source: draft-ietf-httpbis/latest/p2-semantics.xml @ 1003

Last change on this file since 1003 was 1003, checked in by julian.reschke@…, 9 years ago

reorder BCP/STD/RFC numbers in references

  • Property svn:eol-style set to native
File size: 160.1 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 "September">
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 header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
36  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
37  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
38  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
39  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
40  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
41  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
42  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
43  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
44  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
45  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
46  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
47  <!ENTITY header-fields              "<xref target='Part1' x:rel='#header.fields' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
48  <!ENTITY header-host                "<xref target='Part1' x:rel='#header.host' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
49  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
50  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
51  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
52  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
53  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
54  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
55  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
56  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
57  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
58  <!ENTITY header-upgrade             "<xref target='Part1' x:rel='#header.upgrade' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
59  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.te' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
60  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
61  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
62  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
63  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
64  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
65  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
66  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='#internet.media.type.message.http' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
67  <!ENTITY status-206                 "<xref target='Part5' x:rel='#status.206' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
68  <!ENTITY status-304                 "<xref target='Part4' x:rel='#status.304' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
69  <!ENTITY status-401                 "<xref target='Part7' x:rel='#status.401' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
70  <!ENTITY status-407                 "<xref target='Part7' x:rel='#status.407' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
71  <!ENTITY status-412                 "<xref target='Part4' x:rel='#status.412' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
72  <!ENTITY status-416                 "<xref target='Part5' x:rel='#status.416' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
73  <!ENTITY p4-status-codes            "<xref target='Part4' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
74  <!ENTITY p5-status-codes            "<xref target='Part5' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
75  <!ENTITY p7-status-codes            "<xref target='Part7' x:rel='#status.code.definitions' xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
76  <!ENTITY p6-heuristic               "<xref target='Part6' x:rel='#heuristic.freshness'
77xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
78  <!ENTITY p6-explicit               "<xref target='Part6' x:rel='#calculating.freshness.lifetime'
79xmlns:x='http://purl.org/net/xml2rfc/ext'/>">
80]>
81<?rfc toc="yes" ?>
82<?rfc symrefs="yes" ?>
83<?rfc sortrefs="yes" ?>
84<?rfc compact="yes"?>
85<?rfc subcompact="no" ?>
86<?rfc linkmailto="no" ?>
87<?rfc editing="no" ?>
88<?rfc comments="yes"?>
89<?rfc inline="yes"?>
90<?rfc rfcedstyle="yes"?>
91<?rfc-ext allow-markup-in-artwork="yes" ?>
92<?rfc-ext include-references-in-index="yes" ?>
93<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
94     ipr="pre5378Trust200902" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
95     xmlns:x='http://purl.org/net/xml2rfc/ext'
96     xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
97<front>
98
99  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
100
101  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
102    <organization abbrev="Day Software">Day Software</organization>
103    <address>
104      <postal>
105        <street>23 Corporate Plaza DR, Suite 280</street>
106        <city>Newport Beach</city>
107        <region>CA</region>
108        <code>92660</code>
109        <country>USA</country>
110      </postal>
111      <phone>+1-949-706-5300</phone>
112      <facsimile>+1-949-706-5305</facsimile>
113      <email>fielding@gbiv.com</email>
114      <uri>http://roy.gbiv.com/</uri>
115    </address>
116  </author>
117
118  <author initials="J." surname="Gettys" fullname="Jim Gettys">
119    <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
120    <address>
121      <postal>
122        <street>21 Oak Knoll Road</street>
123        <city>Carlisle</city>
124        <region>MA</region>
125        <code>01741</code>
126        <country>USA</country>
127      </postal>
128      <email>jg@freedesktop.org</email>
129      <uri>http://gettys.wordpress.com/</uri>
130    </address>
131  </author>
132 
133  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
134    <organization abbrev="HP">Hewlett-Packard Company</organization>
135    <address>
136      <postal>
137        <street>HP Labs, Large Scale Systems Group</street>
138        <street>1501 Page Mill Road, MS 1177</street>
139        <city>Palo Alto</city>
140        <region>CA</region>
141        <code>94304</code>
142        <country>USA</country>
143      </postal>
144      <email>JeffMogul@acm.org</email>
145    </address>
146  </author>
147
148  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
149    <organization abbrev="Microsoft">Microsoft Corporation</organization>
150    <address>
151      <postal>
152        <street>1 Microsoft Way</street>
153        <city>Redmond</city>
154        <region>WA</region>
155        <code>98052</code>
156        <country>USA</country>
157      </postal>
158      <email>henrikn@microsoft.com</email>
159    </address>
160  </author>
161
162  <author initials="L." surname="Masinter" fullname="Larry Masinter">
163    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
164    <address>
165      <postal>
166        <street>345 Park Ave</street>
167        <city>San Jose</city>
168        <region>CA</region>
169        <code>95110</code>
170        <country>USA</country>
171      </postal>
172      <email>LMM@acm.org</email>
173      <uri>http://larry.masinter.net/</uri>
174    </address>
175  </author>
176 
177  <author initials="P." surname="Leach" fullname="Paul J. Leach">
178    <organization abbrev="Microsoft">Microsoft Corporation</organization>
179    <address>
180      <postal>
181        <street>1 Microsoft Way</street>
182        <city>Redmond</city>
183        <region>WA</region>
184        <code>98052</code>
185      </postal>
186      <email>paulle@microsoft.com</email>
187    </address>
188  </author>
189   
190  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
191    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
192    <address>
193      <postal>
194        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
195        <street>The Stata Center, Building 32</street>
196        <street>32 Vassar Street</street>
197        <city>Cambridge</city>
198        <region>MA</region>
199        <code>02139</code>
200        <country>USA</country>
201      </postal>
202      <email>timbl@w3.org</email>
203      <uri>http://www.w3.org/People/Berners-Lee/</uri>
204    </address>
205  </author>
206
207  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
208    <organization abbrev="W3C">World Wide Web Consortium</organization>
209    <address>
210      <postal>
211        <street>W3C / ERCIM</street>
212        <street>2004, rte des Lucioles</street>
213        <city>Sophia-Antipolis</city>
214        <region>AM</region>
215        <code>06902</code>
216        <country>France</country>
217      </postal>
218      <email>ylafon@w3.org</email>
219      <uri>http://www.raubacapeu.net/people/yves/</uri>
220    </address>
221  </author>
222
223  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
224    <organization abbrev="greenbytes">greenbytes GmbH</organization>
225    <address>
226      <postal>
227        <street>Hafenweg 16</street>
228        <city>Muenster</city><region>NW</region><code>48155</code>
229        <country>Germany</country>
230      </postal>
231      <phone>+49 251 2807760</phone>
232      <facsimile>+49 251 2807761</facsimile>
233      <email>julian.reschke@greenbytes.de</email>
234      <uri>http://greenbytes.de/tech/webdav/</uri>
235    </address>
236  </author>
237
238  <date month="&ID-MONTH;" year="&ID-YEAR;"/>
239  <workgroup>HTTPbis Working Group</workgroup>
240
241<abstract>
242<t>
243   The Hypertext Transfer Protocol (HTTP) is an application-level
244   protocol for distributed, collaborative, hypermedia information
245   systems. HTTP has been in use by the World Wide Web global information
246   initiative since 1990. This document is Part 2 of the seven-part specification
247   that defines the protocol referred to as "HTTP/1.1" and, taken together,
248   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
249   as expressed by request methods, request-header fields, response status codes,
250   and response-header fields.
251</t>
252</abstract>
253
254<note title="Editorial Note (To be removed by RFC Editor)">
255  <t>
256    Discussion of this draft should take place on the HTTPBIS working group
257    mailing list (ietf-http-wg@w3.org). The current issues list is
258    at <eref target="http://tools.ietf.org/wg/httpbis/trac/report/3"/>
259    and related documents (including fancy diffs) can be found at
260    <eref target="http://tools.ietf.org/wg/httpbis/"/>.
261  </t>
262  <t>
263    The changes in this draft are summarized in <xref target="changes.since.11"/>.
264  </t>
265</note>
266</front>
267<middle>
268<section title="Introduction" anchor="introduction">
269<t>
270   This document defines HTTP/1.1 request and response semantics.  Each HTTP
271   message, as defined in &messaging;, is in the form of either a request or
272   a response.  An HTTP server listens on a connection for HTTP requests and
273   responds to each request, in the order received on that connection, with
274   one or more HTTP response messages.  This document defines the commonly
275   agreed upon semantics of the HTTP uniform interface, the intentions defined
276   by each request method, and the various response messages that might be
277   expected as a result of applying that method to the target resource.
278</t>
279<t>
280   This document is currently disorganized in order to minimize the changes
281   between drafts and enable reviewers to see the smaller errata changes.
282   A future draft will reorganize the sections to better reflect the content.
283   In particular, the sections will be ordered according to the typical
284   processing of an HTTP request message (after message parsing): resource
285   mapping, general header fields, methods, request modifiers, response
286   status, and resource metadata.  The current mess reflects how widely
287   dispersed these topics and associated requirements had become in
288   <xref target="RFC2616"/>.
289</t>
290
291<section title="Requirements" anchor="intro.requirements">
292<t>
293   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
294   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
295   document are to be interpreted as described in <xref target="RFC2119"/>.
296</t>
297<t>
298   An implementation is not compliant if it fails to satisfy one or more
299   of the "MUST" or "REQUIRED" level requirements for the protocols it
300   implements. An implementation that satisfies all the "MUST" or "REQUIRED"
301   level and all the "SHOULD" level requirements for its protocols is said
302   to be "unconditionally compliant"; one that satisfies all the "MUST"
303   level requirements but not all the "SHOULD" level requirements for its
304   protocols is said to be "conditionally compliant".
305</t>
306</section>
307
308<section title="Syntax Notation" anchor="notation">
309  <x:anchor-alias value="CR"/>
310  <x:anchor-alias value="DIGIT"/>
311  <x:anchor-alias value="LF"/>
312  <x:anchor-alias value="VCHAR"/>
313  <x:anchor-alias value="WSP"/>
314<t>
315  This specification uses the ABNF syntax defined in &notation; (which
316  extends the syntax defined in <xref target="RFC5234"/> with a list rule).
317  <xref target="collected.abnf"/> shows the collected ABNF, with the list
318  rule expanded.
319</t>
320<t>
321  The following core rules are included by
322  reference, as defined in <xref target="RFC5234" x:fmt="," x:sec="B.1"/>:
323  ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls),
324  DIGIT (decimal 0-9), DQUOTE (double quote),
325  HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed),
326  OCTET (any 8-bit sequence of data), SP (space),
327  VCHAR (any visible USASCII character),
328  and WSP (whitespace).
329</t>
330
331<section title="Core Rules" anchor="core.rules">
332  <x:anchor-alias value="obs-text"/>
333  <x:anchor-alias value="quoted-string"/>
334  <x:anchor-alias value="token"/>
335  <x:anchor-alias value="OWS"/>
336  <x:anchor-alias value="RWS"/>
337<t>
338  The core rules below are defined in &basic-rules;:
339</t>
340<figure><artwork type="abnf2616">
341  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
342  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
343  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
344  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
345  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
346</artwork></figure>
347</section>
348
349<section title="ABNF Rules defined in other Parts of the Specification" anchor="abnf.dependencies">
350  <x:anchor-alias value="absolute-URI"/>
351  <x:anchor-alias value="Accept"/>
352  <x:anchor-alias value="Accept-Charset"/>
353  <x:anchor-alias value="Accept-Encoding"/>
354  <x:anchor-alias value="Accept-Language"/>
355  <x:anchor-alias value="Accept-Ranges"/>
356  <x:anchor-alias value="Age"/>
357  <x:anchor-alias value="Authorization"/>
358  <x:anchor-alias value="comment"/>
359  <x:anchor-alias value="ETag"/>
360  <x:anchor-alias value="Host"/>
361  <x:anchor-alias value="HTTP-date"/>
362  <x:anchor-alias value="If-Match"/>
363  <x:anchor-alias value="If-Modified-Since"/>
364  <x:anchor-alias value="If-None-Match"/>
365  <x:anchor-alias value="If-Range"/>
366  <x:anchor-alias value="If-Unmodified-Since"/>
367  <x:anchor-alias value="partial-URI"/>
368  <x:anchor-alias value="product"/>
369  <x:anchor-alias value="Proxy-Authenticate"/>
370  <x:anchor-alias value="Proxy-Authorization"/>
371  <x:anchor-alias value="Range"/>
372  <x:anchor-alias value="TE"/>
373  <x:anchor-alias value="URI-reference"/>
374  <x:anchor-alias value="Vary"/>
375  <x:anchor-alias value="WWW-Authenticate"/>
376<t>
377  The ABNF rules below are defined in other parts:
378</t>
379<figure><!--Part1--><artwork type="abnf2616">
380  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
381  <x:ref>comment</x:ref>       = &lt;comment, defined in &header-fields;&gt;
382  <x:ref>Host</x:ref>          = &lt;Host, defined in &uri;&gt;
383  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
384  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
385  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
386  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
387  <x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in &uri;&gt;
388</artwork></figure>
389<figure><!--Part3--><artwork type="abnf2616">
390  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
391  <x:ref>Accept-Charset</x:ref> =
392             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
393  <x:ref>Accept-Encoding</x:ref> =
394             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
395  <x:ref>Accept-Language</x:ref> =
396             &lt;Accept-Language, defined in &header-accept-language;&gt;
397</artwork></figure>
398<figure><!--Part4--><artwork type="abnf2616">
399  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
400  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
401  <x:ref>If-Modified-Since</x:ref> =
402             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
403  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
404  <x:ref>If-Unmodified-Since</x:ref> =
405             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
406</artwork></figure>
407<figure><!--Part5--><artwork type="abnf2616">
408  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
409  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
410  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
411</artwork></figure>
412<figure><!--Part6--><artwork type="abnf2616">
413  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
414  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
415</artwork><!--Part7--></figure>
416<figure><artwork type="abnf2616">
417  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
418  <x:ref>Proxy-Authenticate</x:ref> =
419             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
420  <x:ref>Proxy-Authorization</x:ref> =
421             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
422  <x:ref>WWW-Authenticate</x:ref> =
423             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
424</artwork></figure>
425</section>
426</section>
427</section>
428
429<section title="Method" anchor="method">
430  <x:anchor-alias value="Method"/>
431  <x:anchor-alias value="extension-method"/>
432<t>
433   The Method token indicates the method to be performed on the target
434   resource (&effective-request-uri;). The method is case-sensitive.
435</t>
436<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
437  <x:ref>Method</x:ref>         = <x:abnf-char-sequence>"OPTIONS"</x:abnf-char-sequence>   ; "OPTIONS", <xref target="OPTIONS"/>
438                 / <x:abnf-char-sequence>"GET"</x:abnf-char-sequence>               ; "GET", <xref target="GET"/>
439                 / <x:abnf-char-sequence>"HEAD"</x:abnf-char-sequence>            ; "HEAD", <xref target="HEAD"/>
440                 / <x:abnf-char-sequence>"POST"</x:abnf-char-sequence>            ; "POST", <xref target="POST"/>
441                 / <x:abnf-char-sequence>"PUT"</x:abnf-char-sequence>               ; "PUT", <xref target="PUT"/>
442                 / <x:abnf-char-sequence>"DELETE"</x:abnf-char-sequence>      ; "DELETE", <xref target="DELETE"/>
443                 / <x:abnf-char-sequence>"TRACE"</x:abnf-char-sequence>         ; "TRACE", <xref target="TRACE"/>
444                 / <x:abnf-char-sequence>"CONNECT"</x:abnf-char-sequence>   ; "CONNECT", <xref target="CONNECT"/>
445                 / <x:ref>extension-method</x:ref>
446  <x:ref>extension-method</x:ref> = <x:ref>token</x:ref>
447</artwork></figure>
448<t>
449   The list of methods allowed by a resource can be specified in an
450   Allow header field (<xref target="header.allow"/>). The status code of the response
451   always notifies the client whether a method is currently allowed on a
452   resource, since the set of allowed methods can change dynamically. An
453   origin server &SHOULD; respond with the status code 405 (Method Not Allowed)
454   if the method is known by the origin server but not allowed for the
455   resource, and 501 (Not Implemented) if the method is
456   unrecognized or not implemented by the origin server. The methods GET
457   and HEAD &MUST; be supported by all general-purpose servers. All other
458   methods are &OPTIONAL;; however, if the above methods are implemented,
459   they &MUST; be implemented with the same semantics as those specified
460   in <xref target="method.definitions"/>.
461</t>
462
463<section title="Method Registry" anchor="method.registry">
464<t>
465  The HTTP Method Registry defines the name space for the Method token in the
466  Request line of an HTTP request.
467</t>
468<t>
469  Registrations &MUST; include the following fields:
470  <list style="symbols">
471    <t>Method Name (see <xref target="method"/>)</t>
472    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
473    <t>Pointer to specification text</t>
474  </list>
475</t>
476<t>
477  Values to be added to this name space are subject to IETF review
478  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
479</t>
480<t>
481  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-methods"/>.
482</t>
483</section>
484</section>
485
486<section title="Request Header Fields" anchor="request.header.fields">
487  <x:anchor-alias value="request-header"/>
488<t>
489   The request-header fields allow the client to pass additional
490   information about the request, and about the client itself, to the
491   server. These fields act as request modifiers, with semantics
492   equivalent to the parameters on a programming language method
493   invocation.
494</t>
495<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
496  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
497                 / <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
498                 / <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
499                 / <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
500                 / <x:ref>Authorization</x:ref>            ; &header-authorization;
501                 / <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
502                 / <x:ref>From</x:ref>                     ; <xref target="header.from"/>
503                 / <x:ref>Host</x:ref>                     ; &header-host;
504                 / <x:ref>If-Match</x:ref>                 ; &header-if-match;
505                 / <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
506                 / <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
507                 / <x:ref>If-Range</x:ref>                 ; &header-if-range;
508                 / <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
509                 / <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
510                 / <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
511                 / <x:ref>Range</x:ref>                    ; &header-range;
512                 / <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
513                 / <x:ref>TE</x:ref>                       ; &header-te;
514                 / <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
515</artwork></figure>
516<t>
517   Request-header field names can be extended reliably only in
518   combination with a change in the protocol version. However, new or
519   experimental header fields &MAY; be given the semantics of request-header
520   fields if all parties in the communication recognize them to
521   be request-header fields.
522</t>
523</section>
524
525<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
526  <x:anchor-alias value="Reason-Phrase"/>
527  <x:anchor-alias value="Status-Code"/>
528  <x:anchor-alias value="extension-code"/>
529<t>
530   The Status-Code element is a 3-digit integer result code of the
531   attempt to understand and satisfy the request. The status codes listed
532   below are defined in <xref target="status.codes"/>, &p4-status-codes;,
533   &p5-status-codes;, and &p7-status-codes;.
534</t>
535<t>
536   The Reason-Phrase is intended to give a short
537   textual description of the Status-Code. The Status-Code is intended
538   for use by automata and the Reason-Phrase is intended for the human
539   user. The client is not required to examine or display the Reason-Phrase.
540</t>
541<t> 
542   The individual values of the numeric status codes defined for
543   HTTP/1.1, and an example set of corresponding Reason-Phrase values, are
544   presented below. The reason phrases listed here are only
545   recommendations -- they &MAY; be replaced by local equivalents without
546   affecting the protocol.
547</t>
548<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"/>
549  <x:ref>Status-Code</x:ref> =
550       "100"  ; <xref target="status.100"/>: Continue
551     / "101"  ; <xref target="status.101"/>: Switching Protocols
552     / "200"  ; <xref target="status.200"/>: OK
553     / "201"  ; <xref target="status.201"/>: Created
554     / "202"  ; <xref target="status.202"/>: Accepted
555     / "203"  ; <xref target="status.203"/>: Non-Authoritative Information
556     / "204"  ; <xref target="status.204"/>: No Content
557     / "205"  ; <xref target="status.205"/>: Reset Content
558     / "206"  ; &status-206;: Partial Content
559     / "300"  ; <xref target="status.300"/>: Multiple Choices
560     / "301"  ; <xref target="status.301"/>: Moved Permanently
561     / "302"  ; <xref target="status.302"/>: Found
562     / "303"  ; <xref target="status.303"/>: See Other
563     / "304"  ; &status-304;: Not Modified
564     / "305"  ; <xref target="status.305"/>: Use Proxy
565     / "307"  ; <xref target="status.307"/>: Temporary Redirect
566     / "400"  ; <xref target="status.400"/>: Bad Request
567     / "401"  ; &status-401;: Unauthorized
568     / "402"  ; <xref target="status.402"/>: Payment Required
569     / "403"  ; <xref target="status.403"/>: Forbidden
570     / "404"  ; <xref target="status.404"/>: Not Found
571     / "405"  ; <xref target="status.405"/>: Method Not Allowed
572     / "406"  ; <xref target="status.406"/>: Not Acceptable
573     / "407"  ; &status-407;: Proxy Authentication Required
574     / "408"  ; <xref target="status.408"/>: Request Time-out
575     / "409"  ; <xref target="status.409"/>: Conflict
576     / "410"  ; <xref target="status.410"/>: Gone
577     / "411"  ; <xref target="status.411"/>: Length Required
578     / "412"  ; &status-412;: Precondition Failed
579     / "413"  ; <xref target="status.413"/>: Request Entity Too Large
580     / "414"  ; <xref target="status.414"/>: URI Too Long
581     / "415"  ; <xref target="status.415"/>: Unsupported Media Type
582     / "416"  ; &status-416;: Requested range not satisfiable
583     / "417"  ; <xref target="status.417"/>: Expectation Failed
584     / "500"  ; <xref target="status.500"/>: Internal Server Error
585     / "501"  ; <xref target="status.501"/>: Not Implemented
586     / "502"  ; <xref target="status.502"/>: Bad Gateway
587     / "503"  ; <xref target="status.503"/>: Service Unavailable
588     / "504"  ; <xref target="status.504"/>: Gateway Time-out
589     / "505"  ; <xref target="status.505"/>: HTTP Version not supported
590     / <x:ref>extension-code</x:ref>
591
592  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
593  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
594</artwork></figure>
595<t>
596   HTTP status codes are extensible. HTTP applications are not required
597   to understand the meaning of all registered status codes, though such
598   understanding is obviously desirable. However, applications &MUST;
599   understand the class of any status code, as indicated by the first
600   digit, and treat any unrecognized response as being equivalent to the
601   x00 status code of that class, with the exception that an
602   unrecognized response &MUST-NOT; be cached. For example, if an
603   unrecognized status code of 431 is received by the client, it can
604   safely assume that there was something wrong with its request and
605   treat the response as if it had received a 400 status code. In such
606   cases, user agents &SHOULD; present to the user the representation enclosed
607   with the response, since that representation is likely to include human-readable
608   information which will explain the unusual status.
609</t>
610
611<section title="Status Code Registry" anchor="status.code.registry">
612<t>
613  The HTTP Status Code Registry defines the name space for the Status-Code
614  token in the Status-Line of an HTTP response.
615</t>
616<t>
617  Values to be added to this name space are subject to IETF review
618  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).
619</t>
620<t>
621  The registry itself is maintained at <eref target="http://www.iana.org/assignments/http-status-codes"/>.
622</t>
623</section>
624
625</section>
626
627<section title="Response Header Fields" anchor="response.header.fields">
628  <x:anchor-alias value="response-header"/>
629<t>
630   The response-header fields allow the server to pass additional
631   information about the response which cannot be placed in the Status-Line.
632   These header fields give information about the server and about
633   further access to the target resource (&effective-request-uri;).
634</t>
635<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
636  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
637                  / <x:ref>Age</x:ref>                     ; &header-age;
638                  / <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
639                  / <x:ref>ETag</x:ref>                    ; &header-etag;
640                  / <x:ref>Location</x:ref>                ; <xref target="header.location"/>
641                  / <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
642                  / <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
643                  / <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
644                  / <x:ref>Vary</x:ref>                    ; &header-vary;
645                  / <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
646</artwork></figure>
647<t>
648   Response-header field names can be extended reliably only in
649   combination with a change in the protocol version. However, new or
650   experimental header fields &MAY; be given the semantics of response-header
651   fields if all parties in the communication recognize them to
652   be response-header fields.
653</t>
654</section>
655
656<section title="Representation" anchor="representation">
657<t>
658   Request and Response messages &MAY; transfer a representation if not otherwise
659   restricted by the request method or response status code. A representation
660   consists of metadata (representation header fields) and data (representation
661   body).  When a complete or partial representation is enclosed in an HTTP message,
662   it is referred to as the payload of the message. HTTP representations
663   are defined in &payload;.
664</t>
665<t>
666   A representation body is only present in a message when a message-body is
667   present, as described in &message-body;. The representation body is obtained
668   from the message-body by decoding any Transfer-Encoding that might
669   have been applied to ensure safe and proper transfer of the message.
670</t>
671
672<section title="Identifying the Resource Associated with a Representation" anchor="identifying.response.associated.with.representation">
673<t>
674   It is sometimes necessary to determine an identifier for the resource
675   associated with a representation.
676</t>
677<t>
678   An HTTP request representation, when present, is always associated with an
679   anonymous (i.e., unidentified) resource.
680</t>
681<t>
682   In the common case, an HTTP response is a representation of the target
683   resource (see &effective-request-uri;). However, this is not always the
684   case. To determine the URI of the resource a response is associated with,
685   the following rules are used (with the first applicable one being selected):
686</t>
687<t><list style="numbers">
688   <t>If the response status code is 200 or 203 and the request method was GET,
689   the response payload is a representation of the target resource.</t>
690   <t>If the response status code is 204, 206, or 304 and the request method was GET
691   or HEAD, the response payload is a partial representation of the target
692   (see &combining-responses;).</t>
693   <t>If the response has a Content-Location header field, and that URI is the same
694   as the effective request URI, the response payload is a representation of the
695   target resource.</t>
696   <t>If the response has a Content-Location header field, and that URI is not the
697   same as the effective request URI, then the response asserts that its
698   payload is a representation of the resource identified by the
699   Content-Location URI. However, such an assertion cannot be trusted unless
700   it can be verified by other means (not defined by HTTP).</t>
701   <t>Otherwise, the response is a representation of an anonymous (i.e.,
702   unidentified) resource.</t>
703</list></t>
704<t>
705  <cref anchor="TODO-req-uri">
706   The comparison function is going to have to be defined somewhere,
707   because we already need to compare URIs for things like cache invalidation.</cref>
708</t>
709</section>
710
711</section>
712
713
714<section title="Method Definitions" anchor="method.definitions">
715<t>
716   The set of common methods for HTTP/1.1 is defined below. Although
717   this set can be expanded, additional methods cannot be assumed to
718   share the same semantics for separately extended clients and servers.
719</t>
720
721<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
722
723<section title="Safe Methods" anchor="safe.methods">
724<iref item="Safe Methods" primary="true"/>
725<t>
726   Implementors need to be aware that the software represents the user in
727   their interactions over the Internet, and need to allow
728   the user to be aware of any actions they take which might have an
729   unexpected significance to themselves or others.
730</t>
731<t>
732   In particular, the convention has been established that the GET, HEAD,
733   OPTIONS, and TRACE methods &SHOULD-NOT; have the significance of taking an action
734   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
735   This allows user agents to represent other methods, such as POST, PUT
736   and DELETE, in a special way, so that the user is made aware of the
737   fact that a possibly unsafe action is being requested.
738</t>
739<t>
740   Naturally, it is not possible to ensure that the server does not
741   generate side-effects as a result of performing a GET request; in
742   fact, some dynamic resources consider that a feature. The important
743   distinction here is that the user did not request the side-effects,
744   so therefore cannot be held accountable for them.
745</t>
746</section>
747
748<section title="Idempotent Methods" anchor="idempotent.methods">
749<iref item="Idempotent Methods" primary="true"/>
750<t>
751   Methods can also have the property of "idempotence" in that, aside
752   from error or expiration issues, the intended effect of multiple
753   identical requests is the same as for a single request.
754   The methods PUT, DELETE, and all safe methods are idempotent.
755   It is important to note that idempotence refers only to changes
756   requested by the client: a server is free to change its state due
757   to multiple requests for the purpose of tracking those requests,
758   versioning of results, etc.
759</t>
760</section>
761</section>
762
763<section title="OPTIONS" anchor="OPTIONS">
764  <rdf:Description>
765    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
766  </rdf:Description>
767  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
768  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
769<t>
770   The OPTIONS method represents a request for information about the
771   communication options available on the request/response chain
772   identified by the effective request URI. This method allows the client to
773   determine the options and/or requirements associated with a resource,
774   or the capabilities of a server, without implying a resource action
775   or initiating a resource retrieval.
776</t>
777<t>
778   Responses to this method are not cacheable.
779</t>
780<t>
781   If the OPTIONS request includes a message-body (as indicated by the
782   presence of Content-Length or Transfer-Encoding), then the media type
783   &MUST; be indicated by a Content-Type field. Although this
784   specification does not define any use for such a body, future
785   extensions to HTTP might use the OPTIONS body to make more detailed
786   queries on the server.
787</t>
788<t>
789   If the request-target is an asterisk ("*"), the OPTIONS request is
790   intended to apply to the server in general rather than to a specific
791   resource. Since a server's communication options typically depend on
792   the resource, the "*" request is only useful as a "ping" or "no-op"
793   type of method; it does nothing beyond allowing the client to test
794   the capabilities of the server. For example, this can be used to test
795   a proxy for HTTP/1.1 compliance (or lack thereof).
796</t>
797<t>
798   If the request-target is not an asterisk, the OPTIONS request applies
799   only to the options that are available when communicating with that
800   resource.
801</t>
802<t>
803   A 200 response &SHOULD; include any header fields that indicate
804   optional features implemented by the server and applicable to that
805   resource (e.g., Allow), possibly including extensions not defined by
806   this specification. The response body, if any, &SHOULD; also include
807   information about the communication options. The format for such a
808   body is not defined by this specification, but might be defined by
809   future extensions to HTTP. Content negotiation &MAY; be used to select
810   the appropriate response format. If no response body is included, the
811   response &MUST; include a Content-Length field with a field-value of
812   "0".
813</t>
814<t>
815   The Max-Forwards request-header field &MAY; be used to target a
816   specific proxy in the request chain (see <xref target="header.max-forwards"/>).
817   If no Max-Forwards field is present in the request, then the forwarded
818   request &MUST-NOT; include a Max-Forwards field.
819</t>
820</section>
821
822<section title="GET" anchor="GET">
823  <rdf:Description>
824    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
825  </rdf:Description>
826  <iref primary="true" item="GET method" x:for-anchor=""/>
827  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
828<t>
829   The GET method means retrieve whatever information (in the form of a
830   representation) currently corresponds to the target resource.
831</t>
832<t>   
833   If the target resource is a data-producing process, it is the
834   produced data which shall be returned as the representation in the response and not
835   the source text of the process, unless that text happens to be the output of
836   the process.
837</t>
838<t>
839   The semantics of the GET method change to a "conditional GET" if the
840   request message includes an If-Modified-Since, If-Unmodified-Since,
841   If-Match, If-None-Match, or If-Range header field. A conditional GET
842   method requests that the representation be transferred only under the
843   circumstances described by the conditional header field(s). The
844   conditional GET method is intended to reduce unnecessary network
845   usage by allowing cached representations to be refreshed without requiring
846   multiple requests or transferring data already held by the client.
847</t>
848<t>
849   The semantics of the GET method change to a "partial GET" if the
850   request message includes a Range header field. A partial GET requests
851   that only part of the representation be transferred, as described in &header-range;.
852   The partial GET method is intended to reduce unnecessary
853   network usage by allowing partially-retrieved representations to be
854   completed without transferring data already held by the client.
855</t>
856<t>
857   The response to a GET request is cacheable and &MAY; be used to satisfy
858   subsequent GET and HEAD requests (see &caching;).
859</t>
860<t>
861   See <xref target="encoding.sensitive.information.in.uris"/> for security considerations when used for forms.
862</t>
863</section>
864
865<section title="HEAD" anchor="HEAD">
866  <rdf:Description>
867    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
868  </rdf:Description>
869  <iref primary="true" item="HEAD method" x:for-anchor=""/>
870  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
871<t>
872   The HEAD method is identical to GET except that the server &MUST-NOT;
873   return a message-body in the response. The metadata contained
874   in the HTTP header fields in response to a HEAD request &SHOULD; be identical
875   to the information sent in response to a GET request. This method can
876   be used for obtaining metadata about the representation implied by the
877   request without transferring the representation body. This method is
878   often used for testing hypertext links for validity, accessibility,
879   and recent modification.
880</t>
881<t>
882   The response to a HEAD request is cacheable and &MAY; be used to satisfy
883   a subsequent HEAD request; see &caching;. It also &MAY; be used to update a previously cached
884   representation from that resource; if the new field values
885   indicate that the cached representation differs from the current representation (as
886   would be indicated by a change in Content-Length, Content-MD5, ETag
887   or Last-Modified), then the cache &MUST; treat the cache entry as
888   stale.
889</t>
890</section>
891
892<section title="POST" anchor="POST">
893  <iref primary="true" item="POST method" x:for-anchor=""/>
894  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
895<t>
896   The POST method is used to request that the origin server accept the
897   representation enclosed in the request as data to be processed by the
898   target resource. POST is designed to allow a uniform method to cover the
899   following functions:
900  <list style="symbols">
901    <t>
902      Annotation of existing resources;
903    </t>
904    <t>
905        Posting a message to a bulletin board, newsgroup, mailing list,
906        or similar group of articles;
907    </t>
908    <t>
909        Providing a block of data, such as the result of submitting a
910        form, to a data-handling process;
911    </t>
912    <t>
913        Extending a database through an append operation.
914    </t>
915  </list>
916</t>
917<t>
918   The actual function performed by the POST method is determined by the
919   server and is usually dependent on the effective request URI.
920</t>
921<t>
922   The action performed by the POST method might not result in a
923   resource that can be identified by a URI. In this case, either 200
924   (OK) or 204 (No Content) is the appropriate response status code,
925   depending on whether or not the response includes a representation that
926   describes the result.
927</t>
928<t>
929   If a resource has been created on the origin server, the response
930   &SHOULD; be 201 (Created) and contain a representation which describes the
931   status of the request and refers to the new resource, and a Location
932   header field (see <xref target="header.location"/>).
933</t>
934<t>
935   Responses to POST requests are only cacheable when they
936   include explicit freshness information (see &p6-explicit;). A
937   cached POST response with a Content-Location header field
938   (see &header-content-location;) whose value is the effective
939   Request URI &MAY; be used to satisfy subsequent GET and HEAD requests.
940</t>
941<t>
942   Note that POST caching is not widely implemented.
943   However, the 303 (See Other) response can be used to direct the
944   user agent to retrieve a cacheable resource.
945</t>
946</section>
947
948<section title="PUT" anchor="PUT">
949  <iref primary="true" item="PUT method" x:for-anchor=""/>
950  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
951<t>
952   The PUT method requests that the enclosed representation be stored at the
953   effective request URI. If the effective request URI refers to an already
954   existing resource, the enclosed representation &SHOULD; be considered a
955   modified version of the one residing on the origin server. Otherwise, if the
956   effective request URI does not point to an existing resource, and that URI is
957   capable of being defined as a new resource by the requesting user
958   agent, the origin server can create the resource with that URI.
959</t>
960<t>   
961   If a new resource is created at the effective request URI, the origin
962   server &MUST; inform the user agent
963   via the 201 (Created) response. If an existing resource is modified,
964   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
965   to indicate successful completion of the request.
966</t>
967<t>   
968   If the target resource could not be created or modified, an appropriate
969   error response &SHOULD; be given that reflects the nature of the problem.
970   The recipient of the representation &MUST-NOT; ignore any Content-*
971   header fields (headers starting with the prefix "Content-") that it does
972   not understand or implement
973   and &MUST; return a 501 (Not Implemented) response in such cases.
974</t>
975<t>
976   If the request passes through a cache that has one or more stored
977   responses for the effective request URI, those stored responses
978   &SHOULD; be marked as stale if the response to the PUT request
979   has a success status code. Responses to the PUT method are
980   not cacheable.
981</t>
982<t>
983   The fundamental difference between the POST and PUT requests is
984   reflected in the different meaning of the effective request URI. The URI in a
985   POST request identifies the resource that will handle the enclosed
986   representation. That resource might be a data-accepting process, a gateway to
987   some other protocol, or a document that accepts annotations.
988   In contrast, the URI in a PUT request identifies the resource for
989   which enclosed representation is a new or replacement value; the
990   user agent knows what URI is intended and the server &MUST-NOT; attempt
991   to apply the request to some other resource.
992   If the server desires that the request be applied to a different URI,
993   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
994   then make its own decision regarding whether or not to redirect the
995   request.
996</t>
997<t>
998   A single resource &MAY; be identified by many different URIs. For
999   example, an article might have a URI for identifying "the current
1000   version" which is separate from the URI identifying each particular
1001   version. In this case, a PUT request on a general URI might result in
1002   several other URIs being defined by the origin server.
1003</t>
1004<t>
1005   HTTP/1.1 does not define how a PUT method affects the state of an
1006   origin server.
1007</t>
1008<t>
1009   Header fields in a PUT request that are recognized as representation
1010   metadata &SHOULD; be applied to the resource created or modified by
1011   the PUT.  Unrecognized header fields &SHOULD; be ignored.
1012</t>
1013</section>
1014
1015<section title="DELETE" anchor="DELETE">
1016  <iref primary="true" item="DELETE method" x:for-anchor=""/>
1017  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
1018<t>
1019   The DELETE method requests that the origin server delete the target
1020   resource. This method &MAY; be overridden by
1021   human intervention (or other means) on the origin server. The client cannot
1022   be guaranteed that the operation has been carried out, even if the
1023   status code returned from the origin server indicates that the action
1024   has been completed successfully. However, the server &SHOULD-NOT; 
1025   indicate success unless, at the time the response is given, it
1026   intends to delete the resource or move it to an inaccessible
1027   location.
1028</t>
1029<t>
1030   A successful response &SHOULD; be 200 (OK) if the response includes an
1031   representation describing the status, 202 (Accepted) if the action has not
1032   yet been enacted, or 204 (No Content) if the action has been enacted
1033   but the response does not include a representation.
1034</t>
1035<t>
1036   If the request passes through a cache and the effective request URI
1037   identifies one or more currently cached representations, those entries &SHOULD; be
1038   treated as stale. Responses to the DELETE method are not cacheable.
1039</t>
1040</section>
1041
1042<section title="TRACE" anchor="TRACE">
1043  <rdf:Description>
1044    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
1045  </rdf:Description>
1046  <iref primary="true" item="TRACE method" x:for-anchor=""/>
1047  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
1048<t>
1049   The TRACE method is used to invoke a remote, application-layer loop-back
1050   of the request message. The final recipient of the request
1051   &SHOULD; reflect the message received back to the client as the
1052   message-body of a 200 (OK) response. The final recipient is either the
1053   origin server or the first proxy or gateway to receive a Max-Forwards
1054   value of zero (0) in the request (see <xref target="header.max-forwards"/>).
1055   A TRACE request &MUST-NOT; include a message-body.
1056</t>
1057<t>
1058   TRACE allows the client to see what is being received at the other
1059   end of the request chain and use that data for testing or diagnostic
1060   information. The value of the Via header field (&header-via;) is of
1061   particular interest, since it acts as a trace of the request chain.
1062   Use of the Max-Forwards header field allows the client to limit the
1063   length of the request chain, which is useful for testing a chain of
1064   proxies forwarding messages in an infinite loop.
1065</t>
1066<t>
1067   If the request is valid, the response &SHOULD; have a Content-Type of
1068   "message/http" (see &media-type-message-http;) and contain a message-body
1069   that encloses a copy of the entire request message.
1070   Responses to the TRACE method are not cacheable.
1071</t>
1072</section>
1073
1074<section title="CONNECT" anchor="CONNECT">
1075  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1076  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1077<t>
1078   This specification reserves the method name CONNECT for use with a
1079   proxy that can dynamically switch to being a tunnel (e.g., SSL
1080   tunneling <xref target="RFC2817"/>).
1081</t>
1082</section>
1083</section>
1084
1085
1086<section title="Status Code Definitions" anchor="status.codes">
1087<t>
1088   Each Status-Code is described below, including any metadata required
1089   in the response.
1090</t>
1091
1092<section title="Informational 1xx" anchor="status.1xx">
1093<t>
1094   This class of status code indicates a provisional response,
1095   consisting only of the Status-Line and optional header fields, and is
1096   terminated by an empty line. There are no required header fields for this
1097   class of status code. Since HTTP/1.0 did not define any 1xx status
1098   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1099   except under experimental conditions.
1100</t>
1101<t>
1102   A client &MUST; be prepared to accept one or more 1xx status responses
1103   prior to a regular response, even if the client does not expect a 100
1104   (Continue) status message. Unexpected 1xx status responses &MAY; be
1105   ignored by a user agent.
1106</t>
1107<t>
1108   Proxies &MUST; forward 1xx responses, unless the connection between the
1109   proxy and its client has been closed, or unless the proxy itself
1110   requested the generation of the 1xx response. (For example, if a
1111   proxy adds a "Expect: 100-continue" field when it forwards a request,
1112   then it need not forward the corresponding 100 (Continue)
1113   response(s).)
1114</t>
1115
1116<section title="100 Continue" anchor="status.100">
1117  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1118  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1119<t>
1120   The client &SHOULD; continue with its request. This interim response is
1121   used to inform the client that the initial part of the request has
1122   been received and has not yet been rejected by the server. The client
1123   &SHOULD; continue by sending the remainder of the request or, if the
1124   request has already been completed, ignore this response. The server
1125   &MUST; send a final response after the request has been completed. See
1126   &use100; for detailed discussion of the use and handling of this
1127   status code.
1128</t>
1129</section>
1130
1131<section title="101 Switching Protocols" anchor="status.101">
1132  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1133  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1134<t>
1135   The server understands and is willing to comply with the client's
1136   request, via the Upgrade message header field (&header-upgrade;), for a
1137   change in the application protocol being used on this connection. The
1138   server will switch protocols to those defined by the response's
1139   Upgrade header field immediately after the empty line which
1140   terminates the 101 response.
1141</t>
1142<t>
1143   The protocol &SHOULD; be switched only when it is advantageous to do
1144   so. For example, switching to a newer version of HTTP is advantageous
1145   over older versions, and switching to a real-time, synchronous
1146   protocol might be advantageous when delivering resources that use
1147   such features.
1148</t>
1149</section>
1150</section>
1151
1152<section title="Successful 2xx" anchor="status.2xx">
1153<t>
1154   This class of status code indicates that the client's request was
1155   successfully received, understood, and accepted.
1156</t>
1157
1158<section title="200 OK" anchor="status.200">
1159  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1160  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1161<t>
1162   The request has succeeded. The payload returned with the response
1163   is dependent on the method used in the request, for example:
1164  <list style="hanging">
1165    <t hangText="GET">
1166          a representation of the target resource is sent in the response;
1167    </t>
1168    <t hangText="HEAD">
1169          the same representation as GET, except without the message-body;
1170    </t>
1171    <t hangText="POST">
1172      a representation describing or containing the result of the action;
1173    </t>
1174    <t hangText="TRACE">
1175      a representation containing the request message as received by the
1176      end server.
1177    </t>
1178  </list>
1179</t>
1180<t>
1181   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1182   freshness for 200 responses.
1183</t>
1184</section>
1185
1186<section title="201 Created" anchor="status.201">
1187  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1188  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1189<t>
1190   The request has been fulfilled and has resulted in a new resource being
1191   created. The newly created resource can be referenced by the URI(s)
1192   returned in the payload of the response, with the most specific URI
1193   for the resource given by a Location header field. The response
1194   &SHOULD; include a payload containing a list of resource
1195   characteristics and location(s) from which the user or user agent can
1196   choose the one most appropriate. The payload format is specified by
1197   the media type given in the Content-Type header field. The origin
1198   server &MUST; create the resource before returning the 201 status code.
1199   If the action cannot be carried out immediately, the server &SHOULD;
1200   respond with 202 (Accepted) response instead.
1201</t>
1202<t>
1203   A 201 response &MAY; contain an ETag response header field indicating
1204   the current value of the entity-tag for the representation of the resource
1205   just created (see &header-etag;).
1206</t>
1207</section>
1208
1209<section title="202 Accepted" anchor="status.202">
1210  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1211  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1212<t>
1213   The request has been accepted for processing, but the processing has
1214   not been completed.  The request might or might not eventually be
1215   acted upon, as it might be disallowed when processing actually takes
1216   place. There is no facility for re-sending a status code from an
1217   asynchronous operation such as this.
1218</t>
1219<t>
1220   The 202 response is intentionally non-committal. Its purpose is to
1221   allow a server to accept a request for some other process (perhaps a
1222   batch-oriented process that is only run once per day) without
1223   requiring that the user agent's connection to the server persist
1224   until the process is completed. The representation returned with this
1225   response &SHOULD; include an indication of the request's current status
1226   and either a pointer to a status monitor or some estimate of when the
1227   user can expect the request to be fulfilled.
1228</t>
1229</section>
1230
1231<section title="203 Non-Authoritative Information" anchor="status.203">
1232  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1233  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1234<t>
1235   The returned metadata in the header fields is not the
1236   definitive set as available from the origin server, but is gathered
1237   from a local or a third-party copy. The set presented &MAY; be a subset
1238   or superset of the original version. For example, including local
1239   annotation information about the resource might result in a superset
1240   of the metadata known by the origin server. Use of this
1241   response code is not required and is only appropriate when the
1242   response would otherwise be 200 (OK).
1243</t>
1244<t>
1245   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1246   freshness for 203 responses.
1247</t>
1248
1249</section>
1250
1251<section title="204 No Content" anchor="status.204">
1252  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1253  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1254<t>
1255   The server has successfully fulfilled the request, but there is no
1256   additional content to return in the response payload body.  The
1257   resource metadata and representation metadata in the response message's
1258   header fields refer to the target resource
1259   and its current representation, respectively, after the requested action.
1260   For example, if a 204 status code is received in response to a PUT
1261   and the response contains an ETag header field, then the value of
1262   that field is the current entity-tag for the representation that
1263   was successfully PUT.
1264</t>
1265<t>
1266   If the client is a user agent, it &SHOULD-NOT; change its document view
1267   from that which caused the request to be sent. This response is
1268   primarily intended to allow input for actions to take place without
1269   causing a change to the user agent's active document view, although
1270   any new or updated metadata &SHOULD; be applied to the document
1271   currently in the user agent's active view.
1272</t>
1273<t>
1274   The 204 response &MUST-NOT; include a message-body, and thus is always
1275   terminated by the first empty line after the header fields.
1276</t>
1277</section>
1278
1279<section title="205 Reset Content" anchor="status.205">
1280  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1281  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1282<t>
1283   The server has fulfilled the request and the user agent &SHOULD; reset
1284   the document view which caused the request to be sent. This response
1285   is primarily intended to allow input for actions to take place via
1286   user input, followed by a clearing of the form in which the input is
1287   given so that the user can easily initiate another input action. The
1288   response &MUST-NOT; include a message-body.
1289</t>
1290</section>
1291
1292<section title="206 Partial Content" anchor="status.206">
1293  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1294  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1295  <rdf:Description>
1296    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1297  </rdf:Description>
1298<t>
1299   The server has fulfilled the partial GET request for the resource
1300   and the enclosed payload is a partial representation as defined in &status-206;.
1301</t>
1302<t>
1303   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1304   freshness for 206 responses.
1305</t>
1306</section>
1307</section>
1308
1309<section title="Redirection 3xx" anchor="status.3xx">
1310<t>
1311   This class of status code indicates that further action needs to be
1312   taken by the user agent in order to fulfill the request.  The action
1313   required &MAY; be carried out by the user agent without interaction
1314   with the user if and only if the method used in the second request is
1315   known to be "safe", as defined in <xref target="safe.methods"/>.
1316   A client &SHOULD; detect infinite redirection loops, since such loops
1317   generate network traffic for each redirection.
1318</t>
1319<x:note>
1320  <t>
1321    <x:h>Note:</x:h> An earlier version of this specification recommended a
1322    maximum of five redirections (<xref target="RFC2068" x:fmt="," x:sec="10.3"/>).
1323    Content developers need to be aware that some clients might
1324    implement such a fixed limitation.
1325  </t>
1326</x:note>
1327
1328<section title="300 Multiple Choices" anchor="status.300">
1329  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1330  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1331<t>
1332   The target resource more than one
1333   representation, each with its own specific location, and agent-driven
1334   negotiation information (&content-negotiation;) is being provided so that
1335   the user (or user agent) can select a preferred representation by
1336   redirecting its request to that location.
1337</t>
1338<t>
1339   Unless it was a HEAD request, the response &SHOULD; include a representation
1340   containing a list of representation metadata and location(s) from
1341   which the user or user agent can choose the one most appropriate. The
1342   data format is specified by the media type given in the Content-Type
1343   header field. Depending upon the format and the capabilities of
1344   the user agent, selection of the most appropriate choice &MAY; be
1345   performed automatically. However, this specification does not define
1346   any standard for such automatic selection.
1347</t>
1348<t>
1349   If the server has a preferred choice of representation, it &SHOULD;
1350   include the specific URI for that representation in the Location
1351   field; user agents &MAY; use the Location field value for automatic
1352   redirection.
1353</t>
1354<t>
1355   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1356   freshness for 300 responses.
1357</t>
1358
1359</section>
1360
1361<section title="301 Moved Permanently" anchor="status.301">
1362  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1363  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1364<t>
1365   The target resource has been assigned a new permanent URI and any
1366   future references to this resource &SHOULD; use one of the returned
1367   URIs.  Clients with link editing capabilities ought to automatically
1368   re-link references to the effective request URI to one or more of the new
1369   references returned by the server, where possible.
1370</t>
1371<t>
1372   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine
1373   freshness for 301 responses.
1374</t>
1375<t>
1376   The new permanent URI &SHOULD; be given by the Location field in the
1377   response. Unless the request method was HEAD, the representation of the
1378   response &SHOULD; contain a short hypertext note with a hyperlink to
1379   the new URI(s).
1380</t>
1381<t>
1382   If the 301 status code is received in response to a request method
1383   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1384   then the request &MAY; be automatically redirected by the user agent without
1385   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1386   request unless it can be confirmed by the user, since this might
1387   change the conditions under which the request was issued.
1388</t>
1389<x:note>
1390  <t>
1391    <x:h>Note:</x:h> When automatically redirecting a POST request after
1392    receiving a 301 status code, some existing HTTP/1.0 user agents
1393    will erroneously change it into a GET request.
1394  </t>
1395</x:note>
1396</section>
1397
1398<section title="302 Found" anchor="status.302">
1399  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1400  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1401<t>
1402   The target resource resides temporarily under a different URI.
1403   Since the redirection might be altered on occasion, the client &SHOULD;
1404   continue to use the effective request URI for future requests.
1405</t>
1406<t>
1407   The temporary URI &SHOULD; be given by the Location field in the
1408   response. Unless the request method was HEAD, the representation of the
1409   response &SHOULD; contain a short hypertext note with a hyperlink to
1410   the new URI(s).
1411</t>
1412<t>
1413   If the 302 status code is received in response to a request method
1414   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1415   then the request &MAY; be automatically redirected by the user agent without
1416   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1417   request unless it can be confirmed by the user, since this might
1418   change the conditions under which the request was issued.
1419</t>
1420<x:note>
1421  <t>
1422    <x:h>Note:</x:h> HTTP/1.0 (<xref target="RFC1945" x:fmt="," x:sec="9.3"/>)
1423    and the first version of HTTP/1.1 (<xref target="RFC2068" x:fmt="," x:sec ="10.3.3"/>)
1424    specify that the client is not allowed to change the method on the
1425    redirected request.  However, most existing user agent implementations
1426    treat 302 as if it were a 303 response, performing a GET on the Location
1427    field-value regardless of the original request method. Therefore, a
1428    previous version of this specification
1429    (<xref target="RFC2616" x:fmt="," x:sec="10.3.3"/>) has added the
1430    status codes
1431    <xref target="status.303" format="none">303</xref> and
1432    <xref target="status.307" format="none">307</xref> for servers that wish
1433    to make unambiguously clear which kind of reaction is expected of the
1434    client.
1435  </t>
1436</x:note>
1437</section>
1438
1439<section title="303 See Other" anchor="status.303">
1440  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1441  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1442<t>
1443   The server directs the user agent to a different resource, indicated
1444   by a URI in the Location header field, that provides an indirect
1445   response to the original request.  The user agent &MAY; perform a GET
1446   request on the URI in the Location field in order to obtain a
1447   representation corresponding to the response, be redirected again,
1448   or end with an error status.  The Location URI is not a substitute
1449   reference for the effective request URI.
1450</t>
1451<t>
1452   The 303 status code is generally applicable to any HTTP method.  It is
1453   primarily used to allow the output of a POST action to redirect
1454   the user agent to a selected resource, since doing so provides the
1455   information corresponding to the POST response in a form that
1456   can be separately identified, bookmarked, and cached independent
1457   of the original request.
1458</t>
1459<t>
1460   A 303 response to a GET request indicates that the requested
1461   resource does not have a representation of its own that can be
1462   transferred by the server over HTTP.  The Location URI indicates a
1463   resource that is descriptive of the target resource, such that the
1464   follow-on representation might be useful to recipients without
1465   implying that it adequately represents the target resource.
1466   Note that answers to the questions of what can be represented, what
1467   representations are adequate, and what might be a useful description
1468   are outside the scope of HTTP and thus entirely determined by the
1469   URI owner(s).
1470</t>
1471<t>
1472   Except for responses to a HEAD request, the representation of a 303
1473   response &SHOULD; contain a short hypertext note with a hyperlink
1474   to the Location URI.
1475</t>
1476</section>
1477
1478<section title="304 Not Modified" anchor="status.304">
1479  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1480  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1481  <rdf:Description>
1482    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1483  </rdf:Description>
1484<t>
1485   The response to the request has not been modified since the conditions
1486   indicated by the client's conditional GET request, as defined in &status-304;.
1487</t>
1488</section>
1489
1490<section title="305 Use Proxy" anchor="status.305">
1491  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1492  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1493<t>
1494   The 305 status code was defined in a previous version of this specification
1495   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1496</t>
1497</section>
1498
1499<section title="306 (Unused)" anchor="status.306">
1500  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1501  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1502<t>
1503   The 306 status code was used in a previous version of the
1504   specification, is no longer used, and the code is reserved.
1505</t>
1506</section>
1507
1508<section title="307 Temporary Redirect" anchor="status.307">
1509  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1510  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1511<t>
1512   The target resource resides temporarily under a different URI.
1513   Since the redirection can change over time, the client &SHOULD;
1514   continue to use the effective request URI for future requests.
1515</t>
1516<t>
1517   The temporary URI &SHOULD; be given by the Location field in the
1518   response. Unless the request method was HEAD, the representation of the
1519   response &SHOULD; contain a short hypertext note with a hyperlink to
1520   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1521   understand the 307 status code. Therefore, the note &SHOULD; contain the
1522   information necessary for a user to repeat the original request on
1523   the new URI.
1524</t>
1525<t>
1526   If the 307 status code is received in response to a request method
1527   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1528   then the request &MAY; be automatically redirected by the user agent without
1529   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1530   request unless it can be confirmed by the user, since this might
1531   change the conditions under which the request was issued.
1532</t>
1533</section>
1534</section>
1535
1536<section title="Client Error 4xx" anchor="status.4xx">
1537<t>
1538   The 4xx class of status code is intended for cases in which the
1539   client seems to have erred. Except when responding to a HEAD request,
1540   the server &SHOULD; include a representation containing an explanation of the
1541   error situation, and whether it is a temporary or permanent
1542   condition. These status codes are applicable to any request method.
1543   User agents &SHOULD; display any included representation to the user.
1544</t>
1545<t>
1546   If the client is sending data, a server implementation using TCP
1547   &SHOULD; be careful to ensure that the client acknowledges receipt of
1548   the packet(s) containing the response, before the server closes the
1549   input connection. If the client continues sending data to the server
1550   after the close, the server's TCP stack will send a reset packet to
1551   the client, which might erase the client's unacknowledged input buffers
1552   before they can be read and interpreted by the HTTP application.
1553</t>
1554
1555<section title="400 Bad Request" anchor="status.400">
1556  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1557  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1558<t>
1559   The request could not be understood by the server due to malformed
1560   syntax. The client &SHOULD-NOT; repeat the request without
1561   modifications.
1562</t>
1563</section>
1564
1565<section title="401 Unauthorized" anchor="status.401">
1566  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1567  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1568  <rdf:Description>
1569    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part7</redirects-to>
1570  </rdf:Description>
1571<t>
1572   The request requires user authentication (see &status-401;).
1573</t>
1574</section>
1575
1576<section title="402 Payment Required" anchor="status.402">
1577  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1578  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1579<t>
1580   This code is reserved for future use.
1581</t>
1582</section>
1583
1584<section title="403 Forbidden" anchor="status.403">
1585  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1586  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1587<t>
1588   The server understood the request, but is refusing to fulfill it.
1589   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1590   If the request method was not HEAD and the server wishes to make
1591   public why the request has not been fulfilled, it &SHOULD; describe the
1592   reason for the refusal in the representation.  If the server does not wish to
1593   make this information available to the client, the status code 404
1594   (Not Found) can be used instead.
1595</t>
1596</section>
1597
1598<section title="404 Not Found" anchor="status.404">
1599  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1600  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1601<t>
1602   The server has not found anything matching the effective request URI. No
1603   indication is given of whether the condition is temporary or
1604   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1605   knows, through some internally configurable mechanism, that an old
1606   resource is permanently unavailable and has no forwarding address.
1607   This status code is commonly used when the server does not wish to
1608   reveal exactly why the request has been refused, or when no other
1609   response is applicable.
1610</t>
1611</section>
1612
1613<section title="405 Method Not Allowed" anchor="status.405">
1614  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1615  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1616<t>
1617   The method specified in the Request-Line is not allowed for the target
1618   resource. The response &MUST; include an
1619   Allow header field containing a list of valid methods for the requested
1620   resource.
1621</t>
1622</section>
1623
1624<section title="406 Not Acceptable" anchor="status.406">
1625  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1626  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1627<t>
1628   The resource identified by the request is only capable of generating
1629   response representations which have content characteristics not acceptable
1630   according to the accept header fields sent in the request.
1631</t>
1632<t>
1633   Unless it was a HEAD request, the response &SHOULD; include a representation
1634   containing a list of available representation characteristics and location(s)
1635   from which the user or user agent can choose the one most
1636   appropriate. The data format is specified by the media type given
1637   in the Content-Type header field. Depending upon the format and the
1638   capabilities of the user agent, selection of the most appropriate
1639   choice &MAY; be performed automatically. However, this specification
1640   does not define any standard for such automatic selection.
1641</t>
1642<x:note>
1643  <t>
1644    <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1645    not acceptable according to the accept header fields sent in the
1646    request. In some cases, this might even be preferable to sending a
1647    406 response. User agents are encouraged to inspect the header fields of
1648    an incoming response to determine if it is acceptable.
1649  </t>
1650</x:note>
1651<t>
1652   If the response could be unacceptable, a user agent &SHOULD;
1653   temporarily stop receipt of more data and query the user for a
1654   decision on further actions.
1655</t>
1656</section>
1657
1658<section title="407 Proxy Authentication Required" anchor="status.407">
1659  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1660  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1661<t>
1662   This code is similar to 401 (Unauthorized), but indicates that the
1663   client must first authenticate itself with the proxy (see &status-407;).
1664</t>
1665</section>
1666
1667<section title="408 Request Timeout" anchor="status.408">
1668  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1669  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1670<t>
1671   The client did not produce a request within the time that the server
1672   was prepared to wait. The client &MAY; repeat the request without
1673   modifications at any later time.
1674</t>
1675</section>
1676
1677<section title="409 Conflict" anchor="status.409">
1678  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1679  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1680<t>
1681   The request could not be completed due to a conflict with the current
1682   state of the resource. This code is only allowed in situations where
1683   it is expected that the user might be able to resolve the conflict
1684   and resubmit the request. The response body &SHOULD; include enough
1685   information for the user to recognize the source of the conflict.
1686   Ideally, the response representation would include enough information for the
1687   user or user agent to fix the problem; however, that might not be
1688   possible and is not required.
1689</t>
1690<t>
1691   Conflicts are most likely to occur in response to a PUT request. For
1692   example, if versioning were being used and the representation being PUT
1693   included changes to a resource which conflict with those made by an
1694   earlier (third-party) request, the server might use the 409 response
1695   to indicate that it can't complete the request. In this case, the
1696   response representation would likely contain a list of the differences
1697   between the two versions in a format defined by the response
1698   Content-Type.
1699</t>
1700</section>
1701
1702<section title="410 Gone" anchor="status.410">
1703  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1704  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1705<t>
1706   The target resource is no longer available at the server and no
1707   forwarding address is known. This condition is expected to be
1708   considered permanent. Clients with link editing capabilities &SHOULD;
1709   delete references to the effective request URI after user approval. If the
1710   server does not know, or has no facility to determine, whether or not
1711   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1712   used instead.
1713</t>
1714<t>
1715   The 410 response is primarily intended to assist the task of web
1716   maintenance by notifying the recipient that the resource is
1717   intentionally unavailable and that the server owners desire that
1718   remote links to that resource be removed. Such an event is common for
1719   limited-time, promotional services and for resources belonging to
1720   individuals no longer working at the server's site. It is not
1721   necessary to mark all permanently unavailable resources as "gone" or
1722   to keep the mark for any length of time -- that is left to the
1723   discretion of the server owner.
1724</t>
1725<t>
1726   Caches &MAY; use a heuristic (see &p6-heuristic;) to determine freshness
1727   for 410 responses.
1728</t>
1729
1730</section>
1731
1732<section title="411 Length Required" anchor="status.411">
1733  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1734  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1735<t>
1736   The server refuses to accept the request without a defined Content-Length.
1737   The client &MAY; repeat the request if it adds a valid
1738   Content-Length header field containing the length of the message-body
1739   in the request message.
1740</t>
1741</section>
1742
1743<section title="412 Precondition Failed" anchor="status.412">
1744  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1745  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1746  <rdf:Description>
1747    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part4</redirects-to>
1748  </rdf:Description>
1749<t>
1750   The precondition given in one or more of the request-header fields
1751   evaluated to false when it was tested on the server, as defined in
1752   &status-412;.
1753</t>
1754</section>
1755
1756<section title="413 Request Entity Too Large" anchor="status.413">
1757  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1758  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1759<t>
1760   The server is refusing to process a request because the request
1761   representation is larger than the server is willing or able to process. The
1762   server &MAY; close the connection to prevent the client from continuing
1763   the request.
1764</t>
1765<t>
1766   If the condition is temporary, the server &SHOULD; include a Retry-After
1767   header field to indicate that it is temporary and after what
1768   time the client &MAY; try again.
1769</t>
1770</section>
1771
1772<section title="414 URI Too Long" anchor="status.414">
1773  <iref primary="true" item="414 URI Too Long (status code)" x:for-anchor=""/>
1774  <iref primary="true" item="Status Codes" subitem="414 URI Too Long" x:for-anchor=""/>
1775<t>
1776   The server is refusing to service the request because the effective request URI
1777   is longer than the server is willing to interpret. This rare
1778   condition is only likely to occur when a client has improperly
1779   converted a POST request to a GET request with long query
1780   information, when the client has descended into a URI "black hole" of
1781   redirection (e.g., a redirected URI prefix that points to a suffix of
1782   itself), or when the server is under attack by a client attempting to
1783   exploit security holes present in some servers using fixed-length
1784   buffers for reading or manipulating the effective request URI.
1785</t>
1786</section>
1787
1788<section title="415 Unsupported Media Type" anchor="status.415">
1789  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1790  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1791<t>
1792   The server is refusing to service the request because the representation of
1793   the request is in a format not supported by the target resource
1794   for the requested method.
1795</t>
1796</section>
1797
1798<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1799  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1800  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1801  <rdf:Description>
1802    <redirects-to xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">Part5</redirects-to>
1803  </rdf:Description>
1804<t>
1805   The request included a Range request-header field (&header-range;) and none of
1806   the range-specifier values in this field overlap the current extent
1807   of the selected resource. See &status-416;.
1808</t>
1809</section>
1810
1811<section title="417 Expectation Failed" anchor="status.417">
1812  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1813  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1814<t>
1815   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1816   could not be met by this server, or, if the server is a proxy,
1817   the server has unambiguous evidence that the request could not be met
1818   by the next-hop server.
1819</t>
1820</section>
1821</section>
1822
1823<section title="Server Error 5xx" anchor="status.5xx">
1824<t>
1825   Response status codes beginning with the digit "5" indicate cases in
1826   which the server is aware that it has erred or is incapable of
1827   performing the request. Except when responding to a HEAD request, the
1828   server &SHOULD; include a representation containing an explanation of the
1829   error situation, and whether it is a temporary or permanent
1830   condition. User agents &SHOULD; display any included representation to the
1831   user. These response codes are applicable to any request method.
1832</t>
1833
1834<section title="500 Internal Server Error" anchor="status.500">
1835  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1836  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1837<t>
1838   The server encountered an unexpected condition which prevented it
1839   from fulfilling the request.
1840</t>
1841</section>
1842
1843<section title="501 Not Implemented" anchor="status.501">
1844  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1845  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1846<t>
1847   The server does not support the functionality required to fulfill the
1848   request. This is the appropriate response when the server does not
1849   recognize the request method and is not capable of supporting it for
1850   any resource.
1851</t>
1852</section>
1853
1854<section title="502 Bad Gateway" anchor="status.502">
1855  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1856  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1857<t>
1858   The server, while acting as a gateway or proxy, received an invalid
1859   response from the upstream server it accessed in attempting to
1860   fulfill the request.
1861</t>
1862</section>
1863
1864<section title="503 Service Unavailable" anchor="status.503">
1865  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1866  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1867<t>
1868   The server is currently unable to handle the request due to a
1869   temporary overloading or maintenance of the server. The implication
1870   is that this is a temporary condition which will be alleviated after
1871   some delay. If known, the length of the delay &MAY; be indicated in a
1872   Retry-After header field. If no Retry-After is given, the client &SHOULD;
1873   handle the response as it would for a 500 response.
1874</t>
1875<x:note>
1876  <t>
1877    <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1878    server must use it when becoming overloaded. Some servers might wish
1879    to simply refuse the connection.
1880  </t>
1881</x:note>
1882</section>
1883
1884<section title="504 Gateway Timeout" anchor="status.504">
1885  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1886  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1887<t>
1888   The server, while acting as a gateway or proxy, did not receive a
1889   timely response from the upstream server specified by the URI (e.g.,
1890   HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
1891   to access in attempting to complete the request.
1892</t>
1893<x:note>
1894  <t>
1895    <x:h>Note</x:h> to implementors: some deployed proxies are known to
1896    return 400 or 500 when DNS lookups time out.
1897  </t>
1898</x:note>
1899</section>
1900
1901<section title="505 HTTP Version Not Supported" anchor="status.505">
1902  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1903  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
1904<t>
1905   The server does not support, or refuses to support, the protocol
1906   version that was used in the request message. The server is
1907   indicating that it is unable or unwilling to complete the request
1908   using the same major version as the client, as described in &http-version;,
1909   other than with this error message. The response &SHOULD; contain
1910   a representation describing why that version is not supported and what other
1911   protocols are supported by that server.
1912</t>
1913
1914</section>
1915</section>
1916</section>
1917
1918
1919<section title="Header Field Definitions" anchor="header.fields">
1920<t>
1921   This section defines the syntax and semantics of HTTP/1.1 header fields
1922   related to request and response semantics.
1923</t>
1924
1925<section title="Allow" anchor="header.allow">
1926  <iref primary="true" item="Allow header" x:for-anchor=""/>
1927  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
1928  <x:anchor-alias value="Allow"/>
1929  <x:anchor-alias value="Allow-v"/>
1930<t>
1931   The "Allow" response-header field lists the set of methods advertised as
1932   supported by the target resource. The purpose of
1933   this field is strictly to inform the recipient of valid methods
1934   associated with the resource.
1935</t>
1936<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
1937  <x:ref>Allow</x:ref>   = "Allow" ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
1938  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
1939</artwork></figure>
1940<t>
1941      Example of use:
1942</t>
1943<figure><artwork type="example">
1944  Allow: GET, HEAD, PUT
1945</artwork></figure>
1946<t>
1947      The actual set of allowed methods is defined
1948      by the origin server at the time of each request.
1949</t>
1950<t>
1951      A proxy &MUST-NOT; modify the Allow header field even if it does not
1952      understand all the methods specified, since the user agent might
1953      have other means of communicating with the origin server.
1954</t>
1955</section>
1956
1957<section title="Expect" anchor="header.expect">
1958  <iref primary="true" item="Expect header" x:for-anchor=""/>
1959  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
1960  <x:anchor-alias value="Expect"/>
1961  <x:anchor-alias value="Expect-v"/>
1962  <x:anchor-alias value="expectation"/>
1963  <x:anchor-alias value="expectation-extension"/>
1964  <x:anchor-alias value="expect-params"/>
1965<t>
1966   The "Expect" request-header field is used to indicate that particular
1967   server behaviors are required by the client.
1968</t>
1969<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"/>
1970  <x:ref>Expect</x:ref>       = "Expect" ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
1971  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
1972 
1973  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
1974  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
1975                           *<x:ref>expect-params</x:ref> ]
1976  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
1977</artwork></figure>
1978<t>
1979   A server that does not understand or is unable to comply with any of
1980   the expectation values in the Expect field of a request &MUST; respond
1981   with appropriate error status code. The server &MUST; respond with a 417
1982   (Expectation Failed) status code if any of the expectations cannot be met
1983   or, if there are other problems with the request, some other 4xx
1984   status code.
1985</t>
1986<t>
1987   This header field is defined with extensible syntax to allow for
1988   future extensions. If a server receives a request containing an
1989   Expect field that includes an expectation-extension that it does not
1990   support, it &MUST; respond with a 417 (Expectation Failed) status code.
1991</t>
1992<t>
1993   Comparison of expectation values is case-insensitive for unquoted
1994   tokens (including the 100-continue token), and is case-sensitive for
1995   quoted-string expectation-extensions.
1996</t>
1997<t>
1998   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
1999   return a 417 (Expectation Failed) status code if it receives a request
2000   with an expectation that it cannot meet. However, the Expect
2001   request-header field itself is end-to-end; it &MUST; be forwarded if the
2002   request is forwarded.
2003</t>
2004<t>
2005   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
2006   Expect header field.
2007</t>
2008<t>
2009   See &use100; for the use of the 100 (Continue) status code.
2010</t>
2011</section>
2012
2013<section title="From" anchor="header.from">
2014  <iref primary="true" item="From header" x:for-anchor=""/>
2015  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
2016  <x:anchor-alias value="From"/>
2017  <x:anchor-alias value="From-v"/>
2018  <x:anchor-alias value="mailbox"/>
2019<t>
2020   The "From" request-header field, if given, &SHOULD; contain an Internet
2021   e-mail address for the human user who controls the requesting user
2022   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
2023   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
2024</t>
2025<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
2026  <x:ref>From</x:ref>    = "From" ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
2027  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
2028 
2029  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
2030</artwork></figure>
2031<t>
2032   An example is:
2033</t>
2034<figure><artwork type="example">
2035  From: webmaster@example.org
2036</artwork></figure>
2037<t>
2038   This header field &MAY; be used for logging purposes and as a means for
2039   identifying the source of invalid or unwanted requests. It &SHOULD-NOT; 
2040   be used as an insecure form of access protection. The interpretation
2041   of this field is that the request is being performed on behalf of the
2042   person given, who accepts responsibility for the method performed. In
2043   particular, robot agents &SHOULD; include this header field so that the
2044   person responsible for running the robot can be contacted if problems
2045   occur on the receiving end.
2046</t>
2047<t>
2048   The Internet e-mail address in this field &MAY; be separate from the
2049   Internet host which issued the request. For example, when a request
2050   is passed through a proxy the original issuer's address &SHOULD; be
2051   used.
2052</t>
2053<t>
2054   The client &SHOULD-NOT;  send the From header field without the user's
2055   approval, as it might conflict with the user's privacy interests or
2056   their site's security policy. It is strongly recommended that the
2057   user be able to disable, enable, and modify the value of this field
2058   at any time prior to a request.
2059</t>
2060</section>
2061
2062<section title="Location" anchor="header.location">
2063  <iref primary="true" item="Location header" x:for-anchor=""/>
2064  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
2065  <x:anchor-alias value="Location"/>
2066  <x:anchor-alias value="Location-v"/>
2067<t>
2068   The "Location" response-header field is used to identify a newly created
2069   resource, or to redirect the recipient to a different location for
2070   completion of the request.
2071</t>
2072<t>
2073   For 201 (Created) responses, the Location is the URI of the new resource
2074   which was created by the request. For 3xx responses, the location &SHOULD;
2075   indicate the server's preferred URI for automatic redirection to the
2076   resource.
2077</t>
2078<t>
2079   The field value consists of a single URI-reference. When it has the form
2080   of a relative reference (<xref target="RFC3986" x:fmt="," x:sec="4.2"/>),
2081   the final value is computed by resolving it against the effective request
2082   URI (<xref target="RFC3986" x:fmt="," x:sec="5"/>).
2083</t>
2084<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
2085  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
2086  <x:ref>Location-v</x:ref>     = <x:ref>URI-reference</x:ref>
2087</artwork></figure>
2088<figure>
2089<preamble>Examples are:</preamble><!--DO NOT DARE changing the vertical WSP below, it's necessary this way for xml2rfc-->
2090<artwork type="example">
2091  Location: http://www.example.org/pub/WWW/People.html#tim
2092</artwork></figure><figure><artwork type="example">  Location: /index.html
2093</artwork></figure>
2094<t>
2095   There are circumstances in which a fragment identifier in a Location URI
2096   would not be appropriate:
2097   <list style="symbols">
2098      <t>With a 201 Created response, because in this usage the Location header
2099      field specifies the URI for the entire created resource.</t>
2100      <t>With 305 Use Proxy.</t>
2101   </list>
2102</t>
2103<x:note>
2104  <t>
2105    <x:h>Note:</x:h> This specification does not define precedence rules
2106    for the case where the original URI, as navigated to by the user
2107    agent, and the Location header field value both contain fragment
2108    identifiers.
2109  </t>
2110</x:note>
2111<x:note>
2112  <t>
2113    <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
2114    from Location in that the Content-Location identifies the most specific
2115    resource corresponding to the enclosed representation.
2116    It is therefore possible for a response to contain header fields for
2117    both Location and Content-Location.
2118  </t>
2119</x:note>
2120</section>
2121
2122<section title="Max-Forwards" anchor="header.max-forwards">
2123  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
2124  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
2125  <x:anchor-alias value="Max-Forwards"/>
2126  <x:anchor-alias value="Max-Forwards-v"/>
2127<t>
2128   The "Max-Forwards" request-header field provides a mechanism with the
2129   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>)
2130   methods to limit the number of times that the request is forwarded by
2131   proxies or gateways. This can be useful when the client is attempting to
2132   trace a request which appears to be failing or looping in mid-chain.
2133</t>
2134<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
2135  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
2136  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
2137</artwork></figure>
2138<t>
2139   The Max-Forwards value is a decimal integer indicating the remaining
2140   number of times this request message can be forwarded.
2141</t>
2142<t>
2143   Each proxy or gateway recipient of a TRACE or OPTIONS request
2144   containing a Max-Forwards header field &MUST; check and update its
2145   value prior to forwarding the request. If the received value is zero
2146   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2147   respond as the final recipient. If the received Max-Forwards value is
2148   greater than zero, then the forwarded message &MUST; contain an updated
2149   Max-Forwards field with a value decremented by one (1).
2150</t>
2151<t>
2152   The Max-Forwards header field &MAY; be ignored for all other methods
2153   defined by this specification and for any extension methods for which
2154   it is not explicitly referred to as part of that method definition.
2155</t>
2156</section>
2157
2158<section title="Referer" anchor="header.referer">
2159  <iref primary="true" item="Referer header" x:for-anchor=""/>
2160  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
2161  <x:anchor-alias value="Referer"/>
2162  <x:anchor-alias value="Referer-v"/>
2163<t>
2164   The "Referer" [sic] request-header field allows the client to specify the
2165   URI of the resource from which the effective request URI was obtained (the
2166   "referrer", although the header field is misspelled.).
2167</t>
2168<t>
2169   The Referer header field allows servers to generate lists of back-links to
2170   resources for interest, logging, optimized caching, etc. It also allows
2171   obsolete or mistyped links to be traced for maintenance. Some servers use
2172   Referer as a means of controlling where they allow links from (so-called
2173   "deep linking"), but legitimate requests do not always
2174   contain a Referer header field.
2175</t>
2176<t>
2177   If the effective request URI was obtained from a source that does not have its own
2178   URI (e.g., input from the user keyboard), the Referer field &MUST; either be
2179   sent with the value "about:blank", or not be sent at all. Note that this
2180   requirement does not apply to sources with non-HTTP URIs (e.g., FTP).
2181</t>
2182<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
2183  <x:ref>Referer</x:ref>        = "Referer" ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
2184  <x:ref>Referer-v</x:ref>      = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2185</artwork></figure>
2186<t>
2187   Example:
2188</t>
2189<figure><artwork type="example">
2190  Referer: http://www.example.org/hypertext/Overview.html
2191</artwork></figure>
2192<t>
2193   If the field value is a relative URI, it &SHOULD; be interpreted
2194   relative to the effective request URI. The URI &MUST-NOT; include a fragment. See
2195   <xref target="encoding.sensitive.information.in.uris"/> for security considerations.
2196</t>
2197</section>
2198
2199<section title="Retry-After" anchor="header.retry-after">
2200  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2201  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
2202  <x:anchor-alias value="Retry-After"/>
2203  <x:anchor-alias value="Retry-After-v"/>
2204<t>
2205   The response-header "Retry-After" field can be used with a 503 (Service
2206   Unavailable) response to indicate how long the service is expected to
2207   be unavailable to the requesting client. This field &MAY; also be used
2208   with any 3xx (Redirection) response to indicate the minimum time the
2209   user-agent is asked wait before issuing the redirected request.
2210</t>
2211<t>
2212   The value of this field can be either an HTTP-date or an integer number
2213   of seconds (in decimal) after the time of the response.
2214</t>
2215<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
2216  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
2217  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2218</artwork></figure>
2219<t anchor="rule.delta-seconds">
2220  <x:anchor-alias value="delta-seconds"/>
2221   Time spans are non-negative decimal integers, representing time in
2222   seconds.
2223</t>
2224<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2225  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2226</artwork></figure>
2227<t>
2228   Two examples of its use are
2229</t>
2230<figure><artwork type="example">
2231  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2232  Retry-After: 120
2233</artwork></figure>
2234<t>
2235   In the latter example, the delay is 2 minutes.
2236</t>
2237</section>
2238
2239<section title="Server" anchor="header.server">
2240  <iref primary="true" item="Server header" x:for-anchor=""/>
2241  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
2242  <x:anchor-alias value="Server"/>
2243  <x:anchor-alias value="Server-v"/>
2244<t>
2245   The "Server" response-header field contains information about the
2246   software used by the origin server to handle the request.
2247</t>
2248<t>
2249   The field can contain multiple product tokens (&product-tokens;) and
2250   comments (&header-fields;) identifying the server and any significant
2251   subproducts. The product tokens are listed in order of their significance
2252   for identifying the application.
2253</t>
2254<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
2255  <x:ref>Server</x:ref>         = "Server" ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
2256  <x:ref>Server-v</x:ref>       = <x:ref>product</x:ref>
2257                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2258</artwork></figure>
2259<t>
2260   Example:
2261</t>
2262<figure><artwork type="example">
2263  Server: CERN/3.0 libwww/2.17
2264</artwork></figure>
2265<t>
2266   If the response is being forwarded through a proxy, the proxy
2267   application &MUST-NOT; modify the Server response-header field. Instead, it
2268   &MUST; include a Via field (as described in &header-via;).
2269</t>
2270<x:note>
2271  <t>
2272    <x:h>Note:</x:h> Revealing the specific software version of the server might
2273    allow the server machine to become more vulnerable to attacks
2274    against software that is known to contain security holes. Server
2275    implementors are encouraged to make this field a configurable
2276    option.
2277  </t>
2278</x:note>
2279</section>
2280
2281<section title="User-Agent" anchor="header.user-agent">
2282  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2283  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
2284  <x:anchor-alias value="User-Agent"/>
2285  <x:anchor-alias value="User-Agent-v"/>
2286<t>
2287   The "User-Agent" request-header field contains information about the
2288   user agent originating the request. This is for statistical purposes,
2289   the tracing of protocol violations, and automated recognition of user
2290   agents for the sake of tailoring responses to avoid particular user
2291   agent limitations.
2292</t>
2293<t>
2294   User agents &SHOULD; include this field with requests. The field can contain
2295   multiple product tokens (&product-tokens;) and comments (&header-fields;)
2296   identifying the agent and any subproducts which form a significant part of
2297   the user agent. By convention, the product tokens are listed in order of
2298   their significance for identifying the application.
2299</t>
2300<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
2301  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
2302  <x:ref>User-Agent-v</x:ref>   = <x:ref>product</x:ref>
2303                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2304</artwork></figure>
2305<t>
2306   Example:
2307</t>
2308<figure><artwork type="example">
2309  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2310</artwork></figure>
2311</section>
2312
2313</section>
2314
2315<section title="IANA Considerations" anchor="IANA.considerations">
2316
2317<section title="Method Registry" anchor="method.registration">
2318<t>
2319  The registration procedure for HTTP Methods is defined by
2320  <xref target="method.registry"/> of this document.
2321</t>
2322<t>
2323   The HTTP Method Registry shall be created at <eref target="http://www.iana.org/assignments/http-methods"/>
2324   and be populated with the registrations below:
2325</t>
2326<?BEGININC p2-semantics.iana-methods ?>
2327<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2328<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2329   <ttcol>Method</ttcol>
2330   <ttcol>Safe</ttcol>
2331   <ttcol>Reference</ttcol>
2332   <c>CONNECT</c>
2333   <c>no</c>
2334   <c>
2335      <xref target="CONNECT"/>
2336   </c>
2337   <c>DELETE</c>
2338   <c>no</c>
2339   <c>
2340      <xref target="DELETE"/>
2341   </c>
2342   <c>GET</c>
2343   <c>yes</c>
2344   <c>
2345      <xref target="GET"/>
2346   </c>
2347   <c>HEAD</c>
2348   <c>yes</c>
2349   <c>
2350      <xref target="HEAD"/>
2351   </c>
2352   <c>OPTIONS</c>
2353   <c>yes</c>
2354   <c>
2355      <xref target="OPTIONS"/>
2356   </c>
2357   <c>POST</c>
2358   <c>no</c>
2359   <c>
2360      <xref target="POST"/>
2361   </c>
2362   <c>PUT</c>
2363   <c>no</c>
2364   <c>
2365      <xref target="PUT"/>
2366   </c>
2367   <c>TRACE</c>
2368   <c>yes</c>
2369   <c>
2370      <xref target="TRACE"/>
2371   </c>
2372</texttable>
2373<!--(END)-->
2374<?ENDINC p2-semantics.iana-methods ?>
2375</section>
2376
2377<section title="Status Code Registry" anchor="status.code.registration">
2378<t>
2379   The registration procedure for HTTP Status Codes -- previously defined
2380   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> -- is now defined
2381   by <xref target="status.code.registry"/> of this document.
2382</t>
2383<t>
2384   The HTTP Status Code Registry located at <eref target="http://www.iana.org/assignments/http-status-codes"/>
2385   shall be updated with the registrations below:
2386</t>
2387<?BEGININC p2-semantics.iana-status-codes ?>
2388<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2389<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2390   <ttcol>Value</ttcol>
2391   <ttcol>Description</ttcol>
2392   <ttcol>Reference</ttcol>
2393   <c>100</c>
2394   <c>Continue</c>
2395   <c>
2396      <xref target="status.100"/>
2397   </c>
2398   <c>101</c>
2399   <c>Switching Protocols</c>
2400   <c>
2401      <xref target="status.101"/>
2402   </c>
2403   <c>200</c>
2404   <c>OK</c>
2405   <c>
2406      <xref target="status.200"/>
2407   </c>
2408   <c>201</c>
2409   <c>Created</c>
2410   <c>
2411      <xref target="status.201"/>
2412   </c>
2413   <c>202</c>
2414   <c>Accepted</c>
2415   <c>
2416      <xref target="status.202"/>
2417   </c>
2418   <c>203</c>
2419   <c>Non-Authoritative Information</c>
2420   <c>
2421      <xref target="status.203"/>
2422   </c>
2423   <c>204</c>
2424   <c>No Content</c>
2425   <c>
2426      <xref target="status.204"/>
2427   </c>
2428   <c>205</c>
2429   <c>Reset Content</c>
2430   <c>
2431      <xref target="status.205"/>
2432   </c>
2433   <c>300</c>
2434   <c>Multiple Choices</c>
2435   <c>
2436      <xref target="status.300"/>
2437   </c>
2438   <c>301</c>
2439   <c>Moved Permanently</c>
2440   <c>
2441      <xref target="status.301"/>
2442   </c>
2443   <c>302</c>
2444   <c>Found</c>
2445   <c>
2446      <xref target="status.302"/>
2447   </c>
2448   <c>303</c>
2449   <c>See Other</c>
2450   <c>
2451      <xref target="status.303"/>
2452   </c>
2453   <c>305</c>
2454   <c>Use Proxy</c>
2455   <c>
2456      <xref target="status.305"/>
2457   </c>
2458   <c>306</c>
2459   <c>(Unused)</c>
2460   <c>
2461      <xref target="status.306"/>
2462   </c>
2463   <c>307</c>
2464   <c>Temporary Redirect</c>
2465   <c>
2466      <xref target="status.307"/>
2467   </c>
2468   <c>400</c>
2469   <c>Bad Request</c>
2470   <c>
2471      <xref target="status.400"/>
2472   </c>
2473   <c>402</c>
2474   <c>Payment Required</c>
2475   <c>
2476      <xref target="status.402"/>
2477   </c>
2478   <c>403</c>
2479   <c>Forbidden</c>
2480   <c>
2481      <xref target="status.403"/>
2482   </c>
2483   <c>404</c>
2484   <c>Not Found</c>
2485   <c>
2486      <xref target="status.404"/>
2487   </c>
2488   <c>405</c>
2489   <c>Method Not Allowed</c>
2490   <c>
2491      <xref target="status.405"/>
2492   </c>
2493   <c>406</c>
2494   <c>Not Acceptable</c>
2495   <c>
2496      <xref target="status.406"/>
2497   </c>
2498   <c>407</c>
2499   <c>Proxy Authentication Required</c>
2500   <c>
2501      <xref target="status.407"/>
2502   </c>
2503   <c>408</c>
2504   <c>Request Timeout</c>
2505   <c>
2506      <xref target="status.408"/>
2507   </c>
2508   <c>409</c>
2509   <c>Conflict</c>
2510   <c>
2511      <xref target="status.409"/>
2512   </c>
2513   <c>410</c>
2514   <c>Gone</c>
2515   <c>
2516      <xref target="status.410"/>
2517   </c>
2518   <c>411</c>
2519   <c>Length Required</c>
2520   <c>
2521      <xref target="status.411"/>
2522   </c>
2523   <c>413</c>
2524   <c>Request Entity Too Large</c>
2525   <c>
2526      <xref target="status.413"/>
2527   </c>
2528   <c>414</c>
2529   <c>URI Too Long</c>
2530   <c>
2531      <xref target="status.414"/>
2532   </c>
2533   <c>415</c>
2534   <c>Unsupported Media Type</c>
2535   <c>
2536      <xref target="status.415"/>
2537   </c>
2538   <c>417</c>
2539   <c>Expectation Failed</c>
2540   <c>
2541      <xref target="status.417"/>
2542   </c>
2543   <c>500</c>
2544   <c>Internal Server Error</c>
2545   <c>
2546      <xref target="status.500"/>
2547   </c>
2548   <c>501</c>
2549   <c>Not Implemented</c>
2550   <c>
2551      <xref target="status.501"/>
2552   </c>
2553   <c>502</c>
2554   <c>Bad Gateway</c>
2555   <c>
2556      <xref target="status.502"/>
2557   </c>
2558   <c>503</c>
2559   <c>Service Unavailable</c>
2560   <c>
2561      <xref target="status.503"/>
2562   </c>
2563   <c>504</c>
2564   <c>Gateway Timeout</c>
2565   <c>
2566      <xref target="status.504"/>
2567   </c>
2568   <c>505</c>
2569   <c>HTTP Version Not Supported</c>
2570   <c>
2571      <xref target="status.505"/>
2572   </c>
2573</texttable>
2574<!--(END)-->
2575<?ENDINC p2-semantics.iana-status-codes ?>
2576</section>
2577<section title="Header Field Registration" anchor="header.field.registration">
2578<t>
2579   The Message Header Field Registry located at <eref target="http://www.iana.org/assignments/message-headers/message-header-index.html"/> shall be updated
2580   with the permanent registrations below (see <xref target="RFC3864"/>):
2581</t>
2582<?BEGININC p2-semantics.iana-headers ?>
2583<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2584<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2585   <ttcol>Header Field Name</ttcol>
2586   <ttcol>Protocol</ttcol>
2587   <ttcol>Status</ttcol>
2588   <ttcol>Reference</ttcol>
2589
2590   <c>Allow</c>
2591   <c>http</c>
2592   <c>standard</c>
2593   <c>
2594      <xref target="header.allow"/>
2595   </c>
2596   <c>Expect</c>
2597   <c>http</c>
2598   <c>standard</c>
2599   <c>
2600      <xref target="header.expect"/>
2601   </c>
2602   <c>From</c>
2603   <c>http</c>
2604   <c>standard</c>
2605   <c>
2606      <xref target="header.from"/>
2607   </c>
2608   <c>Location</c>
2609   <c>http</c>
2610   <c>standard</c>
2611   <c>
2612      <xref target="header.location"/>
2613   </c>
2614   <c>Max-Forwards</c>
2615   <c>http</c>
2616   <c>standard</c>
2617   <c>
2618      <xref target="header.max-forwards"/>
2619   </c>
2620   <c>Referer</c>
2621   <c>http</c>
2622   <c>standard</c>
2623   <c>
2624      <xref target="header.referer"/>
2625   </c>
2626   <c>Retry-After</c>
2627   <c>http</c>
2628   <c>standard</c>
2629   <c>
2630      <xref target="header.retry-after"/>
2631   </c>
2632   <c>Server</c>
2633   <c>http</c>
2634   <c>standard</c>
2635   <c>
2636      <xref target="header.server"/>
2637   </c>
2638   <c>User-Agent</c>
2639   <c>http</c>
2640   <c>standard</c>
2641   <c>
2642      <xref target="header.user-agent"/>
2643   </c>
2644</texttable>
2645<!--(END)-->
2646<?ENDINC p2-semantics.iana-headers ?>
2647<t>
2648   The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".
2649</t>
2650</section>
2651</section>
2652
2653<section title="Security Considerations" anchor="security.considerations">
2654<t>
2655   This section is meant to inform application developers, information
2656   providers, and users of the security limitations in HTTP/1.1 as
2657   described by this document. The discussion does not include
2658   definitive solutions to the problems revealed, though it does make
2659   some suggestions for reducing security risks.
2660</t>
2661
2662<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2663<t>
2664   Like any generic data transfer protocol, HTTP cannot regulate the
2665   content of the data that is transferred, nor is there any a priori
2666   method of determining the sensitivity of any particular piece of
2667   information within the context of any given request. Therefore,
2668   applications &SHOULD; supply as much control over this information as
2669   possible to the provider of that information. Four header fields are
2670   worth special mention in this context: Server, Via, Referer and From.
2671</t>
2672<t>
2673   Revealing the specific software version of the server might allow the
2674   server machine to become more vulnerable to attacks against software
2675   that is known to contain security holes. Implementors &SHOULD; make the
2676   Server header field a configurable option.
2677</t>
2678<t>
2679   Proxies which serve as a portal through a network firewall &SHOULD;
2680   take special precautions regarding the transfer of header information
2681   that identifies the hosts behind the firewall. In particular, they
2682   &SHOULD; remove, or replace with sanitized versions, any Via fields
2683   generated behind the firewall.
2684</t>
2685<t>
2686   The Referer header field allows reading patterns to be studied and reverse
2687   links drawn. Although it can be very useful, its power can be abused
2688   if user details are not separated from the information contained in
2689   the Referer. Even when the personal information has been removed, the
2690   Referer header field might indicate a private document's URI whose
2691   publication would be inappropriate.
2692</t>
2693<t>
2694   The information sent in the From field might conflict with the user's
2695   privacy interests or their site's security policy, and hence it
2696   &SHOULD-NOT;  be transmitted without the user being able to disable,
2697   enable, and modify the contents of the field. The user &MUST; be able
2698   to set the contents of this field within a user preference or
2699   application defaults configuration.
2700</t>
2701<t>
2702   We suggest, though do not require, that a convenient toggle interface
2703   be provided for the user to enable or disable the sending of From and
2704   Referer information.
2705</t>
2706<t>
2707   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2708   fields can sometimes be used to determine that a specific client or
2709   server have a particular security hole which might be exploited.
2710   Unfortunately, this same information is often used for other valuable
2711   purposes for which HTTP currently has no better mechanism.
2712</t>
2713<t>
2714   Some methods, like TRACE (<xref target="TRACE"/>), expose information
2715   that was sent in request header fields within the body of their response.
2716   Clients &SHOULD; be careful with sensitive information, like Cookies,
2717   Authorization credentials and other header fields that might be used to
2718   collect data from the client.
2719</t> 
2720</section>
2721
2722<section title="Encoding Sensitive Information in URIs" anchor="encoding.sensitive.information.in.uris">
2723<t>
2724   Because the source of a link might be private information or might
2725   reveal an otherwise private information source, it is strongly
2726   recommended that the user be able to select whether or not the
2727   Referer field is sent. For example, a browser client could have a
2728   toggle switch for browsing openly/anonymously, which would
2729   respectively enable/disable the sending of Referer and From
2730   information.
2731</t>
2732<t>
2733   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2734   HTTP request if the referring page was transferred with a secure
2735   protocol.
2736</t>
2737<t>
2738   Authors of services &SHOULD-NOT; use GET-based forms for the submission of
2739   sensitive data because that data will be placed in the request-target. Many
2740   existing servers, proxies, and user agents log or display the request-target
2741   in places where it might be visible to third parties. Such services can
2742   use POST-based form submission instead.
2743</t>
2744</section>
2745
2746<section title="Location Headers and Spoofing" anchor="location.spoofing">
2747<t>
2748   If a single server supports multiple organizations that do not trust
2749   one another, then it &MUST; check the values of Location and Content-Location
2750   header fields in responses that are generated under control of
2751   said organizations to make sure that they do not attempt to
2752   invalidate resources over which they have no authority.
2753</t>
2754</section>
2755
2756</section>
2757
2758<section title="Acknowledgments" anchor="ack">
2759</section>
2760</middle>
2761<back>
2762
2763<references title="Normative References">
2764
2765<reference anchor="Part1">
2766  <front>
2767    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2768    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2769      <organization abbrev="Day Software">Day Software</organization>
2770      <address><email>fielding@gbiv.com</email></address>
2771    </author>
2772    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2773      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2774      <address><email>jg@freedesktop.org</email></address>
2775    </author>
2776    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2777      <organization abbrev="HP">Hewlett-Packard Company</organization>
2778      <address><email>JeffMogul@acm.org</email></address>
2779    </author>
2780    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2781      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2782      <address><email>henrikn@microsoft.com</email></address>
2783    </author>
2784    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2785      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2786      <address><email>LMM@acm.org</email></address>
2787    </author>
2788    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2789      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2790      <address><email>paulle@microsoft.com</email></address>
2791    </author>
2792    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2793      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2794      <address><email>timbl@w3.org</email></address>
2795    </author>
2796    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2797      <organization abbrev="W3C">World Wide Web Consortium</organization>
2798      <address><email>ylafon@w3.org</email></address>
2799    </author>
2800    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2801      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2802      <address><email>julian.reschke@greenbytes.de</email></address>
2803    </author>
2804    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2805  </front>
2806  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2807  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2808</reference>
2809
2810<reference anchor="Part3">
2811  <front>
2812    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2813    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2814      <organization abbrev="Day Software">Day Software</organization>
2815      <address><email>fielding@gbiv.com</email></address>
2816    </author>
2817    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2818      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2819      <address><email>jg@freedesktop.org</email></address>
2820    </author>
2821    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2822      <organization abbrev="HP">Hewlett-Packard Company</organization>
2823      <address><email>JeffMogul@acm.org</email></address>
2824    </author>
2825    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2826      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2827      <address><email>henrikn@microsoft.com</email></address>
2828    </author>
2829    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2830      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2831      <address><email>LMM@acm.org</email></address>
2832    </author>
2833    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2834      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2835      <address><email>paulle@microsoft.com</email></address>
2836    </author>
2837    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2838      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2839      <address><email>timbl@w3.org</email></address>
2840    </author>
2841    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2842      <organization abbrev="W3C">World Wide Web Consortium</organization>
2843      <address><email>ylafon@w3.org</email></address>
2844    </author>
2845    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2846      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2847      <address><email>julian.reschke@greenbytes.de</email></address>
2848    </author>
2849    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2850  </front>
2851  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2852  <x:source href="p3-payload.xml" basename="p3-payload"/>
2853</reference>
2854
2855<reference anchor="Part4">
2856  <front>
2857    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2858    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2859      <organization abbrev="Day Software">Day Software</organization>
2860      <address><email>fielding@gbiv.com</email></address>
2861    </author>
2862    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2863      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2864      <address><email>jg@freedesktop.org</email></address>
2865    </author>
2866    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2867      <organization abbrev="HP">Hewlett-Packard Company</organization>
2868      <address><email>JeffMogul@acm.org</email></address>
2869    </author>
2870    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2871      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2872      <address><email>henrikn@microsoft.com</email></address>
2873    </author>
2874    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2875      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2876      <address><email>LMM@acm.org</email></address>
2877    </author>
2878    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2879      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2880      <address><email>paulle@microsoft.com</email></address>
2881    </author>
2882    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2883      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2884      <address><email>timbl@w3.org</email></address>
2885    </author>
2886    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2887      <organization abbrev="W3C">World Wide Web Consortium</organization>
2888      <address><email>ylafon@w3.org</email></address>
2889    </author>
2890    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2891      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2892      <address><email>julian.reschke@greenbytes.de</email></address>
2893    </author>
2894    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2895  </front>
2896  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2897  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2898</reference>
2899
2900<reference anchor="Part5">
2901  <front>
2902    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2903    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2904      <organization abbrev="Day Software">Day Software</organization>
2905      <address><email>fielding@gbiv.com</email></address>
2906    </author>
2907    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2908      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2909      <address><email>jg@freedesktop.org</email></address>
2910    </author>
2911    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2912      <organization abbrev="HP">Hewlett-Packard Company</organization>
2913      <address><email>JeffMogul@acm.org</email></address>
2914    </author>
2915    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2916      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2917      <address><email>henrikn@microsoft.com</email></address>
2918    </author>
2919    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2920      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2921      <address><email>LMM@acm.org</email></address>
2922    </author>
2923    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2924      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2925      <address><email>paulle@microsoft.com</email></address>
2926    </author>
2927    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2928      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2929      <address><email>timbl@w3.org</email></address>
2930    </author>
2931    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2932      <organization abbrev="W3C">World Wide Web Consortium</organization>
2933      <address><email>ylafon@w3.org</email></address>
2934    </author>
2935    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2936      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2937      <address><email>julian.reschke@greenbytes.de</email></address>
2938    </author>
2939    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2940  </front>
2941  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
2942  <x:source href="p5-range.xml" basename="p5-range"/>
2943</reference>
2944
2945<reference anchor="Part6">
2946  <front>
2947    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2948    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2949      <organization abbrev="Day Software">Day Software</organization>
2950      <address><email>fielding@gbiv.com</email></address>
2951    </author>
2952    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2953      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
2954      <address><email>jg@freedesktop.org</email></address>
2955    </author>
2956    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2957      <organization abbrev="HP">Hewlett-Packard Company</organization>
2958      <address><email>JeffMogul@acm.org</email></address>
2959    </author>
2960    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2961      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2962      <address><email>henrikn@microsoft.com</email></address>
2963    </author>
2964    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2965      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2966      <address><email>LMM@acm.org</email></address>
2967    </author>
2968    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2969      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2970      <address><email>paulle@microsoft.com</email></address>
2971    </author>
2972    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2973      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2974      <address><email>timbl@w3.org</email></address>
2975    </author>
2976    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2977      <organization abbrev="W3C">World Wide Web Consortium</organization>
2978      <address><email>ylafon@w3.org</email></address>
2979    </author>
2980    <author initials="M." surname="Nottingham" fullname="Mark Nottingham" role="editor">
2981      <address><email>mnot@mnot.net</email></address>
2982    </author>
2983    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2984      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2985      <address><email>julian.reschke@greenbytes.de</email></address>
2986    </author>
2987    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2988  </front>
2989  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2990  <x:source href="p6-cache.xml" basename="p6-cache"/>
2991</reference>
2992
2993<reference anchor="Part7">
2994  <front>
2995    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2996    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2997      <organization abbrev="Day Software">Day Software</organization>
2998      <address><email>fielding@gbiv.com</email></address>
2999    </author>
3000    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3001      <organization abbrev="Alcatel-Lucent">Alcatel-Lucent Bell Labs</organization>
3002      <address><email>jg@freedesktop.org</email></address>
3003    </author>
3004    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3005      <organization abbrev="HP">Hewlett-Packard Company</organization>
3006      <address><email>JeffMogul@acm.org</email></address>
3007    </author>
3008    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
3009      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3010      <address><email>henrikn@microsoft.com</email></address>
3011    </author>
3012    <author initials="L." surname="Masinter" fullname="Larry Masinter">
3013      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
3014      <address><email>LMM@acm.org</email></address>
3015    </author>
3016    <author initials="P." surname="Leach" fullname="Paul J. Leach">
3017      <organization abbrev="Microsoft">Microsoft Corporation</organization>
3018      <address><email>paulle@microsoft.com</email></address>
3019    </author>
3020    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3021      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3022      <address><email>timbl@w3.org</email></address>
3023    </author>
3024    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
3025      <organization abbrev="W3C">World Wide Web Consortium</organization>
3026      <address><email>ylafon@w3.org</email></address>
3027    </author>
3028    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
3029      <organization abbrev="greenbytes">greenbytes GmbH</organization>
3030      <address><email>julian.reschke@greenbytes.de</email></address>
3031    </author>
3032    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
3033  </front>
3034  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
3035  <x:source href="p7-auth.xml" basename="p7-auth"/>
3036</reference>
3037
3038<reference anchor="RFC2119">
3039  <front>
3040    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
3041    <author initials="S." surname="Bradner" fullname="Scott Bradner">
3042      <organization>Harvard University</organization>
3043      <address><email>sob@harvard.edu</email></address>
3044    </author>
3045    <date month="March" year="1997"/>
3046  </front>
3047  <seriesInfo name="BCP" value="14"/>
3048  <seriesInfo name="RFC" value="2119"/>
3049</reference>
3050
3051<reference anchor="RFC3986">
3052 <front>
3053  <title abbrev='URI Generic Syntax'>Uniform Resource Identifier (URI): Generic Syntax</title>
3054  <author initials='T.' surname='Berners-Lee' fullname='Tim Berners-Lee'>
3055    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
3056    <address>
3057       <email>timbl@w3.org</email>
3058       <uri>http://www.w3.org/People/Berners-Lee/</uri>
3059    </address>
3060  </author>
3061  <author initials='R.' surname='Fielding' fullname='Roy T. Fielding'>
3062    <organization abbrev="Day Software">Day Software</organization>
3063    <address>
3064      <email>fielding@gbiv.com</email>
3065      <uri>http://roy.gbiv.com/</uri>
3066    </address>
3067  </author>
3068  <author initials='L.' surname='Masinter' fullname='Larry Masinter'>
3069    <organization abbrev="Adobe Systems">Adobe Systems Incorporated</organization>
3070    <address>
3071      <email>LMM@acm.org</email>
3072      <uri>http://larry.masinter.net/</uri>
3073    </address>
3074  </author>
3075  <date month='January' year='2005'></date>
3076 </front>
3077 <seriesInfo name="STD" value="66"/>
3078 <seriesInfo name="RFC" value="3986"/>
3079</reference>
3080
3081<reference anchor="RFC5234">
3082  <front>
3083    <title abbrev="ABNF for Syntax Specifications">Augmented BNF for Syntax Specifications: ABNF</title>
3084    <author initials="D." surname="Crocker" fullname="Dave Crocker" role="editor">
3085      <organization>Brandenburg InternetWorking</organization>
3086      <address>
3087        <email>dcrocker@bbiw.net</email>
3088      </address> 
3089    </author>
3090    <author initials="P." surname="Overell" fullname="Paul Overell">
3091      <organization>THUS plc.</organization>
3092      <address>
3093        <email>paul.overell@thus.net</email>
3094      </address>
3095    </author>
3096    <date month="January" year="2008"/>
3097  </front>
3098  <seriesInfo name="STD" value="68"/>
3099  <seriesInfo name="RFC" value="5234"/>
3100</reference>
3101
3102</references>
3103
3104<references title="Informative References">
3105
3106<reference anchor="RFC1945">
3107  <front>
3108    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
3109    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3110      <organization>MIT, Laboratory for Computer Science</organization>
3111      <address><email>timbl@w3.org</email></address>
3112    </author>
3113    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
3114      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3115      <address><email>fielding@ics.uci.edu</email></address>
3116    </author>
3117    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3118      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
3119      <address><email>frystyk@w3.org</email></address>
3120    </author>
3121    <date month="May" year="1996"/>
3122  </front>
3123  <seriesInfo name="RFC" value="1945"/>
3124</reference>
3125
3126<reference anchor="RFC2068">
3127  <front>
3128    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
3129    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
3130      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
3131      <address><email>fielding@ics.uci.edu</email></address>
3132    </author>
3133    <author initials="J." surname="Gettys" fullname="Jim Gettys">
3134      <organization>MIT Laboratory for Computer Science</organization>
3135      <address><email>jg@w3.org</email></address>
3136    </author>
3137    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
3138      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
3139      <address><email>mogul@wrl.dec.com</email></address>
3140    </author>
3141    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
3142      <organization>MIT Laboratory for Computer Science</organization>
3143      <address><email>frystyk@w3.org</email></address>
3144    </author>
3145    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
3146      <organization>MIT Laboratory for Computer Science</organization>
3147      <address><email>timbl@w3.org</email></address>
3148    </author>
3149    <date month="January" year="1997"/>
3150  </front>
3151  <seriesInfo name="RFC" value="2068"/>
3152</reference>
3153
3154<reference anchor="RFC2616">
3155  <front>
3156    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
3157    <author initials="R." surname="Fielding" fullname="R. Fielding">
3158      <organization>University of California, Irvine</organization>
3159      <address><email>fielding@ics.uci.edu</email></address>
3160    </author>
3161    <author initials="J." surname="Gettys" fullname="J. Gettys">
3162      <organization>W3C</organization>
3163      <address><email>jg@w3.org</email></address>
3164    </author>
3165    <author initials="J." surname="Mogul" fullname="J. Mogul">
3166      <organization>Compaq Computer Corporation</organization>
3167      <address><email>mogul@wrl.dec.com</email></address>
3168    </author>
3169    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
3170      <organization>MIT Laboratory for Computer Science</organization>
3171      <address><email>frystyk@w3.org</email></address>
3172    </author>
3173    <author initials="L." surname="Masinter" fullname="L. Masinter">
3174      <organization>Xerox Corporation</organization>
3175      <address><email>masinter@parc.xerox.com</email></address>
3176    </author>
3177    <author initials="P." surname="Leach" fullname="P. Leach">
3178      <organization>Microsoft Corporation</organization>
3179      <address><email>paulle@microsoft.com</email></address>
3180    </author>
3181    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
3182      <organization>W3C</organization>
3183      <address><email>timbl@w3.org</email></address>
3184    </author>
3185    <date month="June" year="1999"/>
3186  </front>
3187  <seriesInfo name="RFC" value="2616"/>
3188</reference>
3189
3190<reference anchor='RFC2817'>
3191  <front>
3192    <title>Upgrading to TLS Within HTTP/1.1</title>
3193    <author initials='R.' surname='Khare' fullname='R. Khare'>
3194      <organization>4K Associates / UC Irvine</organization>
3195      <address><email>rohit@4K-associates.com</email></address>
3196    </author>
3197    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3198      <organization>Agranat Systems, Inc.</organization>
3199      <address><email>lawrence@agranat.com</email></address>
3200    </author>
3201    <date year='2000' month='May' />
3202  </front>
3203  <seriesInfo name='RFC' value='2817' />
3204</reference>
3205
3206<reference anchor='RFC3864'>
3207  <front>
3208    <title>Registration Procedures for Message Header Fields</title>
3209    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3210      <organization>Nine by Nine</organization>
3211      <address><email>GK-IETF@ninebynine.org</email></address>
3212    </author>
3213    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3214      <organization>BEA Systems</organization>
3215      <address><email>mnot@pobox.com</email></address>
3216    </author>
3217    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3218      <organization>HP Labs</organization>
3219      <address><email>JeffMogul@acm.org</email></address>
3220    </author>
3221    <date year='2004' month='September' />
3222  </front>
3223  <seriesInfo name='BCP' value='90' />
3224  <seriesInfo name='RFC' value='3864' />
3225</reference>
3226
3227<reference anchor='RFC5226'>
3228  <front>
3229    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3230    <author initials='T.' surname='Narten' fullname='T. Narten'>
3231      <organization>IBM</organization>
3232      <address><email>narten@us.ibm.com</email></address>
3233    </author>
3234    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3235      <organization>Google</organization>
3236      <address><email>Harald@Alvestrand.no</email></address>
3237    </author>
3238    <date year='2008' month='May' />
3239  </front>
3240  <seriesInfo name='BCP' value='26' />
3241  <seriesInfo name='RFC' value='5226' />
3242</reference>
3243
3244<reference anchor="RFC5322">
3245  <front>
3246    <title>Internet Message Format</title>
3247    <author initials="P." surname="Resnick" fullname="P. Resnick">
3248      <organization>Qualcomm Incorporated</organization>
3249    </author>
3250    <date year="2008" month="October"/>
3251  </front> 
3252  <seriesInfo name="RFC" value="5322"/>
3253</reference>
3254
3255</references>
3256
3257<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3258<t>
3259  This document takes over the Status Code Registry, previously defined
3260  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3261  (<xref target="status.code.registry"/>)
3262</t>
3263<t>
3264  Clarify definition of POST.
3265  (<xref target="POST"/>)
3266</t>
3267<t>
3268  Failed to consider that there are
3269  many other request methods that are safe to automatically redirect,
3270  and further that the user agent is able to make that determination
3271  based on the request method semantics.
3272  (Sections <xref format="counter" target="status.301"/>,
3273  <xref format="counter" target="status.302"/> and
3274  <xref format="counter" target="status.307"/>)
3275</t>
3276<t>
3277  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3278  It used to indicate that the target resource must be accessed through the
3279  proxy given by the Location field. The Location field gave the URI of the
3280  proxy. The recipient was expected to repeat this single request via the proxy.
3281  (<xref target="status.305"/>)
3282</t>
3283<t>
3284  Reclassify "Allow" as response header field, removing the option to
3285  specify it in a PUT request.
3286  Relax the server requirement on the contents of the Allow header field and
3287  remove requirement on clients to always trust the header field value.
3288  (<xref target="header.allow"/>)
3289</t>
3290<t>
3291  Correct syntax of Location header field to allow URI references (including
3292  relative references and fragments), as referred symbol "absoluteURI" wasn't
3293  what was expected, and add some clarifications as to when use of fragments
3294  would not be appropriate.
3295  (<xref target="header.location"/>)
3296</t>
3297<t>
3298  Allow Referer field value of "about:blank" as alternative to not specifying it.
3299  (<xref target="header.referer"/>)
3300</t>
3301<t>
3302  In the description of the Server header field, the Via field
3303  was described as a SHOULD. The requirement was and is stated
3304  correctly in the description of the Via header field in &header-via;.
3305  (<xref target="header.server"/>)
3306</t>
3307</section>
3308
3309<?BEGININC p2-semantics.abnf-appendix ?>
3310<section xmlns:x="http://purl.org/net/xml2rfc/ext" title="Collected ABNF" anchor="collected.abnf">
3311<figure>
3312<artwork type="abnf" name="p2-semantics.parsed-abnf">
3313<x:ref>Accept</x:ref> = &lt;Accept, defined in [Part3], Section 6.1&gt;
3314<x:ref>Accept-Charset</x:ref> = &lt;Accept-Charset, defined in [Part3], Section 6.2&gt;
3315<x:ref>Accept-Encoding</x:ref> = &lt;Accept-Encoding, defined in [Part3], Section 6.3&gt;
3316<x:ref>Accept-Language</x:ref> = &lt;Accept-Language, defined in [Part3], Section 6.4&gt;
3317<x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in [Part5], Section 5.1&gt;
3318<x:ref>Age</x:ref> = &lt;Age, defined in [Part6], Section 3.1&gt;
3319<x:ref>Allow</x:ref> = "Allow:" OWS Allow-v
3320<x:ref>Allow-v</x:ref> = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
3321<x:ref>Authorization</x:ref> = &lt;Authorization, defined in [Part7], Section 4.1&gt;
3322
3323<x:ref>ETag</x:ref> = &lt;ETag, defined in [Part4], Section 6.1&gt;
3324<x:ref>Expect</x:ref> = "Expect:" OWS Expect-v
3325<x:ref>Expect-v</x:ref> = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
3326
3327<x:ref>From</x:ref> = "From:" OWS From-v
3328<x:ref>From-v</x:ref> = mailbox
3329
3330<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part1], Section 6.1&gt;
3331<x:ref>Host</x:ref> = &lt;Host, defined in [Part1], Section 2.6&gt;
3332
3333<x:ref>If-Match</x:ref> = &lt;If-Match, defined in [Part4], Section 6.2&gt;
3334If-Modified-Since =
3335 &lt;If-Modified-Since, defined in [Part4], Section 6.3&gt;
3336<x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in [Part4], Section 6.4&gt;
3337<x:ref>If-Range</x:ref> = &lt;If-Range, defined in [Part5], Section 5.3&gt;
3338If-Unmodified-Since =
3339 &lt;If-Unmodified-Since, defined in [Part4], Section 6.5&gt;
3340
3341<x:ref>Location</x:ref> = "Location:" OWS Location-v
3342<x:ref>Location-v</x:ref> = URI-reference
3343
3344<x:ref>Max-Forwards</x:ref> = "Max-Forwards:" OWS Max-Forwards-v
3345<x:ref>Max-Forwards-v</x:ref> = 1*DIGIT
3346<x:ref>Method</x:ref> = %x4F.50.54.49.4F.4E.53 ; OPTIONS
3347 / %x47.45.54 ; GET
3348 / %x48.45.41.44 ; HEAD
3349 / %x50.4F.53.54 ; POST
3350 / %x50.55.54 ; PUT
3351 / %x44.45.4C.45.54.45 ; DELETE
3352 / %x54.52.41.43.45 ; TRACE
3353 / %x43.4F.4E.4E.45.43.54 ; CONNECT
3354 / extension-method
3355
3356<x:ref>OWS</x:ref> = &lt;OWS, defined in [Part1], Section 1.2.2&gt;
3357
3358Proxy-Authenticate =
3359 &lt;Proxy-Authenticate, defined in [Part7], Section 4.2&gt;
3360Proxy-Authorization =
3361 &lt;Proxy-Authorization, defined in [Part7], Section 4.3&gt;
3362
3363<x:ref>RWS</x:ref> = &lt;RWS, defined in [Part1], Section 1.2.2&gt;
3364<x:ref>Range</x:ref> = &lt;Range, defined in [Part5], Section 5.4&gt;
3365<x:ref>Reason-Phrase</x:ref> = *( WSP / VCHAR / obs-text )
3366<x:ref>Referer</x:ref> = "Referer:" OWS Referer-v
3367<x:ref>Referer-v</x:ref> = absolute-URI / partial-URI
3368<x:ref>Retry-After</x:ref> = "Retry-After:" OWS Retry-After-v
3369<x:ref>Retry-After-v</x:ref> = HTTP-date / delta-seconds
3370
3371<x:ref>Server</x:ref> = "Server:" OWS Server-v
3372<x:ref>Server-v</x:ref> = product *( RWS ( product / comment ) )
3373<x:ref>Status-Code</x:ref> = "100" / "101" / "200" / "201" / "202" / "203" / "204" /
3374 "205" / "206" / "300" / "301" / "302" / "303" / "304" / "305" /
3375 "307" / "400" / "401" / "402" / "403" / "404" / "405" / "406" /
3376 "407" / "408" / "409" / "410" / "411" / "412" / "413" / "414" /
3377 "415" / "416" / "417" / "500" / "501" / "502" / "503" / "504" /
3378 "505" / extension-code
3379
3380<x:ref>TE</x:ref> = &lt;TE, defined in [Part1], Section 9.5&gt;
3381
3382<x:ref>URI-reference</x:ref> = &lt;URI-reference, defined in [Part1], Section 2.6&gt;
3383<x:ref>User-Agent</x:ref> = "User-Agent:" OWS User-Agent-v
3384<x:ref>User-Agent-v</x:ref> = product *( RWS ( product / comment ) )
3385
3386<x:ref>Vary</x:ref> = &lt;Vary, defined in [Part6], Section 3.5&gt;
3387
3388WWW-Authenticate =
3389 &lt;WWW-Authenticate, defined in [Part7], Section 4.4&gt;
3390
3391<x:ref>absolute-URI</x:ref> = &lt;absolute-URI, defined in [Part1], Section 2.6&gt;
3392
3393<x:ref>comment</x:ref> = &lt;comment, defined in [Part1], Section 3.2&gt;
3394
3395<x:ref>delta-seconds</x:ref> = 1*DIGIT
3396
3397<x:ref>expect-params</x:ref> = ";" token [ "=" ( token / quoted-string ) ]
3398<x:ref>expectation</x:ref> = "100-continue" / expectation-extension
3399<x:ref>expectation-extension</x:ref> = token [ "=" ( token / quoted-string )
3400 *expect-params ]
3401<x:ref>extension-code</x:ref> = 3DIGIT
3402<x:ref>extension-method</x:ref> = token
3403
3404<x:ref>mailbox</x:ref> = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;
3405
3406<x:ref>obs-text</x:ref> = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;
3407
3408<x:ref>partial-URI</x:ref> = &lt;partial-URI, defined in [Part1], Section 2.6&gt;
3409<x:ref>product</x:ref> = &lt;product, defined in [Part1], Section 6.3&gt;
3410
3411<x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;
3412
3413<x:ref>request-header</x:ref> = Accept / Accept-Charset / Accept-Encoding /
3414 Accept-Language / Authorization / Expect / From / Host / If-Match /
3415 If-Modified-Since / If-None-Match / If-Range / If-Unmodified-Since /
3416 Max-Forwards / Proxy-Authorization / Range / Referer / TE /
3417 User-Agent
3418<x:ref>response-header</x:ref> = Accept-Ranges / Age / Allow / ETag / Location /
3419 Proxy-Authenticate / Retry-After / Server / Vary / WWW-Authenticate
3420
3421<x:ref>token</x:ref> = &lt;token, defined in [Part1], Section 1.2.2&gt;
3422</artwork>
3423</figure>
3424<figure><preamble>ABNF diagnostics:</preamble><artwork type="inline">
3425; Reason-Phrase defined but not used
3426; Status-Code defined but not used
3427; request-header defined but not used
3428; response-header defined but not used
3429</artwork></figure></section>
3430<?ENDINC p2-semantics.abnf-appendix ?>
3431
3432<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3433
3434<section title="Since RFC 2616">
3435<t>
3436  Extracted relevant partitions from <xref target="RFC2616"/>.
3437</t>
3438</section>
3439
3440<section title="Since draft-ietf-httpbis-p2-semantics-00">
3441<t>
3442  Closed issues:
3443  <list style="symbols"> 
3444    <t>
3445      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/5"/>:
3446      "Via is a MUST"
3447      (<eref target="http://purl.org/NET/http-errata#via-must"/>)
3448    </t>
3449    <t>
3450      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/6"/>:
3451      "Fragments allowed in Location"
3452      (<eref target="http://purl.org/NET/http-errata#location-fragments"/>)
3453    </t>
3454    <t>
3455      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3456      "Safe Methods vs Redirection"
3457      (<eref target="http://purl.org/NET/http-errata#saferedirect"/>)
3458    </t>
3459    <t>
3460      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/17"/>:
3461      "Revise description of the POST method"
3462      (<eref target="http://purl.org/NET/http-errata#post"/>)
3463    </t>
3464    <t>
3465      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/35"/>:
3466      "Normative and Informative references"
3467    </t>
3468    <t>
3469      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/42"/>:
3470      "RFC2606 Compliance"
3471    </t>
3472    <t>
3473      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/65"/>:
3474      "Informative references"
3475    </t>
3476    <t>
3477      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/84"/>:
3478      "Redundant cross-references"
3479    </t>
3480  </list>
3481</t>
3482<t>
3483  Other changes:
3484  <list style="symbols"> 
3485    <t>
3486      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3487    </t>
3488  </list>
3489</t>
3490</section>
3491
3492<section title="Since draft-ietf-httpbis-p2-semantics-01">
3493<t>
3494  Closed issues:
3495  <list style="symbols"> 
3496    <t>
3497      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/21"/>:
3498      "PUT side effects"
3499    </t>
3500    <t>
3501      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/91"/>:
3502      "Duplicate Host header requirements"
3503    </t>
3504  </list>
3505</t>
3506<t>
3507  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3508  <list style="symbols"> 
3509    <t>
3510      Move "Product Tokens" section (back) into Part 1, as "token" is used
3511      in the definition of the Upgrade header field.
3512    </t>
3513    <t>
3514      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3515    </t>
3516    <t>
3517      Copy definition of delta-seconds from Part6 instead of referencing it.
3518    </t>
3519  </list>
3520</t>
3521</section>
3522
3523<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3524<t>
3525  Closed issues:
3526  <list style="symbols"> 
3527    <t>
3528      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/24"/>:
3529      "Requiring Allow in 405 responses"
3530    </t>
3531    <t>
3532      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/59"/>:
3533      "Status Code Registry"
3534    </t>
3535    <t>
3536      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/61"/>:
3537      "Redirection vs. Location"
3538    </t>
3539    <t>
3540      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/70"/>:
3541      "Cacheability of 303 response"
3542    </t>
3543    <t>
3544      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/76"/>:
3545      "305 Use Proxy"
3546    </t>
3547    <t>
3548      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/105"/>:
3549      "Classification for Allow header"
3550    </t>
3551    <t>
3552      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/112"/>:
3553      "PUT - 'store under' vs 'store at'"
3554    </t>
3555  </list>
3556</t>
3557<t>
3558  Ongoing work on IANA Message Header Field Registration (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/40"/>):
3559  <list style="symbols"> 
3560    <t>
3561      Reference RFC 3984, and update header field registrations for headers defined
3562      in this document.
3563    </t>
3564  </list>
3565</t>
3566<t>
3567  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3568  <list style="symbols"> 
3569    <t>
3570      Replace string literals when the string really is case-sensitive (method).
3571    </t>
3572  </list>
3573</t>
3574</section>
3575
3576<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3577<t>
3578  Closed issues:
3579  <list style="symbols"> 
3580    <t>
3581      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/98"/>:
3582      "OPTIONS request bodies"
3583    </t>
3584    <t>
3585      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/119"/>:
3586      "Description of CONNECT should refer to RFC2817"
3587    </t>
3588    <t>
3589      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/125"/>:
3590      "Location Content-Location reference request/response mixup"
3591    </t>
3592  </list>
3593</t>
3594<t>
3595  Ongoing work on Method Registry (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/72"/>):
3596  <list style="symbols"> 
3597    <t>
3598      Added initial proposal for registration process, plus initial
3599      content (non-HTTP/1.1 methods to be added by a separate specification).
3600    </t>
3601  </list>
3602</t>
3603</section>
3604
3605<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3606<t>
3607  Closed issues:
3608  <list style="symbols"> 
3609    <t>
3610      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/103"/>:
3611      "Content-*"
3612    </t>
3613    <t>
3614      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/132"/>:
3615      "RFC 2822 is updated by RFC 5322"
3616    </t>
3617  </list>
3618</t>
3619<t>
3620  Ongoing work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3621  <list style="symbols"> 
3622    <t>
3623      Use "/" instead of "|" for alternatives.
3624    </t>
3625    <t>
3626      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3627      whitespace ("OWS") and required whitespace ("RWS").
3628    </t>
3629    <t>
3630      Rewrite ABNFs to spell out whitespace rules, factor out
3631      header field value format definitions.
3632    </t>
3633  </list>
3634</t>
3635</section>
3636
3637<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3638<t>
3639  Closed issues:
3640  <list style="symbols"> 
3641    <t>
3642      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/94"/>:
3643      "Reason-Phrase BNF"
3644    </t>
3645  </list>
3646</t>
3647<t>
3648  Final work on ABNF conversion (<eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/36"/>):
3649  <list style="symbols"> 
3650    <t>
3651      Add appendix containing collected and expanded ABNF, reorganize ABNF introduction.
3652    </t>
3653  </list>
3654</t>
3655</section>
3656
3657<section title="Since draft-ietf-httpbis-p2-semantics-06" anchor="changes.since.06">
3658<t>
3659  Closed issues:
3660  <list style="symbols"> 
3661    <t>
3662      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/144"/>:
3663      "Clarify when Referer is sent"
3664    </t>
3665    <t>
3666      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/164"/>:
3667      "status codes vs methods"
3668    </t>
3669    <t>
3670      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/170"/>:
3671      "Do not require "updates" relation for specs that register status codes or method names"
3672    </t>
3673  </list>
3674</t>
3675</section>
3676
3677<section title="Since draft-ietf-httpbis-p2-semantics-07" anchor="changes.since.07">
3678<t>
3679  Closed issues:
3680  <list style="symbols"> 
3681    <t>
3682      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/27"/>:
3683      "Idempotency"
3684    </t>
3685    <t>
3686      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/33"/>:
3687      "TRACE security considerations"
3688    </t>
3689    <t>
3690      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/110"/>:
3691      "Clarify rules for determining what entities a response carries"
3692    </t>
3693    <t>
3694      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/140"/>:
3695      "update note citing RFC 1945 and 2068"
3696    </t>
3697    <t>
3698      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/182"/>:
3699      "update note about redirect limit"
3700    </t>
3701    <t>
3702      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/191"/>:
3703      "Location header ABNF should use 'URI'"
3704    </t>
3705    <t>
3706      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/192"/>:
3707      "fragments in Location vs status 303"
3708    </t>
3709    <t>
3710      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/198"/>:
3711      "move IANA registrations for optional status codes"
3712    </t>
3713  </list>
3714</t>
3715<t>
3716  Partly resolved issues:
3717  <list style="symbols"> 
3718    <t>
3719      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/171"/>:
3720      "Are OPTIONS and TRACE safe?"
3721    </t>
3722  </list>
3723</t>
3724</section>
3725
3726<section title="Since draft-ietf-httpbis-p2-semantics-08" anchor="changes.since.08">
3727<t>
3728  Closed issues:
3729  <list style="symbols"> 
3730    <t>
3731      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/10"/>:
3732      "Safe Methods vs Redirection" (we missed the introduction to the 3xx
3733      status codes when fixing this previously)
3734    </t>
3735  </list>
3736</t>
3737</section>
3738
3739<section title="Since draft-ietf-httpbis-p2-semantics-09" anchor="changes.since.09">
3740<t>
3741  Closed issues:
3742  <list style="symbols"> 
3743    <t>
3744      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/43"/>:
3745      "Fragment combination / precedence during redirects"
3746    </t>
3747  </list>
3748</t>
3749<t>
3750  Partly resolved issues:
3751  <list style="symbols"> 
3752    <t>
3753      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/185"/>:
3754      "Location header payload handling"
3755    </t>
3756    <t>
3757      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/196"/>:
3758      "Term for the requested resource's URI"
3759    </t>
3760  </list>
3761</t>
3762</section>
3763
3764<section title="Since draft-ietf-httpbis-p2-semantics-10" anchor="changes.since.10">
3765<t>
3766  Closed issues:
3767  <list style="symbols"> 
3768    <t>
3769      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/69"/>:
3770      "Clarify 'Requested Variant'"
3771    </t>
3772    <t>
3773      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/109"/>:
3774      "Clarify entity / representation / variant terminology"
3775    </t>
3776    <t>
3777      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/139"/>:
3778      "Methods and Caching"
3779    </t>
3780    <t>
3781      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/190"/>:
3782      "OPTIONS vs Max-Forwards"
3783    </t>
3784    <t>
3785      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/199"/>:
3786      "Status codes and caching"
3787    </t>
3788    <t>
3789      <eref target="http://tools.ietf.org/wg/httpbis/trac/ticket/220"/>:
3790      "consider removing the 'changes from 2068' sections"
3791    </t>
3792  </list>
3793</t>
3794</section>
3795
3796<section title="Since draft-ietf-httpbis-p2-semantics-11" anchor="changes.since.11">
3797<t>
3798  None yet.
3799</t>
3800</section>
3801
3802</section>
3803
3804</back>
3805</rfc>
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