cached POST response with a Content-Location header field
1007   (see &header-content-location;) whose value is the effective
1008   Request URI &MAY; be used to satisfy subsequent GET and HEAD requests.
1009</t>
1010<t>
1011   Note that POST caching is not widely implemented.
1012   However, the 303 (See Other) response can be used to direct the
1013   user agent to retrieve a cacheable resource.
1014</t>
1015</section>
1016
1017<section title="PUT" anchor="PUT">
1018  <iref primary="true" item="PUT method" x:for-anchor=""/>
1019  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
1020<t>
1021   The PUT method requests that the enclosed representation be stored at the
1022   effective request URI. If the effective request URI refers to an already
1023   existing resource, the enclosed representation &SHOULD; be considered a
1024   modified version of the one residing on the origin server. Otherwise, if the
1025   effective request URI does not point to an existing resource, and that URI is
1026   capable of being defined as a new resource by the requesting user
1027   agent, the origin server can create the resource with that URI.
1028</t>
1029<t>   
1030   If a new resource is created at the effective request URI, the origin
1031   server &MUST; inform the user agent
1032   via the 201 (Created) response. If an existing resource is modified,
1033   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
1034   to indicate successful completion of the request.
1035</t>
1036<t>   
1037   If the target resource could not be created or modified, an appropriate
1038   error response &SHOULD; be given that reflects the nature of the problem.
1039   The recipient of the representation &MUST-NOT; ignore any Content-*
1040   header fields (headers starting with the prefix "Content-") that it does
1041   not understand or implement
1042   and &MUST; return a 501 (Not Implemented) response in such cases.
1043</t>
1044<t>
1045   If the request passes through a cache that has one or more stored
1046   responses for the effective request URI, those stored responses
1047   &SHOULD; be marked as stale if the response to the PUT request
1048   has a success status code. Responses to the PUT method are
1049   not cacheable.
1050</t>
1051<t>
1052   The fundamental difference between the POST and PUT requests is
1053   reflected in the different meaning of the effective request URI. The URI in a
1054   POST request identifies the resource that will handle the enclosed
1055   representation. That resource might be a data-accepting process, a gateway to
1056   some other protocol, or a document that accepts annotations.
1057   In contrast, the URI in a PUT request identifies the resource for
1058   which enclosed representation is a new or replacement value; the
1059   user agent knows what URI is intended and the server &MUST-NOT; attempt
1060   to apply the request to some other resource.
1061   If the server desires that the request be applied to a different URI,
1062   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
1063   then make its own decision regarding whether or not to redirect the
1064   request.
1065</t>
1066<t>
1067   A single resource &MAY; be identified by many different URIs. For
1068   example, an article might have a URI for identifying "the current
1069   version" which is separate from the URI identifying each particular
1070   version. In this case, a PUT request on a general URI might result in
1071   several other URIs being defined by the origin server.
1072</t>
1073<t>
1074   HTTP/1.1 does not define how a PUT method affects the state of an
1075   origin server.
1076</t>
1077<t>
1078   Header fields in a PUT request that are recognized as representation
1079   metadata &SHOULD; be applied to the resource created or modified by
1080   the PUT.  Unrecognized header fields &SHOULD; be ignored.
1081</t>
1082</section>
1083
1084<section title="DELETE" anchor="DELETE">
1085  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1086  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1087<t>
1088   The DELETE method requests that the origin server delete the target
1089   resource. This method &MAY; be overridden by
1090   human intervention (or other means) on the origin server. The client cannot
1091   be guaranteed that the operation has been carried out, even if the
1092   status code returned from the origin server indicates that the action
1093   has been completed successfully. However, the server &SHOULD-NOT; 
1094   indicate success unless, at the time the response is given, it
1095   intends to delete the resource or move it to an inaccessible
1096   location.
1097</t>
1098<t>
1099   A successful response &SHOULD; be 200 (OK) if the response includes an
1100   representation describing the status, 202 (Accepted) if the action has not
1101   yet been enacted, or 204 (No Content) if the action has been enacted
1102   but the response does not include a representation.
1103</t>
1104<t>
1105   If the request passes through a cache and the effective request URI
1106   identifies one or more currently cached representations, those entries &SHOULD; be
1107   treated as stale. Responses to the DELETE method are not cacheable.
1108</t>
1109</section>
1110
1111<section title="TRACE" anchor="TRACE">
1112  <rdf:Description>
1113    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1114  </rdf:Description>
1115  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1116  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1117<t>
1118   The TRACE method is used to invoke a remote, application-layer loop-back
1119   of the request message. The final recipient of the request
1120   &SHOULD; reflect the message received back to the client as the
1121   message-body of a 200 (OK) response. The final recipient is either the
1122   origin server or the first proxy or gateway to receive a Max-Forwards
1123   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1124   A TRACE request &MUST-NOT; include a message-body.
1125</t>
1126<t>
1127   TRACE allows the client to see what is being received at the other
1128   end of the request chain and use that data for testing or diagnostic
1129   information. The value of the Via header field (&header-via;) is of
1130   particular interest, since it acts as a trace of the request chain.
1131   Use of the Max-Forwards header field allows the client to limit the
1132   length of the request chain, which is useful for testing a chain of
1133   proxies forwarding messages in an infinite loop.
1134</t>
1135<t>
1136   If the request is valid, the response &SHOULD; have a Content-Type of
1137   "message/http" (see &media-type-message-http;) and contain a message-body
1138   that encloses a copy of the entire request message.
1139   Responses to the TRACE method are not cacheable.
1140</t>
1141</section>
1142
1143<section title="CONNECT" anchor="CONNECT">
1144  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1145  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1146<t>
1147   The CONNECT method is used with a proxy to dynamically switch
1148   the connection to a tunnel.
1149</t>
1150<t>
1151   When using CONNECT, the request-target &MUST; be use the authority form
1152   (&request-target;); i.e., the host name and port number destination of the
1153   requested connection separated by a colon:
1154</t>
1155<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1156CONNECT server.example.com:80 HTTP/1.1
1157Host: server.example.com:80
1158
1159</artwork></figure>
1160<t>
1161   Other HTTP mechanisms can be used normally with the CONNECT method --
1162   except end-to-end protocol Upgrade requests, since the
1163   tunnel must be established first.
1164</t>
1165<t>
1166   For example, proxy authentication might be used to establish the
1167   authority to create a tunnel:
1168</t>
1169<figure><artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1170CONNECT server.example.com:80 HTTP/1.1
1171Host: server.example.com:80
1172Proxy-Authorization: basic aGVsbG86d29ybGQ=
1173
1174</artwork></figure>
1175<t>
1176   Like any other pipelined HTTP/1.1 request, data to be tunnel may be
1177   sent immediately after the blank line. The usual caveats also apply:
1178   data may be discarded if the eventual response is negative, and the
1179   connection may be reset with no response if more than one TCP segment
1180   is outstanding.
1181</t>
1182
1183<section title="Establishing a Tunnel with CONNECT">
1184<t>
1185   Any successful (2xx) response to a CONNECT request indicates that the
1186   proxy has established a connection to the requested host and port,
1187   and has switched to tunneling the current connection to that server
1188   connection.
1189</t>
1190<t>
1191   It may be the case that the proxy itself can only reach the requested
1192   origin server through another proxy.  In this case, the first proxy
1193   &SHOULD; make a CONNECT request of that next proxy, requesting a tunnel
1194   to the authority.  A proxy &MUST-NOT; respond with any 2xx status code
1195   unless it has either a direct or tunnel connection established to the
1196   authority.
1197</t>
1198<t>
1199   An origin server which receives a CONNECT request for itself &MAY;
1200   respond with a 2xx status code to indicate that a connection is
1201   established.
1202</t>
1203<t>
1204   If at any point either one of the peers gets disconnected, any
1205   outstanding data that came from that peer will be passed to the other
1206   one, and after that also the other connection will be terminated by
1207   the proxy. If there is outstanding data to that peer undelivered,
1208   that data will be discarded.
1209</t>
1210
1211</section>
1212</section>
1213</section>
1214
1215
1216<section title="Status Code Definitions" anchor="status.codes">
1217<t>
1218   Each Status-Code is described below, including any metadata required
1219   in the response.
1220</t>
1221
1222<section title="Informational 1xx" anchor="status.1xx">
1223<t>
1224   This class of status code indicates a provisional response,
1225   consisting only of the Status-Line and optional header fields, and is
1226   terminated by an empty line. There are no required header fields for this
1227   class of status code. Since HTTP/1.0 did not define any 1xx status
1228   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1229   except under experimental conditions.
1230</t>
1231<t>
1232   A client &MUST; be prepared to accept one or more 1xx status responses
1233   prior to a regular response, even if the client does not expect a 100
1234   (Continue) status message. Unexpected 1xx status responses &MAY; be
1235   ignored by a user agent.
1236</t>
1237<t>
1238   Proxies &MUST; forward 1xx responses, unless the connection between the
1239   proxy and its client has been closed, or unless the proxy itself
1240   requested the generation of the 1xx response. (For example, if a
1241   proxy adds a "Expect: 100-continue" field when it forwards a request,
1242   then it need not forward the corresponding 100 (Continue)
1243   response(s).)
1244</t>
1245
1246<section title="100 Continue" anchor="status.100">
1247  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1248  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1249<t>
1250   The client &SHOULD; continue with its request. This interim response is
1251   used to inform the client that the initial part of the request has
1252   been received and has not yet been rejected by the server. The client
1253   &SHOULD; continue by sending the remainder of the request or, if the
1254   request has already been completed, ignore this response. The server
1255   &MUST; send a final response after the request has been completed. See
1256   &use100; for detailed discussion of the use and handling of this
1257   status code.
1258</t>
1259</section>
1260
1261<section title="101 Switching Protocols" anchor="status.101">
1262  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1263  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1264<t>
1265   The server understands and is willing to comply with the client's
1266   request, via the Upgrade message header field (&header-upgrade;), for a
1267   change in the application protocol being used on this connection. The
1268   server will switch protocols to those defined by the response's
1269   Upgrade header field immediately after the empty line which
1270   terminates the 101 response.
1271</t>
1272<t>
1273   The protocol &SHOULD; be switched only when it is advantageous to do
1274   so. For example, switching to a newer version of HTTP is advantageous
1275   over older versions, and switching to a real-time, synchronous
1276   protocol might be advantageous when delivering resources that use
1277   such features.
1278</t>
1279</section>
1280</section>
1281
1282<section title="Successful 2xx" anchor="status.2xx">
1283<t>
1284   This class of status code indicates that the client's request was
1285   successfully received, understood, and accepted.
1286</t>
1287
1288<section title="200 OK" anchor="status.200">
1289  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1290  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1291<t>
1292   The request has succeeded. The payload returned with the response
1293   is dependent on the method used in the request, for example:
1294  <list style="hanging">
1295    <t hangText="GET">
1296          a representation of the target resource is sent in the response;
1297    </t>
1298    <t hangText="HEAD">
1299          the same representation as GET, except without the message-body;
1300    </t>
1301    <t hangText="POST">
1302      a representation describing or containing the result of the action;
1303    </t>
1304    <t hangText="TRACE">
1305      a representation containing the request message as received by the
1306      end server.
1307    </t>
1308  </list>
1309</t>
1310<t>
1311   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1312   freshness for 200 responses.
1313</t>
1314</section>
1315
1316<section title="201 Created" anchor="status.201">
1317  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1318  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1319<t>
1320   The request has been fulfilled and has resulted in a new resource being
1321   created. The newly created resource can be referenced by the URI(s)
1322   returned in the payload of the response, with the most specific URI
1323   for the resource given by a Location header field. The response
1324   &SHOULD; include a payload containing a list of resource
1325   characteristics and location(s) from which the user or user agent can
1326   choose the one most appropriate. The payload format is specified by
1327   the media type given in the Content-Type header field. The origin
1328   server &MUST; create the resource before returning the 201 status code.
1329   If the action cannot be carried out immediately, the server &SHOULD;
1330   respond with 202 (Accepted) response instead.
1331</t>
1332<t>
1333   A 201 response &MAY; contain an ETag response header field indicating
1334   the current value of the entity-tag for the representation of the resource
1335   just created (see &header-etag;).
1336</t>
1337</section>
1338
1339<section title="202 Accepted" anchor="status.202">
1340  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1341  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1342<t>
1343   The request has been accepted for processing, but the processing has
1344   not been completed.  The request might or might not eventually be
1345   acted upon, as it might be disallowed when processing actually takes
1346   place. There is no facility for re-sending a status code from an
1347   asynchronous operation such as this.
1348</t>
1349<t>
1350   The 202 response is intentionally non-committal. Its purpose is to
1351   allow a server to accept a request for some other process (perhaps a
1352   batch-oriented process that is only run once per day) without
1353   requiring that the user agent's connection to the server persist
1354   until the process is completed. The representation returned with this
1355   response &SHOULD; include an indication of the request's current status
1356   and either a pointer to a status monitor or some estimate of when the
1357   user can expect the request to be fulfilled.
1358</t>
1359</section>
1360
1361<section title="203 Non-Authoritative Information" anchor="status.203">
1362  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1363  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1364<t>
1365   The returned metadata in the header fields is not the
1366   definitive set as available from the origin server, but is gathered
1367   from a local or a third-party copy. The set presented &MAY; be a subset
1368   or superset of the original version. For example, including local
1369   annotation information about the resource might result in a superset
1370   of the metadata known by the origin server. Use of this
1371   response code is not required and is only appropriate when the
1372   response would otherwise be 200 (OK).
1373</t>
1374<t>
1375   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1376   freshness for 203 responses.
1377</t>
1378
1379</section>
1380
1381<section title="204 No Content" anchor="status.204">
1382  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1383  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1384<t>
1385   The server has successfully fulfilled the request, but there is no
1386   additional content to return in the response payload body.  The
1387   resource metadata and representation metadata in the response message's
1388   header fields refer to the target resource
1389   and its current representation, respectively, after the requested action.
1390   For example, if a 204 status code is received in response to a PUT
1391   and the response contains an ETag header field, then the value of
1392   that field is the current entity-tag for the representation that
1393   was successfully PUT.
1394</t>
1395<t>
1396   If the client is a user agent, it &SHOULD-NOT; change its document view
1397   from that which caused the request to be sent. This response is
1398   primarily intended to allow input for actions to take place without
1399   causing a change to the user agent's active document view, although
1400   any new or updated metadata &SHOULD; be applied to the document
1401   currently in the user agent's active view.
1402</t>
1403<t>
1404   The 204 response &MUST-NOT; include a message-body, and thus is always
1405   terminated by the first empty line after the header fields.
1406</t>
1407</section>
1408
1409<section title="205 Reset Content" anchor="status.205">
1410  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1411  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1412<t>
1413   The server has fulfilled the request and the user agent &SHOULD; reset
1414   the document view which caused the request to be sent. This response
1415   is primarily intended to allow input for actions to take place via
1416   user input, followed by a clearing of the form in which the input is
1417   given so that the user can easily initiate another input action.
1418</t>
1419<t>   
1420   The message-body included with the response &MUST; be empty. Note that
1421   receivers still need to parse the response according to the algorithm defined
1422   in &message-body;.
1423</t>
1424</section>
1425
1426<section title="206 Partial Content" anchor="status.206">
1427  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1428  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1429  <rdf:Description>
1430    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1431  </rdf:Description>
1432<t>
1433   The server has fulfilled the partial GET request for the resource
1434   and the enclosed payload is a partial representation as defined in &status-206;.
1435</t>
1436<t>
1437   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1438   freshness for 206 responses.
1439</t>
1440</section>
1441</section>
1442
1443<section title="Redirection 3xx" anchor="status.3xx">
1444<t>
1445   This class of status code indicates that further action needs to be
1446   taken by the user agent in order to fulfill the request.  The action
1447   required &MAY; be carried out by the user agent without interaction
1448   with the user if and only if the method used in the second request is
1449   known to be "safe", as defined in <xref target="safe.methods"/>.
1450   A client &SHOULD; detect infinite redirection loops, since such loops
1451   generate network traffic for each redirection.
1452</t>
1453<x:note>
1454  <t>
1455    <x:h>Note:</x:h> An earlier version of this specification recommended a
1456    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1457    Content developers need to be aware that some clients might
1458    implement such a fixed limitation.
1459  </t>
1460</x:note>
1461
1462<section title="300 Multiple Choices" anchor="status.300">
1463  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1464  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1465<t>
1466   The target resource has more than one
1467   representation, each with its own specific location, and agent-driven
1468   negotiation information (&content-negotiation;) is being provided so that
1469   the user (or user agent) can select a preferred representation by
1470   redirecting its request to that location.
1471</t>
1472<t>
1473   Unless it was a HEAD request, the response &SHOULD; include a representation
1474   containing a list of representation metadata and location(s) from
1475   which the user or user agent can choose the one most appropriate. The
1476   data format is specified by the media type given in the Content-Type
1477   header field. Depending upon the format and the capabilities of
1478   the user agent, selection of the most appropriate choice &MAY; be
1479   performed automatically. However, this specification does not define
1480   any standard for such automatic selection.
1481</t>
1482<t>
1483   If the server has a preferred choice of representation, it &SHOULD;
1484   include the specific URI for that representation in the Location
1485   field; user agents &MAY; use the Location field value for automatic
1486   redirection.
1487</t>
1488<t>
1489   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1490   freshness for 300 responses.
1491</t>
1492
1493</section>
1494
1495<section title="301 Moved Permanently" anchor="status.301">
1496  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1497  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1498<t>
1499   The target resource has been assigned a new permanent URI and any
1500   future references to this resource &SHOULD; use one of the returned
1501   URIs.  Clients with link editing capabilities ought to automatically
1502   re-link references to the effective request URI to one or more of the new
1503   references returned by the server, where possible.
1504</t>
1505<t>
1506   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1507   freshness for 301 responses.
1508</t>
1509<t>
1510   The new permanent URI &SHOULD; be given by the Location field in the
1511   response. Unless the request method was HEAD, the representation of the
1512   response &SHOULD; contain a short hypertext note with a hyperlink to
1513   the new URI(s).
1514</t>
1515<t>
1516   If the 301 status code is received in response to a request method
1517   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1518   then the request &MAY; be automatically redirected by the user agent without
1519   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1520   request unless it can be confirmed by the user, since this might
1521   change the conditions under which the request was issued.
1522</t>
1523<x:note>
1524  <t>
1525    <x:h>Note:</x:h> When automatically redirecting a POST request after
1526    receiving a 301 status code, some existing HTTP/1.0 user agents
1527    will erroneously change it into a GET request.
1528  </t>
1529</x:note>
1530</section>
1531
1532<section title="302 Found" anchor="status.302">
1533  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1534  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1535<t>
1536   The target resource resides temporarily under a different URI.
1537   Since the redirection might be altered on occasion, the client &SHOULD;
1538   continue to use the effective request URI for future requests.
1539</t>
1540<t>
1541   The temporary URI &SHOULD; be given by the Location field in the
1542   response. Unless the request method was HEAD, the representation of the
1543   response &SHOULD; contain a short hypertext note with a hyperlink to
1544   the new URI(s).
1545</t>
1546<t>
1547   If the 302 status code is received in response to a request method
1548   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1549   then the request &MAY; be automatically redirected by the user agent without
1550   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1551   request unless it can be confirmed by the user, since this might
1552   change the conditions under which the request was issued.
1553</t>
1554<x:note>
1555  <t>
1556    <x:h>Note:</x:h> HTTP/1.0 (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>)
1557    and the first version of HTTP/1.1 (<xref target="RFC2068" x:fmt="," x:sec ="10.3.3"/>)
1558    specify that the client is not allowed to change the method on the
1559    redirected request.  However, most existing user agent implementations
1560    treat 302 as if it were a 303 response, performing a GET on the Location
1561    field-value regardless of the original request method. Therefore, a
1562    previous version of this specification
1563    (<xref target="RFC2616" x:fmt="," x:sec="10.3.3"/>) has added the
1564    status codes
1565    <xref target="status.303" format="none">303</xref> and
1566    <xref target="status.307" format="none">307</xref> for servers that wish
1567    to make unambiguously clear which kind of reaction is expected of the
1568    client.
1569  </t>
1570</x:note>
1571</section>
1572
1573<section title="303 See Other" anchor="status.303">
1574  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1575  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1576<t>
1577   The server directs the user agent to a different resource, indicated
1578   by a URI in the Location header field, that provides an indirect
1579   response to the original request.  The user agent &MAY; perform a GET
1580   request on the URI in the Location field in order to obtain a
1581   representation corresponding to the response, be redirected again,
1582   or end with an error status.  The Location URI is not a substitute
1583   reference for the effective request URI.
1584</t>
1585<t>
1586   The 303 status code is generally applicable to any HTTP method.  It is
1587   primarily used to allow the output of a POST action to redirect
1588   the user agent to a selected resource, since doing so provides the
1589   information corresponding to the POST response in a form that
1590   can be separately identified, bookmarked, and cached independent
1591   of the original request.
1592</t>
1593<t>
1594   A 303 response to a GET request indicates that the requested
1595   resource does not have a representation of its own that can be
1596   transferred by the server over HTTP.  The Location URI indicates a
1597   resource that is descriptive of the target resource, such that the
1598   follow-on representation might be useful to recipients without
1599   implying that it adequately represents the target resource.
1600   Note that answers to the questions of what can be represented, what
1601   representations are adequate, and what might be a useful description
1602   are outside the scope of HTTP and thus entirely determined by the
1603   URI owner(s).
1604</t>
1605<t>
1606   Except for responses to a HEAD request, the representation of a 303
1607   response &SHOULD; contain a short hypertext note with a hyperlink
1608   to the Location URI.
1609</t>
1610</section>
1611
1612<section title="304 Not Modified" anchor="status.304">
1613  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1614  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1615  <rdf:Description>
1616    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1617  </rdf:Description>
1618<t>
1619   The response to the request has not been modified since the conditions
1620   indicated by the client's conditional GET request, as defined in &status-304;.
1621</t>
1622</section>
1623
1624<section title="305 Use Proxy" anchor="status.305">
1625  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1626  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1627<t>
1628   The 305 status code was defined in a previous version of this specification
1629   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1630</t>
1631</section>
1632
1633<section title="306 (Unused)" anchor="status.306">
1634  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1635  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1636<t>
1637   The 306 status code was used in a previous version of the
1638   specification, is no longer used, and the code is reserved.
1639</t>
1640</section>
1641
1642<section title="307 Temporary Redirect" anchor="status.307">
1643  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1644  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1645<t>
1646   The target resource resides temporarily under a different URI.
1647   Since the redirection can change over time, the client &SHOULD;
1648   continue to use the effective request URI for future requests.
1649</t>
1650<t>
1651   The temporary URI &SHOULD; be given by the Location field in the
1652   response. Unless the request method was HEAD, the representation of the
1653   response &SHOULD; contain a short hypertext note with a hyperlink to
1654   the new URI(s), since many pre-HTTP/1.1 user agents do not
1655   understand the 307 status code. Therefore, the note &SHOULD; contain the
1656   information necessary for a user to repeat the original request on
1657   the new URI.
1658</t>
1659<t>
1660   If the 307 status code is received in response to a request method
1661   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1662   then the request &MAY; be automatically redirected by the user agent without
1663   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1664   request unless it can be confirmed by the user, since this might
1665   change the conditions under which the request was issued.
1666</t>
1667</section>
1668</section>
1669
1670<section title="Client Error 4xx" anchor="status.4xx">
1671<t>
1672   The 4xx class of status code is intended for cases in which the
1673   client seems to have erred. Except when responding to a HEAD request,
1674   the server &SHOULD; include a representation containing an explanation of the
1675   error situation, and whether it is a temporary or permanent
1676   condition. These status codes are applicable to any request method.
1677   User agents &SHOULD; display any included representation to the user.
1678</t>
1679<t>
1680   If the client is sending data, a server implementation using TCP
1681   &SHOULD; be careful to ensure that the client acknowledges receipt of
1682   the packet(s) containing the response, before the server closes the
1683   input connection. If the client continues sending data to the server
1684   after the close, the server's TCP stack will send a reset packet to
1685   the client, which might erase the client's unacknowledged input buffers
1686   before they can be read and interpreted by the HTTP application.
1687</t>
1688
1689<section title="400 Bad Request" anchor="status.400">
1690  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1691  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1692<t>
1693   The request could not be understood by the server due to malformed
1694   syntax. The client &SHOULD-NOT; repeat the request without
1695   modifications.
1696</t>
1697</section>
1698
1699<section title="401 Unauthorized" anchor="status.401">
1700  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1701  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1702  <rdf:Description>
1703    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1704  </rdf:Description>
1705<t>
1706   The request requires user authentication (see &status-401;).
1707</t>
1708</section>
1709
1710<section title="402 Payment Required" anchor="status.402">
1711  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1712  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1713<t>
1714   This code is reserved for future use.
1715</t>
1716</section>
1717
1718<section title="403 Forbidden" anchor="status.403">
1719  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1720  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1721<t>
1722   The server understood the request, but is refusing to fulfill it.
1723   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1724   If the request method was not HEAD and the server wishes to make
1725   public why the request has not been fulfilled, it &SHOULD; describe the
1726   reason for the refusal in the representation.  If the server does not wish to
1727   make this information available to the client, the status code 404
1728   (Not Found) can be used instead.
1729</t>
1730</section>
1731
1732<section title="404 Not Found" anchor="status.404">
1733  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1734  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1735<t>
1736   The server has not found anything matching the effective request URI. No
1737   indication is given of whether the condition is temporary or
1738   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1739   knows, through some internally configurable mechanism, that an old
1740   resource is permanently unavailable and has no forwarding address.
1741   This status code is commonly used when the server does not wish to
1742   reveal exactly why the request has been refused, or when no other
1743   response is applicable.
1744</t>
1745</section>
1746
1747<section title="405 Method Not Allowed" anchor="status.405">
1748  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1749  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1750<t>
1751   The method specified in the Request-Line is not allowed for the target
1752   resource. The response &MUST; include an
1753   Allow header field containing a list of valid methods for the requested
1754   resource.
1755</t>
1756</section>
1757
1758<section title="406 Not Acceptable" anchor="status.406">
1759  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1760  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1761<t>
1762   The resource identified by the request is only capable of generating
1763   response representations which have content characteristics not acceptable
1764   according to the accept header fields sent in the request.
1765</t>
1766<t>
1767   Unless it was a HEAD request, the response &SHOULD; include a representation
1768   containing a list of available representation characteristics and location(s)
1769   from which the user or user agent can choose the one most
1770   appropriate. The data format is specified by the media type given
1771   in the Content-Type header field. Depending upon the format and the
1772   capabilities of the user agent, selection of the most appropriate
1773   choice &MAY; be performed automatically. However, this specification
1774   does not define any standard for such automatic selection.
1775</t>
1776<x:note>
1777  <t>
1778    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1779    not acceptable according to the accept header fields sent in the
1780    request. In some cases, this might even be preferable to sending a
1781    406 response. User agents are encouraged to inspect the header fields of
1782    an incoming response to determine if it is acceptable.
1783  </t>
1784</x:note>
1785<t>
1786   If the response could be unacceptable, a user agent &SHOULD;
1787   temporarily stop receipt of more data and query the user for a
1788   decision on further actions.
1789</t>
1790</section>
1791
1792<section title="407 Proxy Authentication Required" anchor="status.407">
1793  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1794  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1795<t>
1796   This code is similar to 401 (Unauthorized), but indicates that the
1797   client must first authenticate itself with the proxy (see &status-407;).
1798</t>
1799</section>
1800
1801<section title="408 Request Timeout" anchor="status.408">
1802  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1803  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1804<t>
1805   The client did not produce a request within the time that the server
1806   was prepared to wait. The client &MAY; repeat the request without
1807   modifications at any later time.
1808</t>
1809</section>
1810
1811<section title="409 Conflict" anchor="status.409">
1812  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1813  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1814<t>
1815   The request could not be completed due to a conflict with the current
1816   state of the resource. This code is only allowed in situations where
1817   it is expected that the user might be able to resolve the conflict
1818   and resubmit the request. The response body &SHOULD; include enough
1819   information for the user to recognize the source of the conflict.
1820   Ideally, the response representation would include enough information for the
1821   user or user agent to fix the problem; however, that might not be
1822   possible and is not required.
1823</t>
1824<t>
1825   Conflicts are most likely to occur in response to a PUT request. For
1826   example, if versioning were being used and the representation being PUT
1827   included changes to a resource which conflict with those made by an
1828   earlier (third-party) request, the server might use the 409 response
1829   to indicate that it can't complete the request. In this case, the
1830   response representation would likely contain a list of the differences
1831   between the two versions in a format defined by the response
1832   Content-Type.
1833</t>
1834</section>
1835
1836<section title="410 Gone" anchor="status.410">
1837  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1838  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1839<t>
1840   The target resource is no longer available at the server and no
1841   forwarding address is known. This condition is expected to be
1842   considered permanent. Clients with link editing capabilities &SHOULD;
1843   delete references to the effective request URI after user approval. If the
1844   server does not know, or has no facility to determine, whether or not
1845   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1846   used instead.
1847</t>
1848<t>
1849   The 410 response is primarily intended to assist the task of web
1850   maintenance by notifying the recipient that the resource is
1851   intentionally unavailable and that the server owners desire that
1852   remote links to that resource be removed. Such an event is common for
1853   limited-time, promotional services and for resources belonging to
1854   individuals no longer working at the server's site. It is not
1855   necessary to mark all permanently unavailable resources as "gone" or
1856   to keep the mark for any length of time -- that is left to the
1857   discretion of the server owner.
1858</t>
1859<t>
1860   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine freshness
1861   for 410 responses.
1862</t>
1863
1864</section>
1865
1866<section title="411 Length Required" anchor="status.411">
1867  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1868  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1869<t>
1870   The server refuses to accept the request without a defined Content-Length.
1871   The client &MAY; repeat the request if it adds a valid
1872   Content-Length header field containing the length of the message-body
1873   in the request message.
1874</t>
1875</section>
1876
1877<section title="412 Precondition Failed" anchor="status.412">
1878  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1879  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1880  <rdf:Description>
1881    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1882  </rdf:Description>
1883<t>
1884   The precondition given in one or more of the request-header fields
1885   evaluated to false when it was tested on the server, as defined in
1886   &status-412;.
1887</t>
1888</section>
1889
1890<section title="413 Request Entity Too Large" anchor="status.413">
1891  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1892  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1893<t>
1894   The server is refusing to process a request because the request
1895   representation is larger than the server is willing or able to process. The
1896   server &MAY; close the connection to prevent the client from continuing
1897   the request.
1898</t>
1899<t>
1900   If the condition is temporary, the server &SHOULD; include a Retry-After
1901   header field to indicate that it is temporary and after what
1902   time the client &MAY; try again.
1903</t>
1904</section>
1905
1906<section title="414 URI Too Long" anchor="status.414">
1907  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
1908  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
1909<t>
1910   The server is refusing to service the request because the effective request URI
1911   is longer than the server is willing to interpret. This rare
1912   condition is only likely to occur when a client has improperly
1913   converted a POST request to a GET request with long query
1914   information, when the client has descended into a URI "black hole" of
1915   redirection (e.g., a redirected URI prefix that points to a suffix of
1916   itself), or when the server is under attack by a client attempting to
1917   exploit security holes present in some servers using fixed-length
1918   buffers for reading or manipulating the effective request URI.
1919</t>
1920</section>
1921
1922<section title="415 Unsupported Media Type" anchor="status.415">
1923  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1924  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1925<t>
1926   The server is refusing to service the request because the representation of
1927   the request is in a format not supported by the target resource
1928   for the requested method.
1929</t>
1930</section>
1931
1932<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1933  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1934  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1935  <rdf:Description>
1936    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1937  </rdf:Description>
1938<t>
1939   The request included a Range request-header field (&header-range;) and none of
1940   the range-specifier values in this field overlap the current extent
1941   of the selected resource. See &status-416;.
1942</t>
1943</section>
1944
1945<section title="417 Expectation Failed" anchor="status.417">
1946  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1947  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1948<t>
1949   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1950   could not be met by this server, or, if the server is a proxy,
1951   the server has unambiguous evidence that the request could not be met
1952   by the next-hop server.
1953</t>
1954</section>
1955
1956<section title="426 Upgrade Required" anchor="status.426">
1957  <iref primary="true" item="426 Upgrade Required (status code)" x:for-anchor=""/>
1958  <iref primary="true" item="Status Codes" subitem="426 Upgrade Required" x:for-anchor=""/>
1959<t>
1960   The request can not be completed without a prior protocol upgrade. This
1961   response &MUST; include an Upgrade header field (&header-upgrade;)
1962   specifying the required protocols.
1963</t>
1964<figure>
1965<preamble>Example:</preamble>
1966<artwork type="message/http; msgtype=&#34;request&#34;" x:indent-with="  ">
1967HTTP/1.1 426 Upgrade Required
1968Upgrade: HTTP/2.0
1969Connection: Upgrade
1970
1971</artwork></figure>
1972<t>
1973   The server &SHOULD; include a message body in the 426 response which
1974   indicates in human readable form the reason for the error and describes any
1975   alternative courses which may be available to the user.
1976</t>
1977</section>
1978</section>
1979
1980<section title="Server Error 5xx" anchor="status.5xx">
1981<t>
1982   Response status codes beginning with the digit "5" indicate cases in
1983   which the server is aware that it has erred or is incapable of
1984   performing the request. Except when responding to a HEAD request, the
1985   server &SHOULD; include a representation containing an explanation of the
1986   error situation, and whether it is a temporary or permanent
1987   condition. User agents &SHOULD; display any included representation to the
1988   user. These response codes are applicable to any request method.
1989</t>
1990
1991<section title="500 Internal Server Error" anchor="status.500">
1992  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1993  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1994<t>
1995   The server encountered an unexpected condition which prevented it
1996   from fulfilling the request.
1997</t>
1998</section>
1999
2000<section title="501 Not Implemented" anchor="status.501">
2001  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
2002  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
2003<t>
2004   The server does not support the functionality required to fulfill the
2005   request. This is the appropriate response when the server does not
2006   recognize the request method and is not capable of supporting it for
2007   any resource.
2008</t>
2009</section>
2010
2011<section title="502 Bad Gateway" anchor="status.502">
2012  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
2013  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
2014<t>
2015   The server, while acting as a gateway or proxy, received an invalid
2016   response from the upstream server it accessed in attempting to
2017   fulfill the request.
2018</t>
2019</section>
2020
2021<section title="503 Service Unavailable" anchor="status.503">
2022  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
2023  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
2024<t>
2025   The server is currently unable to handle the request due to a
2026   temporary overloading or maintenance of the server. The implication
2027   is that this is a temporary condition which will be alleviated after
2028   some delay. If known, the length of the delay &MAY; be indicated in a
2029   Retry-After header field. If no Retry-After is given, the client &SHOULD;
2030   handle the response as it would for a 500 response.
2031</t>
2032<x:note>
2033  <t>
2034    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
2035    server must use it when becoming overloaded. Some servers might wish
2036    to simply refuse the connection.
2037  </t>
2038</x:note>
2039</section>
2040
2041<section title="504 Gateway Timeout" anchor="status.504">
2042  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
2043  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
2044<t>
2045   The server, while acting as a gateway or proxy, did not receive a
2046   timely response from the upstream server specified by the URI (e.g.,
2047   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
2048   to access in attempting to complete the request.
2049</t>
2050<x:note>
2051  <t>
2052    <x:h>Note</x:h> to implementors: some deployed proxies are known to
2053    return 400 or 500 when DNS lookups time out.
2054  </t>
2055</x:note>
2056</section>
2057
2058<section title="505 HTTP Version Not Supported" anchor="status.505">
2059  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
2060  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
2061<t>
2062   The server does not support, or refuses to support, the protocol
2063   version that was used in the request message. The server is
2064   indicating that it is unable or unwilling to complete the request
2065   using the same major version as the client, as described in &http-version;,
2066   other than with this error message. The response &SHOULD; contain
2067   a representation describing why that version is not supported and what other
2068   protocols are supported by that server.
2069</t>
2070
2071</section>
2072</section>
2073</section>
2074
2075
2076<section title="Header Field Definitions" anchor="header.fields">
2077<t>
2078   This section defines the syntax and semantics of HTTP/1.1 header fields
2079   related to request and response semantics.
2080</t>
2081
2082<section title="Allow" anchor="header.allow">
2083  <iref primary="true" item="Allow header" x:for-anchor=""/>
2084  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
2085  <x:anchor-alias value="Allow"/>
2086  <x:anchor-alias value="Allow-v"/>
2087<t>
2088   The "Allow" response-header field lists the set of methods advertised as
2089   supported by the target resource. The purpose of this field is strictly to
2090   inform the recipient of valid methods associated with the resource.
2091</t>
2092<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
2093  <x:ref>Allow</x:ref>   = "Allow" ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
2094  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
2095</artwork></figure>
2096<t>
2097   Example of use:
2098</t>
2099<figure><artwork type="example">
2100  Allow: GET, HEAD, PUT
2101</artwork></figure>
2102<t>
2103   The actual set of allowed methods is defined by the origin server at the
2104   time of each request.
2105</t>
2106<t>
2107   A proxy &MUST-NOT; modify the Allow header field -- it does not need to
2108   understand all the methods specified in order to handle them according to
2109   the generic message handling rules.
2110</t>
2111</section>
2112
2113<section title="Expect" anchor="header.expect">
2114  <iref primary="true" item="Expect header" x:for-anchor=""/>
2115  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
2116  <x:anchor-alias value="Expect"/>
2117  <x:anchor-alias value="Expect-v"/>
2118  <x:anchor-alias value="expectation"/>
2119  <x:anchor-alias value="expectation-extension"/>
2120  <x:anchor-alias value="expect-params"/>
2121<t>
2122   The "Expect" request-header field is used to indicate that particular
2123   server behaviors are required by the client.
2124</t>
2125<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"/>
2126  <x:ref>Expect</x:ref>       = "Expect" ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
2127  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
2128 
2129  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
2130  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
2131                           *<x:ref>expect-params</x:ref> ]
2132  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
2133</artwork></figure>
2134<t>
2135   A server that does not understand or is unable to comply with any of
2136   the expectation values in the Expect field of a request &MUST; respond
2137   with appropriate error status code. The server &MUST; respond with a 417
2138   (Expectation Failed) status code if any of the expectations cannot be met
2139   or, if there are other problems with the request, some other 4xx
2140   status code.
2141</t>
2142<t>
2143   This header field is defined with extensible syntax to allow for
2144   future extensions. If a server receives a request containing an
2145   Expect field that includes an expectation-extension that it does not
2146   support, it &MUST; respond with a 417 (Expectation Failed) status code.
2147</t>
2148<t>
2149   Comparison of expectation values is case-insensitive for unquoted
2150   tokens (including the 100-continue token), and is case-sensitive for
2151   quoted-string expectation-extensions.
2152</t>
2153<t>
2154   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
2155   return a 417 (Expectation Failed) status code if it receives a request
2156   with an expectation that it cannot meet. However, the Expect
2157   request-header field itself is end-to-end; it &MUST; be forwarded if the
2158   request is forwarded.
2159</t>
2160<t>
2161   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
2162   Expect header field.
2163</t>
2164<t>
2165   See &use100; for the use of the 100 (Continue) status code.
2166</t>
2167</section>
2168
2169<section title="From" anchor="header.from">
2170  <iref primary="true" item="From header" x:for-anchor=""/>
2171  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
2172  <x:anchor-alias value="From"/>
2173  <x:anchor-alias value="From-v"/>
2174  <x:anchor-alias value="mailbox"/>
2175<t>
2176   The "From" request-header field, if given, &SHOULD; contain an Internet
2177   e-mail address for the human user who controls the requesting user
2178   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
2179   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
2180</t>
2181<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
2182  <x:ref>From</x:ref>    = "From" ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
2183  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
2184 
2185  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2186</artwork></figure>
2187<t>
2188   An example is:
2189</t>
2190<figure><artwork type="example">
2191  From: webmaster@example.org
2192</artwork></figure>
2193<t>
2194   This header field &MAY; be used for logging purposes and as a means for
2195   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2196   be used as an insecure form of access protection. The interpretation
2197   of this field is that the request is being performed on behalf of the
2198   person given, who accepts responsibility for the method performed. In
2199   particular, robot agents &SHOULD; include this header field so that the
2200   person responsible for running the robot can be contacted if problems
2201   occur on the receiving end.
2202</t>
2203<t>
2204   The Internet e-mail address in this field &MAY; be separate from the
2205   Internet host which issued the request. For example, when a request
2206   is passed through a proxy the original issuer's address &SHOULD; be
2207   used.
2208</t>
2209<t>
2210   The client &SHOULD-NOT;  send the From header field without the user's
2211   approval, as it might conflict with the user's privacy interests or
2212   their site's security policy. It is strongly recommended that the
2213   user be able to disable, enable, and modify the value of this field
2214   at any time prior to a request.
2215</t>
2216</section>
2217
2218<section title="Location" anchor="header.location">
2219  <iref primary="true" item="Location header" x:for-anchor=""/>
2220  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
2221  <x:anchor-alias value="Location"/>
2222  <x:anchor-alias value="Location-v"/>
2223<t>
2224   The "Location" response-header field is used to identify a newly created
2225   resource, or to redirect the recipient to a different location for
2226   completion of the request.
2227</t>
2228<t>
2229   For 201 (Created) responses, the Location is the URI of the new resource
2230   which was created by the request. For 3xx responses, the location &SHOULD;
2231   indicate the server's preferred URI for automatic redirection to the
2232   resource.
2233</t>
2234<t>
2235   The field value consists of a single URI-reference. When it has the form
2236   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2237   the final value is computed by resolving it against the effective request
2238   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
2239</t>
2240<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
2241  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
2242  <x:ref>Location-v</x:ref>     = <x:ref>URI-reference</x:ref>
2243</artwork></figure>
2244<figure>
2245<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical WSP below, it's necessary this way for xml2rfc-->
2246<artwork type="example">
2247  Location: http://www.example.org/pub/WWW/People.html#tim
2248</artwork></figure><figure><artwork type="example">  Location: /index.html
2249</artwork></figure>
2250<t>
2251   There are circumstances in which a fragment identifier in a Location URI
2252   would not be appropriate:
2253   <list style="symbols">
2254      <t>With a 201 Created response, because in this usage the Location header
2255      field specifies the URI for the entire created resource.</t>
2256      <t>With 305 Use Proxy.</t>
2257   </list>
2258</t>
2259<x:note>
2260  <t>
2261    <x:h>Note:</x:h> This specification does not define precedence rules
2262    for the case where the original URI, as navigated to by the user
2263    agent, and the Location header field value both contain fragment
2264    identifiers. Thus be aware that including fragment identifiers might
2265    inconvenience anyone relying on the semantics of the original URI's
2266    fragment identifier.
2267  </t>
2268</x:note>
2269<x:note>
2270  <t>
2271    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2272    from Location in that the Content-Location identifies the most specific
2273    resource corresponding to the enclosed representation.
2274    It is therefore possible for a response to contain header fields for
2275    both Location and Content-Location.
2276  </t>
2277</x:note>
2278</section>
2279
2280<section title="Max-Forwards" anchor="header.max-forwards">
2281  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
2282  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
2283  <x:anchor-alias value="Max-Forwards"/>
2284  <x:anchor-alias value="Max-Forwards-v"/>
2285<t>
2286   The "Max-Forwards" request-header field provides a mechanism with the
2287   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2288   methods to limit the number of times that the request is forwarded by
2289   proxies or gateways. This can be useful when the client is attempting to
2290   trace a request which appears to be failing or looping in mid-chain.
2291</t>
2292<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
2293  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
2294  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
2295</artwork></figure>
2296<t>
2297   The Max-Forwards value is a decimal integer indicating the remaining
2298   number of times this request message can be forwarded.
2299</t>
2300<t>
2301   Each proxy or gateway recipient of a TRACE or OPTIONS request
2302   containing a Max-Forwards header field &MUST; check and update its
2303   value prior to forwarding the request. If the received value is zero
2304   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2305   respond as the final recipient. If the received Max-Forwards value is
2306   greater than zero, then the forwarded message &MUST; contain an updated
2307   Max-Forwards field with a value decremented by one (1).
2308</t>
2309<t>
2310   The Max-Forwards header field &MAY; be ignored for all other methods.
2311</t>
2312</section>
2313
2314<section title="Referer" anchor="header.referer">
2315  <iref primary="true" item="Referer header" x:for-anchor=""/>
2316  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
2317  <x:anchor-alias value="Referer"/>
2318  <x:anchor-alias value="Referer-v"/>
2319<t>
2320   The "Referer" [sic] request-header field allows the client to specify the
2321   URI of the resource from which the effective request URI was obtained (the
2322   "referrer", although the header field is misspelled.).
2323</t>
2324<t>
2325   The Referer header field allows servers to generate lists of back-links to
2326   resources for interest, logging, optimized caching, etc. It also allows
2327   obsolete or mistyped links to be traced for maintenance. Some servers use
2328   Referer as a means of controlling where they allow links from (so-called
2329   "deep linking"), but legitimate requests do not always
2330   contain a Referer header field.
2331</t>
2332<t>
2333   If the effective request URI was obtained from a source that does not have its own
2334   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
2335   sent with the value "about:blank", or not be sent at all. Note that this
2336   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2337</t>
2338<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
2339  <x:ref>Referer</x:ref>        = "Referer" ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
2340  <x:ref>Referer-v</x:ref>      = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2341</artwork></figure>
2342<t>
2343   Example:
2344</t>
2345<figure><artwork type="example">
2346  Referer: http://www.example.org/hypertext/Overview.html
2347</artwork></figure>
2348<t>
2349   If the field value is a relative URI, it &SHOULD; be interpreted
2350   relative to the effective request URI. The URI &MUST-NOT; include a fragment. See
2351   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2352</t>
2353</section>
2354
2355<section title="Retry-After" anchor="header.retry-after">
2356  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2357  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
2358  <x:anchor-alias value="Retry-After"/>
2359  <x:anchor-alias value="Retry-After-v"/>
2360<t>
2361   The response-header "Retry-After" field can be used with a 503 (Service
2362   Unavailable) response to indicate how long the service is expected to
2363   be unavailable to the requesting client. This field &MAY; also be used
2364   with any 3xx (Redirection) response to indicate the minimum time the
2365   user-agent is asked wait before issuing the redirected request.
2366</t>
2367<t>
2368   The value of this field can be either an HTTP-date or an integer number
2369   of seconds (in decimal) after the time of the response.
2370</t>
2371<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
2372  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
2373  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2374</artwork></figure>
2375<t anchor="rule.delta-seconds">
2376  <x:anchor-alias value="delta-seconds"/>
2377   Time spans are non-negative decimal integers, representing time in
2378   seconds.
2379</t>
2380<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2381  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2382</artwork></figure>
2383<t>
2384   Two examples of its use are
2385</t>
2386<figure><artwork type="example">
2387  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2388  Retry-After: 120
2389</artwork></figure>
2390<t>
2391   In the latter example, the delay is 2 minutes.
2392</t>
2393</section>
2394
2395<section title="Server" anchor="header.server">
2396  <iref primary="true" item="Server header" x:for-anchor=""/>
2397  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
2398  <x:anchor-alias value="Server"/>
2399  <x:anchor-alias value="Server-v"/>
2400<t>
2401   The "Server" response-header field contains information about the
2402   software used by the origin server to handle the request.
2403</t>
2404<t>
2405   The field can contain multiple product tokens (&product-tokens;) and
2406   comments (&header-fields;) identifying the server and any significant
2407   subproducts. The product tokens are listed in order of their significance
2408   for identifying the application.
2409</t>
2410<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
2411  <x:ref>Server</x:ref>         = "Server" ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
2412  <x:ref>Server-v</x:ref>       = <x:ref>product</x:ref>
2413                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2414</artwork></figure>
2415<t>
2416   Example:
2417</t>
2418<figure><artwork type="example">
2419  Server: CERN/3.0 libwww/2.17
2420</artwork></figure>
2421<t>
2422   If the response is being forwarded through a proxy, the proxy
2423   application &MUST-NOT; modify the Server response-header field. Instead, it
2424   &MUST; include a Via field (as described in &header-via;).
2425</t>
2426<x:note>
2427  <t>
2428    <x:h>Note:</x:h> Revealing the specific software version of the server might
2429    allow the server machine to become more vulnerable to attacks
2430    against software that is known to contain security holes. Server
2431    implementors are encouraged to make this field a configurable
2432    option.
2433  </t>
2434</x:note>
2435</section>
2436
2437<section title="User-Agent" anchor="header.user-agent">
2438  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2439  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
2440  <x:anchor-alias value="User-Agent"/>
2441  <x:anchor-alias value="User-Agent-v"/>
2442<t>
2443   The "User-Agent" request-header field contains information about the user
2444   agent originating the request. User agents &SHOULD; include this field with
2445   requests.
2446</t>
2447<t>
2448   Typically, it is used for statistical purposes, the tracing of protocol
2449   violations, and tailoring responses to avoid particular user agent
2450   limitations.
2451</t>
2452<t>
2453   The field can contain multiple product tokens (&product-tokens;)
2454   and comments (&header-fields;) identifying the agent and its
2455   significant subproducts. By convention, the product tokens are listed in
2456   order of their significance for identifying the application.
2457</t>
2458<t>
2459   Because this field is usually sent on every request a user agent makes,
2460   implementations are encouraged not to include needlessly fine-grained
2461   detail, and to limit (or even prohibit) the addition of subproducts by third
2462   parties. Overly long and detailed User-Agent field values make requests
2463   larger and can also be used to identify ("fingerprint") the user against
2464   their wishes.
2465</t>
2466<t>
2467   Likewise, implementations are encouraged not to use the product tokens of
2468   other implementations in order to declare compatibility with them, as this
2469   circumvents the purpose of the field. Finally, they are encouraged not to
2470   use comments to identify products; doing so makes the field value more
2471   difficult to parse.
2472</t>
2473<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
2474  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
2475  <x:ref>User-Agent-v</x:ref>   = <x:ref>product</x:ref>
2476                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2477</artwork></figure>
2478<t>
2479   Example:
2480</t>
2481<figure><artwork type="example">
2482  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2483</artwork></figure>
2484</section>
2485
2486</section>
2487
2488<section title="IANA Considerations" anchor="IANA.considerations">
2489
2490<section title="Method Registry" anchor="method.registration">
2491<t>
2492  The registration procedure for HTTP Methods is defined by
2493  <xref target="method.registry"/> of this document.
2494</t>
2495<t>
2496   The HTTP Method Registry shall be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2497   and be populated with the registrations below:
2498</t>
2499<?BEGININC p2-semantics.iana-methods ?>
2500<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2501<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2502   <ttcol>Method</ttcol>
2503   <ttcol>Safe</ttcol>
2504   <ttcol>Reference</ttcol>
2505   <c>CONNECT</c>
2506   <c>no</c>
2507   <c>
2508      <xref target="CONNECT"/>
2509   </c>
2510   <c>DELETE</c>
2511   <c>no</c>
2512   <c>
2513      <xref target="DELETE"/>
2514   </c>
2515   <c>GET</c>
2516   <c>yes</c>
2517   <c>
2518      <xref target="GET"/>
2519   </c>
2520   <c>HEAD</c>
2521   <c>yes</c>
2522   <c>
2523      <xref target="HEAD"/>
2524   </c>
2525   <c>OPTIONS</c>
2526   <c>yes</c>
2527   <c>
2528      <xref target="OPTIONS"/>
2529   </c>
2530   <c>POST</c>
2531   <c>no</c>
2532   <c>
2533      <xref target="POST"/>
2534   </c>
2535   <c>PUT</c>
2536   <c>no</c>
2537   <c>
2538      <xref target="PUT"/>
2539   </c>
2540   <c>TRACE</c>
2541   <c>yes</c>
2542   <c>
2543      <xref target="TRACE"/>
2544   </c>
2545</texttable>
2546<!--(END)-->
2547<?ENDINC p2-semantics.iana-methods ?>
2548</section>
2549
2550<section title="Status Code Registry" anchor="status.code.registration">
2551<t>
2552   The registration procedure for HTTP Status Codes -- previously defined
2553   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> -- is now defined
2554   by <xref target="status.code.registry"/> of this document.
2555</t>
2556<t>
2557   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2558   shall be updated with the registrations below:
2559</t>
2560<?BEGININC p2-semantics.iana-status-codes ?>
2561<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2562<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2563   <ttcol>Value</ttcol>
2564   <ttcol>Description</ttcol>
2565   <ttcol>Reference</ttcol>
2566   <c>100</c>
2567   <c>Continue</c>
2568   <c>
2569      <xref target="status.100"/>
2570   </c>
2571   <c>101</c>
2572   <c>Switching Protocols</c>
2573   <c>
2574      <xref target="status.101"/>
2575   </c>
2576   <c>200</c>
2577   <c>OK</c>
2578   <c>
2579      <xref target="status.200"/>
2580   </c>
2581   <c>201</c>
2582   <c>Created</c>
2583   <c>
2584      <xref target="status.201"/>
2585   </c>
2586   <c>202</c>
2587   <c>Accepted</c>
2588   <c>
2589      <xref target="status.202"/>
2590   </c>
2591   <c>203</c>
2592   <c>Non-Authoritative Information</c>
2593   <c>
2594      <xref target="status.203"/>
2595   </c>
2596   <c>204</c>
2597   <c>No Content</c>
2598   <c>
2599      <xref target="status.204"/>
2600   </c>
2601   <c>205</c>
2602   <c>Reset Content</c>
2603   <c>
2604      <xref target="status.205"/>
2605   </c>
2606   <c>300</c>
2607   <c>Multiple Choices</c>
2608   <c>
2609      <xref target="status.300"/>
2610   </c>
2611   <c>301</c>
2612   <c>Moved Permanently</c>
2613   <c>
2614      <xref target="status.301"/>
2615   </c>
2616   <c>302</c>
2617   <c>Found</c>
2618   <c>
2619      <xref target="status.302"/>
2620   </c>
2621   <c>303</c>
2622   <c>See Other</c>
2623   <c>
2624      <xref target="status.303"/>
2625   </c>
2626   <c>305</c>
2627   <c>Use Proxy</c>
2628   <c>
2629      <xref target="status.305"/>
2630   </c>
2631   <c>306</c>
2632   <c>(Unused)</c>
2633   <c>
2634      <xref target="status.306"/>
2635   </c>
2636   <c>307</c>
2637   <c>Temporary Redirect</c>
2638   <c>
2639      <xref target="status.307"/>
2640   </c>
2641   <c>400</c>
2642   <c>Bad Request</c>
2643   <c>
2644      <xref target="status.400"/>
2645   </c>
2646   <c>402</c>
2647   <c>Payment Required</c>
2648   <c>
2649      <xref target="status.402"/>
2650   </c>
2651   <c>403</c>
2652   <c>Forbidden</c>
2653   <c>
2654      <xref target="status.403"/>
2655   </c>
2656   <c>404</c>
2657   <c>Not Found</c>
2658   <c>
2659      <xref target="status.404"/>
2660   </c>
2661   <c>405</c>
2662   <c>Method Not Allowed</c>
2663   <c>
2664      <xref target="status.405"/>
2665   </c>
2666   <c>406</c>
2667   <c>Not Acceptable</c>
2668   <c>
2669      <xref target="status.406"/>
2670   </c>
2671   <c>407</c>
2672   <c>Proxy Authentication Required</c>
2673   <c>
2674      <xref target="status.407"/>
2675   </c>
2676   <c>408</c>
2677   <c>Request Timeout</c>
2678   <c>
2679      <xref target="status.408"/>
2680   </c>
2681   <c>409</c>
2682   <c>Conflict</c>
2683   <c>
2684      <xref target="status.409"/>
2685   </c>
2686   <c>410</c>
2687   <c>Gone</c>
2688   <c>
2689      <xref target="status.410"/>
2690   </c>
2691   <c>411</c>
2692   <c>Length Required</c>
2693   <c>
2694      <xref target="status.411"/>
2695   </c>
2696   <c>413</c>
2697   <c>Request Entity Too Large</c>
2698   <c>
2699      <xref target="status.413"/>
2700   </c>
2701   <c>414</c>
2702   <c>URI Too Long</c>
2703   <c>
2704      <xref target="status.414"/>
2705   </c>
2706   <c>415</c>
2707   <c>Unsupported Media Type</c>
2708   <c>
2709      <xref target="status.415"/>
2710   </c>
2711   <c>417</c>
2712   <c>Expectation Failed</c>
2713   <c>
2714      <xref target="status.417"/>
2715   </c>
2716   <c>426</c>
2717   <c>Upgrade Required</c>
2718   <c>
2719      <xref target="status.426"/>
2720   </c>
2721   <c>500</c>
2722   <c>Internal Server Error</c>
2723   <c>
2724      <xref target="status.500"/>
2725   </c>
2726   <c>501</c>
2727   <c>Not Implemented</c>
2728   <c>
2729      <xref target="status.501"/>
2730   </c>
2731   <c>502</c>
2732   <c>Bad Gateway</c>
2733   <c>
2734      <xref target="status.502"/>
2735   </c>
2736   <c>503</c>
2737   <c>Service Unavailable</c>
2738   <c>
2739      <xref target="status.503"/>
2740   </c>
2741   <c>504</c>
2742   <c>Gateway Timeout</c>
2743   <c>
2744      <xref target="status.504"/>
2745   </c>
2746   <c>505</c>
2747   <c>HTTP Version Not Supported</c>
2748   <c>
2749      <xref target="status.505"/>
2750   </c>
2751</texttable>
2752<!--(END)-->
2753<?ENDINC p2-semantics.iana-status-codes ?>
2754</section>
2755<section title="Header Field Registration" anchor="header.field.registration">
2756<t>
2757   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
2758   with the permanent registrations below (see <xref target="RFC3864"/>):
2759</t>
2760<?BEGININC p2-semantics.iana-headers ?>
2761<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2762<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2763   <ttcol>Header Field Name</ttcol>
2764   <ttcol>Protocol</ttcol>
2765   <ttcol>Status</ttcol>
2766   <ttcol>Reference</ttcol>
2767
2768   <c>Allow</c>
2769   <c>http</c>
2770   <c>standard</c>
2771   <c>
2772      <xref target="header.allow"/>
2773   </c>
2774   <c>Expect</c>
2775   <c>http</c>
2776   <c>standard</c>
2777   <c>
2778      <xref target="header.expect"/>
2779   </c>
2780   <c>From</c>
2781   <c>http</c>
2782   <c>standard</c>
2783   <c>
2784      <xref target="header.from"/>
2785   </c>
2786   <c>Location</c>
2787   <c>http</c>
2788   <c>standard</c>
2789   <c>
2790      <xref target="header.location"/>
2791   </c>
2792   <c>Max-Forwards</c>
2793   <c>http</c>
2794   <c>standard</c>
2795   <c>
2796      <xref target="header.max-forwards"/>
2797   </c>
2798   <c>Referer</c>
2799   <c>http</c>
2800   <c>standard</c>
2801   <c>
2802      <xref target="header.referer"/>
2803   </c>
2804   <c>Retry-After</c>
2805   <c>http</c>
2806   <c>standard</c>
2807   <c>
2808      <xref target="header.retry-after"/>
2809   </c>
2810   <c>Server</c>
2811   <c>http</c>
2812   <c>standard</c>
2813   <c>
2814      <xref target="header.server"/>
2815   </c>
2816   <c>User-Agent</c>
2817   <c>http</c>
2818   <c>standard</c>
2819   <c>
2820      <xref target="header.user-agent"/>
2821   </c>
2822</texttable>
2823<!--(END)-->
2824<?ENDINC p2-semantics.iana-headers ?>
2825<t>
2826   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2827</t>
2828</section>
2829</section>
2830
2831<section title="Security Considerations" anchor="security.considerations">
2832<t>
2833   This section is meant to inform application developers, information
2834   providers, and users of the security limitations in HTTP/1.1 as
2835   described by this document. The discussion does not include
2836   definitive solutions to the problems revealed, though it does make
2837   some suggestions for reducing security risks.
2838</t>
2839
2840<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2841<t>
2842   Like any generic data transfer protocol, HTTP cannot regulate the
2843   content of the data that is transferred, nor is there any a priori
2844   method of determining the sensitivity of any particular piece of
2845   information within the context of any given request. Therefore,
2846   applications &SHOULD; supply as much control over this information as
2847   possible to the provider of that information. Four header fields are
2848   worth special mention in this context: Server, Via, Referer and From.
2849</t>
2850<t>
2851   Revealing the specific software version of the server might allow the
2852   server machine to become more vulnerable to attacks against software
2853   that is known to contain security holes. Implementors &SHOULD; make the
2854   Server header field a configurable option.
2855</t>
2856<t>
2857   Proxies which serve as a portal through a network firewall &SHOULD;
2858   take special precautions regarding the transfer of header information
2859   that identifies the hosts behind the firewall. In particular, they
2860   &SHOULD; remove, or replace with sanitized versions, any Via fields
2861   generated behind the firewall.
2862</t>
2863<t>
2864   The Referer header field allows reading patterns to be studied and reverse
2865   links drawn. Although it can be very useful, its power can be abused
2866   if user details are not separated from the information contained in
2867   the Referer. Even when the personal information has been removed, the
2868   Referer header field might indicate a private document's URI whose
2869   publication would be inappropriate.
2870</t>
2871<t>
2872   The information sent in the From field might conflict with the user's
2873   privacy interests or their site's security policy, and hence it
2874   &SHOULD-NOT;  be transmitted without the user being able to disable,
2875   enable, and modify the contents of the field. The user &MUST; be able
2876   to set the contents of this field within a user preference or
2877   application defaults configuration.
2878</t>
2879<t>
2880   We suggest, though do not require, that a convenient toggle interface
2881   be provided for the user to enable or disable the sending of From and
2882   Referer information.
2883</t>
2884<t>
2885   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref
2886   target="header.server"/>) header fields can sometimes be used to determine
2887   that a specific client or server have a particular security hole which might
2888   be exploited. Unfortunately, this same information is often used for other
2889   valuable purposes for which HTTP currently has no better mechanism.
2890</t>
2891<t>
2892   Furthermore, the User-Agent header field may contain enough entropy to be
2893   used, possibly in conjunction with other material, to uniquely identify the
2894   user.
2895</t>
2896<t>
2897   Some methods, like TRACE (<xref target="TRACE"/>), expose information
2898   that was sent in request header fields within the body of their response.
2899   Clients &SHOULD; be careful with sensitive information, like Cookies,
2900   Authorization credentials and other header fields that might be used to
2901   collect data from the client.
2902</t> 
2903</section>
2904
2905<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2906<t>
2907   Because the source of a link might be private information or might
2908   reveal an otherwise private information source, it is strongly
2909   recommended that the user be able to select whether or not the
2910   Referer field is sent. For example, a browser client could have a
2911   toggle switch for browsing openly/anonymously, which would
2912   respectively enable/disable the sending of Referer and From
2913   information.
2914</t>
2915<t>
2916   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2917   HTTP request if the referring page was transferred with a secure
2918   protocol.
2919</t>
2920<t>
2921   Authors of services &SHOULD-NOT; use GET-based forms for the submission of
2922   sensitive data because that data will be placed in the request-target. Many
2923   existing servers, proxies, and user agents log or display the request-target
2924   in places where it might be visible to third parties. Such services can
2925   use POST-based form submission instead.
2926</t>
2927</section>
2928
2929<section title="Location Headers and Spoofing" anchor="location.spoofing">
2930<t>
2931   If a single server supports multiple organizations that do not trust
2932   one another, then it &MUST; check the values of Location and Content-Location
2933   header fields in responses that are generated under control of
2934   said organizations to make sure that they do not attempt to
2935   invalidate resources over which they have no authority.
2936</t>
2937</section>
2938
2939<section title="Security Considerations for CONNECT">
2940<t>
2941   Since tunneled data is opaque to the proxy, there are additional
2942   risks to tunneling to other well-known or reserved ports.
2943   A HTTP client CONNECTing to port 25 could relay spam
2944   via SMTP, for example. As such, proxies &SHOULD; restrict CONNECT
2945   access to a small number of known ports.
2946</t>
2947</section>
2948
2949</section>
2950
2951<section title="Acknowledgments" anchor="ack">
2952</section>
2953</middle>
2954<back>
2955
2956<references title="Normative References">
2957
2958<reference anchor="Part1">
2959  <front>
2960    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2961    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2962      <organization abbrev="Day Software">Day Software</organization>
2963      <address><email>fielding@gbiv.com</email></address>
2964    </author>
2965    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2966      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2967      <address><email>jg@freedesktop.org</email></address>
2968    </author>
2969    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2970      <organization abbrev="HP">Hewlett-Packard Company</organization>
2971      <address><email>JeffMogul@acm.org</email></address>
2972    </author>
2973    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2974      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2975      <address><email>henrikn@microsoft.com</email></address>
2976    </author>
2977    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2978      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2979      <address><email>LMM@acm.org</email></address>
2980    </author>
2981    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2982      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2983      <address><email>paulle@microsoft.com</email></address>
2984    </author>
2985    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2986      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2987      <address><email>timbl@w3.org</email></address>
2988    </author>
2989    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2990      <organization abbrev="W3C">World Wide Web Consortium</organization>
2991      <address><email>ylafon@w3.org</email></address>
2992    </author>
2993    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2994      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2995      <address><email>julian.reschke@greenbytes.de</email></address>
2996    </author>
2997    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2998  </front>
2999  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
3000  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
3001</reference>
3002
3003<reference anchor="Part3">
3004  <front>
3005    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
3006    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3007      <organization abbrev="Day Software">Day Software</organization>
3008      <address><email>fielding@gbiv.com</email></address>
3009    </author>
3010    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3011      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3012      <address><email>jg@freedesktop.org</email></address>
3013    </author>
3014    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3015      <organization abbrev="HP">Hewlett-Packard Company</organization>
3016      <address><email>JeffMogul@acm.org</email></address>
3017    </author>
3018    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3019      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3020      <address><email>henrikn@microsoft.com</email></address>
3021    </author>
3022    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3023      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
3024      <address><email>LMM@acm.org</email></address>
3025    </author>
3026    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3027      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3028      <address><email>paulle@microsoft.com</email></address>
3029    </author>
3030    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3031      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3032      <address><email>timbl@w3.org</email></address>
3033    </author>
3034    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3035      <organization abbrev="W3C">World Wide Web Consortium</organization>
3036      <address><email>ylafon@w3.org</email></address>
3037    </author>
3038    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3039      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3040      <address><email>julian.reschke@greenbytes.de</email></address>
3041    </author>
3042    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3043  </front>
3044  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
3045  <x:source href="p3-payload.xml" basename="p3-payload"/>
3046</reference>
3047
3048<reference anchor="Part4">
3049  <front>
3050    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
3051    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3052      <organization abbrev="Day Software">Day Software</organization>
3053      <address><email>fielding@gbiv.com</email></address>
3054    </author>
3055    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3056      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3057      <address><email>jg@freedesktop.org</email></address>
3058    </author>
3059    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3060      <organization abbrev="HP">Hewlett-Packard Company</organization>
3061      <address><email>JeffMogul@acm.org</email></address>
3062    </author>
3063    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3064      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3065      <address><email>henrikn@microsoft.com</email></address>
3066    </author>
3067    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3068      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
3069      <address><email>LMM@acm.org</email></address>
3070    </author>
3071    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3072      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3073      <address><email>paulle@microsoft.com</email></address>
3074    </author>
3075    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3076      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3077      <address><email>timbl@w3.org</email></address>
3078    </author>
3079    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3080      <organization abbrev="W3C">World Wide Web Consortium</organization>
3081      <address><email>ylafon@w3.org</email></address>
3082    </author>
3083    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3084      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3085      <address><email>julian.reschke@greenbytes.de</email></address>
3086    </author>
3087    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3088  </front>
3089  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
3090  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
3091</reference>
3092
3093<reference anchor="Part5">
3094  <front>
3095    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
3096    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3097      <organization abbrev="Day Software">Day Software</organization>
3098      <address><email>fielding@gbiv.com</email></address>
3099    </author>
3100    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3101      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3102      <address><email>jg@freedesktop.org</email></address>
3103    </author>
3104    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3105      <organization abbrev="HP">Hewlett-Packard Company</organization>
3106      <address><email>JeffMogul@acm.org</email></address>
3107    </author>
3108    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3109      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3110      <address><email>henrikn@microsoft.com</email></address>
3111    </author>
3112    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3113      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
3114      <address><email>LMM@acm.org</email></address>
3115    </author>
3116    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3117      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3118      <address><email>paulle@microsoft.com</email></address>
3119    </author>
3120    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3121      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3122      <address><email>timbl@w3.org</email></address>
3123    </author>
3124    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3125      <organization abbrev="W3C">World Wide Web Consortium</organization>
3126      <address><email>ylafon@w3.org</email></address>
3127    </author>
3128    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3129      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3130      <address><email>julian.reschke@greenbytes.de</email></address>
3131    </author>
3132    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3133  </front>
3134  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
3135  <x:source href="p5-range.xml" basename="p5-range"/>
3136</reference>
3137
3138<reference anchor="Part6">
3139  <front>
3140    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
3141    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3142      <organization abbrev="Day Software">Day Software</organization>
3143      <address><email>fielding@gbiv.com</email></address>
3144    </author>
3145    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3146      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3147      <address><email>jg@freedesktop.org</email></address>
3148    </author>
3149    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3150      <organization abbrev="HP">Hewlett-Packard Company</organization>
3151      <address><email>JeffMogul@acm.org</email></address>
3152    </author>
3153    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3154      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3155      <address><email>henrikn@microsoft.com</email></address>
3156    </author>
3157    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3158      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
3159      <address><email>LMM@acm.org</email></address>
3160    </author>
3161    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3162      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3163      <address><email>paulle@microsoft.com</email></address>
3164    </author>
3165    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3166      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3167      <address><email>timbl@w3.org</email></address>
3168    </author>
3169    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3170      <organization abbrev="W3C">World Wide Web Consortium</organization>
3171      <address><email>ylafon@w3.org</email></address>
3172    </author>
3173    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
3174      <address><email>mnot@mnot.net</email></address>
3175    </author>
3176    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3177      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3178      <address><email>julian.reschke@greenbytes.de</email></address>
3179    </author>
3180    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3181  </front>
3182  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
3183  <x:source href="p6-cache.xml" basename="p6-cache"/>
3184</reference>
3185
3186<reference anchor="Part7">
3187  <front>
3188    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
3189    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
3190      <organization abbrev="Day Software">Day Software</organization>
3191      <address><email>fielding@gbiv.com</email></address>
3192    </author>
3193    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3194      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3195      <address><email>jg@freedesktop.org</email></address>
3196    </author>
3197    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3198      <organization abbrev="HP">Hewlett-Packard Company</organization>
3199      <address><email>JeffMogul@acm.org</email></address>
3200    </author>
3201    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3202      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3203      <address><email>henrikn@microsoft.com</email></address>
3204    </author>
3205    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3206      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
3207      <address><email>LMM@acm.org</email></address>
3208    </author>
3209    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3210      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3211      <address><email>paulle@microsoft.com</email></address>
3212    </author>
3213    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3214      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3215      <address><email>timbl@w3.org</email></address>
3216    </author>
3217    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3218      <organization abbrev="W3C">World Wide Web Consortium</organization>
3219      <address><email>ylafon@w3.org</email></address>
3220    </author>
3221    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3222      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3223      <address><email>julian.reschke@greenbytes.de</email></address>
3224    </author>
3225    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3226  </front>
3227  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3228  <x:source href="p7-auth.xml" basename="p7-auth"/>
3229</reference>
3230
3231<reference anchor="RFC2119">
3232  <front>
3233    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3234    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3235      <organization>Harvard University</organization>
3236      <address><email>sob@harvard.edu</email></address>
3237    </author>
3238    <date month="March" year="1997"/>
3239  </front>
3240  <seriesInfo name="BCP" value="14"/>
3241  <seriesInfo name="RFC" value="2119"/>
3242</reference>
3243
3244<reference anchor="RFC3986">
3245 <front>
3246  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3247  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3248    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3249    <address>
3250       <email>timbl@w3.org</email>
3251       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3252    </address>
3253  </author>
3254  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3255    <organization abbrev="Day Software">Day Software</organization>
3256    <address>
3257      <email>fielding@gbiv.com</email>
3258      <uri>http://roy.gbiv.com/</uri>
3259    </address>
3260  </author>
3261  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3262    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3263    <address>
3264      <email>LMM@acm.org</email>
3265      <uri>http://larry.masinter.net/</uri>
3266    </address>
3267  </author>
3268  <date month='January' year='2005'></date>
3269 </front>
3270 <seriesInfo name="STD" value="66"/>
3271 <seriesInfo name="RFC" value="3986"/>
3272</reference>
3273
3274<reference anchor="RFC5234">
3275  <front>
3276    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3277    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3278      <organization>Brandenburg InternetWorking</organization>
3279      <address>
3280        <email>dcrocker@bbiw.net</email>
3281      </address> 
3282    </author>
3283    <author initials="P." surname="Overell" fullname="Paul Overell">
3284      <organization>THUS plc.</organization>
3285      <address>
3286        <email>paul.overell@thus.net</email>
3287      </address>
3288    </author>
3289    <date month="January" year="2008"/>
3290  </front>
3291  <seriesInfo name="STD" value="68"/>
3292  <seriesInfo name="RFC" value="5234"/>
3293</reference>
3294
3295</references>
3296
3297<references title="Informative References">
3298
3299<reference anchor="RFC1945">
3300  <front>
3301    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3302    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3303      <organization>MIT, Laboratory for Computer Science</organization>
3304      <address><email>timbl@w3.org</email></address>
3305    </author>
3306    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3307      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3308      <address><email>fielding@ics.uci.edu</email></address>
3309    </author>
3310    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3311      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3312      <address><email>frystyk@w3.org</email></address>
3313    </author>
3314    <date month="May" year="1996"/>
3315  </front>
3316  <seriesInfo name="RFC" value="1945"/>
3317</reference>
3318
3319<reference anchor="RFC2068">
3320  <front>
3321    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3322    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3323      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3324      <address><email>fielding@ics.uci.edu</email></address>
3325    </author>
3326    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3327      <organization>MIT Laboratory for Computer Science</organization>
3328      <address><email>jg@w3.org</email></address>
3329    </author>
3330    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3331      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3332      <address><email>mogul@wrl.dec.com</email></address>
3333    </author>
3334    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3335      <organization>MIT Laboratory for Computer Science</organization>
3336      <address><email>frystyk@w3.org</email></address>
3337    </author>
3338    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3339      <organization>MIT Laboratory for Computer Science</organization>
3340      <address><email>timbl@w3.org</email></address>
3341    </author>
3342    <date month="January" year="1997"/>
3343  </front>
3344  <seriesInfo name="RFC" value="2068"/>
3345</reference>
3346
3347<reference anchor="RFC2616">
3348  <front>
3349    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3350    <author initials="R." surname="Fielding" fullname="R. Fielding">
3351      <organization>University of California, Irvine</organization>
3352      <address><email>fielding@ics.uci.edu</email></address>
3353    </author>
3354    <author initials="J." surname="Gettys" fullname="J. Gettys">
3355      <organization>W3C</organization>
3356      <address><email>jg@w3.org</email></address>
3357    </author>
3358    <author initials="J." surname="Mogul" fullname="J. Mogul">
3359      <organization>Compaq Computer Corporation</organization>
3360      <address><email>mogul@wrl.dec.com</email></address>
3361    </author>
3362    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3363      <organization>MIT Laboratory for Computer Science</organization>
3364      <address><email>frystyk@w3.org</email></address>
3365    </author>
3366    <author initials="L." surname="Masinter" fullname="L. Masinter">
3367      <organization>Xerox Corporation</organization>
3368      <address><email>masinter@parc.xerox.com</email></address>
3369    </author>
3370    <author initials="P." surname="Leach" fullname="P. Leach">
3371      <organization>Microsoft Corporation</organization>
3372      <address><email>paulle@microsoft.com</email></address>
3373    </author>
3374    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3375      <organization>W3C</organization>
3376      <address><email>timbl@w3.org</email></address>
3377    </author>
3378    <date month="June" year="1999"/>
3379  </front>
3380  <seriesInfo name="RFC" value="2616"/>
3381</reference>
3382
3383<reference anchor='RFC2817'>
3384  <front>
3385    <title>Upgrading to TLS Within HTTP/1.1</title>
3386    <author initials='R.' surname='Khare' fullname='R. Khare'>
3387      <organization>4K Associates / UC Irvine</organization>
3388      <address><email>rohit@4K-associates.com</email></address>
3389    </author>
3390    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3391      <organization>Agranat Systems, Inc.</organization>
3392      <address><email>lawrence@agranat.com</email></address>
3393    </author>
3394    <date year='2000' month='May' />
3395  </front>
3396  <seriesInfo name='RFC' value='2817' />
3397</reference>
3398
3399<reference anchor='RFC3864'>
3400  <front>
3401    <title>Registration Procedures for Message Header Fields</title>
3402    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3403      <organization>Nine by Nine</organization>
3404      <address><email>GK-IETF@ninebynine.org</email></address>
3405    </author>
3406    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3407      <organization>BEA Systems</organization>
3408      <address><email>mnot@pobox.com</email></address>
3409    </author>
3410    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3411      <organization>HP Labs</organization>
3412      <address><email>JeffMogul@acm.org</email></address>
3413    </author>
3414    <date year='2004' month='September' />
3415  </front>
3416  <seriesInfo name='BCP' value='90' />
3417  <seriesInfo name='RFC' value='3864' />
3418</reference>
3419
3420<reference anchor='RFC5226'>
3421  <front>
3422    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3423    <author initials='T.' surname='Narten' fullname='T. Narten'>
3424      <organization>IBM</organization>
3425      <address><email>narten@us.ibm.com</email></address>
3426    </author>
3427    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3428      <organization>Google</organization>
3429      <address><email>Harald@Alvestrand.no</email></address>
3430    </author>
3431    <date year='2008' month='May' />
3432  </front>
3433  <seriesInfo name='BCP' value='26' />
3434  <seriesInfo name='RFC' value='5226' />
3435</reference>
3436
3437<reference anchor="RFC5322">
3438  <front>
3439    <title>Internet Message Format</title>
3440    <author initials="P." surname="Resnick" fullname="P. Resnick">
3441      <organization>Qualcomm Incorporated</organization>
3442    </author>
3443    <date year="2008" month="October"/>
3444  </front> 
3445  <seriesInfo name="RFC" value="5322"/>
3446</reference>
3447
3448</references>
3449
3450<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3451<t>
3452  This document takes over the Status Code Registry, previously defined
3453  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3454  (<xref target="status.code.registry"/>)
3455</t>
3456<t>
3457  Clarify definition of POST.
3458  (<xref target="POST"/>)
3459</t>
3460<t>
3461  Take over definition of CONNECT method from <xref target="RFC2817"/>.
3462  (<xref target="CONNECT"/>)
3463</t>
3464<t>
3465  Failed to consider that there are
3466  many other request methods that are safe to automatically redirect,
3467  and further that the user agent is able to make that determination
3468  based on the request method semantics.
3469  (Sections <xref format="counter" target="status.301"/>,
3470  <xref format="counter" target="status.302"/> and
3471  <xref format="counter" target="status.307"/>)
3472</t>
3473<t>
3474  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3475  It used to indicate that the target resource must be accessed through the
3476  proxy given by the Location field. The Location field gave the URI of the
3477  proxy. The recipient was expected to repeat this single request via the proxy.
3478  (<xref target="status.305"/>)
3479</t>
3480<t>
3481  Define status 426 (Upgrade Required) (this was incorporated from
3482  <xref target="RFC2817"/>).
3483  (<xref target="status.426"/>)
3484</t>
3485<t>
3486  Reclassify "Allow" as response header field, removing the option to
3487  specify it in a PUT request.
3488  Relax the server requirement on the contents of the Allow header field and
3489  remove requirement on clients to always trust the header field value.
3490  (<xref target="header.allow"/>)
3491</t>
3492<t>
3493  Correct syntax of Location header field to allow URI references (including
3494  relative references and fragments), as referred symbol "absoluteURI" wasn't
3495  what was expected, and add some clarifications as to when use of fragments
3496  would not be appropriate.
3497  (<xref target="header.location"/>)
3498</t>
3499<t>
3500  Restrict Max-Forwards header field to OPTIONS and TRACE (previously,
3501  extension methods could have used it as well).
3502  (<xref target="header.max-forwards"/>)
3503</t>
3504<t>
3505  Allow Referer field value of "about:blank" as alternative to not specifying it.
3506  (<xref target="header.referer"/>)
3507</t>
3508<t>
3509  In the description of the Server header field, the Via field
3510  was described as a SHOULD. The requirement was and is stated
3511  correctly in the description of the Via header field in &header-via;.
3512  (<xref target="header.server"/>)
3513</t>
3514</section>
3515
3516<?BEGININC p2-semantics.abnf-appendix ?>
3517<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3518<figure>
3519<artwork type="abnf" name="p2-semantics.parsed-abnf">
3520<x:ref>Accept</x:ref> = &lt;Accept, defined in [Part3], Section 6.1&gt;
3521<x:ref>Accept-Charset</x:ref> = &lt;Accept-Charset, defined in [Part3], Section 6.2&gt;
3522<x:ref>Accept-Encoding</x:ref> = &lt;Accept-Encoding, defined in [Part3], Section 6.3&gt;
3523<x:ref>Accept-Language</x:ref> = &lt;Accept-Language, defined in [Part3], Section 6.4&gt;
3524<x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in [Part5], Section 5.1&gt;
3525<x:ref>Age</x:ref> = &lt;Age, defined in [Part6], Section 3.1&gt;
3526<x:ref>Allow</x:ref> = "Allow:" OWS Allow-v
3527<x:ref>Allow-v</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3528<x:ref>Authorization</x:ref> = &lt;Authorization, defined in [Part7], Section 4.1&gt;
3529
3530<x:ref>ETag</x:ref> = &lt;ETag, defined in [Part4], Section 6.1&gt;
3531<x:ref>Expect</x:ref> = "Expect:" OWS Expect-v
3532<x:ref>Expect-v</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3533
3534<x:ref>From</x:ref> = "From:" OWS From-v
3535<x:ref>From-v</x:ref> = mailbox
3536
3537<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 6.1&gt;
3538<x:ref>Host</x:ref> = &lt;Host, defined in [Part1], Section 2.6&gt;
3539
3540<x:ref>If-Match</x:ref> = &lt;If-Match, defined in [Part4], Section 6.2&gt;
3541If-Modified-Since =
3542 &lt;If-Modified-Since, defined in [Part4], Section 6.3&gt;
3543<x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in [Part4], Section 6.4&gt;
3544<x:ref>If-Range</x:ref> = &lt;If-Range, defined in [Part5], Section 5.3&gt;
3545If-Unmodified-Since =
3546 &lt;If-Unmodified-Since, defined in [Part4], Section 6.5&gt;
3547
3548<x:ref>Location</x:ref> = "Location:" OWS Location-v
3549<x:ref>Location-v</x:ref> = URI-reference
3550
3551<x:ref>Max-Forwards</x:ref> = "Max-Forwards:" OWS Max-Forwards-v
3552<x:ref>Max-Forwards-v</x:ref> = 1*DIGIT
3553<x:ref>Method</x:ref> = %x4F.50.54.49.4F.4E.53 ; OPTIONS
3554 / %x47.45.54 ; GET
3555 / %x48.45.41.44 ; HEAD
3556 / %x50.4F.53.54 ; POST
3557 / %x50.55.54 ; PUT
3558 / %x44.45.4C.45.54.45 ; DELETE
3559 / %x54.52.41.43.45 ; TRACE
3560 / %x43.4F.4E.4E.45.43.54 ; CONNECT
3561 / extension-method
3562
3563<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
3564
3565Proxy-Authenticate =
3566 &lt;Proxy-Authenticate, defined in [Part7], Section 4.2&gt;
3567Proxy-Authorization =
3568 &lt;Proxy-Authorization, defined in [Part7], Section 4.3&gt;
3569
3570<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3571<x:ref>Range</x:ref> = &lt;Range, defined in [Part5], Section 5.4&gt;
3572<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
3573<x:ref>Referer</x:ref> = "Referer:" OWS Referer-v
3574<x:ref>Referer-v</x:ref> = absolute-URI / partial-URI
3575<x:ref>Retry-After</x:ref> = "Retry-After:" OWS Retry-After-v
3576<x:ref>Retry-After-v</x:ref> = HTTP-date / delta-seconds
3577
3578<x:ref>Server</x:ref> = "Server:" OWS Server-v
3579<x:ref>Server-v</x:ref> = product *( RWS ( product / comment ) )
3580<x:ref>Status-Code</x:ref> = "100" / "101" / "200" / "201" / "202" / "203" / "204" /
3581 "205" / "206" / "300" / "301" / "302" / "303" / "304" / "305" /
3582 "307" / "400" / "401" / "402" / "403" / "404" / "405" / "406" /
3583 "407" / "408" / "409" / "410" / "411" / "412" / "413" / "414" /
3584 "415" / "416" / "417" / "426" / "500" / "501" / "502" / "503" /
3585 "504" / "505" / extension-code
3586
3587<x:ref>TE</x:ref> = &lt;TE, defined in [Part1], Section 9.5&gt;
3588
3589<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.6&gt;
3590<x:ref>User-Agent</x:ref> = "User-Agent:" OWS User-Agent-v
3591<x:ref>User-Agent-v</x:ref> = product *( RWS ( product / comment ) )
3592
3593<x:ref>Vary</x:ref> = &lt;Vary, defined in [Part6], Section 3.5&gt;
3594
3595WWW-Authenticate =
3596 &lt;WWW-Authenticate, defined in [Part7], Section 4.4&gt;
3597
3598<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.6&gt;
3599
3600<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2&gt;
3601
3602<x:ref>delta-seconds</x:ref> = 1*DIGIT
3603
3604<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
3605<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
3606<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
3607 *expect-params ]
3608<x:ref>extension-code</x:ref> = 3DIGIT
3609<x:ref>extension-method</x:ref> = token
3610
3611<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
3612
3613<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
3614
3615<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.6&gt;
3616<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 6.3&gt;
3617
3618<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
3619
3620<x:ref>request-header</x:ref> = Accept / Accept-Charset / Accept-Encoding /
3621 Accept-Language / Authorization / Expect / From / Host / If-Match /
3622 If-Modified-Since / If-None-Match / If-Range / If-Unmodified-Since /
3623 Max-Forwards / Proxy-Authorization / Range / Referer / TE /
3624 User-Agent
3625<x:ref>response-header</x:ref> = Accept-Ranges / Age / Allow / ETag / Location /
3626 Proxy-Authenticate / Retry-After / Server / Vary / WWW-Authenticate
3627
3628<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
3629</artwork>
3630</figure>
3631<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
3632; Reason-Phrase defined but not used
3633; Status-Code defined but not used
3634; request-header defined but not used
3635; response-header defined but not used
3636</artwork></figure></section>
3637<?ENDINC p2-semantics.abnf-appendix ?>
3638
3639<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3640
3641<section title="Since RFC 2616">
3642<t>
3643  Extracted relevant partitions from <xref target="RFC2616"/>.
3644</t>
3645</section>
3646
3647<section title="Since draft-ietf-httpbis-p2-semantics-00">
3648<t>
3649  Closed issues:
3650  <list style="symbols"> 
3651    <t>
3652      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3653      "Via is a MUST"
3654      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3655    </t>
3656    <t>
3657      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3658      "Fragments allowed in Location"
3659      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3660    </t>
3661    <t>
3662      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3663      "Safe Methods vs Redirection"
3664      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3665    </t>
3666    <t>
3667      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3668      "Revise description of the POST method"
3669      (<eref target="http://purl.org/NET/http-errata#post"/>)
3670    </t>
3671    <t>
3672      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3673      "Normative and Informative references"
3674    </t>
3675    <t>
3676      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3677      "RFC2606 Compliance"
3678    </t>
3679    <t>
3680      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3681      "Informative references"
3682    </t>
3683    <t>
3684      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3685      "Redundant cross-references"
3686    </t>
3687  </list>
3688</t>
3689<t>
3690  Other changes:
3691  <list style="symbols"> 
3692    <t>
3693      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3694    </t>
3695  </list>
3696</t>
3697</section>
3698
3699<section title="Since draft-ietf-httpbis-p2-semantics-01">
3700<t>
3701  Closed issues:
3702  <list style="symbols"> 
3703    <t>
3704      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3705      "PUT side effects"
3706    </t>
3707    <t>
3708      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3709      "Duplicate Host header requirements"
3710    </t>
3711  </list>
3712</t>
3713<t>
3714  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3715  <list style="symbols"> 
3716    <t>
3717      Move "Product Tokens" section (back) into Part 1, as "token" is used
3718      in the definition of the Upgrade header field.
3719    </t>
3720    <t>
3721      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3722    </t>
3723    <t>
3724      Copy definition of delta-seconds from Part6 instead of referencing it.
3725    </t>
3726  </list>
3727</t>
3728</section>
3729
3730<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3731<t>
3732  Closed issues:
3733  <list style="symbols"> 
3734    <t>
3735      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3736      "Requiring Allow in 405 responses"
3737    </t>
3738    <t>
3739      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3740      "Status Code Registry"
3741    </t>
3742    <t>
3743      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3744      "Redirection vs. Location"
3745    </t>
3746    <t>
3747      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3748      "Cacheability of 303 response"
3749    </t>
3750    <t>
3751      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3752      "305 Use Proxy"
3753    </t>
3754    <t>
3755      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3756      "Classification for Allow header"
3757    </t>
3758    <t>
3759      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3760      "PUT - 'store under' vs 'store at'"
3761    </t>
3762  </list>
3763</t>
3764<t>
3765  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3766  <list style="symbols"> 
3767    <t>
3768      Reference RFC 3984, and update header field registrations for headers defined
3769      in this document.
3770    </t>
3771  </list>
3772</t>
3773<t>
3774  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3775  <list style="symbols"> 
3776    <t>
3777      Replace string literals when the string really is case-sensitive (method).
3778    </t>
3779  </list>
3780</t>
3781</section>
3782
3783<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3784<t>
3785  Closed issues:
3786  <list style="symbols"> 
3787    <t>
3788      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
3789      "OPTIONS request bodies"
3790    </t>
3791    <t>
3792      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
3793      "Description of CONNECT should refer to RFC2817"
3794    </t>
3795    <t>
3796      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
3797      "Location Content-Location reference request/response mixup"
3798    </t>
3799  </list>
3800</t>
3801<t>
3802  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
3803  <list style="symbols"> 
3804    <t>
3805      Added initial proposal for registration process, plus initial
3806      content (non-HTTP/1.1 methods to be added by a separate specification).
3807    </t>
3808  </list>
3809</t>
3810</section>
3811
3812<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3813<t>
3814  Closed issues:
3815  <list style="symbols"> 
3816    <t>
3817      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3818      "Content-*"
3819    </t>
3820    <t>
3821      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3822      "RFC 2822 is updated by RFC 5322"
3823    </t>
3824  </list>
3825</t>
3826<t>
3827  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3828  <list style="symbols"> 
3829    <t>
3830      Use "/" instead of "|" for alternatives.
3831    </t>
3832    <t>
3833      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3834      whitespace ("OWS") and required whitespace ("RWS").
3835    </t>
3836    <t>
3837      Rewrite ABNFs to spell out whitespace rules, factor out
3838      header field value format definitions.
3839    </t>
3840  </list>
3841</t>
3842</section>
3843
3844<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3845<t>
3846  Closed issues:
3847  <list style="symbols"> 
3848    <t>
3849      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
3850      "Reason-Phrase BNF"
3851    </t>
3852  </list>
3853</t>
3854<t>
3855  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3856  <list style="symbols"> 
3857    <t>
3858      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3859    </t>
3860  </list>
3861</t>
3862</section>
3863
3864<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
3865<t>
3866  Closed issues:
3867  <list style="symbols"> 
3868    <t>
3869      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
3870      "Clarify when Referer is sent"
3871    </t>
3872    <t>
3873      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
3874      "status codes vs methods"
3875    </t>
3876    <t>
3877      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
3878      "Do not require "updates" relation for specs that register status codes or method names"
3879    </t>
3880  </list>
3881</t>
3882</section>
3883
3884<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
3885<t>
3886  Closed issues:
3887  <list style="symbols"> 
3888    <t>
3889      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
3890      "Idempotency"
3891    </t>
3892    <t>
3893      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
3894      "TRACE security considerations"
3895    </t>
3896    <t>
3897      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
3898      "Clarify rules for determining what entities a response carries"
3899    </t>
3900    <t>
3901      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
3902      "update note citing RFC 1945 and 2068"
3903    </t>
3904    <t>
3905      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
3906      "update note about redirect limit"
3907    </t>
3908    <t>
3909      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
3910      "Location header ABNF should use 'URI'"
3911    </t>
3912    <t>
3913      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
3914      "fragments in Location vs status 303"
3915    </t>
3916    <t>
3917      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
3918      "move IANA registrations for optional status codes"
3919    </t>
3920  </list>
3921</t>
3922<t>
3923  Partly resolved issues:
3924  <list style="symbols"> 
3925    <t>
3926      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
3927      "Are OPTIONS and TRACE safe?"
3928    </t>
3929  </list>
3930</t>
3931</section>
3932
3933<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
3934<t>
3935  Closed issues:
3936  <list style="symbols"> 
3937    <t>
3938      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3939      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
3940      status codes when fixing this previously)
3941    </t>
3942  </list>
3943</t>
3944</section>
3945
3946<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
3947<t>
3948  Closed issues:
3949  <list style="symbols"> 
3950    <t>
3951      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
3952      "Fragment combination / precedence during redirects"
3953    </t>
3954  </list>
3955</t>
3956<t>
3957  Partly resolved issues:
3958  <list style="symbols"> 
3959    <t>
3960      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
3961      "Location header payload handling"
3962    </t>
3963    <t>
3964      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
3965      "Term for the requested resource's URI"
3966    </t>
3967  </list>
3968</t>
3969</section>
3970
3971<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
3972<t>
3973  Closed issues:
3974  <list style="symbols"> 
3975    <t>
3976      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
3977      "Clarify 'Requested Variant'"
3978    </t>
3979    <t>
3980      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
3981      "Clarify entity / representation / variant terminology"
3982    </t>
3983    <t>
3984      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/139"/>:
3985      "Methods and Caching"
3986    </t>
3987    <t>
3988      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/190"/>:
3989      "OPTIONS vs Max-Forwards"
3990    </t>
3991    <t>
3992      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/199"/>:
3993      "Status codes and caching"
3994    </t>
3995    <t>
3996      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
3997      "consider removing the 'changes from 2068' sections"
3998    </t>
3999  </list>
4000</t>
4001</section>
4002
4003<section title="Since draft-ietf-httpbis-p2-semantics-11" anchor="changes.since.11">
4004<t>
4005  Closed issues:
4006  <list style="symbols"> 
4007    <t>
4008      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/229"/>:
4009      "Considerations for new status codes"
4010    </t>
4011    <t>
4012      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/230"/>:
4013      "Considerations for new methods"
4014    </t>
4015    <t>
4016      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/232"/>:
4017      "User-Agent guidelines" (relating to the 'User-Agent' header field)
4018    </t>
4019  </list>
4020</t>
4021</section>
4022
4023<section title="Since draft-ietf-httpbis-p2-semantics-12" anchor="changes.since.12">
4024<t>
4025  Closed issues:
4026  <list style="symbols"> 
4027    <t>
4028      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
4029      "Fragment combination / precedence during redirects" (added warning
4030      about having a fragid on the redirect may cause inconvenience in
4031      some cases)
4032    </t>
4033    <t>
4034      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/88"/>:
4035      "205 Bodies"
4036    </t>
4037    <t>
4038      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/203"/>:
4039      "Max-Forwards vs extension methods"
4040    </t>
4041    <t>
4042      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/226"/>:
4043      "proxies not supporting certain methods"
4044    </t>
4045    <t>
4046      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/239"/>:
4047      "Migrate CONNECT from RFC2817 to p2"
4048    </t>
4049    <t>
4050      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/240"/>:
4051      "Migrate Upgrade details from RFC2817"
4052    </t>
4053  </list>
4054</t>
4055</section>
4056
4057</section>
4058
4059</back>
4060</rfc>
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